Expander which drives an electromotor to generate electricity is the core of low-temperature waste heat
recovery equipment. At present, domestic expanders on waste heat recovery system mostly arise from exploration,
research and improvement on the existing models of screw expanders and scroll expanders, which have complex
structures and high costs. For overcoming the shortcomings mentioned above, a new roots-type power machine is
researched and designed. In this paper, the working fluid of low pressure waste heat is stimulated according to both the
different operating conditions and the different intake and exhaust pressure and flow, and the changing process of internal
flow field is simulated over the time period using dynamic mesh technique when the power machine is in rotating work.
Besides, the pressure field, velocity field and graph of mass flow rate are analyzed with the simulation results, thus
obtaining the conclusion of optimum operating conditions of the roots-type power machine to guide selection method in
practice, that is, selecting appropriate roots-type power machines according to different types of waste heat in industrial
production. These efforts can therefore provide strong theoretical guidance and foundation for the subsequent engineering
practice of waste heat recovery system on roots-type power machine, and can have a profound impact on further recovery
and utilization of low-grade energy.