US2296701A - Gas turbine - Google Patents

Description

" Sm. 22, i942.

Filed Feb. 20, 1940 6 Sheets-Sheet 1 sepa, 22, 1942.

L. F. G. BUTLER lETI' AL GAS TURBINE Filed Feb. 20, 1940 6 SheeiZs-Slleefl 2 Sept 2, i942.,

L. F. G. BUTLER ETAL GAS TURBINE n Filed Feb. 20, 1940 A 6 Sheets-Sheet 5 Sept- 22, w42. L. F. G. BUTLER ETAL GAS TURBINE Filed Feb. 20, 1940 6 Sheets-Sheet 4 Sept- 22, 1942- L. F. G. BUTLER Erm. 2,296,701

GAS TURBINE Filed Feb. 20,-1940 6 Sheets-Sheet 5 Sept. 22, 1942. L. F. G. BUTLER Erm.

GAS TURBINE Filed Feb. 20, 1940 6 Sheets-Sheet 6 Patented Sept. 22, 1942 GAS TURBINE Leonard Frederick George Butler, Ernest Briggs,

and Edward Bowness, Bristol, England, assignors to The Bristol Aeroplane Company Limited,

, Bristol, England, a British company Application February 2o, 1940,`s eria1 No. 319,950

In Great Britain January .21, 1939 4 Claims. (Cl. 2.430-116)v This invention relates to gas-turbines such as may be used for driving the superoharging com-A pressor of an internal-combustion engine, the turbine being driven by the exhaust gases of the' engine. v

The object of the invention is to provide improved cooling and'lub'rication of the working parts.

According to the invention, a gas-turbine comprises an anti-friction bearing disposed closely adjacent the rotor and means for circulating cooling fluid, such as air, through a space between the outer race of the bearing and the surrounding structure and/or through a space between the inner race of the bearing and the rotor shaft. The said ow of fluid is preferably induced by means of a centrifugal fan the blades of which are mounted adjacent the rotor, on the bearing side thereof,so as` to draw air through the bearing and discharge it over the adjacent face of the turbine rotor. to provide a centrifugal fan between a turbine It is already known rotor and its supporting bearing but there is atendency for such a fan to produce mere turbulence unless its points of intake and discharge are arranged in definite relationship tothe bearing and the rotor blades respectively. According to another feature of the invention, the blades of the fan are shrouded on both sides, the blades being shrouded on the turbine rotor side by abutting against the adjacent face of the rotor. rThe gas-turbine is of the axial-flow type so that air is compelled to flow into the central eye of the fan and out through the inter-blade spaces.

The gases for driving the turbine are supplied to an annular nozzle, having a ring of xed guide-venes, by a scroll-shaped chamber. Where this chamber is disposed on the same side of thel rotor as the bearing aforesaid there is a tendency for the heat of the gases to flow to the bearing. Means may be provided, accordingto the invention, for reducing this flow of-heat.

Where the turbine drives a supercharging compressor for an internal-combustion engine, the

Ilubrication requirements of the turbine bearing` have no fixed relation to the engine speed. A turbo-compressor for superchargingan internalcombustion engine, according to another feature of the invention, therefore comprises one or more lubricating pumps driven by the turbine shaft so as to supply ametered feed of lubricant to the bearing. Where the' compressor comprises a centrifugal fan mounted on the same shaft as the turbine rotor the common shaft may besupported in two or more bearings spaced apart lengthwise of it and there may be a separate pumpor group of pumps appropriated to each bearing.

The space, above referred to, between the shaft and the inner race of the turbine bearing may be supplied with cooling liquid from one of the said pumps; the said liquid is preferably lubricating oil which also lubricates the said bearing.

A specific embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a sectional elevation of a turbocompressor for use in conjunction with a supercharged'aircraft engine, Figure Lbeing a section on the line I-I of Figure 2,

Figure 2 is an underplan of the installation shown in Figure 1,

Figure 3 is an elevation of a detail, being a view in the direction of the arrow 3- of Figure 1,

Figure 4 is a view similar to Figure 2, drawn to an enlarged scale, being a section on the line 4-4 of Figure 5, y

Figure 5 is a sectional elevation corresponding to Figure 4 showing the turbine bearing and associated parts, being a section on .the line 5--5 of Figure 4, i l

Figure 6 is a sectional elevation, also drawn to the same scale as Figure 4, showing the lubricating pump, the impellor bearing and associated parts,` and Figure "Iis a plan, tothe same scale as Figure 1', showing the fan which is carried by the turbine rotor. I

