Performance Evaluation for Positive Displacement Motors by Combining Fluid-Structure Interaction Simulations and Experiments

Summary The aim of this study is to propose a method for evaluating the performance of positive displacement motors (PDMs) from the perspective of robustness and energy conversion efficiency. Monitoring contact force and leakage is challenging when a steel rotor driven by liquid undergoes planetary motion within the rubber lining of the stator. A 3D model with a nominal diameter of 172 mm is established, along with a flow field of the same outer diameter as the stator. The constitutive parameters are determined according to the two-parameter Mooney-Rivlin model. After merging the overlapping nodes of the rubber lining and steel housing, the degrees of freedom are constrained from the exterior of the stator. Four-step loads are applied in ascending order. The average difference in overall efficiency between the experimental results and the simulation of the same model PDM is 1.58%. The sequential simulations include three sets of nine variables: lead (800 mm, 914.4 mm, 1200 mm), interference fit (0.1 mm, 0.2 mm, 0.3 mm), and rubber hardness (70 HA, 80 HA, 85 HA). Contact force differentials on each sealing band are calculated before and after stable operation. The reliability and stability of the cavities are assessed using the mean and variance of the force differentials. Efficiencies after each load stabilization are calculated to compare performance. For loads other than 200 N·m, the overall efficiency of the PDM with the optimized parameter combination increased by 2.98%, 0.27%, and 2.32%, respectively. Finally, this parameter combination is applied to a curved profile PDM. For loads other than 200 N·m, the overall efficiency increased by 3.22%, 0.89%, and 5.14%. This method, which combines the fluid-structure interaction (FSI) with an analysis of robustness and efficiencies, can be used to analyze the strengths and weaknesses of different parameter PDMs and to assess the performance of different profile motors.