强迫对流条件下圆柱体热源的构形研究

建立导热基座上的三维圆柱体热源散热模型,分别以最高温度和最大温差为指标,研究层流流动条件下热源半径、强度和位置以及热源和基座的导热系数对圆柱体热源构形优化的影响。研究结果表明:当给定热源强度和热导率时,存在一个临界半径使得热源最高温度取最大值;存在一个最佳半径使得热源的最大温差取最小值。热源最大温差和热源最高温度不但不能同时达到最佳,而且此高彼低。热源最高温度和温度均匀性则分别是在流体入口处和出口处达到最佳。在实际热设计中,应尽量避开临界半径以防止热点烧损,同时应注意考虑热源半径大小和热源位置的最佳折中。当给定热源半径和位置时,提高热源的导热系数,可以减小热源的最高温度,且减小其最大温差;提高基座的导热系数,可以减小热源的最高温度,但其最大温差增大。在实际热设计中,应尽可能提高热源的导热系数,对基座导热系数则应折中取值。文中所得结果可为电子元器件热设计提供理论支撑。     

TJ376Q活塞组件优化设计

设计活塞组件时，要以尽可能小的质量达到必要的强度和刚度，因此，在满足机械要求的前提下，应尽可能减小活塞组件的质量，试验结果表明经改进设计的活塞满足TJ376Q汽油机的性能要求。     

燃气轮机燃烧室过渡段“多造型函数组合”的设计方法

提出了一种"多造型函数组合"的燃烧室过渡段气动造型设计方法,包括设计原则、技术路线以及坐标系设置、进出口轮廓线离散化等设计步骤,并给出了中心线为SS形、SU形和凹形3种典型气动造型的设计示例。对于出口环扇形圆角半径较小和圆心角较大的2种特殊情况,给出了改进的设计方法和设计示例。结果表明:所提方法可便捷地设计出从进口圆形平滑过渡到出口环扇形的多种几何形状,适用于范围较广的气动造型设计,可作为燃烧室过渡段设计的重要手段。     

普通弯管机弯制小弯曲半径蛇形管的方法

本文利用普通弯管机弯制小弯曲半径蛇形管的方法，并从弯制小弯曲半径弯管方法的比较、选用、普通弯管机的改进、模具的设计及调整等几个方面叙述在普通变管机上弯制小弯曲半径蛇形管的模具设计及防止椭圆度超差的方法及其可行性。     

平衡重的配置对直列六缸柴油机主轴承负荷的影响

文中对七种平衡重配置方案的轴承负荷进行了计算分析,推导了一组确定平衡重质量矩的计算公式和曲线,这有利于平衡重的设计,并为研究轴承磨损和可靠性提供参考。     

多缸柴油机曲轴平衡重的合理配置

在外部平衡性能良好的曲轴上加装平衡重，通常是为了减小曲轴所受弯矩，但平衡重的安装将影响主轴承载荷的大小和分布。经过大量计算求得了一个工作循环中轴承载的最大值，平均值及其比值随平衡重增大而变化的规律。由此得出，合理的重配置应使轴承载荷的最大值达到最小。基地此结论导出了几组平衡重计算公式。文末还给出了算便。     

“Π”形膨胀节挠性设计计算研究

本文通过对大功率汽轮机低压缸“Π”形膨胀节挠性的计算分析,得出判别其设计好坏的标准是;“Π”形膨胀节外圈底部的变形和应力应尽量小;“Π”形膨胀节各部位的应力应在允许值范围内;“Π”形膨胀节的结构应易于制造.     

平衡重的最佳设计

只要平衡了给定的力偶而又不与其它部分发生干涉时,高速内燃机的平衡重就可以作成任意形状。设计平衡重时,通常是平衡全部的旋转质量以及50～60%的往复运动质量,平衡重可以用螺栓固定在曲柄臂上或与曲柄臂做成整体。在单缸发动机中应该避免不平衡,而在多缸发动机中虽然自身不用平衡重就可以平衡,但用平衡重平衡后就可以使轴承负荷与曲轴箱应力减到最小。     

月牙形轴颈的轻质量平衡轴设计

在采用平衡轴系统的活塞式引擎中,由于曲轴系统振荡而产生的二阶往复惯性力可以由带有平衡重的平衡轴来抵消,因此在对平衡重进行优化设计以及对轴颈重新设计后,平衡轴的重量可以得到很大的降低,这对于相似类型的平衡轴优化设计具有参考意义。     

