METHOD OF POGO EFFECT DELETION

专利摘要:
The invention relates to the field of jet powered vehicles and more specifically to a POGO effect suppression method on such a machine (1). A feed system (4) of the jet engine (2) of the machine (1) is equipped with a hydraulic accumulator (8) for selecting between a plurality of predetermined operating stages each corresponding to a different volume of gas. According to this method, if a first reference criterion is not fulfilled by the current stage, a transition of the hydraulic accumulator (8) is preferably carried out at an alternating stage, selected from among alternative stages for which the first criterion reference is filled, and for which no hydraulic resonance frequency intersects any current mechanical resonance frequency during the transition.
公开号:FR3026440A1
申请号:FR1459254
申请日:2014-09-30
公开日:2016-04-01
发明作者:Gonidec Serge Daniel Le；Jeremy Toutin；Alain Kernilis；Olivier Crassous
申请人:SNECMA SAS；
IPC主号:

专利说明:

[0001] BACKGROUND OF THE INVENTION The present invention relates to a method for suppressing the POGO effect on board a craft propelled by at least one jet engine fed with at least one liquid propellant. In this context, it is understood by "jet engine", in particular rocket engines, and by "machine" any vehicle driven or non-driven, but in particular space launchers. In the aerospace field, and more particularly in the case of liquid propellant rockets, the effect name POGO has been given to the resonance input of a liquid propellant in the supply circuit of a jet engine with mechanical oscillations of the machine propelled by the jet engine. Since engine thrust can vary with the propellant flow rate provided by the fuel system, such a resonance input can cause rapidly diverging oscillations, and thus lead to guiding difficulties, and even damage up to 'to the total loss of its payload, or even the vehicle. The name POGO effect does not come from an acronym, but "pogo sticks" or jumping stilts, toys formed by a spring rod whose leaps have reminded technicians violent longitudinal oscillations of rockets caused by this effect. Since the beginning of the development of liquid propellant rockets, it has therefore proved very important to take measures to suppress this POGO effect. In the context of the present description, "suppression" is understood to mean both total suppression and partial reduction. Two main types of POGO effect correcting systems are known to those skilled in the art, passive systems and active systems. With the passive systems, the hydraulic resonance frequencies are changed so that they can not coincide with the mechanical resonance frequencies of the rocket. They can also be amortized. This is done, for example, by installing hydraulic accumulators in the propellant supply circuit. Such a hydraulic accumulator is normally formed by a pressurized volume comprising gas and liquid in communication with the supply circuit. The hydraulic accumulator operates as a mass-spring-damper system, in which the mass is the mass of liquid in the accumulator, the spring is formed by the gas, and the damping comes from the viscosity of the liquid entering and exiting the the accumulator by a restricted conduit. In an equivalent electrical circuit, such a hydraulic accumulator would correspond to a capacitor with a fixed capacitance. The compressibility and damping parameters of such an accumulator are substantially constant, or at least can not be controlled. On the other hand, with the active systems, an oscillation oscillation of pressure-flow in the supply circuit is created, coming to oppose the oscillations measured in the circuit.
[0002] However, both passive systems and active systems have disadvantages. Passive systems are not suitable for rockets with high variability in their mechanical resonant frequencies, since they do not damp modes outside a narrow band around the frequencies for which they have been sized. In the event of a discrepancy between the dynamic forecasts and the actual dynamics of the flight of the rocket, they are not able to correct themselves. As for the active systems, they are likely to have only locally positive effects and can generate negative local or global effects elsewhere.
[0003] To avoid these drawbacks, the international patent application WO 2012/156615 disclosed several POGO effect suppression devices and methods, by which it is possible to vary the hydraulic resonance frequencies in the power system to maintain a distance. with mechanical resonance frequencies throughout the flight of the craft. In particular, this prior document disclosed the use, in a feed system of a jet engine in at least one propellant, of a hydraulic accumulator for selecting between several predetermined operating levels each corresponding to a different volume of gas in the hydraulic accumulator. In a similar electrical circuit, such an electric accumulator would correspond to a variable capacity capacitor between several predetermined levels. However, according to the method disclosed in this document, in some cases, at least one hydraulic resonance frequency can briefly cross a mechanical resonance frequency to pass a first step, which is no longer sufficiently distant from the mechanical resonance frequency at a second stage, sufficiently distant from the mechanical resonance frequency, but situated on the opposite side of the curve of the mechanical resonance frequency. If such a transient and rapid crossing of resonance frequencies can not normally trigger a resonance, they should nevertheless be avoided. OBJECT AND SUMMARY OF THE INVENTION The present invention aims to remedy these drawbacks.
[0004] The aim of the invention is to provide a method that makes it possible to eliminate the POGO effect more effectively by avoiding, to a large extent, the even transient crossing of hydraulic and mechanical resonance frequencies. In at least one embodiment, this object is achieved by virtue of the fact that after the following steps: calculation of a current hydraulic resonance frequency for each mode of a set of hydraulic resonance modes of said feed system with a current stage of said accumulator among said predetermined levels; calculating an alternating hydraulic resonance frequency for each mode of said set of hydraulic resonance modes of said supply system with each bearing of the predetermined bearings alternating with the current stage; and calculating a current difference between each current hydraulic resonance frequency and a current mechanical resonance frequency for each mode of a set of mechanical resonance modes of a structure of said machine; if a first reference criterion is not fulfilled by all the current differences, a set of differences between each alternating hydraulic resonance frequency 30 and each current mechanical resonance frequency is calculated for each alternative level and, if said first criterion reference is filled by each set of differences of a plurality of alternative bearings, a transition of the current bearing hydraulic accumulator to an alternating bearing selected from said alternative stages for which the first reference criterion is completed is controlled , and for which no hydraulic resonance frequency crosses any current mechanical resonance frequency during the transition. In the present context, we mean "together" in a broad sense, covering not only a plurality, but also a unitary whole. Thanks to these arrangements, if the hydraulic accumulator offers at least one alternative bearing fulfilling the first reference criterion and can be reached without frequency crossing, it is this step that will be selected, thus avoiding a crossover presenting a risk even reduced. 