汽车油箱燃油晃动CFD模拟分析

2016-08-31 by:CAE仿真在线来源:互联网

汽车燃油系统是汽车至关重要的部件之一,它关系到每个乘客的生命安全。在刹车和启动过程中,燃油对油箱壁撞击所产生的压力影响到整个燃油系统的稳定性,压力变化引起的振动噪声也是衡量整车舒适性的重要指标之一。因此,燃油晃动一直是燃油系统开发过程中需要研究的重点和难点问题。使用Fluent软件运用VOF方法对汽车燃油箱进行了汽车加速/刹车过程中的燃油晃动模拟,可以得到燃油晃动过程中油箱壁的压力分布和压力变化,为燃油系统的开发和优化提供了指导和理论依据。

Automobile fuel system is one of the most part of automobile is one of the most important, it is related to the safety of all the passengers. In braking and starting process, the fuel to the fuel tank wall impingement generated pressure influence to the stability of the entire fuel system, pressure changes caused by vibration and noise is also weighs in the amount of vehicle comfort is one of the important indexes. Therefore, fuel sloshing has been fuel system in the process of developing the key issues. Through the use of software fluent with VOF method of automobile fuel tank for automobile acceleration / braking process of fuel sloshing simulation can fuel sloshing in the tank wall pressure distribution and pressure variation. It provides guidance and theoretical basis for the development and optimization of the fuel system.

VOF模型

volume of fluid model

所谓VOF模型是一种在固定的欧拉网格下的表面跟踪方法。当需要得到一种或多种互不相融流体间的交界面时,可以采用这种模型。在VOF模型中,不同的流体组分共用着一套动量方程,计算时在全流场的每个计算单元内,都记录下各流体组分所占有的体积率。VOF模型的应用例子包括分层流,自由面流动,灌注,晃动,液体中大气泡的流动,水坝决堤时的水流,对喷射衰竭(jet breakup)(表面张力)的预测,以及求得任意液-气分界面的稳态或瞬时分界面。

Prediction failure examples include the application of.VOF in so-called VOF model is a fixed Eulerian mesh surface tracking method. When you need to get a species or variety of mutual incompatibility between fluids interface, can be used in the model. In the VOF model, different fluid components share a set of momentum equation and calculation in the whole flow field of each calculation unit, record the fluid group branch occupies the volume rate model of stratified flow, free surface flow, perfusion, sloshing, liquid bubble flow, the dam burst flow, the jet (jet breakup) (surface tension), and obtained for any liquid Gas interface steady or transient interface.

使用FLUENT软件进行启动/刹车过程中燃油晃动的模拟,需要将空气设置为多相流的主项,燃油设置为多相流的次相进行计算。

Using FLUENT software to start / brake process of fuel sloshing simulation, the need to set the air as the main item of multiphase flow, fuel is set to multiphase flow calculation of the sub phase.

用户自定义函数UDF

User defined function UDF

UDF(用户自定义程序)是FLUENT提供的用户编程环境,以解决标准FLUENT本身不能解决的问题。用户自定义函数用C语言编写,使用DEFINE宏来定义。UDF中可使用标准C语言的库函数,也可使用Fluent提供的预定义宏,通过这些预定义宏,可以获得Fluent求解器得到的数据。

UDF (user defined function) is provided by fluent user programming environment, to solve the standard fluent itself will not solve the problem. User defined functions written by C language, using the define macros to define standard C language library functions can be used in the.UDF, also can be provided by fluent predefined macros, through these predefined macros can obtain data obtained in fluent solver.

使用FLUENT软件进行启动/刹车过程中燃油晃动的模拟,根据试验取得的油箱加速度数据制定了模型中液相的加速度值,并通过UDF中的DEFINE_SOURCE函数实现了液相加速度随时间的变化。DEFINE_SOURCE函数包含c,t,ds和i四个参数,其中c表示网格,t表示网格线,ds表示源项对所求运输方程的标量的偏导数,用于对源项的线性化,i表示所定义源项对应于整个输运方程。

Using FLUENT software start / brake process of fuel sloshing simulation. According to the test results of tank acceleration data formulated the value of the acceleration of the liquid phase in the model, and through the UDF define source function to achieve the liquid phase acceleration with the change of time.DEFINE_SOURCE source function contains C, t, DS and I four parameters, where C said grid, t denotes the grid lines, DS said source term for the partial derivatives of the scalar transport equation for the source term linearization I defined source term corresponds to the transport equation.

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