US2752858A

US2752858A - Air turbine driven pump

Info

Publication number: US2752858A
Application number: US171624A
Authority: US
Inventors: Donald M Berges
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1950-07-01
Filing date: 1950-07-01
Publication date: 1956-07-03
Anticipated expiration: 1973-07-03

Description

Jufly 3, 1956 D. M. BERGES AIR TURBINE DRIVEN PUMP 2 Sheets-Sheet 1 Filed July 1, 1950 fnuenior'" 0710105 M Jufly 3, 1956 D. M. BERGES 2,752,358

AIR TURBINE DRIVEN PUMP Filed July 1, 1950 2 Sheets-Sheet. 2

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AIR 'runumn nnivlsn PUMP Donald M. Borges, Lakewood, Ohio, assignor to Borg- Warner Corporation, Chicago, 111., a corporation of lllinois Application July 1, 1950, Serial No. 171,624

3 Claims. (Cl. 103-497) This invention relates to an air turbine driven tluid pump, and more particularly to an overspeed control mechanism for an air turbine driven fluid pump.

Air turbine driven lluid pumps are sometimes employed in conjunction with jet type aircraft engines. Such pumps may be employed, for example, to inject fuel into the after-burner of this type engine or to inject water with fuel into the after-burner. T he pumps are normally used only intermittently and a limited supply of fuel or water is provided to prevent damage to the engine from overloading. These pumps are normally designed to operate at extremely high rotational speeds and, thus, if the pump continues to rotate after exhaustion of the fluid supply to the pump, the pump will tend to overspeed. Overspeeding may be sufficient to cause flowering or deflection of the pump blades and destruction of the pump.

In order to pre ent overspeeding of the pump, it has been proposed to employ a braking surface which, upon slight outward deflection of the pump impeller blades, would be engaged to cause slowing of the pump impeller. it has also been proposed to employ a pressure responsive switch connected in the discharge duct of the impeller which, when the discharge pressure dropped below a predetermined value, would actuate mechanism to shut off the supply of air to the air turbine. Neither of these proposals provided an entirely satisfactory solution to the problem. However, in the application of John A. Lauck, Serial No. l62,l94 filed May 16, 1950, now U. S. Patent No. 2,694,979, there is disclosed a very practical and satisfactory mechanism for slowing the pump upon release of the pump load to prevent damage to the pump in which a butterfly type valve 18 disposed in the air inlet duct of the air turbine and has associated therewith a servomotor effective to close the butterfly valve upon the pressure at the pump dropping below a predetermined minimum value. The present invention relates to a modification of the arrangement disclosed in this Lauck application pro viding improved operation particularly under starting conditions.

An object oi the present invention is to provide an air turbine driven fluid pump incorporating a new and improved overspeed control mechanism.

A further object of the present invention is to provide a new and improved overspeed control mechanism incorporating means enabling remote control of the operation of the control mechanism.

in accordance with one embodiment of this invention, there may be provided an overspeed control mechanism comprising essentially a butterfly type valve disposed in the air inlet duct of the air turbine and having associated therewith a servomotor effective to close the valve upon the pressure at the pump dropping below a predetermined minimum value. A solenoid operated piston is associated with the butterfly type valve for causing the valve to open when the solenoid is energized to permit air flow through the turbine to drive the pump, particularly under starting conditions.

tcd States Patent 9 Other objects and advantages of the present invention will be apparent from the following detailed description thereof taken in conjunction with the drawings wherein:

Fig. l is an axial sectional View of an air turbine driven fluid pump constructed in accordance with this invention and incorporating as an integral part thereof the overspeed control mechanism responsive to pump outlet pressure; and

Fig. 2 is an axial, sectional view of the air tut'bin driven fluid pump constructed in accordance with this invention and incorporating an integral part thereof the overspeed control mechanism responsive to pump inlet pressure.