10 of resonance input. In some cases, it may also prove that the first reference criterion is fulfilled by each set of differences of a plurality of alternative steps that can be achieved without any frequency crossing. In these cases, said transition could be controlled to an alternating stage, selected from those for which the first reference criterion is filled and to which the transition does not involve any frequency crossing, for which a comparative parameter, calculated as a function of the set of corresponding differences, has a maximum value, thus allowing further optimization of the choice of the alternative bearing towards which the transition will take place. This comparative parameter can be, for example, the minimum difference among said set of differences, the sum of said set of differences, or the modulus of a vector whose components would be said set of differences. Even with this comparative parameter, it may be that the first reference criterion is satisfied by each set of differences of a plurality of alternative steps that can be achieved without any frequency crossing and whose comparative parameter has the same maximum value. . In this case, it would still be possible to separate these alternative bearings using a predetermined order of preference and thus controlling the transition to an alternative bearing having a maximum rank in a predetermined order, among those for which the first reference criterion is fulfilled. , to which the transition involves no frequency crossover, and having the same maximum value of the comparative parameter.
[0005] Alternatively, it may also prove that the first reference criterion is not filled by all the current differences but is filled by the set of differences for a single alternative level. In this case, a transition of the hydraulic accumulator could be controlled to the single alternative bearing completely fulfilling the first reference criterion. Said first reference criterion may be that each of the differences of said set of differences is greater than a predetermined threshold. It may also prove that said first reference criterion is not fulfilled for any level, current or alternative, but that a second, less restrictive reference criterion is fulfilled for a set of alternative levels. In this case, a transition of the hydraulic accumulator could be controlled to an alternating bearing, selected from the set of alternative bearings for which the second reference criterion is filled, for which a comparative parameter, calculated according to the set of corresponding differences, presents a maximum value. As in the case previously mentioned, this comparative parameter could be, for example, the minimum difference among said set of differences, the sum of said set of differences, or the modulus of a vector whose components would be said set of differences. Said second reference criterion may be that each of the differences of said set of differences is greater than a predetermined threshold, which could be a fraction of the threshold corresponding to the first criterion. Finally, it may also prove that none of the said first or second reference criteria is fulfilled for any level, current or alternative. In this case, an alternating transition could be controlled between at least two of these bearings, current and alternating, so as to avoid a too prolonged proximity in time of the same hydraulic resonance frequency and mechanical resonance frequency pairs, proximity being able to trigger resonance phenomena. If said first reference criterion is fulfilled by each set of differences of a plurality of alternative bearings, it can be determined that during the transition of the current bearing hydraulic accumulator to a selected alternate one of said alternative stages for which the first reference criterion is fulfilled, no hydraulic resonance frequency will intersect any current mechanical resonance frequency, first determining, for each mode of said set of hydraulic resonance modes, a minimum hydraulic resonance frequency and a resonance frequency of the hydraulic resonance frequency for the current capacity and the hydraulic resonance frequency for the selected alternate bearing, and then comparing, for each mode of said set of hydraulic resonance modes, the minimum hydraulic resonance frequency and the frequency hy resonance maximum hydraulics with the current mechanical resonance frequency for each mechanical resonance mode of said set of mechanical resonance modes, wherein no hydraulic resonance frequency can cross any current mechanical resonance frequency during the transition to the selected alternate stage if, for any of said modes hydraulic and mechanical resonance frequency, the minimum hydraulic resonance frequency is lower than the mechanical resonance frequency and the maximum hydraulic resonance frequency is greater than the mechanical resonance frequency.
