Research Of Output Torque Characteristics Of Stirling Engine With Working Fluid Leakage

Dish solar power generation system has high power generation efficiency,in which Stirling engine is the core equipment to convert solar energy into electric energy,and its photothermal conversion performance determines the generation efficiency of the whole generation process.However,due to the harsh working conditions of Stirling engine,the working temperature up to 1000 K,is a major test for Stirling to launch the performance of sealing parts.Inside the Stirling engine,the working fluid flows back and forth in the expansion cavity,heat pipe,regenerator,cold pipe and compression cavity for heat transfer,the size and direction of the working fluid velocity change at all times,and the moving parts of the Stirling engine,so the gap between the components is stimulated,which leads to the leakage of the internal working fluid of the hot cavity and the cold cavity at the upper and lower ends of the piston.Working fluid leakage will affect the output torque change of Stirling engine,resulting in the output power is not constant.Based on this question,the third-order nodal analysis model of the four-cylinder double-acting Stirling engine is established,and the effect of leakage on the output torque of the main shaft is analyzed.Specific research processes are as follows:Firstly,the third-order nodal analysis model of the leak-free Stirling engine is established to analyze the distribution of pressure and temperature in the four-cylinder and the torque characteristics of the main shaft.The results show that the temperature varies between950～1000 K and 320～400 K,and the pressure varies between 10～19 MPa.Under the condition of no leakage,the spindle torque varies from 250 to 265N?m.Secondly,a two-dimensional model of Stirling engine is established,and the validity of the third-order leak-free node analysis model is verified.The results showed that:(1)In the expansion cavity,the difference between the maximum pressure error t=0.023s is 0.85MPa,the error is 5.2%,and the difference between the maximum temperature error t=0.02s is 3%.(2)In a compressed cavity,the difference between the maximum pressure error t=0.023s is0.85MPa,the relative error is 5.2%,and the difference between the maximum temperature error t=0.02s is 28 and the error is 6.5%.Although there is some deviation between the third order analysis method and the results of Fluent calculation,it also shows the validity of the third order leak-free node analysis method within a reasonable range.Finally,based on the leak-free third-order node analysis model,the working fluid leakage and supplementary model of Stirling engine is established.The piston leakage,piston rod leakage and the change of spindle torque after working fluid supplement are analyzed.The results show that:(1)Both piston rod and piston leakage will cause the fluctuation of output shaft torque,and the range of torque variation is 247～267 and 246～268N?m respectively,which will obviously cause the spindle output torque to fluctuate.(2)Torque comparison of piston leakage area at 0cm~2,0.002cm~2,0.004cm~2,0.006cm~2and 0.008cm~2,respectively.As the piston leakage area increases,the torque fluctuations become larger.When the piston leakage area is 0.008 cm2,the fluctuation range of torque is 235～270N?m,the amplitude reaches the maximum value of 35N?m.(3)With the addition of the working fluid supplement,the torque variation range is 247～268N?m,indicating that the working fluid supplement can compensate for the power loss caused by leakage and reduce the vibration of the engine.