FR3114359A1 - Method for determining the operating point of a compressor - Google Patents

Abstract

Method for determining the operating point of a compressor Method for determining in real time the operating point of a compressor (10) comprising an annular casing (30) having a longitudinal axis and surrounding several compression stages, each of these stages comprising a movable impeller (32, 34) driven in rotation and a straightener provided with fixed vanes (36, 38) each having a leading edge and a trailing edge, process consisting of printing in additive manufacturing on at least one fixed vane of each of these straighteners at least one total pressure or static pressure or total temperature measurement sensor (42A, 42B, 42C; 44A, 44B) and to determine from the measurements delivered by these measurement sensors printed in additive manufacturing the operating point of the compressor. Figure for abstract: Fig. 2.

Description

Method for determining the operating point of a compressor

The present invention relates to the field of compressors for aeronautical turbomachines, whether they are single body, double body or triple body, whether they are high pressure (HP), low pressure (LP) or intermediate (IP) compressors ( Intermediate Pressure). It relates more particularly to a method and a compressor provided with sensors allowing the determination of the operating point of this compressor.

One of the aspects of the certification of an aeronautical engine is its transient behavior, that is to say during acceleration or deceleration. The certification authorities therefore specify minimum acceleration or deceleration times that the motors must respect. In addition, aircraft manufacturers also specify acceleration and deceleration times, which must also be respected. These requirements are moreover often more restrictive than those required by the certification (shorter times, or additional operating points).

These transients must be made within the operating limits of the engine, that is to say within what are called its operability limits which must be ensured throughout the declared flight envelope of the aircraft. This is particularly the case for compressors whose pumping ( stall or surge in English) constitutes a limit corresponding to an aerodynamic stall of the blades followed by a periodic inversion of the flow in the stream.

The operation of a compressor can be visualized by plotting its operating point in its scope (compressor compression ratio vs reduced inlet flow). The set of operating points of a compressor under given conditions is called an operating line, and is obtained for example by varying a control parameter of the turbomachine such as for example (non-exhaustive list): its rotational speed or the inlet/outlet temperature ratio. It is also possible to draw a line of surge, stall, flutter or instability, which corresponds to the limit not to be exceeded so as not to cause surge, stall, flutter or any other aerodynamic instability. For simplicity, this boundary line will be referred to as the "pumping line" throughout the rest of the patent.

A transient is a temporary state between two stabilized points. The stabilized start and finish points are by definition located on the stabilized operating line. Since the aerodynamic, thermal and mechanical effects acting on the turbomachine are dictated by different physical laws during a transient, the transient operating line does not follow the stabilized operating line.

Thus, for a high pressure (HP) compressor, the transient operating line in acceleration will be above the stabilized line. For a low pressure (LP) compressor, the transient operating line will be above the stabilized line rather during the deceleration phases, and partially during the acceleration phases, this behavior greatly depending on the turbomachine architecture considered. For three-spool compressors, the intermediate compressor IP may also be above its transient stabilized line, depending on the architecture considered.

To ensure the operability of a compressor, i.e. to ensure never to reach the surge line in its field, even under critical operating conditions, we reserve design of the turbomachine a sufficient margin between the operating line and the surge line, called surge margin, calculated using the method called “margin stack-up” which consists of summing (directly or quadratically) the risks associated with phenomena causing the position of the operating line or the pumping line to vary.

However, this margin reservation has a strong impact on the operation of the motor because, outside of these critical conditions, it results in slower acceleration or deceleration times. It also has the consequence of unnecessarily penalizing the performance of the engine by degrading the yields of the components so as to ensure the required pumping margin, whereas if we could afford to design the compressor with less margin, we could have a line of higher functioning and therefore better yields and thus better performance.

Moreover, there is a particular difficulty in piloting the transients in an optimal way, because one badly controls the residual margin in transient, that is to say the position of the line of transient operation in the field compared to the line of pumping.

The main purpose of the present invention is therefore to overcome these drawbacks by proposing a method making it possible to optimize the turbomachine from the point of view of performance (yields and therefore specific consumption) such as transients (acceleration and deceleration times).

This object is achieved by a method for determining in real time the operating point of an axial compressor comprising an annular casing having a longitudinal axis and surrounding several compression stages, each of these stages comprising a wheel with movable blades driven in rotation and a stator provided with stationary vanes each having a leading edge and a trailing edge, method consisting in printing in additive manufacturing on at least one fixed vane of each of said stator (preferably on said trailing edge or said attack or both) at least one sensor for measuring total pressure or static pressure or total temperature and to determine from the measurements delivered by these printed measurement sensors the operating point of the compressor.