Referring now to the drawing, it will be seen that the air turbine driven fluid pump of this invention comprises a generally cylindrical, three-sectioned housing llll, the sections of which are rigidly secured together, as by the bolt ll. Air inlet 32 is provided at the left end of the housing and a fluid inlet 13 is provided at the right end of the housing. The air inlet 12 may be connected by a suitable duct to any source of air pressure as, for example, a jet engine compressor an.- the fiuid inlet 13 is connected to a source of fuel, or where the pump is used for water injection, to a source of Water. The fuel or water supplied to the fluid inlet 13 must be supplied under pressure and in an actual embodiment, the fuel or water is supplied under a pressure of not less than 5 p. s. i., as a desired minimum. Substantial dropping of the fluid inlet pressure below this value may result in improper operati on of the fluid pump.

Air entering inlet 12 passes through turbine stator blades 14 and drives turbine rotor l5, which is mounted on the left end of a shaft 16 journalled in the mid-section of the housing body. Fluid entering the fluid pump through the inlet 13 is pumped by an impeller 17 which, in the embodiment shown, is of the centrifugal type, and

which delivers fluid under pumping pressure through an outlet or discharge duct 18. impeller 17 is secured to the right end of shaft 16 by an axially extending bolt 2d, which is threaded into the end of the shaft 16. The outlet duct l8 may be connected to any fluid pressure utilization device for which this apparatus is intended as, for example, an injection nozzle located in the after'burner of a jet engine.

As pointed out in the earlier filed application of Kodet et al., S. N. 85,884, filed April 6, 1949, now U. S. Patent No. 2,7l5,36'7, an air turbine driven fluid pump of this type may be employed to deliver fluid at very high pressure, that is, pressures on the order of 250 to 400 pounds per square inch. At the same time, since the pump is intended for use in aircraft, its dimensions must be kept as small as feasible. Accordingly, in order to develop the required power, it is the practice to operate the turbine at on tremely high rotational speeds, that is, speeds on the order of 25,000 R. P. M. and higher and this, of course, necessitates a high pressure air supply to the turbine rotor assembly. The high pressure air flow which may be on the order of 45 to 90 pounds per square inch or higher, applied to the rotor blades from the left, as viewed in Fig. 1, tends to force the driven shaft 116 and associated parts to theright and would, if not compensated in some manner,

produce a side bearing pressure, that is, a pressure axially of the shaft of such a high value as to rapidly Wear the bearing surfaces as well as to decrease the efiiciency of the pump. As described in the aforementioned Kodet et al. application, the various pressure areas in the pump are balanced one against the other in such manner that there is produced a resultant pressure of sufficiently reduced amount so that it may be employed to establish a definite location and bearing pressure for a thrust disc or washer 21 with respect to an adjacent bearing surface 22,

the disc 21 being mounted rigidly on the driving shaft 16 and located in the recessed chamber 23 formed at the right end of the middle housing section adjacent the left side of impeller 17.

A pump constructed as described above and more particularly described in the aforementioned earlier filed Kodet et al. application is extremely efficient, and capable of operating for long periods at very high rotational speeds. However, if for any reason the fluid supply to inlet 13 is terminated, or the pressure thereof reduced substantially below the desired minimum value as hereinbefore stated, thereby removing the load from the pump then, since the air supply to the turbine is not normally simultaneously terminated, except by mechanism of the type herein provided or hereinbefore referred to, the pump will overspeed causing deflection or flowering of the impeller blades and possible destruction of the pump.

The present invention utilizes an arrangement in some respects similar to that disclosed in the aforementioned Lauck Patent No. 2,694,979, an overspeed control mechanism being provided comprising a valve 25 which is positioned in the air inlet 12 in such manner that it may he pivoted to reduce, or to shut off entirely if desired, the flow of air to the air turbine. Because of the arrangement of the air escape ducts on the discharge side of the turbine, it is not practical to mount the overspeed control valve in' the discharge duct side. Furthermore, it has been found that due to the momentum of the turbine itself, positioning of the valve on the air discharge side of the turbine results in a delayed response which may well defeat the purpose of the overspeed control. mechanism. Associated with the valve 25 is a. servornoter 26 which is arranged to permit opening of the valve in the normal operation of the pump but which, upon a surficient reduction of fluid pressure either at the inlet side or the discharge side of the impeller pump, will cause immediate movement of the valve toward closed position. In most cases, it is not necessary to shut off completely the air supply of the turbine, and it is adequate merely to reduce substantially this air supply in order to prevent overspeeding.

