Turbomachine comprising a privileged injection device and corresponding injection method

Abstract

A turbomachine including: a combustion chamber, with a fuel injection device in the combustion chamber; a supply mechanism supplying fuel to the fuel injection device; a mechanism determining instantaneous variation of fuel flow rate of the supply mechanism; and a regulation mechanism regulating the fuel flow rate of the injection device according to the instantaneous variation of the fuel flow rate of the supply mechanism determined by the determination mechanism.

Claims

1. A turbomachine comprising: a combustion chamber, with a fuel injection device in the combustion chamber, the fuel injection device including an injection ramp including a privileged injector and a main injector, the privileged injector being disposed radially outward of the main injector; a fuel meter which supplies fuel to the fuel injection device; a gas generator shaft; and circuitry configured to determine an instantaneous variation of a fuel flow rate of the fuel meter, compare the instantaneous variation of the fuel flow rate of the fuel meter to a first predetermined threshold, increase a fuel flow rate to the privileged injector relative to the main injector if the instantaneous variation of the fuel flow rate of the fuel meter is less than the first predetermined threshold, the fuel meter supplying fuel to both the privileged injector and the main injector, determine an instantaneous acceleration of the gas generator shaft, compare the instantaneous acceleration of the gas generator shaft to a second predetermined threshold, and suppress the fuel flow rate to the privileged injector relative to the main injector so that the fuel flow rate to the privileged injector is equal to the fuel flow rate to the main injector if the instantaneous acceleration of the gas generator shaft is greater than the second predetermined threshold, the instantaneous variation of the fuel flow rate of the fuel meter is greater than or equal to the first predetermined threshold, and the fuel flow rate of the privileged injector is relatively higher than the fuel flow rate to the main injector, the fuel meter supplying fuel to both the privileged injector and the main injector.

2. The turbomachine according to claim 1, further comprising a distributor of fuel flow between the privileged injector and the main injector.

3. The turbomachine according to claim 1, wherein the instantaneous variation of the fuel flow rate of the fuel meter is measured by a resolver connected to the fuel meter.

4. The turbomachine according to claim 1, further comprising a control of the fuel meter for adjusting a fuel flow rate delivered by the fuel meter, and the instantaneous variation of the fuel flow rate of the fuel meter is determined from a reading of set values sent to the control of the fuel meter for adjusting the fuel flow rate delivered by the fuel meter.

5. The turbomachine according to claim 1, wherein the circuitry is configured to suppress the flow rate increase of the privileged injector relative to the fuel flow rate of the main injector after a predetermined period has elapsed.

6. A method for regulating the fuel injection of a fuel injection device in a combustion chamber of a turbomachine, the fuel injection device including an injection ramp including a privileged injector and a main injector, the turbomachine including a fuel meter which supplies fuel to the fuel injection device and a gas generator shaft, the method comprising: supplying fuel to both the privileged injector and the main injector using the fuel meter, the privileged injector being disposed radially outward of the main injector; determining an instantaneous variation of a fuel flow rate of the fuel meter; comparing the instantaneous variation of the fuel flow rate of the fuel meter to a first predetermined threshold; increasing a fuel flow rate to the privileged injector relative to the main injector if the instantaneous variation of the fuel flow rate of the fuel meter is less than the first predetermined threshold while the fuel meter supplies fuel to both the privileged injector and the main injector; determining an instantaneous acceleration of the gas generator shaft; comparing the instantaneous acceleration of the gas generator shaft to a second predetermined threshold; and suppressing the fuel flow rate to the privileged injector relative to the main injector so that the fuel flow rate to the privileged injector is equal to the fuel flow rate to the main injector if the instantaneous acceleration of the gas generator shaft is greater than the second predetermined threshold, the instantaneous variation of the fuel flow rate of the fuel meter is greater than or equal to the first predetermined threshold, and the fuel flow rate to the privileged injector is relatively higher than the fuel flow rate to the main injector, while the fuel meter supplies fuel to both the privileged injector and the main injector.

7. The method according to claim 6, wherein the fuel flow rate of the privileged injector is increased relatively to the fuel flow rate of the main injector by distributing a global flow from the injection device in a privileged way towards the privileged injector.

8. The method according to claim 6, wherein the fuel flow rate of the privileged injector is increased for a predetermined period.

9. The method according to claim 6, wherein the flow rate increase of the privileged injector relatively to the fuel flow rate of the main injector is suppressed after a predetermined period has elapsed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages will be better understood upon reading the detailed description made hereafter of different embodiments given as non-limiting examples. This description refers to the appended figures, wherein:

(2) FIG. 1 schematically illustrates a turbomachine according to the invention, and

(3) FIG. 2 illustrates a flow chart describing the steps of the regulation method according to the invention.

