FSC赛车尾翼攻角对弯道性能影响的研究

以FSC方程式赛车模型为研究对象,利用虚拟风洞实验(VWT)探讨不同尾翼攻角对整车气动性能的影响,得到赛车气动升力特性。考虑了轮胎的非线性,从赛车转弯时轮荷变化入手,研究赛车不同尾翼攻角对应的轮胎侧向力分配及最大侧向加速度。研究结果表明,在一定范围内增大尾翼攻角可获得较大的侧向加速度,且可以降低赛车过弯侧翻的风险。尾翼攻角增加到20°附近后,由于尾翼失速会造成下压力损失,继续增大攻角反而不利于获得较大侧向加速度。最后,研究了赛车在不同尾翼攻角下的稳态转向特性,结果表明,适当增大尾翼攻角可以削弱赛车过多转向特性的趋势。     

目标驱动方法在赛车尾翼攻角优选上的应用

为了找到一种快速获得赛车尾翼在不同工况下最佳攻角的方法,以中国大学生方程式赛车某高校两片式尾翼为研究对象,根据计算流体力学方法,首先利用传统方法选定不同攻角,并使用Fluent进行模拟获得最佳值,然后,在Workbench平台上,对攻角进行参数化,并利用目标驱动优化方法通过数值模拟获得最佳攻角。研究表明,利用参数化优化的方法更加快速有效。     

基于特定赛道的方程式赛车转向梯形优化与虚拟试验

以对某方程式赛车的转向梯形传动机构进行优化为目的,基于转向梯形的运动学特性,及对赛车在特定赛道上比赛时传感器所采集的方向盘转角数据的分析,通过引入加权因子建立了以理想Ackerman几何关系为目标函数的优化模型,利用非线性最小二乘法进行了优化。并通过机械系统仿真软件ADAMS建立了赛车的虚拟样机整车模型,在通过试验验证其准确度的基础上,对优化前后的赛车的操纵特性进行了对比。虚拟试验结果表明,优化后的赛车不足转向特性略有加大,同时转向时前轮距变化幅度变小,转向时外侧车轮更加垂直于地面从而可以提供更大的侧向力,并且轮胎跳动时的前束角变化幅度变小。为同类赛车的转向梯形设计提供了借鉴。     

FSAE赛车新型定风翼型气动性能的提升

赛车的空气动力学特性决定着赛车的设计优劣和性能,其中气动阻力系数和气动负升力系数是决定气动特性的两个关键系数。采用数值模拟方法对赛车的空气动力性能有重要影响的后定风翼进行了翼型、攻角、离地间隙等结构参数下的气动分析和对比,根据阻力系数和负升力系数的变化规律以及匹配原则,确定了最佳的定风翼方案。结果表明:曲率较大、翼身较厚的翼型会产生较大的升力,攻角45°为最佳攻角方案,离地间隙的最佳值为88 mm。     

基于ADAMS的方程式赛车前悬架分析与优化

针对某型大学生方程式赛车前悬架系统进行分析与优化。利用动力学软件ADAMS/CAR建立该赛车前悬架多柔体模型,并在弹性运动学模式下进行仿真。分析了双轮平行跳动时悬架运动特性和赛车制动时的转向轻便性与抗点头性,结果显示主销内倾角、车轮外倾角、转向盘力矩与磨胎半径变化规律不符合设计要求。运用ADAMS/INSIGHT对原系统进行多目标优化,最终各参数均得到优化,改善了悬架系统的运动学特性与赛车的转向轻便性。     

基于CFD的FSAE赛车尾翼设计及优化研究

针对FSAE赛车尾翼的设计,采用CFD数值分析的方法,对FSAE赛车的尾翼翼型、尾翼翼缝、尾翼端板形状和翼片数量与尾翼气动性能之间的关系进行了研究。对尾翼气动性能具有重要影响的翼型在不同弯度和不同弯度位置条件下进行了气动分析和对比,发现了翼型弯度和厚度对于其阻力和负升力的影响,确定了合适FSAE赛车尾翼的翼型;同时对尾翼的翼缝、端板形状和翼片数量等关键参数进行了研究,根据其压力云图、流线图的变化规律和匹配原则,确定了最佳方案。研究结果表明:尾翼的翼型弯度及最大弯度位置、尾翼翼缝、尾翼端板形状和翼片数量对于尾翼的气动性能具有重要影响。     

