Simulation of Start-Up Process of Turbofan Engine Based on Full-State Characteristics of Fan

Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.

MODEL REFERENCE ADAPTIVE CONTROL BASED ON NONLINEAR COMPENSATION FOR TURBOFAN ENGINE

The design of a turbofan rotor speed control system, using model reference adaptive control（MRAC） method with input and output measurements, is discussed for the purpose of practical application. The nonlinear compensator based on functional link neural network is used to deal with the engine nonlinearity and the hardware-in-loop simulation is also developed. The results show that the nonlinear MRAC controller has the adequate performance of compensating and adapting nonlinearity arising from the change of engine state or working environment. Such feature demonstrates potential practical applications of MRAC for aeroengine control system.

Load Sharing Behavior of Star Gearing Reducer for Geared Turbofan Engine

Load sharing behavior is very important for power-split gearing system, star gearing reducer as a new type and special transmission system can be used in many industry fields. However, there is few literature regarding the key multiple-split load sharing issue in main gearbox used in new type geared turbofan engine. Further mechanism anal- ysis are made on load sharing behavior among star gears of star gearing reducer for geared turbofan engine. Compre- hensive meshing error analysis are conducted on eccentricity error, gear thickness error, base pitch error, assembly error, and bearing error of star gearing reducer respectively. Floating meshing error resulting from meshing clearance variation caused by the simultaneous floating of sun gear and annular gear are taken into account. A refined mathematical model for load sharing coefficient calculation is established in consideration of different meshing stiffness and support- ing stiffness for components. The regular curves of load sharing coefficient under the influence of interactions, single action and single variation of various component errors are obtained. The accurate sensitivity of load sharing coefficienttoward different errors is mastered. The load sharing coef- ficient of star gearing reducer is 1.033 and the maximum meshing force in gear tooth is about 3010 N. This paper provides scientific theory evidences for optimal parameter design and proper tolerance distribution in advanced devel- opment and manufacturing process, so as to achieve optimal effects in economy and technology.

Modeling and simulation of turbofan engine based on equilibrium manifold

Because the normal operation of the engine is located near the equilibrium manifold, the method of equilibrium mani fold nonlinear dynamic modeling is adopted for turbofan engine more than the local train modeling. The method studies the sys tem characteristics near the equilibrium manifold. The modeling method can be realized through dynamic and static twostep, and for the specific parameter modeling steps and algorithm are given. The output of the test data is compared with the model output through numerical simulation, to check the model with an additional set of test data. The simulation results show that the model has reached the requirements of engineering accuracy.

MULTIVARIABLE MODEL REFERENCE ADAPTIVE CONTROL FOR A TURBOFAN ENGINE

A decentralized model reference adaptive control (MRAC) scheme is proposed and applied to design a multivariable control system of a dual-spool turbofan engine.Simulation studies show good static and dynamic performance of the system over the fullflight envelope. Simulation results also show the good effectiveness of reducing interactionin the multivariable system with significant coupling. The control system developed has awide frequency band to satisfy the strict engineering requirement and is practical for engineering applications.

Component Matching Based on Low Bypass Ratio Mixed Exhaust Turbofan Engine

In order to study component matching which exists in off-design situation at the initial design stage of turbine engine,by establishing performance analysis model of low bypass ratio mixed flow turbofan engine and components characteristic data,and by applying Newton-Raphson method to solve the nonlinear equations of offdesign points in flying envelop,the factors which affect matching between engine components are studied.The results show that low pressure turbine(LPT)must not operate in a critical condition,and the partial derivative(slope)of pressure ratio to similitude mass flow ratio of working point in LPT characteristic map affects the stability of engine.The smaller the slope is,the more stable the engine is.In addition,the engine is more stable when the fan characteristic map is steep.

Simplified Removable Ground Test-Bed for Testing Turbofan Engine

A new simplified removable ground test-bed was designed for testing a certainturbofan engine. The facilities are 5.5 m long, 1.5 m wide, 2.2 m high and not more than 4. 5 t ofits empty weight. There are four rubber wheels that could be towed. There is an independentelectrical measurement and control system to test the rotational speed of rotors, the gas pressureof the compressor, the exhaust gas temperature, etc. Cooperated with the oil truck and the electricpower supply truck, the turbofan engine could be preserved on the ground and started to the idlingregime. While running, the parameter of the engine could be recorded, disposed and displayed. Inaddition, the facilities were successfully applied to the plateau experiment in order to researchhow the atmosphere pressure affects the start of engines. Some data are given in the paper.

