US2341974A - Supercharger control - Google Patents

Description

Feb.y 15, 1944.

K. A. BROWNE SUPERCHARGER CONTROL Filed May 14, 1941 Patented Feb. 15, 1944 UNITED STATES. PATENT OFFICE.

SUPERCHABGER CONTROL Kenneth A, Browne, Fairlawn, N. J.. assigner to Wright Aeronautical Corporation, a corporation o! New York Application May 14, 1941, serial No. 393,331 1s claims. (ci. 23o- 1114) I'his invention relates to centrifugai blowers and is particularly concerned with improvements factory variable angle diiuser, the vanes may be individually pivoted to a back plate and they may be jointly adjusted in their angular relation by a ring either linked to or'having a slotted connection with the several diffuser vanes. In the present invention, I contemplate using the latter mode of diffuser vane adjustment and in addition, utilize the master adjusting ring aS a side plate for the diffuser assembly, this side plate being axially movable to clamp the vanes from A l vibratory movement when no adjustment is in process, and furthermore, by clamping the plate into and out of engagement with the sides of diiuser passages which may be movable into andl out of engagement with the sides of diffuser vanes for the dual purpose of sealing the vanes and for clamping them against movement when they are adjusted to a position appropriate to a certain order oi blower delivery. A further object is'to provide automatic means for adjusting diiuser vanes' which is responsive in its operation to theY load coefficient under which the blowermay be operating.

Still another object is to provide a servo control system which shall be coincidentally'operable to unclamp the diiius'er vanes for adjusting movement and to move thevanes to a new position pf adjustment, after which reclamping and sealing oi the diiuser vanes may take place.

Centrifugal compressors or blowers obtain their highest adiabatic elciency over a relatively narrow band of load coeiiicient which may be replease of the clamping ring and a subsequent reresented by the expression Q/N, which represents the cubic feet of inlet air per impeller revolution, and the narrow eiliciency band is positioned relathe diiiuser vanes surrounding the impeller. Where iixed vanes are used, a narrow bandoi high efilciency is unfavorable where the compressoihas to operate at various Q/N values as is the case of superchargers for vinternal combustion engines, particularly where the supercharger has several drive ratios as in. the case 'of a multi-speed mechanically driven supercharger, or in the case of an exhaust turbine driven supercharger which has a wide range of impeller speed with respect to engine air de mand. Consequently, the nxed vane superchargers are designed to increase the band width at the expense of peak emciency so that reasonable eiliciencies are obtained under thev actual tive to Q/N primarily by the angular setting of against the sides of the diffuser vanes, interow between diiuser passages is substantially prevented, avoiding the loss of emciency which would occur as a result of leakage between the passages, and I further compensate for manufacturing tolerances in the assembly by this expedient.

utilize a servomotor which is responsive to changes in Q/N. This character of adjustment is obtained by making the vservomotor control responsive to changes in pressure rise across part.

of the impeller along with changes in the velocity of flow of the medium into the impeller eye.

Furthermore, I coordinate the operation of the clamping and adjusting ring with the vane adjusting servomotor in such fashion that vane adjustments are accompanied by a preliminary reclamping of the ring against the sides oi the diffuser vanes.

Further objects of the invention, and a clearer understanding of the provisions thereof will be obtained by reviewing the drawing in connection with the detailed description below.

In the drawing, i0 represents a rotary impellerl embraced by a housing il, part of which forms an axial impeller intake eye i2 blending into an impeller shroud i3. 'I'he impeller delivery 'is substantially radial, and delivers air or other nuid medium substantially radially and tangentially into an exit duct I4 through a varied diffuser i5. The latter comprises a plurality ot circumferentially spaced diffuser vanes i6 pivotally mounted for angular adjustment on pivot pins i'i secured in the housing Ii. Each vane il y carries-a pivoted block i8 spacedv from the pivot 'operating conditions, Variable angle diffuser vanes will allow oi.' maximum obtainable eiilciency i1 engaged in a substantially radial slot i9 in a clamping and adjusting ring 2i which is loosely piloted'at 22 on the outer rim 23 of the shroud `section of the housing il, the ring 2| being arl ranged for slight axial movement and for slight lover a wide range oi Q/N. To construct a satis? lo' circumferential' movement. 4In virtue oi `the -I In the control of diffuser vane adjustment, I l

2 axial movement of the ring 2|, it may be moved leftwardly into clamping engagement with the righthand side faces of the diffuser vanes I6, se-

curing the slderfaces of the vanes and clamping them against inadvertent angular movement on their pivots I1. Axial movement of the ring 2| toward the right frees the vanes for adjusting movement and by subsequent rotational adjustment of the ring 2|, the angular position of the vanes |6 is altered.

