Determination of Time Variant 1D-3D Temperature and Heat Transfer Distribution Inside the Cooling Jacket of a SI Engine Cooling System after Key-Off 2012-01-0642

This research work focuses on the unsteady heat transfer and temperature distribution over the engine cooling jackets. The efforts are gestated to generate the time-dependent effects of heat transfer from the combustion chamber to the cooling jacket of a 4-cylinder 1.6-L cam-profile switching system SI engine. The characteristic behavior of heat transfer to the coolant at lower speed (idle speed/traffic signal) or when the engine is shut down after driving the vehicle for a significant period manifests unstable temperature rise with respect to time. It has been observed that the temperature of the coolant inside the jacket rises up within a very short period of time. It can be a case due to the shut off of the actuators (coolant pump, fan) which helps the cooling system to take effect according to the demand of the thermal efficiency of the engine. A one-dimensional transient cooling system analysis and a 3D CFD analysis of the cooling jacket according to the emulated conditions of real case also shows that temperature instability with respect to time. But this high temperature of the coolant inside the jacket can affect the engine structure as it is a thermal load to the system and the coolant is motion less. As the thermal behavior has been observed as a time-dependent variable the challenge of removing that residual heat inside the cooling jacket, the time period can help to maintain the effective cooling system irrespective of the engine speed. The effect of time variant temperature changes have been observed both in normal thermostatic valve condition (i.e., 82±2°C to 96±2°C) as well as in nucleate boiling condition of isolated vapor bubble temperature zone. The authors found both the 1D transient and 3D CFD analysis quite reliable as they have devoted a significant amount of computational facilities to perform the analysis.