Study on flow field and deformation of scroll expanders with different profiles in waste heat recovery from vehicle engines

Scroll expanders can be integrated with organic Rankine cycle waste heat recovery systems for vehicle engines to boost the overall efficiency of waste heat recovery. In this work, geometric models of scroll expanders with three typical scroll profiles are established, including the fixed base circle involute profile, the variable-radius base circle involute profile (VRBCI), and the combined involute-arc-involute profile (IAI). Comparative investigations are carried out on structural features, internal flow field and scroll plate deformation, followed by the analysis of volumetric efficiency and isentropic efficiency for all three profiles. The results indicate that the leakage line length of the IAI profile is 19.11% shorter than that of the fixed base circle involute profile. Nevertheless, the IAI profile has a larger suction chamber volume and generates far more complex internal flow with distinct separation and vortex structures, accompanied by severe pressure fluctuations between adjacent working chambers. Fluid-structure coupled deformation results demonstrate that the tooth tip deformation of the IAI profile is consistently higher than that of the VRBCI profile along the entire profile length. The average coupled tooth-tip deformation of the IAI profile reaches 134 μm, which is 13.6% larger than the 118 μm deformation of the VRBCI profile. In terms of thermodynamic performance, the IAI profile achieves the highest volumetric efficiency of 82.4%, whereas the VRBCI profile achieves the optimal isentropic efficiency of 80.5%. Benefiting from a less turbulent flow and smaller structural deformation, the VRBCI profile exhibits the best comprehensive thermodynamic performance among the three profiles.