MORE DETAILED DESCRIPTION

(4) FIG. 1 illustrates a turbomachine 10 comprising a free turbine 20 and a gas generator 30. The gas generator 30 includes a compressor 300, a turbine wheel 310 mounted on a gas generator shaft 320 and a combustion chamber 330. The gases leaving the gas generator 30 drive the turbine wheel 200 of the free turbine 20 mounted on a turbine shaft 210, into rotation.

(5) The turbomachine 10 is further equipped with an injection device 340 comprising an injection ramp comprising main injectors 342 and privileged injectors 344. The injection device 340 is regulated by regulation means 350 in order to regulate the fuel flow rate in the combustion chamber 330. The regulation means 350 are notably intended for increasing the flow rate of the privileged injectors 344. Supply means 360 supply the injection device 340 with fuel. For the clarity of the figure, the connections between the supply means 360 and the injection device 340 are not illustrated. The supply means 360 comprise a fuel meter and a control of the meter (not shown).

(6) The turbomachine 10 also comprises determination means 370 for determining the instantaneous variation of the fuel flow rate of the supply means 360. These determination means 370 for example comprise a computer and a memory (not shown) including means for reading the set values sent to the control of the fuel meter (control set values). The determination means 370 are connected to the regulation means 350.

(7) Moreover, the turbomachine 10 comprises the measurement means 380 for measuring the acceleration of the gas generator shaft 320. These measurement means 380 measure the speed of rotation of the gas generator shaft, from which is inferred the acceleration of the gas generator shaft 320, from the phonic wheel 322 firmly attached to the gas generator shaft 320 and for example, by means of a computer and a memory (not shown). The measurement means 380 are connected to the regulation means 350.

(8) The arrows on the connections between the supply means 360, and the determination means 370, the measurement means 380, the regulation means 350 and the injection device 340 represent the flows of information circulating among these different elements.

(9) The operation of this turbomachine 10 is described with reference to FIG. 2. The flow chart of FIG. 2 illustrates the method according to the invention for automatically regulating the fuel injection into the combustion chamber 330 of the turbomachine 10.

(10) The method preferably begins when the turbomachine has started and stops when the turbomachine is stopped, even if this happens during execution of the method. For this reason, there is no end for indicating the end of the method in FIG. 2. Subsequently, for designating a completely performed cycle of the regulation method, we shall use the term of regulation cycle.

(11) The method therefore starts with step E0 start. The method is then divided into two main steps: a first step EI where the instantaneous variation of the fuel flow rate of the supply means 360 is determined, and a second step EII where the instantaneous fuel flow rate is regulated in the combustion chamber 330 according to the instantaneous variation of the fuel flow rate of the supply means 360, determined during step EI.

(12) The step EI comprises a single step E1 which consists of determining the instantaneous speed dXR/dt of the meter, XR corresponding to the position of the meter. This instantaneous speed determination is achieved in a known way, moreover by determination means 370, and in particular by means for reading the set value sent to the control of the meter in order to drive the position of the meter, of the computer and of the memory of the determination means 370. It will be noted that the speed of the meter is positive if the control set value aims at increasing the flow rate of the meter while it is negative if the control set value aims at reducing the flow rate of the meter. At the end of step E1, the first step EI for determining the instantaneous variation of the fuel flow rate of the supply means 360 is completed. Indeed, the instantaneous speed dXR/dt of the meter is representative of the variation of the fuel flow rate of the supply means 360. At the end of step EI, the method switches to step EII. In other words, at the end of step E1, the method switches to step E2.

(13) The step E2 consists of comparing the value of the instantaneous speed dXR/dt of the meter relatively to a predetermined threshold value V.sub.ref. It will be noted that during a sudden deceleration of the turbomachine the instantaneous speed dXR/dt is negative and therefore for detecting this sudden deceleration, the threshold value V.sub.ref is also negative. If the instantaneous variation of the instantaneous dXR/dt is less than the predetermined threshold value V.sub.ref (YES at the end of step E3), the method determines whether there is a risk of extinction of combustion and switches to step E3. If the instantaneous speed dXR/dt is greater than or equal to the predetermined threshold value V.sub.ref (NO at the end of step E3), the method switches to step E4. The step E2 is carried out by the regulation means 350.

(14) The step E3 consists of increasing the flow rate of the privileged injectors 344 relatively to the flow rate of the main injectors 342, this increase being achieved the regulation means 350. When the flow rate of the privileged injectors is increased, the step EII for regulating the instantaneous flow rate is completed; the regulation method completes its regulation cycle and starts a subsequent cycle by again beginning from step E1. Of course, the execution of a subsequent regulation cycle may be timed out. That is to say that the execution of the subsequent step is not immediate, and a certain delay elapses before executing this subsequent cycle. This time-out is achieved for example between step EII and step EI.

