基于应变片的自由活塞斯特林制冷机位移测试研究

压缩活塞与排出器的位移大小及相位差对自由活塞斯特林制冷机的制冷性能具有极其重要的影响。文中通过对目前各种位移测试方法优缺点分析,结合自由活塞式斯特林制冷机自身特点,提出了采用应变片响应涡旋柔性弹簧形变来测量活塞和排出器位移的新方法。通过分析、设计和标定,建立了一套基于应变片的自由活塞斯特林制冷机位移测量系统。实验测试结果表明,该位移测量系统是可靠的,具有体积小、投资省等优点,且不需要特别的安装空间。     

高温超导用自由活塞斯特林制冷机理论研究

制冷机是制约高温超导器件的瓶颈.文中针对自由活塞式斯特林制冷机进行了理论研究,建立了自由活塞斯特林制冷机的热声模型,对充气压力、活塞的位移振幅、热端换热器温度和密封间隙进行了模拟.模拟结果显示,以最大制冷量为目标最佳充气压力为1.9MPa,增加活塞位移振幅、降低回热器热端温度以及减小密封间隙可提高制冷机的性能.     

自由活塞型斯特林制冷机热力学参数的无量纲分析

自由活塞斯特林制冷机由于其结构紧凑、制冷效率高、可靠性好而不断受到重视。自由活塞斯特林制冷机的热力学参数对整机制冷性能具有决定性影响。基于等温模型,对自由活塞斯特林制冷机进行了无量纲分析,通过引入无量纲制冷量,详细研究了死容积比、扫气容积比、温度比、位移相位角对整机热力性能的影响。其研究结果为不同温区的自由活塞斯特林制冷机热力参数设计提供了参考意见。     

空调制冷温区的电驱动大功率自由活塞斯特林制冷机的研究

液氮温区的自由活塞斯特林低温制冷技术研究已经较为深入,并且得到了初步商业化,但在空调制冷温区较大制冷功率(大于1000 W)的研究还不多见。考虑到自由活塞斯特林制冷技术采用氦气等惰性环保气体作为工作介质以及其结构紧凑等优点,本文研制了一台对置直线压缩机驱动的空调温区的千瓦级自由活塞斯特林制冷机,并对其工作特性和制冷性能进行了系统的测试。实验研究中,环境温度设定在35℃,考察了不同制冷温度、不同平均工作压力以及不同频率下制冷量、制冷系数等性能的变化情况。研究表明自由活塞制冷技术在空调制冷领域具有良好的应用前景。     

自由活塞斯特林热泵的理论与实验研究

自由活塞斯特林热机取消了传统斯特林热机的曲柄连杆结构,具有结构简单、高效率、高可靠性、寿命长等诸多优点。但目前的研究热点多集中于自由活塞斯特林发动机与制冷机,对自由活塞斯特林热泵的研究关注很少。本文设计了一台电驱动自由活塞斯特林热泵,首次提出并采用了热机部分反向布置的结构,彻底避免了高温端换热器对直线电机造成的不利影响,并给出了实验结果。该热泵在-20~50℃的泵热温差下获得了1.4的整机COP。利用热声理论,本文对该热泵进行了理论计算,并与实验结果进行了对比,初步考察了热泵在不同泵热温差、不同输入电功以及不同运行频率的工作特性。     

谐振电机耦合型双效自由活塞斯特林子系统性能实验研究

本文提出了一种谐振电机耦合型双效自由活塞斯特林系统,其主要部件有自由活塞斯特林发动机子系统、谐振电机以及自由活塞斯特林制冷机/热泵子系统。全文针对谐振电机耦合型双效自由活塞斯特林子系统分别开展了制冷/热泵子系统、发动机子系统制冷和热功转换特性的实验研究。电驱动制冷子系统实验结果表明,当平均充气压力为3.3 MPa,工作频率为60.0 Hz,水冷温度19℃时,实验系统制冷效果较为显著,输入电功130 W时无负荷的制冷温度可以达到-23.7℃。发动机子系统热驱动声功输出特性实验结果表明,系统充气压力的变化对于系统热驱动起振特性有着十分明显的影响。另外,当平均充气压力为2.9 MPa,水冷温度22℃,外接电阻1500 Ω时,系统的加热功率越高,系统的热功转换性能越好。本文所开展的谐振电机耦合型双效自由活塞斯特林子系统的实验研究对未来要进行的整机系统热驱动制冷实验奠定重要基础。     

