某重型燃气轮机燃烧室燃烧流动的数值模拟

对某重型燃气轮机燃烧室燃烧天然气进行数值模拟,在模拟过程中采用了雷诺应力模型、EBU-Arrheniue湍流燃烧模型和六通量辐射模型来描述其燃烧流动过程,运用FLUENT软件求解了三维流场和温场分布.计算结果能够很好地反映该重型燃气轮机燃烧室燃烧流动特点,对预测燃烧室内的燃烧流动有一定参考价值.     

电控单体泵燃油喷射系统耦合仿真

以某一典型的电控单体泵供油单元、可压缩高压油管以及机械式一级弹簧喷油器组成的燃油喷射系统为原型,建立了电控单体泵燃油喷射系统和喷油正时控制策略的耦合仿真模型,为多学科领域复杂系统建模仿真提供了解决方案和系统工程设计的完整平台.     

自卸汽车举升机构动力学仿真分析

运用机械多体动力学分析软件ADAMS,建立了自卸汽车举升机构的动力学仿真模型,并对此机构进行了动力学仿真分析,分析所得结果对强度设计提供了依据。本文所用的分析方法,有很强的实践应用性,对于设计工作有一定的指导意义。     

贫油直喷燃烧室回火的数值研究

针对燃烧稳定性中的回火问题,对贫油直喷燃烧室的回火特性进行了研究.燃烧中的回火指的是火焰从燃烧室传入到了预混区中的这样一种现象,它包含了声波、湍流、燃烧之间的复杂的相互作用,是燃烧研究中的关键问题之一.利用Fluent中的混合分数/PDF平衡化学反应模型对贫油直喷燃烧室进行了大涡模拟,分别计算了冷态和热态下的流场,捕捉了贫油直喷燃烧室内回火的动态过程,其中亚格子模型采用WALE模型,燃油射流采用离散相模型.研究结果表明,大涡模拟能够较好地反映流场分布情况,贫油直喷燃烧室内存在中心回流区,模拟结果与实验结果吻合较好;贫油直喷燃烧室中的回火发生在中心流区域,回火时,中心回流区向上游移动,这促使了火焰的向上游传播,并最终导致了回火的发生.     

Numerical analysis of acoustic characteristics in gas turbine combustor with spatial non-homogeneity

Acoustic characteristics in an industrial gas-turbine combustor are numerically investigated by a linear acoustic analysis. Spatially non-homogeneous temperature field in the combustor is considered in the numerical calculation and the characteristics are analyzed in view of acoustic instability. Acoustic analyses are conducted in the combustors without and with acoustic resonator, which is one of the acoustic-damping devices or combustion stabilization devices. It has been reported that severe pressure fluctuation frequently occurs in the adopted combustor, and the measured signal of pressure oscillation is compared with the acoustic-pressure response from the numerical calculation. The numerical results are in good agreement with the measurement data. In this regard, the phenomenon of pressure fluctuation in the combustor could be caused by acoustic instability. From the numerical results for the combustor with present acoustic resonators installed, the acoustic effects of the resonators are analyzed in the viewpoints of both the frequency tuning and the damping capacity. It is found that the resonators with present specifications are not optimized and thus, the improved specification or design is required.     

电动燃油泵流道数值仿真及结构改进研究

针对电动燃油泵流道内液体流动规律复杂,工作效率需要改善的问题,运用Fluent软件对燃油泵内部流场进行仿真分析。基于雷诺时均N-S方程和标准K-∑湍流模型以及标准壁面函数法,采用三维非结构四面体网格划分方法,对包括不同叶片数、不同叶片夹角和不同叶轮厚度的燃油泵结构模型进行了数值模拟,得到了燃油泵内部流场压力云图和流线图。以燃油泵叶轮结构参数为变量,出口流量为目标函数,通过对仿真结果进行了数值拟合,得到了叶轮叶片数,叶片夹角,叶轮厚度和出口流量的一般规律。并通过燃油泵台架实验,对优选的燃油泵性能进行了验证。研究结果表明,实验数据与仿真结果基本吻合,且改进后的燃油泵流量提高了2.5%左右,其工作性能得到改善。     

Numerical investigation of NOx reduction in a sudden-expansion combustor with inclined turbulent air jet

Axisymmetric sudden-expansion geometry of a co-flowing methane-air diffusion flame is considered to investigate the effect of air inlet conditions on NO_x formation, flow field and temperature distribution using the k-? turbulence and β-PDF combustion model. The predicted results are in acceptable agreement with the published experimental and numerical data. The obtained results show that increasing air turbulence intensity results in considerable decrease in NO formation. Increasing the inlet angle of the air causes the NO formation to decrease due to raising vorticity strength. As a new index, the mass-averaged integral of vorticity magnitude is introduced to investigate the effect of altering inlet angle of the air on the flow field.     

