变工况下车辆燃油箱多孔挡板抑浪机理研究

车辆的变加速度工况会导致燃油剧烈晃动,发生供给中断甚至损坏燃油箱结构等现象。采用基于动网格耦合VOF的数值模拟方法和构建的水平激励试验平台,从数值与试验两个方面来分析燃油晃动过程。以某重载商用车辆燃油箱内多孔挡板为例,系统分析该挡板抑制燃油晃动的效果,探讨了多孔挡板抑浪的机理。研究结果表明：多孔挡板能够显著减小壁面压力、自由液面高度及液面轮廓起伏;燃油箱运动瞬间,挡板壁面出现瞬态局部高压,但对挡板结构的疲劳损坏程度较低;多孔挡板的孔隙将未被挡板实体部分阻碍的小部分流体分割成多股射流,急剧减缓行进波传递;多孔挡板附近流场产生涡旋,涡旋聚集和耗散能量,降低流体运动速度,达到抑制燃油剧烈晃动的目的。     

飞机发动机驱动泵出口管路振动分析与优化

为了研究飞机发动机驱动泵出口流体压力脉动对管路结构振动的影响,基于某型飞机发动机驱动泵真实结构参数,建立了AMESim柱塞泵模型,模拟了柱塞泵额定工作状态下液压油出口流动特性,得到流体压力脉动函数表达式。选取液压泵出口段管路结构进行建模分析,将流体脉动函数表达式作为管路入口流体边界条件输入,对管路进行流固耦合振动特性分析。结果表明:管路的过渡段在流体冲击下产生的变形最大,变形量为1.1774 mm;当流体激励频率接近管路一阶固有频率时,管路发生共振的振幅最大,其中最大振幅为31.227 mm。最后,通过加设弹性卡箍的方法对管路进行优化,优化方法有效降低了流体激励对管路振动的影响。     

考虑压力脉动的消防水炮自适应炮头射流系统参数振动研究

消防水炮自适应炮头可根据流体压力和流量变化自动调整炮口开度,从而显著提升其射流性能。考虑自适应炮头射流系统中流体的压力脉动,结合流体体积弹性模量与刚度间的关系,建立基于时变流体刚度的射流系统参数振动动力学模型,采用多尺度法推导脉动激励频率接近射流系统固有频率和固有频率与脉动频率的组合频率时的共振响应公式,分析射流系统的主共振和组合共振响应。结果表明射流系统发生主共振响应时,激励频率占主导成分,且接近一阶固有频率时系统共振幅值最大;射流系统发生组合共振响应时,激励频率与流体刚度波动频率的组合频率对系统响应的影响与流体脉动频率有关;主共振和组合共振将恶化系统的动力学行为。本项研究可为深入探索自适应炮头射流系统的动力学特性,优化不同工况环境下的设计参数提供理论依据。     

轴承座受冲击条件下转子系统碰摩动力学行为研究

针对基础受冲击激励的一转子-轴承系统,在线性和非线性范围内分别建立了其动力学模型和相应的微分方程组,其中考虑了碰摩的因素。运用数值计算的方法进行动力学响应求解,得到了时间历程响应。对响应结果进行分析后表明,碰摩对冲击响应的影响是有益的,表现在转子瞬态振动最大振幅减小,转子振动能量衰减加快;对冲击碰摩动力学模型进行线性化近似处理是不合适的;冲击不会改变稳定碰摩运动形式;冲击激励持续时间对响应的影响十分明显,且当冲击激励频率接近或等于转子固有频率和涡动频率时响应较大。     

