FR3069020A1 - 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

Variable speed turbomachine compressor

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

STATE OF THE PRIOR ART

In 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 in by the air inlet of the turbomachine, is compressed, a combustion chamber supplied with air compressed by said compressor in which the fuel is burned, and a turbine in which the burnt gases are expanded so as in particular to cause the turbine to rotate, the compressor of which 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.

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 impeller, a radial diffuser, an axial diffuser, and a manifold.

The rectifier has fixed blades designed to direct the air flow entering the impeller. The impeller is integral in rotation with a compressor rotor and it has vanes which make it possible to accelerate the air, to compress it, and to discharge it radially. Depending on whether the compressor is a centrifugal or axial-centrifugal compressor, the blades impart a purely centrifugal movement to the air which enters the compressor, or on the contrary a movement initially axial at the inlet of the impeller then centrifugal at the outlet of the impeller.

At the outlet of the impeller, the compressed and centrifuged air is introduced into a radial diffuser fitted with blades which makes it possible to supply an axial diffuser in which the air is straightened axially and in which part of the speed of the air is then transformed into additional pressure to further increase the pressure supplied by the compressor. A manifold arranged at the outlet of the axial diffuser makes it possible to recover the compressed air in order to convey it in the axis of the combustion chamber.

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

According to a first known design which has been described in document FR-2,696,210-A1, it has been proposed to provide the compressor with a rectifier comprising a set of blades with variable setting, or input grid with variable setting, that is to say that the position of the blades is liable 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 the blades varying simultaneously.

Such a rectifier, also called an IGV rectifier, an acronym standing for "Inlet Guide Vanes" allows a gain in the compression efficiency provided by the impeller for the low engine speeds. In fact, the modification of the setting of the stator vanes makes it possible to reduce the flow rate and the pressure level which passes through the compressor and therefore makes it possible to reduce the power necessary to drive said compressor. It is therefore possible, thanks to the modification of the angular setting of the stator vanes, to precisely regulate the supply conditions of the compressor.

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

Pumping is a fundamental cyclic phenomenon specific to dynamic compressors. Indeed, in a compressor, 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 stalls, a compressor can stall. At reduced flow, the compressor can no longer push the air flow. As the compressor forms the interface of two networks at different pressures, namely a suction network and a discharge network, in the event of a stall, the capacity of the discharge network, which has the highest pressure, is likely to empty itself into the capacity of the suction network by a flow against the current in the compressor.

When the discharge network has emptied enough 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 begins again.

These large cyclic fluctuations in flow, called pumping, are similar to a series of shocks whose mechanical consequences can be disastrous, and cause, for example, ruptured fins, or very high level radial vibrations, with destruction of internal sealing devices on centrifugal compressors.

To avoid backflow and to 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, produced at the discharge of the compressor, which makes it possible, for reduced flow rates, to drop the pressure downstream of the compressor in order to avoid backflow and consequently d '' avoid pumping phenomena. The air taken from the compressor can be evacuated in different devices inside or outside the internal flow of a gas stream from the turbomachine.

A second solution consists, as has been described in the document FR-2,958,967-A1, in avoiding the drop in the compression ratio by providing the compressor with a radial diffuser with variable setting forming a radial diffuser grid with variable setting . The simultaneous and controlled variation of the inclination of the blades of the radial diffuser at a determined angle makes it possible to modify the compression ratio of the compressor, and consequently to avoid, for low engine speeds, the discharge network empties into the suction network and does not occur the known phenomenon of pumping.

The angle of inclination of the blades of the grid of the radial diffuser can be modified appropriately as a function of the speed of the turbomachine, which makes it possible to guarantee a sufficient pumping margin for each given speed, 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.

STATEMENT OF THE INVENTION

The invention therefore aims to combine the advantages of the two aforementioned technologies, while eliminating the disadvantages, thanks to their association.

Advantageously, the invention consists in providing the compressor with the two aforementioned technologies, namely a radial diffuser grid with variable setting allowing the pumping margin to be increased, and an input grid with variable setting, making it possible to readjust the impeller to setting of the diffuser in order to obtain a satisfactory compression yield.

To this end, the invention provides a centrifugal or axial-centrifugal compressor of a turbomachine comprising at least, from upstream to downstream, at least one inlet grid, a impeller provided with vanes configured to provide a radial flow of compressed air , at least one radial diffuser grid and one axial diffuser grid, characterized in that the inlet grid is a variable-timing input grid or IGV and in that the at least one radial diffuser grid comprises at minus a grid with variable setting.

According to other characteristics of the compressor:

- Said variable setting 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 blade being pivotally mounted according to an angular setting comprised between substantially -15 ° at + 15 ° around a longitudinal axis, with respect to its zero angular position corresponding to an orientation of the blade in the radial direction,

- the variable-timing input gate or IGV comprises movable guide vanes, each of which is pivotally mounted between two extreme positions situated on either side of a general direction of a duct receiving said vanes, each vane being pivotally mounted according to an angular setting comprised between substantially -20 ° to + 80 ° around an axis perpendicular to said direction of said conduit, relative to its zero angular position corresponding to an orientation of the blade in the general direction of said conduit,

the angular setting of the variable-timing input grid or IGV and the angular setting of the variable-timing grid of the radial diffuser are dependent on each other.

