某舰用燃气轮机舷侧进气系统性能试验研究

与燃气轮机常规进气方式相比，舰用燃气轮机舷侧进气系统对风速、风向等环境条件更为敏感，从而影 响整体性能表现。为验证某舰用燃气轮机舷侧进气系统在不同进气方向下总体性能是否满足设计要求，本文搭 建了该进气系统比例模型，并在其中布置了滤清器、稳压室、消声器等损失部件模型，对舷侧进气系统在5个常 见的进气方向下的整体性能表现进行了试验研究，对M进气方向下7个关键截面上流场进行了详细测量。试 验结果发现，进气方向明显影响舷侧进气系统性能，进气方向垂直于百页窗时进气系统总阻力损失最小。进气 系统中前端部件，如百叶窗、滤清器、稳压室等部件流动损失受进气系统的影响较为明显，消声器等进气系统尾 端部件的流动损失基本不受影响。速度场测量结果表明，进气方向同样会影响进气系统出口截面上流动畸变情 况，变化趋势与进气系统总阻力损失变化趋势基本相反。试验结果表明，在不同进气方向下，舷侧进气系统设计 方案的总阻力损失、出口截面畸变、主机功率损失均满足设计要求。     

烟气除湿喷淋塔出口液滴逃逸率研究

为了降低火电厂烟气含湿量,以新型的上喷淋上进气喷淋塔为研究对象,采用FLUENT模型模拟喷淋塔内部两相流体的运动,并与实验验证,采用单变量分析方法研究烟气流速、喷淋液滴直径、喷淋速度、喷淋流量四种因素对出口液滴逃逸量的影响。研究结果表明：各操作条件对出口液滴逃逸量的影响程度：液滴直径>喷淋流量>进气速度>喷淋速度;出口液滴逃逸量随着喷淋流量和进气速度的增长而线性增长;在进气速度3.5 m/s下,当液滴直径小于1 mm时,逃逸量随液滴直径减小而迅速上升;当直径大于1 mm时,液滴逃逸量几乎为0,不受喷淋流量影响。     

国产25 MW燃气轮机进气室改型设计

为进一步提高国产25 MW燃气轮机进气稳定性、降低总压损失，首先计算分析了原进气室长、宽、高变化对总压损失及速度不均匀度的影响，确定了改进的独立进气室的主要几何参数，而后采用帕斯卡涡线对改进的独立进气室底面进行型线优化，采用圆弧曲线及维氏曲线对背面和部分底面进行型线优化。计算分析基于理想气体进口总压100 838 Pa，进口总温298.15 K，出口静压94 900 Pa的边界条件下开展。研究结果表明：相对于改进的独立进气室，采用型线优化的结构削弱了喇叭口前方形箱体内的涡流，进气室出口位置的速度不均匀度及总压损失均减小；相对于改进的独立进气室，选用圆弧曲线或维氏曲线优化型线，判定截面的速度不均匀度分别增加了0.13%，0.14%，总压损失分别降低15.58%，21.43%，内整流罩出口位置速度不均匀度分别降低0.28%，0.19%，总压损失分别降低13.73%，20.6%。     

YC某柴油机各缸EGR率均匀分布性研究

以玉柴某带EGR系统的柴油机为研究对象,建立了该发动机性能数值模拟的Boost分析模型;计算得到进气总管入口、EGR管出口和进气歧管出口的气体流量,再用Fire软件对气道内三维流场进行了数值计算;对比分析了不同EGR管引入角、不同EGR位置及结构对各缸EGR分配均匀性的影响。研究结果为EGR管最佳布置方案的确定提供了理论依据。     

两种阀门结构的部分进气涡轮在不同阀门开度下的性能研究

为满足日益严格的排放法规,可变截面涡轮增压器正广泛地应用于车用发动机,针对一种新型的部分进气可变截面涡轮增压器,采用数值研究方法对采用两种阀门结构的涡轮在阀门不同开度的性能及内部流场进行分析,掌握了在阀门小开度和大开度下两阀门结构涡轮的工作特性及内部流动损失的机理。     

热气机加热器及回热器中流量分配的分析及数值模拟

加热管内流量的分布对热气机的效率有重要影响,对于不同结构的加热器和回热器中的气体流动情况,使用FLUENT软件进行了三维数值模拟,对不合理的结构进行了改进,并从工艺性方面出发,提出了一种流量分配较均匀的加热器和回热器结构方案,为加热器和回热器的结构改进和生产提供了重要的理论依据。     

余热锅炉入口烟道数值模拟

余热锅炉入口烟道的不同结构对其速度场的分布会产生重要的影响.采用标准 k-ε两方程模型,对入口烟道的第1段仰角及其长度、入口烟道的总长度的改变以及加装导流板等情况进行了速度场的数值模拟.结果表明这些因素之间存在优化组合,使出口截面的速度分布趋于均匀,加装导流板可明显改善入口烟道内及其出口截面的速度分布均匀性.     

