| Thermoacoustic heat engine is a new type of thermal power conversion device.It replaces the traditional mechanical compression with thermoacoustic resonance,which greatly reduces the moving parts of the thermal power device.Its basic structure is simple and reliable,its service life is long,its working noise is low,and its pollution-free characteristics are outstanding,which makes the development direction of thermoacoustic engine clear and its application prospect broad.However,because the transformation process of thermoacoustic effect involves very complicated nonlinear factors,each theory has its limitations and adaptability.Therefore,finding a suitable analysis method can deepen the understanding of the working mechanism of thermoacoustic engine.Based on the finite-time thermodynamics theory,the theoretical cycle model of thermoacoustic engine,the cycle model of thermoacoustic engine and the cycle model of thermoacoustic refrigerator are established in this paper.The influence of each design parameter on the system performance is analyzed by numerical method,and the optimal operating characteristics and working range of the system are obtained.The full text is as follows:The first part is the establishment of theoretical cycle model of thermoacoustic engine.By combining the wave equation of gas working medium in thermoacoustic system with the equation of internal energy variation of monatomic gas working medium,the equation of ideal gas state and the equation of energy conservation,the analytical expression of lateral heat exchange between working medium gas and capillary wall is derived,and the thermoacoustic self-excited oscillation mechanism of the corresponding model is analyzed.The results will be helpful to deeply understand the essence of thermoacoustic conversion.The second part is the finite time thermodynamic optimization research of thermoacoustic engine.Based on the internal reversible model,a thermoacoustic engine model considering irreversible and heat leakage is established,and the analytical expressions of dimensionless power,efficiency,efficiency,profit rate and pure profit rate are derived.The influence of each design parameter on the optimization objective is analyzed under the condition of internal irreversibility and external irreversibility,and the optimal working range of the system is obtained.By optimizing the pressure-drive ratio of the thermoacoustic engine,the optimal performance characteristics of the circulation system are obtained.The results show that there is a reasonable range of pressure drive ratio,which makes the profit rate and efficiency of thermoacoustic engine cycle reach the optimum at almost the same time,which is of practical significance.The third part is the finite-time thermodynamic optimization of thermoacoustic refrigerator.Based on the internal reversible model,a thermoacoustic refrigerator model considering irreversible and heat leakage is established,and the analytical expressions of dimensionless refrigeration rate,refrigeration coefficient,efficiency,profit rate and pure profit rate are derived.The influence of each design parameter on the optimization objective is analyzed under the condition of internal irreversibility and external irreversibility,and the optimal working range of the system is obtained.By optimizing the pressure-drive ratio of the thermoacoustic refrigerator,the optimal performance characteristics of the circulation system are obtained.The results show that the thermoacoustic refrigerator has the optimal profit rate and dimensionless optimal refrigeration rate,but the dimensionless refrigeration rate and refrigeration coefficient cannot be optimized at the same time. |
