Geometric optimization of a hydraulic motor rotary valve

The performance of a hydraulic motor is strongly influenced by the timing, leakage, and friction of the valves connecting to the pressure and tank ports. For the application of a linkagebased hydraulic piston motor, a novel clearance sealed cylindrical rotary valve is introduced. A model of the cylinder pressure dynamics is formulated from the bulk modulus definition and solved using a variable-step Runge-Kutta stiff solver. Energy loss equations are developed and used to aid the creation of objective functions. A geometric optimization of the motoring efficiency is conducted based on coupled relationships: including throttling across the transitioning and fully open valve ports, viscous friction, and leakage, but excluding piston related losses. A simple genetic algorithm is used to obtain the optimized geometry, and a theoretical system efficiency greater than 97% is achieved. A multi-objective sub-population genetic algorithm is then used to generate Pareto Optimal solutions for different combinations of efficiency and output power. A sensitivity study of the valve timing and rotational frequency shows the starting angle of the pressure port and the width of the rotor orifice dominate the performance while the system frequency has negligible effects.