US2477954A - Gas turbine - Google Patents

Description

Aug. 2, 1949. J. J. ,L. BLANC 2,477,954

Filed 001:. 22, 1947 2 Sheets-Sheet 1 GAS TURBINE Aug. 2, 1949. J. J. BLANC 2,477,954

v GAS TURBINE- Filed Oct. 22, 1947 2 Sheets-Shret 2 II I II 'I'll Patented Aug- UNITED- STATES PATENT OFFICE [4 i i. 2 477,954- l J acques J eanLo'uis Blane, Paris, France Anplibiitih obt'ti'zz, 194 v ,""s eria1 mama I'.- o IngFrance April 1,,1947 T ith w= -=:9 -'7Cl,ims. 1 (Cl. 230-415) A A The gas. turbines (turbo-reactors or-turbcimprove the output of'thecompressor stages at propellers) thebest reshltsfiie difierent rates of speed,

AI mthe r object of the invention is to obtain some ghe iaotefistits of th= ompfessof which I adaptthem 'e lves"tof'the d 1"iving :turbine.-- I errarm e o'f the turbine; Moreover-f the-inventi'dnperm'ts to improve the as ure tiohas"'-to be aocelex ations of the turbine, ar roperty which irekI-tonjcreaSthie is' verwirhpofti'nt "hmhihesiiritehded to be grated et a, rgte very I c l os e'to 3 seen clearly in order to permit and improve the adaptation of the compressor to the turbine by adjusting the point of operation as near as possible to the pumping and to the maximum efiiclency.

As can be seen (see Fig. 2), a blading constituted by a strip I having the shape of a propeller blade, fitted by a spindle 2 at the periphery of the rim of a compressor mobile wheel and liable to rock about the axis of this spindle, the strip I bein shifted with respect to the axis 00' so that the center of gravity of the blade and the thrust center P of the aerodynamic forces acting on the said blade can be changed in a force F which has its origin at the center thrust of the blade. This force F can be divided into a force F1 which has its origin on the rotation axis 00 of the blade and a torque I=FXa. The factors governing the balance of blades such as these and which can be varied in order to carry out the variation in pitch, according to the invention, are then as follows:

(1) The torque I of the aerodynamic forces having an action on the blades or mobile blades,

(2) The resisting torque of the compressor,

(3) The rotation speed of the mobile wheel bearing the blades.

The balance of the above system can be illustrated by the following equation:

2(aerodynamic torque, residing torque, speed factor) =0 In the algebraic sum 2, one of the factors can be equal to zero. The resisting torque can be used directly or through-the medium which is proportional to it, for instance the density of the air. Also, the speed factor can be used, either directly or through the medium of the centrifugal force which it originates.

Thus, by a predetermined balance of the various above mentioned factors, a better orientation of the blades can be obtained in order to improve the output of the compressor stages at different rates of speed. As can be seen in the diagram of Fig. 1, the operating point is located at the intersectin point of the turbine characteristic with the characteristic curve of the compressor for a given speed and pitch of blade. For instance, for a same period a3 if a change in pitch is made from i2 to 13 the operating point passes from b to c. The latter being nearer to the pumping (in 0) than the point b was (in b) the efliciency has been improved; the rate of flow and the pressure ratio having increased, the overall power of the machine increases.

On the other hand, some characteristics of the compressors which adapt themselves to the driving turbine are obtained. If,-in fact, the pitch of the blades of the turbine was always as in ii for instance, it can be seen that starting from a given speed for instance, around the low speeds, the turbine would drive a compressor the operating point of which d would be located out of the characteristic turbine CD and in the pumping (shown in this case-by the line EF). In order to permit a correct operation at the selected speeds, a pitch 22 would have to be adopted giving an operating point e, but, at great speeds this pitch would have the drawback of shifting the operating point to b, in other words ina low efficiency zone. If, on the other hand, there is a possibility, in accordance with the invention, to obtain a pitch 3 at great speeds only, the result is a better adaptation and therefore a better machine.

Moreover, the invention permits to improve the accelerations of the turbine. If a change in speed is made from at to 143 with a same pitch of the blades 12 for instance, the operating point is shifted from e to b; if, in unison, and according to the invention, the pitch has been changed from 2'2 to 2'3, the point e arrives in c. During the interval in which the speed has been varied, the variation of the mass of fluid passing through the compressor, with the same pitch i2 can be 11- lustrated by the line eb. With a variation in pitch from 2 to 2'3, it would be represented by the line ec; during the same interval of variation, the output will therefore have been greater, and later the impulsion given to the turbine will be stronger. This concerns the compressor; for the whole of the machine, the results are multiplied by reciprocal inter-actions.

