共查询到20条相似文献,搜索用时 93 毫秒
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S. O. Kang S. O. Jun H. I. Park K. S. Song J. D. Kee K. H. Kim D. H. Lee 《International Journal of Automotive Technology》2012,13(4):583-592
This research aims to develop an actively translating rear diffuser device to reduce the aerodynamic drag experienced by passenger cars. One of the features of the device is that it is ordinarily hidden under the rear bumper but slips out backward only under high-speed driving conditions. In this study, a movable arc-shaped semi-diffuser device, round in form, is designed to maintain the streamlined automobile??s rear underbody configuration. The device is installed in the rear bumper section of a passenger car. Seven types of rear diffuser devices whose positions and protrusive lengths and widths are different (with the basic shape being identical) were installed, and Computational Fluid Dynamics (CFD) analyses were performed under moving ground and rotating wheel conditions. The main purpose of this study is to explain the aerodynamic drag reduction mechanism of a passenger car cruising at high speed via an actively translating rear diffuser device. The base pressure of the passenger car is increased by deploying the rear diffuser device, which then prevents the low-pressure air coming through the underbody from directly soaring up to the rear surface of the trunk. At the same time, the device generates a diffusing process that lowers the velocity but raises the pressure of the underbody flow, bringing about aerodynamic drag reduction. Finally, the automobile??s aerodynamic drag is reduced by an average of more than 4%, which helps to improve the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. 相似文献
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汽车日益严苛的排放、油耗法规对准确测量和降低道路行驶阻力提出了更高的要求,气动阻力是汽车道路行驶过程中主要的阻力来源,真实道路自然风来流偏角是影响汽车气动阻力的重要因素。提出了一种基于真实道路来流偏角分布的风平均阻力系数计算方法——偏航角密度法,并和其他风平均阻力系数计算方法进行了比较,利用风洞法测量道路行驶阻力,研究了来流偏角对汽车道路行驶阻力、循环能耗的影响。研究表明,来流偏角概率密度呈现明显的区域分布特征,来流偏角显著影响汽车实际道路气动阻力、循环能耗,根据偏航角密度法,考虑真实道路来流偏角时,气动阻力、循环能耗分别最大可增加3.0%、1.6%。 相似文献
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S.Y. Bhave 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1992,21(1):225-245
Airsprings have been used for vehicle suspensions over the last 40 years. They are mostly used as independent suspensions. Analysis of air springs available in literature is mostly limited to a single-degree-of-freedom system or a two-degrees-of-freedom system only in the translation mode. This paper deals with a model of a vehicle where the front and the rear springs are connected by a capillary tube. A two-degrees-of-freedom model having motion in bounce and pitch mode is presented. Equations of mass flow are linearized on the assumption of small variations in volume and pressure. Expressions for the transmissibility and the phase angle in the bounce and the pitch mode are derived. Road inputs to the front and the rear axles are assumed to be identical except for a phase difference between them. The effect of the capillary flow coefficient and that of the phase angle between the front and the rear axle excitation are studied. It is shown that an optimum value of the capillary flow coefficient exists which minimizes the transmissibility of motion in both modes over the entire frequency range. It is also observed that a phase angle of 180 degrees presents ideal transmissibility characteristics. Thus, a promising application of air springs for a vehicle suspension is presented. 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(1):225-245