千瓦级自由活塞斯特林发电机研究

自由活塞斯特林发电机具有结构简单、高效率、高可靠性、寿命长等诸多优点。但其研究机构多集中于美国,国内的相关研究很少,且缺乏实验研究。为此,本文按照热声理论设计了一台1 kW电功级自由活塞斯特林发电机,并对其进行了实验研究,主要考察了不同热源温度下发电机的工作特性,获得了最大762 W的电功输出,此时热电效率为19.1%,这也是目前国内所报道过的最高热电效率。同时,本文将实验与热声理论的计算值进行对比,结果表明,实验与计算结果能够较好地吻合。     

双作用自由活塞型斯特林发电系统性能研究

自由活塞斯特林发动机作为一种高效的能源转换装置,在可再生能源利用等领域有重要的应用前景。本文针对一种双作用自由活塞型斯特林发电系统,从声电耦合原理出发,推导了双作用斯特林发动机与直线电机之间的阻抗匹配方程,建立了发电系统的整机数值模型,并获得了加热温度、平均压力、活塞连杆直径、机械阻尼和间隙密封宽度等参数对整机性能的影响规律。结果表明,由于双作用活塞两侧同时存在较大的温差和压差,因此相较于单作用结构的系统而言,活塞间隙大小对该系统性能影响更大,这是导致效率变化的关键因素之一。经过优化计算,设计了一台四单元双作用自由活塞斯特林发电机,在加热温度600?C、放热温度20?C和平均压力8 MPa的额定工况下,每个发电单元可输出1.41 k W的电功,热电效率为40.8%,为后续实验研究奠定相关的理论基础。     

室温温区自由活塞斯特林制冷机设计

自由活塞斯特林制冷机作为一种新型制冷技术,具有效率高、可靠性好、结构紧凑、环境友好等特点.目前,室温温区自由活塞斯特林制冷机存在回热器声功利用量少、出口声功大等问题,导致排出器反馈声功大、尺寸大,给加工工艺和实际应用带来困难.本文基于SAGE软件,对室温温区自由活塞斯特林制冷机的核心单元结构进行了设计.通过多级制冷流程,提高制冷的声功利用,同时探究排出器对制冷性能的影响,寻找减小排出器直径的有效方法.在以制冷系数为优化计算目标、限制排出器行程的前提下,得到了不同核心单元直径的三级自由活塞斯特林制冷机可实现的最小排出器尺寸.计算结果显示,总核心单元等效面积相近时,三级自由活塞斯特林制冷机的排出器面积可减小至单级的49％.即多级制冷机有效减小了排出器尺寸,推动自由活塞斯特林制冷机在室温温区的应用.     

耦合型高频光纤振动传感器实验研究

提出了一种耦合型高频光纤振动传感器,并设计了相应的解调电路和信号处理系统.对高频振动信号的响应波形和频率进行了测量,研究了光纤传感器对不同的振动强度和不同方向的振动信号的响应,分析了不同结构和不同材质的传输介质对光纤传感器测量结果的影响.实验证明所设计的耦合型高频光纤振动传感器截止频率达到8 kHz,振幅测量灵敏度为325 mV/mm,频率和幅值响应误差小于1%.     

An experimental study on the phase shift between piston and displacer in the Stirling cryocooler

In the design of the split-type free displacer Stirling cryocooler, the motion of the displacer is very important to the cooling capacity, which depends on the working gas pressure, the swept volume in the compression space and the expansion space, the operating frequency, the phase shift between the piston and the displacer, and other factors. This study describes design and manufacture of the Stirling cryocooler actuated by the electric force of the dual linear motor. The cool-down characteristics of the cold end with laser displacement sensor in the expander of the Stirling cryocooler were evaluated. The charging pressure was 15 kg_f/cm² and the operating frequency was 50 Hz. The input power and the lowest temperature were about 32 W and 67 K, respectively. The displacement of the piston was measured by LVDTs (linear variable differential transformers), the displacement of the displacer was measured by the laser optic method, and the phase shift between piston and displacer was investigated. As the peak-to-peak pressure of the compressor increased, the peak-to-peak displacement of the displacer increased. The peak-to-peak displacement of the displacer increased in the range of 0–64.5 Hz (the resonant frequency of the displacer), but decreased steeply when the operating frequency was higher than the resonant frequency. Finally, when the phase shift between the displacements of the piston and the displacer was 45°, the operating frequency was optimum and was decided by the resonant frequency of the expander, the mass and cross-sectional area of the displacer and the constants of friction and flow resistance.     

