FR3069020B1 - TURBOMACHINE COMPRESSOR WITH VARIABLE CALIBRATIONS - Google Patents

Abstract

The invention relates to a centrifugal or axial-centrifugal turbomachine compressor (14) comprising, from upstream to downstream, at least one inlet grille 32, a wheel (34) provided with at least pallets (36) configured for providing a radial flow of compressed air, at least one grid of a radial diffuser (39) and a grid (40) of an axial diffuser (41), characterized in that the inlet grid (32) is a variable-pitch input grid (p) or IGV and in that the mpoint a grid (38) of the radial diffuser (39) comprises a grid (38) variable pitch. The invention also relates to a law governing said shims (p, d) and a control method of a turbomachine (10) applying this law.

Description

The invention relates to a turbomachine compressor, and in particular to a centrifugal or axial-centrifugal compressor.

STATE OF THE PRIOR ART

In a known manner, a turbomachine comprises, from upstream to downstream in the direction of flow of the gases, at least one compressor, in which the air, previously sucked by the air inlet of the turbomachine, is compressed, a combustion chamber supplied with compressed air by said compressor in which the fuel is burned, and a turbine in which the burnt gases are expanded in order to rotate the turbine, whose compressor is also integral in rotation.

There are several types of compressors, axial compressors, on the one hand, and centrifugal or axial-centrifugal compressors on the other hand.

Centrifugal or axial-centrifugal compressors are often placed immediately upstream of the combustion chamber. Such a compressor comprises, from upstream to downstream, a rectifier, a spinning wheel, a radial diffuser, an axial diffuser, and a collector.

The straightener has fixed vanes for directing the flow of air entering the wheel. The wheel is integral in rotation with a rotor of the compressor and has blades that accelerate the air, to compress it, and to repress it radially. Depending on whether the compressor is a centrifugal or axial-centrifugal compressor, the blades print a purely centrifugal movement in the air entering the compressor, or on the contrary a first axial movement at the impeller inlet and then centrifugal output wheel.

At the outlet of the impeller, the compressed and centrifuged air is introduced into a radial diffuser provided with vanes which makes it possible to supply an axial diffuser in which the air is straightened axially and in which part of the air velocity is then transformed into additional pressure to further increase the pressure delivered by the compressor. A collector arranged at the outlet of the axial diffuser makes it possible to recover the compressed air for conveying it in the axis of the combustion chamber.

In such a compressor, the influence of the angular settings of the fixed vanes of the stator and the radial diffuser is predominant.

According to a first known design which has been described in the document FR-2.696.210-A1, it has been proposed to provide the compressor with a rectifier comprising a set of variable-pitch vanes, or variable-pitch entry grid, that is to say that the position of the blades is likely to vary angularly about an axis perpendicular to the general direction of the inlet duct in which these blades are placed, the position of all blades simultaneously varying.

Such a rectifier, also called IGV rectifier, acronym for "Inlet Guide Vanes" provides a gain compression efficiency provided by the wheel for low speeds of the turbomachine. Indeed, the modification of the setting of the blades of the rectifier reduces the flow rate and the pressure level that passes through the compressor and therefore, it reduces the power required to drive said compressor. It is therefore possible, thanks to the modification of the angular setting of the stator vanes, to precisely adjust the compressor supply conditions.

However, such a rectifier has no influence on the operating range of the compressor, which, for a given angular setting of the vanes of the radial diffuser, is limited by the pumping phenomenon.

Pumping is a fundamental cyclical phenomenon specific to dynamic compressors. Indeed, in a compressor, the compression is obtained by energy exchange in the gas set in motion in rows of fins. Like an airplane wing which, under high incidence and at low speed loses its lift and "picks up", a compressor can stall. At a reduced flow rate, the compressor no longer makes it possible to push the flow of air. As the compressor forms the interface of two networks at different pressures, namely respectively a suction network and a discharge network, in case of stall, the capacity of the discharge network, which has the highest pressure, is likely to empty into the capacity of the suction network by a flow against the current in the compressor.

When the discharge network has sufficiently emptied in the suction, the compressor finds new operating conditions allowing it to restore the flow in the right direction, until a new cycle of instability starts again.

These large cyclical flow fluctuations, called pumping, are like a series of shocks whose mechanical consequences can be disastrous, and cause, for example, fin fractures, or radial vibrations of very high level, with destruction of the internal sealing devices on the centrifugal compressors.

