FR2520806A1 - Twin rotor turbine engine - has differential connecting outputs of separate rotors to common output shaft - Google Patents

Abstract

The turbine engine has two rotor sections which are independent and have a power take-off to drive the accessories. The take-off (a) has a differential connected to each rotor section (6,7) having an output shaft (10) rotating at a speed representative of the difference between the speeds of the rotors. The two rotors can form the high and low pressure sections of the rotors. The output from the differential can rotate at a speed equal to N2-kN1, where N1 and N2 are the respective speeds of the low and high pressure rotors, and k is a constant.

Description

The present invention relates to a turboshaft engine comprising at least two mechanically independent rotary mobiles and at least one power take-off for driving auxiliary devices.

We know that a turbine engine generally has two mobiles rotating around its axis, namely a first mobile consisting of the compressor and the low-pressure turbine (and possibly the fan or fan) and a second mobile consisting of the compressor and the turbine. high pressure. Sometimes, the turbine engines have a third mobile consisting of a compressor and an intermediate turbine
These different mobiles are mechanically independent and are only linked to each other by the gas flows which pass through them. In addition, they rotate at different speeds and their speed excursion ranges are also different. For example, for a turboshaft known commercially under the name GENERAL ELECTRIC CF6-50 and intended to be mounted on an aircraft, the ratio R the maximum speed in flight and the minimum speed on the ground can vary from 1 to 5 for the mobile at low pressure and from 1 to 2 for the mobile at high pressure.

Furthermore, in order to drive various auxiliary devices necessary on board airplanes, such as alternators, direct current generators, and hydraulic generators, it is already known to arrange a power take-off on one of said mobiles of turboshaft engines, for example at by means of a pair of bevel gears as shown by patents FR-A-2 152 362, US-A-3 792 586 and FR-A-2 290 576.

Of course, since the drive speed of said auxiliary devices must be as constant as possible, the power take-off is arranged on that of the mobiles whose speed excursion range is smaller, which makes it possible to minimize the devices intended to regulate and adapt said training speed.

Thus, in the example given above, the power take-off is mounted on the high-pressure mobile whose ratio R varies from 1 to 2, and not on the low-pressure mobile whose ratio R varies from 1 to 5.

However, even by choosing to arrange the power take-off the mobile whose variation in the ratio R is the smallest, the fact remains that this variation is significant (from simple to double in the previous example).

We cannot do without complex regulation and adaptation devices, expensive to install and maintain, and heavy. In addition, these devices do not make it possible to avoid auxiliary gas sampling measures on the engine intended for the air conditioning of the aircraft, which disturbs the thermodynamic cycle thereof.

The object of the present invention is to remedy these drawbacks and to make it possible to eliminate, or at least simplify and reduce, the regulation and adaptation devices intended to mitigate the effects of the large speed variation of the mobile on which the driving movement of the auxiliary devices is taken, as well as avoiding the taking of gas from the engine.

To this end, according to the invention, the turbine engine comprising at least two mechanically independent rotary mobiles and at least one power take-off for driving auxiliary devices, is remarkable in that the power take-off comprises a differential mechanism connected to each of said mobiles and provided with an output shaft rotating at a speed representative of a difference between speeds proportional or equal to the speeds of said mobiles.

Indeed, the Applicant has found by examining the characteristics of certain engines that such a difference had much less variation than the speed of a single mobile of said engines.

For example, for the GENERAL ELECTRIC motor family
CF6, as well as for the PRATT and WITTNEY JT9 engines, we found that the value N2-KN1 (with N1 = speed of the mobile low pressure, N2 = speed of the mobile high pressure and K = constant) remained constant between the flight idle and the maximum flight speed, while the ratio (N2-KNi) max
(N2-KNl) min between the maximum values (N2-KNl) max for the maximum engine speed in flight and minimum (N2-KNl) min for the idle on the ground of the relationship N2-KN1, was only l '' order of 1.3, i.e., at most, the variation of
N2-KN1 between idle on the ground and in flight speed is 35%.

