This paper analyzes rotor profile and meshing law of twin-screw expander. Elementary area is calculated by meshing sequence method, and elementary volume is solved by integration. The influence of geometric characteristics such as torsion angle and internal expansion angle of male rotor on the thermal performance of twin-screw expander is studied. The results show the following: reasonably reducing internal expansion angle and positive rotor torsion angle can increase isentropic adiabatic power of twin-screw expander. Taking isentropic adiabatic efficiency as optimization goal, sequential quadratic programming algorithm is used to optimize the structural parameters of twin-screw expander, and the influence of leakage on its functional force is analyzed. Considering leakage effect, actual shaft power of twin-screw expander is 16.7 kW, the isentropic adiabatic power under ideal conditions is 21.3 kW, and the adiabatic efficiency is 78.71%.

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Spindle unit with various journal bearings is increasingly adopted in numerous machine tools. Due to overlooking the interaction between spindle and bearings in analysis and optimization leads to a less accuracy for simulating real work codition. In order to overcome this shortage, a practical coordination optimization strategy is perposed. Taking both bearing and spindle as subsystems of the overall system, using coordinator to account the interaction. Equivalent stiffness is adopted to ensure the analysis accuracy and save the computation time. An optimum design example is presented.

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