Search Results

The purpose of this study was to investigate how autoignition leads to the occurrence of pressure oscillations. That was done on the basis of in-cylinder visualization and analysis of flame images captured with a high-speed camera using an optically accessible engine, in-cylinder pressure measurement and measurement of light emission from formaldehyde (HCHO). The results revealed that knocking intensity tended to be stronger with a faster localized growth speed of autoignition. An investigation was also made of the effect of exhaust gas recirculation (EGR) as a means of reducing knocking intensity. The results showed that the application of EGR advanced the ignition timing, thereby reducing knocking intensity under the conditions where knocking occurred.

Research on extended expansion engine was carried out in order to enhance thermal efficiency in general purpose engines. A four-jointed linkage was used between the connecting rod and the crank pin of a standard piston-crank system and provides an Atkinson thermo dynamic cycle. Thermal efficiency of an engine with a compression ratio of 12.4 and an expansion ratio of 18.1 was compared to an engine with a compression ratio of 9.4 and an expansion ratio of 13.6. Measured indicated thermal efficiency of prototyped engine operated by natural gas was 38.7%, a 2.6% increase, as predicted in the numerical simulation.