The invention also relates to a turbomachine comprising a centrifugal compressor of the type described above, characterized in that it includes means for controlling the angular setting of the variable-timing input gate or IGV and the angular setting of the timing grid variable of the radial diffuser.

According to another characteristic of the turbomachine, the operation of the control means is subject to a timing law simultaneously regulating the respective angular settings of the variable-timing input grid and the variable-timing grid of the radial diffuser by adapting them to the aerodynamic configuration of the impeller, the angular setting of the variable-timing input grid being controlled to optimize a performance of the compressor at partial load and the angular setting of the variable-timing grid of the radial diffuser being controlled to optimize a speed range 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 with variable setting 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 setting grid of the radial diffuser, and the determined operating regime, the means of control determine using said operating law the angular setting of the variable-timing input grid to optimize the efficiency of the compressor and control 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 description which follows, given by way of nonlimiting example and with reference to the appended drawings, in 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 detail view of a centrifugal compressor according to the first state of the art of Figure 1;

- Figure 3 is an axial sectional detail view of a centrifugal compressor according to a second state of the art;

- Figure 4 is an axial sectional detail view of a centrifugal compressor according to a third state of the art;

- Figure 5 is an axial sectional detail view of a centrifugal compressor according to the invention;

- Figure 6 is a schematic axial view of the grids and vanes of a radial diffuser of the compressor of Figure 5;

- Figure 7 is a block diagram illustrating the steps of a method of controlling a turbomachine according to the invention;

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

DETAILED DESCRIPTION

FIG. 1 shows a turbomachine 10 produced in accordance with a state of the art. In the present case, the turbomachine 10 is, without limitation of the invention, a turboprop engine 10.

In known manner, such a turbomachine 10 comprises, from upstream to downstream in the direction of gas flow, one or more compressor modules 14, 16 arranged in series, in particular a low pressure compressor 14 and a high compressor pressure 16, which compress the air sucked in 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 shafts. associated pressures, of which only the low pressure shaft 24 is visible in FIG. 1. The gases are finally ejected either in a nozzle (not shown) to produce a propelling force, either by reaction, or on a free turbine to produce the power that is recovered on a drive shaft. The low pressure shaft 24 is for example coupled to the input shaft 26 of a reduction gear 28 which includes an output shaft 30 capable of driving a propeller (not shown).

FIG. 2 schematically represents the detail of a compressor of such a turbomachine, for example and without limitation, the low pressure compressor 14, produced in accordance with a first design known from the state of the art.

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

The inlet grid 32 conventionally consists of fixed vanes 42 whose inclination makes it possible to straighten the incoming air flow F which enters an inlet duct 44 so that it attacks the paddles of the impeller 34 so optimal.

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

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

In the case of a centrifugal compressor like the one shown in FIG. 2, the vanes 36 are only intended to provide a compressed radial flow at the outlet of the impeller 34.

The grid 38 of the radial diffuser 39 conventionally comprises fixed blades 46 intended to diffuse the compressed air towards the grid 40 of the axial diffuser 41, which for its part comprises fixed blades 48 intended to straighten the flow before its introduction into a collector 50 .

In this conventional design, the vanes 42 of the inlet grille 32 and the vanes 46 of the grille 38 of the radial diffuser 39 are fixed. Consequently, they do not make it possible to adapt the efficiency of the compressor 14, any more than they allow 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 represented in FIG. 3, the inlet gate 32 is of variable setting, that is to say that the setting or angular position p of the vanes 42 of its diffuser is liable to vary angularly around an axis R perpendicular to the general direction of the inlet duct 44 in which these blades 42 are placed, here the direction X, the position of all the blades 42 varying simultaneously.

This inlet gate 32 provides a gain in the compression efficiency provided by the impeller for the low speeds of the turbomachine. This is obtained 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 pressure level which passes through the compressor 14 and therefore which makes it possible to reduce the power necessary to drive the compressor 14. This modification the angular setting of the vanes 42 makes it possible to adjust the feed conditions of the impeller 34, and consequently to optimize the efficiency of the compressor, in particular for the low revolutions of the compressor 14. However, such a compressor remains dependent on the phenomena that limit 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 regulate 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 FIG. 4, the compressor is provided with a grid 38 of the radial diffuser 39 which comprises vanes 46 with variable setting. 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 blades 46 are arranged. The simultaneous and controlled variation of the inclination of the blades 46 of the grid 38 of the radial diffuser 39 according to a determined angular setting makes it possible to modify the compression ratio of the compressor 14, and consequently to avoid, for low engine speeds, the discharge network downstream of the compressor 14 is emptied into the suction network upstream of the compressor 14 and only the known phenomenon of pumping occurs.