The general arrangement of the turbo-com pressor will now be described with reference to Figures 1, 2 and 3. 'I'he impellor I0 of a centrifugal blower of known or usual construction is attached by splines II and other means (described below) to a shaft I2 which rotates in a top bearing I3 (Figure 6) and a bottom bearing I4 (Figure 5). The top bearing is supported in the volute chamber I5 through which air, or a mixture of fuel and air, is admitted to the eye I6 of c the impellor. The air enters the chamber through an air-inlet I 1 (Figure 2) and is discharged by the impellor I0 through fixed diffuser Vmixture to lthe engine cylinders. The compressor 'the part 42, the studs of the present specication is therefore preferably a first-stage compressor in a two-stage System. but the invention is not limited to this arrangement.

The bottom of the shaft l2 is formed integrally v with a turbine rotor 2l having blades22 through Vas above stated, the gases may simply be discharged into the external airstream ilowing along the underside of the aircraft fuselage or wing.

The detailed construction of the turbine .bearing I4, and associated parts, will now be described with reference to Figures 4 and 5. The shaft I2 is cut with a groove 25 surrounding it near the rotor 2|, the. groove being bounded at its upper end by a shallow ilange 21 on the shaft and at its lower end by an unreduced portion 23 lying adjacent the rotor disc. The groove 25 is surrounded by a thin steel sleeve 29 the bottom end of which, however, is thickened at 39 and has integrally formed with it a short vertical .A cylindricallportion 3l the top of which engages the bottom of the inner race 32 of the ball-bearthe bearing I4 and a'series of radial tunnels, each `from a ring 53 bounded at the bottom by the rotor disc 2|. at the top by the shroud 55 and at each side by two adjacent blades 5,4'.

The bottom plate 31 of the compressor casing is formed with six symmetrically-disposed reinforced rlbs 51,' at the innermost and lowermost point of each of which a boss 53 is formed to receive the screw-threaded end of a stud 53. The stud is formed with a reduced portion 53 in its length which passes through asleeve 5I having from Figure 4 that the fingers 51 are separated ing I4. Engaging the'top of the race 32 is the downwardly-extending tubular part 33 ot a sleeve 34 surrounding the shaft. Near its upper end the sleeve 34 is cut with a series of grooves 35 which form a packing between the sleeve (which rotates with the shaft) and a surrounding boss 35 which is formed integrally with the bottom wall 31 of the compressor casing I3. The

. wall 31 also has formed integrally with it a downwardly-extending tubular casing 33 which supports the outer race of the turbine bearing and the fixed'guide-vanes 25 as will now be described. Surrounding the outer race 40 of the bearing I4 is a steel sleeve 39 of which the bottom end is ilanged outwardly as shown at 4I to abut the underside of the bottom portion 42 of the tubular casing 39. The sleeve 39 is cut with a groove 43 extending right round it so 'as toleave shoulders 44, 45 at the top and bottom respectively each engaging the inner wall of the part 42. As

shown in Figure 4 the shoulder 44 is cut with four notches 45 spaced equally around it so as to provide communication between an alr-space 41 inside the tubular casing, and the groove 43 refer-red to. The shoulder 45 is out with six oblique holes 49, equally spaced around the sleeve, each leading from the groove. 43 to a space below the outer'race 49 of the bearing. 'I'he sleeve 39 is held in place by an annular plate 49 fastened by studs 59 and nuts 5I to the bottom of 53 also passing through the flange 4I on the bottom of the sleeve 33. The inner edge of the plate 49 underlies the outer race 45 of the bearing which is separated from it by a waved springy washer 52. The bearing is thus supported by the plate 49.

'I'he thick portion 33 at the bottom of the sleeve 29 is separated from the disc 2| of the turbine rotor by the hub 53 of a centrifugal fan having blades 54 (see also Figure 1)v the lower edges of which abut against the top face oi' the rotordisc and'the upper edges of which are shrouded by a conical shroud` member 55 so as to,form a central annular eye 53 lying' beneath `Portion 33 -of the sleeve from one another by wide scallops or recesses 53 the purpose of which is' explained below. In Figure 4 one of the studs 59 and its associated sleeve 5I Iare shown in section so that the shape of the nger 51 in relation to the boss 53 can be` clearly seen.

