A model-scale test on noise from single-stream nozzle exhaust geometries in static conditions

A model-scale test with single-stream nozzle exhaust geometries was carried out at the anechoic chamber of Beihang University in Beijing, China. The spectral characteristics are investigated, and the effects of the following parametric variations are reported in this paper: impact of nozzle operating conditions on spectra; impact of the presence of a plug; and effectiveness of chevron configurations for noise mitigation. The measurement shows that the change of pressure values has more impact on spectra than the change of temperature values. The spectral change due to pressure is shown at all band numbers for unheated conditions whereas it is more pronounced at high-frequency ranges for heated conditions. An impact of the presence of a plug is also clearly observed. The reduction of noise is moderate up to band number of 35, and becomes more significant at higher band numbers. It is observed that chevron nozzles are more efficient at high pressure and temperature values. It is expected that the quantified analysis will be used to develop an empirical model of single jet noise, which will be the baseline for the development of prediction of noise from turbofan engines of high bypass ratios.     

超音速流动中侧向喷流干扰特性的数值模拟

通过与实验结果的比较验证Fluent软件可以用于超音速流动中侧向喷流干扰特性数值研究.使用Fluent软件对超音速流动中不同喷流压力和攻角下侧向喷流干扰特性进行的数值研究表明,超音速流动中,随喷流压力和负攻角增大,喷流前的高压区明显增大,喷流的控制效果更好.喷流包裹作用的影响范围在90°弹面内.喷流压力增大,喷流包裹作用加强,影响范围增大.     

固体火箭发动机成本与性能双目标优化设计

为求解某运载火箭上面级固体推进剂火箭发动机多属性价值优化问题,建立了发动机主要部件的参数成本模型,研究了一种改进的Pareto多目标遗传算法--IPGA算法,测试函数的计算结果表明,该算法收敛性优于NSGA-Ⅱ算法.以运载火箭末速度增量最大和发动机制造成本最低作为目标函数,采用IPGA计算得到了壳体材料分别为APMOC和碳纤维时的Pareto非劣解集,采用理想点法得到非劣解集中费效比变化的拐点,计算结果表明,以该点为满意解设计方案可以使该运载火箭的有效载荷提高7.6%,并使发动机的成本降低.     

设备构件对射流开孔性能的影响

通过对设备构件的结构布局和射流毁伤特性的详细分析,得到2种设备构件的模拟结构,并开展了对射流开孔性能影响的试验。试验结果表明,采用均匀平板模拟的方式能够较准确地模拟设备构件对射流的影响。研究结果对破甲弹的设计具有较好的参考意义。     

基于燃气射流冷凝的氧路系统频率特性研究

基于热力学不平衡两流体六方程模型模拟了液氧煤油补燃循环发动机燃气射流在氧路系统泵间管路液氧流体中的冷凝过程，获得了燃气射流冷凝特征参数沿管路流向的分布规律。根据Rayleigh-Plesset方程和燃气射流特性建立了泵间管路燃气冷凝过程的传递函数模型，并与氧路管路、泵等组件模型联立求解，分析了发动机氧路系统频率特性。研究了在不同氧路入口压力和液氧温度边界条件下，泵间管路燃气射流冷凝过程对氧路系统频率特性的影响，仿真结果表明高入口压力和过冷液氧改变了射流气体的惯性和柔度，使得氧路系统特征频率增大。不同边界条件下发动机热试车结果表明，提高氧路入口压力或降低液氧温度使得氧路系统频率从8.3 Hz提高至11 Hz，与数值仿真结果一致，验证了泵间管燃气射流冷凝过程是影响氧路系统频率特性的重要环节。     

