异型回热器热声热机结构动力学分析

利用商业软件ANSYS从结构动力学角度模拟分析了回热器结构的改变对热声热机的影响.在之前研究的基础上,改造了普通板叠回热器的结构,建立针束、肋片板、微坑板异形回热器模型,对包含各回热器的热声整机模型进行了结构动力学分析.分析得出,普通板叠回热器热声热机在150Hz附近谐振,而异型板叠回热器热机由于结构的改变,共振频率发生变化,在高阶模态应变到达峰值,说明了回热器的结构优化是提高热声热机性能的有效手段.     

热声板叠式回热器结构动力学分析

分别利用Solidworks和ANSYS软件对热声系统中回热器的热声机理从结构动力学角度进行模拟研究.建立三维板叠式回热器的物理模型,得到在0.5,0.6和0.7 MPa充气压力作用下和在系统内谐振动作用下回热器的各动力学参数的响应及其分布.从模拟结果得出:回热器在热声系统振动中存在多种模态;在低频段各点应力-应变基本吻合,高频段各点差异逐渐增大;在一阶固有频率3 300 Hz附近,回热器内各点的应力和应变达到最大值.     

热声热机中回热器的数值计算与分析

针对热声热机系统回热器（或板叠）的数值计算。讨论了简单实用的得谐分析方法,并对热声制冷机中的热声板叠进行了数值计算与分析。计算结果为回热器（或板叠）的设计与优化奠定基础,从而保证系统设计的可靠性。     

热声热机——无运动部件的低污染热机

通过对国内外热声热机理论和实验研究的分析，展望我国发展热声热机的前景。     

热声热机板叠式回热器结构数值计算

将热声热机板叠式回热器气体通道看成矩形导管,对回热器结构进行数值计算。通过声波导管理论的推导,对微型热声热机回热器板叠尺寸进行研究,利用高次波在气体通道衰减原理,计算回热器板叠纵向长度。研究结果表明:50kHz的热声热机回热器板叠最小横向长度为3.43mm;横向长度为3.43mm的板叠对于频率分别为20,30,40kHz的3种声源的最佳纵向长度分别为5.9,6.0和6.4mm,最佳纵向长度随声源频率的降低而减小。     

热声热机谐振管截止频率选择机理

通过波导管理论的推导，对热声热机中谐振管的截止频率选择机理进行研究，导出谐振管中传播一维平面波的频率传播范围，阐述热声热机谐振管中一维平面波的传播机理，即谐振管截止频率选择的理论依据。理论研究结果表明：对于同样等效直径的矩形谐振管，其截止频率远大于圆形谐振波导管的截止频率；对于等效半径为2mm的微型热声制冷机的谐振管，当声速为343m／s时，谐振管的截止频率为50248Hz，实际的工作频率5500Hz，远小于谐振管的截止频率；在热声热机谐振波导管中只存在一维平面波传播，有利于合理布置热声热机的其他部件，达到优化热声热机的目的。     

高频驻波热声热机的数值研究

以1/4波长驻波热声热机为研究对象,建立了平行板叠结构回热器以及异形板叠结构回热器的数值模型,采用Fluent软件分析了这两种结构回热器产生的压力、速度以及流场.研究结果表明:异形板叠结构回热器自激振荡达到饱和所需的时间比较短,压力幅值比较高;非线性声场的扰动,导致不同时刻回热器冷热两端温度分布不稳定,相比平行板叠结构回热器,异形板叠结构回热器温度梯度比较小,有利于低品质热源的应用;针对板叠结构回热器,改变平板的结构,有利于实现热声系统的匹配;异形板叠结构回热器周围的流场明显强于平行板叠结构回热器,有利于流固之间的耦合,提高了热声转换的效率.     

热声热机中液相工质的选择与计算

分析了热声热机中使用的液相工质的选择方法,研究了适合于热声热机 液相工质的热力学性质和热物理性质的计算方法,并对液相工质R218进行了数值计算,计算结果已有的实验结果相符合,计算方法和结果具有令人满意的精度,研究结果可用于低品位热源如太阳能驱动的热声热机的研究与开发。     

实际热声热机微热力学循环性能优化

分析实际热声热机微热力学循环中的诸多因素,运用有限时间热力学方法,导出实际热声热机微热力学循环的效率与输出声功率的最优关系,分析不可逆程度因子及热漏系数对此最优关系的影响.结果表明:实际热声热机微热力学循环中存在一最佳温度振荡值,使循环在得到高效率的同时得到高输出功率,并由数值计算认证了这一结论.     