SUMMARY Airsprings have been used for vehicle suspensions over the last 40 years. They are mostly used as independent suspensions. Analysis of air springs available in literature is mostly limited to a single-degree-of-freedom system or a two-degrees-of-freedom system only in the translation mode. This paper deals with a model of a vehicle where the front and the rear springs are connected by a capillary tube. A two-degrees-of-freedom model having motion in bounce and pitch mode is presented. Equations of mass flow are linearized on the assumption of small variations in volume and pressure. Expressions for the transmissibility and the phase angle in the bounce and the pitch mode are derived. Road inputs to the front and the rear axles are assumed to be identical except for a phase difference between them. The effect of the capillary flow coefficient and that of the phase angle between the front and the rear axle excitation are studied. It is shown that an optimum value of the capillary flow coefficient exists which minimizes the transmissibility of motion in both modes over the entire frequency range. It is also observed that a phase angle of 180 degrees presents ideal transmissibility characteristics. Thus, a promising application of air springs for a vehicle suspension is presented. 相似文献
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K. S. Song S. O. Kang S. O. Jun H. I. Park J. D. Kee K. H. Kim D. H. Lee 《International Journal of Automotive Technology》2012,13(6):905-914
This study proposes an aerodynamically optimized outer shape of a sedan by using an Artificial Neural Network (ANN), which focused on modifying the rear body shapes of the sedan. To determine the optimization variables, the unsteady flow field around the sedan driving at very fast speeds was analyzed by CFD simulation, and fluctuations of the drag coefficient (C D ) and pressure around the car were calculated. After consideration of the baseline result of CFD, 6 local parts from the end of the sedan were chosen as the design variables for optimization. Moreover, an ANN approximation model was established with 64 experimental points generated by the D-optimal methodology. As a result, an aerodynamically optimized shape for the rear end of the sedan in which the aerodynamic performance is improved by about 5.64% when compared to the baseline vehicle is proposed. Finally, it is expected that within the accepted range of shape modifications for a rear body, the aerodynamic performance of a sedan can be enhanced so that the fuel efficiency of the sedan can be improved. The YF SONATA, a sedan manufactured by Hyundai Motors Corporate, played a major role in this research as the baseline vehicle. 相似文献
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镂空式车顶扰流板已成为一种汽车造型设计的新思路,对整车空气动力性能也有极大的影响。为了研究镂空式车顶扰流板对整车空气阻力系数的影响,基于比亚迪某款带有镂空式车顶扰流板的两厢车型,以 CFD仿真为主要开发工具,分别研究了扰流板角度、镂空通道和 D 柱扰流板的影响,并与风洞试验结果进行对标。研究发现,镂空式车顶扰流板的角度减小,镂空通道与后风挡距离减小,以及 D 柱扰流板延伸长度增大均会导致顶部尾流增大,使尾流上下匹配关系发生变化。当上下尾流匹配性更好时,空气阻力系数更低。该研究结果可为后续镂空式车顶扰流板的开发提供经验。 相似文献
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利用CFD方法对某款车型进行外流场分析,分析其气动特性,计算出该车的阻力系数和升力系数,并通过对不同的底部上翘角模型进行分析,得出满足要求的底部上翘角,为其改进设计提供理论参考。 相似文献
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A. Buljac I. Džijan I. Korade S. Krizmanić H. Kozmar 《International Journal of Automotive Technology》2016,17(3):377-385
Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k-ε turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height. 相似文献
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Ljubomir Majdandžić Dalibor Buljić Andrija Buljac Hrvoje Kozmar 《International Journal of Automotive Technology》2018,19(6):949-957
