The fluid-thermal-solid coupling analysis of a scroll expander used in an ORC waste heat recovery system

In this research, a one-way fluid-thermal-solid numerical coupling model of a scroll expander for a waste heat recovery system was developed and used to investigate the deformation of the scroll pair. The pressure and thermal loads were firstly calculated by a CFD model, and the surface pressure and body temperature distributions of the scroll members were used as boundary conditions in the FEM model to obtain the deformation distributions of the scroll parts. Three time instants that may have significant adverse impacts on the maximum forces were selected to determine the most critical time for the occurrence of the maximum deformation of the scroll wraps. The results showed that the deformations induced by inertial force only occurred at the orbiting scroll tail, whereas the deformations in other regions negligible. At the time instants of t/T equaled to 13/15 and 1, the deformations induced by pressure loads had the opposite direction compared to that of the thermal loads and thus the two deformations canceled each other out and the coupling deformations decreased. The deformations induced by pressure loads were less significant than the thermal loads, therefore the coupling deformation was dominated by the thermal loads. The results also confirmed that the critical time at t/T equaled to 7/20 for the occurrence of the largest deformation resulted from the maximum axial forces that were exerted on the fixed scroll.