基于能量梯度理论双吸式离心通风机失稳研究

本文利用定常的三维Navier-Stokes方程和RNG k-ε湍流模型,对双吸式离心通风机的内部三维流动进行了数值模拟,并应用能量理论处理不同工况下的全流场流动参数,获得了能量梯度函数K的分布,并且对不同流道内压力面和吸力面上的静压分布进行了分析.研究表明,双吸式离心通风机叶轮出口区域是容易激发流动不稳定的关键位置;在叶道子午面上,沿轴向越接近轮盖处,流动越容易出现不稳定;同一工况下沿叶轮旋转方向接近挡流板的流道内的流动相较于其它流道内流动更容易出现失稳。     

向心式压气机的数值模拟及优化

根据某一压气机级的设计要求,采用向心式结构,合理地设计向心式压气机的气动参数和叶型参数,然后采用ANSYS-geometry对叶片型线进行参数化设置,最后在Workbench平台上对此向心式压气机进行数值模拟和优化。根据数值模拟结果,分析其内部流场流动结构,找到向心式压气机的较优工况;再研究优化后该向心式压气机的总压比、效率随相对流量和转速变化的特性曲线,分析向心式压气机的变工况特性。     

规则结构多孔填料塔两相流动特性实验研究

本文以空气和水为工质,对规则结构多孔填料塔的气-液逆向流动特性进行了可视化实验,研究了填料塔内气一液两相流动规律.实验结果表明:当液体流量一定时,随着气体流量的增加,压力损失增大;当气体流量一定时,随着液体流量的增加,气相压力损失增加.根据实验结果提出了采用水力雷诺数、韦伯数和无量纲流动参数的填料塔内气-液两相流动阻力系数实验关联式.     

流动聚焦微通道中双重乳液乳化行为研究

本文基于VOF(Volume of Fluid)相界面追踪方法,建立了流动聚焦微通道中双乳液液滴形成的模型,研究了互不相溶的三种流体在微流控系统中形成双重液滴的典型物理过程,给出了双重液滴形成的典型工况,分析了流动参数和工质物性对液滴形成过程的影响。结果表明:双重乳液液滴形成过程可分为滴式与喷式两种模式;外流体流量增大时液滴形成模式由滴式转变为喷式,所形成的双重液滴尺寸减小;中间流体流量变化对液滴形成模式、所形成的双重乳液内液滴尺寸影响不明显,外液滴随中间流体流量增大而增大。     

有气流扰动下管流油水混合物粘度实验测量与计算模型

采用局部即时取样方法对水平管内油气水三相流动情况下各种混合比例的复杂混合物的流动粘度进行了实验研究,实验工质采用46号机械油、自来水和空气。以实验数据为基础提出了考虑流动参数变化影响的反相点预测关联式。考虑到管内油水两相的混合发展过程,以局部即时取样的实验数据为基础,提出了一个气流扰动下管内流动条件下油水混合物粘度的预测关系式,该模型考虑了油水两相本身的物性以及流动因素的影响。指出考虑流动参数影响的粘度预测模型能大大提高油气水三相流动情况下油水混合物实测粘度的预测精度。     

圆管管翅散热器肋侧主流方向绝对涡通量研究

本文以圆管管翅式散热器为研究对象,采用数值模拟的方法对圆管管翅式散热器肋侧空气通道主流方向绝对涡通量的特性进行了探讨。给出了肋侧空气通道主流方向绝对涡通量无量纲化参数,二次流雷诺数;横向管间距、肋侧空气流动雷诺数对二次流雷诺数及努塞尔数的影响。     

内聚锥形激波的非均匀强化与结构演变特征

以高超声速内转式进气道流动中的激波汇聚问题为背景,考虑工程实际中的来流和壁面几何条件这两个关键因素,分别提出了以来流攻角为研究参数的非轴向来流内锥流动模型,和以长/短轴比为研究参数的椭圆入口内锥流动模型.采用激波风洞实验观测和数值模拟相结合的方法,揭示了两类流动中激波的非均匀汇聚特征.结果表明:由来流攻角引起的激波初始...     

低反动度附面层抽吸式压气机及其内部流动控制

本文进一步分析了低反动度附面层抽吸式压气机概念,并讨论了该压气机的设计要点和应用范围;分析了抽吸掉的附面层内的低能高熵流体的可能利用途径,以及对于不同的利用方式,效率的评估方法;基于上述概念设计了一台亚声速低反动度附面层抽吸式压气机,详细地分析了该压气机的气动参数选取与分布特点,以及该压气机内部的三维分离流动及其控制规律.     

