热声谐振管的试验研究

热声谐振管是热声热机的关键部件,它相当于一个发动机,将热能转化为声能。对热声谐振管进行了实验研究,并对其起振温度、频率、振幅、输出功率进行测量和分析。     

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。     

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。     

修改变温热源热声发动机驱动制冷机性能

为提高环路多级行波热声发动机驱动制冷机系统在变温热源条件下的热功转换性能,使用SAGE软件对不同加热温度的子系统进行解耦计算,分析了热源温度、回热器和谐振管结构尺寸等影响因素,然后根据计算结果对整机系统进行了结构优化。结果表明:优化后整机系统内部声场行波比例上升、部分谐振管中获得了更大声阻抗幅值,但谐振管尺寸的增加增大了声功损失面积;在整机吸热量和谐振管中声功损失量都增加的情形下,整机热声转换效率和相对卡诺效率略微下降,负载制冷机获得了更多声功。     

行波热声发动机末端耦合方式研究

行波热声发动机可与各种声学负载耦合,在对耦合位置的研究基础上,进一步开展负载末端耦合时行波热声发动机的性能研究.同时改变直管谐振管内径和长度,使频率恒为67.7 Hz,保证发动机环路声功转换特性一致.研究表明,当谐振管内径为120 mm时,系统性能最好;以氦气为工质,在平均压力3 MPa、加热功率2 000 W、热端温...     

谐振管几何形状对热声发动机工作性能的影响

谐振管作为热声发动机的重要部件之一,其几何参数的变化对热声系统的工作性能有重大影响,在驻波型热声发动机系统上对锥形谐振管和圆直谐振管进行了初步的实验对比,以探明谐振管的形状对热声发动机系统性能的影响.实验结果表明,在系统的工作频率固定在130 Hz的情况下,无论是压比、输出声功,还是相对卡诺效率,采用锥形管的系统都要比采用圆直管的系统具有更大的优势.     

影响热声发动机工作频率的因素

热声发动机工作频率关系到与负载的匹配情况,是热声发动机声能输出的重要评价指标.对热声发动机的频率调节手段进行了系统分析,试验验证了部分调频方法,并运用数值模拟分析了新的调频手段.研究发现,通过改变工质类型、改变谐振管长度和直径,可以在一定程度上有效调节热声发动机的工作频率.数值模拟结果显示,发动机内气体平均温度较平均压力和回热器长度对工作频率的影响更大.     

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.     

热声发动机压力特性研究

热声发动机压力特性主要体现在压力波形、相位、压比、压力振幅以及振荡频率等方面,是衡量热声发动机性能的重要依据之一.实验研究了加热温度、充气压力、谐振管长度、工质种类、负载等对压比、压力振幅、频率等压力特性的影响,为更好地进行热声发动机的设计和应用奠定了基础.     

行波型热声发动机谐振管的调相作用

基于环形圈加谐振管的热声发动机的两自由度模型构思,在调相机理上开展了工作.系统分析和仿真研究表明:谐振管对于热声发动机系统不仅是决定系统工作频率、储能和稳定工况,还对行波型热声发动机的声场产生调相作用.针对不同形式的谐振管(谐振管,谐振腔和容腔),以及不同体积的容腔负载(10 L,20 L,40 L)进行仿真计算.研究不同条件下,对回热器处的压力和体积流率之间的相位调节作用及声功的影响.在此基础上,对回热器起点、中点和终点3个位置的流体微团进行分析,得到不同位置的p-V图.结果表明,谐振管的确起到调节声场相位的作用,容腔形式的谐振管更有利于回热器内声场的优化,而容腔的体积大小对回热器声场的影响不大.     

Investigation on a thermoacoustically driven pulse tube cooler working at 80 K

The pulse tube cooler (PTC) driven by a thermoacoustic engine can completely eliminate mechanical moving parts, and then achieves a simpler and more reliable device. A Stirling thermoacoustic heat engine has been constructed and tested. The heat engine can generate a maximal pressure ratio of 1.19, which makes it possible to drive a PTC and get good performance. Frequency is one of the key operating parameters, not only for the heat engine but also for the PTC. In order to adapt to the relatively low design frequency of the PTC, the operating frequency of the thermoacoustic heat engine was regulated by varying the length of the resonance tube. Driven by the thermoacoustic engine, a single stage double-inlet PTC obtained the lowest refrigeration temperature of 80.9 K with an operating frequency of 45 Hz, which is regarded as a new record for the reported thermoacoustically driven refrigerators.     

行波热声发动机驱动的脉管制冷机研究

通过改变热声发动机谐振直路长度,研究系统在不同工作频率下的性能.研究发现,在一定条件下降低频率可以显著改善脉管制冷机的性能.在工作压力为2.7 MPa,加热功率为2 350W,工作频率为45 Hz时,双向进气型单级脉管制冷机获得了80.9 K的最低制冷温度,这是目前用热声制冷方法获得的最低制冷温度.     