Reliability Based Multi-Objective Thermodynamic Cycle Optimisation of Turbofan Engines Using Luus-Jaakola Algorithm

Aircraft engine design is a complicated process,as it involves huge number of components.The design process begins with parametric cycle analysis.It is crucial to determine the optimum values of the cycle parameters that would give a robust design in the early phase of engine development,to shorten the design cycle for cost saving and man-hour reduction.To obtain a robust solution,optimisation program is often being executed more than once,especially in Reliability Based Design Optimisations(RBDO)with Monte-Carlo Simulation(MCS)scheme for complex systems which require thousands to millions of optimisation loops to be executed.This paper presents a fast heuristic technique to optimise the thermodynamic cycle of two-spool separated flow turbofan engines based on energy and probability of failure criteria based on Luus-Jaakola algorithm(LJ).A computer program called Turbo Jet Engine Optimiser v2.0(TJEO-2.0)has been developed to perform the optimisation calculation.The program is made up of inner and outer loops,where LJ is used in the outer loop to determine the design variables while parametric cycle analysis of the engine is done in the inner loop to determine the engine performance.Latin-Hypercube-Sampling(LHS)technique is used to sample the design and model variations for uncertainty analysis.The results show that optimisation without reliability criteria may lead to high probability of failure of more than 11%on average.The thrust obtained with uncertainty quantification was about 25%higher than the one without uncertainty quantification,at the expense of less than 3%of fuel consumption.The proposed algorithm can solve the turbofan RBDO problem within 3 min.

Sustainable Design of Turbofan Engine： A Computer-Aided Design and Finite Element Analysis

A compressive design and analysis of a turbofan engine is presented in this paper. The components of jet engine have been analyzed based on mechanical design concept. An attempt has been to select materials based on sustainability and green design considerations. The energy content （e） of the materials has been one of the parameters for material selection. The choice of material has a substantial impact on cost, manuthcturing process, and the life cycle efficiency. All components nose cone, fan blade, inlet shaft, including compressor has been solid modeled using Siemens NX 11.0 CAD software. The finite element analysis of every component was performed and found safe. A tolerance analysis was performed before assembly of the turbofan engine. A numerical analysis was completed on blade and inlet geometries to determine a more efficient turbofan engine. Thermal analysis was executed oi1 the cone and suitable corrections were made. Finally, the cost and the total energy were estimated to show how much energy is needed to manufacture a turbofan jet engine.

Cost Prediction of a Turbofan Engine Using the Robust Partial Least Squares Method

In recent years, the cost of engines has become increasingly important to engine manufacturers, who are consistently faced with major problems on how to reduce cost to a minimum. Cost has become a decisive factor for aircraft design. To control the continual rapid increased cost, engine cost prediction is indispensable early in the design phase. But the cost data of an aircraft engine is small; we introduce the Robust Partial Least Squares Method in solving this problem, and reducing or removing the effect of outlying data points, which is different from the Classical PLS. We use the MATLAB software doing several simulations; results and analysis of a real turbofan engine data set show the effectiveness and robustness of the Robust PLS method. The Robust PLS method can effectively be used to estimate Turbofan Engine cost with reasonable accuracy.

Simulation of the secondary air system of turbofan engines:Insights from 1D-3D modeling

Focusing on the internal flow and heat transfer analysis,a platform for the performance evaluation of the Secondary Air System(SAS)is developed.A multi-fidelity modeling technique has been developed in a turbofan engine model under different flight conditions.A turbine blade cool-ing model which integrates external heat transfer calculations and coolant side modeling with com-mon components is proposed.In addition,the Computational Fluid Dynamics(CFD)method is selected to capture the complex flow field structure in the preswirl system.The validity of the SAS models is compared with publicly available data.An elaborately designed cooling system for the AGTF30 engine is analyzed through three main branches.It is found that the 1D-3D mod-eling technique can provide more accurate predictions of the SAS for the AGTF30 engine.The results demonstrate the versatility and flexibility of the SAS models,thereby indicating the capacity of meeting most of the demands of flow and thermal analysis of the SAS.