考虑构件偏心时磁场调制型磁齿轮传动系统的主共振

考虑磁场调制型磁齿轮传动系统中内转子偏心,建立了基于时变磁耦合刚度的参数振动动力学模型,采用多尺度法推导了内转子上转矩激励频率接近系统固有频率时的共振响应计算公式,分析了算例系统的主共振响应。结果表明:当转矩波动频率接近系统不同阶固有频率时,产生的共振振幅相差较大,且共振响应中只有一个自由度的振幅很大,而其他自由度振幅很小;系统响应中激励频率占主导成分,而激励频率与磁耦合刚度波动频率的组合频率对系统响应影响很小。较大的主共振会严重恶化系统动力学行为,对其进行研究可以为深入探索该系统的动力学特性、优化不同工况环境下的设计参数提供理论依据。     

自激振荡脉冲射流频率特性实验研究

为了研究射流峰值压力频率和脉冲射流峰值压力以及自激振荡装置结构参数间的相互关系,运用流体网络理论建立了自激振荡装置相似网络模型,并完成了单腔室自激振荡脉冲实验。相似网络模型和实验结果表明:脉冲压力峰值频率不仅取决于系统的固有频率,还决定于系统的阻尼比;射流压力峰值频率随腔长的增大而减小,随泵压的升高而增大,存在一个最佳腔长使射流峰值压力最大;自激振荡装置具有低波滤通性,当来流脉动主频与自激振荡装置固有频率相近时,脉冲射流压力峰值最大。     

基于Stribeck模型的自激系统分岔混沌特性研究

为了能够深入研究摩擦自激振动系统的振动-摩擦耦合动力学特性,建立基于Stribeck摩擦模型的质体 弹簧-带摩擦自激振动系统非线性动力学模型,利用数值仿真,研究自激振动系统在不同系统阻尼系数条件下,不同外部激励振幅和激励频率分别对自激振动系统分岔与混沌特性的影响。结果表明,当激励频率不变,无量纲激励振幅在0～1.5区间,系统持续准周期运动的时间随阻尼系数的增加而逐渐增长。振幅在10～11区间阻尼系数相对较小时,系统除倍周期分岔外还存在Hopf分岔;在阻尼系数相对较大时,系统为倍周期分岔。激励振幅不变,激励频率接近于派生系统固有频率时,为单周期同步振动;激励频率向大于派生系统固有频率方向变化时,为准周期运动;激励频率向小于派生系统固有频率方向变化时,为混沌运动。     

基于有限元的液罐车罐体结构分析

为了研究某消毒液罐车在制动情况下罐体中液体晃动对罐体结构的影响,利用有限元软件对液罐车在不同液面高度及不同加速度情况下进行流固耦合分析,通过Fluent流体仿真,并将仿真得到的流体对罐体内壁的压力导入静态结构分析中,得出消毒液罐车的结构性能.根据仿真分析结果可知,车身和防浪板应力都较小,最大应力位于受冲击一侧的挡板上.     

钢绳联轴器频率-振型的数值模拟

为了得到柔性联轴器系统的固有频率和振型,借助Workbench线性模态分析模块,对钢绳联轴器系统两种运动极限状态下的系统固有频率和主振型进行数值计算,巧妙利用接触刚度K与接触面积的关系,得出非线性钢绳联轴器系统的模态参数;模拟加载特性进行谐响应分析,得到敏感响应面在激励状态下对应的频率-振幅曲线,找出各峰值对应的频率。     

冲锤处流体阻力对高能射流式液动锤性能影响

应用计算流体动力学(computational fluid dynamics,简称CFD)动态分析技术,对SC-86H型高能射流式液动锤试验样机流场特性进行了研究,计算得出了相关性能参数,并通过实验装置对液动锤不同输入流量下的冲击频率进行了测试。将液动锤冲击频率的模拟计算结果与实测结果进行了对比,结果表明:若不考虑冲锤处流体阻力的影响,液动锤冲击频率计算值与实测值相比明显偏大,最小相对误差达18.9%;而将冲锤处流体阻力的作用考虑在内,冲击频率的计算值与实测值比较接近,最大相对误差为8.0%,大幅提高了数值计算结果与实测值之间的吻合程度。这说明冲锤高速运动产生的轴向流体阻力不容忽略,设法减小冲锤处流体阻力的大小,有望成为提高高能射流式液动锤冲击功和能量利用率的重要途径。     