Also, in a turbine engine of this type, in which the two mobiles are respectively the low pressure mobile and the high pressure mobile, the differential mechanism is arranged so that the speed of the output shaft of this mechanism is equal to N2 -KN1, K being obtained by a gear ratio.

Preferably, when the turbine engine comprises a blower integral in rotation with the low-pressure mobile, the differential mechanism is arranged in the vicinity of said blower.

Advantageously, the differential mechanism comprises a freely rotating plate around the axis of said mobiles and provided at its periphery with satellites meshing with toothed rings respectively integral in rotation with said mobiles. In the case where the mobiles rotate in the same direction, this plate can carry two sets of satellites arranged on either side of its plane, the satellites of each of the sets meshing with a toothed crown secured to a mobile, while the satellites of one of said assemblies further mesh with another platform, which rotates freely around the axis of said mobiles and is moreover engaged with said output shaft of the differential mechanism. On the other hand, when the mobiles rotate in direction opposite, the plate can carry a set of satellites meshing both with a crown integral in rotation with one of the mobiles and with another crown integral in rotation with the other of said mobiles and be in engagement with said output shaft of the differential mechanism .

The figures of the appended drawing will make it clear how the invention can be implemented.

Figure 1 is a partial longitudinal section of a turbine engine, illustrating the implementation of the present invention.

FIG. 2 is a diagram justifying the principle of the present invention.

FIG. 3 shows an embodiment of the power take-off according to the invention.

Figures 4 and 5 are respectively sections along lines IV-IV and V-V of Figure 3.

FIG. 6 illustrates an alternative embodiment of the power take-off according to the invention.

In these figures, identical references designate similar elements.

It is known that part of the power developed by the jet engines of modern commercial aircraft is used, either mechanically or by taking air from the compressor stages, to supply the energy necessary for the aircraft's servitudes, and especially
1 / electrical generation systems,
2 / hydraulic generation systems,
3 / the air pressure and
air conditioner.

One of the difficulties in adapting these systems to the engine comes in particular from the notable variation in the rotation speed of the rotating parts of the engines in the operating range. For example, for the engine
GENERAL ELECTRIC CF6-50, the speed Ni of the low pressure mobile (Fan) varies in the ratio 1 to 5, while the speed N2 of the high pressure mobile varies in the ratio 1 to 2.

Due to the smaller range of speed deviations of the high pressure mobile, the mechanical energy samples are generally taken from the latter; an adaptation system (more or less complex) allows the user devices to be coupled to the power source
- for electrical generation, we implement
a speed converter group giving a
constant output speed
- for air conditioning, a
sampling on several stays of compresslon
with transfer capacity between floors, limitation
pressure and temperature
- for hydraulic generation, we use
self-regulating pumps allowing adaptation
across the full range of use,
but the dimensioning of these pumps must be
intended for extreme conditions
- for liquids intended for the engine,
variable speed pumps.

Among the penalties resulting from the use of a speed converter, we can cite: the mass, the very high price of installation and maintenance, the low energy efficiency associated with a relatively complicated system. In addition, an improperly sampled air pressure and temperature leads to poor energy efficiency.

Furthermore, the removal of air from the compressor stages disturbs the thermodynamic cycle of the engine and can lead to significant repercussions on the operation of the reactor; in the extreme, this can lead to limiting or even avoiding any withdrawal in certain operating phases.

It is therefore understandable that it is particularly advantageous to be able to overcome these various constraints.

In FIG. 1, a turboshaft engine of axis X-X is partially shown. We can see the fan bulb 1 (fan) fitted with its blades 2 and secured to its shaft 3, coaxial with the axis X-X. In known manner, the fan 1,2,3 generates a primary flow directed towards the compressors through a primary channel 4, as well as a secondary or bypass flow passing through the peripheral channel 5.