赛车空气动力学套件设计与气动特性研究

FSAE赛车的空气动力学特性对其动力性、燃油经济性、操纵稳定性及制动性有重要影响.文中依据大赛规则设计了FSAE赛车空气动力学套件,基于CFD方法对比分析了3种不同参数的尾翼组合方案的气动特性,确定了最优的尾翼组合方案,根据最优方案的尾翼参数对前翼的参数进行了匹配;研究了有、无空气动力学套件的赛车的空气动力学特性,安装空气动力学套件后,赛车的气动升力系数由0.28下降到-1.19,气动阻力系数由0.44变为0.68,下压力显著增加;基于MATLAB对有、无空气动力学套件的赛车在特征赛道上的性能进行了计算,结果表明:赛车加装空气动力学套件后有效提高了过弯速度,推迟了刹车点,提高了圈速,有效提高了赛车的操纵稳定性和动力性.     

大学生方程式赛车多连杆悬架设计及优化

针对某赛车参赛过程中出现的转向回正力过大,过度转向趋势以及抗制动点头造成球铰间隙过大等问题,论文首先采用"二次瞬轴法"设计多连杆悬架虚拟主销,应用多体动力学仿真软件ADAMS/Car模块建立前悬架与转向系统虚拟样机;之后对主销后倾角、车轮外倾角、前束角及抗制动纵倾性四个参数仿真并应用ADAMS/Insight模块进行多目标优化设计;优化后的多连杆悬架能够提供合适的回正力矩,赛车具有轻微的不足转向趋势,同时赛车抗制动点头现象也得到明显改善。为大学生方程式赛车中的多连杆悬架设计和优化提供了参考。     

基于FLUENT的导弹气动特性仿真分析

针对国外新型轻质超音速导弹欧洲燕,进行导弹三维实体模型构建,开展其黏性定常绕流特性数值仿真计算.基本模型仿真结果表明:末端飞行马赫数1.5时,导弹升力系数在20°攻角以前呈线性变化关系,至25°攻角仍未出现失速迹象,相应沿升力方向过载系数27.33,机动能力强;导弹升阻比在攻角15°时达到最大值,为1.68;导弹气动压心在0°攻角时靠近尾翼,静稳定度最大,导弹周围流谱清晰.研究可为掌握该新型导弹的气动飞行性能提供基础和参考.     

基于虚拟样机的赛车操纵稳定性分析

基于虚拟样机技术对FSAE赛车进行操纵稳定性仿真优化是缩短赛车开发周期、提升赛车操纵稳定性的重要方法。基于ADAMS/Car建立FSAE赛车各系统模块,并装配成符合要求的整车虚拟样机,在前后悬架运动仿真分析的基础上,以前悬架硬点坐标为设计变量,以前轮定位参数和侧倾中心高度为优化目标进行多目标优化设计。为了对优化后的虚拟样机进行验证和整车操纵稳定性评价,分别选取75 m直线加速和整车稳态回转试验进行仿真,分析发现,直线加速仿真时间与实车试验数据偏差较小,侧倾角增益为0.65 (°)/g,转向半径比大于1,整车稳态响应特性良好。     

Numerical investigation on aerodynamic performance of a 2-D inclined hovering wing in asymmetric strokes

A numerical study on the effects of the asymmetry in flapping motions on the aerodynamic performance of a 2-D inclined hovering wing is carried out through the solution of the two-dimensional unsteady Navier-Stokes equations. Asymmetric flapping motions with different flapping durations as well as different angles of attack during downstroke and upstroke are considered, correspondingly the aerodynamic forces, the energy consumption and the flow structures of the wing are examined for the purpose. The results show that the asymmetry either in flapping duration or in angle of attack can effectively alter the aerodynamic characteristics of the wing. It is found that much larger vertical force is generated in the downstroke with smaller duration. As for the angle of attack, an increase in the angle during the downstroke gives rise to a larger vertical force and lifting efficiency while for the upstroke the increase in the angle results in a larger thrust force. Furthermore, a combined model with asymmetry in both flapping duration and angles of attack is also studied and the results show that a combined flapping motion with a faster downstroke and a higher downstroke angle of attack can produce much larger vertical force than a motion with asymmetry simply in stroke duration or angle of attack. The present results provide physical insight into a better understanding of the asymmetric stroke mechanisms in the flapping motion of insects.     

