Patent GB-699668-A (GB)
Title: Dynamometer
Inventor: TUPPER KENNETH FRANKLIN
IPC: G01L3/20
Filed: 1951-10-02
Abstract: 699,668. Dynamometers. NATIONAL RESEARCH COUNCIL. Oct. 2, 1951, No. 22949/51. Class 106 (ii). Apparatus for measuring the power of a prime mover or other motor comprises a compressor operable by the motor means for indicating the speed of shaft rotation and the torque exerted on a driven part of the compressor by the drive shaft, means for dissipating heat developed during compression of the fluid, a main conduit for the fluid arranged to feed back at least a substantial part of the fluid from the discharge port, and means for maintaining the pressure in the main conduit substantially constant including a source of fluid pressure differing from that in the main conduit, and means providing an adjustable fluid flow passage between the main conduit and the source of fluid pressure. The compressor, Fig. 4, comprises an impeller 1 fixed to a shaft 2 supported by bearings 3 within a swung stator casing 4, which encloses the impeller 1 and supports an insulated scroll casing 5 into which fluid passes after compression through the passage 6. The stator and scroll casings 4, 5 are mounted on bearings 7 and pedestals 7A for restricted rotation about the axis of the impeller and shaft. The scroll casing 5 is surrounded by an outer casing 8 connected at one end 9 to a supply conduit and at the other to a return conduit 10 by an expansion type seal 10A. A torque meter, is attached to an arm 11 of the stator casing 4 and a tachometer is attached to the shaft 2 which is connected to the source of power by a coupling 12 so that with a selected density, temperature and flow of fluid to the compressor the power exerted may be calculated from the torque meter and tachometer readings. The stator casing 4 contains inlet guide vanes 13 controlling fluid entry and vanes 14 and straightening screens 15 for guiding the discharge preferably formed to eliminate a tangential velocity component in the fluid entry and discharge. In one embodiment, air at a given density enters the compressor through a supply conduit, compressed air is discharged through the return conduit 10 which passes through a heat exchanger, com. prising a coil through which passes air, water or other coolant, and returns to the inlet. Adjustable automatic valves connected respectively to a vacuum pump and a compressor control the initial density of the air and compensate for any variations due to leakage. In another embodiment steam of a given density flows from the supply conduit, through the compressor into the return conduit 10 equipped with an adjustable automatic valve for releasing excess steam to atmosphere, the remainder passing into a body of water maintained at constant level by a pump and adjustable valve. In the embodiment of Fig. 3, using a fluid such as dichloro-difluoro methane, an adjustable pressure valve 25 in the conduit 10 controls the flow of excess fluid to a heat exchanger 27 in which it is liquified and passed through conduit 28 to a body of liquid 29. The remainder passes through a conduit 30 and is released into the body of liquid 29 to vaporize sufficient thereof to maintain the predetermined density in the supply conduit 16. The valve 20 may be automatically controlled by the fluid pressure in the conduit 16. The apparatus may be used for testing aircraft engines, particularly propeller type gas turbines.