[0006] The present disclosure also relates to a machine comprising at least one jet engine, and a system for supplying said engine with at least one liquid propellant, said supply system being equipped with a hydraulic accumulator, making it possible to select between several stages of predetermined operation each corresponding to a different volume of gas in the hydraulic accumulator, and a control unit configured to perform the abovementioned POGO effect suppression method. Furthermore, the control unit may be a programmable control unit, and this disclosure therefore also relates to a computer program for implementing this POGO effect deletion method, as well as a data storage medium containing such a device. program readable by an electronic data processing unit, and an electronic data processing unit programmed to implement this method. The term "data storage medium" also means any form of memory, alive or dead, which may contain data in computer-readable form, including optical, magnetic and / or electronic media. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which: - Figure 1 is a diagram, constructed by means of the hydraulic-electrical analogy, of a rocket motor vehicle with a liquid propellant supply system according to a method of embodiment of the invention; FIGS. 2A and 2B show cross-sections of a hydraulic accumulator with a variable gas volume installed as a bypass of a supply circuit of the system of FIG. 1; FIGS. 3A and 3B are graphs illustrating the evolution of the volume of gas and the hydraulic resonance frequencies of the feed system of FIG. 1 following the passage of the hydraulic accumulator FIG. 2 by several level levels; FIG. 4 illustrates the crossing of a hydraulic resonance frequency with a mechanical resonance frequency during the transition from one of said bearings to another; - Figure 5 is a block diagram of a control unit of the hydraulic accumulator; FIG. 6 is a flowchart illustrating a frequency crossing detection algorithm; and FIGS. 7 and 8 are flowcharts illustrating, respectively, a first and a second portion of an algorithm governing a POGO effect deletion method. DETAILED DESCRIPTION OF THE INVENTION Apparatus 1 shown in FIG. 1 comprises a jet engine 2 incorporating a combustion chamber and a convergent-divergent nozzle. The machine 1 also comprises a feed system 3, 4 for each of two liquid and chemically reactive propellants feeding this jet engine 2. The first feed system 3 is illustrated only partially. Each supply system 3, 4 filled with fluid represents a dynamic system that can be modeled as an electrical circuit having resistors 5, inductances 6 and capacitances 7 and which normally has several modes of hydraulic resonance, each with a resonant frequency hydraulic fh. In order to vary at least one resonant frequency of the second supply circuit 4, it comprises, as a bypass of the circuit, a hydraulic accumulator 8 with a variable gas volume, and therefore with variable compressibility. This accumulator 8, illustrated in FIGS. 2a and 2b, comprises a reservoir 9 with, on one side, a point 10 for supplying gas under pressure, and on an opposite side, a connection 11 to a conduit 15 of the second supply circuit 4. At different levels between the point 10 and the connection 11, plunger tubes 12a to 12d connect the reservoir 9 with the conduit 15. In each plunger tube 12a to 12d, a valve 14a to 14d is interposed The valves 14a to 14d are all connected to a control unit 30 to control their opening and closing. The opening and closing of the valves 14a to 14d make it possible to vary the level of liquid, and therefore the volume of gas 17, in the reservoir 9, as illustrated in FIGS. 2a and 2b. In FIG. 2a, the valve 14a of the shorter plunger tube 12a is open, while the valves 14b to 14d of the other plunger tubes 12b to 12d are closed. The free surface of the liquid is thus stabilized at the inlet of the plunger tube 12a, and the volume of gas 17 as well as the compressibility thus remain comparatively limited. In FIG. 2b, however, the valve 14a of the plunger tube 12a is closed, and the valve 14b of the next plunger tube 12b is open. The free surface of the liquid is thus stabilized at the lower level of the inlet of the plunger tube 12b, and the volume of gas 17 and the compressibility increase accordingly. The capacity of the hydraulic accumulator 8 can be further increased in consecutive steps by opening the other valves 14c and 14d.
[0007] The structure of the machine 1 can normally vibrate in a plurality of mechanical resonance modes, each associated with a mechanical resonance frequency fm. In flight, these frequencies of mechanical resonance fm evolve over time, in particular because of the progressive emptying of propellant reservoirs used to feed the combustion chamber 2. Even if the frequencies of hydraulic resonance fh and the frequencies of mechanical resonance fm are initially quite distant from each other to avoid the POGO effect, in certain circumstances the evolution of mechanical resonance frequencies fm could bring them closer to the frequencies of hydraulic resonance fh until triggering this effect, if they remained unchanged. As the four plunger tubes 14a to 14d make it possible to choose an operating bearing from a set of four predetermined levels each corresponding to a different volume of gas in the accumulator 8, and to move from one to the other of the levels of this assembly, it therefore becomes possible to adapt, even during the operation of the rocket engine of the machine 1, the hydraulic resonance frequencies fh of the different hydraulic resonance modes of the second feed circuit 4, so as to prevent at least one of them coincides with a time-variable mechanical resonance frequency fm of a mechanical resonance mode of the structure of the machine 1. FIG. 3A illustrates the evolution of the volume of gas V in FIG. the accumulator 8 following the passage through several successive stages of the level of the free liquid surface in the accumulator 8. FIG. 3B illustrates the evolution of the hydraulic resonance frequencies fh (in Hertz) corres The first three hydraulic resonance modes of the second power supply circuit 4 can be evaluated. It is possible to appreciate how each of these hydraulic resonance frequencies fh also decreases in steps concurrently with the stepwise increase in the capacity of the accumulator 8. Under certain circumstances, during a transition of the hydraulic accumulator 8 from a current bearing to an alternative bearing from the set of predetermined levels, this transition is intended to increase the distance between the hydraulic resonance frequencies fh and the frequencies mechanical resonance fm, at least one of the hydraulic resonance frequencies fh can momentarily cross at least one of the mechanical resonance frequencies fm, as illustrated in FIG. 4. Although the coincidence between the hydraulic and the mechanical resonance frequencies is then only transient, which limits the risk of triggering POGO effects, it is generally necessary to avoid these crossings. The control unit 30 may especially be a data processing unit configured and / or programmed to implement the POGO effect suppression method. In particular, the control unit 30 may comprise a RAM or dead memory in which is recorded a series of instructions, that is to say a program, for this implementation. Fig. 5 is a block diagram of the control unit 30, illustrating it as a set of interconnected functional modules. Thus, this control unit 30 comprises a first calculation module F1 for calculating, from physical parameters provided by sensors 31 and / or estimated through at least one model of the machine 1, and for each mode of measurement. resonance of a set of hydraulic resonance modes and mechanical resonance modes: the hydraulic resonance frequency fh (0, n) of the supply system 4 corresponding to the current stage, that is to say with the volume current gas of the accumulator 8, for each resonance mode n of a set of N hydraulic resonance modes; the current mechanical resonance frequency fm (p) of the structure of the vehicle 1 for each resonance mode p of a set of P mechanical resonance modes; the hydraulic resonance frequencies fh (x, n) of the supply system 4 corresponding to each level x of the other X levels available, that is to say with each of the alternating levels of the accumulator 8, among the set of predetermined levels, for the same resonance mode n among the set N of the hydraulic resonance modes. Optionally, the first calculation module F1 can also calculate uncertainty intervals for each of these frequencies.
