Nicolas Poujol
email: nicolas.poujol@ec-lyon.fr

Isabelle Trébinjac

Pierre Duquesne

EFFECTS OF INLET GUIDE VANES ON THE PERFORMANCE AND STABILITY OF AN AERONAUTICAL CENTRIFUGAL COMPRESSOR

Keywords: centrifugal compressor, inlet guide vanes, rotating instabilities, surge

A research centrifugal compressor stage designed and built by Safran Helicopter Engines is tested at 3 IGV (Inlet Guide Vanes) stagger angles. The compressor stage includes 4 blade rows: axial inlet guide vanes, a backswept splittered impeller, a splittered vaned radial diffuser and axial outlet guide vanes. The methodology for calculating the performance is detailed, including the consideration of humidity in order to minimize errors related in particular to operating atmospheric conditions.

The shift of the surge line towards lower mass flow rate as the IGV stagger angle increases highly depends on the rotation speed.

The surge line shift is very small at low rotation speeds whereas it significantly increases at high rotation speeds. A first-order stability analysis of the impeller and diffuser sub-components shows that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle.

At low rotation speeds below a given mass flow rate, rotating instabilities at the impeller inlet are detected at zero IGV stagger

angle. Their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet flow angle. Therefore, the onset of the rotating instabilities is delayed towards lower mass flow rates.

At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases. As a result, the flow is highly alternate over two adjacent channels of the radial diffuser beyond the surge line at IGV stagger angle of 0°.

INTRODUCTION

Environmental issues and the market environment encourage the engine manufacturers to improve the versatility of helicopter turboshafts. Therefore, the operating range of compressors should be extended while maintaining a high level of efficiency. There are two ways to extend the operating range of compressors:

• Reduce the surge margin by understanding better the local instabilities that cause deep surge. However, some complex instabilities such as spikes are still poorly understood [START_REF] Day | Stall, surge, and 75 years of research[END_REF] thus this method might not work in all cases for coming years. It should also be noted that the surge margin would reach a minimal value due to production tolerance and ageing of engines [START_REF] Young | Stall warning by blade pressure signature analysis[END_REF],

• Push towards lower mass flow rates the onset of deep surge and local instabilities. This goal might be achieved by inserting technology effects such as casing treatment, variable Inlet Guide Vanes (IGV) and boundary layer suction [START_REF] Schwerdt | Active flow control in an axial compressor by zero-net-mass-flux actuation[END_REF][START_REF] Van Den Braembussche | Design and Analysis of Centrifugal Compressors[END_REF]. The main difficulty of this method is to maintain the high level of efficiency at the design point while pushing towards lower mass flow rates the onset of deep surge.

TURBO-21-1015

The second method with the use of IGV for a centrifugal compressor is studied in the present work. Indeed, Whitfield et al. [START_REF] Whitfield | The performance of a centrifugal compressor with high inlet prewhirl[END_REF] have shown that the positive (in the direction of rotation) inlet pre-swirl pushed the onset of local instabilities, recirculation and deep surge towards lower mass flow rates. An inlet pre-swirl can be achieved in helicopter engines with IGV which have been previously used in numerous centrifugal compressor applications: Auxiliary Power Unit (APU) [START_REF] Rodgers | Centrifugal compressor inlet guide vanes for increased surge margin[END_REF], terrestrial industrial compressor [START_REF] Simon | Improvements in performance characteristics of single-stage and multistage centrifugal compressors by simultaneous adjustments of inlet guide vanes and diffuser vanes[END_REF] or turbocharger [START_REF] Ishino | Effects of variable inlet guide vanes on small centrifugal compressor performance[END_REF].

The IGV can be set at different stagger angles to modify the incidence at impeller inlet. Tian et al. [START_REF] Tian | Influence of adjustable inlet guide vanes on the performance characteristics of a shrouded centrifugal compressor[END_REF] noticed that the pre-swirl angle was lower than the IGV stagger angle. This lag effect has been attributed to the large IGV hub and the flow separation. Positive inlet pre-swirl induced by the IGV affect nevertheless the range of high efficiency and the stability of the compressor. The experimental and numerical investigations of Mohseni et al. [START_REF] Mohseni | Novel IGV designs for centrifugal compressors and their interaction with the impeller[END_REF] point to an extension of the range of high efficiency for IGV with s-cambered profiles and positive pre-swirl for stagger angles up to +75°. Experimental work of Rodgers [START_REF] Rodgers | Centrifugal compressor inlet guide vanes for increased surge margin[END_REF] at different stagger angles indicates that the onset of the deep surge is pushed towards lower mass flow rates at high rotation speeds with a positive pre-swirl even if the radial diffuser is stalled. The use of IGV for a turbocharger has been studied by Uchida et al. [START_REF] Uchida | Development of wide flow range compressor with variable inlet guide vane[END_REF]. The IGV stagger angles has been set up to +80° and the surge line has been shifted towards lower mass flow rates up to 15%. Ishino et al. [START_REF] Ishino | Effects of variable inlet guide vanes on small centrifugal compressor performance[END_REF] observed that the deviation caused by the IGV reduces the recirculation occurring between the suction side of the inducer and the shroud.

Most of the works cited above study the effect of the IGV stagger angle at only one rotation speed. The present work aims at investigating the effect of the IGV stagger angle over the complete performance map. Furthermore, the effect of IGV on the development of instabilities is rarely investigated. In particular, none work on the impact of the IGV stagger angle on the onset of rotating instabilities in centrifugal compressors has been published to the authors' knowledge. Therefore, the present work also focuses on the impact of the IGV stagger angle on the onset of rotating instabilities.

First, the test case, the experimental setup and the performance calculation methodology are described. The performance maps of the compressor stage for three IGV stagger angles are given and discussed. Then, the impact of the IGV stagger angle on the onset of rotating instabilities is studied. Finally, the evolution of the flow topology in the radial diffuser according to the IGV stagger angle is analyzed.

TEST CASE

The test case is a research centrifugal compressor stage designed and manufactured by Safran Helicopter Engines. The compressor stage includes four blade rows: axial inlet guide vanes (IGV), a backswept splittered impeller (IMP.), a splittered vaned radial diffuser (RD) and axial outlet guide vanes (OGV). A meridional scheme of the compressor is provided in Fig. 1.

FIGURE 1: MERIDIONAL VIEW OF THE COMPRESSOR

TURBO-21-1015

The overall stage total to static pressure ratio is around 4. The Mach number based on the peripheral velocity at the exit radius of the impeller is around 1.2.

EXPERIMENTAL SETUP AND PERFORMANCE CALCULATION

The centrifugal compressor stage is mounted on the 1MW test rig of Ecole Centrale de Lyon and is considerably instrumented.

More than a hundred steady pressure measurements and almost 20 thermocouples are used for the monitoring and the performance measurements. The mass flow is measured with a diaphragm flowmeter which is located at the test rig inlet.

The distribution of the steady pressure sensors in two channels of the radial diffuser is given in Fig. 2. Indeed, a particular flow topology spread on two channels of the radial diffuser has been previously observed numerically [START_REF] Benichou | Numerical analysis of an alternate stall in a radial vaned diffuser[END_REF] and experimentally [START_REF] Moënne-Loccoz | Detection and analysis of an alternate flow pattern in a radial vaned diffuser[END_REF] at an IGV stagger angle of 0°. The impact of the IGV stagger angle on this alternate flow topology is studied in the last part of the paper. The steady pressure sensors are located at the shroud or/and the hub. Ten unsteady pressure sensors are circumferentially distributed at the shroud at the impeller inlet (1 mm upstream the impeller leading edge), the distribution is provided in Fig. 3. Moreover, 5 unsteady pressure sensors are distributed along the external meridional path from the impeller leading edge to the impeller trailing edge. There are also 36 unsteady pressure sensors in the radial diffuser whose the location is not given because they are not used in the following analysis.

TURBO-21-1015 The rotation speed of the compressor is determined during the measurements by the standard rotation speed targeted and the atmospheric conditions of the day including the relative humidity (as explained later).

𝛺 =

√𝛾𝑟𝑇𝑡,0

√ 𝛾 𝑟𝑒𝑓 𝑟 𝑟𝑒𝑓 𝑇 𝑟𝑒𝑓 𝛺 𝑠𝑡𝑑 (1)
The performance values of the compressor stage are calculated with the Eq. 2, Eq.3 and Eq. 4.

𝑚̇𝑠 𝑡𝑑 = √ 𝑟𝛾 𝑟𝑒𝑓 𝑇 𝑡,0 √ 𝑟 𝑟𝑒𝑓 𝛾𝑇 𝑟𝑒𝑓 𝑃 𝑟𝑒𝑓 𝑃 𝑡,0 𝑚̇ (2)
The outlet guide vanes are not taken into account for the performance estimation of the compressor stage: the performance values of the compressor are calculated between the planes 3 and 0 in Fig. 1.

TURBO-21-1015 𝜋 𝐶 𝑡-𝑠 = 𝑃 𝑠,3 𝑃 𝑡,0 (3)
𝜂 𝐶 = 𝑇 𝑡,0 (𝜋 𝐶 𝑡-𝑠 𝛾-1 𝛾 -1) 𝑇 𝑡,3 -𝑇 𝑡,0 (4)
There are several steady pressure and temperature sensors distributed all around the circumference at each reference plane in order to reduce measurement errors: the values are averaged at each reference plane. The performance of the components is calculated with the same methodology.

The uncertainties on the performance values are calculated with propagation formulas and given at the design operating point in Tab. 2. The uncertainties on performance values at the design point are low. It should be noted that for lower mass flow rates (especially at low rotation speeds near surge), the uncertainty on mass flow rate can reach up to 0.4% for example. However, this measurement accuracy is more than sufficient for quantifying the impact of the stagger angle of the IGV on the performance values of the compressor stage.