Investigation of wind tunnel wall effect and wing-fuselage interference regarding the prediction of wing aerodynamics and its influence on the horizontal tail

The calculation of aerodynamic characteristics of a wing is the basic problem for aerodynamic design of aircraft. Wing aerodynamics can be determined experimentally and numerically. The method of fixing the wing in the test chamber of wind tunnel is related to disturbance of flow through the wing. When the wing is entirely fixed in the test chamber, the disturbance is usually caused by the sting connecting the wing to the test chamber. The experiments in this paper fixed the wing by clamping to the wind tunnel wall at the wing symmetry surface (root section). With this wing fixation, it was possible to take advantage of the wingspan twice, but to obtain the 3D wing experiment results, it was necessary to evaluate the impact of the wind tunnel wall effect. As for aircrafts, the aerodynamic force of the aircraft’s wing will have certain difference than that of the wing alone. The intersection region between the wind tunnel wall and wing root (for the experiment), as well as between the fuselage and wing root have complex interactions of boundary layers, in particular separation phenomena in the boundary layers. By solving the differential equation for viscous flows, it was possible to visualize the picture of streamlines and flow separations in this interference region and the aerodynamic characteristics of the wing. The singularity method was also used to compare results within its application range. The aerodynamic coefficients in the two cases with and without interference were analyzed. Complex interactions in the interference region could alter the predicted aerodynamic force calculated for the wing alone, which should be estimated. Very strong separations in the wing-fuselage interference region at large angles of attack turned into vortices at the rear impacting on the horizontal tail aerodynamics that is related to the balance problem of the aircraft.

     

小型通用飞机翼根气动性能及流动机理研究

小型通用飞机通常需要采用相对简单的增升系统及自身良好的气动性能以满足起飞和着陆阶段的安全和效益的匹配要求,这些与大迎角空气动力学特性有关。而控制翼身结合部的流动分离, 对改善小型飞机的大迎角性能具有重要的工程应用价值。通过数值模拟的方法,对某一典型通用飞机外形的着陆构型的气动性能及翼根处的流动机理研究得出,翼根处产生的马蹄涡及边角涡以及根部前缘吸力峰增高是导致翼根气流分离的主要原因,由此可通过前缘整流、展向整流和中后段三方面进行相关的整流方案设计。     

Numerical investigation into the effects of stroke trajectory on the aerodynamic performance of insect hovering flight

Various stroke trajectories may be observed in insect hovering flight in nature; however their influences on the flight performance of insect are not well estimated. In this study, a numerical investigation into the effects of stroke trajectories on the aerodynamic performance of insect hovering flight is carried out through the solution of the two-dimensional unsteady incompressible Navier-Stokes equations. An insect wing model with ellipse cross section in hovering flight is considered for the purpose and four types of idealized trajectories (Named linear, oval, figure-eight and double-eight) which possess different deviation characteristics from the stroke plane are examined. The influences of the deviation amplitude of trajectory, the attack angle of wing and the inclined angle of stroke plane on the aerodynamic characteristics of hovering wing are systematically analyzed. The results show that in the case of the wing in a normal hovering flight where the stroke plane is horizontal, the trajectory deviation from the stroke plane weakens the aerodynamic performance for each trajectory case considered, and this deteriorative effect becomes more serious as the amplitude of deviation increases. With regard to the influence of the angle of attack, the results show that the time-averaged drag force and power consumption increase monotonically with the angle, whereas the time-averaged lift force and the lifting efficiency increase first and then decrease as the angle increases further. In the case of a hovering flight with an inclined stroke plane, distinctly different trends from a normal hovering flight are obtained.     