To avoid backflow and avoid pumping phenomena, there is a first solution consisting in providing the turbomachine with a device for discharging its compressor. Such a discharge device essentially comprises a tapping or sampling duct, carried out at the discharge of the compressor, which makes it possible, for reduced flow rates, to reduce the pressure downstream of the compressor in order to avoid back-ups and consequently avoid pumping phenomena. The air taken from the compressor can be discharged into different devices inside or outside the internal flow of a gas stream of the turbomachine.

A second solution consists, as described in document FR-2.958.967-A1, in preventing the compression ratio from being lowered by providing the compressor with a variable-pitch radial diffuser forming a variable-variable radial diffuser grid. . The simultaneous and controlled variation of the inclination of the vanes of the radial diffuser according to a given angle makes it possible to modify the compression ratio of the compressor, and consequently to avoid, for low speeds of the turbomachine, that the delivery network empties into the suction network and the known pumping phenomenon does not occur. The angle of inclination of the vanes of the radial diffuser grid can be suitably modified according to the speed of the turbomachine, which makes it possible to guarantee a sufficient pumping margin for each given regime, and consequently to extend the Compressor operating range. However, this solution has the disadvantage of penalizing the compression efficiency since it involves a mismatch of the radial diffuser due to the change in the angular setting of its blades.

DISCLOSURE OF THE INVENTION The object of the invention is therefore to combine the advantages of the two abovementioned technologies while eliminating the disadvantages by their association.

Advantageously, the invention consists in providing the compressor with the two aforementioned technologies, namely a radial variable-orifice diffuser grid making it possible to increase the pumping margin, and a variable-pitch inlet grille enabling the wheel to be readjusted. setting of the diffuser to obtain a satisfactory compression performance.

For this purpose, the invention proposes a centrifugal or axial-centrifugal turbomachine compressor comprising at least, from upstream to downstream, at least one inlet grille, a wheel provided with vanes configured to provide a radial flow of compressed air. at least one radial diffuser grid and an axial diffuser grid, characterized in that the input gate is a variable-pitch input gate or IGV and in that the at least one radial diffuser grid comprises at least one radial diffuser grid. less a variable-pitch grid.

According to other characteristics of the compressor: said variable-pitch grid of the radial diffuser comprises movable guide vanes, each of which is pivotally mounted between two extreme positions on either side of a radial direction, each vane being pivotally mounted according to a angular setting between substantially -15 ° to + 15 ° about a longitudinal axis, relative to its zero angular position corresponding to an orientation of the blade in the radial direction, - the variable-pitch inlet gate or IGV comprises movable guide vanes, each of which is pivotally mounted between two end positions located on either side of a general direction of a duct receiving said vanes, each vane being pivotally mounted according to an angular setting of between substantially -20 ° to + 80 ° about an axis perpendicular to said direction of said duct, with respect to its zero angular position corresponding to an orientation of d the blade in the general direction of said duct, - the angular setting of the variable-pitch inlet gate or IGV and the angular setting of the variable-pitch gate of the radial diffuser are dependent on one another. The invention also relates to a turbomachine comprising a centrifugal compressor of the type described above, characterized in that it comprises means for controlling the angular setting of the variable-pitch inlet gate or IGV and the angular setting of the wedge gate variable radial diffuser.

According to another characteristic of the turbomachine, the operation of the control means is subject to a stall law governing simultaneously the respective angular wedges of the variable-pitch inlet grille and the variable-pitch grille of the radial diffuser by adapting them to the aerodynamic configuration of the impeller, the angular setting of the variable-pitch inlet gate being controlled to optimize a partial-load compressor performance, and the angular setting of the variable-pitch gate of the radial diffuser being controlled to optimize a range of speeds of operation of said compressor. The invention finally relates to a method for controlling a turbomachine, characterized in that it comprises at least one step during which, for a determined operating speed of the compressor, the control means control the angular setting of the grid variable pitch of the radial diffuser so as to increase the operating range, and at least one step during which, depending on the angular setting of the variable-pitch grid of the radial diffuser, and the determined operating speed, the means of control determine with the aid of said operating law the angular setting of the input gate variable pitch to optimize the efficiency of the compressor and drive said angular setting.

BRIEF DESCRIPTION OF THE FIGURES The invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings, in which: which: - Figure 1 is an axial sectional view of a turbomachine according to a first state of the art; - Figure 2 is an axial sectional view of detail of a centrifugal compressor according to the first state of the art of Figure 1; - Figure 3 is an axial sectional view of detail of a centrifugal compressor according to a second state of the art; - Figure 4 is an axial sectional view of detail of a centrifugal compressor according to a third state of the art; FIG. 5 is a view in axial section of detail of a centrifugal compressor according to the invention; FIG. 6 is a schematic axial view of the grids and vanes of a radial diffuser of the compressor of FIG. 5; FIG. 7 is a block diagram illustrating the steps of a method for controlling a turbomachine according to the invention;

In the following description, like reference numerals designate like parts or having similar functions.

