Mathematical modeling of twin screw compressors with special attention to gas pulsations in three-dimensional gas paths
Abstract
Geometric and thermodynamic simulations of a twin screw compressor were carried out to determine the flows through the suction and discharge ports, and to calculate the compressor performance. As flows through ports are oscillatory in nature, gas pulsations are excited in the suction and discharge manifolds. The thermodynamic activity and the gas pulsation interact with each other during the process. Gas pulsations not only alter the gas conditions inside the compression chamber and thus change the performance of the compressor, but also cause the compressor structure to vibrate and radiate noise. The acoustic characteristics of the suction and discharge manifolds were described in terms of pressure and volume flow transfer functions. The fundamental physics of gas oscillation was studied by use of a lumped parameter model and a one-dimensional continuous model. However a finite element model was employed in this research to deal with the complicated geometry and large size of the three-dimensional enclosure of a real screw compressor. Results of the mathematical modeling and computer simulation, were checked against the measured data and showed good agreement. Influences of gas pulsation on the compressor performance and the vibration and noise generation were studied. These studies included the calculation of the natural frequencies of the compressor shell and measurements of the acceleration and noise spectra. Acoustic properties of the steel wool demister in the discharge manifold were also measured and their influence was studied. Effects of the over/under pressure condition and the volume ratio unloading mechanism on the compressor performance and gas pulsation were investigated.
Degree
Ph.D.
Advisors
Soedel, Purdue University.
Subject Area
Mechanical engineering
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