虚拟风洞下的车辆散热器模块性能改进

引用本文

刘佳鑫, 秦四成, 徐振元, 张奥, 习羽, 张学林. 虚拟风洞下的车辆散热器模块性能改进. 2014, 44(2): 330-334[LIU Jia-xin, QIN Si-cheng, XU Zhen-yuan, ZHANG Ao, Xi Yu, ZHANG Xue-lin. Improvement and analysis of heat exchange performance of vehicle radiator module in virtual tunnel. 吉林大学学报(工学版), 2014, 44(2): 330-334] 复制到剪切板

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虚拟风洞下的车辆散热器模块性能改进

刘佳鑫¹², 秦四成¹, 徐振元¹, 张奥¹, 习羽¹, 张学林¹

1.吉林大学机械科学与工程学院,长春 130022

2.徐工集团徐工道路机械事业部,江苏徐州 221000

刘佳鑫(1983),男,博士研究生.研究方向:工程机械系统节能.E-mail:nihao9002002@yahoo.com.cn

基金:国家自然科学基金项目(50775096); 国家科技支撑计划项目(2013BAF07B04);

摘要

为了提升车辆散热器模块性能,保证车辆工作可靠性,在已有的研究基础上提出3种改进方案,依据图纸资料建立动力舱三维模型,使用热交换模型代替散热器模块,结合CFD数值方法在虚拟风洞内对各改进方案进行仿真,根据仿真结果进行评估。结果表明:3种改进方案均能提高车辆散热器模块性能,其中在消声器附近增加空气出口效果最好,与原始模型对比,中冷器、水、液压油散热器热流体出口温度分别降低了14.48%、1.39%、2.28%。

关键词: 车辆工程; 动力舱; 散热器; 数值分析; 热交换

中图分类号:U415.52 文献标志码:A 文章编号:1671-5497(2014)2-330-5

Improvement and analysis of heat exchange performance of vehicle radiator module in virtual tunnel

LIU Jia-xin¹², QIN Si-cheng¹, XU Zhen-yuan¹, ZHANG Ao¹, Xi Yu¹, ZHANG Xue-lin¹

1.CollegeofMechanicalScienceandEngineering,JilinUniversity,Changchun 130022,China

2.RoadMachineryDivisionofXuzhouConstructionMachineryCo.,Ltd.,Xuzhou 221000,China

Fund:

Abstract

In order to improve the vehicle radiator capacity and keep vehicle reliable, three new improvement schemes were proposed on the foundation of former research. A 3D model based on the drawing from manufactures was set up. Heat exchange model was used as substitute for radiator module. Each improved model was simulated in virtual tunnel with commercial CFD software. These schemes were assessed based on the simulations. The results show that all of three schemes could enhance radiator performance. Addition of air exits near muffler has the best effect. Compared with original model, the intercooler, water radiator and oil radiator of the improved schemes could lower the thermal fluid outlet temperature by 14.48%, 1.39% and 2.28%, respectively.

Keyword: vehicle engineering; engine cabin; radiator; numerical analysis; heat exchange

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引言

工程车辆动力舱内具有较多的发热部件,这些部件的布置形式、工况载荷均会影响散热器模块性能及动力舱内热流场特征^[1]。目前国外最新研究成果是采用激光感应散热器冷流体侧与热流体侧分布点的温度,利用温度变化实时调整控制策略^[2];也有部分研究侧重于散热器的几何特征对性能的影响,通过改变压阻特性强化其散热性能^[3];还有部分学者利用风洞结合含有纳米粒子的冷却液来进一步提高换热性能^[4]。实际上,散热器从风洞安装到车上后,实际性能会出现降低,甚至出现换热性能不佳致使系统过热的现象,该现象的产生与整车设计中散热器布置方式等有着极为密切的联系^[5,6]。作者曾结合国内目前主流的压路机就动力舱几何特征与散热器的组合特征进行了初步研究^[7,8,9],结果表明,具有规则几何特征的动力舱配合侧置的散热器组可以有效地提高整车散热性能。

本文在已有研究的基础上,结合国内某型压路机使用ANSYS/CFD数值仿真模块对散热器传热性能进行分析,主要涉及冷却风扇与散热器组之间的布置方式、增加动力舱空气出口两方面对散热器模块性能变化的影响。

1 动力舱以及风洞模型

1.1 冷却风扇模型^[10,11]

