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

Abstract

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 turboexpander. In this paper, a new similitude modeling method (NSMM), which is based on dimensional analysis, actual characteristics of real gas and seven similitude criteria, is proposed. On the basis of modeling criterion p4, the new similitude 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 NSMM, the similitude modeling performance of turboexpander with air, methane, CO2 and helium is verified by using 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 2.9~5.0), 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 NSMM also has pinpoint accuracy with the prediction of 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.