Investigation of a Mechanism Through a Transient Thermal Analysis and an Equivalent Steady-State Thermal Analysis

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The thermal analysis of a rotary engine mechanism requires taking into consideration the transfer of heat from the combustion gas to the engine parts, which include rotating parts and fixed parts, as well as the transfer of heat to the environment. During an engine mechanism rotation, the conditions of convective heat transfer are variable, and the surfaces of fixed parts exposed to combustion gas are continuously changing. In this case, the transient thermal analysis using the finite elements method is very complex because of the permanent modification of surfaces covered with combustion gas, as a consequence of mechanism rotation. Therefore, in the current paper, an equivalent model for steady-state thermal analysis is developed, so that the same results are obtained as in the long transient thermal analysis, but with significantly smaller requirements of time and computational resources. The transient thermal analysis performed for a large number of rotations, which provides the stationary thermal conditions of mechanism parts, is compared with the equivalent steady-state thermal analysis performed using the equivalent film coefficients and the equivalent convection temperatures. The distributions of fixed part temperature and heat flux obtained from the steady-state thermal analysis are compared to those obtained from the transient thermal analysis, and very good similarities are ascertained. In conclusion, the equivalent steady-state thermal analysis provides similar results, compared with the transient thermal analysis, but with significantly lower computational effort.