Multivariable Decoupling Control of Civil Turbofan Engines Based on Fully Actuated System Approach

Gas turbine engines must be operated by means of control,and how to achieve multivariable control decoupling with aero-engine control constraints is an open thorny issue attracting increasingly more attention.The paper considers the multivariable decoupling problems of aero-engines by using a compound controller,which originates from the fact that it is impossible to eliminate all the nonlinear dynamics of system to obtain desired constant linear closed-loop system by using full actuated control because of modeling errors and some physical constraints.Two controllers are involved in the compound controller.One is a fully actuated controller and the other is classical feedback controller.In order to use fully actuated control and maintain the accuracy of engine model,a full state scheduling linear parameter-varying(LPV)modeling method is proposed based on fuzzy neural network weights.For a general input matrix of the system,its generalized inverse is applied to design fully actuated controller to result in a pseudolinear system.Combined with a feedback controller and control limiter,the control synthesis is achieved.The simulation shows that the proposed method is possessed of a better decoupling and tracking effect compared with traditional control approach.

大涵道比涡扇发动机安装节动力学设计及性能评估分析进展

综述了大涵道比涡扇发动机安装节动力学设计及评估问题。首先从减振设计需求出发,论述了发动机安装节开展动力学设计的重大意义,并对安装节的主要结构形式及特点进行了详细的阐述;进一步从军民用标准规范和工程实践经验出发,归纳了安装系统动力学设计技术要求;而后从动力学设计、性能评估、系统验证等方面回顾了涡扇发动机安装节的国内外研究现状,指出国内外差距主要体现在设计要求、设计理念和应用实践经验等方面。在此基础上,展望了大涵道比涡扇发动机安装节动力学设计及性能评估技术的发展趋势和热点。

小尺寸无静叶对转风扇/压气机气动设计与变工况性能分析研究

无静叶对转风扇/压气机能有效减小发动机陀螺力矩,在轴向长度方面具有优势。然而,无静叶往往导致下游叶片攻角变化较大,变工况性能难以保证,且这一特点随叶尖切线速度的增大而恶化。本文利用小尺寸涡扇发动机风扇叶片根部周向速度较低的特点,尝试对其进行风扇与压气机无静叶对转方案设计。通过速度三角形分析了无静叶对转风扇/压气机的性能特点,开发了无静叶对转风扇/压气机一维设计程序进行参数方案的筛选优化,设计得到小尺寸无静叶对转风扇/压气机构型方案,设计点效率为85.1%,压比为3.16。结果表明,对转压气机的下排叶片相对进口气流角的变化范围较常规转叶+静叶相对进口气流角范围更小,而对转下排叶片的进口速度却将增大1.5~3倍,因此,需要合理选择对转风扇/压气机的轮毂比及转速比,才能保证对转风扇/压气机变转速工况下的设计点效率及失速裕度。减小对转风扇/压气机转速比有利于提高设计点效率和裕度,但本文受发动机总体指标限制,对转速比选择进行了折中。

基于冲击的涡扇发动机退化建模与下发预测

为解决多性能参数模型无法描述不同起飞推力下发动机性能退化的问题,利用单性能参数结合极端冲击模型描述起飞时发动机全功率运转对热端部件的热冲击影响,利用线性退化模型描述发动机自然退化过程,建立发动机性能可靠度退化模型。利用V2500发动机全寿命EGTM数据,结合最大似然估计给出性能可靠度表达式与模型参数,最后利用机队中同型V2500发动机非完整EGTM数据验证模型,预测下发时间,结果表明此模型预测下发时间和实际下发时间的误差小于3%,证明了模型的有效性。

