AEDC的航空推进试验设备和试验能力(下)

计算流体力学（ＣＦＤ）ＡＥＤＣ采用ＣＦＤ可分析进气道管道内的流场、试验舱内的冷却空气以及试验舱内燃气的排气收集。ＣＦＤ的其他应用还包括试验件在自由射流流场中的摆放，以使对气流最关键点，即进气道唇口的模拟最佳化。ＡＥＤＣ还成功地将ＣＦＤ用来分析气流从发动机矢量喷管进入排气收集器的流场。近３０年来，用来分析与试验有关流场的ＣＦＤ能力得到不断的提高，并与现有计算机的计算能力提高密切相关。试验数据的管理缩短研制周期最重要的是推进和试验工程师需要掌握现有信息，以便及时做出决定。近来ＡＥＤＣ在３个方面有明显…     

开放式气动力数值模拟系统研究

气动力数值模拟系统是ＣＦＤ流场解算技术、网格生成技术、数据可视化技术和网络技术相结合的产物。描述了一种运行于计算机网格环境下多任务、多用户、交互式的数值模拟软件环境－ 气动力数值模拟系统,该环境能计算模拟亚、跨、超音速绕流的气动力,也能方便地集成模拟不同复杂气动布局飞机流场的解算程序。介绍了其网格生成、数据可视化、系统接口等核心部分的结构和功能。     

变比热容对喷管流场和性能影响的计算

从变比热容角度出发,采用ＣＦＤ方法计算了发动机加力工作时高温状态下喷管内部流场分布和性能,并和定比热容计算结果进行了比较。结果表明,采用ＣＦＤ方法计算加力工作时喷管内部流场和性能,应该考虑变比热容的影响。     

气氢液氧同轴式单喷嘴燃烧室热态流场计算

建立了欧拉－拉格朗日坐标系下液体火箭发动机内部工作过程二维轴对称两相湍流化学反应流的完全Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ模型。应用该模型对气氢液氧同轴式单喷嘴燃烧室热态流场进行了数值模拟，得到了全流场的速度矢量分布、燃气组分等值线、流场等温线、流场等压线和流场等马赫线。计算是在任意斜交曲线坐标系下进行的，采用等参数正变换（代数变换）把物理平面上不规则计算域变换成了计算平面上的矩形域，控制方程也进行了相应的变换。计算结果表明，用计算流体力学（ＣＦＤ）的方法研究和分析液体火箭发动机内部工作过程是可行的。     

CIMS环境下CAPP系统的开发

介绍了ＣＩＭＳ环境下一个实用ＣＡＰＰ系统──ＦＡ—ＣＡＰＰ的主要功能，着重论述ＦＡ—ＣＡＤ／ＣＡＰＰ／ＣＡＭ的集成，ＦＡ—ＣＡＰＰ与ＣＩＭＳ其它分系统的集成，以及工艺知识表达、工序图生成。     

亚跨超CFD软件平台研制

亚跨ＣＦＤ软件平台研制的宗旨是综合国内外计算流体动力学的最新研究成果，用计算机软件技术的新发展，建立一个面向对象的计算流体动力学的研究开发环境，加快计算流体动力学最新成果向工程应用的转换速度。本文介绍初级版本的研究进展和研究成果，主要匝数值网格生成技术，流场解算器，面向对象的界面设计等三部分组成。     

SFD方法模拟高超声速进气道中激波与边界层干扰

采用ＳＦＤ方法,在ＥＸＣＥＬ软件上利用ＮＮＤ格式数值模拟了激波与平板边界层之间的相互作用以及激波与管道壁面边界层的相互作用,即高超声速进气道隔离段内激波串流动现象。该方法的特点是简单、直观而且不用常规编程,计算结果基本反映了流场的基本结构,表明ＳＦＤ方法是一种具有潜力的计算方法。     

二维旋转湍流边界层内气固两相流动的数值模拟

本文用修正的ＤＯＲＯＤ－ＦＥＭ方法对不可压流体二维旋转湍流边界层进行了数值模拟，得到了与实验数据较符合的边界层形状因子和壁面摩擦系数的计算结果。采用单向耦合（Ｏｎｅ－ｗａｙ Ｃｏｕｐｌｉｎｇ）方法，计算了固粒在湍流边界层和无粘流中的运动轨迹，给出了壁面被固粒撞击后的冲蚀磨损分布，分析了近壁流场性态与壁面冲蚀磨损的关系。     

气液同轴离心式喷嘴喷雾流场数值模拟

采用计算流体动力学（ＣＦＤ）方法对气液同轴离心式喷嘴冷态液雾两相流场进行了数值模拟，并且与试验结果进行了比较。为了比较，计算中采用的入口边界条件和液滴质量平均直径（ＭＭＤ）及其分布规律都是由试验确定的。研究了气液喷注压降对喷雾流动过程和流强分布的影响规律。结果表明，数值模型和计算程序能较好地模拟气液同轴离心式喷嘴两相喷雾流动过程，喷雾的存在对流场流型有很大的影响。     

