Regulated three-engined power plant for a rotary wing aircraft

Abstract

A power plant (1) having two engine groups (10, 20) and a main gearbox (MGB) (2), and a rotary wing aircraft (30) having such a power plant (1). Each engine group (10, 20) drives said MGB (2) mechanically to rotate a main outlet shaft (3) and, consequently, a main rotor (31) of said aircraft (30) at a frequency of rotation NR. A first engine group (10) has two main engines (11, 12) and is by a first setpoint NR* for said frequency of rotation NR, while a second engine group (20) has one secondary engine (21) and is regulated by a second setpoint W.sub.1* for power from said second engine group (20). The first engine group (10) is also regulated by a third setpoint W.sub.2f* for anticipating power such that said first engine group (10) and said second engine group (20) deliver the power needed at said main rotor (31).

Claims

1. A power plant comprising two engine groups and a main gearbox (MGB), the two engine groups driving the MGB mechanically in order to rotate a main outlet shaft of the MGB, the main outlet shaft having a frequency of rotation NR, wherein a first engine group comprises at least one main engine and a first regulator device, the first regulator device regulating operation of each main engine in application of a first setpoint NR* for the frequency of rotation NR of the main outlet shaft, and in that a second engine group comprises at least one secondary engine and a second regulator device, the second regulator device regulating power delivered by each secondary engine in application of a second setpoint W.sub.1* for the power to be delivered from the second engine group, the power plant having a third regulator device regulating operation of the first engine group in application of a third setpoint W.sub.2f* for anticipating power to be delivered by the first engine group such that the first engine group and the second engine group together provide a necessary power Ws* needed at the main outlet shaft.

2. The power plant according to claim 1, wherein the second regulator device includes at least one filter.

3. The power plant according to claim 2, wherein the third setpoint W.sub.2f* for anticipating power is such that W.sub.2f*=W.sub.2*+H.Math.(W.sub.1*W.sub.1), (W.sub.1*W.sub.1) being a difference between the power W.sub.1, actually delivered by the second engine group and the second setpoint W.sub.1*, and where H.Math.(W.sub.1*W.sub.1) is a difference filtered by the at least one filter.

4. The power plant according to claim 1, wherein the first engine group comprises two identical main engines.

5. The power plant according to claim 1, wherein the second setpoint W.sub.1* for power is determined so as to optimize specific consumption of each engine of each of the engine groups.

6. The power plant according to claim 1, wherein the second setpoint W.sub.1* for power is determined in order to optimize maintenance of each engine of each of the engine groups.

7. The power plant according to claim 1, wherein the second setpoint W.sub.1* for power is determined so as to optimize performance of each engine of each of the engine groups if at least one of the engines fails.

8. The power plant according to claim 1, wherein the first regulator device includes at least one main computer, each main computer being connected to a single main engine, and the second regulator device includes at least one secondary computer, each secondary computer being connected to a single secondary engine.

9. The power plant according to claim 1, wherein each secondary engine is a turboshaft engine provided having a gas generator, and the second setpoint W.sub.1* for power is transformed into a fifth setpoint N.sub.1* for the frequency of rotation of the gas generator, the second regulator device being configured to transform the second setpoint W.sub.1* for power into the fifth setpoint N.sub.1* for frequency of rotation of the gas generator.

10. The power plant according to claim 1, wherein the at least one main engine of the first engine group is two main engines and the at least one secondary engine of the second engine group is one secondary engine.

