单缸发动机惯性力测试校正理论与实验的研究

单缸发动机中曲柄连杆机构的惯性力的大小与方向对车辆的振动和舒适性有相当大的影响,在中小排量的发动机中一般采用过量平衡调整一次惯性力的方法,但长期以来缺乏有效的实验研究手段。讨论了单缸曲柄连杆机构的理论惯性力曲线“力椭圆”和实验惯性力曲线“力8字”的关系,提出在摆架上逐点偏移气缸进行惯性力实验的方法,得到的实验惯性力曲线完全反映了惯性力的主要参数。在单缸发动机惯性力数学模型的基础上,研究了曲柄连杆机构的合成旋转质量的位置及与往复质量的比值这两个重要的设计参数与一次最大惯性力、主趋角、不平衡率的变化关系,讨论了单缸发动机惯性力参数选择依据。提出了惯性力参数的实验校正算法。     

V6发动机整机振动控制的工程化实现

本文针对某V型90°夹角的6缸车用发动机,将发动机整机振动分析和控制工作与发动机的研制过程紧密结合,通过惯性力系平衡分析、振动激励力特性分析、悬置系统优化设计、悬置元件与悬置系统工程化设计等,实现了该V6发动机整机振动的工程化最优控制。通过台架整机振动测试及可靠性考核试验表明,本文所采用的一系列分析方法和工程设计是合理、可行和可靠的,对其它类型发动机的整机振动分析和控制具有现实的参考价值。     

H-PIPE对发动机扭矩曲线影响的研究

以一台V型6缸汽油机为例,利用1维CFD发动机模拟软件GT-POWER建立了整体发动机模型（包括进排气系统）,通过对H-PIPE直径、位置及长度的优化,研究了H-PIPE对发动机扭矩曲线影响,对如何优选H-PIPE参数以调谐发动机扭矩曲线具有指导意义。     

太阳能斯特林发动机气缸系统振源特性分析

以38 kW 4缸双作用斜盘式太阳能斯特林发动机为例,构建了其实体结构模型,针对气缸系统内部工质与活塞组件振源,应用Fluent软件对发动机气缸内工质的三维流动特性及脉动参数的时域和频域特性,活塞组件的往复运动惯性力、惯性力矩及其端面所受的气体力特性等进行了研究。结果表明:与吸热器相邻气缸内的工质压力脉动显著,且其脉动频率范围为10~50 Hz,而气缸内工质的流量脉动频率则主要在10~50 Hz和200~250 Hz两个范围内;活塞端面所受的气体力在工质的压缩与膨胀转换过程中大小、方向都会发生突变,引起活塞组件的振动冲击;单缸活塞组件的往复运动惯性力与惯性力矩均呈正弦规律变化,且相邻两缸之间相差90°相位角,整个气缸系统活塞组件的往复惯性力能自行抵消,而惯性力矩则需要通过合理设计平衡块质量及其与旋转轴心的距离才能达到平衡。     

90°V6柴油机平衡特性分析

推导和建立了V型6缸(V6)内燃机惯性力系平衡分析的通用公式,并针对某型号V型90°缸排夹角的6缸(90°V6)柴油机进行了整机平衡分析。由分析结果可见,该90°V6柴油机惯性力载荷已全部自平衡,而惯性力矩载荷均未平衡,是该机振动、噪声的重要激励成分,需要采取适当的措施予以控制。     

基于AVL EXCITE动力学分析的连杆静强度计算

以某型直列四缸发动机连杆为研究对象,采用多体动力学方法在AVL-EXCITE中建立连杆大头轴承润滑特性分析的弹性液体动力学(EHD)模型,着重进行了峰值油膜总压、最大粗暴接触压力、平均摩擦功率损失等参数的计算与分析;基于动力学结果提取连杆在典型转速工况下的惯性力、活塞销座力、油膜压力作为静强度计算的动态载荷,从而对连杆进行静强度分析。     

60°V8发动机平衡分析及平衡机构设计

本文对60°夹角的V型8缸发动机进行了平衡分析,并就该类机型平衡机构的设计进行了探讨,为某8V150柴油机优化设计了双轴平衡机构,使该平衡机构不但100％完全平衡了二次往复惯性力,而且最大可能地消减了侧倾力矩。经实验验证表明,本平衡方案极大地改善了该8V150柴油机的振动特性,解决了该类机型设计中的一大技术难题。     

现代先进发动机技术——平衡和振动(2)续

<正> 5.5 直列四缸机采用双平衡轴平衡二次惯性力 当直列四缸发动机一对曲柄销到达上止点或者下止点时,四个活塞和连杆的二次惯性力均达到最大值,方向均指向上止点。如果发动机气缸排量大于2 L,那么,在一定转速下发动机的垂直振动很显著,表现在发动机工作粗暴和振动强烈。 配置双平衡轴和平衡重可以抵消不平衡的二次惯性力,平衡重产生的离心力大小与四个气缸的二次惯性力相等(图61a-d)。平衡轴安装在曲轴下方,转动方向彼此相反,平衡轴由一对啮合齿轮驱     

