Open-air traveling-wave thermoacoustic generator

Taking the input and reflected waves into account,the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed.Closed and open acoustic configurations that influence the pressure,volumetric velocity,impedance and acoustic work were compared in detail.Based on the above investigation,an open-air traveling-wave thermoacoustic generator was designed and fabricated.It is composed of a looped tube,a resonator open at one end,a regenerator,and hot and cold heat exchangers.It is a small scale and simple configuration.The resonant frequency is 74 Hz at 1 bar in air.The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20μPa when the heating power was 210 W,respectively.Acoustic pressure is reasonable for practical application as a low-frequency acoustic source.In further work,we believe that the acoustic pressure at the open end can achieve 150 dB,which could be a solution to problems in existing acoustic generators.These problems include low acoustic pressure and system complexity.It can be used as a basic acoustic source for low frequency and long-range noise experiments,and as a supply for high acoustic pressures necessary for industrial sources.     

A 100 W-class traveling-wave thermoacoustic electricity generator

Experimental investigation on a traveling-wave thermoacoustic electricity generator is presented. In the experiment, more than 100 W electrical power was achieved under 2.5 MPa mean pressure, 64 Hz working frequency and 0.2 MPa pressure amplitude.     

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.     

Experimental investigation of a 500 W traveling-wave thermoacoustic electricity generator

In this paper, an experimental investigation of a traveling-wave thermoacoustic electricity generator, which consists of a traveling-wave thermoacoustic heat engine and a linear alternator driven by that engine, is presented. Using the results of previous theoretical and experimental research, we designed and fabricated a traveling-wave thermoacoustic heat engine and a linear alternator. In the experiments, 450.9 W of electrical power was obtained with a maximum thermal-to-electrical efficiency of 15.03%, and a maximum electrical power of 481.0 W was achieved with 12.65% thermal-to-electrical efficiency.     

机械谐振式热声制冷机模态频率研究

研究了一种机械谐振式热声制冷机结构,建立了装置机械谐振系统的二维模型,从振动方程中分析获得了系统的模态频率关系,同时研究了振动质量、机械和气体弹簧、腔体尺寸以及工作压力等参数对模态频率的影响.研究结果显示系统存在两个模态频率,且频率随谐振参数的变化出现分岔.通过对谐振参数的设计和调节,装置可以获得所需的特性和谐振频率.     

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...     

An acoustical pump capable of significantly increasing pressure ratio of thermoacoustic heat engines

A thermoacoustic heat engine is a new device pow- ered by differential-temperature heat energy. It is highly reliable without any moving part and is now becoming an ideal driving source of pulse tube refrigerators or thermoacoustic refrigerators. Most of …     

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.     

风冷溴化锂吸收式制冷机热力－传热耦合性能的研究

本文结合各设备的传热性能，通过计算机模拟，以无量纲量Ｆ／Ｆ为变量研究风冷溴化锂吸收式制冷机的热力－传热耦合性能，据此求得各设备换热面积的合理匹配值．计算结果表明，风冷溴化锂机各设备换热面积经合理匹配，可以显著减小风冷吸收器和冷凝器的换热面积，机组单位基管面积制冷量可因此提高４７％，而机组的性能系数ＣＯＰ值与水冷溴化锂机基本接近．     

现场总线技术在电冰箱测试线中的应用

通过对现场总线技术特点的分析,结合ＥＶＯＣ工控设备在电冰箱测试线中的应用,从现场总线技术的角度 介绍了新一代冰箱测试线的系统特点与功能。     

移频降噪理论在往复式冰箱压缩机噪声控制中的应用

通过模拟计算QD58型往复式冰箱压缩机的声学特性，指出压缩机噪声最大峰值与其内部气体共鸣音直接有关．运用移频降噪理论，改变压缩机内气体的声学固有频率，降低共鸣音．实测了空气介质下压缩机内腔安装隔板后的移频降噪数据．并用电一声类比法推导的压缩机内气体的声学固有频率对隔板各个几何参数的灵敏度公式，调整实际工作状态下隔板的几何参数，模拟计算了压缩机内部气体声学固有频率的变化．     

压力波制冷机工作管开口端处的流动分析

对压力波制冷机内非定常流动过程、波系结构、激波形成机理等进行了探讨 .得到了入射激波Mach数(Ms)的表达式 ,并分析了进口气流速度、压力及膨胀比对Ms 的影响 .     