11. A power plant comprising two engine groups and a main gearbox (MGB) and a calculator for determining a necessary power Ws* needed at a main outlet shaft of the MGB, the two engine groups driving the MGB mechanically in order to rotate the main outlet shaft of the MGB, the main outlet shaft having a frequency of rotation NR, wherein a first engine group comprises at least one main engine and a first regulator device, the first regulator device regulating operation of each main engine in application of a first setpoint NR* for the frequency of rotation NR of the main outlet shaft, and in that a second engine group comprises at least one secondary engine and a second regulator device, the second regulator device regulating power delivered by each secondary engine in application of a second setpoint W.sub.1* for the power to be delivered from the second engine group, the power plant having a third regulator device regulating operation of the first engine group in application of a third setpoint W.sub.2f* for anticipating power to be delivered by the first engine group such that the first engine group and the second engine group together provide the necessary power Ws* needed at the main outlet shaft, wherein the calculator for determining the necessary power Ws* needed at the main outlet shaft of the MGB is configured to determine the necessary power Ws* needed at the main outlet shaft by anticipation of needs for torque and/or power at the main outlet shaft.

12. A method of regulating a power plant for a rotary wing aircraft, the power plant comprising a first engine group, a second engine group, and a main gearbox (MGB), the first and second engine groups driving the MGB mechanically in order to rotate a main outlet shaft of the MGB, the main outlet shaft having a frequency of rotation NR and being constrained to rotate with a main rotor of the aircraft, the method comprising the following steps: determining a necessary power Ws* needed at the main outlet shaft and a first setpoint NR* for the frequency of rotation NR of the main outlet shaft; determining a second setpoint W.sub.1* for power to be delivered by the second engine group; regulating the first engine group having at least one main engine in application of the first setpoint NR* for the frequency of rotation NR; regulating the power delivered by the second engine group having at least one secondary engine in application of the second setpoint W.sub.1* for power; determining a third setpoint W.sub.2f* for anticipating power to be delivered by the first engine group; and regulating the operation of the first engine group in application of the third setpoint W.sub.2f* for anticipated power such that the first engine group and the second engine group together deliver the necessary power Ws*.

13. The method according to claim 12 for regulating a power plant, wherein power W.sub.1 actually delivered by the second engine group is filtered by at least one filter, the third setpoint W.sub.2f* for anticipating power being such that W.sub.2f*=W.sub.2*+H.Math.(W.sub.1*W.sub.1), where (W.sub.1*W.sub.1) being a difference between the power W.sub.1 actually delivered by the second engine group and the second setpoint W.sub.1* and where H.Math.(W.sub.1*W.sub.1) is a difference filtered by at least one filter.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 shows a rotary wing aircraft having a power plant of the invention;

(3) FIG. 2 shows the preferred embodiment of a power plant of the invention; and

(4) FIG. 3 shows another embodiment of a power plant of the invention.

(5) Elements present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows a rotary wing aircraft 30 having a main rotor 31, a tail rotor 32, a power plant 1, and an avionics installation 5. The power plant 1 has a first engine group 10, a second engine group 20, and a main gearbox (MGB) 2. The two engine groups 10, 20 drive the MGB 2 mechanically in order to rotate a main outlet shaft 3 of the MGB 2. The main outlet shaft 3 is constrained to rotate with the main rotor 31 in order to provide the aircraft 30 with lift and possibly also propulsion.

(7) The tail rotor 32 is also driven in rotation by the MGB 2 via a secondary outlet shaft from the MGB 2.

(8) The first engine group 10 comprises two identical main engines 11 and 12 and a first regulator device 15. The first regulator device 15 comprises two main computers 13 and 14, each main computer 13, 14 being connected to a respective one of the main engines 11, 12, and the main computers 13, 14 are also connected to each other.

(9) The second engine group 20 has a secondary engine 21 and a second regulator device 25. The second regulator device 25 has a secondary computer 22 connected to the secondary engine 21.

(10) The main engines 11, 12 and the secondary engine 21, are all turboshaft engines, each comprising a gas generator and a free turbine driving the MGB 2.

(11) The avionics installation 5 has a third regulator device 35 and calculation means 6.

(12) FIGS. 2 and 3 show more precisely the power plant 1 in two embodiments, FIG. 2 showing the main embodiment of the power plant 1 of the invention.

