Experimental and numerical study on pressure oscillation in a combustor with rotary valve

A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine. This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model. A 3D numerical model is proposed to obtain the transient flow inside the rotary valve, and the dynamic mesh technique and User-Defined Functions (UDFs) are adopted to implement a swing motion instead of a rotary motion. Several cold gas flow experiments are carried out at rotating speeds of 75 225, and 375 rpm to verify the validity of the numerical model. The effects of rotating speed, stroke length ratio and radius of the RED (Rotor Exhaust Duct) on the pressure oscillations are studied using this numerical model. The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed. The ratio of the corresponding peak-to-peak value to the maximum pressure (pressure amplitude ratio) is reduced from 1.81 to 0.6%. The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage. When the stroke length ratio is 0, the waveform closely resembles a sine wave. With the increase in the stroke length ratio, the pressure waveform exhibits a more square or a triangular wave shape. Finally, a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED.     

CT5ATP在GTCP131-9BAPU管理中的作用

针对波音737NG机型GTCP131—9B辅助动力装置（APU）出现涡轮叶片移位的故障,分析了叶片移位对APU的影响,提出7CT5ATP方法．并结合南航的经验将其应用于GTCP131—9BAPU的管理中．确定了以CT5ATP作为启动值,结合修后使用时间（TSR）、孔探结论和后中心体盖裂纹检查作为完整性能监控的手段,为APU拆换提供了可信的实践依据,实现7APU单位维修成本的有效降低。     

飞机轮胎自动充气与检测装置的研制

为了减轻飞机轮胎的充气与检测工作量，提高工作效率，增加操作时的安全性．研制了一种飞机轮胎自动充气与检测装置。试验结果表明，该装置性能可靠、工作安全、使用范围宽、使用效率高，具有国内领先水平。     

{MC COMMENT: PA CORRECTION}Theoretical study of ullage washing with mixed inert gas in a non-equilibrium state

The Mixed Inert Gas (MIG) produced by the novel Green OnBoard Inerting Gas Generation System (GOBIGGS) mainly consists of carbon dioxide, nitrogen and oxygen. Because of the large solubility of carbon dioxide in jet fuel compared with nitrogen, the no gas release or equilibrium model could not be employed any more. In this paper, first, a mathematical model of the ullage washing was set up to predict the variation of the oxygen concentration on ullage and in the fuel, and the gas evolution and dissolution rate were calculated by Fick’s second law. Then, an experimental apparatus was constructed to verify the accuracy of the model. Finally, the numerical comparisons of ullage washing using Nitrogen Enriched Air (NEA) and MIG are presented under various flow rates and fuel loads, and the result reveals that the variation of the oxygen concentration on ullage is nearly identical whatever the inert gas is NEA or MIG. However, the variation of the oxygen concentration in the fuel is disparate, and the oxygen concentration decreases rapidly if the inert gas is MIG, especially when the fuel load is low or the flow rate of the inert gas is high. Besides, MIG could suppress the rising trend of the oxygen concentration on ullage when the aircraft ascends if the fuel tank is fully washed into an equilibrium state on ground.     

高压气体压力现场校准方法研究

针对高压气体压力仪表现场校准的具体要求，提出高压气体压力现场校准方法。介绍了目前国内外高压气体压力现场校准领域内的研究现状及校准用标准器的技术要求，现场应具备的环境条件，校准项目，校准点的选取。本校准方法在被校准压力仪表的使用范围内校准，不需要拆卸压力仪表，大大便利了现场高压气体压力仪表的校准，对高压气体压力仪表现场校准测量不确定度进行评定及验证。     

大型飞机气源起动装备供气流程设计与计算

为了研发具有自主知识产权的气源起动装备,立足于大型飞机较高压力、超大流量的特殊气源起动保障需求,设计了以双级无油螺杆压缩为核心技术的供气流程,对其中涉及的级间压力、散热量、除水量等关键参数进行了分析与计算,为解决超大流量气源的二次升压、风冷散热、高温除水等核心技术难题奠定了基础。     

燃气轮机刷丝与平衡盘碰摩的振动故障诊断

针对某型航改燃气轮机压气机机匣振动超限故障,通过时频和振动幅值趋势分析,结合分解检查结果进行了试验验证,发现平衡盘端面与刷环刷丝之间发生碰摩为根本原因,碰摩形式与传统涡轮叶尖与外环块之间的碰摩形式截然不同。通过定性分析发现,激振力主要通过低压涡轮输出轴传递,且因受№1支点的"杠杆"作用,对振动响应进行了放大;碰摩产生的激振力大小主要与引气量和二者间隙相关,刷环刷丝的表面刚性是随引气量变化的变刚度过程,分析了在燃气轮机动力涡轮转速稳定后,压气机动力涡轮基频幅值随燃气发生器转速提高而继续增大的原因,最后得到力学模型和运动方程。     

某型燃气轮机进气系统内流场的数值分析

为了揭示燃机进气系统内的流动特性,并为进气系统的性能预测、优化设计提供理论依据,以某型燃气轮机的进气系统为研究对象,基于混合网格的SIMPLE算法和标准的k-ε湍流模型,运用FLUENT软件对燃气轮机进气系统内的流场进行数值模拟,并从压力分布、气流角分布2个方面进行分析。结果表明:对气动性能产生重要影响的损失区域主要集中在进气外环上方和支板附近,蜗壳内锥的绕流分离也是损失源之一。应进行尽可能消除进气外环上方的气流分离,同时将绕流分离控制在一定范围内的优化设计和改进。     

民用发动机状态混沌预测算法

首先应用Haar小波和DB16小波对航空发动机排气温度的原始数据序列进行去噪处理,并且证明了处理后的数据序列具有混沌特征.其次应用混沌理论建立发动机状态预测算法,实现对排气温度的预测.通过检验排气温度预测值是否超过所规定的红线,以及该曲线是否平稳,从而进行发动机的健康状态排查.作为验证实例,使用一组某机型发动机实际飞行...     

中热值合成气扩散燃烧速度特性的实验研究

针对CH4和中热值合成气的旋流燃烧室进行了PIV测量,获得了不同燃料燃烧对火焰流场变化的影响。实验结果表明：在相同入口条件下,合成气燃烧时的火焰张角略大,回流区宽度和回流强度均高于CH4火焰,燃气流量较低时,合成气火焰的湍流强度更大,燃气流量增大后,CH4的燃烧脉动速度逐渐增大并超过合成气。