气体辅助注射成型技术的应用与发展

本文首先阐述了气体辅助注射成型的工艺过程和技术要点 ,然后分析了该技术的实际应用和发展     

Effects of injection type on slot film cooling for a ramjet combustor

A slot film cooling technique has been used to protect a combustor liner from hot combustion gas. This method has been developed for gas turbine combustors. A ramjet combustor exposed to high temperature can be protected properly with a multi-slot film cooling method. An experimental study has been conducted to investigate the change of the first slot angle under recirculation flow and the influence of wiggle strip within a slot, which affects the film cooling effectiveness. The first slot angle has been changed to understand the effect of the injection angle on the film cooling effectiveness in a recirculation zone. The distribution of dimensionless temperature was obtained by a thermocouple rake to investigate the wiggle strip effect, and the adiabatic film cooling effectiveness on downstream wall was measured by a thermochromic liquid crystal (TLC) method. At the first slot position, the film cooling effectiveness decreases significantly because of the effects of recirculation flow. The lip angle of the first slot affects slightly on the film cooling effectiveness. The wiggle strip reinforces the structure of slot and keeps the uniform open area of slot. However, it induces three dimensional flows and enhances the flow mixing between the main flow and the injected slot flow. Therefore, the wiggle strip decreases slightly the overall film cooling effectiveness. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Kwanghoon Park received his M.S degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2007. He is currently working for an education of an officer as a drillmaster in Army Consolidated Logistics School. Kang Mo Yang joined the Republic of Korea Army in 2004. He is currently working towards the M.S. degree at the Department of Mechanical Engineering, Yonsei University. Keon Woo Lee received his M.S. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2008. In 2008, he joined the Doosan heavy industries & Construction Co, LTD, where he is a member of the IGCC Business Team. Hyung Hee Cho received his PhD degree in Mechanical Engineering from University of Minnesota, Minneapolis, MN in 1992. In 1995, he joined the Department of Mechanical Engineering, Yonsei University, Seoul, Korea, where he is currently a full professor in the School of Mechanical Engineering. His research interests include heat transfer in turbomachineries, rocket/ramjet cooling as well as nanoscale heat transfer in thin films, and microfabricated thermal sensors. Hee Cheol Ham received his PhD degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 2001. In 1984, he joined the Agency for Defense Development, Daejeon, Korea, where he is currently a Principal Researcher. Ki Young Hwang received his Ph.D. degree in Mechanical Engineering from Yonsei University, Seoul, Korea in 1994. In 1979, he joined the Agency for Defense Development, Daejon, Korea, where he is currently a principal researcher in the Airbreathing Propulsion Directorate.     

Measurement and simulation of fuel injection pipe pressure and study of its effect on the heat release in a direct injection diesel engine

Fuel injection pipe pressures are measured and simulated to study the effect of fuel injection system characteristies on the heat release in a direct injection diesel engine. The fuel injection simulation is based on a linear model. The governing equations are solved by the finite difference method. The measured fuel pipe pressures and the simulated fuel pipe pressures matched well to each other except for the interval when the nozzle is closing. The effects of the fuel pipe length and the nozzle opening pressure are tested. The longer fuel pipe length causes proportional retardation of the fuel injection time. The higher nozzle opening pressure results in increase of the maximum fuel pipe pressure and shorter combustion duration.     

柴油机喷油阀碰撞分析

喷油器是柴油机燃油供给系统中实现燃油喷射的重要部件,然而在其工作中,针阀常与针阀体产发生碰撞,产生很大应力,针阀体工作寿命相当有限。以某款柴油机的喷油器为例,在CATIA中建立喷油器的三维模型,导入Hypermesh中进行模型的简化和网格的划分,利用Hypermesh和ABAQUS的接口,在ABAQUS的显式动力学有限元模块进行瞬态力学分析,模拟出喷油器中针阀与针阀体的碰撞过程,发现与应力波理论推导出的经验公式计算出的应力值基本接近。采用有限元方法对喷油器进行力学分析,有利于喷油器的改进设计。     

Direct numerical simulation of channel flow with wall injection

The present study investigates turbulent flows subject to strong wall injection in a channel through a Direct Numerical Simulation technique. These flows are pertinent to internal flows inside the hybrid rocket motors. A simplified model problem where a regression process at the wall is idealized by the wall blowing has been studied to gain a better understanding of how the near-wall turbulent structures are modified. As the strength of wall blowing increases, the turbulence intensities and Reynolds shear stress increase rapidly and this is thought to result from the shear instability induced by the injected flows at the wall. Also, turbulent viscosity grows rapidly as the flow moves downstream. Thus, the effect of wall-blowing modifies the state of turbulence significantly and more sophisticated turbulence modeling would be required to predict this type of flows accurately.     

