Abstract
High efficiency and low emission requirement for motor vehicles is becoming more and more urgent. Before the revolutionary of new energy (such as fuel cell) realized for practical use, the improvement of fuel consumption and emission is very important. Diesel engine has higher efficiency than the gasoline engine, but its NOx and particulate emissions are difficult to reduce. On the other hand, port fuel injection (PFI) engine produces low particulate matter (PM), but its efficiency is lower as compared to diesel engine. Gasoline direct injection (GDI) engine combines their advantages. However, GDI engine is difficult for motorcycle application. This study creates a new idea known as semi-direct injection (SDI) to overcome this problem. The conventional PGI system was used liquefied petroleum gas (LPG) injection with some modifications. The fuel injection timing is set during intake valve open so that the fuel could directly flow into the cylinder. A swirl intake air flow is designed to generate swirl, and hence to form stratified charge. The SDI engine will operate under lean conditions at 4500 rpm and 5300 rpm. Swirl generated by controlling airflow with one deactivated intake valve results in the improvement of thermal efficiency and reduction of HC emission, cyclic variations, ignition delay and combustion duration. The lean limit was extended and there was no increase in the NO level at lean mode.
Keywords: Liquefied Petroleum Gas; Lean Burn; SI Engine; Swirl Intake Air