Numerical Study On Heat Transfer In Micro Internal Combustion Swirling Engine

With the development of science and technology,portability has become an important index of the electronic and mechanical equipment.To make the electronic and mechanical equipment portable,the energy system should have high endurance life and energy density,however the conventional batteries cannot meet these requirements.Due to the high energy density and energy conversion efficiency,microscale engine based on hydrocarbon fuel combustion may be a good choice of the energy system for the portable equipment.The specific surface area of the microscale engine are much larger than that of the conventional engine,therefore the heat loss of the microscale engine are also higher than that of the conventional engine.To improve the efficiency of the microscale engine,it is necessary to study the process of the heat loss in the microscale engine.In this article,the heat transfer process in MICSE is studied by developing a numerical model.The work and results as are summarized below:(1)A simulation model is established to analyze the heat transfer in MICSE.Include instantaneous heat transfer models for gas working process in MICSE chamber,a cyclic transient heat transfer model and a steady one for the body.Simulation of heat transfer in whole machine realized by boundaries coupling iteration between the body and gas.(2)Through the steady simulation in the body of the engine,it is found that the body stay in high temperature,the rotor is more hot that chamber wall,and temperature on the outer surface of the body is uniform distributed;Through the cyclic transient simulation,it is found that,in the steady running state,the influence of the gas temperature fluctuation on the body is limited to the shadow layer of the chamber,and the temperature in the other parts of the body is constant in time.The rationality of using steady state with equivalent boundary instead of cyclic transient simulation for the body heat transfer during coupling simulation is verified.The coupling simulation of the heat transfer shows that the higher the engine operating frequency is,the higher temperature in body is.(3)The adiabatic working process of the gas is simulated,it is found that the combustion time is an important factor of the working cycle.(4)Working cycle in cylinder under different steady working conditions are solved by coupling iteration method.It shows that the heat transfer between the gas and the wall can promote the combustion process,by shorting the combustion time,the working circulation improved as result.In the cold starting process,the heat transfer is detrimental to the cycle.And the higher the operating frequency,the more obvious the effect of heat transfer on the working circulation.Based on the heat transfer simulation work,the heat balance of the whole machine in MICSE is calculated.Result shows that more than 80% of the heat enter the working cycle is taken out by surface heat dispersion of engine body surface and exhausts.