(13) The calculation means 6 serve to determine the necessary power Ws* needed by the main outlet shaft 3, and consequently by the main rotor 31. For this purpose, the calculation means 6 include anticipation means 7 in order to determine this power Ws* needed by the main outlet shaft 3 while taking account in particular of the torque and/or power requirements of the main outlet shaft 3 and of the main rotor 31 depending on flight commands executed by a pilot of the aircraft 30.

(14) The first regulator device 15 serves to regulate the operation of the two main engines 11, 12 in application of a first setpoint NR* for the frequency of rotation NR of the main outlet shaft 3 and of the main rotor 31.

(15) By way of example, the first regulator device 15 serves to regulate the two main engines 11, 12 using a proportional integral (PI) regulation loop. If these two engines 11, 12 are identical, they then operate symmetrically, with each main engine 11, 12 contributing equally to driving the main rotor 31 via the main outlet shaft 3.

(16) Thus, by means of the first regulator device 15, the first engine group 10 serves to control the frequency of rotation NR of the main outlet shaft 3 and of the main rotor 31, with this frequency of rotation NR being substantially equal to the first setpoint NR*.

(17) The second regulator device 25 serves to regulate the power delivered by the secondary engine 21 constituting the second engine group 20 in application of a second setpoint W.sub.1* specifying the power to be delivered by the second engine group 20.

(18) This second regulator device 25 includes protection means for providing protection against overspeed of the main outlet shaft 3, and consequently of the main rotor 31, and against overspeed of the secondary engine 21. The second regulator device thus multiplies the second setpoint W.sub.1* by a coefficient k, where the coefficient k is greater than zero and less than or equal to 1.

(19) When no overspeed is detected, the coefficient k is equal to one. In contrast, if such overspeed is detected, the coefficient k is less than one and greater than zero. Under all circumstances, the power W.sub.1 actually delivered by the second engine group 20 is then substantially equal to the value k.Math.W.sub.1*, but may nevertheless vary a little about this value k.Math.W.sub.1* during regulation, while the coefficient k is greater than zero and less than or equal to one.

(20) The second regulator device 25 regulates the secondary engine 21 by applying a proportional integral (PI) regulation loop.

(21) The third regulator device 35 serves to regulate the operation of the two main engines 11, 12 in application of a third setpoint W.sub.2f* anticipating the power that needs to be delivered by the first engine group 10. The first engine group 10 then delivers power W.sub.2 substantially equal to this third setpoint W.sub.2f*, but that may nevertheless vary a little around this third setpoint W.sub.2f* during regulation.

(22) This third setpoint W.sub.2f* does not enable the power delivered by the first engine group 10 to be regulated directly, since this group is regulated by the first setpoint NR*. However, this third setpoint W.sub.2f* serves to improve the reactivity with which the first engine group is regulated by taking account in anticipation of the power that is to be needed from this first engine group 10.

(23) This third setpoint W.sub.2f* concerning anticipated power is such that the first engine group 10 and the second engine group 20 together deliver the power Ws* needed by the main outlet shaft 3.

(24) The necessary power Ws* needed by the main outlet shaft 3 and determined by the calculation means 6 is shared between the first engine group 10 and the second engine group 20. This necessary power Ws* is the sum of the second power setpoint W.sub.1* plus a fourth power setpoint W.sub.2*, such that Ws*=W.sub.1*+W.sub.2*.

(25) When no overspeed is detected by the protection means 29, the coefficient k is equal to one. Consequently, the power W.sub.1 actually delivered by the second engine group 20 is then substantially equal to the second setpoint W.sub.1*. Consequently, the third setpoint W.sub.2f* is equal to the fourth setpoint W.sub.2* such that W.sub.2f*=W.sub.2*, and consequently W.sub.2f*=Ws*W.sub.1*.