The specific heat ratio γ and the specific gas constant r, appearing in Eq. 1, Eq. 2 and Eq.4, depend on the humidity rate of the day.

Therefore, the humidity rate might be considered in order to minimize errors related in particular to operating atmospheric conditions.

A humidity sensor is positioned in the settling chamber where the total temperature and total pressure are also measured. The empirical relation found by Glück [14] is used to calculate the saturation vapor pressure with the total temperature at the inlet of the compressor.

Then, the water vapor concentration in the flow is straightforward calculated and the values of the specific heat ratio γ and specific gas constant r are deduced.

These two specific values (γ and r) of the flow are used at two times (as shown in Fig. 4):

• During measurements for determining the rotation speed in order to be consistent with the standard rotation speed,

• After measurements, for the performance calculation.

6

TURBO-21-1015 3. It should be noted that these errors depend on the atmospheric conditions of the day (Φ=55% for these measurements). The error on the standard mass flow rate is negligible but the errors on the rotation speed and on the stage isentropic efficiency are significant. Indeed, the error on the isentropic efficiency is about 5 times higher than the measurement uncertainty. It highlights that the humidity rate has to be measured and taken into account a priori (during measurements to maintain the correct standard rotation speed) and a posteriori (for the performance calculation).

PERFORMANCE MAP AND VARIATION OF THE CHOKED MASS FLOW RATE

Previous work on the compressor at an IGV stagger angle of 0° has been carried out by Moënne-Loccoz et al. [START_REF] Moënne-Loccoz | Detection and analysis of an alternate flow pattern in a radial vaned diffuser[END_REF][START_REF] Moënne-Loccoz | An experimental description of the flow in a centrifugal compressor from alternate stall to surge[END_REF]. Rotating instabilities at the impeller inlet have been observed, the impact of the IGV stagger angle on the development of these rotating instabilities is discussed in the last part.

The performance map of the compressor stage has been measured at 7 rotation speeds from choke to surge for 3 IGV stagger angles: 0°, 20° and 40° (positive pre-swirl). It can be noted that the IGV clearances increase at both ends of the vane as the IGV stagger angle increases. From 11 to 21 stabilized operating points have been captured for each operating speed and for each stagger angle.

Therefore, the performance map is well discretized. Rotation speeds can be divided into two groups: low rotation speeds (L1 to L3) and TURBO-21-1015 high rotation speeds (H1 to H4). Therefore only a portion of the performance map with two rotation speeds (each representative of one group) is given in Fig. 5 for confidentiality reasons. The measurement uncertainties are lower than the marker size, therefore non visible on Fig. 5. The surge line is plotted for each stagger angle in thick lines on Fig. 5 a.

FIGURE 5: PORTION OF THE PERFORMANCE MAP AT 3 STAGGER ANGLES φ

As the stagger angle increases (for positive pre-swirl) the curves are shifted towards lower mass flow rates and slightly lower pressure ratios. However, the curves shift highly depends on the rotation speed, for example:

• At the low rotation speed L2, the stagger angle has a small impact on the pressure ratio curve.

• At the high rotation speed H2, the increase of the stagger angle shifts considerably the pressure ratio curve.

At low rotation speeds, the compressor stage reaches the same pressure ratio as the stagger angle increases contrary to the high rotation speeds especially at the stagger angle of 40°.

The stage isentropic efficiency is normalized by the maximum efficiency for the rotation speed considered at stagger angle of 0°.

The stage isentropic efficiency is considerably increased at low rotation speeds as the stagger angle increases (see Fig.

Fig. 6 shows the results for the 7 rotation speeds explored, the y-axis being ∆𝑚̇𝑠 𝑡𝑑 𝑐ℎ𝑜𝑘𝑒 (𝜑 𝑏 𝑉𝑆 𝜑 𝑎 ) and the x-axis being 𝑚̇𝑠 𝑡𝑑,𝑎 𝑐ℎ𝑜𝑘𝑒 .

The rotation speeds H3 and H4 have not been explored at the stagger angle of 40° which explains that the range in mass flow rate of the two curves is different.

FIGURE 6: DIFFERENCE IN CHOKED MASS FLOW DUE TO A STAGGER ANGLE INCREASE

The difference of choked mass flow rates is higher between 40° and 20° than 20° and 0° for all rotation speeds (the red curve is always above the blue one). The effect of the stagger angle on the choked mass flow is indeed not linear.

In addition, the curves diverge : the difference ∆𝑚̇𝑠 𝑡𝑑 𝑐ℎ𝑜𝑘𝑒 (𝜑 𝑏 𝑣𝑠 𝜑 𝑎 ) increases as the choked mass flow increases, i.e. as the rotation speed increases. Therefore, these curves illustrate the horizontal shift of the choked mass flow rate as a function of the stagger angle in Fig. 5.

The second limit of the operating range is the surge mass flow rate which depends on the incidence on the impeller amongst other parameters. The velocity triangles at the impeller inlet are determined, assuming that the flow at the impeller inlet is aligned with the IGV trailing edge. Such an assumption has been evaluated from numerical simulations RANS run with the elsA software from ONERA.

TURBO-21-1015

The simulations are run on the whole stage (including the OGV row) with mixing planes between the stationary and rotating components.

As these simulations are only used to assess the validity of the previous assumption, further details on the parameters are not given.

However, it should be noted that the parameters recommended by the ONERA are used.

The absolute flow angle at the IGV outlet (before the mixing plane between the IGV row and the impeller) is extracted for a numerical operating point near the experimental operating point corresponding to the onset of rotating instabilities. The results are that (i) the value of the average of the absolute flow angle does not depend on the rotation speed for a given stagger angle, (ii) the difference between the IGV stagger angle and the absolute flow angle is similar between all stagger angles and very low (less than 4° at the worst case). Therefore, the differences are sufficiently small to validate the assumption. Furthermore, this assumption was done in order to establish a method only using experimental data.

Two velocity triangles at the impeller inlet at a same rotation speed and same mass flow rate are given in Fig. 7: without pre-swirl in black, with a pre-swirl of +40° in red.

FIGURE 7: VELOCITY TRIANGLES AT IMPELLER INLET

The incidence at impeller inlet at a same mass flow rate is thus reduced by increasing the IGV stagger angle especially near deep surge. Therefore, increasing the IGV stagger angle might extend the operating range towards lower mass flow rates.

ANALYSIS OF THE STABILITY OF COMPONENTS

A first-order stability analysis of the components (based on Dean's work [START_REF] Dean | The fluid dynamic design of advanced centrifugal compressors[END_REF]) is performed. A compression system is defined stable if the slope of the total-to-static pressure ratio with the mass flow rate is negative:

𝜕𝜋 𝐶 𝑡-𝑠 𝜕𝑚̇𝑠 𝑡𝑑 ≤ 0 (6)
One can split the pressure ratio of the compressor in the product of the pressure ratios of each component. By applying a logarithmic derivative, the stability parameter of each component appears:

The stability parameter is computed with an off-centered derivative to the right. The stability parameter uncertainties are calculated using propagation formulas and plotted with error bars. For the last stable operating point, the uncertainties cannot be computed, the value plotted is the same as the penultimate stable operating point. The stability parameters of the whole compressor stage, the impeller 10 TURBO-21-1015 and the radial diffuser are computed. The IGV stability parameter is not studied because it is always stable due to pressure losses. Indeed, pressure losses being proportional to the square of the mass flow rate, the total to total pressure ratio of the IGV decreases as the mass flow rate increases.

The stability parameters for a stagger angle of 0° for all rotation speeds explored are given in Fig. 8. The error bars are smaller than the marker size for all presented operating points.

FIGURE 8: STABILITY PARAMETERS AT THE STAGGER ANGLE 0°

It is recalled that the stability parameter is only a first-order condition for stability of a compression system. However, it is clear that the radial diffuser is unstable whereas the impeller is stable at low rotation speeds. In contrast, at high rotation speeds, the radial diffuser is stable whereas the impeller is unstable.

The stability parameters for a stagger angle of 20° are plotted in Fig. 9.

TURBO-21-1015 The stability parameters for a stagger angle of 40° are given in Fig. 10.

TURBO-21-1015 The trends at the low rotation speeds remain unchanged: the impeller is stable whereas the radial diffuser is unstable near deep surge. However, none of the components is unstable at high rotation speeds according to this first-order stability analysis. More accurate investigations (especially from unsteady pressure signals) will thus be carried out in order to understand the surge triggering at rotation speeds H1 and H2.

An overall similarity of the component stability at the 3 IGV stagger angles is observed. At low rotation speeds, the impeller is stable whereas the radial diffuser is unstable near surge. At high rotation speeds, it is the opposite configuration: the impeller is unstable and the radial diffuser is stable.

DELAY OF THE ONSET OF ROTATING INSTABILITIES AT LOW ROTATION SPEEDS

Rotating disturbances have been observed at the low rotation speed L2 on a large mass flow range at the stagger angle 0° during previous work [START_REF] Moënne-Loccoz | An experimental description of the flow in a centrifugal compressor from alternate stall to surge[END_REF]. These rotating disturbances are in fact rotating instabilities according to the description of rotating instabilities proposed by Day [START_REF] Day | Stall, surge, and 75 years of research[END_REF]. These rotating instabilities are spatially consistent only during a few rotations of the impeller and their intensity and frequency are continuously varying, thus they differ from rotating stall.

