Investigation of variable valve timing with electromechanical valve mechanism effects on air flow parameters

Due to the mandatory emission restrictions imposed on the Internal Combustion Engines, R & D work is getting more important each day. These studies focus on improving parameters such as combustion efficiency, power, torque, and emission of internal combustion engines. In the past, for the first step was to switch from single-valve systems to double-valve systems to increase the amount of intake air at the combustion chamber. In internal combustion engines, the valve timings are optimizing for the ideal operating conditions of the engine and operating with a constant opening and closing timing at all revolutions. For this reason, the ideal opening times of the valves differ at cycles apart from optimum cycle, and the expected volumetric efficiency cannot be obtained. To increase the volumetric efficiency studies are continuing on variable valve timing. In recent years, with the development of electronic control units studies are focusing on camless engine technology where active valve control can be done more efficiently. 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 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, analyses repeated using electromechanical valve mechanism (EMS) cam profiles. In case of using EMS, the advancing intake valve opening time and exhaust valve closing advancing and retarding are simulated with CFD software. Simulations where different cam profiles 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 EMS at low revolutions decreased the volumetric efficiency according to the conventional camshaft valve lifting amount and timing, and increased the volumetric efficiency at high revolutions. 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 swirl ratio is significantly affected by EMS system.