TM 9-4310-394-13Section III. PRINCIPLES OF OPERATION1-12. THEORY OF OPERATIONS. The ACU is a self contained, transportable, diesel engine driven centrifugal aircompressor designed for compressing air and delivering it as needed. It consists of a two stage reciprocating aircompressor, a four stroke air cooled diesel engine, and a chassis for the mounting of the ACU components and toprovide a means of transporting the ACU. The ACU performs its operations in the following manner.a. AirCompressor. The air compressor operates to compress air through the use of a two stage compressingsystem. This two stage system consists of two complete piston assemblies which are mounted internally to thecompressor crankshaft.As the compressor crankshaft rotates, the first stage (low pressure) piston moves downward to draw outside air. This airis passed through a filter, through a set of valve plates, and then into the cylinder area of the first stage piston. As thecompressor crankshaft continues to rotate, the first stage piston moves upward to compress and push out this air throughthe valve plates and into an intercooler tube which transports and cools the partially compressed air into the cylinderhead of the second stage piston.This second stage (high pressure) piston is also attached to the compressor crankshaft. As the second stage pistonmoves downward, it draws in the air partially compressed by the first stage piston. When the second stage piston movesupward, it further compresses this air and then forces the air through an exit port of the cylinder head of the compressor.The air is transferred from this exit port to a receiver tank by means of a discharge tube. The receiver tank stores thefully compressed air until needed by the operator.b. DieselEngine. To cause the crankshaft inside the air compressor to rotate, the compressor flywheel mountedon the air compressor crankshaft is driven by a V-belt attached to a pulley connected to the output shaft of a dieselengine. This diesel engine is equipped with both an electrical starter and a manual recoil starter for starting the engine.The operating speed of the engine is controlled by a throttle control mechanism which is factory set to provide a constantoperating speed for the air compressor. The electric starter can be powered by a 12 volt direct current battery (notfurnished with the ACU).1-5/(1-6 Blank)
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