Development and design optimization of a single-acting electro-pneumatic variable valve actuator for a camless engine using experiments, mathematical theory and genetic algorithm

The paper describes the development of a novel, single-acting electro-pneumatic variable valve actuation (EPVVA) system for a camless internal combustion engine, and the optimization of its design variables and control parameters. Unlike the conventional cam-based system in which the valve events are tied up with the rotation of the crankshaft, the EPVVA can achieve an arbitrary specification of the motion of the engine valve as a function of time with a relatively simple control strategy. A mathematical theory for single-acting EPVVA system is formulated here, which captures the thermo-fluid-dynamics as well as the applied mechanics of the actuator cylinder and the engine valve. An experimental facility is developed to measure the valve motion in a single-acting EPVVA system. The theory matches well with the experiments. An example-application of binary-coded genetic algorithm produces the optimum design of an EPVVA system to be retrofitted to an SI engine which was originally cam-based. As compared to the cam-based actuation, the EPVVA system is shown to enhance the volumetric efficiency (by up to 63 %) while consuming similar level of power for actuation (0.012–0.117 kW at 1000–4000 rpm) (the EPVVA system will, however, considerably reduce the pumping loss in the engine thermodynamic cycle).