Effect of different working gases on the performance of a small thermoacoustic Stirling engine

The performance of a small thermoacoustic Stirling heat engine (TASHE) was investigated with three kinds of working gases experimentally and numerically. The examined performances focused on the operating frequency, onset temperature, pressure amplitude and some temperature characteristics after onset. The working frequency with nitrogen, argon and helium as the working gas was 45 Hz, 42 Hz and 130 Hz, respectively. The engine worked with helium in a much wider range of mean pressure than with nitrogen and argon. There was an optimal mean pressure for the minimum onset temperature for each working media. Using nitrogen and argon as working gas rather than helium, another optimal mean pressure for the highest pressure ratio was obtained in the experiment. The loop dimension was indispensable in determining the frequency and the highest pressure ratio was observed in the resonator cavity.     

Numerical investigation on a 300 Hz pulse tube cryocooler driven by a three-stage traveling-wave thermoacoustic heat engine

A 300 Hz pulse tube cryocooler (PTC) driven by a three-stage traveling-wave thermoacoustic heat engine (TSTHE) has been proposed and studied in this paper. In the configuration, three identical thermoacoustic heat engine units are evenly incorporated in a closed traveling-wave loop, in which three pulse tube cryocoolers are connected to the branch of each thermoacoustic heat engine. Compared with the conventional thermoacoustic heat engine which involves a traveling-wave loop and a long resonator, it has advantages of compact size and potentially high thermal efficiency. A TSTHE–PTC system was designed, optimized and studied in detail based on the thermoacoustic theory. Firstly, numerical simulation was conducted to design the system thus the optimum structure parameters of the system were obtained. With the operating condition of 4 MPa mean pressure and high working frequency, a cooling power of 7.75 W at 77 K and an overall relative Carnot efficiency of 11.78% were achieved. In order to better understand the energy conversion characteristics of the system, distributions of key parameters such as acoustic work, phase difference, dynamic pressure, volume flow rate and exergy loss were presented and discussed. Then, the coupling mechanism of the system was investigated. In addition, influence of coupling position on the system performance was further studied.     

Influence of resonance tube length on performance of thermoacoustically driven pulse tube refrigerator

A resonance tube is an important component of a thermoacoustic engine, which has great influence on the performance of the thermoacoustically driven pulse tube refrigerator. A standing wave thermoacoustic engine is simulated with linear thermoacoustics. Computed results show that an appropriate accretion of the resonance tube length may lead to a decrease of the working frequency and an increase of the pressure amplitude, which will improve the match between the thermoacoustic engine and the pulse tube refrigerator. The theoretical prediction is verified by experiments. A refrigeration temperature as low as 88.6 K has been achieved with an optimized length of the resonance tube, helium as working gas, and 2200 W of heating power.     

采用正弦型谐振管的高频驻波热声发动机

设计了一截面积正弦变化的对称管道作为高频驻波发动机谐振管,实验研究了该发动机的工作性能与声功输出能力,并与采用等直径谐振管的实验结果进行对比.在一定加热功率下,正弦管能有效抑制系统产生的二阶谐波,提高一阶压力波动幅值并降低加热块温度.由于存在显著的非线性效应,基于经典线性热声理论的计算无法预测两种谐振管实验性能的不同,并且与实验结果偏差很大.     

Advances in a 300 Hz thermoacoustic cooler system working within liquid nitrogen temperature range

With the combined advantages of high reliability, compact size and low electromagnetic interference, a high frequency operating thermoacoustic cooler system, i.e. a pulse tube cooler driven by a thermoacoustic heat engine, is quite promising for space applications. This article introduced a high frequency standing-wave thermoacoustic heat engine-driven pulse tube cooler system working around 300 Hz with axial length being 1.2 m. To improve the thermal efficiency of such system, an optimization has been carried out, both analytically and experimentally, by observing the influence of the dimensions of the stack, the hot buffer length and the acoustic pressure amplifier tube length. So far, a no-load temperature of 68.3 K has been obtained with 4.0 MPa helium and 750 W heating power. With 500 W heating power, a no-load temperature of 76.9 K and 0.2 W cooling power at 80 K have been achieved. Compared with former reports, the performance has been improved.     

新型热声制冷-双作用行波热声制冷机热力特性的数值模拟研究

对一种新型热声制冷系统—双作用行波热声制冷机进行了研究,设计了一台在气液双作用行波热声发动机上使用的行波制冷机,并通过数值模拟优化了制冷机的结构尺寸。在环境温度300K,制冷温度250K的条件下,新型的双作用制冷机的COP达到了2.74,相对卡诺效率接近60%,声功消耗为534W,制冷量为1464.9W。通过对传统的斯特林制冷机及不同结构的行波制冷机计算比较。结果表明:从压比、效率、制冷量等多角度考察,新型的双作用行波制冷机更适合与气液双作用行波热声发动机耦合工作。它具有潜在的高效率、热驱动及无运动部件的优点,非常有潜力成为常规制冷方式的一种替代技术。