扬声器驱动热声制冷机的频率特性研究

对电声制冷机的电声效率的影响因素及与工作频率的关系做了实验研究。实验表明,回热器长度和填料种类、位置以及谐振腔长度、工作气体等都对工作频率有影响,存在一个频率迁移,使制冷机工作在优化范围。对于扬声器参数及电声效率计算采用网络模型做了验证计算。计算结果和实验是一致的。     

Experimental investigation of a thermoacoustic refrigerator driven by a standing wave twin thermoacoustic prime mover

The objective of this study is to analyse the performance of thermoacoustic refrigerator (TAR) measured in terms of hot end temperature and temperature difference across refrigerator stack with two different spacing namely 0.4 mm and 0.8 mm and stack used in refrigerating section was made of low thermal conductivity materials namely Mylar sheet and photographic film & the experiments were carried out at 1 MPa pressure using helium as working fluid. High powered acoustic wave with frequency of 460 Hz and pressure amplitude of $?$0.07 MPa was obtained from twin thermoacoustic prime mover (TAPM) and this acoustic wave produced temperature difference of 16 °C across the Mylar sheet stack made of 0.4 mm spacing in refrigerator section. From this study, it has been inferred that twin TAPM can act as efficient drive for TAR.     

高频热声制冷机中的压电喇叭特性

研究建立了1台5 kHz微型热声制冷实验样机,对压电喇叭谐振系统的阻抗特性,以及频率和电压响应特性进行了实验研究.初步的实验显示,压电喇叭与驱动电源和热声谐振系统之间需要在电学和声学上进行匹配,PZT5的压电陶瓷材料发热较大,且提供的声功率较小,这些是影响微型制冷的重要因素.     

哑铃形热声谐振器的谐振频率

热声自激振荡模态取决于声学谐振器结构形式和特征尺度。级联型热声热机依靠哑铃形谐振器来调制所需要的局部高阻抗行波声场,谐振管通常由几段不同横截面的管段组成。哑铃形热声谐振器的谐振频率由共鸣腔容积、谐振管截面和长度共同决定。根据哑铃形谐振器不同截面管段内的声传播规律、共鸣腔声学边界条件以及管段间的声压和体积流率连续条件,利用行波叠加的方法,建立均匀管模型、变截面模型和热声网络模型,得到了系统谐振频率随共鸣腔容积变化和谐振管特征尺寸变化的规律。系统谐振频率的变化将引起最佳听音点的位置的移动,进一步起到调节回热器声阻抗的作用。实际热声热机实验研究中,通过改变谐振器特征尺度或结构形式调节系统的谐振频率,也是热声热机调试过程中实现自激振荡的主要手段。     

Temperature difference generated in thermo-driven thermoacoustic refrigerator

The work proposes a simple and feasible calculation method--network model method to calculate temperature differences generated in thermo-driven thermoacoustic refrigerator (TAR). The theoretical calculation model is first built. The network model is given and used to make numerical calculations under different conditions including heat-pump stack positions in TAR, different oscillating pressure ratios (PR), plate spacings and different stack geometries. Theoretically calculated results show that the former two factors make significant influence on temperature differences, the influence of stack spacing on temperature difference has relation with PR, and cooling effect of pin-array stack is superior to that of parallel plate stack under other same conditions. Furthermore, theoretically calculated results and experimentally measured data are in good agreement at small acoustic pressure amplitude.     

热声回热器频谱特性的研究--网络类比法的应用

采用网络类比法对回热器热声效应机理进行描述，并建立起网络类比数学模型，采用该模型对回热器不同填料的频谱特性进行了分析和比较。为回热器填料的选择以及回热器与热机系统频率的匹配提供理论依据。     

热声制冷机

热声制冷是微型低温技术潜在的最佳方法。一台声驱动热声制冷机主要包含一个接在中空管道端部的声波发生器和一个在管道内预选位置处放置的热声器件。声波发生器产生的声波在热声效应作用下可在热声器件两端形成温度梯度。介绍了一种基于高效斯特林循环的热声制冷机的基本原理及主要组成。在此基础之上,可通过对各组成部件结构参数的计算、确认,设计出一台热声制冷机。     

Design and analysis of acoustically-driven 50 W thermoacoustic refrigerators

The design of loudspeaker-driven 50 W cooling power thermoacoustic refrigerators operating with helium at 3% drive-ratio and 10 bar pressure for a temperature difference of 75 K using the linear thermoacoustic theory is discussed. The dimensional normalization technique to minimize the number of parameters involved in the design process is discussed. The variation in the performance of the spiral stack-heat exchangers’ at 75% porosity as a function of the normalized stack length and center position is discussed. The resonator optimization is discussed, and the optimized one-third-wavelength (tapered, small diameter tube and divergent section with hemispherical end), and one-fourth-wavelength (tapered and divergent section with hemispherical end) resonator designs show 41.3% and 30.8% improvements in the power density compared to the published 10 W designs, respectively. The back volume gas spring system for improving the performance of the loudspeaker is discussed. The one-third-wavelength and one-fourth-wavelength resonator designs are validated using the DeltaEC software, which predicts the cold heat exchanger temperature of ? 3.4 °C at 0.882 COP, and ? 4.3 °C at 0.841 COP, respectively.     