The turbine engine comprises a shaft 6, coaxial with the axis XX and integral with the compressor and the low pressure turbine (not shown). The shaft 3 of the blower is integral in rotation with the low pressure shaft 6. In addition, the turbine engine comprises a shaft 7, also coaxial with the axis
XX, integral with the high pressure compressor 8 (partially visible in Figure 1) and the high pressure turbine (not shown).

In accordance with the present invention, the turbine engine of FIG. 1 comprises a differential mechanism 9 receiving the movement of the shafts 3,6, the speed of rotation of which is
N1, and the movement of the shaft 7, the rotation speed of which is N2, and delivering on an output shaft 10 a rotation movement of which the speed is representative of a difference between speeds proportional to or equal to said speeds N1 and N2. By a return system 11, the movement of the shaft 10 is transmitted to a shaft 12 which drives different auxiliary devices (not shown).

Indeed, the examination of the operating curves of certain engines reveals that there is at a given temperature a rigorous relationship between the speeds N1 and N2 and that the law is substantially linear between the speed of the flight idle and the maximum speed.

Such curves are for example shown in FIG. 2, which relates to the GENERAL ELECTRIC CF6-50 engine. In FIG. 2, the speed N1 (in%) of the mobile at low pressure is shown on the abscissa (with 100% N1 = 3432, 5 revolutions per minute) and on the ordinate the speed N2 (in%) of the mobile at high pressure (with 100% N2 = 9827 revolutions per minute).

For ISA atmospheric conditions for example, the variation of N2 as a function of Ni is shown on the right
B, while the variation of Ni expressed in% of N2 is given by the line A.

At given atmospheric conditions, it is possible to find a straight line C, representative of a speed KN1 (with K = constant = 1.037 in the case of the GE CF6-50 engine) such that the difference D = N2 - KN1 remains constant between the flight idle speed (zone E) and the maximum speed (zone F). Indeed, between zones E and F, the line B is strictly parallel to the line C.

If the temperature varies, curve B can move between
B '(extreme case corresponding to ISA + 350C conditions) and
B "(extreme case corresponding to -400C), but the ratio N2 N1 varies at most by 10%.

(N2 - KNl) max,
Furthermore, if we carry out the ratio R =
(N2 - KNl) min in which (N2-KNl) min is the value of D at ground idle for -4 00C and (N2-KNl) max the value of D at maximum speed for ISA + 350C, we can see that this ratio R is equal to about 1.33.

Thus, the maximum difference on D is at most of the order of 35%, while N2 varies from simple to double and N1 from simple to fivefold. Therefore, using the difference
D, it is possible, without the use of complicated technology, to provide direct mechanical drive
1 / electric generators,
2 / air compressors,
3 / liquids pumps optimized for a range
reduced speed.

Obtaining power take-off at speed N = N2 KN, i can be achieved by a differential mechanism, as illustrated by Figures 3,4 and 5, on the one hand, and Figure 6, d ' somewhere else.

The embodiment of the differential mechanism 9 shown in FIGS. 3,4 and 5 is suitable for the case where the shafts 6 and 7 rotate in the same direction.

The differential mechanism 9 comprises a plate 13 which can freely rotate around the shaft 6, by means of rolling elements 14. At its periphery, the plate 13 has axes 15, for example four in number, on each of which revolve a satellite 16 and a satellite 17, the satellites 16 all being on the same side of the plate 13, while all the satellites 17 are on the opposite side.

The satellites 16 mesh, on the one hand, with an internal toothed ring 18 secured to the shaft 3 (and therefore of the shaft 6) and, on the other hand, with an external toothed ring 19 carried by a turntable 20 freely around the shaft 3, thanks to rolling means 21. The plate 20 also has a conical toothing 22, meshing with an associated conical toothing 23, integral with the shaft 10, suitably journalled, by means of bearings 24.

The satellites 17 mesh, on the one hand, with an internal toothed ring 25 secured to the shaft 7 and, on the other hand, with an external toothed ring 26, secured to the carcass of the engine and therefore fixed.

