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Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT12008200820082008HunanHunanHunanHunanUniversityUniversityUniversityUniversityFormulaFormulaFormulaFormulaSAESAESAESAEWestWestWestWestDesignDesignDesignDesignReportReportReportReport1. 1. 1.1.IntroductionIntroductionIntroductionIntroductionHNU Racing Team is a second year competitor in the Formula SAE West competition. After summing upthe experience of the 2007 competition, we made some guide lines of our design, in summary: Reliability:Reliability:Reliability:Reliability:After our discussion for the 2007 competition after finishing, we made the conclusion thatreliability was the most essential design component of HNU2008.Wewant to have a car that isengineered to last and to be reliable in all components. Simplicity:Simplicity:Simplicity:Simplicity:Get the car running on time with a simple and practical design easy to manufacture,orsimplypurchased. Keep it simple is the key. WWWWeighteighteighteightR R RReductioneductioneductioneduction: : :Compare with the cars of other teams, HNU2007 was too heavy. One of the mostimportant guide lines was reducing the weight as much as possible. According to the design, well reduceweight of HNU2008 by 80kg(176 lb). EaseEaseEaseEaseofofofofservicingservicingservicingservicingandandandandmaintenance:maintenance:maintenance:maintenance:when something was wrong with HNU2007, we couldnt repair iteasily and quickly as a result of design.Wepaid more attention in design to make HNU2008 easy formaintenance.In order to meet these requirements and manufacturing deadlines, we have relied extensively on the use ofcomputers. Several different design, simulation, optimization, and manufacture packages were used toenhance our design process as the table below.Design SectionDesignAnalysis /TestingSuspension and SteeringSystemModeling inUnigraphics,AutoCAD1. Dynamic Analysis inADAMS2. Designed in Matlab3. Simulated and optimize in Lotus Suspension AnalysisImpact attenuator1. Simulated in LS-DYNAFrame1. Use of PVC models for optimization.2. Chassis stiffness calculation & optimization inANSYS.Powertrain1. Injectors flow-tested to determine characteristics.2. Dynamometer mapping of ECU.3. MatLab employed for drivetrain optimization.Drivetrain1. Dynamic Analysis inADAMSAerodynamics1. Use of Fluent for testing & optimizationErgonomics1. Calculated in Excel2. Use of PVC models of the frame to validate drivers comfortand room.Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT22. 2. 2.2.DesignDesignDesignDesignReviewReviewReviewReview2.1BrakesBrakesBrakesBrakesSystemSystemSystemSystemThe braking system is great important for the vehicleperformance. Reliability, safety and brakingperformance were our first design tasks.Tomaximize the reliability and safety, we considered thefollowing factors:Individual hydraulic circuits for the front and the rear have individual reservoirs for each circuit.Asaresult two master cylinders were employed. The bore of the front master cylinderis7/10 inch, and the rearboreis7/8 inch. The balance bar transmits the force which was applied to the pedal and distributes it to thefront and rear master