To afford the rotational adjustment of the ring 2|, I provide a shaft 25 having a crank 26, said shaft being carried'in a rigid bearing, not shown. The inner end of the shaft carries a dog 21 engaging a notch28 in the ring 2| so that, by turning the crank 26, limited rotational adjustment of the ring 2| is secured.

As will be seen in the lower part of the ligure, the ring 2l defines with the housing portion 23 an annular cavity 30 which under normal operating conditions will be under supercharger discharge pressure by leakage of the pumped fluid through the clearance at 22 or through apertures 3| in the housing element 23. The inner edge of the ring 2| is sealed to the outer rim of the shroud I3 by a suitable elastic gasket )32. The housing is provided withan annular chamber 33 communicating with the cavity 30 through drillings 34 whose aggregate area is somewhat greater than the leak area at 22 so that, by dumping the cavity 33 through the medium of a valve 36 vented to atmosphere at 31, pressure within the cavity 30 is relieved, thereby driving the ring 2| to the right in virtue of the intermediate pressure, greater than atmospheric but less than supercharger discharge, residing in the diffuser section I5.' Thus, when the valve 36 is opened, the ring 2| frees the vanes I6 and subsequent rotational adjustment of the ring by the crank 26 alters'the diffuser vane setting. Upon closing of the valve 36, supercharger pressure again builds up in the cavities 30 and 33 to move the ring 2| leftwardly into clamping and sealing engagement with the side faces of the vanes I6.

In order to prevent slamming of the ring 2l to the right, the puter surface of the ring 2| is provided with pads 39 overlying the drillings 34 so that as these -pads approach abutment with the housing section containing the drillings 34, flow of air from the cavity 30 is throttled and an air cushion is lformed to prevent contact of the ring with the housing. Y

To automatically control adjustment of the diffuser vanes, I provide a servomotor 46 which comprises a cylinder 4| containing a piston 42,

\ the piston being directly connected to the crank 26 by a link `43. The piston rod extends to the right as at 44 beyond the cylinder end and to it is securedl a lever fulcrum 45 through which passes a lever 46. The left end of the lever 46 is clevised to a servo valve 41 whose lower end is secured to a diaphragm 46 which divides the diaphragm chamber into an upper cavity 49 and a lower cavity 56. The cavity 49 connects through a pipe 6I to the supercharger impeller cavity through the shroud I3 while the lower cavity 50 connects through a pipe 62-to the supercharger inlet whereby the diaphragm, and consequently the valve stem 41 and .the left end of the lever 46 are subjected to a force proportional to the vpressure rise across part of the impeller.

- The right end ofthe lever 46 is pivoted on a stem 54'connected to a diaphragm 66 which divides its housing chamber into an upper cavity es and a iower cavity s1. 'rne cavity se con- 'turi 62 disposed in the impeller eye. Thus, the

force acting upon the diaphragm 55, and consequently upon the stem 54 and the righthand end of the lever 46, is proportional to the intake velocity of the supercharger.

The servo valve stem 41 upon vertical adjustment thereof, admits pressure fluid from a suitable source through a line 64 toeither the right or lefthand ends of the cylinder 4|, the left or right hand ends of the cylinder, respectively, being concurrently fconnected through the servo valve 41 to the interior ofthe servomoto;` 40 for subsequent drainage through a conduit 66. When the piston ||2 and the diffuser vanes are xed in position, the moments about the adjustable fulcrum 45 of the lever'46 must be equal. When any material change occurs in the blower pressure rise or in the velocity of flow into the impeller, an unbalance will obtain, changing the position of the servo valve 41 to admit pressure fluid to one side or the otherof the piston 42, urging change in adjustment of the diffuser vanes. Such change in adjustment will of course change the position of the fulcrum 45 which in effect acts as a balancing follow-up to secure a new equilibrium position for the servo motor, the attainment of such position of course centralizing the valve 41 and cutting oil motive fluid flow to the cylinder 4|.

The motive fluid feed passages 66 and 69 which establish connections respectively between the righthand end of the cylinder 4| and the valve 41, and the lefthand end of the cylinder 4| and thev valve 41, are bridged by a cavity 1| having restricted communicationat its ends with the passages 66 and 69, This cavity 1I is connected, by a conduit 12, to a cylinder 13 having therein a piston 14 acting upon the valve 36 which is normally urged to a closed position by a. spring 15. Admission of pressure fluid to the cylinder 13 will move the piston 14 leftwardly to'open the valve 36 while relief of pressure from the cylinder 13 will allow closing of the valve 36. Such opening and closing of the valve 36, as indicated previously, serves to unlock and lock the ring 2| respectively to alldw of' adjusting movement of the diffuser vane I6. Pressure in the line 12 is imposed as soon as the servo valve 41 moves in either direction to admit pressure fluid to the cylinder 4I so that as such pressure is imposed, the fLrst resulting function will be to unload the diffuser clamping ring 2| after which the piston 42 may eiect diiluser vane adjustment. When such adjustment is attained, the pressure on opposite sides of the piston 42 will equalize and there will be no flow through the cavity 1| and furthermore, the valve 41 will close and the pressure downstream of the valve 41 will drop to allow 'to form a supercharger therefor, engine hibri-v cating oil pressure may be utilized as a source of motive pressure for the servomotor 40.