In the practical form of embodiment of the invention, the variation of the pitch of the blades can be obtained by means of various devices established according to the manufacturers personal requirements and accordin to the value of the factors which govern this variation.

In the example illustrated in Figs. 3 and 4, 3 indicates the rim of a mobile wheel of the axial compressor bearing in this case, at the periphery, two rows of blades or small blades I. Each of these is constituted, according to a method already known and as illustrated in Fig. 2, by a metal strip twisted in the shape of a propeller and having sectionally an aerodynamic profile. Accordin to the invention, each blade is fixed onto the rim 3 through the medium of a spindle 2 mounted on a, ball abutment 4 which permits it to rotate partially.

As it has been specified above, each blade being constituted in such a way so that it is shifted with respect to its axis of oscillation, the result is, that when the wheel 3 is driven into a rapid rotary movement, the component of the centrifugal force, in addition to the resultant of the aerodynamic forces which act on the blade, gives an elementary torque I which tends to make the blade turn about its axis. A small bevel gear 5 is fixed integrally at the lower part of each blade I. The wheel 3 bearing the blades l is mounted free on a shaft 6 which bears a disk I, which comprises here, on either side of its peripheral part, two bevel gears, 8, 8 which respectively engage with the gears fixed at the bases of each row of blades.

The blade bearing 3 and geared disks 1 are interconnected by a connected connecting rod system 9 and 9", one of the ends of which is fixed on axles l0, Hl borne by each disk, and the other being connected on a common axle ll bearing a mass l2. The compressor is driven by a central shaft 6 integral with the disk I. The disk 3 is thus driven in this movement through the medium of the connected connecting rods 9 and 9 of the mass Hi. If the centrifugal masses are carefully designed, the disk 3 follows the disk I with a variable off-set the balance of which is obtained at all times by the constitution of the resisting torque, of the position of the connecting rods, and of the value of the centrifugal force of the mass 12 and of the connecting rods. At all times, the off-set between the disks 3 and 1 depends then of the resisting torque and of the centrifugal force resulting from the rotation speed. Due to the fact that the bases of the blades borne by the disk 3 comprise a gear 5 engaging with the disk 1, it results from this that for any variations of the off-set of the two disks 3 and I there corresponds a variation of the pitch of each blade I. Thus an elementary device is 1,11 and the p ton :fiDhtituted the bo'ttom oiI-the socket; 2 5.

contalningifnsj W1llbeidescribed laterta. fluid such as on; Th inher. l8, and outer ivflxhelical v 1"; l-ft,a@Siith sheclsso act the compressor deter-. .t which is cocnteractedtbyr d admitted in the chamber u idefp essu e, hr u h n opening '2'! provided in the center of the shaitJbi; andis guidedby a conduit zfi proyidedin thedisk 3 f up ti a *distijibuting' device; arranged b tween v. Q Part".- -Th s e a prises a slide'boxj sliding in a series of bores conm stituting several compartments in ,th. piston ,2 5 and in the"piec1e' ll," name a-first compartment l tt r i sui ed by I ox 291,11 to the ri ht. i il-int rmed te m,- i h S fi ed m dianh but. ,7 e w l S de x- 2 ls.r c ms where starts a .canal returns, the a 110 an i tlc nd ji i fikla fl w hin, he a es oftl'ie'shaftb"; a'c mpartnierit '36; arranged in ane i e 7 e li j'i i lih, a 99 m tater-attest '3'. in

ts ext I anal 28 bringing. the flu d r d the butmenttiofthe slidelbox int pl ced; com ressed. sprin 9 wh ch -tc push back the said slide box tothe right.