排气系统尾管对发动机性能及排气噪声影响研究

以一台V型6缸汽油机为例,利用一维CFD发动机模拟软件GT—POWER建立了整体发动机模型（包括进排气系统）,通过改变排气尾管直径、长度设计参数,研究了排气尾管长度、直径对发动机性能和排气噪声的影响,并总结了如何适当选取尾管的长度、直径设计参数,以满足发动机性能和排气噪声的要求。     

降低CF4108T型柴油机振动方法及效果

直列4缸往复式柴油机由于其结构特点,在运转时其二阶往复惯性力不能自平衡,引起发动机产生较大的振动。在此类发动机上采用双轴平衡机构以平衡二阶往复惯性力可显著降低发动机振动。本文介绍了采用增加双轴平衡机构来降低CF4108T型柴油机的振动,包括平衡计算过程、振动测试结果。     

Heat Transfer in a Rotating Twin-Pass Trapezoidal-Sectioned Passage Roughened by Skewed Ribs on Two Opposite Walls

An experimental study of heat transfer in a radially rotating twin-pass trapezoidal-sectioned duct with two opposite walls roughened by 45° staggered ribs was performed. Two channel orientations of 0° and 45° from the direction of rotation were tested. At each Reynolds number of 5000, 7500, 10000, 12500, and 15000, local Nusselt numbers along the centerlines of two rib-roughened surfaces with five different heating levels were acquired at rotating numbers of 0, 0.1, 0.3, 0.5, 0.7, and 1. A selection of experimental results illustrates the isolated and interactive influences of convective inertial, Coriolis, and rotating buoyancy forces on local and centerline-averaged heat transfers. The isolated Coriolis force-effect improves heat transfer over two unstable surfaces of the rotating twin-pass channel. The rotating buoyancy effect undermines local heat transfer, but its influence is alleviated when the rotating number increases. At rotating number of 0.7 and 1, the rotating buoyancy force acting with counter-flow manner considerably impairs local heat transfer in the end-region of the first passage with radially outward flow. With the rotating numbers in the range of 0.1 to 1, the heat transfer differences between the two channels with orientations of 0° and 45° are in the range of 5–26%. As a strategic aim of the present study, heat transfer correlations are derived to evaluate the centerline-averaged Nusselt numbers over two rib-roughened surfaces that permit the individual and interactive influences of convective inertia, Coriolis force, and rotating buoyancy to be quantified. As the full-field spatial heat transfer variations in the present rotating channel are not measured, the local heat transfer results generated by the present study are limited to the locations measured.     

Heat transfer in a radially rotating square duct fitted with in-line transverse ribs

This paper describes an experimental study of heat transfer in a radially rotating square duct with two opposite walls fitted by transverse ribs. The manner in which rotation modifies the forced heat convection is considered for the case where the duct rotates about an axis perpendicular to the duct's axis of symmetry and the flow within is radially outward with particular reference to the design of a gas turbine rotor blade. A selection of experimental results illustrates the individual and interactive effects of Coriolis and centripetal buoyancy forces on heat transfer along the centerline of each rotating rib-roughened surface. A number of experimental-based observations are revealed those confirm the manner for which the Coriolis force and centripetal buoyancy interactively modify the heat transfer even if the rib associating flow phenomena persist when the through flow transverses the ribs. An empirical correlation based on theoretical consideration and experimental data, which is physically consistent, has been developed to permit the evaluation of interactive effects of rib-flows, convective inertial force, Coriolis force and centripetal buoyancy on heat transfer.     

Numerical investigation of developing convective heat transfer in a rotating helical pipe

Numerical simulation is carried out for heat transfer characteristics of flow in rotating helical pipes. A good agreement has been achieved compared with experimental data from literature. The impacts of both co-rotation and counter rotation on local heat transfer enhancement are discussed in detail. Different developing modes of heat transfer enhancement in laminar and transitional regions are observed. Streamwise variation of circumferential distribution of heat transfer enhancement by rotation exhibits sensitivity to rotation speed, rotation direction and curvature ratio. Within the range of De and Ro under discussion, the impact of streamwise inertial force is the major factor of heat transfer enhancement for co-rotational cases while the effect of reversed flow and accompanied Dean vortex for counter rotational cases cannot be neglected.     

