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1西华大学毕业设计说明书目录摘要···································································································2Abstract·····························································································31引言·································································································41.1课题的背景和意义···········································································41.2国内外发动机冷却系统研究现状及发展方向··········································41.3本次设计的主要内容········································································62475Q汽油机工作过程计算····································································72.1已知条件·······················································································72.2参数选择·······················································································82.3额定工况工作过程计算·····································································83475Q汽油机冷却系统的设计································································113.1冷却系统的作用············································································113.2冷却系统的设计要求······································································113.3冷却系统的总体设计方案和参数选取·················································113.4散热器设计及选型·········································································133.5风扇的设计及选型·········································································183.6水泵设计及选型············································································243.7475Q汽油机冷却系统的调节机构······················································294475Q汽油机冷却系统整体布置图························································355结论······························································································36总结与体会························································································37谢辞·································································································38参考文献···························································································39附录1475Q汽油机工作过程计算源代码及运行结果·································40附录2475Q汽油机冷却系统布置图······················································51附录3475Q汽油机纵剖面图·······························································522西华大学毕业设计说明书475Q汽油机冷却系统的设计摘要冷却系统的作用是使发动机总是工作在最佳温度范围内。本设计通过在475Q汽油机额定功率工况下进行的工作过程计算，对该汽油机冷却系统的参数进行了计算并对其总体布置方案进行了设计。本设计在475Q汽油机冷却系统总体设计的基础上，同时也对该冷却系统中的各组成，如散热器、水泵、风扇、节温器、进行了一系列的计算、选型、布置设计和匹配研究。结果表明，本设计所选择的各个部件都符合475Q汽油机的冷却要求，保证了该汽油机在各种环境下都能工作在最佳温度范围内。关键词：475Q汽油机，冷却系统，散热器，水泵，风扇3西华大学毕业设计说明书TheDesignofCoolingSystemfor475QGasolineEngineAbstractThepurposeofthecoolingsystemistomaketheenginealwaysworkinthebesttemperaturerange.Thedesignandcalculationofworkthroughtheprocessinthe475Qgasolineengineratedpowerconditions,theparametersofthecoolingsystemofthegasolineenginewerecalculatedandthegenerallayoutschemeisdesigned.Thedesignisbasedonthegeneraldesignofthecoolingsystemfor475Qgasolineengine,butalsoonthecompositionofthecoolingsystem,suchasradiator,fan,waterpump,thermostat,werecalculated,andaseriesofselection,layoutdesignandmatchingstudy.Theresultsshowthat,thedesignofeachpartoftheselectedareconsistentwith475Qgasolineenginecoolingrequirements,ensurethattheenginecanworkatthebesttemperaturerangeinavarietyofenvironments.Keywords：475QGasolineengine,Coolingsystem,Waterpump,Fan,Radiator4西华大学毕业设计说明书1引言1.1课题的背景和意义随着现代车用发动机采用更加紧凑的设计和更大的单位体积功率,强化程度越来越高,发动机产生的热流密度也随之明显增大,目前几乎所有的发动机强化都面临着如何解决高功率密度下的冷却及热平衡问题,在满足不断提高的输出功率的同时,又要具有良好的经济性。此外,日益严格的排放标准也对冷却系统提出了新的要求。冷却系统工作性能的优劣,直接影响着动力系统的整体性能。冷却系统即便出现小的故障也可能在排气门散热周围的区域造成灾难性的后果。发动机冷却系统的散热能力一般应满足发动机满负荷时的散热需求，已为此时发动机产生的热量最大。然而，在部分负荷时，冷却系统会发生功率损失，水泵所提供的冷却液流量超过所需的流量。发动机冷起动时间应尽可能短，因为发动机怠速时排放的污染物较多，油耗也大。而冷却系统的结构对发动机的冷起动时间有较大的影响。现代的发动机设计充分考虑这些问题，将发动机的热量管理系统纳入到整个发动机控制系统中，全面考虑发动机的暖机、冷却效率、废气排放控制、燃油利用、乘客室的取暖和三元催化剂活化时间等。目前的冷却系统属于被动系统，只能有限地调节发动机和汽车的热分布状态[1]。开发高效可靠的冷却系统,已成为发动机进一步提高功率、改善经济性所必须突破的关键技术问题。因此,采用先进的冷却系统设计理念,对发动机冷却系统进行深入研究具有十分重要的实际意义。1.2国内外发动机冷却系统研究现状及发展方向1.2.1国外发动机冷却系统发展方向传统冷却系统采用的是冷却风扇或离合器式冷却风扇，两种风扇均由发动机曲轴通过皮带驱动，其冷却灵敏度不高，功率损失也大。为优化风扇，就出现了自控电动冷却风扇。最早的汽车电动冷却风扇出现在1981年三月的美国专利文件中（专利号US4257554），该专利提出使用电动风扇替代传统的皮带带动，根据发动机温度和负荷的不同实现风扇的运转；1985年德国大众在中国申请专利（专利号5西华大学毕业设计说明书CN851095/A），此专利在汽车散热器前方设置空气输入口和辅助通口，加快散热器散热，降低风扇能耗；1989年，美国发明专利（专利号US4875521），该专利首次在载重货车上采用电动风扇；1999年，法国Valeo公司提出在发动机上配置智能热调节系统的新型电控系统，改善发动机的冷却性能。上世纪70年代，美国、日本、英国等国家提出了“绝热发动机”，其基本思路是对发动机燃烧室表面进行耐高温陶瓷的喷涂，从而减少散热损失[2]。经过数十年的发展，绝热发动机在高温陶瓷零件方面取得了较大成功。绝热发动机的整机热效率接近40%，复合式绝热发动机的整机热效率达到了40%以上。目前，还出现了发动机常规冷却机理中的强化冷却措施，如活塞的“內油冷”、排气门的“钠冷”以及喷油嘴的“內油冷”等内冷技术。另外，采用的一些节油技术也具有内部冷却的功能，如乳化柴油、进气喷水、进气引气、代用燃料冷却和过量空气冷却等。1.2.2国内冷却系统的发展方向目前国内对发动机冷却系统的研究手段主要为试验研究和计算机模拟数值研究。在冷却液流动研究方面，以朱义伦等人为代表的采用多普勒测速仪（LDV）进行发动机缸盖冷却液流动测量，得到了冷却水在平行于缸盖和缸体结合面之间的二维流场；以王书义等人为代表的利用流动显形法得到冷却水流动的二维流场，通过研究冷却流场以改进水腔设计。通过计算机模拟数值研究，利用CFD分析技术及有限元（FEA）耦合分析技术对冷却液流场进行模拟。目前常用的技术载体，如大型的CFD商业软件有FLU2ENT，STARCA，FIRE等。计算机软硬件水平飞速提高，使得采用计算机模拟数值研究复杂结构水腔内流动特性成为了越来越重要的研究手段[3]。自主品牌长城汽车近年来也在发动机冷却系统方面取得了许多技术成果，如充钠气门，通过在气门内充入金属钠，利用比热较大的钠快速吸收和传递热量，降低气门的在恶劣工作环境下的温度；如无极变速风扇，相比传统的2级或3级转速的散热器风扇，该技术可以做到风扇转速的无极调节，进