The scroll-shaped chamber 24'to which the exhaust gases are admitted is supported from the ring 63 in the following manner. Ihe top inside wall 10 0f the chamber is formed with a flange 1I at its inner edge and an outer top wall 12 is similarly iianged at 13 the flanges 1I and 13 being en gaged by -a 'series of bolts 14 which pass through the ring 53 and are engaged by nuts 15. 'Ihe flange 1I is, however, separated from the base of the recess in the ring 53 in which the'iianges lie by two or more gaskets 15 of asbestos or other heat-insulating material. The two top walls 10 and4v12 of the exhaust chamber are spaced apart and the space between them is occupied by a lagging 11 of suitable non-'conducting material.

The inside upper wall 13, at its outer edge-carries `a ring 13 welded to'- it (see also Figure 3); welded to .the ring '1,3 is a plurality of brackets 19 of which the upper ends are turned over and fastened to the bottom plate 31 of the compressor casing by the nuts 33 oi' suitable studs. Each bracket 19 is perforated as shown at 3| and is of such lightness and ilexibility a's will permit relative movementbetween the exhaust-gas chamber and the compressor casing in the manner described below. As shown in Figure 3 small plates 32 are welded to the outer wall 12 of the scrollshaped chamber; each of these plates carries a bolt 33 passing 'through the dange 13 and engaging a nut 34. In this manner the two upper walls 12 and 13 of the exhaust chamber are secured together by their outer periphery.

The bottom wall 34 of the exhaust chamber is supported by beingwelded along the line 53 to the inner upper wall 15.

It will be explained below how a metered ilow of lubricating oil is supplied along an internal conduit 35 in the shaft I2, througha radial passage 32, to the groove 25. oil passes through a port 33 in the steelsleeve inner race 32 of the bearing. From the space the oil ows through one or more ports in the depending cylindrical 34 into th immediately above the bearing. The oil ilows From this groove the espace through the central hole in the plate 49.

The sleeve 34 is formed with a flange 92 of slightly less external diameter than the internal diameter of the sleeve 39 so as to leave a narrow annular space 93. Air from the chamber 41 canflow through this space into the space 9|. Air enters the chamber 41 through a lateral port 94 to which a suitable air-filter 95 is fitted.

As shown in Figure 1 the impellor I0 of the compressor is engaged on its lower side by a coneshaped plate 96 and on its upper side by a simi'- lar plate'91 (see Figure 6). The plate 91 is formed with a sleeve-shaped portion 98 which is cut with a series of grooves 99 to form packing between the sleeve and a downward extension from a ring I0| which is attached to the wall I5 of the inlet volute by studs and nuts |02, |03. The nuts also locate an annular plate |04 between which and a shoulder at the bottom of the ring |0| the outer race |05 of the impellor bearing I3 is clamped. The inner race is engaged at the bottom by the top of the sleeve 98 and at the top by a washer |06 which is held in place by a nut |01 screw-threaded to the shaft I2. At its upper end the shaft I2 carries a' worm |08 which meshes with a worm-wheel |09 whereby the oil pumps (described below) are driven.

The turbo-compressor shaft is assembled in the following manner. The'turbine bearing I4 having been assembled in the surrounding casing,

with which a stem |3I is integrally formed and leads down into the interior of the shaft I2. Radial ports V|32 connect the groove |29 with the bore |33 of the stem. Thus the delivery of the pump-cylinder I|9 is supplied to the interior of the shaft |2. The other cylinder is equipped with a similar delivery port and ball-valve the valvechest of which is connected by a conduit |34 to a central space |35 in the cylinder block H8. From this space the oil is delivered along the interior of a shaft |36 which is cross-pinned to the shaft |31 with which the worm-wheel |09 is integrally formed. The shaft |31 where it enters the sleeve I38which lines the enlargement II2 is formed with a groove |39 which is connected by a port |40 with the interior of the righthand end of the shaft. At its left-hand end the shaft |31 is cross-pinned to a shaft |4| having a nonf circular portion |42 for engagement with the end of a exible shaft from which a tachometer is driven to indicate the rate of revolution of the turbo-,compressor shaft. Oil from the space |39 lubricates the bearing between an enlarged portion |43 of the shaft |31 and the surrounding sleeve |38 and, having passed beyond this portion, escapes through a conduit |44 in the casing III into the cup-shaped chamber |45 formed-by the central portion of the compressor casing I5.

and the sleeve 34 having been inserted through the boss 36, the fan-hub 53 and the part 29, 30

The cone-shaped plate |49 cut on the inside wall of the sleeve I4.

