Investigation of In-Cylinder Heat Flux in a Single Cylinder, 4 Stroke, Air Cooled, Spark Ignition Engine for Motorcycle Application

Heat flux measurements can provide much needed insight into the energy flow inside an IC engine, which is the key to optimizing its performance. This paper focuses on understanding the nature of heat flux curve and how it varies with varying load conditions, engine speed, Air fuel ratio and ignition timing in a single cylinder, 4 stroke, carbureted, air cooled, spark ignition engine for motorcycle application. In-cylinder heat flux was monitored along with wall temperature and cylinder pressure for motored operation as well as fired conditions. The difference between the motoring mode and fired mode was analyzed to separate out the effects of combustion. In general, the magnitude of maximum heat flux was found to increase with engine rpm and load when all other engine parameters remained constant. The heat flux was found to increase when a mixture setting closer to the stoichiometric value was used. While studying the effect of ignition timing, it was observed that the peak cylinder pressure and cylinder head wall temperatures increased as the ignition timing was advanced. However, there exists a particular value of ignition timing for which the heat flux peaked for any set of operating conditions and advancing the timing any further resulted in a decrease in the magnitude of peak heat flux regardless of the fact that the cylinder pressure continued to rise well beyond this point.