Effects of variable valve timing on the air flow parameters in an electromechanical valve mechanism-A cfd study

In this study, volumetric efficiency, air flow rates, and cylinder pressure values were experimentally determined for a single-cylinder spark-ignition engine having conventional camshafts. Cold flow analysis was carried out using the computational fluid dynamics (CFD) method with importing combustion chamber and flow volumes of the suction and exhaust ports of the engine. After validating analyzes results with experimental data for different revolutions (RPMs), analyses were repeated using electromechanical valve mechanism (EMV) cam profiles. In the case of using EMV, advancing the intake valve opening time and advancing and retarding exhaust valve closing were simulated with CFD software. Simulations where different cam profiles were used for each revolution, volumetric efficiency, in-cylinder pressure, swirl and tumble ratio, in-cylinder total mass, and air flow rates in the cylinder were investigated numerically. As a result of the obtained data, it was seen that the use of EMV at low RPMs caused a decrease in the volumetric efficiency according to the conventional camshaft valve lifting amount and timing and it caused an increase in the volumetric efficiency at high RPMs. According to the results, it was understood that the effect of intake valve closing time is important on volumetric efficiency. Additionally, this study shows that the swirl ratio is significantly affected by EMV system.