﻿ 发动机短舱泄压过程瞬态仿真<sup>*</sup>
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1. 南京航空航天大学 航空学院 飞行器环境控制与生命保障工业和信息化部重点实验室, 南京 210016;
2. 中国航空发动机集团 商用航空发动机有限责任公司, 上海 200241

Transient simulation on pressure relief process of engine nacelle
WANG Chenchen1, FENG Shiyu1, PENG Xiaotian1, DENG Yang2, CHEN Jun2
1. Key Laboratory of Aircraft Environment Control and Life Support of Ministry of Industry and Information Technology, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;
2. Commercial Aircraft Engine Co., Ltd., Aero Engine Corporation of China, Shanghai 200241, China
Received: 2019-03-04; Accepted: 2019-03-29; Published online: 2019-05-08 09:23
Foundation item: National Natural Science Foundation of China (U1933121); the Fundamental Research Funds for the Central Universities (kfjj20180108); the Priority Academic Program Development of Jiangsu Higher Education Institutions
Corresponding author. FENG Shiyu. E-mail:shiyuf@nuaa.edu.cn
Abstract: The design of the engine nacelle pressure relief door will affect the safety of the nacelle. The pressure relief is a dynamic process, which is related to the pressure inside and outside the nacelle, the freestream Mach number and the structure of the pressure relief door. Based on the Modelica language, a zero-dimensional transient simulation mathematical model of the nacelle pressure relief process was established, and the pressure relief door (PRD) discharge and moment coefficient under different opening angles were calculated via computational fluid dynamics (CFD). Then those coefficients were substituted into the zero-dimensional transient simulation model, and the variation relationship of key parameters such as the plenum compartment pressure and opening angle of the PRD with time during the pressure relief process is obtained. The influence of the plenum compartment pressure threshold and the maximum opening angle of the PRD on the pressure relief process was analyzed. The study results show that reducing the plenum compartment pressure threshold for PRD opening will reduce the time required for the pressure relief process reaching to the equilibrium stage, but has no effect on the plenum compartment pressure and reciprocating swing angle/amplitude at equilibrium stage; properly reducing the maximum opening angle can effectively reduce the PRD reciprocating swing angle/amplitude in the equilibrium stage, and has no effect on the pressure relief rate in the initial stage and the plenum compartment pressure in the equilibrium stage, but excessive reduction of the maximum opening angle will decrease the pressure relief rate in the initial stage and increase plenum compartment pressure in the equilibrium stage.
Keywords: engine nacelle     pressure relief process     transient model     pressure relief door     computational fluid dynamics (CFD)

Pratt等[3-4]为了分析挡板对流场结构的影响，使用Vick[2]报告中的试验装置作为计算域进行了CFD计算，结果与试验数据基本吻合。随后，Benard等[5]对压力比大于1的泄压门排放特性进行了试验研究，结果表明在给定压力比下，排放系数随马赫数的增加而减小。Vedeshkin等[6]研究了一种与前述不同的开启方式，即泄压门铰链与来流方向平行，CFD计算和试验之间存在很好的一致性。Schott[7]考虑了泄压门纵横比、倒圆角、铰链类型、侧壁边缘围护等因素的影响，在一系列压力比、马赫数、内部温度、外界高度等条件下对短舱核心舱泄压门的排放性能和受力进行了CFD计算，得到许多对泄压门设计具有指导作用的结论。

Modelica语言是为解决多领域物理系统的统一建模与协同仿真，在归纳和统一先前多种建模语言的基础上，于1997年提出的一种基于方程的陈述式、面向对象的、非因果建模语言[10-11]。Modelica语言采用数学方程描述不同领域子系统的物理规律和现象，根据物理系统的拓扑结构基于语言内在的组件连接机制实现模型构成和多领域集成，通过求解微分代数方程系统实现仿真运行。Modelica语言已广泛应用于各个学科，如航空航天、电力系统、汽车系统、燃料电池等领域[12-17]。因此，本文采用Modelica语言建立仿真模型，并对模型进行求解。