[0008] The control unit 30 also includes a decision module F2 for controlling a step change based on the values calculated by the first calculation module F1. As illustrated in FIG. 5, this decision module F2 can in turn be decomposed into several other functional modules, including a second calculation module F21 for calculating the differences DIFF (0, n, p) between each current hydraulic resonance frequency. fh (0, n) and each current mechanical resonance frequency fm (p) a third calculation module F22 for calculating the differences DIFF (x, n, p) between each alternative hydraulic resonance frequency fh (x, n) and each current mechanical resonance frequency fm (p), a frequency crossing detection module F24, a current bearing change detection module F25 and a bearing selection module F26. For the calculation of the current differences DIFF (0, n, p) and alternatives DIFF (x, n, p) for each hydraulic resonance mode n and each mechanical resonance mode p, the second and third calculation modules F21, F22 can take into account the intervals of uncertainty possibly provided by the first calculation module F1. The frequency crossing detection module F24 is designed to determine for which transitions, among the set of potential transitions from the current stage, to the different alternating stages of the hydraulic accumulator 8, none of the hydraulic frequencies fh would cross none of the mechanical frequencies fm. For this, in this frequency crossing detection module F24, the following algorithm, illustrated by the flow chart of FIG. 6, is implemented: Following the departure S600 of this algorithm, the counters x and n are initialized, each with the value 1, in the corresponding steps S601 and S602. In step 5603, the current hydraulic resonance frequency fh (0, n) is compared to the alternative hydraulic resonance frequency fh (x, n) for the same hydraulic resonance mode n. If the current hydraulic resonance frequency fh (0, n) is greater than the alternating hydraulic resonance frequency fh (x, n), the current hydraulic resonance frequency fh (0, n) is recorded in step S604 as the upper frequency fhrnax and the alternating hydraulic resonance frequency fh (x, n) as the lower frequency fhmin. On the other hand, if the current hydraulic resonance frequency fh (0, n) is not greater than the alternating hydraulic resonance frequency fh (x, n), the current hydraulic resonance frequency is recorded in step S605 fh (0, n) as the lower frequency fhmin and the alternating hydraulic resonance frequency fh (x, n) as the upper frequency fhmax.
[0009] Once the lower and upper frequencies fhmin and fhmax are thus recorded, the counter p is initialized, with the value 1, in the step S606. Then, in step S607, the current mechanical resonance frequency fm (p) is compared to said lower and upper frequencies fhmin and fhmax, to determine if the current mechanical resonance frequency fm (p) is lower than the upper frequency fhmax and greater than the lower frequency fhmin. In the opposite case, in step S608, the value of the counter p is compared with its maximum value P, that is to say with the number P of mechanical resonance modes to be taken into account in this algorithm. If this value P is not reached, in step S609 a unit is added to the counter p and a loop is returned to step 5607 to compare the mechanical resonance frequency for the mode with the lower and upper frequencies fhmin and fhmax. mechanical resonance. If, on the other hand, the maximum value P of the counter p is reached, in step S610 the counter n is compared to its maximum value N, ie to the number N of the hydraulic resonance modes. take into account in this algorithm. If this value N is not reached, in step S611 a unit is added to the counter n and loopback is returned to step S603 to determine the lower and upper frequencies for the next hydraulic resonance mode and then compare them. at mechanical resonance frequencies. If, on the other hand, the maximum value N of the counter n is reached without the comparison of the step S607 having given a positive result for any of the N hydraulic resonance modes and none of the P mechanical resonance modes, a value is recorded. zero for a binary signal CRITX (x) in step S612, indicating in this manner that the alternate bearing x can be reached from the current stage without any frequency crossing. On the other hand, if in step S607 the comparison of the present mechanical resonance frequency fm (p) with said lower and upper frequencies fhmin and fhmax gives a positive result, a step S613 is directly recorded. value 1 for the binary signal CRITX (x), without continuing the loops corresponding to the counters n and p. After either step S612 or step S613, the value of counter x is compared to its maximum value X in step S614. It is thus determined whether each of the X alternative steps has been verified. In the opposite case, a unit is added to the value of the counter X in the step S615, and the initialization step of the counter n is returned to the step S602. On the other hand, if the maximum value X is reached by the counter x, we proceed to the end S616 of the frequency crossing detection algorithm. The current step change detection module F25 is configured to detect whether a step transition is currently in progress and generates a CRITT bit signal with a zero value if no transition is in progress and a value of 1 if such a transition is well underway. For this, the module F25 can for example be based, as illustrated, on a comparison between the values of the current hydraulic resonance frequencies fh (0, n), calculated by the module Fi, and hydraulic resonance frequencies fhc (n) corresponding to the bearing currently selected by the bearing selection module F26 for the same hydraulic resonance modes n. The value of the CRITT signal will then change from zero to one