New Twin Screw Compressor Design by Deviation Function Method

The rotor profiles of twin screw compressors have a significant influence on the compressor performance. Three different rotor profile design methods are derived mathematically and their limitations are addressed. This dissertation presents the complete theory and algorithm of the deviation function (DF) method for the twin screw compressor design. This method is based on conjugate pair design and generates new twin screw compressor profiles from generating curves derived by the deviation functions. The deviation functions used in this research are composed of the Bezier curves. The partially overlapped three-segment third-order Bezier curve-based deviation function is proposed to achieve the goal of minimizing the blowhole area along with shorter interlobe sealing line length. The complication of combining curves as the generating curves and determining values of parameters of those curves are problems for the rotor profile designs of twin screw compressors in industry. Thanks to the adoption of Bezier curves for the deviation functions, these problems can be avoided when the rotor pro-files of twin screw compressors are designed in this study. In addition, it helps discover a more diverse range of designs and thus leads to the more universal optimal results. Those advantages are emphasized by showing a variety of design examples and the improvement for the industry applications. Moreover, the effects of the lead non-uniformity of the twin screw compressor are investigated and the results are compared to the twin screw compressor with constant lead in this research. It is found that the twin screw compressor with increasing lead tends to reduce the leakage, and thus, the volumetric efficiency of this kind is improved, especially in the practical operating conditions when the working gas has a significant tendency to leak out of the compression chamber of the compressor