' face cam |53 which engages simultaneously with the race ||0, the sleeve S8 and plate 91, the

impellor hub, the plate 96v the sleeve 34, tl'ie race 32, the parts 3 I and 30, and the fan-hub 53 are all clamped between the nut |01 and the turbine rotor disc 2|.

The oil pumps will now be described. Engaging the top of the impellor casing I5, as shown in Figure 1, is a conical closure plate III which is formed at one side with a tubular enlargement II2 and at the other side with an enlargement I I3 in which the pumps are accommodated. The enlargement I I3 is engaged internally by a sleeve ||4 of which the outer endis fianged at |I5, the flange being aixed to the plate III by suitable bolts (not shown). Between the sleeve |I4 and the surrounding wall of the part ||3 'an annular space III is formed into which a conduit |I1 leads from areservoir (not shown) of lubricating oil. The end of the sleeve II4 is engaged by a cylinder-block- I|8 which is cut with two cylindrical recesses II9, |20 toaccommodate pistons |2I, |22, respectively. The cylinder II9'and the surrounding sleeve |I4 are cut with a conduit |23 to form-an inlet port from the groove I|6 to the interior of the cylinder. This port is controlled by the piston I2I in a manner described below. The delivery port |24 of the cylinder II9 is controlled by a spring-pressed ball-valve |25 of which the valve-chest communicates through a port |26 and a conduit |21 in `thesleeve II 4 and casing II3with a conduit |28 in the casing. This c'onduit leads to a groove |29 in a plug |30 which closes the top of the conical casing I and notches in the pistons 2| |22 whereby, upon rotation of the cam, the pistons are reciprocated in their cylinders. The shaft |52 is borne in the central recess |35 in the cylinder block and the shaft |36 is borne at its right-hand end in the shaft |52 and at its left-hand end in a bush |54 in the inner end of the sleeve II4.

As the piston |2I, for example, is moved to the left as seen in Figure 6 the ball |25 closes and a vacuum is produced in the cylinder ||9 until the port |23 is uncovered'. Thereupon oil from the space I I6 fiows into the cylinder and on the succeeding stroke to the right this oil is supplied through the delivery port |24 in the manner already explained. The pump |22 operates in the same manner.

It will be understood that the shaft I2 rotates at a high speed and the gearing |08, |09 and the epicyclic gearing |46, |41, |48, |49, |50 ensures that the pump-plungers I2I, |22'are driven at a suitably reduced speed.

The oil which enters the space |45 through the port |44 flows downwardly through the bearing I3 and lubricates the balls escapes slowly through the packing 99, |00, and is discharged by centri.- fugal force *from the bottom edge of the coneshaped plate 91. At this point the oil enters the streain. of air flowing into the eye I6 of the impellor.

The manner in which the various features described above with reference tothe drawing con* tribute to the cooling of theturbine bearing will now be described. It w1ll be understood that the fan 54, 55, which is carried by the turbine rotor will suck air downwardly through the central aperture of the plate'49 from between'the races 32, 40'of the bearing I4. This will create a suction b elow the plate 49. Air will therefore flow from the chamber 41 through the notches 46 in the sleeve 39, into the groove 43. From this groove the air will flow through the holes 48 to the eye of the fan. In passing through the groove 43 the air insulates the outer race 40 of the bearing from heat which would otherwise be conducted to it from the surrounding casing 42. It will be seen that the groove 43 extends in a direction parallel with -the axis of the shaft by a distance greater than the dimension of the race 40 in this direction so that the only heat which is conducted from the part 42 of the casing directly to the outer race 40 of the bearing must pass either through the uncut portions of the shoulder 44 or through the shoulder 45 of the sleeve 39.

Another path for air exists through the narrow space 93 into the space 9|. From this point the air flows through the bearing in company with the oil and enters the eye of the fan. The suction which exists at the lower side of the plate 49 causes yet a third stream of air to ow between the bottom plate 31 of the compressor casing and the top of the exhaust chamber, radially inwardly and downwardly, through the slot-shaped spaces 68 between the fingers 67, and into the eye of the impellor. It will be seen that the only way in which heat can be conducted from the vane-ring 63 tothe part 42 of the bearing casing is along the fingers 61. The area of contact is reduced to a minimum by reducing the diameter of each of the studs 60 where it passes through the sleeve 6I and, where the faces of the parts 61 and 58 abut, an insulating washer 64 is interposed.