as soon as the differences between the values of the current hydraulic resonance frequencies fh (0, n) and those of the hydraulic resonance frequencies fhc (n) corresponding to the level currently selected for the same modes. hydraulic resonance n will exceed a threshold of uncertainty, and will return to zero as soon as these differences return below this threshold of uncertainty, or a threshold of time since the beginning of the transition has been exceeded. Alternatively, however, the determination of such a transient state of change of bearing can be carried out in other ways, as for example on the basis of time gradients in the current hydraulic resonance frequencies fh (0, n), by observation of the valves 14a to 14d or their control signals, or by observation of the liquid level in the accumulator 8. The bearing selection module F26 is configured to select an operating level among the X alternating stages and order the transition of the 8 hydraulic accumulator to this alternative bearing according to the algorithm illustrated in Figures 7 and 8, from the CRITT signal transmitted by the step change detection module F25, CRITX (x) signals transmitted by the detection module F24 frequency crossing and current differences DIFF (0, n, p) and alternatives DIFF (x, n, p) calculated by the second and third calculation modules F21 and F22. Following the departure S700 of this algorithm, it is first checked in step S701 if a first reference criterion is already not filled by the current stage. In the illustrated embodiment, this first reference criterion is a distance D (0) between the set of current hydraulic resonance frequencies fh (0, n) and the set of mechanical resonance frequencies fm (p) is greater than a first threshold Dmin1. This distance D (0) can for example be calculated as being the smallest difference DIFF (0, n, p). If the current stage fulfills this first reference criterion, no step transition is necessary and the algorithm is immediately interrupted, proceeding to finalization S702. On the other hand, if the current stage does not fulfill this first reference criterion, in step S703 it is proceeded to verify that the value of the signal CRITT, indicating a step transition in progress, is not equal to 1. If the CRITT signal indicates a transition in progress, the algorithm is also interrupted, going to the finalization step S702. On the other hand, if the value of the binary signal CRITT is zero, we go to the initialization step S704, in which the counters i, j and k are initialized with a zero value, the value of a parameter DMAX is initialized with the value of the distance D (0), and the counter x is initialized with a value of 1. Then, in the step S705, it proceeds to check whether the first reference criterion is filled by the alternative bearing x, c ' that is, if the distance D (x), computed in the same way as the distance D (0), but based on the alternative differences Af (x, n, p) corresponding to the level x, is greater than the first threshold Drnin1.
[0010] If this first reference criterion is not fulfilled by the alternating step x, in step S706 a zero value is assigned to the binary signal CRIT1 (x), before checking in step S707 whether the step x fulfills at least a second, less restrictive benchmark. In the illustrated embodiment, this second reference criterion is that the value of the distance D (x) is at least greater than a second threshold Dmin2 less than the first threshold. However, alternative criteria may also be considered for this second benchmark. If this second reference criterion is also not satisfied by the alternate level x, a zero value is assigned to the binary signal CRIT2 (x) and step S709, in which the value of the counter x is checked. is already equal to the number X of alternative levels. If it is not yet the case, a unit is added to the counter x in the step S710 and is looped back to the step S705. Alternatively, if the second reference criterion has been fulfilled in step S707, in step S711 the value 1 is assigned to the signal CRIT2 (x) for step x and one unit is added to the counter j. Then, in step S712 it is checked whether the counter k is still at zero and whether the distance D (x) is greater than the value assigned to the parameter DMAX. If both conditions are met, in step S713 the value of the distance D (x) for step x is assigned to this parameter DMAX before proceeding to step S709. Otherwise, go directly to step S709. If the first reference criterion is filled by the alternate step x in step S705, in step S714 a value of 1 is assigned to the signal CRIT1 (x) and one unit is added to the counter i. Then, in step S715, it is verified through the value of the signal CRITX (x) that a transition to the alternating stage x is possible without crossing frequencies. If the value of the signal CRITX (x) is not zero, which indicates that the transition to the alternate bearing x involves at least one frequency crossing, proceed to the step S712 previously described. On the other hand, if in step S715 it is verified that the value of the signal CRrrX (x) is indeed zero, thus indicating that a transition to the alternating stage x is possible without frequency crossing, it is verified in step S716 if the value of the counter k is still equal to zero or the distance D (x) greater than the value of the comparative parameter DMAX. If at least one of these two conditions is fulfilled, thus indicating that this alternative bearing x is either the first towards which the transition can be carried out without crossing frequencies, or the one presenting for the moment the highest distance D (x). among those to which it has already been verified that the transition can be carried out without crossing frequencies, in step S717 the value of the distance D (x) is assigned to the parameter DMAX, before going on to step S718 in which one adds a unit to the counter k, to then go to the step S709 previously described. On the other hand, if none of the conditions verified in step S716 are fulfilled, step S718 is directly passed without going through step S717. Thus, at each loop between the steps S705 and S709, if an alternative bearing x fulfills the condition CRITX (x) = 0, according to which the transition is possible without crossing frequencies, the value of the corresponding distance D (x) is assigned. in step S716 to the parameter DMAX if the first comparative criterion is satisfied and the value of the counter k is zero or the value of the distance D (x) greater than the previous value of the parameter DMAX, while if an alternative step x does not fulfill the condition CRITX (x) = 0, the value of the corresponding distance D (x) is assigned to the parameter DMAX in step S713 only if the first or at least the second reference