Investigation On Characteristics Of Multi-stage Looped Cascade Thermoacoustic Engines

Multi-stage looped thermoacoustic engines have unique advantages in the utilization of low grade energy,which have attracted more and more enthusiastic researchers attention In recent years.In this paper,the operational characteristics of multi-stage loop-type cascade traveling-wave thermoacoustic engines are carried out in order to explore the characteristics of the thermoacoustic engines.The main contents include the following three parts.1)Using DeltaEC software to simulate the three-stage looped thermoacoustic engine,the sound field and sound energy distribution of the three-stage looped thermoacoustic engine are solved,and the influence of heating temperature and stack length on the system performance is analyzed.Research indicates that the heating temperature has influence on system performance.The higher the heating temperature is,the higher the sound power is,and the higher the thermoacoustic conversion efficiency is,but the thermoacoustic conversion efficiency is not increased monotonically with the increase of the heating temperature.2)The steady-state performance of the three-stage thermoacoustic engine-driven pulse tube refrigerator is studied by using DeltaEC software,and The sound field distribution of the load of the main loop engine and the branch pulse tube refrigerator is solved.The simulation results show the same trend as the experimental results,indicating the validity of the simulation.The simulated total exergy efficiency is slightly higher than the experiment total exergy efficiency,which may come from numerical simulations based on a one-dimensional thermoacoustic model that ignores some of the viscous loss and heat loss.Simultaneously,the influencing factors of system performance are explored.The higher the heating temperature is,the higher the heating capacity and the cooling capacity are,and the thermal efficiency of the thermoacoustic refrigeration has a maximum in the middle.The higher the cooling temperature is,the higher the heating temperature and the cooling capacity are,the total exergy efficiency has a maximum in the middle.3)The performance of the low temperature difference mixed loop-type thermoacoustic refrigerator proposed by de Blok was optimized.Under the given conditions,the cooling capacity of the variable diameter model is 3.44 kW and the total cooling efficiency is 15.9%.The cooling capacity of the Equalizing tube diameter model is 0.99 kW,and the total cooling efficiency is 11.8%.Simultaneously,the influence of the inconsistency of the parameters of the thermoacoustic unit on the system performance is studied.The results shows that when the parameters of the system are exactly the same,the performance parameters of the units are completely consistent along the path distribution,which is beneficial to consistent load access,and can effectively improve the performance of the whole system.Inconsistent element parameters will lead to inconsistencies in the distribution of the unit sound power,Which leads to the inconsistency of the thermoacoustic conversion efficiency of each unit and is harmful to consistent load access.When the system is loaded,the inconsistency of each unit will lead to inconsistent performance of the unit,which may be higher or lower than the original unit when the performance of the same,but the overall performance of the system is declining.