梯形间隙处理机匣对于离心压气机性能的影响

针对高速离心压气机设计了6种梯状间隙机匣处理结构,采用数值模拟方法比较分析了不同机匣结构对离心压气机性能和稳定性的影响。结果表明:随着梯状间隙结构径向尺寸的增大,近失速点效率会随之逐渐下降,而稳定裕度值和近失速点压比则有所提高。梯状间隙结构大径向间隙区域的轴向尺寸变小,会使近失速点效率,压比以及稳定裕度值都略有增大。通过对叶顶区域流场的分析,揭示了梯状间隙结构机匣处理的扩稳机理。     

Exploration of combined adjustment laws about IGV,stator and rotational speed in off-design conditions in an axial compressor

Experimental investigations are performed in a three-stage low-speed axial compressor with variable inlet guide vanes(IGV) and adjustable stators.The characteristics of the compressor,especially the efficiency and stall margin,are analyzed in design and off-design operation conditions by adjusting stagger angles of IGV and stators as well as changing the rotational speed.The experimental results show that the off-design performance of the multistage axial compressor is improved by restaggering of IGV and st...     

Effects of injection frequency on the rotor stall margin

The stall margin of compressor could be improved effectively by rotor tip injection,and the periodic injection is commonly used in the research.The purpose of this work is to investigate the influence of injection frequency on the rotor stall margin.An unsteady CFD code was employed to simulate the flow field of the rotor with injections of different frequencies.Comparing the stall margin of the rotor with injections of different frequencies,it is shown that there is an optimal injection frequency,around wh...     

基于模糊熵的压气机失速信号分析研究

熵作为无序程度的度量,能够用于描述不同过程的复杂度或相似程度。采用模糊熵分析了某跨声压气机从稳定工作状态连续变化到失速工作状态过程中机匣壁面静压的变化情况,发现模糊熵值在压气机稳定工作状态下变化很小,而当模糊熵开始大幅值波动时压气机开始进入失速状态。将模糊熵分析结果与滤波分析进行对比表明,模糊熵可应用于压气机失速先兆信号的实时监测。     

槽深对跨音速压气机稳定性影响的数值仿真

为了研究不同槽深下的周向槽对压气机稳定性的影响,由于带槽结构下的转子37失速类型仍是叶尖失速,但是带周向槽结构的主要失速因素是叶尖间隙的泄漏涡,且不同轴向位置的周向槽所造成的损失也是不同的。为解决上述问题,利用NUMECA软件和系统的数值模型对某跨音速压气机进行了数值仿真,对三类带周向槽结构的计算结果进行了分析,结果表明,设计中讨论最佳槽深应先给定效率损失要求,并且应以研究最佳槽位置的选择为主。对压气机周向槽处理机匣的设计,不一定要设计涉及整个叶片的处理机匣。对于跨音速压气机在叶尖泄漏涡严重的位置优化设计,可提高压气机稳定性能。     

Useful nonlinearities and global stabilization of bifurcations in amodel of jet engine surge and stall

Compressor stall and surge are complex nonlinear instabilities that reduce the performance and can cause failure of aircraft engines. We design a feedback controller that globally stabilizes a broad range of possible equilibria in a nonlinear compressor model. With a novel backstepping design we retain the system's useful nonlinearities which would be cancelled in a feedback linearizing design. The design control law is simple and, moreover, it is optimal with respect to a meaningful nonquadratic cost functional. As in a previous bifurcation-theoretic design, we change the character of the bifurcation at the stall inception point from subcritical to supercritical. However, since we approach the bifurcation control using Lyapunov tools, our controller achieves not only local but also global stability. The controller requires minimal modeling information and simpler sensing (rotating stall is stabilized without measuring its amplitude)     

轴流压气机旋转失速建模与检测:基于确定学习理论与高阶Moore-Greitzer模型的研究

喘振和旋转失速是轴流压气机研究领域中重要而困难的问题. 本文基于确定学习理论及动态模式识别方法提出一个旋转失速初始扰动 近似准确建模和快速检测的方法. 首先,基于高阶Moore-Greitzer模型（Mansoux模型）,利用确定学习理论提出一个对旋转失速初始扰动的内在系统动态的近似准确建模方法;其次,基于以上近似准确建模,利用 动态模式识别方法提出一个对旋转失速初始扰动的快速检测方法. 基于MIT的Mansoux-C2模型仿真研究验证了 所提方法的有效性. 最后,在北京航空航天大学航空发动机重点实验室的低速轴流压气机试验台上开展了试验研究. 通过对低速轴流压气机试验台参数进行测量,得到基于北航低速轴流压气机试验台的Mansoux模型. 通过对基于北航试验台Mansoux模型进行仿真研究,验证了所提方法的有效性.     