消声器内部流场及温度场的数值分析

对一典型结构消声器的内部流场及温度场进行了数值模拟研究，并就消声器内部气流速度、温度变化对消声性能的影响进行了分析。消声器设计应遵循以下原则：穿孔管小孔总的流通面积应大于排气管口的面积；应充分利用气流与声波流的逆向作用来提高消声效果；消声器入口段应尽量采用均匀过渡结构；出口直径不宜过小。     

微小空腔内气体的预混燃烧

采用Longwell良搅拌反应器模型和详细化学反应机理对微尺度空腔内气体预混燃烧过程进行了零维数值模拟,从微腔体内稳定燃烧的临界半径、点火极限以及稳定流率范围着手,分析了不同预混气成分、不同当量比和不同环境对流换热系数等外部条件对微尺度燃烧点火与熄火特性的影响.稳定燃烧时,大腔体可对应较大的上极限流率,低预混气流率可对应较小的下临界半径;腔体越小(或流率越大),系统启动所需的温度和压力越高.     

基于最大内接的圆曲线拟合算法编程

圆曲线拟合方法有多种,如机械元件配合的需要,必须对圆形件的测量样本点进行“最大内接圆”（或“最小外接圆”）进行拟合。目前解决这一问题多为近似算法。笔者通过论证以说明“最大内接圆”必含于特殊圆的集合之中,该集合由所有过三点的内接圆（含内切圆）构成。通过逐步逼近的方法,遍寻满足条件的内接圆,构成内接圆集合。最后通过半径比较,找出符合“最大内接”的圆拟合曲线。     

Heat Transfer in a Horizontal Cylinder With Eccentric Surfaces

Heat transfer in horizontal cylinders exposed to free convection and radiation is of importance in many industries. Usually this problem is treated by adopting a concentric geometry, disregarding that the external surface temperature is not uniform. If an eccentric geometry is used, the external surface temperature should have a larger variation, changing the flow around the cylinder and the heat transfer coefficient, either improving or reducing the heat transfer. A numerical analysis is presented of the heat transfer in a horizontal cylinder with an internal isothermal surface eccentric to the external surface that is exposed to air free convection and radiation. The conduction problem was solved analytically and integrated numerically, while the free convection was solved by the PHOENICS software. The parameters analyzed were the ratio of radius, the ratio between the material and air thermal conductivities, the Rayleigh number, the emissivity of the outer surface, and the eccentricity between the external and inner surfaces. The parameters of a proposed equation to estimate the total heat of an eccentric arrangement in terms of the total heat of the corresponding concentric arrangement and the ratio between the convective and conductive thermal resistances were determined for given ratios of radius and eccentricities.     

The performance of a centrifugal fan with enlarged impeller

The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller–volute gap.     

循环流化床锅炉对排渣和供风系统的要求

从循环流化床锅炉的工作原理出发,结合百余台实际运行的循环流化床锅炉的实践,分析了锅炉性能对排渣、配风以及燃料、石灰石系统的要求.提出了有效床存量的概念、床压控制的原则、一次风机压头选择的依据.认为风帽阻力是漏渣的根本原因;在排渣粒度可以保证的条件下,且物料平衡系统对选择性排渣有要求时,尽量采用床下连续排渣、流化床冷渣器;考虑燃料的适应性和运行灵活性,建议送风机流量储备系数宜为1.25,压力储备系数1.3,而引风机的流量储备系数为1.25,压力储备系数1.20;若是燃用生物质等易燃燃料,储备系数还应更大一些.     

Conditions of Single-Valuedness of Rotation and Displacements for Non-Homogeneous Materials in Plane Thermoelasticity

The conditions of single-valuedness of rotation and displacements in the multiply connected regions for non-homogeneous materials are discussed theoretically by using the stress function. As an example of a multiply connected region, we have considered the steady thermal stresses in a functionally graded hollow circular body with an eccentric outer circular boundary. The material properties are expressed by the power law of the radius of the inner circle. The inner boundary conditions are satisfied strictly, whereas the outer boundary conditions are satisfied numerically using a point-matching method. Steady thermal stresses in the body are shown for ZrO₂/Ti-6Al-4 V functionally graded materials (FGMs). The results were verified by comparing with those of a functionally graded hollow circular cylinder.     