More particularly, the valve 25 comprises a disc-type or butterfly valve mounted on a shaft 27 journalled transversely in the air inlet passage 12 side walls. The valve may thus he supported in much the same manner as the air inlet control valve in a conventional automotive carburetor is mounted. The valve 25 may be mounted on the shaft 27 in balanced relation or in unbalanced relation, depending upon the response to air inlet pressure desired. Thus, where. as in the arrangement disclosed in the drawings, the valve opens by moving in a clockwise direction, it may be desirable to make the area of the lower half of tho alve slightly less than the area of the upper half, thereby causing the valve to tend to open in response to air pressure applied from the inlet l2. This may be conveniently done either by notching the lower periphery of the valve to reduce the area thereof exposed to air [low as compared with the upper portion or by drilling a hole through the lower portion of the valve, or by actually mounting the valve ecccntrically on the shaft 27.

Where the servomotor 26 is made to respond to fluid inlet pressure, it may be desirable to unbalance the valve 25 slightly in this manner so that the valve tends to open in response to air pressure applied thereto. However, because of the normal minimum fluid inlet pressure of approximately 5 p. s. i. the servemotor 26 will tend to open. the butterfly valve in to this inlet pressure. On the other hand, where the servomotor 26 is made to respond to pump discharge pressure as disclosed in the drawing, then it may be desirable to unbalance the valve so that it tends to close in response to air inlet pressure and is positively opened due to the discharge pressure applied to the servomotor 26. in this case, .it is then necessary either to make the valve smaller than the passage 12 or to provide a stop to prevent the valve from closing entirely so that some air flow will reach the turbine. A stop member threaded in the wall of inlet 12 and having its inner end positioned so as to be engaged by the right lower side of the valve 25 is satisfactory.

Rigidly secured to the shaft 27 at the end thereof projecting outside the far wall of passage 12 is the left end of a short lever or crank arm 30, which crank arm extends to the right and is connected at its right end through a lost motion connection indicated generally at 31 to the mid portion of a shaft 32 of the servomotor 26. Movement of the shaft 32 downwardly, as viewed in the drawing, causes clockwise rotation of the butterfly valve to cause opening of the valve. It will be evident that a lost motion connection of the type indicated is necessary due to the arcuate path of the right end of the short lever arm 3t} with respect to the linear path of the rod 32.

The servomotor 26 may be of the diaphragm type, as illustrated, or of the piston type as shown in the earlier filed Lauck application, and is suitably mounted on or associated with the housing of the air turbine driven pump, being located on the upper side thereof, as illustrated. More particularly, in the embodiment illustrated the servo motor comprises two mating cup-shaped housing members 33 and 34 having sandwiched therebetween a flexible diaphragm 35 of suitable material. The upper portion of the shaft 32 extends through an aperture 36 formed through the center of the lower housing mmber 34, the shaft 32 being journalled in the aperture 36 and its upper end being affixed to the central portion of the diaphragm 35. A helically coiled spring 37 disposed between the lower side of diaphragm 35 and the upper side of lower housing section 34 and encircling the upper portion of the shaft 32 normally urges the diaphragm upwardly, thus tending to hold the butterfly valve 25 in closed position.

Discharge pressure from the centrifugal pump is communicated to the upper side of the diaphragm 35 through a passage 40 which may be conveniently formed in the housing 10 of the pump assembly or alternatively may be provided by a suitable tube which is connected at one end to the discharge side of the pump and at its other end through a suitable port 41 formed in the upper housing section of the servo motor to the upper diaphragm chamber. Application of fluid pressure to the diaphragm, of course, tends to move the valve toward open position. Or as shown in Fig. 2 of drawings, pressure at the inlet of the centrifugal pump may be communicated to the upper side of the diaphragm 35 through a passage 40a conveniently formed in the housing or by a suitable tube which is connected at one end with the inlet side of the pump and at its other end through port 41. Application of fluid pressure to the diaphragm in this embodiment will tend to move the valve toward open position in response to inlet pressure. In connection with this latter discussion of Fig. 2, it is to be noted that this figure is identical with the embodiment shown in Fig. 1 except for the passage 40a communicatory with pump inlet pressure.