cylinders. Each reservoir was directly mounted onto the master cylinder andispackagedasa single assembly soasto reduce the possibility of leakageorother damage. Four discsare thesame dimension 220 mm (8.66 in). Front calipers are a dual piston floating caliper with 27 mm (1.06 in)diameter piston, rear calipers are a single piston floating caliper with 34 mm (1.34 in) diameter piston. Thepedal box and the bracket are designed and fabricated by students. The pedal boxisconstructed fromaluminum alloy. It cleverly angles the master cylinders to give it a short overall length. With abovemeasures, our brake systemisable to make a good performance on the track that the friction coefficientrange from 0.6 to 1.6, and the brake deceleration can reach to 1.6gasmaximum.2.2FrameFrameFrameFrameThe chassisisbased on space-frame concept and the usage of #20 (equals to 1020-Normalized) tubesensures enough torsion stiffness and bending rigidity. This was chosen over other chassis types suchasmonocoque chassis due toitsability to retain high efficiency without difficult design and muchmanufacturing processes.This year the main considerations in the design of the frame were the safety of the driver, ergonomics,packaging criteria and overall strength, which still considered the safetyasthe most important point. Theentire frameisdesigned just around the driver, giving himorher the right amount of space and thusreducing the length of the members and shaving off excess weight. By using CAD (Unigraphics) to findthe best compromise between driver CG and comfort suchasseating position, visibility, steering wheelangle etc.The total weight of the frame was optimized using tubes of lower thickness and OD in areas of low stresswhich still meetthe rule. Our goalisto reduce the frame weight from 45kg(99 lb) to 32kg(70.5 lb),which have achieved. This goal was met by the optimized member placement using results of FEAanalysis (ANSYS). Analysis of the frame was performed for several cases by loading at the frontsuspension points with dynamic loads. The frame was designed such that the forces generated atsuspension points, engine mounts and the drive train assemblies were effectively dissipated through thestructure, ensuring higher load carrying capacity. The torsion stiffness of the frame was effectivelyincreased by the use of cross members and a final figure of 2500Nm/deg was obtained through ANSYS.The Special fixtures were designed to minimize the effect of warpage of the frame during the welding.The front impact attenuator was simulated in LS-DYNA.Acrush zone made of aluminum honeycomb wasprovided and was designed to absorb 8000 joules of energy.Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT32.3BodyBodyBodyBodyThe main aimisto reduce the weight of thebody.Since racing on the track in competitionisat relativelylow speeds (60km/h speed on the average), the aerodynamics of the vehicleisnot so important.Thebodywork was therefore shaped to fit the frame and show the style of a racecar.The idea of the body stylewas from high speed motorbikes and racing cars.Wetend to make the vehiclesstyle different from otherteams.At the same time, our new vehicle has these new characteristicsfor