Crowns 18 and 25 turning respectively at speed
Ni and N2, it follows that the satellites 16 and 17 travel respectively at linear speeds N1 x R1 and N2 x R2, if R1 and R2 are respectively the radii of said crowns 18 and 25. Consequently, the plate 13 rotates around the Ri axis
XX at a speed N2 - R1 N1.

R2
If R3 and N3 are respectively the radius and the speed of rotation of the plate 20, we can write
R2
N3 = R2 (N2 - R1 N1)
R3 R2
Thus, the speed N3 of the plate 20, and therefore that of the shaft 10, is proportional to N2 - R1 N1. By choosing to
R2 appropriately R1 = K, so we get the relation D = N2-KN1
R2 above.

In the case where the shafts 6 and 7 rotate in opposite directions, the differential mechanism 9 can be simplified, as shown in FIG. 6. In this case, a single set of satellites 27 are journalled on a plate 28 freely rotating around the shaft 7 by means of rolling 29. The plate 28 has an oblique toothing 30, meshing with the toothing 23 secured to the shaft 10. The satellites 27 mesh with an inner ring 31 secured to the shaft 7 and with an outer ring 32 secured to the shaft 6. It can easily be checked that the speed of rotation of the plate 30 can be defined by a relationship similar to that given for the speed of the plate 20.

Given that the power taken mechanically by the differential mechanism 9 is very low, compared to the power of the engine (of the order of 0.5%), this differential mechanism respects the independence in rotation of the mobiles at low and high pressure.

Thus, the advantages of the present invention result in particular from the possibility:
1 / replacement of the hydromechanical system
drive the electric generators by a
purely mechanical superior performance system
and less penalizing maintenance.

2 / replacement of the multiple withdrawal system
of air pressure by an optimized compressor
able to reduce or eliminate levies
air on the engine stages.

3 / the drive of engine accessories (pumps
lubrication, etc ... at variable speed).

Claims (6)

l.-Turboshaft engine comprising at least two mechanically independent movable rotators and at least one power take-off for driving auxiliary devices, characterized in that said power take-off (9) comprises a differential mechanism connected to each of said mobiles (6 , 7) and provided with an output shaft (10) rotating at a speed representative of a difference between speeds proportional or equal to the speeds of said mobiles. 2. Turboshaft according to claim 1, in which the two mobiles (6,7) are respectively the low pressure mobile and the high pressure mobile, characterized in that the speed of the output shaft (10) of the mechanism differential (9) is equal to N2-KN1, N1 and N2 being respectively the rotational speeds of the mobile at low pressure (6) and the mobile at high pressure (7), while K is a constant. 3. Turboshaft according to claim 2, comprising a fan 1,2,3 integral in rotation with the low-pressure mobile (6), characterized in that said differential mechanism (9) is arranged in the vicinity of said fan 1,2, 3. 4. Turboshaft according to any one of claims 1 to 3, characterized in that the differential mechanism (9) comprises a plate (13,28) freely rotating around the axis XX of said mobiles (6,7) and provided at its periphery of satellites (16,17,27) meshing with toothed rings (18,25,31,32) respectively integral in rotation with said mobiles. 5. Turboshaft according to claim 4, in which said mobiles (6,7) rotate in the same direction, characterized in that said plate (13) carries two sets of satellites (16,17) arranged on either side from its plan, the satellites of each of the assemblies meshing with a toothed crown (18,25) secured to a mobile, while the satellites (16) of one of said assemblies further mesh with another plate (20), which rotates freely around the axis XX of said mobiles and is moreover engaged with said output shaft (10) of the differential mechanism (9). 6. Turboshaft according to claim 4, in which said mobiles rotate in opposite directions, characterized in that said plate (28), on the one hand, carries a set of satellites (27) meshing at the same time with a crown (31 ) integral in rotation with one of the mobiles and with another ring (32) integral in rotation with the other of said mobiles and, on the other hand, is engaged with said output shaft (10) of the differential mechanism (9) .