The heat can also iiow from the blades 22 of the rotor, through the rotor disc 2`I to the shaft I2 and from the shaft I2 to the bearing, but conduction of heat along this path isvreduced to a minimum as follows.

The oil which is pumped into the conduit 8S within the shaft I2 ows out through the radial passage 81 into the space 26, through the port 88 intothe space 89, through the port 90 into the space 9I and then flows through the bearing to lubricate it and is finally discharged into the eye of the fan 54. The oil is ultimately discharged with the exhaust'gases into the airstream. The rate of ow of oil is very small in relation to the total consumption of engine oil so that this loss is not serious. of the bearing from the adjacent part of the shaft I2 and it will be seen that the groove 26 extends in a direction lengthwise of the shaft-axis considerably beyond the vbearing on either side. Thus, the only path by which heat can be conducted from the shaft to the inner race of the bearing is through the flange 21 or the unreduced portion 28 of the shaft and then along the sleeve 29; The oil which flows continuously through the groove 26 keeps down the temperature of the sleeve 29.

The diiferences of temperature to which the installation is subjected give rise to relative movements which are accommodated inthe following manner. The expanding and contracting of'the exhaust-collecting scroll 24 in relation to the impellor .casing are accommodated by the flexible brackets 'I9 which are sufficiently resilient -for this purpose as has already been explained. The shaft I2 is suspended by the impellor bearing I3, the turbine 'bearing I4 accommodating only lateral thrusts. Any vertical movement of the shaft with respect to the surrounding easing is accommodated by movement of the outer race 40 of the turbine bearing with respect to the The space 26 insulates the race 3-2 sleeve 39. The spring-washer 52 can expand and contract to accommodate such movements.

The conduction of heat from the exhaust system to the compressor casing is reduced by the lagging 'I1 already described. In addition, the inward and downward flow of air between the -wall 'l2 of the exhaust chamber and the bottom wall 21 of the compressor casing keeps the com- Ipressor casing cool. The lagging referred to must be extended in order to cover the pipel 23 and for this purpose the flange 18 is shaped as shown in `Figure 2 so as to conform to the maximum diameter of the pipe 23 and, as shown diagrammatically .in Figure 1, the lagging I1 may be extended to form a saddle |60 engaging the upper half of the pipe 23.

The compressor casing may also carry an out-1.

wardly-extending plate ISI, of any suitable radius, to prevent fuel or other combustible matter from dripping on to the hot exhaust system from the engine above.

The various means, above described, for insulatingthe turbine bearing from the hot parts of the exhaust system ensure that the oil in the .bearing is not disintegrated. In an alternative form of the invention, not shown in the-drawings, the space 26 between the inner race and the shaft could .be cooled by air instead of by the lubricating oil. The arrangement wherebyl the lubricating oil pumps are ldriven by the turbine shaft ensures that a metered flow of oil is supplied to the bearings at arate depending yupon the bearing requirements. t

Although the invention has Ibeen described in relation to ball-bearings for the turbo-compressor`shaft it can be applied to an installation having anti-friction bearings of the cone or roller type.

Moreover, the invention is applicable to turbines and turbo-compressors generally and is not limited to the superchargers of internal-combustion engines.

We claim:

1. A gas-turbine comprising a turbine rotor and an anti-friction ibearing disposed closely adjacent the turbine rotor, Walls forming al space between the outer race of the bearing and the surrounding structure and a centrifugal fan mounted adjacent the rotor, at the bearing side thereof, so as to draw air through the .bearing and through the said space and discharge it over the adjacent face of the turbine rotor.

2. In a turbo-compressor for a supercharged' and to said"bearing, means admitting air to said bearing and to the exterior of said wall and openl ings through which the air and oil are extracted by said fan.

blades whereby the fan induces a ow of cooling fluid through and around the bearing and out through the inter-blade spaces of the fan.

4. An axial ow gas-turbine comprising a.

rotor, a shaft -for the rotor, an anti-friction bearing about the shaft adjacent the rotor, a centrifugal fan having blades lying along and shrouded at that side by the face of the rotor nextsaid bearing, a shroud on the outer side of said fan blades having a substantially central eye adjacent the bearing whereby the Ian induces a. fiow of air through the bearing and out through the 5 inter-bladespaces of the fan.

LEONARD FREDERICK GEORGE BUTLER. ERNEST BRIGGS. EDWARD BOWNESS.

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