DETAILED DESCRIPTION

FIG. 1 shows a turbomachine 10 produced according to a state of the art. In the present case, the turbomachine 10 is, in a nonlimiting manner of the invention, a turboprop 10.

In known manner, such a turbomachine 10 comprises, from upstream to downstream along the direction of flow of the gases, one or more compressor modules 14, 16 arranged in series, in particular a low-pressure compressor 14 and a high compressor. pressure 16, which compresses air sucked by an air inlet 12. The air, after passing through the compressor modules 14, 16, is then introduced into a combustion chamber 18 where it is mixed with a fuel and burned. The combustion gases pass through one or more turbine modules 20, 22, in particular a high-pressure turbine 20 and a low-pressure turbine 22, which drive the compressor (s) 14, 16 via high-pressure and low-pressure shafts. associated pressure, of which only the low-pressure shaft 24 is visible in Figure 1. The gases are finally ejected either in a nozzle (not shown) to produce a propulsive force, either by reaction or on a free turbine to produce the power that is recovered on a transmission shaft. The low-pressure shaft 24 is for example coupled to the input shaft 26 of a gearbox 28 which has an output shaft 30 capable of driving a propeller (not shown).

FIG. 2 diagrammatically represents the detail of a compressor of such a turbomachine, for example and in a nonlimiting manner, the low-pressure compressor 14, produced according to a first known design of the state of the art.

In known manner, the compressor 14 is a centrifugal or axial-centrifugal compressor of X axis comprising at least, from upstream to downstream, at least one input grid 32 of rectifier, a wheel 34 provided with vanes 36 configured to provide a radial flow of Z-direction compressed air at the output of the impeller 34, at least one gate 38 of a radial diffuser 39, and a gate 40 of an axial diffuser 41. In FIG. 2, the compressor 14 comprises only a grid 38 for its radial diffuser 39.

The inlet grille 32 is conventionally constituted by blades 42 whose inclination makes it possible to straighten the incoming air flow F which enters an inlet duct 44 so that it impinges on the vanes of the wheel 34 optimal.

Depending on whether the compressor is a centrifugal compressor or an axial-centrifugal compressor, the vanes 36 of its wheel 34 have different configurations.

In the case of an axial-centrifugal compressor, the vanes 36 are configured to axially compress the inlet flow of the impeller 34, then to provide a compressed radial flow at the output of the impeller 34.

In the case of a centrifugal compressor such as that shown in FIG. 2, the vanes 36 are only intended to provide a compressed radial flow at the output of the impeller 34.

The gate 38 of the radial diffuser 39 conventionally comprises stationary vanes 46 intended to diffuse the compressed air towards the gate 40 of the axial diffuser 41, which comprises, in turn, vanes 48 intended to straighten the flow before it is introduced into a collector 50 .

In this conventional design, the blades 42 of the inlet grille 32 and the blades 46 of the grid 38 of the radial diffuser 39 are fixed. Consequently, they do not make it possible to adapt the efficiency of the compressor 14, nor do they make it possible to adapt the operation of the compressor 14 to the pumping phenomenon, which is therefore limited in its operating range.

According to a second known design which has been shown in FIG. 3, the inlet gate 32 is of variable pitch, that is to say that the wedging or angular position p of the blades 42 of its diffuser is capable of varying angularly. around an axis R perpendicular to the general direction of the inlet duct 44 in which are placed these vanes 42, here the X direction, the position of all the vanes 42 varying simultaneously.

This input gate 32 makes it possible to provide a gain in the compression efficiency provided by the impeller for the low speeds of the turbomachine. This is achieved by a modification of the angular setting of the vanes 42 of the rectifier which makes it possible to reduce the flow rate and the level of pressure which passes through the compressor 14 and thereby reduces the power required to drive the compressor 14. This modification the angular setting of the blades 42 makes it possible to adjust the supply conditions of the impeller 34, and consequently to optimize the efficiency of the compressor, in particular for the low rotational speeds of the compressor 14. However, such a compressor remains dependent on the phenomena pumping which limits its range of use.

It is therefore possible, thanks to the modification of the angular setting of the vanes 42 of the rectifier, to precisely adjust the supply conditions of the compressor 14.

However, such a rectifier has no influence on the operating range of the compressor, which is limited by the pumping phenomenon.