criterion is fulfilled, that the value of the corresponding distance D (x) is greater than the previous value of the parameter DMAX and the counter k is still zero, which means that no alternative bearing x has yet fulfilled the condition CRITX (x) = 0. Consequently, at the end of this first part of the algorithm, when the condition of the step 5709 is finally fulfilled and all the X alternative stages have therefore been taken into consideration, the value of the parameter DMAX will correspond either to that of the greater of the distances D (x) among the set of alternative bearings filling the first (and therefore also the second) criterion of reference as well as the condition CRITX (x) = 0, and therefore accessible without crossing frequencies, ie at that of the greatest of the distances D (x) among the set of alternative bearings fulfilling at least one of the first and second reference criteria and the distance D (0) corresponding to the current stage, if none of the alternative levels fills the first I [CDNRI] criterion of reference and the condition CRITX (x) = 0. The second part of the algorithm implemented by the bearing selection module F26 is illustrated in FIG. 8. If in step S709 it has been verified that it has already reached the last of the X alternative stages, the state of the counter i is checked in steps S801 and S802. If in these steps S801 and S802 it is verified that the value of the counter i is, respectively, greater than zero and one, thus indicating that a plurality of the alternative steps fills the first reference criterion, the condition is checked. counter k in steps S803 and S804. If in these steps S803 and S804 it is verified that the value of the counter k is, respectively, greater than zero and one, thus indicating that several alternative stages, among those fulfilling the first reference criterion, can be reached without frequency crossing. it is verified in step S805 whether the value of the distance D (x) is equal to that of the parameter DMAX for more than one alternative step x for which the value of the signal CRITX (x) is zero. If this is the case, in step S806 the selection module F26 selects, among the plurality of alternative stages x for which D (x) = DMAX and CRITX (x) = 0, that having the rank 10 the highest in a predetermined order, and proceeds to control the transition to this selected step, then proceed to the finalization S807 of the algorithm. On the other hand, if in step S805 it was found that the value of the distance D (x) was equal to that assigned to the parameter DMAX only for a single alternative step x among those for which the value of the signal CRITX (x) was zero, or in step S804 it was found that the value of the counter k is not greater than one, which implies that a single alternate bearing x fulfills the condition CRITX (x) = 0 and thus also D (x) = DMAX, in the step 5808 the module F26 proceeds to control the transition to the only alternative bearing x fulfilling the two conditions D (x) = DMAX and CRID ((x) = 0, for then proceed further with the finalization S807. On the other hand, if in step S802 it has been found that the value of the counter i is not greater than unity, which indicates that a single alternative step x fulfills the first criterion of reference, in step S809 the module F26 proceeds to control the transition to the single alternate level x filling this co ndition CRIT1 (x) = 1, then proceed to the finalization S807. The comparative parameter, i.e., the distance D (x) in the illustrated embodiment, and the predetermined order of the alternate bearings x 30 may also be used to separate several alternative bearings x filling the first or the second reference criterion when none is accessible without frequency crossing. Thus, if in step S802 it has been found that the value of the counter i is greater than unity, which indicates that several alternative steps x satisfy the first criterion of reference, but that in step 5803 it has It has been found that the value of the counter k has remained zero, which indicates that none of these alternative levels x can be reached without crossing frequencies, we proceed to the step S810, in which it is checked if more than one alternate bearing x has a distance D (x) equal to that assigned to parameter DMAX. In the affirmative case, in step S811, the module F26 proceeds to control the transition of the accumulator 8 to the alternating stage x with a distance D (x) equal to the value of the parameter DMAX and higher rank, and then proceed to the finalization S807. In a negative case, in step S812, the module F26 proceeds to control the transition of the accumulator 8 to the only alternative stage x whose value of the distance D (x) is therefore equal to the value of the parameter DMAX, for then proceed with finalization S807. Step S810 is also reached if in step S801 it has been found that the value of the counter i has remained zero, which indicates that no alternative step x does not fulfill the first reference criterion, and refers to a first mode degraded operation, but that in the next step S813 it is found that the value of the counter j is not zero, which means that at least one alternative step x fulfills the second reference criterion, and that thereafter it is found in step S814 that the distance D (0) corresponding to the current step is less than the value of the parameter DMAX, corresponding to the greater of the distances D (x) among the alternate levels x. On the other hand, if in step S814 it is found that the distance D (0) corresponding to the current step is not less than the value of the parameter DMAX after the first part of this algorithm, or if in step S813 it has been found that the value of the counter j has remained zero, and that no alternative stage thus fulfills even the second reference criterion and that it is then noted in the step S815 that the current stage fulfills this second criterion well. reference criterion, the module F26 then goes directly to the finalization S807 of the algorithm without controlling any step transition.
[0011] Finally, if in step S815 it has been found that the current step also does not fulfill the second reference criterion, the module F26 is returned to a second degraded operating mode, in which, in step S816, it controls a rapidly alternating transition between at least two different stages to try to avoid further triggering of the POGO effect despite the proximity of the hydraulic and mechanical resonance frequencies.
[0012] Although the present invention has been described with reference to a specific exemplary embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In addition, individual features of the various embodiments mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