Solar road vehicles have very specific design requirements. This makes their aerodynamic characteristics quite different from classic sedan vehicles. In the present study, the computational model of a typical solar road vehicle was developed to investigate its aerodynamic forces and flow characteristics. Computations were performed assuming the steady viscous flow and using the Reynolds-averaged Navier Stokes equations along with the k-ω turbulence model. The obtained results indicate some important findings that are commonly not present for classic sedan vehicles. In particular, a contribution of the viscous drag force to the overall drag force is considerably larger (41 %) than it is the case for the standard passenger road vehicles, where the form drag force dominates over the viscous drag force. Surface pressure distribution patterns indicate a favorable aerodynamic design of this vehicle. In particular, larger pressure coefficients on the top of the vehicle body as compared to the bottom surface contribute to increasing a downforce and thus the vehicle traction. The airfoil-shaped crosssection of the designed cockpit canopy has favorable properties with respect to reduction of the aerodynamic drag force. 相似文献
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Sung Jun Ha Ung Chun Jong Yun Park Moon Sang Kim 《International Journal of Automotive Technology》2017,18(5):779-784
High pressure acting on the vehicle’s body plays an important role in deciding the aerodynamic drag. An idea has been suggested to enhance the aerodynamic performance for small passenger car by relieving the high pressure in the engine room. The high pressure inside the engine room can be released to the outside of the vehicle through a hole perforated on the wheel house liner. About 1 % of the drag coefficient can be improved with the 1.88 % of the radiator air mass flow rate increment by installing the top hole with slots on the wheel house liner. Flow simulations are performed at the driving velocity of 110 km/h with the moving wall condition of the same velocity. The tire is rotating to catch more precise flow physics around a tire and wheelhouse liner. 相似文献
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准确获得车-桥系统气动力是评估强风作用下桥上车辆运行安全性和舒适性的基本前提,为此必须考虑车辆与桥梁间存在的显著气动相互干扰。以山区大跨桥梁常见的π型断面主梁和集装箱货车为研究对象,设计并制作了1:32几何缩尺比的桥梁和车辆刚性测压模型,通过风洞试验测试了典型车-桥组合工况下车辆表面的风压分布,分析了前、后车辆干扰作用、车辆横向距离和车道组合方式等对桥上汽车气动特性的影响,并进一步分析汽车表面的风压值分布,以探究汽车气动力系数变化的机理。研究结果表明:前、后车辆间的干扰、车辆横向距离的改变对汽车的侧向力系数、阻力系数和升力系数均有较大影响,但对汽车的力矩系数影响较小,且汽车的力矩系数具有一定的离散性;车道组合方式中测试车辆位置的改变对汽车气动特性的影响大于干扰车辆位置的改变对汽车气动特性的影响,且车辆组合方式的改变对汽车的力矩系数基本没有影响;受桥梁π型主梁断面的影响,汽车侧向力系数的变化趋势与Coleman规律下的变化趋势不同。 相似文献
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为了研究局部开孔或开槽等措施对减小交通标志板风荷载的影响效果,设计了可以实现多种开孔开槽方式的标志板试验模型。通过刚性模型测压风洞试验,得到16种不同开孔、开槽方式下的非均匀开孔板表面风压数据,获得不同工况下板表面的平均风压分布特性,分析单排孔位置、单列孔位置、多排多列孔位置及单槽双槽等因素对交通标志板表面平均风压分布、阻力系数和扭矩系数的影响规律,进一步分析各工况下板平均阻力系数随孔隙率的变化规律,以及扭矩系数随风向角的变化规律。研究结果表明:风向角为0°~45°时,板的阻力系数变化很小,风向角为45°~90°时,板的阻力系数呈线性减小;0°风向角下,开孔或开槽板迎风面风压系数基本不变,背风面孔或槽附近平均风压系数幅值增大;当孔隙率小于5%时,板阻力系数对孔隙率、孔位置和开槽数量均不敏感,标志板风荷载减少的主要原因在于受风净面积的减少;孔隙率较大时,减小板阻力系数的效果相对明显;给出了非均匀开孔情况下,板阻力系数与孔隙率的建议公式;板在45°斜风向下产生最大扭矩系数,开孔或开槽都能够显著减小斜风向下绕板竖向中心轴和边缘竖轴的平均扭矩系数,其中45°风向角时影响更为显著;孔隙率较大时,扭矩系数减小效应更为显著。 相似文献
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Being a continuous subject of research, this study presents new aspects regarding the relevance of underbody diffusers in road vehicle aerodynamics. Using a generic car model on wheels as a reference, the effect of the wheels on the body fitted with an underbody diffuser was studied, where the diffuser length and angle were varied within ranges which are applicable for hatchback passenger cars. The results show that the vortices which originate from the rear wheelhouses have a major impact on the aerodynamics of the underbody diffuser, which results in increasing of drag and lift of the body. For cases studied, the average drag and lift increment due to the addition of wheels were (ΔcD)mean = 0.058, respectively (ΔcL)mean = 0.243. The lift of the body on wheels decreases with both diffuser length and diffuser angle, and there are situations when it may become negative as for a body without wheels. The results show also the possibility to reach a minimum drag according with normalised diffuser length. 相似文献