船舶与海洋工程计算流体力学的研究进展与应用

本文着重介绍了中国航船科学研究中心在ＣＦＤ方面所具备的能力,内容有：粘性流中水面舰船尾流场计算;实船雷诺数１０＾９量阶的舰船尾流场和水动力性能的数值预报;实效伴流场－船体与螺旋浆相互作用的数值预报;     

与飞机融合的单边膨胀喷管排气系统

单边膨胀喷管（Single Expansion Ramp Nozzle,SERN）是1种新型的排气喷管,具有可以有效抑制航空发动机排气系统的红外辐射和雷达反射截面积、后体阻力小、质量轻、增加飞机的敏捷性和可操控性等优点。运用计算流体力学/红外辐射（CFD/IR）数值模拟的方法,采用标准k-ε湍流模型和标准壁面函数,研究了轴对称喷管、单边膨胀喷管和开缝冷却单边膨胀喷管的排气系统与机身融合后的红外辐射特性空间分布规律。结果表明：单边膨胀喷管大幅度降低了排气系统尾向红外辐射峰值,其降幅达到60%以上,说明了单边膨胀喷管与后机身融合、遮挡内部高温部件,从而降低了尾向红外辐射的卓越红外抑制效果。     

二元收-扩喷管与球形收敛调节片喷管的性能对比研究

为了对比二元收-扩喷管(2DCD)与球形收敛调节片喷管(SCFN)的性能,基于CFD数值计算软件对2种喷管在相同工作点下进行了内外流场计算与分析。数值模拟结果表明:在相同高度及飞行马赫数条件下,SCFN的流量系数相较于2DCD呈现出较大不同,推力系数则略差于2DCD;在低落压比条件下,2种喷管内流对后体阻力特性影响不大;在高落压比条件下,2种喷管内流对后体阻力特性影响较大。     

基于单缝射流的二元推力矢量喷管设计及数值模拟

喷管是发动机产生推力的主要部件,其气动性能对发动机的性能具有决定性的影响。本文利用简化特征线法设计二元收敛-扩张（2DCD）推力矢量喷管模型;采用RNGk-ε湍流模型和非平衡壁面函数对单缝二次流喷射后的喷管流场进行数值模拟,分析了射流位置、主流落压比（NPR）、二次流与主流总压比（SPR）等参数对矢量喷管气动性能的影响...     

Vector deflection stability control of aero-engine based on linear active disturbance rejection

Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle (AVEN), a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control (LADRC) is proposed. Firstly, based on CFD numerical simulation, aerodynamic performance model of AVEN is established, and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed. Subsequently, the integrated model of AVEN/turbofan engine is established by Simulink/AMESim co-simulation. Finally, the nozzle throat area control loop based on LADRC is designed. The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system. The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%, indicating a high degree of confidence. Compared with the conventional PID control, the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%, which effectively improves the control stability of the vector deflection. Meanwhile, the fuel flow ratechange during the vector deflection process is smaller and more economical, which provides an important reference for engineering applications.     

Numerical analysis for impacts of nozzle end-clearances on aerodynamic performance and forced response in a VNT turbine

It has been well known that nozzle end-clearances in a Variable Nozzle Turbine (VNT) are unfavorable for aerodynamic performance, especially at small openings, and efforts to further decrease size of the clearances are very hard due to thermal expansion. In this paper, both the different sizes of nozzle end-clearances and the various ratios of their distribution at the hub and shroud sides were modelled and investigated by performing 3D Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) simulations with a code of transferring the aerodynamic pressure from the CFD results to the FEA calculations. It was found that increasing the size of the nozzle end-clearances divided equally at the hub and shroud sides deteriorates turbine efficiency and turbine wheel reliability, yet increases turbine flow capacity. And, when the total nozzle end-clearances remain the same, varying nozzle end-clearances’ distribution at the hub and shroud sides not only shifts operation point of a VNT turbine, but also affects the turbine wheel vibration stress. Compared with nozzle hub clearance, the shroud clearance is more sensitive to both aerodynamic performance and reliability of a VNT turbine. Consequently, a possibility is put forward to improve VNT turbine efficiency meanwhile decrease vibration stress by optimizing nozzle end-clearances’ distribution.     