导流片结构对物流分配性能影响的实验研究

通过板翅式换热器物流分配问题的实验研究发现，不合理的导流片结构造成板翅式换热器内部物流分配极不均匀，以及在横向与纵向上物流分配不均匀的程度也不相同。同时提出了具有补液腔的新型导流片结构，并定义了新型导流片的结构参数。实验结果表明，采用新型的导流片可以有效的改进换热器内部物流分配不均匀的问题，同时还发现在实验的条件下结构参数为0．2的导流片具有最佳的导流性能，通过实验研究得到了不同导流片结构的物流分配不均匀特性与流体雷诺数之间的关系式。     

不同阀门结构在阀门小开度下对部分进气涡轮性能的影响

为了满足现在日益严格的排放法规,可变截面涡轮增压器正广泛的应用于车用发动机,针对一种新型的部分进气可变截面涡轮增压器,采用数值研究方法对采用不同阀门结构的涡轮在阀门小开度下的性能及内部流场进行分析,找出了两阀门结构在小开度下的流量调节能力的关系,掌握了两阀门结构涡轮流量相同时的涡轮工作特性和内部流动损失机理。     

不同阀门结构在阀门小开度下对部分进气涡轮性能的影响

为了满足现在日益严格的排放法规,可变截面涡轮增压器正广泛的应用于车用发动机,针对一种新型的部分进气可变截面涡轮增压器,采用数值研究方法对采用不同阀门结构的涡轮在阀门小开度下的性能及内部流场进行分析,找出了两阀门结构在小开度下的流量调节能力的关系,掌握了两阀门结构涡轮流量相同时的涡轮工作特性和内部流动损失机理。     

Numerical study of the inlet/outlet arrangement effect on microchannel heat sink performance

In this study, fluid flow and heat transfer in microchannel heat sinks are numerically investigated. The three-dimensional governing equations for both fluid flow and heat transfer are solved using the finite-volume scheme. The computational domain is taken as the entire heat sink including the inlet/outlet ports, inlet/outlet plenums, and microchannels. The particular focus of this study is the inlet/outlet arrangement effects on the fluid flow and heat transfer inside the heat sinks.The microchannel heat sinks with various inlet/outlet arrangements are investigated in this study. All of the geometric dimensions of these heat sinks are the same except the inlet/outlet locations. Because of the difference in inlet/outlet arrangements, the resultant flow fields and temperature distributions inside these heat sinks are also different under a given pressure drop across the heat sink. Using the averaged velocities and fluid temperatures in each channel to quantify the fluid flow and temperature maldistributions, it is found that better uniformities in velocity and temperature can be found in the heat sinks having coolant supply and collection vertically via inlet/outlet ports opened on the heat sink cover plate. Using the thermal resistance, overall heat transfer coefficient and pressure drop coefficient to quantify the heat sink performance, it is also found these heat sinks have better performance among the heat sinks studied. Based on the results from this study, it is suggested that better heat sink performance can be achieved when the coolant is supplied and collected vertically.     

汽轮机低压缸进汽结构变流量工况气动性能的研究

为了探究传统轴向分流和新型环形空腔两种出口导流形式对一型进汽结构变流量工况下气动性能的影响,采用全三维数值模拟的方法对分别带有两种出口导流形式的进汽结构进行研究,并通过分析出口气动参数变化规律,获得二者的变流量性能特性。结果表明：二者在流动损失方面无明显差别,但带有环形空腔出口导流形式的进汽结构在出口气流角均匀度和马赫数均匀度上性能突出,其气流角和马赫数在出口的分布规律也更接近压力级的实际来流情况,为压力级高效、安全运行提供保障。     

Investigation on inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet

The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct.     

船用柴油机多缸流动不均匀性的数值模拟与优化

采用数值模拟方法建立整机冷却水腔三维模型,研究大型船用柴油机的多缸流动不均匀性问题。分析了进出口位置和不同进口流量对流量不均匀度的影响。结果显示:冷却水腔进出口位置对各缸不均匀性有较大影响;进口位置布置于V型机端面中部,且出口位置靠近机体轴向中部,均有利于使各缸压力损失均匀并提高进水均匀性。对原冷却水腔结构优化后,流量不均匀度从7.10%下降至3.91%;各缸流量不均匀度基本不随进口流量的增加而变化;且A、B两列气缸流量基本一致。     

旋流喷嘴缩放型出口的流动特性

利用VOF(volume of fluid)方法对旋流式喷嘴气液两相流动进行了数值模拟.分析了缩放型出口结构功能和其内的流场特征.结果表明,喷嘴出口处液膜厚度和速度分布存在周向不均匀性.旋流室与出口段的结构连接方式较充分地利用了旋流室的加速功能,但也会造成流场方向强烈扭曲.随入口压力增大,出口液体的径向、切向和轴向速度均增大,而液体速度方向变化微小.收缩段和喉部上部对液体有加速作用;喉部能较平滑的引流;扩张段损耗了液体速度,但足够长的扩张段有控制液体喷淋方向作用.     

