A 125 cc 4-valve engine was retrofitted by designing a control plate to enhance the swirl of intake flow at low load. This design combined high swirl and injection during intake valve opening to produce stratified charge, which is called SDL The lean limit was extended to 1.7 of lambda. The engine was tested in a low-load region, which was composed of most operation points of the ECE-40 driving cycle. A complete engine performance map under half-load operation was conducted for comparison between an SD1 and an original SI engine. Measurements of various combustion characteristics and emissions on the target engine have led to the following conclusions: The design criteria of SDI are high swirl of intake flow, fuel injection during intake valve opening, and better atomisation of fuel spray. The objective is to produce stratified charge with a richer mixture around the spark plug. Injection timing at 80 CA ATDC of intake stroke has the lowest COV for SDI engine; it may indicate that injection timing has considerable influence on combustion stability. The injection timing near the middle point of intake stroke is a good choice. The lean limit of SDI system has been extended to 1.7 of lambda. A homogeneous charge SI engine cannot achieve such a lean mixture; therefore, it must have the effect of charge stratification. The MBT timing of original PFI engine is indeed higher than that of SDI, plus shorter combustion duration and a better HRR result with SDI engine. The SDI's stratified charge and swirl motion are the reasons for these results. In a part-load region, which consists of most of the engine operating points of the ECE-40 driving cycle, SDI performs quite well. By taking the average of all testing points in this region, BSFC and BSNOx are reduced by 11.3% and 32.0%, respectively, and BSCO decreases tremendously by 92.9%. However, BSHC increases by 47.7%. Therefore, based on technical view points, SDI engine is a real possibility for motorcycle engines. Future work should study strategies for controlling torque at lean mode, as well as controlling the transient stage between stratified mode and homogeneous mode.
Application of semi-direct injection for spark-ignition engine
Anwendung der Semi-Direkteinspritzung beim Otto-Motor
International Journal of Vehicle Design ; 54 , 4 ; 356-370
2010
15 Seiten, 13 Bilder, 2 Tabellen, 12 Quellen
Article (Journal)
English
Application of semi-direct injection for spark-ignition engine
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