box comprises a grooveta inLwhichissuesthe conduit kQILQiHtiOIlQd abDYQ, and .which can place itsel lop po eya calibrated-opening idilv drilled thro .t e.,wal;1;o.f the extension 3? ofthepiece r 0 communication the compartgsltwith the chamber; .26; .Finally, inthe piston, a conduit 4| ;isv;arranged, this-conduit estalo i ishingla communication between the chamher 2 1t a hollowpart 42 arrangedin front of the Je nd of jheslide box. 29, while a conduit drilled in the :collar .38;0f the; slide box '29 tet 'bli hes acornrnunication between the chamber and-the chamben32. i e s. Due to thisarransement,.thetposition of the slide box will bedetermined'bythe balance-resulting from theaction of three forces in unison: gar) A iorce ;,pro;oortional to .the centrifugal iorce which is. materialized. by the force which is enerted, on the column of liquid flowing from the servomotor, through the chamber 3?. and returned through the axle of the shaft 5' by the du ziisi, V H

b;) The el 'c sforce-lofithe spring39 located 0 ,chainber incoinmunication with the outside through a channel 435%;

gc) cc which isrproportional tetheres'istin I mile-materializedby the pressure of the 1 girl enclosed/between the piston 25 and the piece ll,-and the-value oflwhich is main tained seas to .balance the reactions created-by the driving strain of the disks on the helical gears. v v

t l-he met or these forces acts on the whole surface of the central abutment 33 of the slide 1 boxzjfi Theythird actsv on the left front endof the;sli de-,box;29 through the. channel 4!. The spring 39 adds its power to'one of the two other forces. El e; resultant of the force proportioned to he speedis opposed torthe spring 35, the

7, corn ression of which determines adefinite positiomoithe slide box 29., The calibrated. bore 4c drilled in the extension 31. of the' part H is norn ally iclosed by; the collar 38 of the slide box, which is submitted, on one hand by its groove 385., to thejmotive pressureoi the fluid, and on ernalright surface ism-relation with the draining pharnber 32through the medium of the channel 43; ,;Thus,,as"it-will be noticed, any movement-pr me slide-box .23 causes immediately a correlative shifting of the piece t1, and

thereby, through the play, of. the helical gears I Q-Q lS and' 2,!l--,i?l ,4 an angularly relative displacement of the disks time "I., This rncvei= ment determines, through the mediumof the knee-joint, levers. Z4,v a pivoting ofthe blades 5 about their axisloi fixation. Thus a definite pitch of the blades. [corresponds toeach balance" position given by the torque and the rotation speed V. v

.Fig. 6 con ernsa device which uses an electric servo-motor. ,The device illustrated in Fig. 6 comprises two stages each of which comprises as above, two disks 3v and 1, one ofwhich, 3, hearsonits ri rn mobiletblades l, and the other,

. 1. ,driving the compressor, bears on its periphery sockets/22 in which areengagedlance-joints 23 proyidedat. theend of levers 24,-integral with the phases oi; the blades. The junction between no;pljates of each stage is insured, by an he epifiy b d l s oi gcarsythe planet wheeLcar-ti' 75' ri'r'of which I4 is integral with the driving plate the;

I, the outer crown 45 is fixed onto the blade bearing disk 3, and the planet wheels 46 engage with a central pinion 41 clamped on a shaft 6' located in the axis of the disks 3 and 1, and driven through the medium of a transfer case 48, by an electric motor 49.

A servo motor, located for instance on the casing of the transfer case 48, regulates the movement of the motor 49 and accordingly the off-set between the disks 3 and 1'. This servo motor includes a lever 5| which comprises three connected parts, namely:

A first connected part 5i on which act, in opposition, on one hand the rotation speed of the compressor, materialized here by the thrust of deadheads 52 submitted to the action of the centrifugal force and driven at a speed proportioned to that of the compressor, and on the other the resisting torque represented by the characteristic factor of the compressed fluid (ratio between the fore and aft depression and the density of the fluid to be compressed) and which is materialized by an aneroid device 53, while a spring 54 sets, for each balance position, a definite position of the connected part SW;

A second intermediate connected part 51*, to which is connected a mobile organ for instance a needle 55 which controls the sensitive element of an electric circuit, for instance the rheostat 56 of a Wheatstone bridge;

A third connected part 5l, in relation with the central shaft 6', for example through the medium of a tangent wheel and endless screw mechanism 5'! driven through the medium of the transfer case 48, so that its position is determined according to the oif-set existing between the two disks 3 and 'l.

Due to this arrangement, for any variation of torque or of speed, the balance of the forces exerting a stress on the connected part 5| is modified. The connecting point 5l being momentarily fixed, the lever 5|, moving about this point, entrains, by the movement of the needle 55, a variation of the resistance 56 and this variation switches on, through the medium of a Wheatstone bridge 58 the electric motor 49. The latter determines a variation in the off-set between the two disks 3 and I, and consequently a correlative variation of the blades I. The connecting point 5l is then driven along in this same movement and returns the lever 5| in a balanced position, cutting off thereby the electric power supply to the motor.