According to a third known design which has been shown in Figure 4, the compressor is provided with a grid 38 of the radial diffuser 39 which comprises blades 46 variable pitch. The blades 46 are in particular pivotable about an axis D substantially parallel to the axial direction X, that is to say perpendicular to the radial direction Z of the duct 52 in which the vanes 46 are arranged. The simultaneous and controlled variation of the inclination of the blades 46 of the gate 38 of the radial diffuser 39 according to a predetermined angular setting makes it possible to modify the compression ratio of the compressor 14, and consequently to avoid, for low speeds of the turbomachine, that the delivery network downstream of the compressor 14 is empty in the suction network upstream of the compressor 14 and that does occur the known phenomenon of pumping.

In this configuration, the angular setting of the blades 46 of the grid 38 of the radial diffuser 39 is modified for each speed of the turbomachine to maintain a compression ratio to prevent backflow. Thus, the pumping margin is generally increased, and in particular it is thus possible to cover a larger range of speeds for which the turbomachine is operational without any risk of pumping. However, this design has the disadvantage of penalizing the compression efficiency, since it involves a mismatch of the radial diffuser 39 and its gate 38 to the wheel 34 due to the change of the angular setting of these blades 46. The invention makes it possible to overcome this last disadvantage by rehabilitating the impeller 34 to the radial diffuser 39 by modifying the compression efficiency with at least one input gate 32 variable pitch IGV.

Thus, the invention comprises a centrifugal or axial-centrifugal compressor 14 of the type described above, characterized in that the input gate 32 is a variable-pitch input gate or IGV and in that at least one gate of radial diffuser 39 is a variable-pitch gate 38.

According to the invention, there is shown in Figure 5 a compressor 14 having a radial diffuser 39 having a fixed gate 37 and a gate 38 variable pitch. Fixed vanes 45 of the fixed grid 37 and moving blades 46 of the variable-pitch grid 38 have been schematically represented in FIG. 6.

Each blade 46 movable direction is pivotally mounted between two extreme positions on either side of the radial direction Z relative to its zero angular position corresponding to an orientation of the blade 46 in the radial direction Z. Thus, each blade 46 is pivotally mounted substantially about its longitudinal axis D, with respect to a zero angular position corresponding to an orientation of the blade 46 in the radial direction Z. More particularly, each blade 46 is pivotally mounted according to an angular setting p between substantially -15 ° to + 15 ° around its longitudinal axis D, with respect to a zero angular position.

It will be understood that this configuration is not limiting of the invention, and that the radial diffuser 39 could comprise a single blade grid, provided that it is the grid 38 variable pitch.

Furthermore, the input grid or IGV, also variable-pitch, has its vanes 42 movable and pivoting. Each blade 42 is pivotally mounted between two extreme positions located on either side of a general direction of the conduit 44 receiving said vanes 42, here the X direction. Each vane 42 is pivotally mounted with an angular wedge δ between substantially -20 ° to + 80 ° around the axis R perpendicular to the direction X of the duct 44, the zero angular position corresponding to an orientation of the blade 42 in the general direction X of said duct.

In the preferred embodiment of the invention, the angular setting p of the input gate 32 with variable pitch or IGV and the angular setting δ of the variable-pitch gate 38 of the radial diffuser 39 are dependent on one of the 'other. This configuration advantageously makes it possible, for a given angular setting δ of the variable-pitch grid 38 of the radial diffuser 39, to readjust the wheel 34 to the grid 38 of the radial diffuser 39 by modifying the compression efficiency by means of the angular setting p input gate 32 with variable pitch IGV.

In known manner, all the known means of the state of the art suitable for ensuring the rotation of the axes D, R can be used.

In particular, the axes D, R can be driven by electric actuators step, pneumatic actuators or hydraulic actuators.

Advantageously, the axes D, R can be driven by a double actuator simultaneously ensuring the rotation of the axes D, R. This configuration makes it possible by its compactness to facilitate the integration of the double actuator in the turbomachine 10.

Thus, a turbomachine 10 comprising a centrifugal compressor 14 of the type described above comprises means for controlling the angular setting of the variable-pitch inlet gate 32 or IGV and the angular setting of the variable-pitch grille 38 of the radial diffuser 39 allowing to control the operation of these actuators.

