多孔介质特性参数对燃烧温度及压力影响的数值模拟研究

考查了两段式多孔介质内预混气燃烧的温度与压力分布情况。建立了甲烷／空气预混气体在多孔介质内燃烧的二维数学模型,运用FLUENT软件求解瞬态控制方程的方法计算出燃烧稳定后多孔介质内的温度、与压力分布,并考查了不同当量比、多孔介质辐射衰减系数和导热系数对温度和压力分布的影响。结果表明,甲烷／空气预混气体在多孔介质中燃烧,当量比越大温度峰值越高,压力梯度越大;小孔介质辐射衰减系数的改变对温度分布和压力分布没有明显的影响,而大孔介质辐射衰减系数对温度分布和压力分布有较大的影响;增加多孔介质的导热系数,会使固相与气相温度均有所升高,燃烧区域压力降低。     

计及浮环变形的发动机增压器浮环轴承润滑分析

以涡轮增压器浮环轴承为研究对象,考虑了浮环热弹变形,基于浮环平衡方程,建立了浮环流体润滑计算模型.主要分析了不同工况下热变形和弹性变形对浮环轴承润滑性能的影响规律.计算中采用有限差分法求解Reynolds方程进行润滑分析,采用变形矩阵法计算轴承表面弹性变形.结果表明:浮环表面热变形对浮环润滑特性影响显著;轴负荷越小,浮环工作温度越高,浮环热变形量越大;浮环热变形对内、外膜端泄流量的影响程度和转速有直接联系,转速越高,热变形对内、外膜端泄流量的影响越大;内膜间隙越小,浮环热变形对润滑性能影响程度越大;与浮环热变形相比,浮环弹性变形对浮环润滑性能基本没有影响.     

基于空气动力循环的内燃机废气余热回收方法

为提高内燃机能量利用效率,提出了采用布雷顿空气循环回收内燃机废气余热能的底循环方案,并对其回收废气余热能的潜力进行了研究。针对不同的循环压力、循环空气流量和内燃机排气温度进行了循环多参数性能计算分析,得出该余热回收系统循环参数和内燃机排气温度对废气余热能回收效率的影响。研究结果表明:循环压力和空气流量范围受内燃机排气温度制约,排气温度越高,可用压力范围和空气流量范围越大,并且相应的回收效率也越高;分别存在一个最佳压力点和一个最佳空气流量点,使回收效率出现峰值。     

基于三维有限元波箔片模型的气体箔片轴承承载性能研究

波箔型空气动压轴承在小型高速旋转机械中具有广阔的应用背景,其承载性能受箔片弹性变形影响较大.通过三维有限元法建立箔片变形模型,采用气膜压力分布的二次分布逼近建立箔片弹性变形表达式,实现与气体润滑雷诺方程耦合求解;提出了小柔度步计算方法,以提高箔片轴承大偏心率运行下承载性能求解的稳定性.在验证气体箔片动压轴承求解算法准确...     

基于CFD的袋式轴承油膜特性的分析

利用CFD软件分析不同油膜厚度、转速、供油压力下袋式轴承的油膜特性。首先将UG软件建立的物理模型导入Workbench的Mesh软件中进行网格划分,再计算不同的油膜厚度、转速、供油压力下的袋式轴承的油膜压力分布;由于Workbench的Flunet里没有黏温方程的计算模型,则需要用Flunet里的udf自定义编程接口将编写的C++程序导入该软件的计算器中,求解袋式轴承在不同转速、油膜厚度和供油压力下油膜温度分布。结果表明:通过对袋式轴承的数值模拟可以看出,最佳的油膜厚度、转速、供油压力对袋式轴承的油膜特性及对旋转机械转子稳定性起着非常重要的作用。汽轮机启动运行时,在合理的转速范围内,转速越大,温升降低,油膜稳定性越好,汽轮机转子运行就越加稳定;最佳的油膜厚度和供油压力使袋式轴承油膜压力稳定,温升小,使承载能力提高,且保证汽轮机安全稳定运行。     

船用柴油机供油机构滚轮衬套混合热弹流润滑特性研究

以船用柴油机供油机构中滚轮–浮动衬套–滚轮销为研究对象,考虑其低速重载运行工况下衬套弹性变形,计入表面粗糙特征,构建了浮动衬套内外双层油膜混合热弹性流体动压润滑分析模型,并据此探究了内外层油膜间隙比、衬套宽径比、衬套厚度及其表面粗糙度对环速比、内外层最大油膜压力及承载能力等润滑特性的影响规律。结果表明：滚轮–浮动衬套–滚轮销结构运行过程中内层油膜厚度较小,润滑状态较为恶劣;低速重载工况下,衬套弹性变形与混合润滑效应不可忽略;宽径比越大、内外层间隙比越小,最大油膜压力越小,结构承载能力越强,但温升越高;混合润滑状态仅出现于衬套内层润滑油膜,且衬套表面粗糙度越大,润滑效果越差。     