Through this detailed knowledge of the operating point of each compression stage in real time, it becomes possible to size the compressors as close as possible to their maximum efficiency point and therefore to gain in overall performance. Similarly, it becomes possible to set up fine-tuned regulation laws to better control the transients, and to gain acceleration or deceleration time without risk to the turbomachine.

Advantageously, at least one sensor for additional total pressure or static pressure or total temperature measurement is printed by additive manufacturing on said annular casing immediately downstream of each of said rectifiers.

The invention also relates to a compressor comprising an annular casing having a longitudinal axis and surrounding several compression stages each comprising a wheel with movable blades driven in rotation and a stator provided with stationary vanes each having a leading edge and a leading edge. leak, characterized in that, to allow the operating point of this compressor to be determined, at least one stationary vane of each of said rectifiers comprises at least one sensor for measuring total pressure or static pressure or total temperature printed in additive manufacturing and a processing unit is configured to determine the operating point of the compressor from the measurements delivered by these printed measurement sensors.

In a configuration where the first compression stage is also preceded by an inlet stator fitted with fixed blades each having a leading edge and a trailing edge, said inlet stator also comprises at least one measurement of total pressure or static pressure or total temperature printed in additive manufacturing.

Advantageously, said trailing edge or said leading edge of at least one fixed blade of each of said rectifiers comprises at least one sensor for measuring total pressure or static pressure or total temperature printed in additive manufacturing and at least one sensor additional measurement of total pressure or static pressure or total temperature is printed in additive manufacturing on said annular casing immediately upstream of each of said rectifiers.

Preferably, said trailing edge or said leading edge of said at least one stationary vane of each of said rectifiers comprises several measurement sensors printed in additive manufacturing distributed radially with respect to said longitudinal axis.

Advantageously, each of said rectifiers comprises several measurement sensors printed in additive manufacturing distributed circumferentially around said longitudinal axis, typically at the level of one out of two fixed blades.

Advantageously, said at least one sensor for measuring total pressure or static pressure or total temperature printed in additive manufacturing is a sensor printed with metallic ink and the compressor is one of the following compressors: low-pressure compressor, high-pressure compressor, pressure, intermediate compressor.

The invention also relates to a turbomachine comprising a compressor as mentioned above.

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an example of embodiment devoid of any limiting character and on which:

there schematically illustrates in axial half-section a turbomachine to which the method of the invention is applied,

there shows an example of an axial compressor comprising a set of measurement sensors for implementing the method of the invention,

there is an end view of the compressor from the mounting the circumferential arrangement of the measurement sensors.

There shows an axial half-sectional view of a turbomachine 10 with longitudinal axis 12, in particular a dual-spool turbomachine, to which the method for determining in real time the operating point of a compressor according to the 'invention. Of course, the invention is not limited to this type of double-spool dual-flow turbomachine and it could for example apply to a single spool, a triple spool, a ducted fan turbojet engine with a very high bypass rate, a turboprop (with unducted propeller), or an open rotor type architecture.

Conventionally such a turbomachine comprises a primary stream 14 traversed by a hot flow that surrounds a secondary stream 16 traversed by a cold flow and it comprises from upstream to downstream with respect to the direction of the exhaust gases: a fan 18, a low pressure compressor 20, a high pressure compressor 22, an annular combustion chamber 24, a set of high and low pressure turbines 26 and an exhaust nozzle 28. In the example illustrated, each of the axial compressors is provided, in a annular casing, impellers with moving blades and rectifiers with fixed blades arranged alternately in a succession of adjacent compression stages.

The operating point of a compressor in its field is defined by the ratio of total pressure (total pressures upstream and downstream)/reduced flow rate. The reduced flow is defined by the relation and can be obtained by a flow measurement (the same for all compressor stages), a total upstream temperature measurement and a total upstream pressure measurement.

However, the flow measurement being difficult to obtain accurately, especially given the withdrawals and reintroductions existing at each stage of the compressor, the reduced flow can be obtained as a function of the section A (known because it is measurable) and the Mach ( which is linked to the ratio of the total and static pressures Pt/Ps and to the known constant g): WR = A.g(Pt/Ps), and, in this case, we can therefore content ourselves with a measurement of total pressure and d a static pressure measurement.

In practice, the operating point is most often defined by the ratio of total pressure/reduced speed, the reduced speed being then defined by the relationship which only requires an XN speed measurement (the same for all compressor stages) and a total temperature measurement upstream.

