Research On Heat Transfer Characteristics Of MSRE And Its Effect On Overall Performance

Research group proposed a new catch-up micro swing rotor engine(MSRE),which has the characteristics of high relative thermal efficiency and large weight-to-weight ratio.As the engine size decreasing,area-volume ratio increases and the heat exchange between the working fluid in the cavity and the contact wall increases.Then the heat loss increases and the effect of the heat transfer on MSRE cannot be neglected.Based on this problem,this paper studies the heat transfer law and parameter optimization of MSRE in order to realize the regulation and performance optimization of the engine temperature field.The main works and conclusions are as follows:Based on the working principle of MSRE,heat transfer model of the working fluid-cavity-environment is established,and the thermodynamic model of the working process of the engine is improved.Considering the heat exchange between the working fluid and the cavity,the initial process parameters and the performance of MSRE are calculated.The result provides the foundation for the subsequent calculation of the thermal load on the cavity and the study on the performance change of MSRE.The equivalent cycle average temperature and heat transfer coefficient of the working fluid in the cavity are obtained as the boundary conditions for calculating the temperature field of the cavity by processing the preliminary calculation results.The temperature distribution of the cavity shows that the location of the compression stroke is the low temperature area,about 840K.The combustion/expansion and exhaust stroke locations are the high temperature area,about 1140K.Rotor piston temperature is more uniform,about 1010K,and the top of the rotor piston temperature slightly higher than the hub.The deformation of the cavity and the rotor piston under the heat load of the temperature distribution is large,and the deformation at the sharp corner is up to 385?m.The inner wall expands to the outer periphery,but the overall deformation is up to 201.1?m and smaller than the deformation of the rotor piston,which up to 238?m.The actual work of the engine will appear the phenomenon of piston scraping.Based on the improved heat transfer model and the temperature field of the cavity,the performance of the engine is simulated under the more realistic conditions,which considering the heat exchange between the working fluid and the contact surface.It is found that the compression is the most affected when the heat transfer is taken into account.Due to the heat transfer from the wall to the working substance,the wage temperature in the compression process increases significantly and the compression loss increases.Output power from the adiabatic conditions of 2.818kW drops to1.700kW,and the thermal efficiency from the adiabatic conditions of 17.288%drops to 12.061%.At the same time,it is found that the thermal efficiency increased by 0.5%point and the relative increase rate is 4.2%.In addition,it is also found that the heat exchange by the leakage flow is relatively smaller than the heat exchange between the wall and the working fluid.Finally,it is found that the smaller the size,the larger area-volume ratio,and the power declines greater than the size of the cubic relationship.The performance of MSRE drops significantly.Comparing the performance of MSRE at different frequencies,the thermal efficiency relative decline caused by the leakage at low frequency is 35.57%,which is slightly larger than that caused by the heat transfer,about 30.06%.However,the heat loss at high frequency is greater than that caused by leakage.Power is more sensitive to the frequency,compared with thermal efficiency.Through reasonable parameter optimization by reducing the cavity wall temperature of 200K and the convection heat transfer coefficient of 50W/(m~2·K),the performance of MSRE is greatly improved.The maximum power is up to 2.818kW at the frequency of 100Hz and the maximum thermal efficiency is up to 17.703%at the frequency.Based on the existing prototype,the motion feasibility is verified by rotating with motor.The static frictional resistance moment is about 0.15N·m,and the binding performance curve shows that the self-running speed is about 500rpm.The test results show that the ignition continuity is the best when the equivalence ratio is 0.8.The test parameters are measured by using the sectional coverage measurement.It is found that the temperature and the pressure of working fluid in the combustion/expansion process are quite lower than the theoretical value.The impact of irreversible factors is significantly large.