权利要求:
Claims (10)
[0001]
REVENDICATIONS1. A method for suppressing POGO effect on a machine (1) comprising at least one jet engine (2) and a feed system (4) of said engine (2) in at least one liquid propellant, said fuel system being equipped with a hydraulic accumulator (8) for selecting between a plurality of predetermined operating stages each corresponding to a different volume of gas in the hydraulic accumulator (8), the method comprising the steps of: calculating a current hydraulic resonance frequency for each mode of a set of hydraulic resonance modes of said power system (4) with a current stage of said accumulator (8) among said predetermined stages; calculating an alternating hydraulic resonance frequency for each mode of said set of hydraulic resonance modes of said supply system (4) with each bearing of the predetermined bearings alternating with the current bearing; calculating a current difference between each current hydraulic resonance frequency and a current mechanical resonance frequency for each mode of a set of mechanical resonance modes of a structure of said machine and, if a first reference criterion is not satisfied by all present differences: calculating a set of differences between each alternating hydraulic resonance frequency and each current mechanical resonance frequency for each alternative level and, if said first reference criterion is fulfilled by each set of differences of a plurality of alternative bearings: controlling a transition of the hydraulic accumulator (8) of the current bearing to an alternating bearing, selected from among said alternative bearings for which the first reference criterion is filled, and for which no hydraulic resonance frequency crosses any frequency mechanical resonance during the transition.
[0002]
A POGO effect suppression method according to claim 1, wherein, if the hydraulic accumulator (8) is able to move from the current stage to any one of several alternative stages, among those for which the first reference criterion is filled, without any hydraulic resonance frequency intersecting any current mechanical resonance frequency during the transition, said transition is controlled to an alternate bearing, selected from those for which the first reference criterion is filled and to which the transition implies no frequency crossing, and for which a comparative parameter, calculated as a function of the corresponding set of differences, has a maximum value. 10
[0003]
A POGO effect suppression method according to claim 2, wherein, if a plurality of alternative stages, among those for which the first reference criterion is fulfilled and to which the transition involves no frequency crossing, exhibit a same maximum value of said comparative parameter, said transition is controlled to an alternative bearing having a maximum rank in a predetermined order, among those for which the first reference criterion is filled, to which the transition involves no frequency crossing, and having the same maximum value of the comparative parameter. 20
[0004]
A POGO effect suppression method according to any one of the preceding claims, wherein, if the first reference criterion is not filled by the set of current differences but is filled by the set of differences for a Only one alternative bearing, a transition of the hydraulic accumulator (8) is controlled to the only 25 alternative bearing completely complete the first criterion of reference.
[0005]
A POGO effect suppression method as claimed in any one of the preceding claims, wherein said first reference criterion is that each of the differences of said set of differences is greater than a predetermined threshold. 30
[0006]
A POGO effect suppression method according to any one of the preceding claims, comprising, if said first reference criterion is not fulfilled for any step, current or alternative, but a second reference criterion is fulfilled for a set of alternating bearings, a transition of the hydraulic accumulator (8) is controlled to an alternating bearing, selected from the set of alternative bearings for which the second reference criterion is filled, and for which a comparative parameter, calculated in function of the set of corresponding differences, presents a maximum value.
[0007]
A POGO effect suppression method according to claim 5, wherein, if none of said first or second reference criterion is fulfilled for any current or alternate stage, an alternating transition is controlled between at least two of the steps ongoing and alternative.
[0008]
The POGO effect suppression method according to any one of claims 1 to 7, wherein said second reference criterion is that each of the differences of said set of differences is greater than a predetermined threshold.
[0009]
A POGO effect suppression method as claimed in any one of the preceding claims, wherein, if said first reference criterion is filled by each set of differences of a plurality of alternative steps, it is determined that during the transition of the hydraulic accumulator (8) of the current bearing at an alternative bearing selected from said alternative bearings for which the first reference criterion is filled, no hydraulic resonance frequency will intersect any current mechanical resonance frequency according to the following steps: determining for each mode of said set of hydraulic resonance modes, a minimum hydraulic resonance frequency and a maximum hydraulic resonance frequency among the hydraulic resonance frequency for the current bearing and the hydraulic resonance frequency for the selected alternate bearing, compare, for each mode of said mode set s of hydraulic resonance, the minimum hydraulic resonance frequency and the maximum hydraulic resonance frequency with the current mechanical resonance frequency for each mechanical resonance mode of said set of mechanical resonance modes, no hydraulic resonance frequency being able to cross any frequency present mechanical resonance during the transition to the selected alternate bearing if, for any of said modes of hydraulic and mechanical resonance, the minimum hydraulic resonance frequency is lower than the mechanical resonance frequency and the maximum hydraulic resonance frequency is greater than the frequency of mechanical resonance.
[0010]
10. Engine (1) comprising at least: a jet engine (2), and a feed system (4) of said engine (2) in at least one liquid propellant, said feed system (4) being equipped with a hydraulic accumulator (8) for selecting between a plurality of predetermined operating steps each corresponding to a different volume of gas in the hydraulic accumulator (8), and a control unit (30) configured to perform a method of POGO effect suppression according to one of the preceding claims.

