Experimental study of heat transfer coefficient in a spark ignition engine (1st report, relation between gas velocity and heat transfer coefficient under motored conditions)

Many studies have been made on heat flux or heat transfer coefficient in internal combustion engines to increase thermal efficiency or to solve thermal loading problems. However, there are few cases in which heat flux of engine walls and gas velocity in a cylinder were measured under the same experimental conditions. In this study, gas velocity was varied by changing the setting angle of an intake shrouded valve. Heat flux was measured by the thin film thermocouple transducers and gas velocity was measured by a hot wire anemometer under motored conditions. Heat transfer coefficient was calculated from measured heat flux and physical properties at the cylinder gas temperature. As a result, the relationship between gas velocity (Re number) and heat transfer coefficient (Nu number) was found to be subjected to the equation Nu=a+b · Reⁿ.