high performanceasfollowing:1.In order to get moreairto cool the engine, we decide to add an intake at either side of the vehicle.2.The whole bodyisdesigned accord aerodynamics for lower resistance.We made the 1:1 model of the bodywork from plastic foam by CNC and manufactured the final body withfiber glass.2.4SuspensionSuspensionSuspensionSuspensionNature frequencies were set to 2.6 Hz and 2.8 Hz in the front and rear respectively. Higher rear rate wasdetermined for ride reasons.Wepositioned roll center to 14mm above ground in the front, twice the value(28mm) in therear.They were set to this low height to reduce jacking force, while would never go acrossthe ground plane and remain within the track in roll even in extreme conditions.Lessons had learnt from last year, we added Anti-Roll Bars on HNU2008, thus the roll gradient was greatlyimproved to 1.02 deg/g. The ARBs were designed such that they could be easily adjusted by alteringtorque arm length, resulting in roll rate distribution varying from 40/60 to 60/40.Suspension kinematics & dynamics was simulated and optimized in ADAMS and Lotus SuspensionAnalysis. Longer links (compared with HNU2007) were selected to minimize parameters change. Frontswing arm length was set to 3000mm. It was determined to keep the front wheel upright under braking.Asa result, the camber gainis0.53 deg/in in bump and 0.79 deg/deg in roll. The tradeoff was large casterangles and minimum KPI angles.Weran 7 degrees of caster and 2 degrees of KPI. KPI was set for steeringarm packing reasons. And the angle was the same valueasthe maximum static negative camber, allowingthe steering axis parallel to the wheel installation surface, which resulted in easy manufacture. While in therear, the SAL was halved to about 1200mm, slightly larger than the track on the side, because of nocompensation of steering effect in roll. Besides, much less braking forceisgenerated in the rear, theresofless importance to keep the wheel upright. The result of camber gainis1.26 deg/in in bump and 0.50deg/deg in roll.KS-KIND coil-over shocks were employed on four corners. Opposed package was preferred for loadtransmission balanceaswellasminimizing the effect of frame stiffness.Asfor the bell cranks, specialattention was placed on them because the Big Mac on HNU2008 astonished everyone. The reduction ofweight was a main concern. Analysis in ANSYS proved the success of light weight. Kinematics wassimulated and optimized inADAMS, so the motion ratio changed within a minimal field.The goal in upright designisto reduce the weight and keep the enough strength.The front and rear uprightwas made by aluminum and were very simple design for easy to process by CNC machining. Rear uprightwas designed to T shape for two reasons. One was to enlarge toe baseaswellaseliminating bumpsteer.The other was to increase upright stiffness by splitting upper load to tie-rod and upperA-arms.Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT42.5SteeringSteeringSteeringSteeringSystemSystemSystemSystemAccording to the teamslatest tyre data and calculations, we chose to use upper steer .By using the positiveAckerman, the HNU2008 had been achieved using longer steering arms than the HNU2007. TheHNU2008 used the rack housingasthe HNU2007 which had been modified to reduceitsweight obviouslyby using aluminum to take the place of steel. By giving a final steering ratio about 4:1,and keeping theminimum steering diameter to about 7 m,we aimedat giving the driver a steering with a prompt responsewithout being too difficult to steer.?Weused ADAMS for simulation and optimization to get the accurate data and minimal change of toe angleduring wheel bump. Optimization in Matlab assures our geometry almost 110% Ackerman which providesgood handling and the ability for sharp corners.2.6PowertrainPowertrainPowertrainPowertrainThe HNUispowered by a Jialing JH600 F02 engine, an upgrade from the one installedin2007. Theengine has significant improvement suchasthe cylinder and ECU.The intake manifold has been specially designed to reduce losses and maximize the volume flow rate intothe engine. An air chamber was designed to make intake pressure stable,inorder to reduce the influence ofpressure waves to the sensors and reduce the noise of the exhaust system.The mandatory 20mmairintakerestrictor per FSAE rules was not ignored.With the 20mm restrictionontheairintake between the throttleand the engine,the power outputisseverely limited.Inorder to increase the power output whilst restricted,the restrictor was given a streamlined form to accelerate the rate of the flow.The fuel system has been implementedasan efficient, low weight, low cost and performance orienteddesign. The fuel tank was designed to adapt the body and frame of the racing car and steel was selectedasthe primary material of it both due toitssuperior strength,stableonheating and lower price. Itsalso easyto manufacture for a complex shape using 1.5 mm steel sheet.The cooling systemiscomposed of a radiator with a fan mountedonthe back,an overflow bottle andcoolant lines.The radiatorisone of the attachments of the engine.Aslarger convection areaisneeded forhigh efficiency, the radiator was locatedinthe side of thebody,whichisbetter for the engine comparedwith previous yearscar.Weare using a modified stock muffler to provide a good packaging for other parts suchasthe A-arms, CVand half shaft. One more important consideration was to keep itaslowaspossible to lower the CG.2.7DrivetrainDrivetrainDrivetrainDrivetrainThe final ratiois3.0 (45/15) which provided the driverasmuch torqueaspossible, while at the same timereducing the frequency of gear changes. The differential,together with the CV joint and half shafts werepurchased usedinan Xiali Car.The differential mounts were made by aluminum and was processed byCNC machining. Computer calculation proved them to be sufficiently strong and less weight.Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT53. 3. 3.3.AdditionalAdditionalAdditionalAdditionalMaterialMaterialMaterialMaterialCamberAngle VS. Wheel TravelToeAngle VS. Wheel TravelCamberAngel VS. Body RollAngleAnalyzeinANSYSBrakeAssemblyAckerman CurveHunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT64 4 44. . .EngineeringEngineeringEngineeringEngineeringDrawingsDrawingsDrawingsDrawings4 4 44.1 .1 .1.1FrontFrontFrontFrontViewViewViewViewHunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT74 4 44.2 .2 .2.2SideSideSideSideViewViewViewView1600160016001600mmmmmmmm(63(63(63(63in)in)in)in)Hunan UniversityHNU RacingFSAE WEST58#DESIGN REPORT84.3TopTopTopTopViewViewViewView1200mm1200mm1200mm1200mm(47.25in)(47.25in)(47.25in)(47.25in)1 1 11150150150150mmmmmmmm(47.