The Numerical Simulation Research On A Two-stage Traveling Wave Thermoacoustic Engine Using Low Grade Thermal Energy

In recent years,with the development of society and the improvment of human’s living standard,building energy consumption is rising,has become the most quantity of energy utilization.Building energy efficiency has become one of key areas of energy conservation in China,efficient building energy system is an effective way to reduce building energy consumption.A two stage traveling wave thermoacoustic engine is a new type of thermal power conversion device which has developed for recent years.It has become a hot research topic in the field of engineering thermophysics and energy,due to the advantages of using moderate and low temperature heat source,no harmful substances emission,high thermal efficiency and good reliability.Therefore,it is of great significance to develop efficient building energy systems based on the two stage traveling wave thermoacoustic engines in order to meet the developed demand of energy saving technology under the new energy system.In this article,first of all,the research advance and status have been reviewed.The basic governing equations with solutions are summarized.The thermoacoustic time-averaged equations and performance evaluation indexes are also provided.Then focus on the following parts:(1)A design scheme is proposed for a two stage traveling wave thermoacoustic engine.According to the linear thermoacoustic theory and the current pressure pipeline design standard,the design calculation of thermoacoustic elements in a two stage traveling wave thermoacoustic engine is conducted.The structure and materials of heat exchanger are introduced and the quantitative index of its length is given.The structure type of regenerator is determined,and the rationality of structure parameters for regenerator is checked.A type of thermal buffer tube with straight tube and conical tube cascaded is proposed to restrain Reyleigh streaming and the quantitative index of its length is given.A resonator with cooling coil is adopted to replace the secondary ambient heat exchanger in order to reduce the loss of resistance in the system.The pipe diameter is determined by DeltaEC,and the relationship between frequency and the length of resonator is given.(2)A two stage traveling wave thermoacoustic engine is analyzed by numerical simulation based on DeltaEC,a linear thermoacoustic simulation soft.The system structure of two stage traveling wave thermoacoustic engine is introduced,and the transfer process of acoustic power flow and total energy flow in the system is described.According to the symmetry of the two stage traveling wave thermoacoustic engine,a simplified DeltaEC model is built.The assumption is proposed that simulating one of thermoacoustic engine units can realize the simulation of whole loop,and the verification is carried out.Otherwise,the distribution of acoustic field in a two stage traveling wave thermoacoustic engine is central symmetry.The operational characteristics under the condition of steady state for the two stage traveling wave thermoacoustic engine is simulated by DeltaEC.The distribution rules of acoustic field,acoustic power flow and total energy flow in the system are obtained.The effects of different length of regenerator on net acoustic power,input power,thermal efficiency and pressure ratio are explored under different working condition.(3)A two stage traveling wave thermoacoustic apparatus is set up which can adjust the length of regenerator and resonator and realize single and double stage switching as well.The two stage traveling wave thermoacoustic engine is built up on the base of the design scheme and numerical simulation discussed in chapter 2 and chapter 3.Structure and manufacturing process of each component are described.A new type of thermoacoustic core which can change the length of regenerator is proposed.Some flanges are arranged on the resonator in order to realize the replacement of resonator for different length and stage number switching.Experimental measurement system and vacuum system are introduced.The driving heat source of the two stage traveling wave thermoacoustic engine is a solar dish thermal system.