柴油机润滑系统仿真计算与分析

利用Flowmaster软件对某柴油机润滑系统在额定转速1 000 r/min,机油温度工作从60℃到90℃每隔5℃的工况下进行仿真计算分析,得到润滑系统关键节点压力和流量,从而评价该润滑系统的工作性能并保证该柴油机润滑系统的工作可靠性。结果表明:不同机油温度下,机油泵压升能够保证润滑系统各轴承、喷油嘴的压力均在合理范围内,各元件节点流量均能满足正常的润滑需求;随机油温度的升高,机油黏性降低,润滑系统各节点压力均呈下降趋势。     

径向滑动轴承变形与润滑耦合设计的双间隙协调法

以重载油轴承和水润滑轴承为背景研究瓦面变形的区域性和润滑计算方法,对变形区用双间隙函数来表征,相应变形和润滑算法与无变形函数假设下的结果基本一致。针对热粘弹算法复杂、工程应用困难的问题,提出并构造了一种计入瓦块变形的轴承双间隙表征方法,该方法依据瓦体变形大小将轴承间隙划分为变形区和非变形区的两段圆弧,并以最小膜厚为等效目标构造轴承的等效双间隙,进而达到运用经典润滑理论及成熟计算方法解决重载轴承瓦体变形与润滑的耦合设计问题的目的。以某大型(直径800mm)重载(135t)轴承为案例进行多方法计算结果对比分析,表明双间隙协调法较一般流体润滑模型最小油膜厚度和最大油膜压力的计算精度大为提高。由于双间隙方法有效建立了瓦体变形-间隙-膜厚的映射关系,进一步探讨了通过控制瓦体变形来控制轴承间隙和膜厚的问题,为重载轴承、水润滑轴承优化设计和承载能力提升提供了新的思路。     

轴颈偏斜对径向滑动轴承静态性能的影响

研究了轴颈偏斜对径向滑动轴承静态性能的影响.推导了轴颈偏斜时油膜厚度表达式,计算中考虑温度变化,联解雷诺方程、能量方程与温粘方程,计算了不同偏斜角、不同偏斜方位时轴承的压力和温度分布,以及不同偏心率、不同偏斜角度时轴承的静态特性.结果表明:轴颈偏斜时,油膜厚度、油膜压力与油膜温度分布变化明显,最小油膜厚度出现在端部,最大油膜压力与最高温度均向轴承端部移动;对轴承静态性能的影响也较明显,油膜反力随偏斜角增大而增大,阻力系数随偏斜角增大而减小,对端泄油量的影响在不同偏心率时规律不同.     

四瓦可倾瓦轴承大偏心下润滑性能研究

目前对可倾瓦轴承润滑性能的研究普遍局限于轴承偏心率0~1的范围。以四瓦可倾瓦轴承为对象,研究轴承偏心率大于1,即大偏心工况下,可倾瓦轴承的润滑性能。计算某可倾瓦轴承瓦间承载下的静动特性参数并与典型瓦面承载计算结果对比分析,并针对支点系数0.5、比压为0.6MPa的实例进行具体说明。结果表明:可倾瓦轴承在常用比压下会出现轴承大偏心状态,瓦间承载下承载力、最小膜厚和油膜刚度等关键润滑性能随偏心率变化的曲线与瓦面承载下的曲线相比有明显的滞后特点。     

螺旋隔板光滑管单管换热器的数值模拟

采用FLUENT6.0软件对整个螺旋隔板光滑管单管换热器的流场、温度场和压力场进行数值模拟,并与实验测量和计算结果进行了对比,验证了数值模拟的准确性。流场模拟结果显示,流体在壳程呈螺旋状流动,没有死区,而且流速比较均匀,变化比较小,从而进一步验证了许多学者经过实验研究分析得出的螺旋隔板换热器具有的优良性能。     

Assessment of different bio-inspired flow fields for direct methanol fuel cells through 3D modeling and experimental studies

The performance impact of using bio-inspired interdigitated and non-interdigitated flow fields (I-FF and NI-FF, respectively) within a DMFC is investigated. These two flow fields, as well as a conventional serpentine flow field (S-FF, used as a reference), were examined as possible anode and cathode flow field candidates. To examine the performance of each of these candidates, each flow field was manufactured and experimentally tested under different anode and cathode flow rate combinations (1.3 mL/min [methanol] and 400 mL/min [oxygen], as well as 2 and 3 times these flow rates), and different methanol concentrations (0.50 M, 0.75 M, and 1.00 M). To help understand the experimental results and the underlying physics, a three dimensional numerical model was developed. Of the examined flow fields, the S-FF and the I-FF yielded the best performance on the anode and cathode, respectively. This finding was mainly due to the enhanced under-rib convection of both of these flow fields. Although the I-FF provided a higher mean methanol concentration on the anode catalyst layer surface, its distribution was less uniform than that of the S-FF. This caused the rate of methanol permeation to the cathode to increase (for the anode I-FF configuration), along with the anode and cathode activation polarizations, deteriorating the fuel cell performance. The NI-FF provided the lowest pressure drops of the examined configurations. However, the hydrodynamics within the flow field made the reactants susceptible to traveling directly from inlet to outlet, leading to several low concentration pockets. This significantly decreased the reactant uniformity across its respective catalyst layer, and caused this FFs performance to be the lowest of the examined configurations.     