(47.(47.(47.28282828in)in)in)in)汽车空调的二氧化碳冷却系统的工程和湿气-压缩吸收的测试摘要跨临界的二氧化碳冷却循环对环保来说是相当重要的，但是在高达120bar的高操作压力下它的应用具有很大的挑战性。湿气-压缩吸收 (WCA) CO2 冷却循环是通过把非挥发性液体加入 CO2 冷却循环系统实现的。CO2在液体中溶解度很高并且也很容易被解析。在 WCA CO2 冷却循环中，较高的压力少于35bar，大大低于跨临界的二氧化碳冷却循环。在这篇论文中，根据对工作液体的各项热力学分析，WCA CO2 冷却实验设备是通过限制现有汽车冷却单元的外形和操作包装构造的。正确的操作这个独特的设备为汽车空调传递足够的冷却条件。系统性能和周期律的关系及内部热交换器的效率要经过测试。设备使用的成分完全以现有的成份为基础而不是为提高效率追求最大化的潜在物质。关键字: 二氧化碳; 压缩-吸收的周期; 测试; 车辆; 空调1、简介与其他的冷却系统相较, 比如吸收或热电的冷却系统，蒸汽压缩系统由于他们的高效率而广泛的被使用。但是传统的蒸汽压缩系统对碳氟化合物的使用易对环境造成污染而逐步被淘汰。基于环境友好的潜在选择性冷却系统目前具有较低的性能需要发展更新的有更高价值的成分。这些问题很显然存在于传统的汽车空调的二氧化碳冷却系统中，即使CO2目前是替代CFC/HCFC的最好办法，跨临界的二氧化碳冷却系统承受较高的操作压力，不同于现有成分的成分具有较低的性能。为了减少跨临界的二氧化碳冷却循环系统的操作压力和费用，本论文经过研究将湿气-压缩吸收 (WCA) CO2 冷却循作为汽车空调。此循环将跨临界的二氧化碳冷却循环和吸收冷却循环联系在了一起。由于吸收剂吸收了二氧化碳在吸收体里，WCA CO2 系统解除压力重要地减少到不高于35bar以便那现有的成份为基于蒸汽压缩系统的碳氟化合物直接地被吸收。混合液体在系统各处流通。吸收体和解吸蒸发器分别地代替传统系统的凝结器。这不是第一次联合蒸汽压缩和吸收周期在冷却系统中。大部分共同的系统是带有VCCSC的蒸汽压缩循环。命名法一 区域 (m 2) x 离心因素C 周期 Dp 差别的压力 (Pa)d 公斤 kgA 1 干空气h 特性焓 (kJ kgA 1) 脚注m 块 (公斤) a 空气M 摩尔 (g molA 1) c 冷却；重要状态P 压力 (Pa) 压缩物q 空气流程率 (m 3 sA 1) h 高温Q 热流出 (千瓦) I 工作液体T 温度 (K) 物体内部V 体积 (m 3) 1 低温W 力量 (千瓦) n 混合的成分编号x 摩尔分数 物体外部q 密度 (公斤)g 效率 r 比率Groll 发展了一个样品单位并总结了1998年之前的研究成果。他对在以 CO2/丙酮作为工作液体对VCCSC在实验和数字的研究具有显著的成就。与 NH3/H2 O 系统相比,CO2/丙酮在高度温度环境应用下具有很大的竞争力, 像是热邦浦。Itard 和 Machielsen 发展了以 NH3/H2 O 作为工作液体的一个实验的 VCCSC 样品单位。他们发现对外表面的局部条件最好将全部NH3浓缩在制高点上。与蒸汽压缩系统相较, VCCSC 的主要优势是较高的潜在性能、新的能力控制选项、操作压力的减少。尽管VCCSC的性能具有恨得吸引力, 但系统对安装空间受限制的汽车空调的系统条件要求叫复杂。因此, 在WCA 周期通过在VCCSC 取消解决线路, 单一化能潜在减少工作压力的系统程序。 Spauschus获得二个基于 WCA 周期 的冷却系统专利. 连同 Visteon 一起,Spauschus 呈现他们的起始测试结果。 结果表示 CO2 WCA 周期是有能力递送足以支撑的冷却能力。同时地, 一个源自制高点的周期模型包含了CO2/能吸收的混合特性和外部的环境条件也得到了改善。后来的工作描述了一个 WCA CO2冷却系统周期模型。模拟展现了IHX 的性能和周期比在系统性能上具有很强的影响。在这篇论文中，不是以设计和生产出一种商业上可行的新的冷却产品。相反的，主要目的是对于汽车应用使用的WCA CO2冷却系统在概念示范上的证明，以及找到了系统性能、周期比和IHX性能之间的关系，哪一个对以后的研究有更深远的影响。2、原型设计和测试设备2.1、程序和器具图表图表展示了整个测试设备的结构。户外的房间环境的情况由一个电的加热器和一个空调控制着, 而户内的房间环境由一个电加热器、一个增湿器和一个空调控制着。能够驱动风扇的变速度马达安装在每个房间中的空气输送管中模拟不同的热交换器在实际应用中遇到的空气速度。气流率是以喷嘴测试。温度和湿气是以 Pt100 温度计测试。 科里奥利块流程公尺, 连同 T 热电偶和压力转换器一起安装在每个成份区域的冷冻边缘的上下部分。压缩物体的力用测力计直接地测量, 包括有带子和没有带子的损失。测试台简单的反映了感应器的准确性和功能。在图中也展示了 WCA CO2 冷却原型单位环。WCA 原型的主要的成份被挑选出来与汽车空调应用中现有的 R134系统外部尺寸大致相配。系统成份的概要列在表 2。安装了三副感光镜来监测工作液体的状态。WCA 的工作程序周期是:在解吸过程中,超过了蒸发温度工作混合液体中更多挥发性成份 (CO2)就会蒸发消失。在这之后, CO2 蒸汽和吸收了C5H9的液体被压缩到一有利于吸收体吸收的高压环境。在吸收过程中,热气不经过热洗涤槽,并且CO2蒸汽被C5H9NO所吸收。此过程完成后最终回到吸收体中。IHX被用来传送热气从高温溶液到低温溶液。在低温的IHX中样品单位利用旁路管道控制它的效率。表 1器具规格和功能项目 准确性量功能 PT100 0.1 C 4 空气边温度和湿气T 热电偶 0.2 C 15 冷冻的边温度压力下降转换器 2.5 Pa 2 空气边压力不同完成的喷嘴压力转换器 0.5 酒吧 6 冷冻的边绝对的压力力量公尺 0.02个千瓦 1 压缩物力量输入流程公尺 0.8 公斤/h 1 冷冻的块流程率RPM 公尺 10个转/每分 1 压缩物速度表 2原型的主要部份成份项目 规格 压缩物 卷桥压缩物, 换置 89 cc/转吸收体 明矾的, 六个途径平行流程热交换器,装有百叶窗板的有鳍, 740. 290.(L 。 W 。 H)使解吸 明矾的, 15条途径带子-管热交换器,装有百叶窗板的有鳍, 305. 185. 90(L 。 W 。 H)IHX 青铜碟子热交换器, 总数热移动区域: 0.9 m 2扩充活瓣 手册, 大头针-活瓣接收器 明矾的, 体积: 1500 cm 3 图 1. 原型和测试设备。2.2. 不确定分析主要的实验结果是解吸空气流程率q,系统冷却能力Qc,压缩物力量输入W补偿和性能系数。这些叁数之间的关系是:C 是一个常数, 0.99; n喷嘴的喷嘴区域;Dp经过喷嘴的压力差;qa在喷嘴插入处的空气密度;hin和hout是吸收体分别在吸收和释放时的空气