Numerical simulations of the combustor for waste insulating oil containing polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are classified as persistent organic compounds and used in many industries because they are incombustible, heat resistant and electrical insulators. Owing to their strong toxicity and bioaccumulative nature, their transboundary movements are controlled by the Basel Convention and their levels are monitored by United Nations Environment Programme (UNEP). One of the most general methods for treating PCBs-containing waste is high-temperature decomposition; the removal efficiency of PCBs is 99.999% at over 1200°C for a retention time longer than 2 s. However, relatively low temperatures or low oxygen levels can produce highly toxic substances such as dioxins and dibenzofurans. Therefore, the reactor for the decomposition of PCBs should be very carefully designed. In this study, numerical simulations have been carried out to design a reactor for waste insulating oil containing PCBs. The flow patterns and temperature distributions of the gas in the reactor are examined. The path lines of the fluid particles are analyzed from the numerical results and the detention time of the PCBs-containing oil in the reactor is calculated. On the basis of this result, we try to scale up from a pilot plant to a commercial plant.     

A simulation for prediction of nitrogen oxide emissions in lean premixed combustor

Chemical reactor networks (CRN) models were developed for lean premixed gas turbine combustor to predict the NOx emissions. In this study, CRN models are constructed based on the computational fluid dynamics (CFD) for both non-pilot and pilot flame cases. Predictions of NOx emissions in combustor with the developed models were made by using CHEMKIN code and full GRI 3.0 chemical kinetic mechanism in the CRN. The predicted results agree reasonably well with the experimental data obtained from a simplified test combustor for the GE7FA gas turbine. The effects of overall equivalence ratio, swirl angle and pilot fuel ratio on the NOx emissions were investigated.     

射流预冷却发动机用喷嘴的数值模拟

采用计算流体动力学（CFD）方法,对气液喷嘴射流冷却两相流场进行数值模拟,采用混合模型的连续方程、动量方程、能量方程,相间考虑了相对（滑流）速度和漂移速度,数值模拟了喷嘴在进气道内采用垂直气流喷射方式下的流场分布,分析了液滴在流场内的轨迹和速度,沿飞行轨迹计算分析了射流预冷却对发动机性能的影响.结果表明,采用喷流预冷却方式所形成的温度场、压力场均匀,压力损失不大,可满足压气机进口条件要求.     

温度梯度对热障涂层影响的模拟

采用热弹塑性有限元法,对热障涂层在不同温度梯度作用的过程中,由于材料系数不匹配而引起的应力和位移进行了模拟分析.结果表明,等效应力的大小随温度梯度的大小单调递减;界面最大位移随温度梯度单调递增.同时也发现,模型在不同温度梯度下存在一个最小位移;当材料属性和载荷一定时,将存在一个最佳涂层厚度,使得涂层总的位移最小.该结果对分析涂层寿命及失效机制有指导意义.     

环形节流孔径向静压气体轴承的数值仿真

以环形节流孔径向静压气体轴承为研究对象,介绍了静压气体轴承的结构形式和工作原理,对气体润滑理论基础Reynolds方程进行了分析,利用计算流体动力学软件FLUENT对气体轴承的流场进行仿真分析,求解出了轴承气膜的压力分布.在轴承几何参数不变的情况下,分析了承载力与空气质量流量随不同供气压力和偏心率变化关系,并研究了静压气体轴承在高速工作下,动压效应对承载力的影响.     

水平V型砧连续拔长工艺的数值模拟

对水平V型砧锻造法进行了连续拔长过程的数值模拟.以前的研究仅仅给出了单次压下拔长模拟结果,忽略了上一次压下所产生的变形对后续压下的影响,采用ANSYS有限元分析软件对水平V型砧锻造法实现了矩形截面毛坯连续拔长过程的数值模拟,分析了锻件横截面上的中心轴线横向应力分布.     

Integrated simulation of the injection molding process with stereolithography molds

Functional parts are needed for design verification testing, field trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process holds the best promise of reducing the time and cost needed to mold low-volume quantities of parts. The potential of this integration of injection molding with RP has been demonstrated many times. What is missing is the fundamental understanding of how the modifications to the mold material and RP manufacturing process impact both the mold design and the injection molding process. In addition, numerical simulation techniques have now become helpful tools of mold designers and process engineers for traditional injection molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for verification, which show that the present scheme is well suited to handle RP fabricated stereolithography (SL) molds.