Early detection of rotating stall in axial flow compressors via deterministic learning: detectability analysis

Rotating stall and surge are two violent unstable phenomena of an aero-engine compressor. The early detection of rotating stall is a critical and difficult issue in the operation of a compressor. Recently, a deterministic learning based stall inception detection approach (SIDA) has been developed for modeling and detecting stall inception in aero-engine compressors. This paper considers the derivation of analytical results on the detection capabilities for the SIDA based on deterministic learning. First, by utilizing the input/output stability of the residual system, a detectability condition of the SIDA is presented, and how to choose the parameters of the diagnostic system is also analyzed. Second, based on the relationship between NN approximation capabilities and radial basis function (RBF) network structures, the influence of RBF network structures on the performance properties of the SIDA is analyzed. Finally, a simulation study is presented, in which the Mansoux-C2 compressor model is utilized to verify the effectiveness of the proposed SIDA.     

航空涡轮发动机失稳预警信号提取方法的研究

综合航空涡轮发动机失稳先兆波的幅值特性与频率特性,设计出能够提取失稳先兆特征的处理方法,并据此对发动机失稳数据进行处理与分析。通过使用不同的参数,此方法可实现对模态波和尖脉冲型失稳的预警。处理结果表明,此提取方法能够在失稳前15～20个转子周期内,有效地对尖脉冲型失稳进行预报,对模态波型失稳能够在60～80个转子周期前预警。并且此提取方法的算法复杂度较低,有利于失稳的在线预警,对航空燃气涡轮发动机主动控制技术的发展具有十分重要的意义。     

某型压气机失速先兆研究

压气机失速时,其流场压力信号会发生变化,这种压力信号的特征频率固定在某一频率范围内.利用小波多分辨分析方法,提取包含特征频率的细节信号,并对该细节信号进行统计分析,得出稳定工作状态及失速状态信号的方差范围,由此确定滤波的阈值.通过阈值滤波,可以确定失速先兆信号及其出现的时刻.分析表明,该方法是有效的、可行的.     

天然气离心式压缩机组特性仿真

为解决某天然气压缩站离心式压缩机组特性评估问题,分析了离心式压缩机组的热力过程,深入研究了压缩机的多变效率、喘振裕度以及燃气轮机效率的计算方法,建立了离心式压缩机组特性仿真的数学模型并编制了仿真程序.通过使用VC 语言和Fortran语言混合编程,开发了人机界面友好、操作简单的离心压缩机组特性仿真软件.通过对实际离心压缩机组特性仿真,表明仿真程序具有很高的精度,开发的仿真软件能够方便地对天然气离心压缩机组的特性进行准确合理的评估.     

Simulation of rotating stall in a whole stage of an axial compressor

Aerodynamic instabilities that naturally occur in compression systems, such as surge and rotating stall, largely reduce the life duration and performance of system components. The prediction of the compressor operating range is thus a key parameter for the design of gas turbines. This paper investigates the ability of an unsteady flow solver to simulate the rotating stall phenomenon in the full annulus of an axial compressor stage. A comparison with experimental data indicates that the simulation correctly estimates the stability limit. However the rotating stall flow patterns are different. While measurements show only one full span rotating stall cell (40 Hz), the simulation shows first a part span stall with 10 cells (790 Hz) that evolves then towards a full span stall with three cells (170 Hz). A spectral analysis based on numerical results underlines the role of rotor-stator interactions in the development of rotating stall. The effects of downstream volumes and inlet distortions are also discussed, showing the necessity to consider the whole geometry to correctly predict the rotating stall frequency.     