催化肋片对微燃烧室内燃烧特性的影响

针对带有催化肋片的微燃烧室内部的氢氧预混合燃烧过程,利用CFD计算软件建立数值模型,在实验验证的基础上进行了模拟计算。结果表明:不同流速下,燃烧室内布置催化肋片能提高燃烧室外壁面平均温度以及燃烧效率。在低流速时催化肋片布置越靠近入口,表面催化反应对气相反应的抑制程度越大;肋片位置越靠近出口,燃烧室外壁面平均温度越高。在高流速下,催化肋片位置越靠近出口,表面催化反应对气相反应的促进作用越明显,使得燃烧室外壁面温度分布越均匀、燃烧室出口截面温度越高。     

杏林湾排涝泵站竖井贯流泵装置进出水流道流态的数值分析

运用三维湍流数值模拟方法对杏林湾排涝泵站竖井贯流泵装置进出水流道流态进行数值模拟,分析进水流道的流场均匀度和出水流道的扩散均匀性,提出优化方案。模拟结果表明,优化后的竖井贯流泵装置,在均匀进流的条件下,进水流道内的水流流态较好,竖井两侧流道内的水流流速分布较均匀,未出现明显的漩涡、回流等不良流态,水泵进流均匀、平顺;出水流道通过设置中隔墩的长度,不仅水流流态得到一定改善,而且中隔墩两侧水流流量分配基本均匀,有助于保证泵站良好的出水条件。     

Numerical analysis on the effects of manifold design on flow uniformity in a large proton exchange membrane fuel cell stack

The size and configuration of manifold can affect the flow characteristics and uniformity in proton exchange membrane fuel cell (PEMFC) stack; then its efficiency and service life. Based on the simulation results of a single fuel cell considering electrochemical reaction, a stack model with 300 porous media is established to numerically investigate the performances of a large commercial PEMFC stack. The effects of manifold width and configuration type on the pressure drop and species concentration are studied by computational fluid dynamics (CFD). The results show that the uniformity for most cases of U-type configuration is better than those of Z-type configuration. For U-type configuration, a very good uniformity can be obtained by selecting anode inlet manifold width of 20 mm and anode outlet manifold in range from 25 to 30 mm; the uniformity is bad for all cathode inlet manifold width, relatively better uniformity can be achieved by adjusting cathode outlet manifold width. For Z-type configuration, bad uniformity is found for cathode inlet and outlet manifold with all width; a relatively good uniformity can be obtained with suitable anode manifold width of 35 mm. The research can provide some references to improve gas distribution uniformity in large PEMFC stacks.     

Thermal Characteristics of Paraffin Wax for Solar Energy Storage

A thermal energy storage medium must meet the requirements of a stable storage material with high heat capacity. Heat storage based on the sensible heating of media such as water, rock, and earth represents the first generation of solar energy storage subsystems and technology for their utilization is well developed. However, recently the heat storage based on the latent heat associated with a change in phase of a material offers many advantages over sensible heat storage. The most important characteristic of such a subsystem is its sufficient storage capacity. The PCM (phase change material) behavior is visualized by constructing an idealized model thermal capacitor subjected to simulated solar system environmental conditions which include thermal cycling utilizing the latent heat of paraffin for heating and cooling. The proposed model of the capacitor is of a flat plate geometry consisting of two panel compartments forming the body of the capacitor containing the paraffin, leaving at their inner surfaces a thin passage allowing the water flow. The whole structure is assumed to be insulated to minimize heat loss. Analysis solution is used to generate data about the temperature distribution, the melt thickness, and the heat stored in the PCM under two conditions of: (a) constant mass flow rate tests for various water inlet temperatures, and (b) constant water inlet temperature for various mass flow rates. A FORTRAN computer program is constructed to perform the analysis. It is found that water outlet temperature increases with time until it becomes nearly equal to the inlet temperature. Increasing the mass flow rate for a given inlet temperature, decreases the time required for outlet temperature to reach a given value. Increasing inlet temperature for a given mass flow rate gives a very rapid decrease in the time required for the outlet water temperature to reach a given value. Instantaneous rate of heat storage is determined from the inlet-to-exit temperature differential and measured flow rate. This rate is then integrated numerically to determine the cumulative total energy stored as a function of time. It is found that the instantaneous rate of heat storage decreases till reaching a nearly constant value. The total or cumulative heat storage as a function of time, showed a nearly linear trend in the mid-range time, and it increased with increasing inlet temperature.     

喷孔几何特征对变截面喷油孔空穴流动状态的影响

采用混合多相流模型及空穴模型相结合的方法,对喷油嘴激光打孔过程形成的变截面喷油孔内空穴流动现象进行数值模拟,重点分析喷孔几何特征对空穴流动状态的影响规律.结果表明,变截面喷孔内喷孔截面收缩或者扩张的程度及位置对孔内燃油空穴流动状态具有重要影响.截面收缩型的喷孔可在出口形成更大的空穴强度分布,利于促进燃油的初次分裂及雾化.截面扩张型喷孔可使得出口燃油速度分布更均匀,出口平均速度增大,从而提高流量系数;研究还发现,相对于直喷孔,变截面喷油孔内空穴流动状态对孔入口倒角变化的敏感性减小,这将有利于提高多孔喷嘴各孔流量及雾化的均匀性.