Analysis Of Thermo-mechanical Coupling Effect Of An Engine

The near space vehicle with a high speed is in complex environment. Their externally exposed power systems face serious thermo-mechanical dynamic problems under the effect of aerodynamic forces and heating problems. In this paper an engine(including the heat shield) of power systems is taken as the research object. And the structure response regularities under different conditions of the mechanical, thermal and thermo-mechanical coupling environment are studied. The main contents of the paper are listed below.The dynamic finite element model of the engine is established, which accurately simulate the structure and connection relation between the various components. And the natural frequencies and mode shapes of the engine are calculated by using the finite element method(FEM). And the general rule is obtained through the analysis of the structure response under effects of shock, overload and random vibration excitation.A finite element model for thermal analysis is established. The thermal response of the engine under working, aerodynamic heating and the compound action under both of them are analyzed. The distribution regularity of temperature and thermal stress field are obtained in different heating environments.Through comparative analysis of the methods of the fully thermo-mechanical coupling and sequential thermo-mechanical coupling, a simplified coupling analysis method is proposed. In this method the power spectrum density function in the frequency domain is transformed into time domain signals and then loaded with the temperature field at the same time. Dynamic characteristics and responses under heat-random vibration environments are studied by the method mentioned above to assess the effect of thermo-mechanical coupling quantitatively based on the establishment of the coupling analysis model.In conclusion,the general rules of dynamic characteristics and response, thermal response and kinetics of thermo-mechanical coupling of the engine structure are studied in this paper. And the effect of the thermal-mechanical coupling on the random vibration response of the engine is studied quantitatively. The research in this paper has the important application value for analysis and design of engines and power systems of near space vehicles.