基于约束卡尔曼滤波的航空发动机状态变量模型辨识方法

为建立高精度的航空发动机状态变量模型,采用约束卡尔曼滤波算法辨识民用涡扇发动机非线性模型以及某型涡轴发动机试车数据状态变量方程矩阵参数。研究表明:基于约束卡尔曼滤波算法能够辨识得到高精度的状态变量模型,相比标准卡尔曼滤波算法,改进的卡尔曼滤波算法可以明显加快模型参数收敛速度、减小稳态误差。     

WTGS非线性动态模型的T-S模糊线性化

针对变速变桨风力发电系统(WTGS)的非线性动态模型,采用Takagi-Sugneo(T-S)模糊建模理论处理其非线性,以得到高精度的线性形式控制设计模型.首先,提取代表WTGS变工况特性的外部参量作为变化参数,并理论抽象出一类仿射非线性参数变化(ANPV)模型,给出其齐次线性T-S模糊线性化步骤并得到线性参数变化(LPV)T-S模糊模型.然后,将上述方法应用于WTGS非线性动态模型的T-S模糊线性化.最后,针对WTGS的LPV T-S模糊模型对其非线性特性的逼近性能进行仿真验证.结果表明:通过改变T-S模糊模型前提变量输入空间的划分精度,可以有效调节LPV T-S模糊模型对WTGS非线性特性的逼近性能.     

改进1D-CNN和LSTM的涡扇发动机剩余寿命预测

针对单一深度学习网络对涡扇发动机退化特征提取不足、超参数选择困难的问题，提出一种改进一维卷积神经网络(1-Dimensional Convolutional Neural Network, 1D-CNN)和长短时记忆网络(Long Short-Term Memory, LSTM)的涡扇发动机剩余寿命预测方法。首先，利用相关性、单调性和离散性一系列评价指标对涡扇发动机的多维传感器特征参数进行评价和选择，将综合评价指标高的优选特征参数作为1D-CNN的原始输入特征；然后，通过改进激活函数和Dropout函数来提升1D-CNN的特征提取能力，构建表征发动机退化趋势的一维复合健康指标；最后，利用贝叶斯优化(Bayesian Optimization, BO)的LSTM挖掘一维复合健康指标的时间特征，并实现剩余寿命预测。为验证此方法的预测效果，采用美国国家航空航天局提供的涡扇发动机退化数据集进行剩余寿命预测，实验的均方根误差为14.040 2,评分函数值为314.607 8。结果表明：相比于单一深度学习方法和传统机器学习方法，该方法不仅能获得较高的剩余寿命预测精度，还能有效解决深度学习模型超参数...     

基于动态约束分析的舰载机着舰复飞技术研究

基于涡扇发动机动态模型和飞机气动模型,以舰载机着舰过程为典型剖面,依据能量法建立飞/发一体化控制模型,作为舰载机着舰复飞研究的基础。模型充分考虑了着陆时的升阻特性、地面效应和飞机重量等因素,采用功率提取法改进涡扇发动机加速控制规律和供油规律,并与原控制规律进行比较,结果表明新加速控制规律可以有效减少复飞所需的甲板滑跑长度和增加着舰重量,为舰载机着舰复飞方案设计提供借鉴和参考。     

基于LMI的航空发动机状态反馈最优控制

提出了基于线性矩阵不等式(Linear Matrix Inequality,LMI)的带有时滞的离散分段线性系统状态反馈最优控制规律,并将其应用于航空发动机控制器设计中。基于某型双轴航空涡扇发动机地面试车非线性模型,使用小偏差法建立了该发动机离散线性状态空间模型。基于线性模型,实现了基于LMI的控制器增益的计算,并在非线性模型上进行了仿真试验。仿真结果表明,在大工况范围下,LMI控制器较传统的PID控制器,能有效缩短发动机的动态响应时间并降低超调量。     

基于BP神经网络乙醇汽油与无铅汽油排放性能分析

BP网络模型用于检测发动机燃烧乙醇汽油排放,可以解决发动机燃烧乙醇排放的非线性问题。笔者选用了转速和功率(负荷)为变量,对发动机燃烧乙醇汽油产生的排放物进行建模,在误差允许的范围内能较好地预测排放性能,并且与无铅汽油产生的排放物进行分析比较,突出乙醇汽油(E10)较无铅汽油的排放性能优越性。     