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JP2017534792A|2017-11-24|

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FR3026440B1|2016-10-14|

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US10914268B2|2021-02-09|

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RU2017114730A|2018-11-02|

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法律状态:
2015-09-11| PLFP| Fee payment|Year of fee payment: 2 |

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2016-04-01| PLSC| Search report ready|Effective date: 20160401 |

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2016-09-14| PLFP| Fee payment|Year of fee payment: 3 |

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2018-09-24| PLFP| Fee payment|Year of fee payment: 5 |

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2020-10-16| ST| Notification of lapse|Effective date: 20200905 |

优先权:

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申请号 | 申请日 | 专利标题

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FR1459254A|FR3026440B1|2014-09-30|2014-09-30|METHOD OF POGO EFFECT DELETION|FR1459254A| FR3026440B1|2014-09-30|2014-09-30|METHOD OF POGO EFFECT DELETION|

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JP2017517255A| JP2017534792A|2014-09-30|2015-09-21|How to suppress the pogo effect|

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PCT/FR2015/052520| WO2016051047A1|2014-09-30|2015-09-21|Method for eliminating the pogo effect|

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EP15778367.1A| EP3201460B1|2014-09-30|2015-09-21|Method for avoiding the pogo effect|

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RU2017114730A| RU2017114730A|2014-09-30|2015-09-21|POGO EFFECT METHOD|

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CN201580052756.3A| CN107110069A|2014-09-30|2015-09-21|Method for eliminating extensional vibration effect|

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US15/515,423| US10914268B2|2014-09-30|2015-09-21|Method for suppressing the pogo effect|