It will be seen 4that the servomotor 46 is c08- nizant of the ratio Q/N and it shifts the diffuser vanes automatically vas dictated by the operating 'auen load coeicient. The optimum position of the` vanes I6 is directly proportional to the value 1 Q/N and therefore the control should move thel vanes linearly with respect to Q/N. In the ligure, the diaphragm55 is sensitive to the pressure differential created in the pitot-venturi 59,= 62.

The diaphragm 48 is sensitive to the pressure differential created by impellerrotation.` The diaphragms 55 and 48 are linked to the ends of the lever 4Q provided with the movable fulcrum 45, the fulcrumbeing movable in accordance with movements of the piston 42.'

The pitot-venturi 59, 62 is a device which produces a pressure differential proportional to DW where D is the density o the air surrounding the venturi and V is its v locity. Obviously, Q is directly proportional to V and consequently the pressure diierential Pv imposed on the diaphragm 55 is proportional to DQ2 whereby Q is proportional to the square root of Pn/D.

Neglecting the friction loss in flow of air through the impeller passages, the rise. in pressure Pc through a fixed increment of the impeller varies directly as DN2 wherefore N is proportional to the square root of Pc/D. It follows directly that ,Q/N is proportional to the square root oi?A Pv/Pc.- Now, the shifting fulcrum for the lever 46 produces a control effect which is not a linear function, but it turns out that this shifting fulcrum device when combined with the control forces proportional to Q2 and N2 produces a nearly linear control eiect on the vanes within the useable range both of'fulcrum position and the Qf'N ratio. f Y

In operation, the forces from diaphragms 5% and d8 must be in balance about the fulcrum t5; otherwise, the servo valve 41 will move to admit oil to the cylinder 4 I. causing it to move the fulcrum 45 to a, point creating balance of the forces on the diaphragms 55 and 48. The type of diaphragm shown in the figure doesnot have a constant piston area. This area increases with rise in the diaphragm and decreases with drop; consequently stability at the balance point is obtained inherently. If this stabilizing effect is inadequate. a spring may be added at the diaphragme which will urge the servo valve 4l to mid position. A definite overlap of valve closure is provided in the servo valve M to prevent continual movement and hunting of the control.

The ports adjacent the cavity` 'Il are so a1;- ranged that oil pressure acts on the piston 42 prior to its action in the cavity ll and on the piston 'M At all times when the forces in the` diaphragms 55 and 48 are balanced, no oil iiow exists through the servo valve $7, and the vent valve 36 remains closed.

Preferably, vby the proper` empirical adjustment of theqlinkage between the piston 42 nd the diuser, vanes I6, the latter are auto atically positioned to give maximum emciency from about 35% to/about 120% of the rat'ed air ow through the blower. care of all-normal running conditions of the blower when used as lan engine supercharger.

While I have described my invention' in detail4 in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modiiicationsmay be made therein without departing from the 'spirit or scope thereof. I aim 'in the appended claims to cover all such modi fcations and changes.

I claim as my invention:

ing, an impeller rotatably mounted therein and diiuser vanes disposed about the impeller periphery, means mounting said vanes for angular movement, an operator for moving said vanes jointly, and means movable against said vanes to secure said vanes 'against inadvertent movement when said operator is inactive, said movable means comprising a releasable ring clampable into engagement with all saidvanes.

2. In a centrifugal blower, a housing comprising a diffuser plate having circumferentially spaced pivots, a diiuser vane mounted on each pivot, a ring mounted for rotational adjustment relative to said plate with the diffuser' vanes disposed between said ring and plate, a sliding con. nection between said ring and each vane, each said connection being spaced from the pivot of the corresponding vane, whereby rotational ring adjustment affords joint adjustment ofthe angular position of the vanes upon said plate, and

means to move said ring axially into and out of clamping engagement with said vanes.

3. In acentrifugal blower having adjustable diffuser vanes, a member for adjusting the vanes jointly, a servomotor for actuating said member, a servo valve operable to control ow of operating fluid to and from the motor, means for operatlngsaid valve responsive to pressure rise across the blower and to rate of flow through the blower, a locking ring for the diiuser vanes, and means responsive to valving of uid to and from the motor to unlock said ring.

4. In a centrifugal blower having adjustable on the vanes, to clamp them from inadvertent movement, an annular cell'of whichsaid ring forms a wall the cell having restricted communlcation with the blower discharge whereby blower discharge pressure lacts upon said ring to hold This range of adjustment will take ysaid dump valve.

