多级环形热声热机的起振条件及特性

Onset condition and characteristic of multistage looped-tube thermoacoustic engine

基于线性热声网络理论,推导了多级环形行波热声热机的起振条件式,并对无负载系统的起振及稳态特性进行数值模拟分析.重点研究了不同工质、充气压力、回热器丝网水力半径及热声芯级数对热声热机起振温度、自激振荡频率以及相应声功率和效率的影响.模拟结果表明:不同充气压力下均存在获得最低起振温差的最优丝网水力半径,且在最优值附近存在一个合适的选值范围,使起振温差随充气压力的增加而降低,充气压力对振荡频率的影响不大;起振温差和振荡频率均随热声热机级数的增加而减小,当回热器温差一定时,增加级数会降低单个热声芯产生的声功率和效率.在一定加热功率条件下,采用混合工质可以获得比氦气工质更低的起振温差,且能获得与氦气工质相当的高声功率,因此混合工质有利于降低热机系统的工作温度和低品位热能的利用.

Based on the linear thermoacoustic network theory ,the onset condition equation was de‐rived for a multistage looped‐tube thermoacoustic engine .T he onset and steady state characteristics of the unloaded system were numerically simulated and analyzed . The effects of working substance , charging pressure ,the hydraulic radius of regenerator screen mesh and stage number of thermoacous‐tic core were closely investigated on the onset temperature ,oscillation frequency ,acoustic power as well as efficiency .The simulated results indicate that at different charging pressures there all exist an optimal hydraulic radium of regenerator screen mesh to achieve the lowest onset temperature .Moreo‐ver ,near the optimal value there is a suitable selection range in w hich the onset temperature difference decreases with the increasing of the charge pressure .However ,there is a little influence of the charge pressure on the oscillation frequency ;the onset temperature difference and oscillation frequency both decrease with the increase of stage number of thermoacoustic core .Meanwhile ,at a constant regener‐ator temperature difference ,the acoustic power and efficiency of a single thermoacoustic core will both decrease with the increasing of stage number of thermoacoustic core .At constant heating power ,u‐sing mixture working substance will achieve lower onset temperature difference than the He system , while the acoustic power is almost as high as the He system .Therefore ,it is in favor of using a suit‐able mixture working substance to decrease the working temperature of heat engines and to utilize the low‐grate thermal energy .