Power-Optimal Control of a Stirling Engine’s Frictional Piston Motion

The power output of Stirling engines can be optimized by several means. In this study, the focus is on potential performance improvements that can be achieved by optimizing the piston motion of an alpha-Stirling engine in the presence of dissipative processes, in particular mechanical friction. We use a low-effort endoreversible Stirling engine model, which allows for the incorporation of finite heat and mass transfer as well as the friction caused by the piston motion. Instead of performing a parameterization of the piston motion and optimizing these parameters, we here use an indirect iterative gradient method that is based on Pontryagin’s maximum principle. For the varying friction coefficient, the optimization results are compared to both, a harmonic piston motion and optimization results found in a previous study, where a parameterized piston motion had been used. Thus we show how much performance can be improved by using the more sophisticated and numerically more expensive iterative gradient method.     

谐振电机耦合型双效斯特林燃气热泵系统研究

针对当前国家大力推行清洁能源技术和煤改气政策的供暖现状,本文探索了一种双效斯特林燃气热泵系统.全文基于热声学观点对系统进行了理论研究,并采用SAGE程序对其进行数值模拟和优化设计.计算表明,当加热、供热和冷端温度分别为923 K、333 K和273 K时,系统可获得的泵热量为7000 W,COPh为 1.79,系统?效...     

交变流动下间隙密封耦合气体轴承的特性研究

气体轴承是回热式热机的一项关键技术,它是利用气体代替润滑油作为润滑剂,在轴与轴承套之间构成气膜,是避免运动面与静止面直接接触的较为理想支撑元件。将间隙密封与气体轴承相结合,可以在实现密封的同时消除接触磨损。本文利用ANSYS Fluent对具有77 kW(声功)设计输出能力的活塞进行其气体轴承与间隙密封耦合特性的数值模拟与分析,指导该新型气路结构的优化设计,并验证其在大功率自由活塞斯特林发动机中应用的可行性。     

The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w...     

气液耦合振动对热声发动机性能的影响

进行了气液耦合振动驻波型热声发动机定量模拟.重点比较分析了单纯气体振动系统和引入[EMIM][BF_4]室温离子液体作为液体活塞的气液耦合振动系统的运行参数,并考察了液体活塞的质量对热声发动机谐振频率、压力振幅以及板叠热端温度等的影响.     

Cooling Cycle Optimization for a Vuilleumier Refrigerator

Vuilleumier refrigerators are a special type of heat-driven cooling machines. Essentially, they operate by using heat from a hot bath to pump heat from a cold bath to an environment at intermediate temperatures. In addition, some external energy in the form of electricity can be used as an auxiliary driving mechanism. Such refrigerators are, for example, advantageous in situations where waste heat is available and cooling power is needed. Here, the question of how the performance of Vuilleumier refrigerators can be improved is addressed with a particular focus on the piston motion and thus the thermodynamic cycle of the refrigerator. In order to obtain a quantitative estimate of the possible cooling power gain, a special class of piston movements (the AS motion class explained below) is used, which was already used successfully in the context of Stirling engines. We find improvements of the cooling power of more than 15%.     

Theoretical analysis of 2D acceleration laser sensor and several design parameters

Having adopted several sets of new technology and techniques, we have developed a new type of laser angle sensor that can be used to measure two-dimensional (2D) angle of moving target. On this basis, a new design for 2D acceleration laser sensor has been advanced. The optics-type sensor can be used to measure 2D acceleration of motion object, and it has high sensitivity, high precision and longer measuring range. Under these design parameters that are given in this paper, the measuring range will achieve 177 g, while its sensitivity is 13.5 s². The experimental results show that the measuring error is not greater than 0.1 g. In this paper, several design parameters and measuring results for 2D acceleration laser sensor are given.