Reduction of sloshing effects in a rectangular tank through an air-trapping mechanism – a numerical study

A 2D rectangular tank subjected to horizontal excitations is used to analyze the effects of sloshing. The tank is fitted with horizontal baffles on two sides to suppress the impact pressure of sloshing by using an air-trapping mechanism. The volume of fluid method is adopted to create sloshing phenomena. Five cases with fixed baffle gaps and various baffle lengths are used to analyze the effects of suppressing the sloshing impact pressure in the tank. The peak pressure values of the cases with baffles are compared with those of the cases without baffles. Results show that the maximum suppression rate achieved is 63.6 % due to air trapping and baffle effects. Baffle ratio (Defined by G/L), a geometrical dimensionless factor, is considered to analyze the effects of baffle length and gap. A baffle ratio of 0.5 results in a 14.2 % reduction in the sloshing impact rate. An increasing amount of air is trapped within the baffle array as BR decreases.     

防波板对罐车在制动时的安全稳定性的影响

充液罐车在制动时,液体晃动对罐车的安全稳定性影响很大。对罐体进行全尺寸建模模拟,通过与试验结果的对比验证了计算方法的可靠性,并且对比研究了罐车在带有防波板和未带防波板两种情况下,液体的晃动分析、罐车的压强和受力变化以及在不同加速度、充装率下防波板的作用。结果表明,防波板能够使晃动液体分流,减小了冲击力峰值,使压强分布得更加均匀,有效地降低液体的晃动程度。这对罐车的安全运行,尤其是装有化学试剂的罐车具有重要的参考价值。     

Optimization design technique for reduction of sloshing by evolutionary methods

The oscillation of a fluid caused by external force, called sloshing, occurs in moving vehicles containing liquid masses, such as trucks, railroad cars, aircraft, and liquid rockets. This sloshing effect could be a severe problem in vehicle stability and control. Therefore, development of efficient and easy method to reduce sloshing effect is positively necessary. In this study, optimization design technique for reduction of the sloshing using evolutionary method is suggested. Two evolutionary methods are employed, respectively, the artificial neural network (ANN) and genetic algorithm (GA). ANN is used for the analysis of sloshing and GA is adopted as optimization algorithm. The considered storage tank for fluid is a rectangular tank. The design variables are width and installation location of the baffle, and sloshing reduction coefficient by baffle is used as an object function in the optimization. As a result of this study, the optimal design for sloshing reduction is presented.     

Dynamic response characteristics of cylindrical baffled liquid storage tank to the baffle number

The goal of current study is to numerically investigate the dynamic response characteristics of cylindrical baffled liquid storage tank, which is subjected to a vertical acceleration at boosting, with respect to the number of baffles. Both the storage tank and baffles are modeled as flexible elastic structures, and the suppression of sloshing-induced dynamic responses by baffles are evaluated in terms of the hydrodynamic pressure, the dynamic displacement and stress. Through the numerical experiments, it has been observed that the introduction of baffles to the partially filled liquid tank remarkably decreases the maximum values of displacement and effective stress at both the bottom plate and baffles. And, the variation of displacement and effective stress is stabilized much faster when baffles are installed and the baffle number increases. Thus, it has been verified that the baffled liquid storage tank can be stably and safely applied to the liquid fuel storage tank for various transport vehicles.