铁路车轮结构动力学分析与仿真

本文采用国内铁道客车用外径为915D的s型辐板车轮为研究对象,利用Ansys有限元软件建立车轮三维有限元模型,分析车轮的固有特性（模态）,得到车路在固有频率下的振型,并总结出了标准车轮的振动特性及其规律.进行了车轮谐响应分析,并得到加速度和位移导纳幅值.研究结果表明：车轮的模态分析中,频率在0～300 Hz范围内车轮几乎没有变形;在300～1000 Hz范围内,车轮主要表现为踏面的轴向振动;在1000 Hz以上时除了踏面的扭摆振动,开始出现辐板的轴向和径向振动,在高频段内辐板和踏面是车轮的主要振动部位.并且由于车轮模型的对称性,使得车轮各阶模态振型左右对称.车轮的谐响应分析中,在8～1000 Hz的低频段,车轮辐板以面外振动为主,对应的轴向位移导纳比径向位移导纳大.在1000～4000 Hz的高频段范围,以面内振动为主,对应的径向位移导纳更大.车轮在8～4000的计算频域内的共振频率较多.在每个共振频率后,都对应出现一个响应很低的反共振频率.     

多级环形热声热机的起振条件及特性

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.     

Advances in thermoacoustic engine and its application to pulse tube refrigeration

Thermoacoustically driven pulse tube refrigerator, a novel cryocooler without any moving components using heat energy as driving power, attracts much effortsfrom the researchers in the field of cryogenics and refrigeration in the past decades. After a short introduction of the history about thermoacoustics, we presented the key technology, followed by a detailed review on theoretical and experimental developments and advances of thermoacoustics.The prospective research emphases are also presented at the end of this review.     

3kHz微型驻波热声发动机的实验研究

以芯片冷却为应用背景,在线性热声学理论的指导下,以降低起振温度、获得较高的热声转换效率为目标,进行了机型的选择和热声热机核心段的设计.研制了一台3.3kHz微型驻波热声发动机,长度为55mm,由加热器、回热器、冷却器及谐振管4部分组成.在9W的加热量下,热端温度78℃时该发动机产生自激振荡,起振温差为26℃.稳定运行后...     

Influence of resonator diameter on a miniature thermoacoustic Stirling heat engine

A small scale thermoacoustic Stirling engine （TASHE） is simulated according to the linear thermoacoustic theory. The computed results show that in a small scale thermoacoustic Stirling heat engine, the diameter of the resonance tube might have important influences on the working frequency and the performance of the engine, which are always neglected in a large scale system. Likewise, the analysis and experimental results show that in order to obtain better engine performance, the diameter of the resonance tube must be chosen appropriately according to the looped tube dimension and the input heating power. This provides an effective way to miniaturize the thermoacoustic Stirling heat engine. According to the computation and analysis, a small scale engine was built, the resonance tube length and diameter of which were about 350 mm and 20 mm, respectively, and the working frequency was about 282 Hz. When the input heating power was about 637 W, the maximal peak to peak pressure amplitude and pressure ratio reached 0.22 MPa and 1.116, respectively, which were able to drive a thermoacoustic refrigerator or an electrical generator.     

Characteristics of onset and damping in a standing-wave thermoacoustic engine driven by liquid nitrogen

We explore characteristics of onset and damping in a thermoacoustic engine (TE) driven by cryogens instead of conventional heat sources above the ambient temperature by a comprehensive study of a self-made standing-wave thermoacoustic engine driven by liquid nitrogen. The experiments verify the feasibility of enhancing the thermoacoustic oscillation at cryogenic temperatures. The onset temperature difference along the stack of the TE significantly decreases, compared with that of a conventional TE driven by high-temperature heat sources. The resonance frequency of the cryogen-driven TE is smaller than that of the heat-source-driven TE, mainly due to the lower average temperature of the working gas. Experiments and calculations show that the temperature discrepancy between onset and damping is partly caused by the linear temperature distribution along the stack before damping, together with the nonlinear distribution before onset. These results will contribute to a better understanding of thermoacoustic oscillation and to the recovery of the cold energy of cryogens.     

A high pressure-ratio, energyfocused thermoacoustic heat engine with a tapered resonator

Heat energy with temperature difference may lead to self-excited acoustical oscillation under appropriate condition, which is called “thermoacoustic phenomenon”. The physical phenomenon was observed about two hundreds years ago. However, the research on high-energy thermoacoustic devices was begun only about a decade ago.Thermoacoustic machines use inert gases as working medium and have no moving mechanical pans; consequently they are really environment-friendly and highly reliable.The efficiencies of thermoacoustic machines are now greatly improved, close or even higher than that of conventional heat engines.