A Study on Adapted Similitude Modeling Method of Turboexpander With Different Gas Working Fluids

The study on similitude modeling method of turboexpander with different working fluids is not only the key technical means and necessary method for the research and development of turboexpander with special working fluids but also an effective way to further expand the application scope of a turboexpander. In this paper, an adapted similitude modeling method (ASMM), which is based on dimensional analysis, actual characteristics of real gas, and seven similitude criteria, is proposed. Based on modeling criterion pi, the new similitude modeling relationship of turboexpander with different gas working fluids is obtained based on rotational speed, inlet total temperature, specific heat ratio, and gas constant. Aiming at the ASMM, the similitude modeling performance of turboexpander with air, methane, CO₂, and helium is verified by using the computational fluid dynamics method. The results show that the modeling effects on aerodynamic performance are well predicted in a wide range including the design point (expansion ratio 2.9 similar to 5.0), and the errors of the total-to-total isentropic efficiency, relative equivalent mass flow rate, relative equivalent shaft power are less than 0.74%, 1.94%, and 1.69%, respectively. Methane and CO₂ have the best modeling performance, their errors of efficiency, relative equivalent mass flow rate, and relative equivalent shaft power are all less than 0.5%; Furthermore, the ASMM also has pinpoint accuracy with the prediction of the internal flow field, which provides a good idea for further research on special working fluid turboexpander and an approach to expand the application scope of turboexpanders.