| As a clean and efficient energy source,natural gas' s position in the world's energy market continues to rise.Recycling the large amount of cold energy released during the gasification of liquefied natural gas is of great significance to China's emission reduction and sustainable development strategy.As a unique variant of the Stirling heat engine,the thermoacoustic engine holds the advantages of high theoretical efficiency,simple structure,and reliable operation compared with technologies such as the direct-expansion turbine,the low-temperature Rankine cycle and the gas turbine cycle.Recently,the multi-stage traveling-wave thermoacoustic engines have received more and more attention due to their lower onset temperature differences and much higher energy density.However,at present,there is still a lack of researches related to the thermoacoustic engines for cold recovery,and the working mechanism of thermoacoustic conversion under low-temperature conditions is still not clear.To explore the thermoacoustic conversion mechanism under cryogenic conditions,verify the feasibility of the thermoacoustic system in the field of cold energy recovery,and fill the gap in experimental research in this field,both numerical simulation and experimental research is carried out in this paper.The main contents are as follows:1.,Numerical simulations were performed based on the DeltaEC software for the design,optimization,and the rationality verification of the 3-stage traveling-wave thermoacoustic engine driven by cold energy.The influence of the core components on the thermoacoustic effect under cryogenic conditions was investigated.Driven by a temperature difference of 110-500 K with 4 MPa helium as the working medium.This system could provide 3 × 5 kW acoustic power,with an overall sound power-thorium efficiency of 44.2%2.A simplified structure of a 3-stage traveling-wave thermoacoustic engine driven by cold energy if proposed,indicating that the AHXs and TBTs can be removed in the cold reovery applications.Relative numerical simulations were carried out and the results showed that the overall performance is even improved in the Simplified structure compared with the Original structure.The analysis of the exergy loss of the two systems under the same exergy input shows that,in addition to the removal of redundant components,reduction the flow-rate amplitude of the working fluid in the resonant tube is another important factor that leads to the performance improvement.Therefore,this simplified structure can significantly improve the compactness of the thermoacoustic engine system and improve the overall performance of the system.4.Based on the existing traditional heat-driven traveling-wave thermoacoustic engine,a cold-driven 3-stage traveling-wave thermoacoustic engine system was designed and built up.Experimental studies under different inflation pressure and hot-end temperature were conducted to compare the onset characteristics,operating frequency,and pressure amplitude.The experimental results are compared with the simulation results and the performance of traditional heat-driven systems,the result indicates: The onset characteristics are affected by the mean pressure of the working gas,the temperature on both ends of REG: It would be easier for this system to start up with the working medium with higher pressure,and higher mean temperature of REG.The operating frequency is stabilized at about 50 Hz,which is slightly lower than its heat-driven counterparts,which is consistent with the theoretical prediction trend.The pressure amplitude increases with the increment of inflation pressure and driving temperature difference.When the pressure amplitude is relatively low,When the temperature difference ?T is close to the oscillation temperature difference,the simulation results agree well with the experimental result.As the temperature difference further increases,the error gradually increases due to the influence of nonlinear phenomena. |
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