涡扇发动机高原起动供油调整规律研究及故障分析

以某型涡扇发动机高原起动试验为研究对象,通过建立关键事件方式建立起动调整策略分析方法,总结分析了高原起动特点及起动供油量的调整规律,并针对发动机起动过程中出现的几种典型的失速、热悬挂失败案例,分析获得了起动失败的原因。结果表明:高原冷态起动失败主要为起动机脱开后发动机失速为主;热态起动失败主要为低压转子阻力矩增大导致热悬挂为主;起动供油调整规律为起动第二阶段减小供油量,起动第三阶段增加供油量。并提出了提升高原起动成功率的建议,可为发动机高原使用提供参考。

基于参数匹配的航空发动机飞行性能评估技术研究

本文提出了一种基于参数匹配的发动机性能评估模型建立方法,在不依赖部件特性的情况下,以发动机可测截面参数作为输入,建立影响系数矩阵,利用罚函数法求解非直接测量参数的极小二范数解,建立了考虑性能衰减影响的发动机性能评估模型。以某型大涵道比涡扇发动机仿真模型为应用对象,结果显示,在全包线内的典型工作状态下,仿真数据与评估模型计算数据相对误差小于4.5%,表明性能评估模型建立方法是正确的,所建立的性能评估模型可满足工程使用要求。

涡扇发动机再压缩CCA系统热力循环耦合分析

为了提高发动机的推进性能和热效率,同时改善发动机冷却引气品质,在传统预冷冷却空气(cooled cooling air,CCA)技术基础上,建立基于再压缩CCA系统的典型飞机发动机热力计算耦合分析仿真平台.结合涡轮叶片平均壁温计算模型和飞机/发动机总体匹配模型,分析再压缩CCA系统对涡轮叶片冷却效果、发动机总体性能及相应飞行性能的影响规律.结果表明:采用减小引气比的方式未加力时推力最高提升7.88%,加力时推力最高提升2.03%;加力时耗油率降低、热效率提升,冷却引气总温降低100~120 K、总压提升4%左右,高压涡轮导叶冷却效果提高显著.采用提高燃烧室最高出口温度的方式未加力时推力最高提升22.81%,加力时推力最高提升3.70%;加力时耗油率降低、热效率提升,冷却引气总温降低90 K左右,且在各任务航段高压涡轮叶片温度均低于许用温度.两种方案再压缩CCA系统对发动机性能损失基本无影响,取功比在各状态下均低于0.25%.

脉冲爆震外涵加力涡扇发动机总体性能研究

为研究外涵装有脉冲爆震燃烧室(PDC)的混合排气涡扇发动机性能,建立其性能模型。研究了隔离段总压恢复系数和外涵循环参数对PDC特性和整机性能的影响;分析了发动机性能参数对部件参数的敏感性;在相同设计循环参数下与传统加力涡扇发动机性能进行了对比。结果表明:提高隔离段总压恢复系数能够增大PDC增压比,提升发动机性能;风扇压比一定,涵道比增大,发动机耗油率和单位推力增大;风扇压比增大,涵道比在0.2~0.4时,单位推力先增大后减小,涵道比在0.4~0.5时,单位推力先增大后基本不变,涵道比在0.5~0.9时,单位推力一直增大,但增幅逐渐减小。不同涵道比下耗油率随风扇压比增大一直减小;发动机性能对直接影响外涵气流状态参数的部件参数敏感性高;由于PDC的增压特性,脉冲爆震外涵加力发动机仅利用外涵部分气流组织燃烧就可使单位推力与传统加力涡扇发动机相当,且耗油率在设计点降低27.7%,非设计点降低12.8%~26.8%。

机械剩余使用寿命预测模型的增量学习方法

机械剩余使用寿命预测模型依据设备状态监测数据样本进行寿命预测,当样本模式发生变化时,基于原模式样本训练好的模型在新模式样本上的预测表现往往较差。为使模型保留对原模式样本的处理能力,同时拓展出针对新模式样本的处理能力,提出了3种增量学习方法:第一种方法使用新模式样本与原模式样本的标签值构建损失函数;第二种方法在第一种方法基础上增加了模型参数初始化步骤;第三种方法在第一种方法的损失函数中增加了表示当前模型与原模型参数分布差异的正则化项。在涡扇发动机数据集上进行了不同学习方法的对比实验,结果表明所提方法实现了增量学习的目标,其中第三种方法在模型预测准确度和模型训练时长两方面取得了最优的综合表现。