TURBO-21-1015

The experimental signature of rotating instabilities at the 3 low rotation speeds is described below. The pressure fluctuations at 5

sensors circumferentially distributed at the shroud at the impeller inlet are plotted in Fig. 11 over one revolution at a stable operating point at low rotation speed L2. The phase average on 100 rotations is substracted in order to remove the synchronous phenomena such as the blade passing.

FIGURE 11: PRESSURE FLUCTUATIONS AT THE IMPELLER LEADING EDGE AT THE SHROUD AT ROTATION SPEED L2 AT THE STAGGER ANGLE 0°

It should be noted that even if only 5 sensors distributed on a small sector have been used for plotting Fig. 11 for clarity, the rotating instabilities are also observed when more sensors on a sector of about 60° are considered.

The pressure fluctuations are significant: they reach up to 40 kPa. Some rotating instabilities can be identified: two are distinguished by black lines joining fluctuation peaks. Their rotating speed is between 55% and 60% of the rotor speed on this operating point.

The power spectral density of the pressure signal recorded by one sensor at the impeller leading edge at the shroud is also plotted in Fig. 12 for the same stable operating point. The power spectral density is also given for the choked operating point of the same rotation speed at the same stagger angle. At the operating point with rotating instabilities, the power is distributed on a bump which is centered on the rotating speed of the rotating instabilities. At the choked operating point, the power is only distributed in several peaks which are spaced of the rotation frequency. This characteristic of rotating instabilities is similar to the observations of Young et al. [START_REF] Young | Stall warning by blade pressure signature analysis[END_REF].

TURBO-21-1015 This methodology is used at all stable operating points (previously presented). It is concluded that rotating instabilities also occur at low rotation speeds L1, L2 and L3 at the 3 stagger angles. The pressure fluctuations are the same order of magnitude at all low rotation speeds and at all stagger angles. In addition, the bump in the power spectral density has also the same shape between all operating points with rotating instabilities.

A critical value of the relative flow angle at the tip of the leading edge of the impeller β1,critical tip is calculated by averaging the relative flow angle β1 tip at which the rotating instabilities appear at each characteristic curve.

The operating points where rotating instabilities occur are identified by stars on Fig. 13. The x-axis is the standard mass flow rate and the y-axis is the ratio between the relative flow angle at the tip of the leading edge of the impeller β1 tip and its critical value β1,critical tip .

The change of the relative flow angle is consequent from choke to surge at a given rotation speed.

It should be noted that the relative flow angle is calculated by assuming that the meridional velocity is constant along the span.

This assumption is obviously inaccurate but the bias introduced is equal between all rotation speeds and all stagger angles. The radial profile of the meridional velocity at the impeller inlet is extracted for a numerical operating point near the experimental operating point corresponding to the onset of rotating instabilities and plotted in Fig. 14 at IGV stagger angle of 0°. The radial profile of the meridional velocity is almost similar between the low rotation speeds. Therefore, if a mistake is done on the value of the critical flow angle, it does not depend on the rotation speed or stagger angle.

TURBO-21-1015 rotation speed and as previously shown in Fig. 10, the radial diffuser is very unstable. Therefore, the flow is very unstable and it is not surprising that the correlation does not fit.

Rotating instabilities are not observed at high rotation speeds whatever the stagger angle. Indeed, the compressor stage surges before the relative flow angle at the impeller inlet reaches this critical value at high rotation speeds.

INCREASE OF THE ALTERNATE RATE AT HIGH ROTATION SPEEDS

Previous numerical and experimental studies [START_REF] Benichou | Numerical analysis of an alternate stall in a radial vaned diffuser[END_REF], [START_REF] Moënne-Loccoz | Detection and analysis of an alternate flow pattern in a radial vaned diffuser[END_REF] at an IGV stagger angle of 0° have shown that a steady alternate flow pattern settles in the radial diffuser over two channels at low mass flow rate on some rotation speeds. This steady alternate flow topology is also observed in RANS simulations at different IGV stagger angles (previously introduced). An example of static pressure maps obtained by RANS simulations is given for two mass flow rates in Fig. 15 a):

• Left column corresponds to the peak efficiency operating point. This flow topology is called "Periodic" because the flow is the same in each channel.

• Right column corresponds to an operating point at lower mass flow rate than the peak efficiency. This flow topology is called "Alternate" because it is very different over two adjacent channels: the left channel (channel 1) is stalled whereas the right channel (channel 2) is free. This flow pattern is steady in time and space.

It should be noted that these numerical flow fields are only given for an illustrative purpose and not for a comparison between experimental and numerical results.

Well discretized pressure maps are not available experimentally. An indicator called the "Alternate rate" (A) using the steady pressure profiles measured at the radial diffuser inlet is developed in order to estimate how much the topology is alternate. The diffuser inlet is chosen because the sensors are the most numerous there (see Fig. 2) and the flow difference between two adjacent channels is the most pronounced. A similar indicator is presented in [START_REF] Moënne-Loccoz | Detection and analysis of an alternate flow pattern in a radial vaned diffuser[END_REF] but the methodology of calculation is considerably simplified in the present work. The alternate rate A compares the difference between the circumferential static pressure profiles at the diffuser inlet between the channel 1 and channel 2:

FIGURE 2 :

 2 FIGURE 2: DISTRIBUTION OF THE STEADY PRESSURE SENSORS IN TWO CHANNELS OF THE RADIAL DIFFUSER Furthermore, 54 unsteady pressure sensors (models XTE-190M and XTEH-7L-190M manufactured by Kulite Semiconductor Product Inc.) are distributed over the entire stage in order to capture the time-dependent fluctuations of the flow and to investigate instabilities. To capture phenomena at frequencies around 100kHz, the protection grids were removed in order to maximize the natural frequency of the probes. The average value of the uncertainties of the fluctuations is less than 0.7% of the peak-to-peak pressure fluctuation of the signal.

FIGURE 3 :

 3 FIGURE 3: DISTRIBUTION OF THE UNSTEADY PRESSURE SENSORS AT THE IMPELLER INLET

FIGURE 4 :

 4 FIGURE 4: METHODOLOGY OF INCLUSION OF HUMIDITY RATE FOR MEASUREMENTS

  5 b). In addition, the mass flow rate of the peak efficiency operating point is almost unaltered by the stagger angle at low rotation speeds. In contrast, the TURBO-21-1015 stage isentropic efficiency is slightly modified by the stagger angle at high rotation speeds but the mass flow rate of the peak efficiency operating point is greatly affected (see Fig. 5 c). Therefore, the mass flow range of high efficiency is considerably extended by adjusting the IGV stagger angle. At a given rotation speed, the operating range is limited on the one hand by the choked mass flow and on the other hand by the surge mass flow. The impact of the stagger angle on the choked mass flow and the shift of the surge line towards lower mass flow rates are now being analyzed. The choked mass flow rate is considerably reduced as the stagger angle increases. The change in choked mass flow rate at a given rotation speed is quantified (with φa and φb two different stagger angles) by: ∆𝑚̇𝑠 𝑡𝑑 𝑐ℎ𝑜𝑘𝑒 (𝜑 𝑏 𝑉𝑆 𝜑 𝑎 ) = |𝑚̇𝑠 𝑡𝑑,𝑏 𝑐ℎ𝑜𝑘𝑒 -𝑚̇𝑠 𝑡𝑑,𝑎 𝑐ℎ𝑜𝑘𝑒 |

FIGURE 9 :

 9 FIGURE 9: STABILITY PARAMETERS AT THE STAGGER ANGLE 20°

FIGURE 10 :

 10 FIGURE 10: STABILITY PARAMETERS AT THE STAGGER ANGLE 40°

FIGURE 12 :

 12 FIGURE 12: POWER SPECTRAL DENSITY OF PRESSURE FLUCTUATIONS AT THE IMPELLER LEADING EDGE AT THE SHROUD AT THE SAME OPERATING POINT

  𝑐ℎ𝑎𝑛,1+2 ̅̅̅̅̅̅̅̅̅̅̅̅̅̅ ∫ |𝑃 𝑐ℎ𝑎𝑛.1 (𝜃) -𝑃 𝑐ℎ𝑎𝑛,2 (𝜃)|𝑑𝜃 𝜃 𝐷𝑅 0[START_REF] Ishino | Effects of variable inlet guide vanes on small centrifugal compressor performance[END_REF]

FIGURE 16 :

 16 FIGURE 16: EVOLUTION OF ALTERNATE RATE FROM PEAK EFFICIENCY OPERATING POINT TO LAST STABLE OPERATING POINT AT ROTATION SPEED H2 FOR 3 IGV STAGGER ANGLES This difference of alternate rate at the last stable operating point between the IGV stagger angle is investigated. The alternate rate A against the difference between the absolute flow angle at the radial diffuser inlet and the camber angle ϴC is plotted in Fig. 17. The

  . The absolute flow angle is calculated by using Euler's equation and the mass flow rate conservation. Aside from the two last operating points near surge, a satisfactory correlation is observed between the alternate rate and the absolute flow angle. Therefore, the difference of alternate rate at last stable operating point between stagger angles is explained by a difference of absolute flow angle at the diffuser inlet.TURBO-21-1015The authors would like to thank also Safran Helicopter Engines which supported this study. This project has received funding from the Clean Sky 2 Joint Undertaking under the European Union's Horizon 2020 research and innovation program under grant agreement N°820099.