     

Effect of baffles on orbital accelerations - Induced bubble oscillations in microgravity

The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations with partially-filled rotating fluids has been studied. Present study is applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffle. Results of slosh wave excitation along the liquid—vapor interface induced by jitter acceleration-dominated orbital accelerations provide a torsional moment with an up-and-down movement of bubble oscillations in the rotating dewar. The results show rightward and leftward movement of bubble oscillations transverse to the rotating axis, and up-and-down movement of bubble oscillations longitudinal to the rotating axis of dewar container. The orbital accelerations also induce an eccentric contour of bubble oscillations in a horizontal r—θ plane. As viscous force between liquid—solid interface, and surface tension force between liquid—vapor—solid interface can greatly contribute to the damping effect of slosh wave excitation, the rotating dewar with baffle provides more areas of liquid—solid and liquid—vapor—solid interfaces than that of a rotating dewar without baffle. Results show that the damping effect provide by a baffle reduce the amplitude of slosh wave excitation and reduce the degree of asymmetry in liquid—vapor distribution. Computation of bubble (helium vapor) mass center fluctuations also verifies that a rotating dewar with baffle produces less fluctuations than that of a rotating dewar without baffle.     

The vibration performance experiment of Tuned Liquid damper and Tuned Liquid Column damper

Tuned Liquid damper and Tuned Liquid Column are kind of passive mechanical damper which relies on the sloshing of liquid in a rigid tank for suppressing structural vibrations. TLD and TLCD are attributable to several potential advantages —low costs; easy to install in existing structures; effective even for small-amplitude vibrations. In this paper, the shaking table experiments were conducted to investigate the characteristics of water sloshing motion in TLD (rectangular, circular) and TLCD. The parameter obtained from the experiments were wave height, base shear force and energy dissipation. The shaking table experiments show that the liquid sloshing relies on amplitude of shaking table and frequency of tank. The TLCD was more effective control vibration than TLD.     

液罐车流-固耦合分析及优化设计

在液罐车转向的过程中,罐体内液体的晃动会对液罐车产生侧向冲击力和侧倾力矩。以非满载液罐体为研究对象,采用流体体积法(Volume of fluid,VOF)对转向工况下的液体晃动进行数值分析,获得了侧向加速度和充液比对液晃的影响规律。建立液罐车侧向动力学模型,仿真结果表明,充液比为50%~70%时液罐车侧翻阈值较小。对罐体内部结构进行优化设计,设计一种倒V型防波板装置来降低液体对罐壁冲击。研究了9种倒V型防波板在不同充液比时的减晃效果,结果表明,安装三块夹角为150°的V型防波板防晃效果最好。搭建缩比液罐车侧倾台架,利用电动液压缸举升整个钢板平面和滑台以模拟罐车侧倾状态,同时滑台带动罐体向反方向平移,实现质心位置纠正,从而减小液体侧向晃动力与侧倾力矩,提高了液罐车的侧向稳定性。     

Effect of the Inclination of Baffles on the Power Consumption and Fluid Flows in a Vessel Stirred by a Rushton Turbine

The role of baffles in mechanically stirred tanks is to promote the stability of power drawn by the impeller and to avoid the fluid swirling, thus enhancing mixing. The present paper numerically investigates the baffles effects in a vessel stirred by a Rushton turbine. The geometric factor of interest is the baffle inclination which is varying between 25°, 32.5°, 45°, 70° and 90° at different impeller rotational speeds. The impeller rotational direction has also been varied. The vortex size and power consumption were evaluated for each geometrical configuration. It was found that the best configuration is the baffle inclination by α = 70° at a negative angular velocity.     

泵源与机体共同激励下液压管路振动特性

车辆液压系统在工作过程中会受到车体振动与泵源液压脉动双重激励的影响,对压力波的传递及管网的振动产生重要影响。针对车辆液压系统泵源激励和车辆机体激励产生的振动进行分析,研究多源激励下管路的振动规律及压力波的传递规律。首先对泵源与机体共同激励下管路振动的计算方法进行了分析,将流体域动力学方程与固体域动力学方程进行组合,建立了流固耦合的总体动力学方程,然后对方程进行离散求解。基于理论推导,采用数值模拟的方法对液压管路的振动进行了分析,研究发现,液压系统在泵源谐波激励下的振动响应表现为宽频域的强迫振动,其谐波频率与泵源流体压力脉动频率保持一致,当泵源产生的压力脉动频率与液压管路的固有频率接近时,会激起管路结构大幅度共振响应。