柴油机活塞温度场和耦合应力计算

采用AVL BOOST软件对活塞的工作过程进行计算,得到了活塞的换热边界条件和最高燃烧压力;在此基础上,采用ANSYS有限元软件对组合式活塞有无冷却时的温度场和耦合应力及变形进行了分析计算;另外对活塞的连接螺栓进行了应力强度考核。     

A numerical and experimental study of chevron,corrugated-plate heat exchangers

In this work, the widely used chevron corrugated-plate heat exchanger was simulated, and the three-dimensional temperature, pressure, and velocity fields were obtained. From the temperature field we can see that in the first zone, the temperature gradient increases gradually and get the maximum; in the central of the flow, the temperature gradient becomes smaller again. The highest temperature appears around the upper port, while the lowest temperature appears in the cold fluid inflow around the lower port. From the pressure field, we can see that the fluid pressure is gradually reduced along the flow direction. From the flow field, no matter the fluid inflows or outflows the port, there is a marked “dead zone” departed from the corrugated side of the port, where the fluid flow rate is very low. The fluid flows along the side of the port and appears a minor's “bias” (uneven-distributed) phenomenon. Meanwhile, it can be seen that a large number of contact points are distributed in the chevron corrugated-plate heat exchanger. In addition, the simulated results are compared with the experimental values and found that trends of the outside temperature are consistent with those of pressure drop, and experimental values were similar to those of simulated values.     

330MW对冲燃烧锅炉燃烧和污染物排放的数值模拟

分别对330MW对冲锅炉在额定负荷、55％额定负荷工况下的流场、温度场、煤粉颗粒场和NOx场进行了模拟研究,模拟结果与实际运行经验吻合较好。通过研究得出了一些有参考价值的数据,对大型对冲燃烧锅炉的设计优化和安全运行具有较为重要的参考价值。     

瞬态电场测量系统的研制与试验

针对瞬态电场的测量,研制了一款以基于MSP430系列微处理器为核心,应用高速模数转化芯片与高速存储器的测量系统,所用球形探头具有体积小、功耗低、可编程和测量范围可调的特点。通过试验验证和改进,该测量系统能够满足电力系统中的电场测量要求。     

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。     

Numerical simulation of the effect of electrode insertion depth on melting process of self-supporting lining electric furnace

This research is on the melting process of slag in non-inner lining furnaces. In this electric furnace, slag is solidified into the lining of the inner wall during the melting process by means of water cooling of the outer wall. It is a self-supporting lining electric furnace. In this study, the slag melting process was simulated using ANSYS software, and the electromagnetic field, temperature field, and furnace lining thickness of the self-supporting lining were analyzed at different electrode insertion depths. The results show that the self-supporting lining can be formed under the three insertion depth of the electrodes, and the thickness of the lining increases with the insertion depth of the electrode.     

利用火焰图像同时重建温度场和浓度场的试验研究

煤粉火焰图像是火焰辐射经过发射、衰减和散射等过程后到达摄像机靶面的投影。火焰发射出的辐射强度与火焰自身的温度密切相关，而辐射强度的衰减则取决于弥散介质的特性和浓度。该文首先研究了辐射衰减系数与粒子浓度场的关系，提出了对温度场和浓度场进行同时重建的控制方程。最后，在小型燥粉炉上进行断面温度场和浓度场的重建试验。图ll参l2     

Design optimization of a solar tower power plant heliostat field by considering different heliostat shapes

The present study focuses on the optimization of solar tower power plant heliostat field by considering different heliostat shapes including rectangular, square, pentagon, hexagon, heptagon, octagon, and circular heliostat shapes. The optimization is carried out using an in-house developed code-based MATLAB program. The developed in-house code is validated first on a well-known PS10 Solar Thermal Power plant having rectangular heliostats shape and the resulting yearly unweighted heliostat field efficiency of about 64.43% could be obtained. The optimized PS10 heliostat field using different heliostat shapes showed that the circular and octagon heliostat shapes provide better efficiency with minimum land area. The yearly efficiency is increased from 69.65% for the rectangular heliostat shape to 70.96% and 71% for the octagon and circular shapes, respectively. In addition, the calculated field area (land area) is reduced for the case of circular and octagon heliostat shapes with a gain of about 11.10% and 10.93% (about 42.0436 × 10³ and 41.4036 × 10³ m²), respectively, in comparison with the PS10 field area.