TABLE 1 :

 1 STEADY MEASUREMENT UNCERTAINTIES AT THE DESIGN POINT

	Measured value	Uncertainty
	Ω	±0.06 %
	P	±0.01 %
	T	±0.20 %

TABLE 2 :

 2 MEASUREMENT UNCERTAINTIES OF PERFORMANCE VALUES AT THE DESIGN POINT

	Performance value	Uncertainty
	ṁ	±0.11 %
	πC t-s	±0.13 %
	ηC	±0.21 %

TABLE 3 :

 3 PERFORMANCE ERRORS WITHOUT THE INCLUSION OF HUMIDITY RATE

	Characteristic value	Additional error
	Ω	0.7%
	ṁstd	0.01%
	ηC	1.11%

TURBO-21-1015

The alternate rate is 0.01 in the periodic case, it is not zero because there are differences of discretization between the two channels.

In the alternate case, the alternate rate is 0.15. Therefore, the indicator A discriminates well the two flow topologies because there is a ratio of 15 between the two cases.

The values of A are then calculated from the experimental pressure data at rotation speed H2 in order to study the impact of the IGV stagger angle on the alternate rate. The alternate rate A is plotted against the standard mass flow rate from the peak efficiency operating point to the last stable operating point in Fig. 16. The alternate rate increases towards surge for the three stagger angles.

Moreover the alternate rate near surge is higher at stagger angles of 40° and 20° than at stagger angle of 0°.

ACKNOWLEDGEMENTS

The authors would like to thank Pierre Laucher, Sebastien Goguey, Gilbert Halter and Benoit Paoletti for manufacturing the test bench and supporting the measurements.

The presented research was supported through Clean Sky 2 Joint Undertaking (JU), project FLORA under grant agreement N•820099. The JU receives support from the European Union's Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union. This publication reflects only the author's view and the JU is not responsible for any use that may be made of the information it contains.

https://www.researchgate.net/project/FLORA-FLOw-control-in-RAdial-compressor Pierre.duquesne@ec-lyon.fr

TURBO-21-1015 A strong correlation between the onset of rotating instabilities and the relative flow angle at the tip of the leading edge of the impeller β1 tip is observed. The correlation is only proven false near deep surge at the rotation speed L3 at a stagger angle of 40° (two operating points with RI before the critical relative flow angle on Fig. 13). This discrepancy might be due to mild surge observed at this TURBO-21-1015 The alternate rate A is actually calculated from discrete values with a trapezoids integration. An example from numerical results The unsteady alternate rate is also calculated with the same methodology but with the unsteady pressure sensors. The standard deviation of the temporal fluctuations of the alternate rate remains very low for all operating points at rotation speed H2. Therefore, the alternate flow pattern is fully steady and is not coupled with a mode.

Finally, the steady alternate rate is calculated for all high rotation speeds and it is observed that there is a large zone of high alternate rate (A > 0.03) ranging from rotation speed L3 to rotation speed H4 beyond the surge line at IGV stagger angle of 0° in A first-order stability analysis of the impeller and diffuser sub-components showed that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle.

Rotating instabilities at the impeller inlet are observed at low rotation speeds at each IGV stagger angle. It is shown that their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet relative flow angle. As a result, the onset of the rotating instabilities is delayed towards lower mass flow rates.

At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases.

Therefore, the flow is highly alternate over two adjacent channels of the radial diffuser (one channel stalled and one channel free) beyond the surge line at IGV stagger angle of 0°. Indeed, there is a critical absolute flow angle below which the flow is highly alternate over two channels in the diffuser.


Dorothée Legrand

The violence of the ethical encounter: listening to the suffering subject as a speaking body

Keywords:

How does the clinical encounter work? To tackle this question, the present study centers on the paradigmatic clinical encounter, namely, psychoanalysis, paradigmatic in that it is structured by the encounter itself. Our question thus becomes: how does the clinical encounter work, when its only modality is speech? By reading Jacques Lacan and Emmanuel Levinas together, we better identify how speech sets up as subjects those who address one another and how this subjectivation touches the suffering body specifically. In this framework, a definition of the encounter is put to work: The encounter of a sufferer and a listener, that is, the clinical encounter, is the opening of an inter-human space beyond suffering. This conception of the encounter permits a specifying of the violence it avoids-respecting the transcendence of the other irreducibly other-but also the violence that it mobilizes-through a presumption of subjectivity imposed upon the other, by which the subjectivation at work in the encounter is, by definition, a subjection to the other. This outlines, then, an ethics of the clinical encounter: a relationship of man to man commanded by one sensing body to another, i.e. a minimal and therefore radical ethics that is structured as a sensible ethics between speaking bodies.

1 Questions How might one understand that ''there is no speech without a response, even if speech meets only with silence, provided it has an auditor?''1 How does speech-the demands that it conveys, the desire that it carries, the listening that it summons, the response for which it calls-how does speech work at the scene of an encounter where one's singularity radically escapes the alterity of the other? In the encounter with a clinician, how can one give voice to one's suffering, how does one address it to the other, as an inexhaustible demand of survival? In the encounter with a patient, how does one listen, and in this way respond to the unspeakable suffering of the other? What is the body, if it bears the saying and the listening addressed to one another? How might one understand that ''matter is the very locus of the for-theother?''2 context-one understands better, for example, the specificity of Freud's unconscious, in comparing it with that of Merleau-Ponty8-an articulation instead proposes to work outside of borders, to shift a thought to where it is not thought (yet), to impregnate, indeed to contaminate a thought with that which is not thought (yet). In particular, here we will play on the articulation between philosophy and psychoanalysis in order to elaborate upon the notion of the clinical encounter.

Metamorphic address

How does the clinical encounter work? In order to clearly grasp this question, here, we will tackle the paradigmatic clinical encounter, namely, psychoanalysis: Paradigmatic in that its only modality of work is the encounter; no psychological tests, no neurophysiological investigations, no medical prescriptions are involved; that which goes on there is: An encounter. What is it that goes on, then, within such an encounter? What does pass between one and the other that constitutes an encounter, and that makes an encounter work, on one and on the other? To target psychoanalytic practice already makes an initial response appear that allows us to qualify this question. Indeed, psychoanalysis is an encounter, its practice is a technique and this technique is speech. Patient and clinician encounter each other and do nothing other than encounter each other-they do not test one another, do not measure one another, do not advise one another, do not touch one another-and that which passes between the one and the other, is first and always speech.9 But then, how does the clinical encounter work, when its only modality is speech? In order to better seize what is at play here, it is important to discern, with Jacques Lacan, ''two planes […] within which the exchange of human speech is played out,''10 two dimensions that both participate fully in the speaking. Speech is, in one part, a link between subjects, in the other part, a link between subject and object. In Lacan's terms, it is necessary to distinguish, in one part ''the plane of the communique´'' which ''involves a tendency to reach an agreement on the object […] the object considered as external to the action of speech, which speech expresses,'' and in the other part, the plane of communicating subjects, that is, the plane where ''speech links the subjects together into [a] pact.''11 Whatever the agreement of the subjects on the object, whatever the object about which they speak, all speech is first of all and always a pact between subjects. Now, speech, precisely this dimension of speech that ties the subjects together, is not sterile. On the contrary, by establishing a link between subjects, speech ''transforms them.''12 Specifically the speech which 8 de Saint Aubert (2017, in press), Mooney (2017, in press), Phillips (2017, in press), Legrand (2017a, in press). 9 Notice that speech remains the ineliminable ingredient of all clinical practice, including in technoscientific contexts. 10 Lacan (1988, p. 108). 11 Ibid. 12 Ibid.

The violence of the ethical encounter: listening to the… 45 passes between subjects ''sets them up as human subjects communicating.''13 It is exactly this operation that must be better understood here, as it occurs in the clinical encounter: How does speech set up as subjects those who address one another? How does this subjectivation touch the suffering body14?

4 Suffering body, speaking body

Suffering is that without which there would be no clinical encounter. The suffering of the other is always necessarily ''useless,'' ''for nothing,'' ''senseless;'' it is ''unjustifiable. ''15 The suffering of the other ''is unforgivable to me.''16 It is exactly as such that the suffering of the other ''solicits me and calls me.''17 The suffering of the other summons me; it calls me to remedy the irremediable, and puts me in a position to respond to the call of the other. The grimaces of pain, the tears, the cries, the atrocious howls of a person pushed into insurmountable horror, the face marked with suffering, all of that is perhaps, in itself, foreign to language. Nevertheless, all of that can perhaps also be heard as a call addressed to the other, a call to respond to her subjecting sufferance. Such a call is ''the original call for aid, for curative help, help from the other me whose alterity, whose exteriority promises salvation.''18Here, ''a beyond appears in the form of the interhuman,''19 a beyond suffering, whereas suffering itself is ''intrinsically senseless,''20 a self-enclosed ''dead end,'' the impossibility of ''being protected in oneself from oneself.''21 To be clear: It is exteriority, alterity, that opens the suffering to a beyond suffering. We can therefore propose a definition: The encounter, and in particular, the encounter of a suffering with a listening subject, i.e. the clinical encounter, is the opening of an inter-human space where a beyond suffering is sketched out. To open this space, to undertake an encounter, is not to take on the suffering of the other in its place; it is to place oneself in a position to receive the manifestation of her suffering, as a manifestation of her subjectivity, and so to put her in the position of a subject; it is to put oneself in the position of a listening subject, and so to put the other in the position of a speaking subject; to encounter, then, is to receive the suffering body and to establish it as a speaking body; it is to give an address to sufferance.22 13 Ibid.

14 Legrand (2015d).

15 Levinas (1998, p. 93 Levinas (1979, p. 238).

22 Ingerslev and Legrand (2017, in press).

D. Legrand

My suffering subjects me to myself; in suffering I am taken, wrapped up in myself, enclosed, but the fact that you listen to me expressing my suffering-that is to say, the act by which you respond not only to the suffering, but to me, a subject expressing this suffering-this gesture opens the suffering; it transforms a space of suffering, in which I am enclosed within myself, into a space of speech where I am in a position to address my suffering to you, thus calling for your response.