式中: 为空气密度; 为叶片切面相对半径; 为风扇叶片半径; 为冷却风扇轮毂比; 为经过冷却风扇的空气体积流量; 为冷却风扇静压。

风扇几何尺寸确定后,面向大气的风扇静压近似表达为关于体积流量平方的二次函数。利用式(1)可以初步拟合多转数下的面向大气时风扇静压值来表征风扇性能。

1.2 散热器模型

目前的国内外研究大部分采用散热器压阻与换热量作为其性能表征。本文采用效能单元法进行换热性能计算。其具体表达式^[11]为

式中: 为散热器散热效率; 为散热器换热量; 为热流体入口温度; 为冷流体入口温度; 分别为热、冷流体的定压比热; 分别为热、冷流的质量流率。

散热器压阻表达式为

式中: 为冷流体密度; 为通流面积; 分别为进口和出口阻力系数; 为水力直径。

为获取散热器压阻与换热特性,本文结合供应商提供的资料,提取所需的变量对性能曲线进行拟合。

1.3 动力舱及风洞模型

根据生产厂商提供的设计图纸建立动力舱三维模型。为了便于网格划分,尽量在不影响仿真结果的前提下对模型进行简化,具体模型如图1所示:

	Figure Option View Download New Window
	图1 动力舱三维模型Fig.1 Engine cabin three-dimensional model

风洞模型参见文献[7-9]。1-空气滤清器;2-动力舱空气出口A、B;3-动力舱;4-发动机机体;5-消声器;6-振动轮;7-冷却风扇;8-导风罩;9-动力舱空气进口;10-液压油散热器;11-水散热器;12-中冷器;13-燃油箱

2 CFD数值仿真

温度边界、网格划分、工况选定、实验验证具体见文献[7-9],选用标准湍流模型^[12,13]。

在保持动力舱内各部件总体位置不变的前提下,提出3种可行的改进方案:①调整冷却风扇相对于散热器组的轴向距离。将冷却风扇沿轴向远离散热器组方向移动12.5 mm。②调整冷却风扇相对于散热器组的径向位置。将冷却风扇沿径向方向移动37 mm,使冷却风扇居中。③增加高温区域动力舱空气出口,在消声器附近增加两个空气出口。各改进方案在原方案基础上通过修改模型几何特征实施,依照改进方案分别建立模型1、模型2、模型3,具体如图2所示:

	Figure Option View Download New Window
	图2 改进方案模型图Fig.2 Improvement model

由图3可知

	Figure Option View Download New Window
	图3 改进模型风扇中心处散热器模块的温度分布Fig.3 Temperature contour of radiator module at cooling fan center of improvement model

模型3流经中冷器空气温度变化明显,该模型中水散热器内部空气绿色高温区域最小,液压油散热器下端的高温区已消失。与原模型相比,模型1、模型3中散热器散热效率有所提升,较明显特征是水散热器出口处的黄色高温区消失。

由图4可知:

	Figure Option View Download New Window
	图4 改进模型风扇中心处散热器模块的压力分布Fig.4 Pressure contour of radiator module at cooling fan center of improvement model

模型1散热器内部出现较大范围的连续低压区,加大冷却风扇与散热器组间的距离使得冷却风扇前端空气流动性得以充分改善。模型3散热器进出口压强差绝对值较高。与原模型相比,模型1、模型2散热器进出口压差均有所增大。

由图5可知:

	Figure Option View Download New Window
	图5 改进模型风扇中心处动力舱的温度分布Fig.5 Temperature contour of engine cabin at cooling fan center symmetrical place of improvement model

改进模型在冷却风扇出口处温度变化不明显,但在发动机及消声器附近温度变化较大,其中模型1中的黄色高温区范围较广。模型3中高温区域较小是由于其附近的高温气体从新增出口流出,具体见图6:

	Figure Option View Download New Window
	图6 改进开口处的温度云图Fig.6 Temperature contour of improved air exit

由图7可知:

	Figure Option View Download New Window
	图7 改进模型风扇中心处动力舱的压强云图Fig.7 Pressure contour of engine cabin at cooling fan center symmetrical place of improvement model

由于改进模型仅针对散热器模块及动力舱出口,所以动力舱内部的压强变化趋势相差不大。

3 对比分析

提取原模型与3种改进模型中散热器热流体出口温度,具体如表1所示:

表1 原始模型与改进模型热流体出口温度对比表 Table 1 Outlet temperature of thermal fluid in original and improvement models

由表1可知,改进模型3综合效果最好,该模型通过减少热空气在动力舱内的滞留时间、减少热空气回流改善了散热器模块热环境,同时改进模型3实施成本较低,易于实现。

4 结束语

以国内某型双钢轮振动压路机为研究对象,利用热交换模型和CFD数值方法对车辆散热模块换热性能进行了仿真研究。针对提出的3种改进方案分别建立模型并进行仿真,结合仿真结果对方案进行了评估,为实际的车辆散热系统设计提供了一定参考依据。

The authors have declared that no competing interests exist.

