【作者】 刘传超；

【导师】 张彬乾；

【作者基本信息】 西北工业大学 ， 流体力学， 2005， 硕士

【摘要】 国外对于汽车空气动力学的研究起步很早,而我国国内最近几年也对汽车空气动力学的重视程度也越来越高。本文结合与东风汽车有限公司合作的“关于东风D310型汽车外流场流动特性和发动机舱内流场及散热特性”课题,针对载重汽车的外部流场和发动机舱内流动情况,采用计算空气动力学数值模拟方法,利用FLUENT商用软件,探索模拟载重汽车外部绕流、发动机舱内部流动的方法:在对载重汽车内—外部流动数值模拟的基础上,研究通过理论分析、实验数据和工程方法相结合的技术途径解决发动机舱散热问题的工程方法。并提出了一些改善流场的意见和建议。本论文的主要内容有以下几个方面: 1) 回顾了国内外汽车空气动力学的发展历史,查阅了大量的资料,通过具体的数据来了解汽车空气动力学对于汽车的性能、外观、环保以及能源等方面的重要性和实用性,研究分析了国内外汽车气动力与流场计算方法。 2) 针对汽车空气动力学周围绕流流场以及发动机舱内流场的流动特性,选择不可压缩雷诺平均的RANS方程作为控制方程,采用了有限体积法对方程进行空间的离散,然后通过SIMPLE方法进行迭代求解,计算过程中所采用的湍流模型是一方程约束的S-A湍流模型。所采用的网格生成软件是FLUENT的前置处理器GAMBIT作为网格生成工具。计算软件选用的是FLUENT计算软件,同时利用FLUENT进行后置处理。 3) 通过轿车标模对本论文的计算方法进行了验证。对东风D310型载重卡车的外部流场进行了数值模拟,并得出了该车型外部流场的流动特性以及阻力系数等参数,并与国外的试验数据进行了对照,结果合理。 4) 针对载重汽车发动机舱内部流动情况,采用外部流动与发动机舱内部流动耦合求解方法,计算了发动机舱内部流场特性,计算结果合理。 5) 在对发动机舱内部流动数值模拟的基础上,通过理论分析、实验数据和工程方法相结合的方法,计算了发动机舱散热特性,与实验结果吻合较好。 6) 根据本文和国内外研究结果,分析研究了载重汽车的外部流动对汽车阻力、升力、气动噪声等方面的影响,并针对这些问题,探讨了一些控制方法。更多还原

【Abstract】 On account of energy source crisis and improvement of motorcars speed, since last century people are paying more and more emphasis on the applying of aerodynamics to automobile work. It was researched early overseas, but recent years the domestic research also has made great progress. This paper analyses the trucks’ outer flow field, its flowing circs inside the engine cabin and its scattering heat trait and connected with the subject cooperated with Dongfeng Automobiles Corporation Ltd., which named "the analysis of a Dongfeng D310 lorry’s outer flow, the flowing analysis inside the engines and scattering heat character". Furthermore on the basis of analysis and research of lorrys’ character of the flow field in this paper introduces the basic theory, the methods of request numerical method, the grid system, the choice of turbulence model and the introduction of CFD software. And according to the analysis result this paper introduces camion’s characters of and scattering heat in engine and the character of flowing field all around on which the author puts forward some improvement steps. The content of this paper as follows:1.Because of the improvement of automobiles’ speed and the crisis of energy source induct the aerodynamics. Introducing the aerodynamic effect on motorcars’ various capability.2.The control equation is three-dimensional uncompressable RANS equation, applies control volume to disperse it in spatial and request its answer iteratively by SIMPLE method. And adopt GAMBIT software to build the structure-unstructure admixture grid, FLUENT software to dispose its data.3.Arithmetic validating by the car’s outer flow field numericalsimulation. The validation result shows that the surface pressure distribution adapts to the experimental result appropriately, which validates that the calculation method of this paper is feasible, the pressure distribution, flow characteristics and aerodynamic drag of the camion are obtained. The results have shown with good precision on small grids amount. Finally, the ways to decrease aerodynamic drag are indicated. The calculation result adapts to the distributing rule of great type of freight automobiles, and the calculation of the drag is smaller than the similar vehicle type used in the classical wind tunnel experiment overseas,this is only because the the cargo box of this camion is not included.4.The numerical simulation on the flowing field of engine cabin is in use of inner-outer coupling calculation method .The computing grid of the cabin in engine and the outer flowing field is established. During the course, media theory, porous jump boundary condition were introduced to simulate the radiator’s draught condition, meanwhile fan’s capability was used in calculating course. The method of calculating the engine cabin’s scattering heat character is conversion of air mass and heat flux. On base of the relation of the conversion of flux and heat, and the outcome tested by the research and exploitation center for commercial camion of Dongfeng Automobiles Corporation Ltd. A a dispose on flowing air mass and flowing heat is maded, and the heat carried by radiator is educed. This paper adopts the conversion relation of heat and temperature to dispose the cooling impact. The quantity of heat carried by radiator reflects the decrease of water in it, thus conclude the cooling water temperature falling. This paper uses two types flux of cooling water: 175L/min and 280L/min to educe that the temperature of cooling water inthe mouth of radiators falling 11℃ and 8℃ respectively.5.Connecting with the calculation result of this dissertation, The characters of camion’s flowing field and its effect on motorcars is simply analyzed when it is moving.更多还原