In accordance with the invention and as shown in the , it is proposed to print in additive manufacturing on at least the fixed vanes of the rectifiers of each of the compression stages of the compressor, sensors for measuring at least one physical parameter such as the total pressure, the static pressure or the temperature total.

Thus, with enough measurements, one can obtain the operating point of each stage of an axial compressor (pressure ratio/reduced rpm of each stage), instead of the operating point of the overall compressor (total pressure ratio/rpm reduced). This makes it possible to focus on the stage of the compressor closest to surge, rather than considering the compressor as a whole and it then becomes possible to control the operating point of the compressor according to the most critical compression stage. This is also valid for a centrifugal compressor carrying an annular casing having a longitudinal axis and surrounding an impeller driven in rotation.

It is possible, for example, to compare the pressure/reduced speed position with a target curve, and the desired change in speed/pressure is then determined to be placed on the target curve. The information is transmitted to a computer to allow the fuel flow / position of the variabilities to be adjusted.

More specifically, an annular compressor casing 30 having the longitudinal axis 12 as its axis of symmetry surrounds several compression stages (two in the example shown) each comprising a wheel 32, 34 with movable blades driven in rotation about this longitudinal axis. and a stator 36, 38 provided with a plurality of stationary vanes each having a leading edge 36a, 38a and a trailing edge 36f, 38f. The first compression stage may be preceded by an inlet stator 40 also provided with a plurality of stationary vanes each having a leading edge 40a and a trailing edge 40f.

To enable real-time determination of the compressor's operating point, each of the compression stages and, if present, the input rectifier, include, additively printed on the trailing edge 36f, 38f, 40f d at least one stationary vane of each of the rectifiers 36, 38, 40, at least one measurement sensor 42A, 44A, 46A of a physical parameter (pressure or temperature for example). Alternatively or cumulatively, at least one measurement sensor 48, 50, 52 can also be printed in additive manufacturing on the annular casing 30 immediately downstream of each of the rectifiers or upstream of each of the moving blades.

To cover the radial pressure and/or temperature dispersions in the air flow path 14, the trailing edge of the fixed stator vane preferably comprises several sensors 42A, 42B, 42C; 44A, 44B; 46A, 46B, 46C distributed radially with respect to the longitudinal axis 12 (typically between 1 and 10 preferably between 2 and 3) and printed in additive manufacturing.

Similarly, to cover pressure or temperature dispersions around the airflow path, and as shown in the , the measurement sensors of each of the rectifiers 36, 38, 40 are advantageously distributed circumferentially around the longitudinal axis 12, typically at the level of one out of two fixed blades, or less, without this distribution being limiting. And more particularly, to cover the pressure or temperature dispersions on the wall of the annular casing 30, the measurement sensors 48, 50, 52 printed in additive manufacturing immediately downstream of each of the rectifiers can also be distributed circumferentially on the annular casing.

To have an even more precise determination of the operating point of the compressor (for example to better know the heat transfers), it is possible to also equip the leading edges 36a, 38a, 40a with at least one fixed blade of each rectifiers 36, 38, 40 measuring sensors 54A, 56A, 58A of a physical parameter printed in additive manufacturing which may or may not be the same as that measured on the trailing edge of the blade. Similarly, at least one measurement sensor 60, 62, 64 can also be printed in additive manufacturing on the annular casing 30 immediately upstream of each of the rectifiers.

Of course, as for the sensors printed on the trailing edges of the fixed vanes of the rectifiers and those printed immediately downstream of these rectifiers, these measurement sensors printed on the leading edges or immediately upstream of these rectifiers can be distributed at both radially and circumferentially to cover all pressure or temperature dispersions at any point in the airflow path.

All of the measurements delivered by these sensors are fed back (only four links are shown by way of illustration) to a conversion module 66 whose function is to shape the signals received to allow them to be processed by a control unit of the turbomachine, for example the FADEC 68 of the engine, which can from these measurements (and if necessary the knowledge of A and g) determine in real time the operating point of the compressor.

The measurements made using these sensors also make it possible to determine the pumping margin, for example:

Delta Stall Margin (SM) = Margin at constant flow with operating line (or low line such as a surge line observed during testing) as a reference.

SM = (Pi 3 – Pi 1)/ Pi 1, with Pi 1 the pressure at stage 1.

Delta Pressure Ratio (dPRS) = Margin at constant flow with surge line (or high line) as reference.

dPRS = (Pi 3 – Pi 1) / Pi 3.

