10W@80K分置式气体轴承斯特林制冷机研究

为了同时满足冷量、重量、振动、寿命以及环境适应性的需求,开展了分置式气体轴承斯特林制冷机的研发。以气体轴承线性压缩机为驱动源,设计了一款大冷量分置式气体轴承斯特林制冷机。优选了制冷机的设计参数,系统研究了制冷机的运行频率、充气压力、降温时间与制冷量的变化规律,进行了相关实验研究,压缩机输入240Wac,制冷机输出性能指标达到10.2W@80K,验证了制冷机设计的合理性。     

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。     

增压透平膨胀制冷机转速性能试验研究

基于气体轴承、滚动轴承支撑下的某航空用空气透平膨胀机,进行不同转速下热力性能和机械性能的试验研究,给出了两种支承下的热力性能及机械性能对比试验结果,验证了气体轴承润滑在高转速运行的条件下的优越性。研究结果表明:抑制低频振动、提高工作转速,有利于提高增压透平膨胀机的制冷效果、机械效率。     

百瓦级气体轴承斯特林发电机研究

气体轴承斯特林发电机具有效率高、寿命长、体积小和重量轻等优点。为满足空间电源对效率及重量的苛刻要求,本设计斯特林发电机采用气体轴承支撑消除活塞磨损,并采用动磁式直线发电机、高效回热器等技术。通过建立等温模型和参数修正,对斯特林发动机进行参数设计。搭建气体轴承斯特林发电机实验台,在热端温度350℃、20℃水冷散热工况下,得到38.6W电功率输出,整机效率11%。其成功研制可为我国未来空间探测用电源的研制奠定基础。     

百瓦级气体轴承斯特林发电机研究北大核心

气体轴承斯特林发电机具有效率高、寿命长、体积小和重量轻等优点。为满足空间电源对效率及重量的苛刻要求,本设计斯特林发电机采用气体轴承支撑消除活塞磨损,并采用动磁式直线发电机、高效回热器等技术。通过建立等温模型和参数修正,对斯特林发动机进行参数设计。搭建气体轴承斯特林发电机实验台,在热端温度350℃、20℃水冷散热工况下,得到38.6W电功率输出,整机效率11%。其成功研制可为我国未来空间探测用电源的研制奠定基础。     

线性对置式压缩机非线性振动特性理论研究

在空间遥感探测任务中,斯特林和脉冲管制冷机广泛应用于红外探测器和低温镜头的制冷。压缩机是制冷机的主要运动部件,是影响星上振动敏感设备的重要振动源之一。为了研究压缩机的振动特性,采用两自由度系统对线性对称布置的压缩机进行了建模,其中考虑了压缩腔的气体弹簧力以及间隙气流阻力的非线性特性。然后采用龙格-库塔数值方法对非线性动力学方程进行了求解。此外,还分析了由两个对置活塞质量、阻尼、刚度不对称引起的振动力。发现压缩机输出的振动力是以驱动频率为基频的一系列谐波,随着质量、阻尼、刚度不对称程度的增加,振动力的各次谐波幅值均随着增大。     

透平膨胀机静压径向气体轴承优化设计

对静压径向气体轴承的承载性能进行了数值计算,分别研究了供气压力、偏心率、供气孔直径、数量、轴承间隙对轴承承载特性的影响。研究发现,在给定条件下,增加孔数,减小孔径并减小轴承间隙时,轴承具有最优承载特性。     

自由活塞斯特林发电机气体轴承的设计方法研究

自由活塞斯特林发电机是一种高效紧凑的外燃式热电转换装置。气体轴承是实现其动子无接触支撑下往复运动的技术方案之一,结合间隙密封技术,可有效提高斯特林发电机的可靠性和使用寿命。目前常用的自由活塞斯特林气体轴承技术主要针对的是小功率,其承载力要求不高,往往简单采用几倍于实际承载的设计思路以应对实际气路结构产生的较大差异,而对实际承载力与细致优化设计考虑较少并缺乏系统的优化设计方法指导。随着大功率斯特林热机的发展,气体轴承的准确设计要求越来越高,掌握其实际应用环境中的最基本特征是实现其高效优化设计的基础。因此,本文从最为简单的一维轴向流模型出发,结合流动的扩散效应和非轴向流效应修正,为气体轴承的设计提供一种快速的计算方法;同时对气体轴承参数进行无量纲分析,给出无量纲结构计算图表,为常规斯特林热机气体轴承的优化设计提供具有普适特性意义的分析方法。     

制冷用线性压缩机结构设计与动力分析

介绍了制冷用线性压缩机结构中活塞组件、容量调节机构和气阀等设计选型的解决方法,提出一种以R134a为工质,冷量为2kW的线性压缩机设计方案。建立线性压缩机动力系统数学模型,并对模型中主要非线性因素气体力进行分析,以活塞运动方向为判据区分压缩机的工作过程,最后通过MATLAB/Simulink平台建模仿真,分析动力系统设计参数对制冷用线性压缩机动力性能的影响。     

悬臂梁压电振子宽带低频振动能量俘获的随机共振机理研究

研究了利用系统非线性来提高悬臂梁压电振子宽带低频振动能量俘获效率的随机共振机理,通过增加一对矩形永磁铁对传统线性悬臂梁压电振子结构进行了改进,结果揭示:在外部非线性磁力作用以及合适的磁铁间距条件下,这种外加磁力悬臂梁压电振子会构成一个双稳系统,在外部宽带低频随机振动源激励下发生随机共振现象,且发生随机共振时的输出电压明显增大,从而可以扩展悬臂梁压电振子的共振频率范围、提高低频振动能量的转化输出. 关键词： 压电悬臂粱 振动能量俘获 宽带低频 随机共振     