(15) Moreover, it is understood that, if during the next cycle, the step E2 also leads to step E3, depending on the alternatives, the fuel flow rate of the privileged injector may again be increased or else be maintained at the level at which it was increased during the previous cycle.

(16) The step E4 consists of checking that the flow rate of the privileged injectors 344 has not increased relatively to the flow rate of the main injectors 342, this increase for example resulting from a step E3 carried out during a previous regulation cycle. This operation is also achieved by the regulation means 350. If the flow rate of the privileged injector 344 is increased (YES at the end of step E4), the method then passes to step E5, steps E5 to E7 consisting of determining whether this flow rate increase of the privileged injectors may be suppressed. In other words, during steps E5 to E7, the regulation means 350 determine whether a risk of extinction of the combustion in the combustion chamber 330 is ruled out and they regulate the flow rate of the privileged injectors 344 accordingly. If the flow rate of the privileged injectors 344 is not increased relatively the flow rate of the main injectors 342 (NO at the end of step E5), the instantaneous flow rate regulation step EII in the combustion chamber 330 is completed, the regulation method completes its regulation cycle and starts a subsequent cycle by again beginning from step E1.

(17) The step E5 consists of determining the instantaneous acceleration dNG/dt of the gas generator shaft 320, NG corresponding to the speed of rotation of the gas generator shaft 320. This determination is moreover achieved continuously by measurement means 380, in particular by means of the phonic wheel 322, of the memory and of the computer of the measurement means 380. At the end of step E5, the method switches to step E6.

(18) The step E6 consists of comparing the value of the instantaneous acceleration dNG/dt of the gas generator shaft 320 relatively to a predetermined threshold value A.sub.ref. This step is achieved by the regulation means 350. If the instantaneous acceleration dNG/dt is greater than or equal to the predetermined threshold value A.sub.ref (YES at the end of step E53), the method considers that the increase in the flow rate of the main injectors may be suppressed, and switches to step E7. If the instantaneous acceleration dNG/dt is less than the predetermined threshold value A.sub.ref (NO at the end of step E53), then the method considers that the risk of extinction of the combustion remains so that the fuel flow rate of the privileged injectors remains unchanged. In this case, the step EII for regulating the instantaneous flow rate of the fuel in the combustion chamber 310 is completed, the regulation method completes its regulation cycle and starts a subsequent cycle by again beginning from step E1.

(19) The step E7 consists of suppressing the increase in the fuel flow rate of the privileged injectors 344 so that their flow rate again becomes equal to the flow rate of the main injectors 342. This suppression is gradual, for example over a period of the order of three seconds (3.0 s), in order to avoid unpriming of the privileged injectors. Moreover, in the case when the main injectors would be switched off, their switching on is also gradual. At the end of the step E7, the instantaneous flow rate regulation step EII is completed; the method for regulating the instantaneous fuel flow rate in the combustion chamber 310 completes its regulation cycle and starts a subsequent cycle by again beginning with step E1.

(20) According to an alternative, the regulation means 350 gradually suppress (or according to an alternative, instantaneously) the flow rate increase of the privileged injectors 344 after a time-out delay. For example, this delay is three seconds (3.0 s). With this delay it is possible to avoid that the flow rate of the privileged injectors 344 be brought back to the flow rate under normal operating conditions while the combustion in the combustion chamber 330 may still be unstable and have a risk of extinction. Thus, by timing out the gradual suppression of the flow rate increase of the privileged injectors 344, it is expected that the combustion stabilizes before gradual suppression of the flow rate increase of the privileged injectors 344. The safety of the turbomachine is thus improved. This time-out is achieved for example before or after step E7.

(21) It is understood that in this alternative, the regulation means 350 record the time tn of the command for gradual suppression of the flow rate increase, and actually control the gradual suppression of the flow rate increase in the privileged injectors 344 during a subsequent regulation cycle, at a time tmtn+D (tm greater than or equal to tn plus D), D being the time-out delay, if the speed dXR/dt of the meter is always greater than or equal to the predetermined threshold value V.sub.ref and the acceleration dNG/dt of the gas generator shaft is greater than A.sub.ref.

(22) According to an alternative, the steps E5 and E6 are omitted, and the method directly switches from step E4 to step E7, if the answer is YES to step E4. Of course, gradual suppression of the increase in the flow rate may be timed out, as described above.

(23) According to another alternative, the flow rate of the privileged injectors is increased, or according to an alternative, gradually increased, for a predetermined period in step E3. Thus, in this alternative, the steps E4 to E7 of FIG. 2 are omitted, and the flow rate increase in the privileged injectors is suppressed, or according to an alternative, gradually suppressed, automatically, at the end of a predetermined period. Of course, according to an alternative, a subsequent regulation cycle is carried out for a predetermined period, or according to still another alternative, the subsequent regulation cycle is only carried out when the predetermined period has elapsed.