In addition, the isentropic efficiencies of compressors can be directly estimated from the total pressures and temperatures, and even from each stage:

Or even the polytropic yields, from the following relationship:

With the invention, it is therefore possible to reduce the need for a surge margin and therefore design the compressors so as to be on maximum yields (in particular by optimizing the yield of each stage), unlike the prior art where the surge margin forced to position the operating line lower in the field (farther from the pumping line) and therefore with lower yields.

In addition, the exact knowledge of the pressures and temperatures at the level of each compression stage makes it possible to ensure precise monitoring of the HP compressor field in Pi vs WR and no longer only an estimate, when this is provided in C/P vs NR, as it is known.

From the measurements of total temperatures and pressures, it is also possible to control the idle speeds to the exact need for minimum pressure (you can even enslave a setpoint on this measurement by the regulation) rather than relying on the construction of the minimum pressure idle stop based on a pre-calibrated model. We therefore regulate on a measure rather than on a model.

Claims (13)

Method for determining in real time the operating point of a compressor (10) comprising an annular casing (30) having a longitudinal axis (12) and surrounding several compression stages, each of these stages comprising a wheel with moving blades (32 , 34) driven in rotation and a stator provided with stationary vanes (36, 38) each having a leading edge and a trailing edge, method consisting in printing in additive manufacturing on at least one stationary vane of each of said stator at least one total pressure or static pressure or total temperature measurement sensor (42A, 42B, 42C; 44A, 44B) and to determine from the measurements delivered by these measurement sensors printed in additive manufacturing the operating point of the compressor . A method according to claim 1, wherein at least one additional total pressure or static pressure or total temperature sensor is additively printed on said annular casing immediately downstream of each of said rectifiers. A method according to claim 1 or claim 2, wherein said at least one measurement sensor is printed on said trailing edge (36f, 38f) or said leading edge (36a, 38a). Compressor (10) comprising an annular casing (30) having a longitudinal axis (12) and surrounding several compression stages each comprising a wheel with movable blades (32, 34) driven in rotation and a rectifier fitted with fixed vanes (36, 38) each having a leading edge (36a, 38a) and a trailing edge (36f, 38f), characterized in that, to allow determination of the operating point of the compressor, at least one fixed vane of each of said rectifiers comprises at least one sensor for measuring total pressure or static pressure or total temperature (42A, 42B, 42C; 44A, 44B) printed in additive manufacturing and a processing unit (66, 68) is configured to determine the point of operation of the compressor from the measurements delivered by these measurement sensors printed in additive manufacturing. Compressor according to Claim 4, characterized in that it further comprises at least one sensor for additional measurement of total pressure or of static pressure or of total temperature (48, 50, 52) printed in additive manufacturing on said annular casing immediately in downstream of each of said rectifiers. A compressor according to claim 4 or claim 5, wherein the first compression stage is further preceded by an inlet stator (40) provided with stationary vanes each having a leading edge (40a) and a leading edge. leakage (40f), characterized in that said input rectifier comprises at least one sensor for measuring total pressure or static pressure or total temperature (46A, 46B, 46C) printed in additive manufacturing. Compressor according to Claim 4 or Claim 6, characterized in that the said trailing edge or the said leading edge of at least one fixed vane of each of the said rectifiers comprises at least one sensor for measuring total pressure or static pressure or of total temperature (54A, 56A, 58A) printed in additive manufacturing. Compressor according to claim 7, characterized in that it further comprises at least one sensor for additional measurement of total pressure or static pressure or total temperature (60, 62, 64) printed in additive manufacturing on said annular casing immediately in upstream of each of said rectifiers. Compressor according to any one of Claims 4 to 8, characterized in that the said trailing edge or the said leading edge of the said at least one fixed vane of each of the said rectifiers comprises several measurement sensors printed in additive manufacturing (44A, 44B ) distributed radially relative to said longitudinal axis. Compressor according to any one of Claims 4 to 9, characterized in that each of the said rectifiers comprises several measuring sensors printed in additive manufacturing (50) distributed circumferentially around the said longitudinal axis, typically at the level of one out of two fixed blades. Compressor according to any one of Claims 4 to 10, characterized in that the said at least one sensor for measuring total pressure or static pressure or total temperature printed in additive manufacturing is a sensor printed with metallic ink. Compressor according to any one of Claims 4 to 11, characterized in that it consists of one of the following compressors: low-pressure compressor, high-pressure compressor, intermediate compressor. Turbomachine comprising a compressor according to any one of claims 4 to 12.