Advantageously, the operation of the control means is subject to a shimming law simultaneously governing the respective angular wedges p, δ of the inlet gate 32 and the variable-pitch grid 38 of the radial diffuser 39 by adapting them to the aerodynamic configuration pallets 36 of the impeller 34. Thanks to this law, the angular setting p of the inlet gate 32 is controlled to optimize the efficiency of the compressor 14 at partial load and the angular setting δ of the grid 38 variable pitch of the radial diffuser 39 is controlled to optimize a range of operating speeds of the compressor 14. In practice, the angular setting δ of the variable-pitch gate 38 of the radial diffuser 39 is controlled to optimize a range of operating speeds of the compressor 14, and the angular setting p of the inlet gate 32 is controlled to optimize the efficiency of the compressor 14 at partial load as a function of the angular setting δ of the grill the variable valve 38 of the radial diffuser 39.

In this configuration, as shown in FIG. 6, the means for controlling the angular setting of the variable-pitch inlet grille 32 or IGV and the angular setting of the variable-pitch grille 38 of the radial diffuser 39 are governed by a control method of the turbomachine which comprises at least one step ET1 during which, for a given operating speed N of the compressor 14, the control means control the angular setting δ of the variable-pitch gate 38 of the radial diffuser 39 of in order to increase the operating range, and at least one step ET2 during which, as a function of the angular setting δ of the gate 38 of the radial diffuser 39 and the determined operating speed N, the control means determine using of said operating law the angular setting p of the input gate 32 to optimize the efficiency of the compressor 14 and drive said angular setting p. The invention thus makes it possible to optimize the performance of a centrifugal or axial-centrifugal compressor in a simple and efficient manner.

Claims (7)

1. Centrifugal or axial-centrifugal turbomachine compressor (14) comprising, from upstream to downstream, at least one inlet gate (32), a wheel (34) provided with at least pallets (36) configured to providing a compressed air radial flow, at least one gate (38) of a radial diffuser (39) and a gate (40) of an axial diffuser (41), characterized in that the gate (32) ) is a variable-pitch input grid (p) or IGV and in that the at least one grid of the radial diffuser (39) comprises at least one gate (38) variable pitch. 2. Centrifugal compressor (14) according to claim 1, characterized in that said grid (38) variable pitch (δ) of the radial diffuser (39) comprises movable guide vanes (46) each of which is pivotally mounted between two extreme positions on either side of a radial direction (Z), each blade (46) being pivotally mounted according to an angular setting (δ) between substantially -15 ° to + 15 ° around a longitudinal axis (D), relative to its zero angular position corresponding to an orientation of the blade in the radial direction. 3. Centrifugal compressor according to one of the preceding claims, characterized in that the input gate (32) variable pitch (p) or IGV comprises movable guide vanes (42) each of which is pivotally mounted between two extreme positions located on either side of a general direction (X) of a duct (44) receiving said blades (42), each blade being pivotally mounted according to an angular setting (p) between substantially -20 ° to + 80 ° about an axis (R) perpendicular to said direction (X) of said duct (44), with respect to its zero angular position corresponding to an orientation of the blade (42) in the general direction (X) of said duct (44); ). Centrifugal compressor according to one of the preceding claims, characterized in that the angular setting (p) of the variable-pitch inlet gate (32) and the angular setting (δ) of the variable-pitch gate ( 38) of the radial diffuser (39) are dependent on each other. 5. Turbomachine (10) comprising a centrifugal compressor (14) according to one of the preceding claims, characterized in that it comprises means for controlling the angular setting (p) of the input gate (32) variable pitch or IGV and the angular setting (δ) of the grid (38) variable pitch of the radial diffuser (39). 6. Turbomachine (10) according to the preceding claim, characterized in that the operation of the control means is subject to a shimming law simultaneously governing the respective angular wedges (ρ, δ) of the input gate (32) wedging variable and variable-pitch grid (38) of the radial diffuser (39) adapting them to the aerodynamic configuration of the impeller (34), the angular setting (p) of the variable-pitch inlet grille (32) being controlled to optimize efficiency of the partial load compressor (14) and the angular setting (δ) of the variable-pitch gate (38) of the radial diffuser (39) being controlled to optimize a range of operating speeds of said compressor (14). 7. A method of controlling a turbomachine (10) according to the preceding claim, characterized in that it comprises at least one step (ET1) during which, for a given operating speed (N) of the compressor (14). , the control means control the angular setting (δ) of the variable-pitch gate (38) of the radial diffuser (39) so as to increase the operating range, and at least one step (ET2) during which, in function of the angular setting (δ) of the variable-pitch grid (38) of the radial diffuser (39) and the determined operating speed (N), the control means determine with the aid of said operating law the angular setting ( p) of the input gate (32) variable pitch to optimize the efficiency of the compressor and control said angular setting (p) of said input gate (32).