﻿ 基于欧拉壁面液膜模型的三维热气防冰腔数值仿真<sup>*</sup>
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Numerical simulation of 3D hot-air anti-icing chamber based on Eulerian wall film model
LI Yan, GUO Tao, CHANG Hongliang
The First Aircraft Institute, Aviation Industry Corporation of China, Xi'an 710089, China
Received: 2017-05-31; Accepted: 2017-08-11; Published online: 2017-10-13 14:05
Corresponding author. LI Yan, E-mail:276637284@qq.com
Abstract: A new computation method of hot-air anti-icing chamber performance based on Eulerian wall film (EWF) model was presented in this paper. User defined scalar (UDS) of FLUENT software was used to calculate water droplet impingement efficiency by solving droplet governing equation. Mass balance analysis of water collection rate and film evaporation rate was performed to get the mass flow rate of each micro unit, which was used as boundary condition in calculating 3D film thickness distribution driven by air, and then the dynamic model of film flow on anti-icing surface was set up. Based on the above work, conjugate heat transfer model for 3D anti-icing surface was built, and under-relaxation factor was used in solving the loose coupling of inner/outer flow field, water film flow and skin heat conduction. The method of this paper was used in the calculation of a nacelle anti-icing chamber performance, and the results show good compliance with the physical phenomenon. The method in this paper can be used in 3D hot-air anti-icing chamber performance calculation.
Key words: Eulerian wall film (EWF) model     hot-air anti-icing     loose couple     anti-icing heat load     water film     numerical simulation     three-dimensional

1 数学模型 1.1 内外空气流场及蒙皮导热计算

1.2 水滴撞击特性的计算

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 (5)

 (6)

 (7)

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1.3 EWF模型及防冰表面热载荷的计算

1.3.1 EWF模型

 图 1 防冰表面水的流动 Fig. 1 Water flow on anti-icing surface

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1.3.2 防冰表面热载荷的计算

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e(T)的计算式为[18]

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1.4 耦合换热模型的建立

1.4.1 水膜流动过程中的热载荷计算

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1) 获取当前微元的水膜厚度和微元面积，计算得到当前微元上水膜的质量为

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2) 根据水滴收集特性计算结果，计算当前时间步长Δt内微元收集的水量为

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3) 计算当前微元在时间步长内的理论蒸发量Mevap

4) 计算微元的质量源流量：

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5) 若Msource < 0, 则进一步比较|Msource|和Mf的大小：

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6) 计算得到质量源流量后，进一步根据1.3.2节的方法计算每个微元的等效对流换热系数，并设置用户自定义存储(UDM)将等效对流换热系数存储在计算文件中。

7) 计算CFL数，并将其与前一步长的CFL数进行对比，当残差小于设定值时，即可认为水膜流动达到了稳定状态，以此时计算得到的等效对流换热系数作为防冰表面热载荷的计算结果，将其作为内流场和蒙皮导热计算的边界条件。

1.4.2 界面数据的交换

1.4.3 耦合收敛的控制

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2 算例分析 2.1 计算模型和计算状态

 图 2 短舱几何外形及其防护区域 Fig. 2 Nacelle's geometric shape and protection area
 图 3 短舱防冰腔 Fig. 3 Nacelle anti-icing chamber

 参数 马赫数 环境压力/Pa 环境温度/℃ 水滴直径/μm 液态水含量/(g·m-3) 供气压力/kPa 供气温度/℃ 数值 0.3 70 124 -9.4 20 0.5 350 150

2.2 水滴撞击特性

 图 4 水滴局部收集系数计算结果的对比 Fig. 4 Comparison of water droplet local collection coefficient

2.3 水膜流动的动态过程

 图 5 不同时刻的水膜厚度分布 Fig. 5 Water film thickness distribution at different time

 图 6 防护区域外的水膜厚度分布 Fig. 6 Water film thickness distribution in non-protection area
2.4 防冰表面温度及热载荷

 图 7 加热区域蒙皮表面温度分布对比 Fig. 7 Comparison of skin temperature distribution of heated area
 图 8 不同截面蒙皮表面温度分布对比 Fig. 8 Comparison of skin temperature distribution on different sections

 图 9 等效对流换热系数分布 Fig. 9 Distribution of equivalent convective heat transfer coefficient
3 结论

1) 基于UDS的水滴撞击特性计算方法的计算结果与FENSAP-ICE软件计算结果基本相同，可满足三维表面水滴撞击特性的计算。

2) 提出了基于EWF模型结合UDF自定义质量流量边界条件求解水膜在防冰表面的动态流动过程方法，实现了三维水膜的流动及传热计算，结果真实可信。

3) 建立了适应于三维外形的防冰性能换热计算模型，并通过算例计算得到了某民机发动机短舱防冰系统在典型外部环境和供气参数下的三维防冰表面温度、防冰表面水膜厚度分布以及表征防冰热载荷的等效对流换热系数。通过对算例计算结果的分析和对比可知，本文提出的基于EWF模型的热气防冰腔性能仿真计算方法是切实有效的，其计算结果也是合理可信的。

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文章信息

LI Yan, GUO Tao, CHANG Hongliang

Numerical simulation of 3D hot-air anti-icing chamber based on Eulerian wall film model

Journal of Beijing University of Aeronautics and Astronsutics, 2018, 44(5): 959-966
http://dx.doi.org/10.13700/j.bh.1001-5965.2017.0362