热声热机的频率特性研究

热声效应是热声回热器与热声工质在一定的温度梯度作用下相互作用的结果,热声热机的频率是热声系统的一个重要参数,对于热声制冷机其直接决定了消耗声功而泵热的可能性.分别分析了不考虑热粘效应和考虑热粘效应时空谐振管的谐振频率,认为考虑热粘效应时,谐振频率大于不考虑热粘效应时的频率,同时分析了有温度梯度存在时的热声驱动器和热声制冷机的谐振频率,认为热声器件的存在改变了系统的频率特性,使系统的频率高于没有板叠存在时的频率.此结论对于热声制冷机的设计有重要的指导意义.     

板叠式回热器的特征频率

提出回热器特征频率的概念,以热声器件的热动力学理论为基础,建立起热声回热器的分布参数网络模型,以实例分析并用Matlab编程计算回热器不同工质下的特征频率,得出了单一He气和He、Ar混合气体下回热器的特征频率分别为565 rad/s和1 300 rad/s以及回热器的阻抗特性和不同工作压力对回热器阻抗影响的关系图.通过计算分析以便为回热器与系统更好地匹配,以及为回热器热声转换效率的提高提供依据.     

热声回热器自激振荡特性的研究

从热动力学理论出发,定量地证明回热器的自激振荡特性为负阻尼振荡。回热器是热机系统的热声源,从外热源吸收热能补偿热机系统的能量耗散,维持系统的热声振荡。对不同的回热器填料进行比较,为回热器的填料选择提供了理论依据。     

填料物性对热声器件谐振频率的影响

利用热声网络理论,对热声器件谐振频率进行了分析计算,揭示了热声器件的谐振频率与其填料物性的关系,利用数值计算分析了填料物性对热声器件谐振频率的影响.结论表明在声压一定的情况下,热声器件谐振频率分别随着其填料物性:横截面积、比定压热容以及密度的增大而增大;随着声压的增大,谐振频率分别随填料的横截面积、比定压热容以及密度的增大而增大得更快.     

Thermoacoustic oscillation in channels of the pressurized He II

In channels filled with the pressurized He II at 1 atm, a continuous thermoacoustic oscillation with a clear sound is triggered above the critical power-input q_λ of the phase transition under some conditions. A temperature distribution along the channel length is entirely maintained as long as the thermoacoustic oscillation lasts, i.e. the heat q_λ is kept transporting in the vortex state without drying the heater surface.The characteristic frequency of the thermoacoustic oscillation depends both on the channel length and weakly on the bath temperature, reflecting the property of the 1st sound.     

缓冲器对热声机谐振频率的影响

介绍了用于计算流体管路谐振频率的流体阻抗法,并对几种带有典型缓冲器布置形式的热声机的谐振频率进行了计算,最后讨论了缓冲器对谐振频率的影响。     

Influence of buffer on resonance frequency of thermoacoustic engine

Frequency matching is of great importance to a thermoacoustically driven pulse tube refrigeration system. To compute the resonance frequency of thermoacoustic engines, the fluid impedance method is introduced. The calculations of the thermoacoustic engines with different arrangements of buffer have been carried out. The influence of the buffer arrangements and the volume on the resonance frequency as well as the acoustic power of thermoacoustic engines is also discussed.     

A simple method to determine the frequency of engine-included thermoacoustic systems

Frequency determination is important for the simulation of a thermoacoustic system consisting of a thermoacoustic engine. Based on the characteristics of linear acoustics, this article proposes a simple method for frequency calculation through numeric investigation. According to the method, frequency value can be decided if it leads to an inflexion point of the amplitude of volume flow rate, which is also a local minimum, most close to the volume flow rate node boundary. Compared with experimental data, the method proves to be very reliable. Besides, a concept of virtual tube is also proposed for frequency determination of thermoacoustic systems with no apparent geometrically-closed end.     

热声系统中的回热器声学特性的理论及实验研究

设计并建造了一台声驱动的热声装置,用于研究回热器的声学特性.从理论上利用相关谱分析方法(包括自相关谱与互相关谱),得到热声系统中回热器的声反射系数,复声阻抗,传播损失和回热器处的入射波与反射波相位差.并通过实验测得的压力信号分析回热器的声学特性.分析比较换热器及不同加热功率的情况下,对回热器声学特性的影响,结论有利于进一步辨识回热器模型中的未知参数.     

行波热声斯特林机中自激振荡的实验分析--利用相空间重构方法

一个由环形行波圈和谐振管组成的热声斯特林系统巳成功的设计和建造，本文介绍了使用声信号的时间序列来进行相空间重构，用相空间重构方法来描述和分析行波热声系统中的自激振荡，对系统的起振特性以及行波模态到驻波模态的转变进行了实验分析和研究。     

大型多功能热声发动机的研制及初步实验 第二部分:热声发动机的初步实验

行波热声发动机在回热器中进行的是可逆热声转换过程,理论上可以更高效地产生和传输声功,因而具有广阔的研究应用前景.对自行研制的大型多功能热声发动机进行了初步实验,着重研究了系统的起振、消振过程及压力波动情况.实验结果表明,该热声发动机比纯驻波型热声发动机具有更低的起振温度、更大的压比及更高的热声转换效率.以氮气为工质,在充气压力为9×105 Pa的条件下,该热声发动机最大压比达1.21,工作频率为25 Hz,这是当前国际上处于前列的实验结果.     

热声热机系统的测量与实验研究

对热声热机驱动耗散性负载的性能进行了实验研究和分析,对热声热机系统起振温度和谐振频率进行了测量和标定。得出导致热声发动机工作在二附谐振频率模态下的影响因素。测量和分析了气体充气压力、频率以及谐振管长度对系统驱动制冷机,产生了25℃的温差。