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Design modification of an exhaust valve in an automobile compressor
This study involved analysis of flow through a reed-type discharge valve of a positive displacement compressor used in the climate
control system of a car. An existing design of the valve produced a very high pressure within the compressor when the car was started. This high pressure resulted in breakage of the piston assembly and
costly replacement of the compressors.
A simple lumped-parameter based Flow Network Modeling analysis of the system showed that the discharge valve of the compressor was very restrictive. The reed
valve is a pressure-driven valve. It involves a metal leaf that deflects due to the pressure within the compressor to allow the fluid to exit. It was proposed to increase the flow gap at the maximum open
position of the reed valve by incorporating a chamfer in the face plate on which the leaf rests in its closed position. CFD analysis of the flow through the exhaust valve with the chamfer showed a
substantial reduction in the pressure within the cylinder. The angle and the size of the chamfer was then optimized using CFD analysis to obtain maximum reduction in the cylinder pressure while
preventing occurrence of any leakage through the valve in its closed position. The design modification was incorporated in the compressor design and it eliminated the damage to the piston.
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