Theoretical and numerical analysis of convective heat transfer in the rotating helical pipes

In terms of the tensor analysis technique, the relative N-S equations and the energy equation in a rotating helical coordinate system are presented in this paper. Convective heat transfer in the rotating helical pipes with circular cross-section is investigated employing theoretical and numerical method. A perturbation solution up to the secondary order is obtained for a small Dean number. Variations of the temperature distribution with the force ratio (the ratio of the Coriolis force to the centrifugal force), the curvature and the torsion are discussed in detail. Present studies also show the natures of the Nusselt number, as well as the effects of the force ratio, the curvature, and the torsion. This study explores many new characteristics of convective heat transfer in the rotating helical pipes and covers wide ranges of parameters.     

How far have we been? &#8213;Summary of investigations on rotating cavity at IDG,RWTH Aachen University

Annular cavities are found inside rotor shafts of turbomachines with an axial or radial throughflow of cooling air, which influences the thermal efficiency and system reliability of the gas turbines. The flow and heat transfer phenomena in those cavities should be investigated in order to minimize the thermal load and guarantee the system reliability. An experimental rig is set up in the Institute of Steam and Gas Turbines, RWTH Aachen University, to analyze the flow structure inside the rotating cavity with an axial throughflow of cooling air. The corresponding 3D numerical investigation is conducted with the in-house flow solver CHTflow, in which the Coriolis force and the buoyancy force are implemented in the time-dependent Navier-Stokes equations. Both the experimental and numerical results show that the whole flow structure rotating slower than the cavity rotating speed. The flow passing the observation windows in the experimental and numerical results indicates the quite similar trajectories. The computed sequences and periods of the vortex flow structure correspond closely with those observed in the experiment. Furthermore, the numerical analysis reveals a flow pattern changing between single pair, double pair, and triple pair vortices. It is suggested that the vortices inside the cavity are created by the gravitational buoyancy force in the investigated case, while the number and strength of the vortices are controlled mainly by the Coriolis force.     

How far have we been? —Summary of investigations on rotating cavity at IDG, RWTH Aachen University

Annular cavities are found inside rotor shafts of turbomachines with an axial or radial throughflow of cooling air, which influences the thermal efficiency and system reliability of the gas turbines. The flow and heat transfer phenomena in those cavities should be investigated in order to minimize the thermal load and guarantee the system reliability. An experimental rig is set up in the Institute of Steam and Gas Turbines, RWTH Aachen University, to analyze the flow structure inside the rotating cavity with an axial throughflow of cooling air. The corresponding 3D numerical investigation is conducted with the in-house flow solver CHTflow, in which the Coriolis force and the buoyancy force are implemented in the time-dependent Navier-Stokes equations. Both the experimental and numerical results show that the whole flow structure rotating slower than the cavity rotating speed. The flow passing the observation windows in the experimental and numerical results indicates the quite similar trajectories. The computed sequences and periods of the vortex flow structure correspond closely with those observed in the experiment. Furthermore, the numerical analysis reveals a flow pattern changing between single pair, double pair, and triple pair vortices. It is suggested that the vortices inside the cavity are created by the gravitational buoyancy force in the investigated case, while the number and strength of the vortices are controlled mainly by the Coriolis force.     

Convective mass transfer from a horizontal rotating cylinder in a slot air jet flow

The effects of air jet impinging on the mass transfer characteristics from a rotating spinning cylinder surface were experimentally investigated. The effects of rotational Reynolds number, jet-exit Reynolds number , the nozzle width-to-cylinder diameter ratio , and the ratio of the distance between nozzle exit and the front of cylinder to nozzle width on the mean were determined. The phenomena of the first and second critical point was analyzed and validated. On the basis of experimental data, the correlation equation was obtained.     

Melting of a vertical ice cylinder inside a rotating cylindrical cavity filled with binary aqueous solution

The melting of a vertical ice cylinder into a homogeneous calcium chloride aqueous solution inside a rotating cylindrical cavity with several rotating speeds is considered experimentally. The melting mass and temperature are measured on four initial conditions of the solution and four rotating speeds of the cavity. The temperature of the liquid layer becomes uniform by the mixing effect resulting from cavity rotation and it enhances the melting rate of the ice cylinder. As the cavity‐rotating speed increases, the melting rate increases. The dimensionless melting mass is related to the Fourier number and the rotating Reynolds number in each initial condition, therefore an experimental equation that is able to quantitatively calculate the dimensionless melting mass is presented. It is seen that the melting Nusselt numbers increase again in the middle of the melting process. The ice cylinder continues to melt in spite of the small temperature difference between the ice cylinder and the solution. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(6): 359–373, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20211     

双平行平面射流输运特性研究

平行射流输运特性研究具有较重要的理论意义和工程价值,对水平浓淡煤粉燃烧也有较重要的意义。本文实验研究了双平行平面射流动量、能量和质量输运,结果表明：速度分布表现为双射流相互吸引并最终汇合成单一射流;温度分布反映了冷射流为加热射流所卷吸;浓度分布反映了惯性力的占优作用。三种变量分布反映了动量、能量和质量输运性质的根本性区别。