It is to be understood, as it stands out from the hereinabove text, that the invention is not limited in its realizations only to the examples described and illustrated, but can take the form of any other modifications.

I claim:

1. A gas turbine including an axial several stage compressor and a drive shaft driving the said compressor, in which each stage of the said compressor comprises a first rotating disk v spindles mounted at the periphery of said first disk so as to be able to pivot respectively about a radial axis, blades integral individually with each spindle, a second disk mounted co-axially with the said first disk and integral with the first driving shaft, means connecting mechanically the said second disk with each of said spindles, so that a relative angular displacement of the two disks determines correlatively a pivoting of the said blades about a corresponding radial axis, and means connecting the said second disk to the first disk so that the first 8 disk follows the said second disk with an angular offset the balance of which depends, at all times, on the resisting torque and the centrifugal force.

2. A gas turbine according to claim 1, in which the said means connecting mechanically the said second disk with each of the said spindles comprise a bevelled geared crown wheel integral with said second disk and a bevel gear clamped on each of the said spindles and meshing with the said bevelled geared crown wheel.

3. A gas turbine according to claim 1, in which the said means connecting mechanically the said second disk with each of the said spindles comprise a lever fixed on each of said spindles forming a ball at the end of the said lever, the said ball being engaged in a corresponding socket provided on the said second disk.

4. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise pairs of interconnected connecting rods and connected on one hand on the said first disk, and on the other hand, on the said second disk, and weights borne respectively by each of said pairs of connecting rods, the said weights being designed so that the amount of ofiset between the two disks depends on the centrifugal force exerted on the said Weights of the said connecting rods.

5. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise a servo-motor operating through the medium of a fluid.

6. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise a crown wheel helically geared externally integral with the said second disk; a crown wheel helically geared internally integral with the said first disk, an annular piece helically geared internally and externally meshing respectively with the teeth integral with the second disk and of the first disk, an annular extension provided on the first disk and adapted so as to constitute a piston in a corresponding hollow part in the said annular part, a slide box engaged on one hand with the said extension and on the other hand, with the said annular piece, elastic means acting on one hand on the said slide box, the said slide box being moreover under the action of a fluid under pressure admitted in the said hollow part of said annular piece, so that the position of the said slide box and consequently the angular relative position of the said second disk and of the said first disk are determined at all times, by the balance resulting from the simultaneous action of the said elastic means, of the centrifugal force acting on ghedsaid fluid and on the pressure of the said 7. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise an electric servo-motor.

8. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise a planet wheel bearer integral with the said second disk, an internally geared crown wheel integral with the said first disk, planet wheel pinions mounted on said planet wheel bearer and engaging with the said internally geared crown wheel, a central pinion clamped on said driving shaft and engaging with said planet wheel pinions, an electric motor driving said driving shaft, means to control the operation of said electric motor, and

76 mobile elements arranged so as to move under the action of the speed variations of said compressor, mobile elements arranged so as to move under the action of the variations of the resisting torque and a mobile organ driven simultaneously by the said mobile elements first mentioned and by the said mobile elements mentioned after, so as to control the means controlling the operation of the electric motor.

9. A gas turbine according to claim 1 in which the said means connecting the said second disk to the said first disk comprise a planet wheel bearer integral with the said second disk, an internally geared crown wheel integral with the said first disk, planet wheel pinions mounted on said planet wheel bearer and engaging with the said internally geared crown wheel, a central pinion clamped on said driving shaft and engaging with said planet wheel pinions, an electric motor driving said driving shaft, means including an electric relay controlling the operation of the 20 2,443,355

, 10 electric motor, means to control the operation of said electric motor, and mobile elements arranged so as to move under the action of the speed variations of said compressor, mobile elements arranged so as to move under the action of the variations of the resisting torque and a mobile organ driven simultaneously by the said mobile elements first mentioned and by the said mobile elements mentioned after, so as to control the said 0 electric relay.

JACQUES JEAN LOUIS BLANC.

REFERENCES CITED The following references are of record in the 15 file of this patent:

UNITED STATES PATENTS Number Name Date 1,481,188 Damon Jan. 15, 1924 Black et al Sept. '7, 1944

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