航空发动机模糊滑模控制方法的比较研究

研究了航空发动机的模糊滑模控制方法,使航空发动机在较广的运行条件下满足控制需求。采用一维间接模糊滑模控制、二维直接模糊滑模控制这两种方法设计模糊滑模控制器,并通过仿真对比,分析了两种设计方法在航空发动机线性模型和用LPV建模法建立的非线性模型上的控制效果。仿真结果表明,二维模糊滑模控制方法具有响应快,对外界干扰不敏感,系统鲁棒性强且非线性跟踪效果好的优点,其控制效果优于一维模糊滑模控制方法。     

发动机失火检测中的转速齿盘制造误差影响及修正算法研究

基于曲轴转速波动进行发动机失火诊断时需要考虑曲轴转速传感器的58X信号齿盘制造误差的影响.本研究在奇瑞477F发动机上采用自行开发的失火检测系统,研究了58X齿盘的齿形加工误差对失火诊断的影响,改进了失火诊断算法中的齿盘误差修正算法.     

基于一缸缸压和瞬时转速的内燃机分缸燃烧状态估计

提出了一种基于曲轴瞬时转速分析和一个缸压传感器结合进行发动机的分缸燃烧状态估计的方法。试验研究表明:基于刚性模型和曲轴瞬时转速分析估计得到的各缸指示转矩误差有相似性,装有缸压传感器的参考缸可以得到误差信号并用于修正其他缸指示转矩估计结果,修正后指示转矩估计误差大幅降低。根据估计的指示转矩可以分析各缸的燃烧状态参数,平均指示有效压力估计值误差小于0.05MPa,最大燃烧转矩位置误差小于3°。与只采用曲轴转速信号相比,模型不依赖复杂算法并具有较高精度,鲁棒性更好。     

发动机怠速的离散滑模控制

设计了发动机怠速的离散滑模(DSM)控制器,用已开发出的4缸、1.4L的AJR发动机怠速控制系统的非线性模型进行发动机怠速转速的控制。实验结果表明,与原机的控制器相比较而言,DSM控制器在跟踪期望怠速转速及抗干扰等方面具有优良的性能。     

内_外函分流的某涡轮风扇燃气发生器性能试验

途述了带外函道的双转子发动机内、外函分流,各自通流阻力可以改变的燃气发生器试验装置和试验结果。本燃气发生器试验结果将为涡轮风扇发动机在陆上应用提供有价值的试验数据和发动机改装途径。     

Counter Rotating Fans- An Aircraft Propulsion for the Future?

In the mid seventies a new propulsor for aircraft was designed and investigated - the so-called PROPFAN. With regard to the total pressure increase, it ranges between a conventional propeller and a turbofan with very high bypass ratio. This new propulsion system promised a reduction in fuel consumption of 15 to 25% compared to engines at that time.A lot of propfans (Hamilton Standard, USA) with different numbers of blades and blade shapes have been designed and tested in wind tunnels in order to find an optimum in efficiency, Fig.1. Parallel to this development GE, USA, made a design of a counter rotating unducted propfan, the so-called UDF, Fig.2. A prototype engine was manufactured and investigated on an in-flight test bed mounted at the MD82 and the B727. Since that time there has not been any further development of propfans (except AN 70 with NK 90-engine, Ukraine, which is more or less a propeller design) due to relatively low fuel prices and technical obstacles. Only technical programs in differen     

Counter Rotating Fans—An Aircraft Propulsion for the Future？

In the mid seventies a new propulsor for aircraft was designed and investigated - the so-called PROPFAN. With regard to the total pressure increase, it ranges between a conventional propeller and a turbofan with very high bypass ratio. This new propulsion system promised a reduction in fuel consumption of 15 to 25% compared to engines at that time. A lot of propfans (Hamilton Standard, USA) with different numbers of blades and blade shapes have been designed and tested in wind tunnels in order to find an optimum in efficiency, Fig.1. Parallel to this development GE, USA, made a design of a counter rotating unducted propfan, the so-called UDF, Fig.2. A prototype engine was manufactured and investigated on an in-flight test bed mounted at the MD82 and the B727. Since that time there has not been any further development of propfans (except AN 70 with NK 90-engine, Ukraine, which is more or less a propeller design) due to relatively low fuel prices and technical obstacles. Only technical programs in different countries are still going on in order to prepare a data base for designing counter rotating fans in terms of aeroacoustics, aerodynamics and aeroelasticities. In DLR, Germany, a lot of experimental and numerical work has been undertaken to understand the physical behaviour of the unsteady flow in a counter rotating fan.     