双驱动热声热机谐振管中声波的传播特性研究

分析了双驱动热声热机谐振管中声波的传播特性,通过分析指出,对于双驱动的热声热机,可以通过改变其反射系数和驱动声源的驱动相位差,进而实现谐振管声场的声压幅值和声场相位的改变.理论研究表明,在|rp|=0.3,相位差为σπ=0.5π时的声压幅值大于σπ=π的声压幅值;而在σπ=0.5π时,声场幅值随反射系数|rp|的增大而增大.实验研究表明,在相位差σπ为常数时,通过改变不同的反射系数值,就可以实现谐振管中声场的调节;在反射系数|rp|为常数时,通过改变谐振管两边驱动声源的驱动电压值,也可以实现声场幅值和相位差的调节.这样就有利于调节结构已经确定的微型热声热机的最佳声场分布,使其达到最优热声转换效率,实现微型双驱动热声制冷机热声制冷效率的最优化.     

Research on defects and domain characteristics of MgO-doped near-stoichiometric lithium tantalate in room-temperature polarization process

MgO-doped congruent and near-stoichiometric lithium tantalate single crystals were grown by Czochralski technique and flux method respectively. Optical absorption studies showed that the UV absorption edge was very sensitive to the composition of the crystals and the decrease in defects led to the blue-shift of the UV-edge. The unit domain shape also related to the composition, and the observed results of the crystal wafers that etched by hydrofluoric acid indicate that the domain structure of near- stoichi...     

北方地区小型氨制冷系统压缩机选型探讨

北方地区冬夏季温差较大,在小型冷库设计时,冷凝水温度随环境温度发生变化,直接影响压缩机的选型．通过对具体工程实例的分析,总结出小型冷库压缩机的优化选型方案,从而既满足设计要求,又达到经济运行的目的。     

A novel coupling configuration for thermoacoustically-driven pulse tube coolers： Acoustic amplifier

A thermoacoustically-driven pulse tube cooler has re-cently reached temperatures below 77 K[1] by modifying the resonance tube of the thermoacoustic engine and the hot end phase adjuster of the pulse tube cooler. Normally, the pulse tube cooler is directly connected with the ther-moacoustic engine so that pressure ratio available to the pulse tube cooler is limited by what the thermoacoustic engine can provide[1,2]. To obtain temperatures below 70 K, the high frequency pulse tube cooler genera…     

A study on multifunction heat pipe type high efficient adsorption refrigerator using compound adsorbent-ammonia

Adsorption refrigeration systems have the advan- tages of environment benign, zero ozone depletion po- tential (ODP) as well as zero global warming potential (GWP) due to the use of natural refrigerants such as ammonia, water, methanol, etc. Adsorption re…     

混合热阻条件下不可逆斯特林制冷机的基本优化关系

该文研究了混合热阻条件下不可逆斯特林制冷机的性能界限,导出了制冷机的制冷系数与制冷率间的优化关系,并作了些有意义的讨论,从而为斯特林制冷机的优化设计和最佳工况的选择提供些理论指导     

远程教学系统中流媒体网络传输的动态控制

在把流媒体技术应用于一个远程教学系统的过程中，本文具体设计了流媒体客户端缓冲区的预警机制，并提出了一个流媒体网络传输的动态控制策略。仿真实验结果表明：在实时性、客户端适应性、多媒体通信质量等方面均得到了一定的改善和提高。