The gas-dynamic unsteadiness effects on heat transfer in the intake and exhaust systems of piston internal combustion engines

This article presents the results of experimental research into the gas-dynamic and heat-exchange parameters of gas flows in the intake and exhaust pipelines of piston ICEs (internal combustion engine) taking into account the nonstationary nature of the gas exchange processes. Some characteristic times of transient processes (recovery time and relaxation time) are established during the gas flow recovery in round pipelines. Based on the obtained data, the degree of non-stationarity or unsteadiness of the gas-dynamic processes in piston ICE pipelines can be established. It is demonstrated that there are two types of resolution for gas-dynamic unsteadiness. It is established that unsteadiness reduces the instantaneous local heat transfer intensity in the pipelines of piston ICEs by 1.3-2.5 times. A method is proposed for taking the thermomechanical unsteadiness into account in thermal calculations by applying the heat transfer mobility correction coefficient for classical equations that are used to calculate the local heat transfer coefficient.