参考文献

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2010

0.0

2.996

... 引言工程车辆动力舱内具有较多的发热部件,这些部件的布置形式、工况载荷均会影响散热器模块性能及动力舱内热流场特征^[1] ...

2012

4.781

0.0

. 2012, 91(1):null-null

Fan air flow analysis and heat transfer enhancement of vehicle underhood cooling system#cod#x02014;towards a new control approach for fuel consumption reduction

... 目前国外最新研究成果是采用激光感应散热器冷流体侧与热流体侧分布点的温度,利用温度变化实时调整控制策略^[2] ...

2009

0.0

... 也有部分研究侧重于散热器的几何特征对性能的影响,通过改变压阻特性强化其散热性能^[3] ...

2010

1.581

0.0

. 2010, 31(4):613-621 DOI:10.1016/j.ijheatfluidflow.2010.02.016

Numerical study of fluid dynamic and heat transfer performance of Al₂O and CuO nanofluids in the flat tubes of a radiator

Abstract

A three-dimensional laminar flow and heat transfer with two different nanofluids, Al₂O₃ and CuO, in an ethylene glycol and water mixture circulating through the flat tubes of an automobile radiator have been numerically studied to evaluate their superiority over the base fluid. New correlations for viscosity and thermal conductivity of nanofluids as a function of particle volumetric concentration and temperature developed from the experiments have been used in this paper. Numerical results from the present simulation were first validated for the flow of water by comparing the friction factor and the Nusselt number in flat tubes, for which accurate results are available in the literature. Next, the model was applied to study the peripheral variations of shear stress and convective heat transfer coefficient, both showing higher magnitudes in the flat regions of the tube. Convective heat transfer coefficient in the developing and developed regions along the flat tubes with the nanofluid flow showed marked improvement over the base fluid. Results for the local and the average friction factor and convective heat transfer coefficient show an increase with increasing particle volumetric concentration of the nanofluids. Quantitative results of the increase of the heat transfer coefficient and the friction factor with increasing volumetric concentrations of nanofluids at various Reynolds numbers are presented. The pressure loss increases with increasing particle volumetric concentrations of nanofluids; however, due to the reduced volumetric flow needed for the same amount of heat transfer, the required pumping power diminishes.

... 还有部分学者利用风洞结合含有纳米粒子的冷却液来进一步提高换热性能^[4] ...

0.0

... 实际上,散热器从风洞安装到车上后,实际性能会出现降低,甚至出现换热性能不佳致使系统过热的现象,该现象的产生与整车设计中散热器布置方式等有着极为密切的联系^[5,6] ...

0.0

2012

0.0

... 作者曾结合国内目前主流的压路机就动力舱几何特征与散热器的组合特征进行了初步研究^[7,8,9],结果表明,具有规则几何特征的动力舱配合侧置的散热器组可以有效地提高整车散热性能 ...

2012

0.0

0.701

. 2012, 42(4):834-839

Numerical simulation analysis of heat transfer performance of vehicle radiator module in a virtual wind tunnel

College of Mechanical Science and Engineering, Jilin University, Changchun 130022, China

In order to enhance the heat transfer performance and inprove the temperature field in the engine cabin to keep the vehicle performance stable, a 3-D physical model was built inside and outside the engine cabin according to the system drawing. A heat exchanger model was used instead of the radiator module in the engine cabin, the CFD numerical analysis was used to simulate the heat transfer performance of the engine cabin in a virtual wind tunnel at standard working conditions. The temperature fields and flow fields in the radiator, inside and outside the engine cabin were obtained. The comparison between the experiment data and the simulation results shows that the discrepancy is acceptable, proving the effectiveness of the model and the accuracy of CFD numerical analysis.