From the foregoing, it will be evident that with this arrangement, until pressure is generated by the fluid pump, the butterfly valve will not'be moved to open position to admit air to the air turbine motor. Conversely, until the air turbine motor is driven, the pump will not deliver pressure. In accordance with the present invention, there is provided, however, means for initially opening the butterfly valve to permit air to reach the air turbine. motor to drive the pump. This means comprises a solenoid arrangement designated generally at 42 and is employed for moving the shaft 32sdownwardly in response to energization of the solenoid. More particularly, the solenoid 42 may comprise a solenoid core 43 connected to the lower end of the shaft 32 and having associated therewith a solenoid coil 44 which may be energized through leads 45 and 46 connected through a. suitable switch 47 to a source 48 of direct current. The solenoid 42 is suitably mounted on or adjacent the air turbine driven pump.

areasea In using this arrangement, at the start of operation, the switch 47 is closed to energize the solenoid, thereby opening the butterfly valve an 1 permitting air to reach the air turbine motor. After the pump begins turning and generates discharge pressure, it is no longer necessary to energize the solenoid, as the pressure generated by the pump and communicated to the diaphragm 35 will hold the butterfly valve in open position so long as pressure is generated. However, upon a cessation of pressure due, for example, to exhaustion of the fluid supply, the pressure will immediately drop and the butterfly valve will close in response to the action of spring 37, thus preventing overspeeding of the mechanism.

The switch 47 may be located at a point remote from the solenoid and pump which is convenient. It will be apparent, too, that a double-acting solenoid may be employed whereby upon suitably energizing the soleoid, the shaft may be moved upwardly to close the butterfly valve and, thus, shut off the air supply to the turbine, thus stopping the pump.

Where herein the various parts of this invention have been referred to as being located in a right or a left position, or an upper or a lower position, it will be understood that this is done solely for the purpose of facilitaing a compact housing for said air driven fluid pump, an

air turbine rotor and a fluid pump rotor coaxially mounted in said housing, means drivingly connecting said air turbine rotor to said fluid pump rotor, means forming a part of said housing defining an air inlet portion to said turbine rotor coaxial with said turbine rotor, means forming a part of said housing portion defining an air outlet from said air turbine coaxial with said air turbine rotor, means forming a portion of said housing defining a fluid inlet portion to said fluid pump coaxial with said fluid pump rotor, means defining a fluid outlet portion from said fluid pump, said air inlet portion and said air outlet portion forming together a duct which telescopes and overlaps said connecting means in coaxial relationship, a control valve mounted in said air inlet portion and having means cooptrable therewith for regulating the supply of air to said air turbine rotor between a predetermined maximum value and a predetermined minimum value, said last-mentioned means including a fluid pressure responsive servomotor having a movable member linked to said control valve, passage defining means for connecting one side of said movable member to the fluid circuit of said -fluid pump whereby said movable member responds to the pressure in said fluid circuit at the point to which it is connected to urge said movable member toward the position of maximum value of air supply, said servomotor further including resilient means urging the other side of said movable member in the opposite direction whereby said control valve is moved toward a position of minimum value of air supply, and solenoid operated means connected to said control valve for shifting said control valve independently of the actuation of said servomotor.

2. An air driven fluid pump as claimed in claim 1 wherein said passage defining means connects said servomotor to pump inlet pressure whereby pump inlet pressure is applied to said servomotor.

3. An air driven fluid pump as claimed in claim 1 wherein said passage defining means connects said servomotor to pump outlet pressure whereby pump outlet pressure is applied to said servomotor to tend to urge said control valve toward the position of minimum air supply.

References Cited in the file of this patent UNITED STATES PATENTS 768,076 Rateau Aug. 23, 1904 1,078,986 Becker Nov. 18, 1913 1,305,365 Hopkins June 3, 1919 1,312,644 Raab Aug. 12, 1919 1,863,406 Hudson June 14, 1932 2,213,663 Berard Sept. 3, 1940 2,382,412 Grey Aug. 14, 1945 2,512,438 Ranzi July 20, 1950 FOREIGN PATENTS 23,418 Great Britain 1906 282,818 Great Britain July 19, 1928