1 短舱泄压过程零维瞬态仿真数学模型 1.1 泄压过程简化和基本假设

 图 1 短舱泄压过程示意图 Fig. 1 Schematic diagram of nacelle pressure relief process
1.2 零维瞬态仿真数学模型

 (1)

p1/p0πp, cr时，流动为非临界状态，此时高压引气管路泄漏质量流量为

 (2)

p1/p0 < πp, cr时，流动为临界状态，此时高压引气管路泄漏质量流量为

 (3)

p2/p1πp, cr时，流动为非临界状态，此时泄压门排放质量流量为

 (4)

p2/p1 < πp, cr时，流动为临界状态，此时泄压门排放质量流量为

 (5)

 (6)

 (7)

 (8)

 (9)

 (10)

2 CFD稳态仿真计算 2.1 几何模型及网格生成

 图 2 泄压门外形和结构示意图 Fig. 2 Schematic diagram of PRD shape and structure
 图 3 泄压门几何模型 Fig. 3 Geometry model of PRD
 图 4 网格划分 Fig. 4 Mesh generation
2.2 计算条件及边界条件

2.3 CFD计算验证

 图 5 计算结果与试验数据对比 Fig. 5 Comparison of calculation and test data
 图 6 计算结果与试验数据误差分析 Fig. 6 Error analysis of calculation and test data

 (11)

 (12)

2.4 CFD稳态仿真计算结果

 图 7 排放质量流量随开启角度和舱内压力的变化 Fig. 7 Discharge mass flow rate varies with opening angle and plenum compartment pressure
 图 8 流量系数随开启角度和舱内压力的变化 Fig. 8 Discharge coefficient varies with opening angle and plenum compartment pressure
 图 9 力矩随开启角度和舱内压力的变化 Fig. 9 Moment varies with opening angle and plenum compartment pressure
3 短舱泄压过程瞬态计算结果

3.1 泄压门开启阈值对泄压过程的影响

 图 10 不同开启阈值下舱内压力变化对比 Fig. 10 Comparison of plenum compartment pressure changes under different opening thresholds
 图 11 不同开启阈值下开启角度变化对比 Fig. 11 Comparison of opening angle changes under different opening thresholds

3.2 泄压门最大开启角度对泄压过程的影响

 图 12 不同最大开启角度下舱内压力变化对比 Fig. 12 Comparison of plenum compartment pressure changes under different maximum opening angles
 图 13 不同最大开启角度下开启角度变化对比 Fig. 13 Comparison of PRD opening angle changes under different maximum opening angles

4 结论

1) 所建立的零维瞬态仿真数学模型可有效分析泄压时舱内压力及泄压门开启角度随时间变化关系，高压引气管路泄漏会使短舱内部压力迅速升高，而泄压门泄压过程可降低舱内压力从而避免破坏短舱结构。

2) 泄压初始阶段，舱内压力较高，此时泄压门力矩平衡角很大，因此泄压门达到最大开启角度；而随着泄压过程的进行，舱内压力逐渐降低并趋于某一值附近，当泄压门力矩平衡角低于最大开启角度时，泄压门会在平衡角附近往复摆动，舱内压力也会出现微小波动。

3) 降低泄压门开启舱内压力阈值，会影响泄压初始阶段舱内压力变化，使泄压过程到达平衡状态所需时间减小，但对平衡阶段基本无影响。

4) 适当降低泄压门最大开启角度，可有效减小泄压门平衡阶段往复摆动角度，且对泄压初始阶段泄压速率及平衡阶段舱内压力影响很小；而过多地降低最大开启角度导致最大开启角度低于泄压平衡角时，会大大降低泄压速率，且会提高平衡阶段舱内压力。

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文章信息

WANG Chenchen, FENG Shiyu, PENG Xiaotian, DENG Yang, CHEN Jun

Transient simulation on pressure relief process of engine nacelle

Journal of Beijing University of Aeronautics and Astronsutics, 2019, 45(11): 2284-2290
http://dx.doi.org/10.13700/j.bh.1001-5965.2019.0081