航空发动机最优翻修间隔评定研究

对单元体/大部件寿命控制模式下军用航空发动机最优翻修间隔的确定方法进行了研究。基于对军用航空发动机工程使用的分析,综合了发动机的使用安全性、使用经济性、使用性能衰减等因素,建立了航空发动机翻修间隔评价指标体系层次分析模型,确定了各层次指标权重系数。应用灰色综合评判方法,建立了航空发动机最优翻修间隔综合评判模型。结合某型涡扇发动机寿命控制的工程实际,综合评定了其最优翻修间隔,得出了国内该型发动机最优翻修间隔为700h的结论。     

Influence of Reynolds Number on the Unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct

The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption (SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine (HPT) to low pressure turbine (LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct (AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow’s point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer’s transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX (RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle’s suction side surface.     

Assessment of NOx emissions of the Scimitar engine at Mach 5 based on a thermodynamic cycle analysis

The Scimitar engine is a new advanced propulsion system designed to propel the aircraft A2 of the LAPCAT project. It is a hybrid system that utilizes the features of turbofan, ramjet and air-turborocket. Hydrogen and air are used as the fuel and oxidant, respectively, while helium is used to transfer heat from the hot incoming air to the hydrogen in the engine. In this study, we present a thermodynamic cycle analysis of the Scimitar engine for the assessment of NO_x emissions. The combustion of fuel is studied in detail with an equilibrium model taking into account various dissociation and formation reactions since high levels of temperatures are achieved in its combustion chamber. The NO_x emissions of the engine at Mach 5 and the effects of fuel and air flow rates, cruise speed and altitude on these emissions are presented by solving a nonlinear system of equations formed through our novel thermodynamic model. The results show that the NO emissions of the engine can be diminished significantly by decreasing air flow rate, cruise speed and altitude and by increasing the fuel flow rate. The variations of NO₂ emissions with these parameters are similar except the variation with altitude which has an inverse effect as compared to the variation of NO.     

大涵道比航空发动机风扇/增压级鸟撞性能数值模拟研究

针对民航客机涡扇发动机鸟撞问题,以某民机大涵道比涡扇发动机风扇/增压级为研究对象,将风扇鸟撞造成的缺损进行简化,构建了四种简化的鸟撞损伤模型。在此模型的基础上,采用数值模拟方法,预测和分析鸟撞损伤引起的风扇气动性能变化。通过分析得出,鸟撞后风扇流量、压比、效率、裕度均显著下降,缺损超过两片叶片后性能显著恶化。其中靠近损伤叶片吸力面一侧的叶片入口攻角增大,产生流动分离,是造成风扇裕度下降的关键叶片。     

Exergetic analysis of an aircraft turbofan engine

The main objective of the present study is to perform an exergy analysis of a turbofan kerosene‐fired engine with afterburner (AB) at sea level and an altitude of 11 000 m. The main components of this engine include a fan, a compressor, a combustion chamber, a turbine, an AB and an exhaust. Exergy destructions in each of the engine components are determined, while exergy efficiency values for both altitudes are calculated. The AB unit is found to have the highest exergy destruction with 48.1% of the whole engine at the sea level, followed by the exhaust, the combustion chamber and the turbine amounting to 29.7, 17.2 and 2.5%, respectively. The corresponding exergy efficiency values for the four components on the product/fuel basis are obtained to be 59.9, 65.6, 66.7 and 88.5%, while those for the whole engine at the sea level and an altitude of 11 000 m are calculated to be 66.1 and 54.2%. Copyright © 2007 John Wiley & Sons, Ltd.