为提高车辆散热器模块性能和改善动力舱温度场以保证车辆工作性能稳定,依照图纸建立动力舱内、外的三维物理模型,使用热交换模型来代替动力舱内散热器模块,利用CFD数值仿真方法在虚拟风洞中模拟车辆动力舱在标准工况下的传热性能,分析总结散热器、动力舱内外的温度场与流场特点。通过将实验数据与仿真结果对比发现误差在可接受范围内,验证了文中模型的有效性以及分析的准确性。

2012

0.0

0.608

. 2012, 47(4):623-628 DOI:10.3969/j.issn.0258-2724.2012.04.014

Numerical simulation of heat exchange performance of radiator module in construction vehicles

College of Mechanical Science and Engineering, Jilin University, Changchun 130025, China

In order to study the performance law of a construction vehicle radiator under different working conditions and ensure its working stability, a 3D physical model of the vehicle engine cabin was built based on original drawings with the software UG NX7.0, in which a heat exchange module was adopted to represent the radiator group. Then, the engine cabin model in a virtual tunnel was simulated using the computational fluid dynamics (CFD) numerical method, and the heat exchange performance of the radiator module was analyzed under various working conditions. Finally, the simulation results were verified experimentally. The results show that the heat exchange process has a gradient temperature change in each working condition, and increasing the temperature of the hot-air backflow will lower the radiator efficiency. When the radiator efficiency can not meet the need of the whole vehicle system, system overheating and performance instability occur. The error between simulation and experimental results is between 2.83% and 4.07%.

为了了解工程车辆散热器模块在不同工况下的性能变化规律,保证其工作稳定性,结合工程车辆的原始资料,在UG NX7.0软件中建立动力舱的三维物理模型.用热交换模型表征车辆散热器模块,采用CFD数值方法对虚拟风洞内的动力舱模型进行仿真,对各工况下散热器模块散热性能进行分析,并进行实验验证.结果表明:各工况下散热器内部热交换过程均呈现梯度变化;随着回流热空气温度升高,散热器的工作效率逐步降低.当其效率不能满足整车需要时,整车会出现系统过热以及工作性能不稳定现象.对比仿真与实验数据,两者误差在2.83%~4.07%之间.

2001

0.0

... 1 冷却风扇模型^[10,11] ...

2012

0.0

... 1 冷却风扇模型^[10,11] ...

... 其具体表达式^[11]为 ...

2007

0.0

0.3603

. 2007, 25(3):351-356

Research on aerodynamic characteristics during the vehicle overtaking process

采用稳态和瞬态两种方法,对两辆车超车过程中外部流场的空气动力特性进行了数值模拟研究.采用网格变形和局部网格重构相结合的动网格技术,并耦合刚体动力学方程和PISO算法实现了汽车超车过程的三维瞬态数值模拟.通过稳态和瞬态计算,探讨了超车过程中两车纵向相对位置对气动特性的影响以及气动力对汽车行驶稳定性的影响.研究发现超车过程中被超车的阻力、侧向力和横摆力矩都有最大值,并找出了其变化规律.通过对稳态与瞬态计算结果的比较,可以看出:本文采用的瞬态模拟方法能够充分捕捉超车过程中的动态效应,优于传统的稳态模拟.

... 2 CFD数值仿真温度边界、网格划分、工况选定、实验验证具体见文献[7-9],选用标准湍流模型^[12,13] ...

2006

0.0

0.701

. 2006, 36(6):871-875

Aerodynamic characteristics of vehicle platoon

<FONT face=Verdana>College of Automotive Engineering, Jilin University, Changchun 130022，China</FONT>

In order to reveal the effects of the longitudinal spacing between the vehicles and vehicle number in platoon on the aerodynamic drag coefficient of vehicle platoon, the numerical simulation method was used to study the aerodynamic characteristics of 11 cases of a serial vehicle platoon in the intelligent transport system. Results indicated that the drag of platoon decreases with the decreasing of the vehicle spacing at fixed vehicle number. At fixed longitudinal spacing, with the increasing of vehicle number in platoon the average drag coefficient may decrease by 20%_30% and the vehicle with the lowest drag is about at the center of the platoon.

为了研究队列行驶时，车辆前后间距对队列行驶车辆气动特性的影响以及队列中车辆数目对气动阻力系数的影响，采用数值模拟方法分别对智能交通系统中队列行驶车辆11种不同情况下车辆的气动特性分别进行了研究。结果表明：队列行驶车辆随车间距离的缩短，阻力值降低。在固定间距下，随着队列中车辆数目的增加，平均阻力系数可降低20%-30％，阻力最低的车大致处于车队的中心位置。

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