Effects of window size and thermal mass on building comfort using an intelligent ventilation controller

A prototype microcomputer-controlled thermostat was developed that can manage airflow according to cooling the needs in a building and the resources in the environment. This intelligent control system measures both indoor and outdoor temperature and uses decision rules to control a whole-house fan, in addition to the furnace and air conditioner. No such residential thermostat is currently commercially available. This paper presents the controller strategy that optimizes cooling with outdoor air. This paper also quantifies the effects of modifying the amount of thermal mass and the window area on indoor comfort when using this controller. These test confirm that smaller windows and more mass performed better than larger windows and less mass, and that higher volumes of controlled ventilation outperformed fixed ventilation rates.     

Effects of geometrical parameters of a dish concentrator on the optical performance of a cavity receiver in a solar dish‐Stirling system

Dish‐Stirling concentrated solar power (DS‐CSP) system is a complex system for solar energy‐thermal‐electric conversion. The dish concentrator and cavity receiver are optical devices for collecting the solar energy in DS‐CSP system; to determine the geometric parameters of dish concentrator is one of the important steps for design and development of DS‐CSP system, because it directly affects the optical performance of the cavity receiver. In this paper, the effects of the geometric parameters of a dish concentrator including aperture radius, focal length, unfilled radius, and fan‐shaped unfilled angle on optical performance (ie, optical efficiency and flux distribution) of a cavity receiver were studied. Furthermore, the influence of the receiver‐window radius of the cavity receiver and solar direct normal irradiance is also investigated. The cavity receiver is a novel structure that is equipped with a reflecting cone at bottom of the cavity to increases the optical efficiency of the cavity receiver. Moreover, a 2‐dimensional ray‐tracking program is developed to simulate the sunlight transmission path in DS‐CSP system, for helping understanding the effects mechanism of above parameters on optical performance of the cavity receiver. The analysis indicates that the optical efficiency of the cavity receiver with and without the reflecting cone is 89.88% and 85.70%, respectively, and former significantly increased 4.18% for 38 kW XEM‐Dish system. The uniformity factor of the flux distribution on the absorber surface decreases with the decreases of the rim angle of the dish concentrator, but the optical efficiency of the cavity receiver increases with the decreases of the rim angle and the increase amplitude becomes smaller and smaller when the rim angle range from 30° to 75°, So the optical efficiency and uniformity factor are conflicting performance index. Moreover, the unfilled radius has small effect on the optical efficiency, while the fan‐shaped unfilled angle and direct normal irradiance both not affect the optical efficiency. In addition, reducing the receiver‐window radius can improve the optical efficiency, but the effect is limited. This work could provide reference for design and optimization of the dish concentrator and establishing the foundation for further research on optical‐to‐thermal energy conversion.     

Pr对具有表面蒸发环形池内热毛细对流的影响

为了了解普朗特数对具有表面蒸发的环形液池内热毛细对流的影响,对流体在其纯蒸汽环境中蒸发时的热毛细对流进行了数值模拟,流体Pr变化范围为0.01至50.00,环形液池半径比和深宽比分别为0.5和1.0。结果表明,随着Pr的增加,表面温度逐渐升高,表面蒸发质量通量增大,热毛细对流流胞逐渐向外壁和自由表面移动,这种影响随着蒸发Biot数增加而逐渐减小;当蒸发Bi较小时,总蒸发质量随Pr增加而增大,当Bi较大时,Pr对总蒸发质量影响很小。     

活塞裙部廓形的计算机辅助分析

在分析活塞裙部廓形的基础上，建立了其横向廓形的通用数学模型，并采用最小二乘法求解其廓形参数，使求解过程大大简化。此外，对椭圆－偏心圆规律的廓形，提出了改变拟合点数寻求最佳型线参数的方法。提出的方法不仅适用于标准椭圆型线及其１阶、２阶近似型线，而且对椭圆－偏心（正）圆等组合廓形参数的求解同样有效，克服了现有方法的缺陷，具有很好的通用性。实例计算表明，本文方法的通用性和精度均较好，具有较好的工程实用价值