(26) However, in the event of such overspeed being detected, the coefficient k is less than one and greater than zero. Consequently, the power W.sub.1 actually delivered by the second engine group 20 is then substantially equal to the value k.Math.W.sub.1*. Consequently, the third setpoint W.sub.2f* is equal to the fourth setpoint W.sub.2* plus the difference between the second setpoint W.sub.1* and the power W.sub.1 actually delivered, such that W.sub.2f*=W.sub.2*+(W.sub.1*W.sub.1). It can thus be deduced that the second setpoint W.sub.2f*=Ws*W.sub.1, i.e. W.sub.2f*=Ws*k.Math.W.sub.1*.

(27) The total power delivered by the power plant 1 is thus indeed equal to the power Ws* needed by the main outlet shaft 3 and the main rotor 31.

(28) Furthermore, the second regulator device 25 includes filter means 27 to avoid injecting disturbances into the third regulator means 35. The filter means 27 serve to limit or indeed eliminate excitations generated by the resonant frequencies of a drive train relating to the power W.sub.1 delivered by the secondary engine 21. These filter means 27 may be a lowpass filter or a frequency stop filter.

(29) The third setpoint W.sub.2f* is then such that W.sub.2f*=W.sub.2*+H.Math.(W.sub.1*W.sub.1) or W.sub.2f*=W.sub.2*+H.Math.[W.sub.1*(1k)], where H.Math.(W.sub.1*W.sub.1) is the difference between the power W.sub.1 and the second setpoint W.sub.1* as filtered by the filter means 27.

(30) In addition, since the two main engines 11, 12 are identical, this third setpoint W.sub.2f* is shared equally between the two main engines 11, 12. As a result, each main engine 11, 12 needs to deliver power W.sub.2f/n, where n=2 in this example, such that:

(31) $W_{2}f/n=\frac{W_2^{*}+H.Math.\left(W_1^{*}-W_1\right)}{2}$

(32) Furthermore, the sharing of the necessary power Ws* between the two engine groups 10 and 20, i.e. between the second setpoint W.sub.1* and the fourth setpoint may be achieved by the calculation means 6 in application of various operating criteria of the power plant 1.

(33) For example, the sharing of the necessary power Ws* may be determined so as to optimize the specific consumption of the two main engines 11, 12 and of the secondary engine 21, i.e. so that the sum of the specific consumptions of the main and second engines 11, 12 and 21 is as low as possible.

(34) In another example, the sharing of the necessary power Ws* may be determined so as to optimize the maintenance of each of the engines 11, 12, 21 of the power plant 1.

(35) Finally, the sharing of the necessary power Ws* may be determined so as to optimize the performance of each engine 11, 12, 21 of the power plant 1 in the event of at least one of the engines 11, 12, 21 failing, e.g. by minimizing the time needed by each engine 11, 12, 21 to reach its maximum power in the special OEI mode.

(36) FIG. 3 shows another embodiment of the power plant 1 of the invention.

(37) In this embodiment, the third regulator device 35 uses the second setpoint W.sub.1* to determine the third setpoint W.sub.2f*. Thus, the second setpoint W.sub.1* is subtracted from the necessary power Ws* needed at the main outlet shaft 3 in order to obtain this third setpoint W.sub.2f*. As a result, the third setpoint W.sub.2f* is equal to the fourth setpoint W.sub.2* such that W.sub.2f*=W.sub.2*, and consequently W.sub.2f*=Ws*W.sub.1*.

(38) The calculation means 6 include conversion means 8 for transforming the second power setpoint W.sub.1* into a fifth setpoint N.sub.1*. The second regulator means 25 thus serve to regulate the frequency of rotation N.sub.1 of the gas generator of the secondary engine 21 in application of this fifth setpoint N.sub.1*. This frequency of rotation N.sub.1 of the gas generator of the secondary engine 21 is then substantially equal to this fifth setpoint N.sub.1*, but may nevertheless vary a little around this fifth setpoint N.sub.1*.

(39) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described above, it will readily be understood that is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.