To listen, to respond, is to receive the suffering body as if it were a call from one subject to another. It is about receiving that which, without this space giving it an address, could have been a suffering that ''had no subject to receive it and had therefore the weight of a fatality.''23 To listen to suffering in this way, is to give or to give back a subject to the suffering. In an analytic situation, this is to ''involve the subject in his message.''24 This is not to engage a subject so that she reveals her secrets, first in spite of herself perhaps, so that they will then be brought to consciousness. Instead, the subject engages herself as an interlocutor, which is to say that she participates in a situation where she engages herself as a speaking subject by engaging another subject as a listening/responding subject. It is in this way that listening, like speaking, is capable of a ''transformation of the subject to whom it is addressed by means of the link it establishes with the speaker.''25 To consider psychoanalysis as implicating first and always such a ''subject to subject relationship,''26 such a ''dialogue,'' such a ''communication,'' such an ''intersubjectivity,'' such an ''interlocution''-this is what we call here an encounter-to characterize psychoanalysis as a ''dialectical experience''27 in this sense28 comes down to recognizing that, if one uses speech there, it is precisely because the effect of this speech is to set up a subject as such. It is not about an ''I speak, therefore I am'' that would emerge out of a language where the speaking subject would be able to function in a self-sufficient manner. And the answer given to the speech of the subject does not act only ''as approval or rejection of what he is saying;''29 rather, to respond to him is ''to recognize or abolish him as a subject,''30 either by depriving him of any place in the interlocution, or on the contrary in recognizing a subjective position that he will be able to assume and take up in speaking: In this manner, ''you listen, therefore I am.'' In this way, that which engages the speech of the subject engages ''not only her comprehension of things, but her very position as a 23 Levinas (1979, p. 53). Here, Levinas speaks particularly of the work of memory ''Memory recaptures and reverses and suspends what is already accomplished in birth-in nature.

[…] By memory […] I assume today what in the absolute past had no subject to receive it and had therefore the weight of a fatality. By memory I assume and put back into question. Memory realizes impossibility: memory after the event, assumes the passivity of the past and masters it'' (Ibid.). We reroute the remarks in the setting of the present reflection; we are leaning on the fact that, in analysis at least, the work of the encounter and the work of memory are indissociable from one another.

24 Lacan (2006d, p. 241). 25 Ibid. (p. 245).

26 Lacan (2006b, p. 176). 27 Ibid. (p. 177).

28 Legrand (2015a). 29 Lacan (Lacan 2006d, p. 247). 30 Ibid. (p. 248).

The violence of the ethical encounter: listening to the… 47 subject.''31 Such is the ''magical power''32 of the encounter, the transformative power of speech, its capacity to bind ''the subjects together into this pact which transforms them, and sets them up as human subjects communicating.''33

An encounter with alterity

But how to encounter the other? This question, always concrete and urgent, is made to appear sharply in the clinical encounter because, if, in her suffering, the other is closed in on herself, if she radically escapes the grasp of comprehension, as well as prehension, how could one encounter her? How could one speak and listen? How could we position each other together in the space of an encounter? In other words, how is it possible that an encounter could come to pass between two subjects who are estranged from one another? Or again, how does an encounter come to pass between two singular subjects, each one irreducible to the other? For Ludwig Binswanger, psychiatry is practiced ''always and everywhere from man to man:''34 It is about being-with-others and being-for-others. Contemporary work inspired by phenomenology and phenomenological psychiatry equally defends such an approach. For Michael Kleinberg-Levin35 who bases his philosophical position on that of Merleau-Ponty, it is necessary-and for him this is a moral duty-to put an end to the idea of an omnipotent ecological subject, and introduce on the contrary, relations of symmetry, transpositions, reciprocity, and reversibility between self and other. For Thomas Fuchs,36 intersubjective understanding is a process of interaction, of mutual coordination and intercorporation which permits the generation of common significations. But how is being-with-others possible, in this manner, when the other is a ''stranger,'' that is to say, when her suffering is incommensurable with mine, when I fail to understand her language, when my own mental and bodily states do not open and resonate in empathy with hers? According to Maurice Merleau-Ponty, if I can encounter the other, it is because we are not two subjects installed in two incomparable worlds, but two openings onto the same world.37 However, the hallucinating man is excluded from this common world. For Merleau-Ponty, indeed, hallucination is ''the overwhelming proximity of the object''38 because it is exclusively to the hallucinating man's own body that her objects are tied, without a possible distance, without a possible sharing with others.

31 Lacan (Lacan 2006b, p. 178).

32 Freud (2014, p. 3).

33 Lacan (1988, p. 108). 34 Quoted by Maldiney (2007, p. 64); all translations of this text by M. G. Butler. See also [START_REF] Binswanger | Being-in-the-world[END_REF].

35 [START_REF] Kleinberg-Levin | A responsive voice: Language without the modern subject[END_REF][START_REF] Kleinberg-Levin | Before the voice of reason: Echoes of responsibility in Merleau-Ponty's ecology and Levinas's ethics[END_REF]. 36 [START_REF] Fuchs | Enactive intersubjectivity: Participatory sense-making and mutual incorporation[END_REF], [START_REF] Fuchs | Embodied affectivity: On moving and being moved[END_REF].

37 [START_REF] Merleau-Ponty | The visible and the invisible (trans: Alphonso Lingis)[END_REF]. Here, Merleau-Ponty expresses this in ontological terms: We are ''two entries to the same being'' (Ibid., p. 82).

38 Merleau-Ponty (2012, p. 304). 48 D. Legrand In this sense, ''the hallucinatory phenomenon is not part of the world,''39 and in this way ''it is not accessible.''40 If it is true that the ''world'' is the common world where ''every consciousness that I might encounter''41 gesticulates, then, I could not encounter the hallucinating man, excluded from the ''world.'' However, Merleau-Ponty clarifies that madness is not an ''island of experience without any communication and from which one cannot escape.''42 Admittedly, ''the existence of the patient […] gradually exhausts itself in the solitary constitution of a fictional milieu;''43 admittedly, ''the hallucination does not take place in the stable and intersubjective world,''44 but a certain connection to the other remains possible, even if she hallucinates. This connection, for Merleau-Ponty, is conditional upon our communal points, by exclusion of our differences. A connection with the other is possible, even if she is mad, but only if she is not completely mad, only if for her, the entire world has not contracted into a hallucination. Following Merleau-Ponty then, I can only have access to the non-mad dimensions of the existence of the mad and an encounter with a patient is all about ''making explicit my experience and his experience, such as it is indicated in my own, or [about] making explicit his hallucinatory belief and my real belief, and [about] understanding them through each other.''45 In this way, even if the difference of the other, her singularity, her alterity is particularly ''resistant,'' we try to ''subdue'' her ''disquieting existence.''46 And yet, in the clinical encounter, it is impossible to subdue the otherness of the other: We are confronted by her alterity, inescapably. For Henri Maldiney, for example, in psychosis-and in melancholia in particular-the other is ''pure alterity.''47 In that case, ''there would be nobody with whom to communicate.''48

The difference, the alterity of the other imposes a limit on our empathic resonance. At most, one could observe a patient and understand her cognitively, because the other's madness is closed in on itself-impermeable to the alterity that I am for her-and therefore hermetically sealed off from the encounter. But if, even if-and it is not in any way established that such is the case, but let's allow this for a moment-even if no empathic resonance would be possible with a person enclosed in psychosis, who would be radically other, would one have to conclude that no encounter is possible? Is an encounter possible only with your own kind? Is it only possible to encounter a subject on the condition that one shares a common world with her, the world of sane consciousness In reality, are we not always confronted with the alterity of the other, whether or not she is psychotic, whether or not she is a stranger? The other, completely other, as other, always overcomes me. She is the singular subject who is never only that which I perceive her to be, never just what I understand her to be. How then is it possible to encounter the other, since she is other, and thus incessantly and irremediably overflows my efforts at comprehension and my talents of interpretation? Because it could suggest that an encounter with the other could be impossible, because it could imply that the encounter with the other could be possible only if the alterity were purged and the other were integrated as my semblance, because to pose this question already includes this violence, this question must be inverted. We are left to wonder then, how it would be possible to encounter the other, if she were not other?

Transcendence

The alterity of the other is not an obstacle to our encounter. On the contrary, it is that without which there would be no encounter. Emmanuel Levinas describes this alterity as it is implemented in speech and describes speech as an implementation of alterity. In Lacan's terms, as discussed above, one could say that Levinas tirelessly refuses the reduction of speech to ''the plane of the communique´,'' to ''a tendency to reach an agreement on the object.''49 Levinas incessantly bends our ear to hear speech as that which ''links the subjects together and sets them up as human subjects communicating.''50 In his own terms, Levinas tirelessly insists that Saying is irreducible to that which is Said: Saying is that by which speech opens a space of address, a space of call and response, a space of encounter. This space spreads below and beyond our understanding of what is said.

The incomprehensible nature of the presence of the Other […] is not to be described negatively. Better than comprehension, discourse relates with what remains essentially transcendent.

