Study on novel cross-axis conical screw rotors with large built-in volume ratio for twin-screw expanders used in energy recovery systems

The twin-screw expander is widely used in many low-grade energy recovery systems. Its built-in volume ratio has a crucial impact on the system performance. Large built-in volume ratio can expand both the application and scope of the twin-screw expander, and can improve the efficiency of the power generation cycle as well. In this study, a novel pair of intermeshing cross-axis conical twin-screw rotors (CCSRs) with large built-in volume ratio and large expansion ratio for the twin-screw expander was proposed. The conjugate meshing of CCSRs can be achieved by using spherical-sectional profiles. Geometric performance of the proposed CCSRs was studied. Moreover, a thermodynamic model and numerical simulations of the working process of the proposed cross-axis conical twin-screw expander (CCSE) were established, and the working performance and thermodynamic characteristics during the expansion process were analyzed. Study results indicate that the proposed CCSRs exhibit a larger built-in volume ratio, and the corresponding twin-screw expander has a larger expansion ratio than that of the traditional one. The contents will be beneficial to the improvement and development of the twin-screw expander and energy recovery systems.