Two-channel 100-MW microwave compressor for the three-centimeter wavelength range

We present the results of the studies of a 100-megawatt active two-channel compressor of microwave pulses for the three-centimeter wavelength range. The compressors of the transit and reflector types are excited at the TE₀₁ mode of a circular waveguide, and the energy is output by using resonance plasma switches. The channels of the compressors are connected to a microwave oscillator and a load via a special quasioptical 3-dB directional coupler with enhanced electric strength. The use of the quasioptical coupler allows one to ensure the decoupling of the input microwave line (by about 20 dB) and combine coherently the pulses compressed in each of the compressor channel. High-and low-power tests of the compressors have been performed and the wave phase in the compressed pulses has been measured. The pulses obtained for an incident power of 5 MW have a power of 40–53 MW, a duration of 40–60 ns, and a power gain greater than 10. The compression efficiency amounts to 55%. The stability and good reproducibility of the amplitude and frequency characteristics of the radiation from a two-channel compressor make it promising for use in the linear accelerators of charged particles. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 8, pp. 660–674, August 2008.     

Energy conversion and high power pulse production using miniaturemagnetic flux compressors

The design, construction, and testing of miniature, high-power magnetic flux compressors are presented and discussed. The magnetic flux compressors are located inside high-speed, 30-mm projectiles that are launched with a high-pressure helium gun to velocities of approximately 300 m/s. The large deceleration force created when the projectile impacts the ground is used to power the magnetic flux compressor. Initial magnetic flux compressor currents of 200 mA are amplified up to 230 times to reach a peak current approaching 50 A. The output peak power is on the order of 3.5 kW into a 1-Ω load with a pulse length of 100 to 150 μs. Good agreement exists between the experimental results and the theoretical predictions for peak output current     

Performance analysis of capacity control devices for heat pump reciprocating compressors

The present paper is concerned with the study of the application of capacity control devices on heat pump reciprocating compressors. Five typical control systems have been studied: variable speed, variable clearance volume, by-pass of the discharge gas, throttling of the suction gas and suction valve cut-off. A simulation model was developed for the analysis. The heating coefficient of performance and the compressor discharge temperature were chosen for the comparison between these five mechanisms. Model predictions revealed that variable speed and variable clearance volume should present the best results. Worst performances went to suction throttling and discharge gas by-passing, both of which present highly irreversible processes.     

Waveguide bridge as an element for energy extraction from a resonant microwave compressor

We present the results of theoretical analysis of the operation of a waveguide bridge as a device for microwave-energy extraction and the data of experimental studies of 3-cm compressors with energy extraction through the bridge. We determine conditions under which the bridge can be used as an efficient output device capable of doubling the output pulsed power of the compressor. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 216–222, March 2008.     

Interstage Pressures of a Multistage Compressor with Intercooling

This paper considers the criterion of minimum compression work to derive an expression for the interstage pressure of a multistage compressor with intercooling that includes the gas properties, pressure drops in the intercoolers, different suction gas temperatures, and isentropic efficiencies in each compression stage. The analytical expression for the interstage pressures is applied to estimate the number of compression stages and to evaluate its applicability in order to estimate interstage pressures in the operation of multistage compressors, which can be especially useful when their measurements are not available.     

空调压缩机变容量调节技术

压缩机变容量技术是空调系统节能的重要手段.系统总结了制冷空调压缩机各种容量调节方法,并对目前使用广泛的吸气旁通和气缸卸载变容量技术进行了详细阐述,对最新的冷媒泄出调节技术也做了介绍.     

Free-electron RF-pulse compressor

A spatially modulated (corrugated) electron beam provides Bragg-type scattering of two waveguide modes. This allows the use of corrugated beams as quick active elements in rf-pulse compressors. In an illustrative example shown with a peak power compression ratio of 20-40, a 10-20 ns output pulse with a peak power of tens of MW is predicted for a millimeter-wavelength compressor.     

考虑粘性及展向掺混的轴流和离心组合压气机流动分析

本文研究建立了具有复杂流道形状的一体化轴流和离心组合压气机内部流动的数值计算方法,考虑到湍流扩散和粘性掺混,对不同类型的组合压气机内部流场进行了计算,根据计算结果详细分析了压气机的流动特性和气动性能,为建立先进的轴流和离心组合压气机气动设计体系,提供了工程实用的计算机程序和设计分析方法。     

Designing a New 4:2 Compressor Using an Efficient Multi-Layer Full-Adder Based on Nanoscale Quantum-Dot Cellular Automata

Quantum-dot Cellular Automata (QCA) is novel prominent nanotechnology. It promises a substitution to Complementary Metal–Oxide–Semiconductor (CMOS) technology with a higher scale integration, smaller size, faster speed, higher switching frequency, and lower power consumption. It also causes digital circuits to be schematized with incredible velocity and density. The full adder, compressor, and multiplier circuits are the basic units in the QCA technology. Compressors are an important class of arithmetic circuits, and researchers can use quantum compressors in the structure of complex systems. In this paper, first, a novel three-input multi-layer full-adder in QCA technology is designed, and based on it, a new multi-layer 4:2 compressor is presented. The proposed QCA-based full-adder and compressor uses an XOR gate. The proposed design offers good performance regarding the delay, area size, and cell number comparing to the existing ones. Also, in this gate, the output signal is not enclosed, and we can use it easily. The accuracy of the suggested circuits has been assessed with the utilization of QCADesigner 2.0.3. The results show that the proposed 4:2 compressor architecture utilizes 75 cell and 1.25 clock phases, which are efficient than other designs.