[…] we must attend to the formal work of language, which consists in presenting the transcendent.51

The formal work of language would then be to make present that which is outside of me, the alterity of the other, that which overflows me, that which exceeds my own comprehension, my own consciousness. If such is the case, it is because Language is a relation between separated terms. To the one the other can indeed present himself as a theme, but his presence is not reabsorbed in his status as a theme. The word that bears on the Other as a theme seems to contain the Other. But already it is said to the Other who, as interlocutor, has 49 Lacan (1988, p. 108). 50 Ibid. 51 Levinas (1979, p. 195)

Violence

Before saying any more, it is necessary to emphasize the violence inherent in the encounter. To listen to the one who addresses herself to you as if she were not addressing herself to you is to objectify her. It is to observe the words that she pronounces like natural signs that would be correlated with fixed physical or psychic objects, independent of her, of you, of the situation of interlocution. Such is the violence of objectification. But it is another violence, a violence intrinsic to the encounter, which is at stake here, and which rests upon a presumption of subjectivity, subjectivity assigned by the one who listens, to the one who speaks in spite of herself. Faced with the other, ''you have to answer for yourself, for your identity,''54 and Jacques Derrida calls on us not to forget that the injunction to present oneself ''could be an act of extreme violence.''55 This violence is mobilized by the very same act that gives space to the subjectivity of the other. To listen is an act whose violence is commensurate with the metamorphosis that it provokes, the violence of the metamorphosis of the suffering body into the speaking subject, listened to as such.

In the encounter, she who suffers and addresses her suffering to the other, she who is heard as the suffering subject, sees herself compelled to recognize the subjectivity of a suffering that she could prefer to see as other, exterior, objectifiable, a suffering that she would have to carry subjectively, a suffering for which she could prefer to disown responsibility.56 She who is listened to as a subject 52 Ibid. 53 Legrand (2017b, in press). 54 Derrida (1991, p. 131); for this text, translations by M. G. Butler. See also [START_REF] Derrida | Of Hospitality: Anne Dufourmantelle Invites Jacques Derrida to Respond, trans[END_REF]. 55 Ibid. (p. 131). 56 Legrand (2015c).

The violence of the ethical encounter: listening to the… 51 is put in a position to respond as a subject to this suffering which is tied to herself despite herself. She is thus confronted with the violence of a suffering of which she cannot rid herself like she could an encumbrance. More generally, in the encounter, she has to assume the subjectivity of that with which she does not identify, that which exceeds what she wants to be or how she wants to appear. From the moment she speaks, what she means to say can be invalidated by that which comes out of her own mouth, and this impromptu itself becomes the manifestation of a subjectivity despite itself. But, there is yet another violence. ''A subject is a hostage,'' says Levinas.57 We understand that she who listens is the hostage of she who speaks: Such is one of the forms of violence that dwells in listening, violence which subjects the listener to being the hostage of the speech that is addressed to him. The listener, listening in spite of herself, is here confronted with the ''impossibility of evading the assignation of the other without deficiency.''58 The subject cannot evade her condition as the hostage of the other without ''denying'' herself.59 If I evade myself, I exile myself from the relation to the other whereas it is precisely there that I am constituted as subjectivity, without possible substitution, as I-I whose unicity surges precisely from my ''assignation to answer without evasions''60 to the call that the other addresses to me. Furthermore-and without here introducing a symmetry between self and other, a symmetry which would completely contradict the Levinasian movement-if ''the subject is a hostage,''61 we must understand here as well that she who speaks is the hostage of she who listens. The act of listening is a call without possible evasion: It assigns the other to being the one who speaks and assigns her in this way to answering her own question: Who am I? Who am I for you? I am the one who speaks; I am the one who speaks to you. In this way, the subject who is listened to as subject is subjected not only to the violence of speaking and hearing herself speak, but also to the violence of listening. This act of listening is violent because it is in the same gesture that it establishes the speaking body as a subject and that it deposes the subject of her sovereignty. Listened to in this way, the subject is the one who ''is called on to be someone and cannot slip away from this call.''62 Such a subject is radically irreconcilable with the constitution of oneself, in oneself, by oneself. Rather, the subjectivation at work in the encounter is, by definition, a subjection to the other-as it is the listening of one that establishes the other as a speaking subject. Here, it is necessary to consider how, as soon as I listen, I extract speech from the other. It is necessary to consider how opening a space in order for the speech of the other to make itself be heard, is also inextricably linked to imposing an encounter on the other without possible refusal. In the encounter, the other imposes herself on me in spite of myself and deposes me therefore from the 57 Levinas (1981, p. 112) 8 Being subject for the other That which develops here between subjectivity and subjection, unicity and alterity, encounter and separation, this knot has the same structure as speech. Specifically, it is that ''language, prior to signifying something, signifies to someone.''63 Jacques Lacan reminds us of this, when reading the Odyssey: One day, Odysseus' companions […] were turned, because of their unfortunate tendencies, into swine.

[…] One is still obliged to think they nonetheless retain some links with the human world, since in the middle of the pigsty […] they communicate through their grunts, their different needs, hunger, thirst, their sensuality, indeed their group feeling. But that is not all. What can we say about these grunts? Aren't they also messages addressed to the other world? […] How do we recognize that a grunt which comes to us out of this silky mass filling the enclosed space of the pigsty is speech? […] The pig's grunt only becomes speech when someone raises the question as to what it is they want to make you believe. Speech is precisely only speech in as much as someone believes in it.

[…] Speech is essentially the means of gaining recognition.64 What is heard here is the alterity of the other, the other who is, for me, incomprehensible but audible, who I hear as a subject and therefore recognize as such. What is also heard is the alienation from the other, the other that I am, who listens such and such a manifestation as speech, and therefore establishes the speaking subject as such. What is heard is equally the structure of speech as a ''relationship between separate terms,''65 a structure such that one could never speak alone, because to speak is to address a call that cannot ''be held up in isolation.''66 In order for there to be a call there must be a caller and a called-or more precisely, when there is a call, it is the sign that there is a caller and a called, addressing one another. If the call is important here, it is not insofar as it would characterize language as a structure, but insofar as it structures speech as an act-not speech such as it is carried by a subject but speech such as it carries the encounter between more than one subject, between caller and called. The call is a call insofar as it is addressed; as such it cannot be the act of a solitary subject but always already includes the addressed as the one for whom the call is manifested. In this sense, the call is structured by its respondant.67

63 Lacan (2006a, p. 66). [START_REF] Legrand | [END_REF] Lacan (1988, pp. 239-240). 65 Levinas (1979, p. 195).

66 Lacan, 1998, p. 182; translation by M. G. Butler. 67 Ingerslev and Legrand (2017, in press).

The violence of the ethical encounter: listening to the… 53

To speak to you is to ask you to recognize that the sounds that come out of my mouth are not senseless grunts, but speech. Speaking to you, I ask you therefore to recognize me as the subject who speaks, and to recognize yourself as the subject that I address. All speech, therefore, is a demand, a demand to be heard as speech, and as such all speech is a demand addressed to the other. More precisely all speech is an ''intransitive'' demand which ''brings no object with it:''68 Speech is not necessarily a transitive demand as an ''asking for…,'' that is, asking for something more, or for something else, or asking to have this or that; rather, all speech is an intransitive demand, [as in the French] ''demande a`,'' a demand addressed to someone, for being recognized as a speaking subject, as an interlocutor, as a partner in an encounter. 9 A need for which words are not enough

The intransitive demand, contained in all speech, cannot be satisfied by giving something, as what is called for is someone. Nonetheless, this does not signify that one could satisfy the intransitive demand without giving something which could respond to the needs of the subject. Speech is never only the expression of a need to have more or something else. All speech always carries the desire for the other, the desire to be recognized by the other, for whom the subject calls.69 This distinctionbetween need and desire, between having an object and being a subject, between the transitive dimension of the demand for something and the intransitive demand for someone-this distinction is not purely conceptual. In fact, it is concretely clinical, because it imposes a certain position on the clinician. Indeed, if the clinical encounter is about not reducing the demand to the demand for something, in order to also listen to the demand as a call for someone, then a particular listening position is required. Listening, the clinician positions herself as someone to whom speech is addressed, and it is from this place that she can position the patient herself as someone who addresses herself to someone else, rather than remaining close in on herself, in the isolation of her sufferance. Listening in such a way, the clinician does not ignore the transitive demand. But even if she also gives the ''something'' that the subject demands, she does not give this exclusively, and does not aim to give everything that the subject demands to have-how could she?-because it would then suffocate, reduce the demand to silence, terminate the pact of speech that links the subjects together. Facing the suffering subject who calls for help, the clinician does not wear the insignia of omnipotence. She does not ''stuff him with the baby food [she] does have,''70 but rather puts herself in position to be the one who is lacking-the one who is structurally lacking that which could fill the demand that the subject addresses to her. It is in this way that the clinician can be the one who does not keep the demand of the patient quiet, but on the contrary, who holds onto the pact of speech that this demand allows to be established.

68 Lacan (Lacan 2006c, p. 515). 69 Lacan (2006c, p. 627). 70 Ibid. (p. 525).

D. Legrand

Insofar as she does not shut up this demand, it is the responsibility of the clinician to respond to it. This response is first and always a reception of speech as speech thereby setting up the groaning body as the speaking subject. But it is also necessary to insist on the fact that this response to the other ''has meaning only as 'taking care of the other's need'.''71 To encounter the other is to give him bread when he is subjected to a hunger that no speech could appease, as an empty stomach could not be filled with words. Levinas insists on this from the beginning to the end of his writing: ''Hunger is, in itself, need or privation par excellence, which constitutes the materiality or the great frankness of matter.''72 The hunger in question concerns, always and above all, the survival of the organic body, and ''keeps one from taking consolation from this privation in the image of a spiritually ordered world.''73

Here, ''at a very humble level, in the humility of hunger we can see taking shape a non-ontological transcendence that begins in human corporeality.''74 This transcendence is not that of the world of which I could make my food, that upon which I could bite and whose material I could assimilate into my own body; moreover, the prayer sharpened by the sharpness of hunger is not a question addressed ''in the direction of some world behind the world.''75 On the contrary, hunger is ''the establishing of [the] primacy of the ethical, that is, of the relationship of man to man:''76 ''The one listening to the other, the one stepping out of itself toward the other, is the response to the question and the pre-orational prayer of hunger. It is thus that, in hunger, at a very humble level, transcendence progressively appears.''77 It thus appears that the ''hunger that no music appeases''78 reverses the conception of intentional consciousness so dear to transcendental phenomenology. For Levinas, this analysis does not aim at ''making transcendence subjective:''79 It is not about reducing the transcendent to the subject; on the contrary, it is about ''being astonished by subjectivity,''80 astonished by the fact that it is always penetrated by transcendence.