Vortical flows over a delta wing at high angles of attack

The vortex flow characteristics of a sharp-edged delta wing at high angles of attack were studied using a computational technique. Three dimensional, compressible Reynolds-averaged Navier-Stokes equations were solved to understand the effects of the angle of yaw, angle of attack, and free stream velocity on the development and interaction of vortices and the relationship between suction pressure distributions and vortex flow characteristics. The present computations gave qualitatively reasonable predictions of vortical flows over a delta wing, compared with past wind tunnel measurements. With an increase in the angle of yaw, the symmetry of the pair of leading edge vortices was broken and the vortex strength was decreased on both windward and leeward sides. An increase in the free stream velocity resulted in stronger leading edge vortices with an outboard movement.     

基于ANSYS的小型赛车车架的有限元分析

车架是FSAE赛车的重要组成部分,车架的好坏直接影响着赛车的性能,车架的强度和刚度是贯穿整个车架设计和制造的重点.文中旨在设计一个既符合规则,又具有轻量化、高性能的车架.首先在三维软件CATIA中建立车架的模型,然后导入到有限元分析软件ANSYS中进行受力分析,最后对车架进行了模态分析,得出了车架的6阶模态,并得到了相应的振型和频率.将分析所得数据与已知数据进行对比,证明该方案满足设计要求,为FSAE赛车的安全参赛提供理论保证.     

基于轮胎侧偏特性的汽车自适应前照灯转角修正方法及跟随效果研究

由于汽车前照灯转角和汽车的运动状态有关,而汽车的运动状态又受轮胎侧偏特性的影响,因此本文利用前后轮侧偏角的绝对值之差来修正前照灯理论转角;然后,在Simulink中建立步进电机仿真模型,在ADAMS中建立前照灯减速机构虚拟样机模型,再通过两者组合成前照灯转角开环控制系统.把前照灯理论转角输给该开环控制系统,通过MATLAB/Simulink和ADAMS的之间的软件通信接口,实现了2个软件的联合仿真,得出了前照灯的实际输出转角对需求理论转角的跟随曲线.     

飞行汽车概念设计与气动特性分析

利用CFD软件Fluent,根据Spalart-Allmaras模型建立了飞行汽车外流场的三维湍流流动模型.通过数值模拟,得到飞行汽车在不同攻角下的升阻力系数变化规律.研究结果表明,在所选攻角范围内,随着攻角的增大,飞行汽车的升阻力系数不断增大,当攻角达到14＆#176;左右时,飞行汽车由于气流分离而发生失速.Fluent为飞行汽车的气动特性分析提供了重要依据.     

FSAE赛车前轮定位参数的优化研究

针对大学生方程式(FSAE)赛车前轮定位参数的优化设计问题,基于ADAMS/Car模块建立FSAE赛车双横臂独立悬架的仿真模型,对前轮定位参数进行仿真分析。利用ADAMS/Insight模块进行优化设计,确定设计参变量和设计目标,对所选定的设计目标进行影响因素分析;根据优化结果修改前悬架仿真模型,再次进行前轮定位参数的仿真分析。结果表明:赛车车轮上下跳动时,优化后的前轮定位参数能够在合理的范围内变化,满足赛车悬架设计要求,赛车悬架的主要性能得到明显提高。     

对旋式轴流风机全角度整机数值模拟及试验验证

通过对对旋式轴流风机采用不同的湍流模型进行多角度和多工况点整机数值模拟,并对比试制样机试验数据,探索湍流模型的规律性,为对旋式轴流风机全角度整机数值模拟下湍流模型的合理选择,提供了一定的依据;通过全角度整机数值模拟,有效地验证了全角度下风机的气动性能特性和设计工况点的合理性,并对I、II级叶轮叶片安装角进行正交数值模拟试验,筛选出I、II级叶轮叶片最佳匹配角度,通过进一步分析最佳匹配角度的气动性能,探索了两级叶轮功率最佳匹配关系。