氦流体的格鲁尼森数

格鲁尼森数是已知诸热力参数中对流体的临界点最不敏感的参数之一,将这个通常描述固体热力学性质的格鲁尼森数应用于描述非理想流体的流动可以给出合理的结果。本文计算了氦在不同的温度和压力下的格鲁尼森数,给出了广宽流动区域内氦的格鲁尼森数的普遍关联式,与用标准热力参数值计算结果的最大误差小于5％。     

螺旋管内高压汽水两相流不稳定性试验研究

本文在3—10MPa压力范围内,对内径为12mm的立式上升流动螺旋管内高压汽水两相流不稳定性进行了试验研究,得到了不稳定性的脉动曲线和各参数的影响以及预报系统稳定性的界限图,给出了依据系统参数预报稳定性的关系式。     

交变流动回热器的热声功能和回热功能

本文从解析的角度论证了交变流动回热器不仅具有经典热力学理论所认为的回热功能,而且具有热声理论所论述的热声功能,并指出交变流动斯特林热机进行的不是传统热力分析认为的两个等温过程和两个等容回热过程组成的斯特林循环。     

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.     

耦合高压斯特林制冷效应的复合磁制冷循环的数值模拟

本文借助计算流体力学软件, 对复合磁制冷机进行整机数值模拟分析. 以复合磁制冷机为建模原形, 分别计算了主动式磁制冷循环以及复合磁制冷循环. 利用模型计算分析了利用系数, 工作频率对主动式磁制冷的制冷效果影响, 同时模拟计算了不同相位角、不同频率下的复合磁制冷机的制冷效果, 计算得到适合复合磁制冷循环的最佳匹配相位角. 模拟计算结果对后续实验台的设计搭建有很好的指导作用.     

基于Simulink的气动分置式斯特林制冷机仿真

利用等温模型分析法,建立了分置式斯特林制冷机的控制方程和数学模型,并将这一数学模型应用到Simulink平台上,采用Matlab/Simulink的动态模拟特性模拟了制冷机内部的压力、容积、质量等参数的动态变化规律,并对仿真模拟的结果进行了分析。程序采用模块化设计,具有一定的通用性。     

分置式斯特林制冷机失效分析

斯特林制冷机是红外探测器组件中一个关键的组成部分。目前我国斯特林制冷机的性能指标与国外同类产品差距缩短 ,但可靠性问题一直没有很好解决。文中介绍了斯特林制冷机的原理、双活塞对动型分置式斯特林制冷机的结构特点及表征参数 ;通过对产品研制开发过程中成品率低的原因分析 ,揭示了主要失效机理 ,对改进工艺和设计起到了参考和指导作用。     

Thermoeconomic analysis of an irreversible Stirling heat pump cycle

In this paper an analysis of the Stirling cycle in thermoeconomic terms is developed using the entropy generation. In the thermoeconomic optimization of an irreversible Stirling heat pump cycle the F function has been introduced to evaluate the optimum for the higher and lower sources temperature ratio in the cycle: this ratio represents the value which optimizes the cycle itself. The variation of the function F is proportional to the variation of the entropy generation, the maxima and minima of F has been evaluated in a previous paper without giving the physical foundation of the method. We investigate the groundwork of this approach: to study the upper and lower limits of F function allows to determine the cycle stability and the optimization conditions. The optimization consists in the best COP at the least cost. The principle of maximum variation for the entropy generation becomes the analytic foundation of the optimization method in the thermoeconomic analysis for an irreversible Stirling heat pump cycle.     

A stochastic approach to the hadron spectrum. I

In this paper the squared mass of the hadron is defined as a random variable, whose average is the measured quantity. This leads to a mass formula, of a unique type for mesons and baryons, with a general law for the spin variation of the coefficients. The central squared masses form an overall geometrical scheme; in the baryon case it contains trajectories which are a fine structure of the Regge trajectories. For the accurately measured masses the difference between the computed and experimental value lies within 5 MeV for mesons and baryons. The geometrical scheme will be the basis for the computation of the decay rates, to be developed in the next paper.     

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。     

斯特林制冷机振动数学模型的Laplace变换及仿真

通过对斯特林制冷机振动系统的研究,建立了系统的振动方程并进行了相应的Laplace变换,结合斯特林制冷机实际的工作状况,给出了振动系统在不同阻尼比条件下的仿真结果,该结论对今后斯特林制冷机的设计有一定的指导意义。     

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.