Development of Gasoline Direct Injection Engine for Improving Brake Thermal Efficiency Over 44%

Abstract

This study demonstrates the effects of technologies applied for the development of a gasoline direct injection (GDI) engine for improving the brake thermal efficiency (BTE). The engine has relatively high stroke to bore ratio of 1.4 with a displacement of 2156cm3. First, since compression ratio is directly related to the thermal efficiency, four compression ratios were explored for operation without exhaust gas recirculation (EGR). Then, for the same four compression ratios, EGR was used to suppress the knock occurrence at high loads, and its effect on initial and main combustion duration was compared. Second, the shape of intake port was revised to increase tumble flow of incylinder charge for reducing combustion duration, and extending EGR-stability limit further eventually. Then, as an effective method to ensure stable and complete combustion for EGR-diluted stoichiometric operation, the use of twin spark ignition system is examined by modifying both valve diameter of intake and exhaust, and its effect is compared against that of single spark ignition. In addition, the layout of twin spark ignition was also examined for the location of Front-Rear and Intake-Exhaust. To get the maximum BTE at high load, 12V electronic super charger (eSC) was applied. Under the condition of using 12V eSC, the effect of intake cam duration was identified by increasing from 260deg to 280deg. Finally, 48V eSC was applied with the longer intake camshaft duration of 280deg. As a result, the maximum BTE of 44% can be achieved for stoichiometric operation with EGR.

Thermal efficiency optimization of a single cylinder gasoline engine based on active jet ignition

“…However, these engines face challenges in achieving brake thermal efficiencies of 45% and higher due to high exhaust emissions and cooling losses. [1][2][3][4] Additionally, knock can occur at high or even medium engine loads under stoichiometric combustion, which limits the engine's thermal efficiency. Lean burn, on the other hand, is a promising technology for improving thermal efficiency and reducing knock tendency.…”