And it is exactly here that the encounter plays out, at the most concrete levelbecause when Levinas speaks of hunger, his language is not metaphorical; his language is ethical and hyperbolic but not metaphorical. For Levinas, listening is the response to the question that is hunger. It is in order to give the bread that nourishes the other, that the encounter is necessary: It is necessary to have listened, it is necessary to have heard her call, the cry of her hunger. In order to feed her when she is hungry, in order not to force feed her when she is full, it is necessary to listen, to 71 Levinas (1981, p. 74); emphasis added. 72 Levinas (2000, p. 170) Levinas (1979, p. 79). 77 Levinas (2000, p. 171) listen to her calls, to listen to the gurgling of her stomach like a call for help, a demand. By the dovetailing of the transitive and intransitive dimensions of the demand, by the artificiality there would be in isolating a purely intransitive demand, by the danger there would be in hearing the demand only as a ''demand to,'' by the violence it would be to ignore the need for which the demand calls for help-what is implied is the articulation of body and speech. The idea that it is now necessary to analyze further is that it is the body by which is established the ''relationship of man to man''81-which is nothing other than the purest definition that Levinas gives to ethics. Sensible, corporeal, material, for such an ethics, fine words are not enough: It is vital.82 This is perhaps what one might better keep in view when considering the ''vital insufficiency''83 that inaugurates the life of an infant, and when giving all of its importance to the ''psychical fecundity''84 of such vulnerability. Throughout his teaching, Lacan takes up this ''paradoxical law''85 that Freud details in 1895 in his Project for a Scientific Psychology: ''At early stages, the human organism'' cannot survive without ''extraneous help, when the attention of an experienced person has been drawn to the child's condition by a discharge taking place along the path of internal change (e.g. by the child's screaming).''86 The child, being ''helpless,'' has alerted this ''extraneous helper'' by her cries, by her tears, by her behavior-in the terms we are privileging here: The child addresses her distress to the other as a demand for survival, putting the other in a position to respond to her. And because it makes necessary the articulation of vital needs in a demand addressed to an other, ''the original helplessness of human beings is thus the primal source of all moral motives.''87 With this first demand, the oral demand that is not, strictly speaking, the demand to eat but also the demand to be nourished-with the first moments of life, the living body localizes the subject, not in a world to which she would innately adhere, but in the space of the other. Indeed, for humans, the vital need is always already a demand, the demand to survive. Not purely a physiological need of the infant, the oldest need is always already articulated in the most simple demand: I am hungry.

What occurs here is a primordial structuration of the body insofar as its needs are addressed to the other. In this sense ''all the needs of speaking beings are contaminated by the fact of being involved in an other satisfaction […] the one that is based on language.''88 This articulation of the body in speech, inaugurated by prematurity, is never resolved by maturation. That which never ceases, therefore, is 81 Levinas (1979, p. 79).

82 Legrand (2017b, in press), Legrand (2015b).

83 Lacan (2006a, p. 72). 84 Ibid. 85 Ibid. 86 Freud (1954, p. 379). 87 Ibid.; emphasis added. 88 Lacan (1999, p. 51). 56 D. Legrand the vital necessity of a ''relationship of man to man,''89 i.e. the necessity of a bodytobody ethics, an ethics for which words are not enough.

An ethics of listening

What listening is mobilized in such an ethics? The encounter that is being thought of here is about listening, but it is not about hearing the other in the manner of a spectator who could listen as one observes a measurable object, that one could take in at a distance. Rather, if the listening is such that it establishes the listener as a speaking subject, it matters to be sensitive to the other, in the sense that to listen in this way is notably to mobilise the very sensitivity90 that animates the lived body, this sensitivity that I cannot choose, postpone, suspend-except by depriving my own body of it. What is being sketched out here is the idea according to which there is ethics, a relation of one man to the other, that is a sensible demand, a bodily necessity-and not a moral obligation.91 ''The Ego does not only become conscious of this necessity to respond as if it were a demand or a particular duty it must decide on;''92 on the contrary, the presence of the Other, i.e. the presence of her body, her sensitivity, her susceptibility to being hurt is a ''summons to respond:''93 The sensitivity of the other puts me in a position to respond, a position from which I cannot remove myself, just as I cannot avoid my own body. It is here that, with Levinas, in the humility of the sensible, one could see an ethics sketched out that begins with the subject's corporeity.

In spite of myself, my body is sense-able: Able to sense the other, in spite of me. ''Matter is the very locus of the for-the-other''94 and it is in exactly this sense that there is a sensible ethics. Were we permitted to paraphrase Jacques Derrida,95 we could summarize what is at stake here in one sentence: I have but one sensibility, and it is not mine. Neither interoception, nor introspection, at once for oneself and for the other, the sensible is ethical: A body-to-body relation of one to the other. Levinas writes a striking page in order to describe ''the common action of the sentient and the sensed which voluptuosity accomplishes,'' but for him, what is this ''community of sentient and sensed?''96 It is tied to the fact that The other is not only a sensed, but in the sensed is affirmed as sentient, as though one same sentiment were substantially common to me and to the other 89 Levinas (1979, p. 79). 90 Translator's note: I have rendered sensibilite´ and sensible interchangeably as sensitivity/sensibility and sensitive/sensible respectively, depending on context. 91 Legrand (2017b, in press). 92 Levinas (2005, p. 33). 93 Ibid. (p. 33). 94 Levinas (1981, p. 77).

95 [START_REF] Derrida | Monolingualism of the other, or, the prosthesis of origin[END_REF].

96 Levinas (1979, p. 265).

The violence of the ethical encounter: listening to the… 57 -and not in the way two observers have a common landscape or two thinkers a common idea. An identical objective content does not here mediate the community, nor is the community due to the analogy of feeling; it is due to the identity of feeling.97 This identity of sensing is not the identity of the sensed. It is not the identity of ''that which is sensed by me'' and ''that which is sensed by you.'' It is not an identity of content. It does not, therefore, tend towards the eventuality of an identification of the other as my semblance. This identity does not work by analogy or by comparison. It does not operate relatively on contingent qualities that determine the other taken as my theme, my object of observation, of description, of investigation. The identity of sensing is sensing as identity, it is my identity insofar as it is sensible, it is my sensitivity insofar as that participates in my identity, it is the singularization that operates on my body such that I can take on life. What's more, this sensible identity, that makes me be me, is very precisely that which makes me be-for-the-other. Because to be sensible is indissociably to be sensitive to the vital demands of one's own body, and to be sensitive to the vital demands to which the body of the other is subjected. The sensitivity of one (subjective genitive) is the sensitivity of the other (objective genitive). My sensitivity is sensitivity to your sensitivity, to your ''susceptibility to being hurt.''98 Such identity of sensing does not permit me to carry your suffering in my body, nor to recognize your suffering as comparable to mine, similar or different. The identity of sensing is to recognize your suffering as yours, incomparably yours, and to be unable to be unsensitive to it. It is my body that makes me hear the suffering of the other, and more precisely, it is my body insofar as it is sensitive that commands me to respond to the other whose sensibility is a suffering that calls me. No analogy here, no empathy; I am not like the other, I do not put myself in the other's position.

On the contrary, it is the suffering that my own body has known which makes my body be for the other: My suffering has been a cry addressed to the other, the helping other, and by ''transference''99 it makes me hear and respond to the cry that the other addresses to me. But if such is the case it is not because we could share one communal suffering. It is not because I would make mine a suffering of yours. If humans cannot not be for the other, it is not because the one and the other would be made of a common flesh that would make the bodies vibrate in unison. On the contrary, the space of an encounter with the other only opens if it is not determined by the weight of my suffering, only if I take up the disparity between my suffering and yours. In this way, even when Levinas describes an ''identity of feeling,'' he does not avoid reminding us of the unavoidable separation between oneself and the other: Being in contact with another ''is neither to invest the other and annul his alterity, nor to suppress myself in the other.''100 I am sensitively affected in my own body by 97 Levinas (1979, p. 265). 98 Levinas (1981, p. 51). 99 Levinas (2000 p. 171). 100 Levinas (1981, p. 86). 58 D. Legrand the body of the other, by her face, her suffering, but I am affected like this because she exceeds me: The sensible is the incarnation of the transcendence of the other.

To make apparent that which is building up here, I will employ an image. The encounter with the other is a walk towards the horizon. The horizon, in a concrete sense,101 is the place where sky and land meet and draw the line of their separation. It is this place beyond which I cannot see, from where I stand. The horizon is perceptible. It is present. But it exceeds this presence, and by its presence, it indicates an absence: A space infinitely inaccessible from here. The horizon shifts with each of my steps, in a manner such that its movement immutably structures my perception: The horizon is dynamically unsurpassable. The space that separates me from the horizon is a space of desire, desire that animates my steps and orients my walk, desire that I will never satisfy, space that I will never totally cross, since the horizon recedes at the same speed that I walk on. The horizon structures the field of my perception like a desirable line calling to be rejoined but that cannot be, because it exists only as distance, as separated.