一种三组元直排塞式喷管发动机系统方案

三组元发动机和塞式喷管发动机均是实现单级入轨的关键技术。针对三组元(液氢、液氧、煤油)直排塞式喷管发动机提出了一套系统结构方案，并对其进行了初步的研究计算。发动机采用泵压式燃气发生器动力循环系统。利用蝶形活门关闭煤油管路、利用可调气蚀管调节氢氧流量转变工况，利用可调气蚀文氏管和涡轮排气进行推力矢量控制。以已有的三组元塞式喷管发动机推力室设计、分析为基础，继承了三组元发动机和塞式喷管的研制成果，是技术先进、性能高、可在短期内实现的新型液体火箭发动机。     

Progress and future prospects of CFD in aerospace—Wind tunnel and beyond

A historical perspective of computational fluid dynamics (CFD) in aerospace in the last 30 years is firstly given. It is shown that there still remain a number of problems that are geometrically simple but difficult to simulate even after many simulations were conducted over complex body configurations. The fact indicates that CFD research is now in the “specific phase” and requires some innovation.The innovation includes “evolutionary effort” and “revolutionary effort”. As an example of evolutionary effort, large eddy simulations/ Reynolds-averaged Navier–Stokes simulations (LES/RANS) hybrid method and its application examples are presented. A shift from RANS to LES/RANS hybrid method occurs not because of the advancement of computers but because of our recognition that separated flows are inherently unsteady and successful simulations require LES-like computations.Comment is given that there may be other types of research necessary to make CFD a real useful tool for a design in addition to simply showing CFD capability for complex body configurations. As one of the examples, construction of a CFD database is presented. Another issue is to make CFD infrastructures so that people outside CFD community may use CFD as a tool to formulate or refine their ideas.To find out revolutionary effort, the message given by Prof. Dean Chapman in 1977 is referred. Observation of current CFD research reveals that evaluation methods of “scale effect” that were believed to be the most important benefit of CFD have not yet been established. Such establishment is the key for the revolution of CFD and researchers need to focus their effort on the development of technologies to evaluate scale effect. Only with such new CFD technologies can “conceptual design with CFD” become feasible.     

直升机旋翼桨-涡干扰状态非定常气弹载荷高精度预估

为准确计算直升机旋翼在复杂的桨-涡干扰(BVI)状态下的气弹载荷,在刚性旋翼计算流体力学方法中引入桨叶弹性变形的影响,建立了一套适合于弹性旋翼BVI状态气动特性分析的计算流体力学/计算结构力学(CFD/CSD)耦合方法.CFD模块对Reynolds averaged Navier-Stokes(RANS)/Euler方程进行求解,并采用双时间法推进和Baldwin-Lomax(B-L)湍流模型.CSD模块采用中等变形梁假设的有限元模型,通过Newmark-Beta方法求解桨叶运动方程.通过代数变换方法进行桨叶网格变形,并建立一个适于流场/结构信息交换的CFD/CSD耦合方法.在分别验证CFD和CSD模块的有效性的基础上,开展UH-60A直升机旋翼的BVI 状态载荷分析,并与飞行测试数据进行了对比.计算结果表明:相比于旋翼综合分析中的升力线理论和刚性旋翼CFD方法,耦合的CFD/CSD方法可以更准确地预测BVI状态气弹载荷,并有效地模拟桨叶前行侧方位角和后行侧方位角附近的BVI现象,对BVI导致的升力波动幅值和相位的计算结果均与试验值吻合良好.      

Experimental Investigation of Nozzle Effects on Thrust and Inlet Pressure of an Air-breathing Pulse Detonation Engine

Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine (APDE) are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle. Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.     

旋翼VPM/CFD耦合模型的建立及其在小前进比气动分析中的应用

为了提高旋翼计算流体力学（CFD）流场计算效率及克服其在尾迹捕捉上的不足,将旋翼黏性涡粒子方法（VPM）与CFD分析相结合,建立了一个新的旋翼VPM/CFD耦合气动分析模型。在该模型中,采用VPM分析以实现对旋翼尾迹中黏性涡的高效捕捉而不引入数值耗散,而采用CFD分析用于精确地模拟旋翼桨叶近体区域内复杂的流动现象,同时也为VPM分析提供一个较高精度的涡源模型。至于两者信息交换,则使用集中涡源法将CFD信息传递至VPM分析,而VPM计算得到的尾迹信息则通过边界修正施加至CFD域的远场边界上,从而可以鲁棒地实现CFD域与VPM域的耦合计算。在此基础上,对“Helishape 7A旋翼”小前进比前飞桨-涡干扰（BVI）状态进行了较为深入的气动分析,计算结果表明：与全CFD计算比较,建立的VPM/CFD耦合分析模型可以有效地避免旋翼尾迹区桨尖涡的数值耗散,从而更加可靠地捕捉桨-涡干扰状态下的桨叶非定常气动载荷脉动,同时对于本文算例,计算效率可以提高30%以上。