In this configuration, the angular setting of the vanes 46 of the grid 38 of the radial diffuser 39 is modified for each speed of the turbomachine in order to maintain a compression ratio making it possible to avoid backflow. The pumping margin is therefore increased overall, and in particular it is thus possible to cover a greater range of speeds for which the turbomachine is operational without 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 grid 38 to the impeller 34 due to the change in the angular setting of these blades 46.

The invention overcomes this latter drawback by readjusting the impeller 34 to the radial diffuser 39 by modifying the compression efficiency using at least one input gate 32 with variable setting IGV.

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

In accordance with the invention, FIG. 5 shows a compressor 14 comprising a radial diffuser 39 comprising a fixed grid 37 and a grid 38 with variable setting. Fixed blades 45 of the fixed grid 37 and movable blades 46 of the grid 38 with variable setting have been shown schematically in FIG. 6.

Each movable guide blade 46 is pivotally mounted between two extreme positions on either side of the radial direction Z with respect 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 about its longitudinal axis D, relative 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 grid of blades, provided that it is the grid 38 with variable setting.

Furthermore, the inlet grid or IGV, also with variable timing, has its movable and pivoting guide vanes 42. Each blade 42 is pivotally mounted between two extreme positions located on either side of a general direction of the conduit 44 receiving said blades 42, here the direction X. Each blade 42 being pivotally mounted with an angular setting 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 the said duct.

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

In known manner, all the means known from the prior art capable of ensuring the rotation of the axes D, R can be used.

In particular, the axes D, R can be driven by electrical actuators of the step-by-step type, 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 input gate 32 with variable setting or IGV and the angular setting of the gate 38 with variable setting of the radial diffuser 39 allowing to control the operation of these actuators.

Advantageously, the operation of the control means is subject to a timing law simultaneously regulating the respective angular settings p, δ of the inlet gate 32 and of the gate 38 with variable setting of the radial diffuser 39 by adapting them to the aerodynamic configuration. paddles 36 of the impeller 34. Thanks to this law, the angular setting p of the inlet grid 32 is controlled to optimize the efficiency of the compressor 14 at partial load and the angular setting δ of the grid 38 with variable setting 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 grid 38 with variable setting 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 input grid 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 38 with variable setting of the radial diffuser 39.

In this configuration, as illustrated in FIG. 6, the means for controlling the angular setting of the input gate 32 with variable setting or IGV and the angular setting of the gate 38 with variable setting of the radial diffuser 39 are governed by a method for controlling the turbomachine which comprises at least one step ET1 during which, for a determined operating speed N of the compressor 14, the control means control the angular setting δ of the grid 38 with variable setting of the radial diffuser 39 of so as to increase the operating range, and at least one step ET2 during which, as a function of the angular setting δ of the grid 38 of the radial diffuser 39 and of the determined operating speed N, the control means determine at using said operating law the angular setting p of the input gate 32 to optimize the efficiency of the compressor 14 and control said angular setting p.

The invention therefore makes it possible to optimize the performance of a centrifugal or axial-centrifugal compressor in a simple and effective manner.

Claims (7)

1. Centrifugal or axial-centrifugal compressor (14) of a turbomachine (10) comprising, from upstream to downstream, at least one inlet grid (32), a impeller (34) provided with at least pallets (36) configured for providing a radial flow of compressed air, at least one grid (38) of a radial diffuser (39) and a grid (40) of an axial diffuser (41), characterized in that the inlet grid (32 ) is an input grid with variable setting (p) or IGV and in that the at least one grid of the radial diffuser (39) comprises at least one grid (38) with variable setting. 2. centrifugal compressor (14) according to claim 1, characterized in that said grid (38) with variable setting (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 grid (32) with variable setting (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 ). 4. Centrifugal compressor according to one of the preceding claims, characterized in that the angular setting (p) of the input grid (32) with variable setting or IGV and the angular setting (δ) of the variable setting grid ( 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 grid (32) with variable setting or IGV and the angular setting (δ) of the grid (38) with variable setting 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 timing law simultaneously regulating the respective angular settings (ρ, δ) of the input grid (32) variable and of the variable setting grid (38) of the radial diffuser (39) by adapting them to the aerodynamic configuration of the impeller (34), the angular setting (p) of the variable setting input grid (32) being controlled to optimize a performance of the compressor (14) at partial load and the angular setting (δ) of the grid (38) with variable setting of the radial diffuser (39) being controlled to optimize a range of operating speeds of said compressor (14). 7. Method for 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 setting grid (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 setting grid (38) of the radial diffuser (39) and of the operating regime (N) determined, the control means determine using said operating law the angular setting ( p) of the input grid (32) with variable setting in order to optimize the efficiency of the compressor and control said angular setting (p) of said input grid (32).