5. In a blower havinga variable speed impeller, means to maintainblower eiiiciency at a A high level over a wide speed range comprising concurrently tiltable diffuser vanes disposed.

around the impeller exit openings, means to tilt said vanes, a clamp normally holding said vanes in :dxed position, and means responsive to initiation of operation of said tilting means to release said vane clamp to allow of free movement of said vanes said clamp being actuated by fluid under blower delivery pressure and said releasing means comprising a device for dumping that fluid which operates said clamping means..

6.In Aa supercharger, an impeller, a backplate,

dimiser vanesvpivotally mounted on said backplate, a ring opposite said backplate with the diuser vanes disposed between said ring and backplate, rotatably and axially movable relative to thebackplate, a connection betweeneach vane Jand said ring whereby ring rotation changes diHuser vane tilt. and means to move -said ring axially into clamping and ,end-sealing engagement with said vanes.

7. In asupercharger, an impeller, a backplate,

4 diffuser vanes pivotally mounted on said vback-- plate, a ring opposite said backplate, rotatably and axially movable relative to the backplate and with the diffuser vanes disposed between said ring and backplate, a connection between each vane and said ring whereby ring rotation changes diffuser vane tilt, means to move said ringaxially into clamping and end-sealing engagement with said vanes, and automatic control means operable sequentially to unclamp said ring, to rotate said ring and to reclamp said ring.

8. In a supercharger, an impeller, a backplate, diiuser vanes pivotally mounted on said backplate, a ring opposite said backplate, rotatably and axially movable relative to the backplate, a connection between. each vane and said ring whereby ring rotation changes diffuser vane tilt, means to move said 'ring axially into clamping and end-sealing engagement with said vanes, and control means operable sequentially to unclamp said ring, to rotate said ring and to reciamp said ring, said control means being responsive in .its operation to changes in the blower delivery per impeller revolution.

9. In a superchar'ger, an impeller, variable an- Y gle diffuser vanes around the impeller, a bellows device subject to rise in pressure between the impeller intake and a point on the impeller upstream of the diiuser vanes, a bellows device subject to a pressure proportional to iiow through the superchargen. a beam connecting said bellows, a movable fulcrum fpr said beam, means for moving said fulcrum in accordance with diffuser vane tilt, and means operated by beam movements to vary the diffuser vane angles concurrently.

10. In a supercharger, an impeller, variable angle diiuser vanes ldisposed around the impeller, a'means controlled by'impeller speed, a means controlled by supercharger flow, a device actuated by said two means to alter the diffuser vane angle, and follow-back mechanism operated by the diiuser vanes to stabilize the control eect of said two means. A

11. In a supercharger having variable angle diffuser vanes, means to vary the angle of said vanes, a clamp member movable into vane engagement to clamp the vanes against movement, pressure responsive means to urge said vanes to a new position, and means responsive to incipient operation of said pressure responsive means to disengage said clamp member 'from said vanes.

12. In a supercharger, an impeller, a variable vane diffuser; a servomotor :for varying the vanes including an operating valve, means to move said valve in response to changes in the blower delivery per impeller revolution, a clamp for said vanes, and means responsive to initiation of servomotor operation to release said clamp, and to stopping of the servomotor to apply said clamp.

13. In a blower comprising a housing, an impeller rotatably mounted therein and diffuser vanes disposed about the impeller periphery, means mounting said vanes for angular movement, means movablel in one direction for adjusting said vanes and movable in another direction for securing said vanes against inadf vertent movement.

14. In a blower, a housing, an impeller rotatably mounted therein, pivotally mounted diffuser vanes disposed about the impeller periphery, and a member movable to adjust said vanes and upon completion of an adjustment movable to secure said vanes against inadvertent movement.

15. In a blower, an impeller, adjustable diffuser vanes mounted between two opposed walls, and means to adjust said vanes, one of said walls being axially movable into clamping and end sealing engagement with said vanes when said vanes are not being adjusted.

16. In a blower, an impeller, adjustably movable diffuser vanes mounted between two opposed walls at the impelleroutlet, means to move at least one of said walls into clamping and end sealing engagement with said vanes to lock said vanes against movement, and means automatically responsive to variations in blower performance and operable sequentially to effect unclamping of said vanes, adjustment of said vanes and reclamping of said vanes against adjustment.

17. In a. blower, an impeller, variable diffuser vanes at the impeller outlet, means responsive to fluid flow through the impeller, means responsive to the pressure differential lacross a portion of the impeller upstream from its outlet end, and control mechanism operated by said two means to adjust said vanes.

18. In a blower, an impeller, variable diffuser vanes at the impeller outlet, means responsive to the pressure differential across a portion of .the impeller upstreamirom its outlet end, and control mechanism responsive to said means for adjusting said vanes.

KENNETH A.l BROWNE.

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