汽車油箱燃油晃動CFD模擬分析

2016-08-31 by:CAE仿真在線來源:互聯網

汽車燃油系統是汽車至關重要的部件之一,它關系到每個乘客的生命安全。在剎車和啟動過程中,燃油對油箱壁撞擊所產生的壓力影響到整個燃油系統的穩定性,壓力變化引起的振動噪聲也是衡量整車舒適性的重要指標之一。因此,燃油晃動一直是燃油系統開發過程中需要研究的重點和難點問題。使用Fluent軟件運用VOF方法對汽車燃油箱進行了汽車加速/剎車過程中的燃油晃動模擬,可以得到燃油晃動過程中油箱壁的壓力分布和壓力變化,為燃油系統的開發和優化提供了指導和理論依據。

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

所謂VOF模型是一種在固定的歐拉網格下的表面跟蹤方法。當需要得到一種或多種互不相融流體間的交界面時,可以采用這種模型。在VOF模型中,不同的流體組分共用著一套動量方程,計算時在全流場的每個計算單元內,都記錄下各流體組分所占有的體積率。VOF模型的應用例子包括分層流,自由面流動,灌注,晃動,液體中大氣泡的流動,水壩決堤時的水流,對噴射衰竭(jet breakup)(表面張力)的預測,以及求得任意液-氣分界面的穩態或瞬時分界面。

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軟件進行啟動/剎車過程中燃油晃動的模擬,需要將空氣設置為多相流的主項,燃油設置為多相流的次相進行計算。

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.

用戶自定義函數UDF

User defined function UDF

UDF(用戶自定義程序)是FLUENT提供的用戶編程環境,以解決標準FLUENT本身不能解決的問題。用戶自定義函數用C語言編寫,使用DEFINE宏來定義。UDF中可使用標準C語言的庫函數,也可使用Fluent提供的預定義宏,通過這些預定義宏,可以獲得Fluent求解器得到的數據。

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軟件進行啟動/剎車過程中燃油晃動的模擬,根據試驗取得的油箱加速度數據制定了模型中液相的加速度值,并通過UDF中的DEFINE_SOURCE函數實現了液相加速度隨時間的變化。DEFINE_SOURCE函數包含c,t,ds和i四個參數,其中c表示網格,t表示網格線,ds表示源項對所求運輸方程的標量的偏導數,用于對源項的線性化,i表示所定義源項對應于整個輸運方程。

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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