轴流压气机转子叶顶间隙流动结构及机理研究

研究某轴流压气机叶顶复杂流动问题,为深入了解压气机叶顶泄漏流流动机制和引发失速的机理,对一亚音速轴流压气机进行全工况数值仿真与试验测量。提出通过对比试验数据和分析泄漏流的流动特性,随着压气机负荷的提高,泄漏流方向的改变引起叶顶堵塞区增大,并诱发压气机失速。采用不同工况下叶顶流场进行仿真对比分析。仿真结果表明,泄漏流与主流相互作用形成泄漏涡,距前缘40%弦长范围内泄漏流影响泄漏涡形态变化,其余部分泄漏流主要通过周向输运低能流体进一步堵塞通道;叶顶压力分布是决定泄漏流方向的主要因素。     

Robust Surge Avoidance Control for a Low Pressure Compressor of a Turbojet Engine

The aim of this paper is to improve the efficiency of a low pressure compressor within a turbojet engine. For this purpose a new feedback controller will be introduced which compares the actual compressor surge margin to a given reference value. Then, this new feedback controller calculates a deviation on the existing nozzle area schedule such that the overall efficiency of the controller is improved at steady state condition. The major contribution of this work consists in a robust control design approach leading to improved robustness properties and reduced calibration efforts for the controllers of future unmanned aircraft propulsion systems.     

Bifurcation stabilization of nonlinear systems by dynamic output feedback with application to rotating stall control

The paper deals with the problem of stabilization of stationary bifurcation solutions of nonlinear systems via dynamic output feedback.It is emphasized that the parameter of the system is not directly available.We introduce the concepts of uniform observability of the inverse of a function of state and input and N-order-input-to-state bifurcation stability.Based on the concepts,we propose a new method for designing dynamic compensators that guarantee bifurcation stability for the closed-loop system.As an example,we apply the general theory to active control of rotating stall in axial flow compressors by designing a stabilizing dynamic compensator for the three-state Moore-Greitzer model with a class of cubic compressor characteristics.     

Intriguing nonlinear dynamics of a controller with a sluggish actuator

We apply a bifurcation-theoretic approach to the standard Moore–Greitzer compressor model in effort to understand a curious phenomenon. When one forces the actuator to respond sluggishly to commanded inputs, performance of the controller improves dramatically. We show that the behavior can be explained via Hopf–Hopf interactions of surge and rotating stall. Also, we argue that there is a broad class of controllers which possess the general dynamic features responsible for the surprising effectiveness of sluggish actuators.     

Bifurcation control of rotating stall with actuator magnitude and rate limits: Part II—control synthesis and comparison with experiments

Operability enhancement is defined as the extension of operating range for which fully developed rotating stall is avoided. It is proved that the rate-saturated control law is the optimal control that maximizes the operability enhancement. For the controlled system with the rate-saturated controller, analytic formulas are derived for the operability enhancement as a function of noise level, actuator saturation limits, and the shape of the compressor characteristic, which is the major nonlinearity in the model. The shape of the compressor characteristic, especially the unstable part, is critical to the rate required for robust operability near the peak for the closed-loop system. Experiments are carried out on a single-stage low-speed axial compressor using different levels of steady air injections to generate compressor characteristics with different shapes. The rate requirement predicted by the theoretical formulas agrees qualitatively with experiments and simulations of a higher order model (37 states).     

Shape signifiers for control of a low-order compressor model

Rotating stall and surge, two instability mechanisms limiting the performance of aeroengines compressors, are studied on the third-order Moore-Greitzer model. The skewness of the compressor characteristic, a single parameter shape signifier, is shown to determine the key qualitative properties of feedback control     

跨音级轴流压气机转子轮毂非轴对称造型研究

关于优化提高压气机效能问题,由于压气机通道的二次流流动会造成流动损失,引起效率下降.为了解决上述问题,通过改变轮毂端壁结构,可以控制二次流流动,以提高压气机效率.采用人工神经网络及遗传算法的叶轮机械三维优化建模方法,使在最高效率工况下可以保持流量不变,压比不低于优化前.对压气机转子轮毂结构进行了优化,得到新型非轴对称端壁结构,并进行仿真.结果表明,降低了转子通道内的相对总压损失,抑制了下游静叶角区分离,可使压气机提高效率,并能有效控制端壁附近的流动损失,提高压气机效率.     

气柱共振和涡轮增压器喘振噪声分析

针对使用废气涡轮增压器带来的振动和噪声的问题,在增压器进气口和中间体上进行噪声与振动测试,在增压器前、后的气体管道上进行压力脉动测试.测试发现,在发动机转速2 000 r/min,85%负荷时,出现强烈的气体共振和增压器喘振.对发生喘振的原因进行流体力学计算分析,结果表明共振产生在气体进入压气机叶轮之前的管道内.推测增压器发生喘振的根源为气体流动呈现轴对称旋转流状态,增压器管道内气体无法继续向前流动,导致气体回流,增压器失速.根据四分之一波长理论,在增压器压前管道上增加一个支管. 测试验证表明,改进后气体共振和增压器喘振噪声均消失,增压器运转平稳,改进效果明显.