航空发动机整体叶盘磨料水射流开坯加工技术研究进展

整体叶盘结构是航空发动机技术发展的一个重要方向，且多采用难加工材料，如何实现整体叶盘高质高效加工是机械制造领域亟待解决的难题之一。通过高压磨料水射流（AWJ）加工技术实现整体叶盘毛坯的开坯粗加工，是一种有效缩短整体叶盘加工周期、降低昂贵铣削刀具成本、提高开坯效率的工艺手段。本文就磨料水射流加工材料去除机理、复杂曲面轨迹优化、多物理量和机械量参数组合优化和整体叶盘开坯设备概述了国内外的研究现状，在此基础上，针对当前具有复杂曲面结构的整体叶盘开坯面临的关键问题，提出了若干解决思路和技术途径，指出了高压磨料水射流在复杂曲面零件高效加工中的发展趋势。     

航空发动机高温部件系统模拟技术

对航空发动机高温部件系统模拟技术进行研究,在涡轮等高温部件及其冷却系统组成的流固系统研究中采用整体域划分思路,并对两部分组成的整体域统一求解.将该方法在某模型中进行分析验证,应用到某涡轮系统及周围冷却空气模拟中,并对强弱耦合两种耦合模拟方法的结果进行了比较分析.     

超声速高温冲击射流注水流场实验研究

为了降低发动机羽流冲击流场的温度,减弱其对发射装置的冲击和烧蚀作用,对超声速高温冲击射流的注水流场开展了实验研究。通过高速摄影和红外热像仪两种非接触式测量设备对无注水和注水两种状态下的冲击流场进行了对比拍摄,并且使用热电偶对底板冲击区的温度进行了测量。对注水两相冲击流场的结构和温度场分布进行了深入分析和研究,并与无注水状态下流场进行对比,得出了通过注水方式可以减少核心区长度和面积,降低迎气面温度,减弱其热冲击烧蚀效应的结论。     

Numerical investigation of co-flow jet airfoil with parabolic flap

Both the Active Flow Control (AFC) and the variable-camber technology are considered as efficient ways to enhance the aerodynamic performance of an aircraft. The present study investigated the feasibility of the combination of a Co-Flow Jet (CFJ) airfoil and a parabolic flap, where the Reynolds Average Navier-Stokes (RANS) equations and the Spalart-Allmaras (S-A) turbulence model were exploited for the numerical simulation. Several significant geometric parameters, including the injection slot location, the suction slot location, the injection slot angle, the suction slot angle and the airfoil Suction Surface Translation (SST), were selected to study their effects on the aerodynamics of the proposed configuration. Then, an optimized design was created and compared with the baseline airfoil. The results show that the CFJ airfoil combined with the parabolic flap is more beneficial to the aerodynamic performance enhancement at small angles of attack. It is preferable to locate the injection slot at a 2% chord-wise location and the suction slot at a 75% chord-wise location. Both the decrease of the injection slot angle and the augmentation of the suction slot angle could reduce the drag. Furthermore, the SST of 0.5% chord is selected due to its high gain in the corrected aerodynamic efficiency at small angles of attack. Compared with the baseline, the optimized design could increase the lift coefficient and the corrected lift-to-drag ratio by 32.1% and 93.8% respectively at the angle of attack α = 4°.     

Adaptive modification of turbofan engine nonlinear model based on LSTM neural networks and hybrid optimization method

An accurate and reliable turbofan engine model which can describe its dynamic behavior within the full flight envelop and lifecycle plays a critical role in performance optimization, controller design and fault diagnosis. However, due to the performance differences caused by the tolerance of engine manufacturing and assembly, and performance degradation during continuously stringent environmental regulations, the model accuracy is severely reduced. In this paper, an adaptive modification method of turbofan engine nonlinear Component-Llevel Model (CLM) based on Long Short-Term Memory (LSTM) Neural Network (NN) and hybrid optimization algorithm is pro-posed. First, a dynamic compensator with a combined LSTM NN architecture is constructed to compensate for the initial error between the experimental data and CLM of a turbofan engine under health condition. Then, a sensitivity analysis approach based on the entropy coefficient and technique for order preference by similarity to an ideal solution integrated evaluation is developed to choose the unmeasurable health parameters to be adjusted. Finally, a parallel hybrid optimization algorithm is developed to complete the adaptive model modification when the performance degrades. The proposed method is verified on a military low-bypass twin-spool turbofan engine, and the experimental results show the effectiveness of the proposed method.