Research on Effect of Center Direct Injection in Natural Gas Lean-Burn Engine

- Thermal Efficiency Improvement of Natural Gas Engine -

Abstract

Center direct injection with supercharging engine is known as the method for improvement of engine output. To improve the thermal efficiency of the automotive spark-ignition engine with CNG, we applied lean combustion by using center direct injection. We tried to improve thermal efficiency by using single cylinder engine, and furthermore, we analyzed the engine data by fundamental experiment with Rapid Compression Machine (RCM) and numerical calculation. By optimization of the toroidal combustion chamber and swirl port and injection pattern and injection pressure, it was possible to optimize the air-fuel mixture distribution around spark plug. Therefore, it was possible to expand the lean limit A/F. Direct injection improved thermal efficiency compared to conventional port injection.