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Serving as a core component, the performance of the hydraulic transformer (HT) directly affects the energy-saving performance of the common pressure rail (CPR) system. The HT is capable of both amplifying and reducing pressure without throttle loss, in which the pressure ratio is a critical parameter controlled through adjusting the torques acting on the rotors. However, our understanding of it relies on simplified models due to the complicated operation mechanism. This study focuses on the pressure ratio characteristics of the novel double rotor hydraulic transformer (DRHT). Firstly, the key influencing factors of the DRHT are acquired through theoretical analysis. Secondly, a dynamic model of the DRHT is established allowing for mechanical and fluid properties. Thirdly, a specially designed DRHT prototype is manufactured and the test bench is built up to verify the model. The experimental and numerical results show that the pressure ratio varies nonlinearly with the control angle especially when the control angle is greater than 10 degrees, while it changes almost linearly with the increasing rotating speed. The test results are consistent with the simulation results, which credit the mathematical model feasible and effective. The parametric study show that the augment of the A slot wrap angle on the valve plate could enhance the driving torque, as a result larger pressure ratio can be acquired. The enlargement of the B slot on the valve plate could make the variation of the pressure ratio more linearly. The current work is also significant for further design and the application of the DRHT.

Served as a core component, the performance of the hydraulic transformer (HT) directly affects the energy-saving performance of the common pressure rail (CPR) system. The pressure reduction process of HT is accompanied by an expansion of the plunger cavity, which can result in a steep pressure drop and lead to cavitation under certain working parameters. In order to enhance the performance, a double rotor hydraulic transformer (DRHT) is proposed, and systematic analysis of the pressure reduction process in DRHT is provided by the CFD simulation and experimental test. The CFD model is based on the dynamic mesh method considering both cavitation and turbulence. The experiment is carried on with a specially designed prototype and four kinds of valve plates. The results show that the transient pressure decreases sharply with increasing rotating speed, and minimum transient pressure is reached at the control angle of -30 degrees. The damping groove can deter the volume expansion effect and thus enlarging the working range, but the volume loss will be incurred. The results of the parameter study show that the damping groove with the length 4 mm and the depth 3 mm can avoid the excessively low transient pressure occur while maintaining low volume loss. The simulation curves have good consistency with the test results, which credit the numerical method feasible and effective. The current work is also significant for further design and the application of the DRHT.