Thermal-mechanical characteristics of stationary and pulsating gas flows in a gas-dynamic system (in relation to the exhaust system of an engine)

Abstract

It is a relevant objective in thermal physics and in building reciprocating internal combustion engines (RICE) to obtain new information about the thermal-mechanical characteristics of both stationary and pulsating gas flows in a complex gas-dynamic system. The article discusses the physical features of the gas dynamics and heat transfer of flows along the length of a gas-dynamic system typical for RICE exhaust systems. Both an experimental set-up and experimental techniques are described. An indirect method for determining the local heat transfer coefficient of gas flows in pipelines with a constant temperature hot-wire anemometer is proposed. The regularities of changes in the instantaneous values of the flow rate and the local heat transfer coefficient in time for stationary and pulsating gas flows in different elements of the gas-dynamic system are obtained. The regularities of the change in the turbulence number of stationary and pulsating gas flows along the length of RICE gas-dynamic systems are established (it is shown that the turbulence number for a pulsating gas flow is 1.3-2.1 times higher than for a stationary flow). The regularities of changes in the heat transfer coefficient along the length of the engine’s gas-dynamic system for stationary and pulsating gas flows were identified (it was established that the heat transfer coefficient for a stationary flow is 1.05-1.4 times higher than for a pulsating flow). Empirical equations are obtained to determine the turbulence number and heat transfer coefficient along the length of the gas-dynamic system.