Between the walker and the horizon, something happens that is just like the encounter between oneself and the other: That which animates the walk is the distance, the desire to cross it, and the impossibility of reducing it. That which animates the encounter is the separation from the other, the desire to approach her, and the impossibility of reaching her. To encounter the other is therefore always to go to encounter the other, incessantly to go there, without ever arriving. The approach towards the other, says Levinas, is a ''search: A march towards the invisible.''102

11 The separation of bodies

The psyche is ''my approaching of the other, the fact that the proximity of the same and the other is never close enough.''103 This proximity never close, such is the ethical inviolability of the other: An impossibility. It is impossible for me to encounter someone, if she is reduced to the object of my interest, of my care, of my understanding, to the object of my anger, of my cruelty, of my torture; to violate the alterity of the other and to reduce her to the same would be to not encounter her. This impossibility is a bodily demand that is imposed on me by my sensitivity that makes me sensible to the sensitivity of the other, and thus to that which exceeds me. Insofar as it is strictly impossible to reduce the sensitivity of the other to my own sensitivity, it is impossible that the other is reduced to an object placed in front of a subject who, herself, will remain unaffected. The objectification of the other would not only be the destruction of the other as an other, but the destruction of all possible 101 This description of the horizon is loosely inspired by Anthony Poiraudeau, a historian of art who works on the ''engineering of place'' and who discusses the position of George Didi-Huberman on this point in particular: The concept of the horizon. For Didi-Huberman, the horizon is a limit, that which is far off, transcendent, beyond oneself, and inaccessible. See: [START_REF] Poiraudeau | Erotique du Paysage, de l'image et de la marche[END_REF].

102 Levinas (1979, p. 258).

103 Levinas (1981, p. 137).

The violence of the ethical encounter: listening to the… 59 encounters-a destruction, therefore, of that part of my subjectivity, which surges from within my encounter with the other.

The ethical inviolability of the other therefore entails an impossibility: It is impossible for me to encounter someone if she is reduced to an object, and what's more, it is impossible for me to reduce the other (subject) to an object of my interest, of my care, of my comprehension, of my anger, of my cruelty, of my torture; I cannot not be exceeded by the other. I cannot not be exceeded. We must size up this demand: I cannot not be sensitive to the sensitivity of the other. More precisely, insofar as I have a sensitive body, it is imposed on me to be sensitive to the other, and therefore, to the encounter.

If it is true that by the formal structure of language, the encounter is a separation, we must consider how the gap between speaking subjects, an ethical gap, is a gap between speaking bodies. The body in the encounter is inviolable, in the sense that there could not be an encounter (in the ethical sense considered here) if the bodily limits of its participants were violated. In this way, it is by the body, as inviolable, that the encounter is anchored in the strict singularity of each interlocutors. Regardless of whether or not you understand the other who addresses herself to you, her body is and must remain other than yours. Yet, this otherness is not an obstacle for the encounter. On the contrary, otherness structures the encounter as a separation between inviolable subjects. If this gap between speaking subjects exists in the encounter, it is not only but always due to the body, by the fact that each subject is ''always inevitably confronted by the corporeal ordeal of its limits.''104 This ordeal is the impossible communion or total harmony with the other. It is what allows the clinician to work with ''that which she cannot be,''105 that which allows her to encounter the patient as the one she cannot be, as the one who is in a place where she cannot put herself, as the one who she cannot fulfill. It is the ordeal of the body as a stranger that constrains the clinician to staying ''just beside'' the patient:

The just position is to remain beside. The bodily ordeal of the limits between one and another, the separation of bodies is what assures the ethical inviolability of the other, that which allows a clinician to receive a patient as a singular subject hosted in her alterity. This reception is possible only if the act of listening is not that of a clinician ''who would be capable of hearing everything, bearing everything, and who would be able to give to the patient the exclusive and total love that she believes she demands.''106 Clinical listening is not an absolute listening, neutral, abstract, dis-embodied, theoretical, general, anonymous, and that ''would immediately be grotesque in its wanting to be heroic.''107 In contrast, it is a listening that is limited because it is singular, singularly embodied. Only under this condition, the one who speaks is not just anyone who speaks to walls. ''It is I-I and no one else''108 who presently encounters this other and no one else. ''It is I-I and no one else'' who is assigned 104 Fe´dida (2012, pp. 10-11) Levinas (1981, p. 126). 60 D. Legrand this position, ''an assignation that does not aim at any generality.''109 In the encounter, I am not ''a particular case of the universal, an ego belonging to the concept of ego, but as I said, in the first person, I, unique in my genus.''110 If-as it has been proposed above-the encounter establishes subjects as such, then there is no question of ''the ego, but of me. The subject which is not an ego, but which I am, cannot be generalized, is not a subject in general; we have moved from the ego to me who am me and no one else.''111 That I cannot not present myself in person to face the other, such is the motivation of the encounter of speaking bodies. The one who speaks to the other ''tolerates only a personal response, that is, an ethical act. ''112 This is what must be undertaken in order for there to be an encounter: Become a particular listener, while stripping off any act that is not rooted in listening to the word of the patient who addresses me. It is in and through accepting and acknowledging my position, and thereby positing my body in this place, that I am a singular subject, assuming the fact of being faced with another singular subject, who I recognize as such, by the sole fact of recognizing that she is irreducibly inaccessible, and that she addresses her speech singularly to me.

12 Excess

To encounter is to assume that, faced with the other who addresses me in speech, my listening is not anonymous, is not covered under a theoretical, theological, or technical cloth, that could be carried by another, by anyone. Without alibi, my listening is not substitutable. If a course in psychology, a seminar in philosophy, a line in the Bible, etc. predetermined the listening that I give in response to the speech that is addressed to me, then it would be difficult to encounter the other in the place of her very singularity. Yet, it is exactly this that is demanded: The recognition of her singularity. If my listening, my response therefore, is singular, it is insofar as it is not substitutable by another and as it is without any theological, theoretical, or technical alibi: Psychoanalysis ''would be another name for ''without alibi''''.113 Is it then necessary to cut oneself off from these ''alibis,'' to try to cut oneself off from references, to put them in parentheses, suspend them, submit them to an e´poche´, in the ambition to open a space of unconditioned and unconditional listening? Is it not also necessary, first and above all, to make a reality of these references, embody them, in order to give weight to one's listening and in this way to structure the space of the encounter, without predetermining it? To pose this question-even without answering it-allows us to clarify that the space of the encounter is open to ''what comes about, comes to pass, or as we say in French, ce qui arrive, the event of the other as arrivant (the one who or which arrives),'' the other as the one who ''exceeds and puts to rout'' the security that is installed ''when an already legitimated speech takes advantage of some convention.''114 The other arrives ''beyond all convention,'' beyond all theoretical, theological or technical requirements, ''beyond mastery, beyond ''I can,'' ''I may,'' beyond the economy of appropriation of a ''that is in my power,'' an ''it is possible for me,'' the ''this power belongs to me,'' the ''this power is conferred on me''''.115 Beyond all these reassuring positions, the event of the encounter is ''a hospitality of visitation and not of invitation, when what arrives from the other exceeds the rules of hospitality and remains unpredictable for the hosts.''116 To encounter, therefore, is to be exceeded by the other who arrives, to be visited by the stranger that was not invited, that could not have been anticipated, to be (placed) in position to host the other, the alterity of the other, her transcendence. The other comes, she enters into the space of the encounter, I host her there, without possible evasion, I cannot not host her there, because she arrives always already without any possibility for me to anticipate or reduce her otherness by imposing upon her conventional rules of hospitality. In this sense, to encounter the other is not to invite her ''to my home.'' Rather, she comes to a space opened between her and me.

The encounter goes on in between: Beside, just beside, always beside, the encounter is always wobbly and it is as such that it opens the space of suffering; already a transformation is at work, therefore, there where the suffering is not completely abandoned to a domain of cognitive understanding, a domain of explanation and justification, where suffering as such would be neglected. Without alibi, to encounter is to open an inter-human space where a beyond suffering could be sketched.

  The inviolability of the other is ethical: It is the impossibility that an encounter with the other could occur if the other is reduced to a theme, an object of interest, of investigation, of comprehension, of care, of love.53 The ethical inviolability of the other is an irreducible gap between her and my understanding of her. It is a gap between her and me, a space of encounter structured by separation, singularity, alterity.

	.
	50 D. Legrand
	quit the theme that encompasses him. [… In this way] in discourse the
	divergence that inevitably opens between the Other as my theme and the Other
	as my interlocutor, emancipated from the theme that seemed a moment to hold
	him, forthwith contests the meaning I ascribe to my interlocutor. The formal
	structure of language thereby announces the ethical inviolability of the
	Other.52

The ethical inviolability of the other is her transcendence, her irreducible alterity, which speech makes present. The ethical inviolability of the other is at work in the interlocution: It is the work of speech as the Saying of a subject that is addressed to a separated other.

  of my identity, and yet, it is exactly there, in this deposing, that subjectivity is bestowed upon my position, that unicity is conferred upon my identity-in spite of myself, I am unique.

	.
	58 Ibid.; translation modified; emphasis added.
	59 Ibid. (p. 122).
	60 Ibid. (p. 106).
	61 Ibid. (p. 112).
	62 Ibid. (p. 53).
	52 D. Legrand

sovereignty

Ibid. (p. 127).

Ibid. (p. 139).

(pp. 13-14).

Levinas (1979, p. 219).

Derrida and Kamuf (2002, p. 240).