In a screw compressor, both pressure pulsations in the discharge chamber and performance are affected by the design of the discharge port. A function for calculating the real flow area of the discharge port has been included in two analytical models for evaluating this. The predicted results, thus obtained, showed that this function varies according to the shape of the discharge port in a manner that influences the amplitude of the gas pulsations and hence the noise generated in the discharge chamber. With the aid of the model, a port shape was designed to minimise these pulsations and thereby reduce noise levels by up to 5 decibels. However, reducing sound emissions by this means, slightly lowered the compressor efficiency. An experimental programme was then carried out to investigate this and good agreement was obtained between the predicted and measured values.
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