Physical model for acoustic resonance in annular cavity structure

A physical model for acoustic resonance in the annular cavity structure is developed to represent the typical characteristic when acoustic resonance occurs. Firstly, the measurement of sound pressure in the casing and rotor blades vibration is operated in a multistage high pressure compressor. The sharp peak frequency and discrete multi-tone occur in the frequency spectrum of sound pressure in the compressor, and the vibration of the first stage of rotor blades synchronously presents the high amplitude. The frequencies associated with rotor blades vibration can be calculated with rotating sound source theory. It is also confirmed that acoustic resonance occurs in the multistage compressor. With acoustic similarity principle, an annular cavity model is established to simulate the typical characteristics of acoustic resonance in the compressor based on Large Eddy Simulation (LES) and Lighthill acoustic analogy. The coupling relationship between cavity acoustic mode and disc vibration mode shape is expounded when acoustic resonance occurs in the model. And acoustic resonance will be locked in the certain flow rate range. All these characteristics match well with those occur in the multistage high pressure compressor.     

Experimental and numerical study of tip injection in a subsonic axial flow compressor

Parametric study of tip injection was implemented experimentally on a subsonic axial flow compressor to understand the underlying flow mechanisms of stability improvement of the compressor with discrete tip injection.Injector throat height varied from 2 to 6 times the height of rotor tip clearance,and circumferential coverage percentage ranged from 8.3％ to 25％ of the annulus.Static pressure fluctuations over the rotor tip were measured with fast-response pressure transducers.Whole-passage time-accurate simulations were also carried out to help us understand the flow details.The combinations of tip injection with traditional casing treatments were experi mentally studied to generate an engineering-acceptable method of compressor stall control.The results indicate that the maximum stability improvement is achieved when injectors are choked despite their different sizes.The effect of circumferential coverage percentage on compressor stabil ity depends on the value of injector throat height for un-choked injectors,and vice versa.Tip blockage in the blade passage is greatly reduced by the choked injectors,which is the primary reason for stability enhancement.The accomplishment of blockage diminishment is maintained in the circumferential direction with the unsteady effect of tip injection,which manifests as a hysteresis between the recovery of tip blockage and the recovery of tip leakage vortex.The unsteady effect is primarily responsible for the effectiveness of tip injection with a partial circumferential coverage.Tip injection cannot enhance the stability of the rotor with axial slots significantly,but it can improve the stabil ity of the rotor with circumferential grooves further.The combined structure of tip injection with circumferential grooves is an alternative for engineering application.     

低雷诺数下高负荷轴流压气机表面粗糙度流动调控机制

以某1.5级高负荷轴流压气机为研究对象,采用经过校核的数值模拟手段详细探究了低雷诺数下表面粗糙度对其气动性能及内部流场的影响.结果表明:相比于光滑叶片,表面粗糙度为137.8时压气机性能提升最为明显,总压比、堵塞流量以及峰值效率分别提升4.01％、2.24％、5.34％.在整个表面粗糙度大小范围内,表面粗糙度布置在吸力...     

Mechanism of stall and surge in a centrifugal compressor with a variable vaned diffuser

To expand the stable operating range of compressors, understanding the mechanism of flow instability at low flow rates is necessary. In this paper, the mechanism of stall and surge in a centrifugal compressor with a variable vaned diffuser is experimentally investigated, where the diffuser blade setting angle can be adjusted. Many dynamic pressure transducers are mounted on the casing surface of the compressor. From the design condition to surge, dynamic pressure data is recorded throughout the gradual process. According to the signal developing status, the typical modes of compressor instability are defined in detail, such as stall, mild surge, and deep surge. A relatively high-frequency stall wave originates in the impeller and propagates to the diffuser, and finally stimulates a deep surge in the compressor. The compressor behavior during surge differs at different diffuser vane angles. When the diffuser vane angle is adjusted, both the unstable form and the core factor affecting the overall machine stability change. A specific indicator is proposed to measure the instability of each component in a compressor, which can be used to determine the best region for stability extension technologies, such as a holed casing treatment, in different compressor applications.     

某型涡轮轴发动机轴流压气机转子振动特性分析

通过增大叶片径向尺寸 ,减少叶片数量 ,对涡轮轴发动机整体式轴流转子做了结构改进 ,并采用DA SOBD有限元程序对因结构改进引起的叶轮振动进行了分析     

应用S2流面准三元计算程序分析小型发动机的跨音压气机气动特性

应用Ｓ２流面准三元计算程序，对两台典型小型发动机压气机（Ｉ型机、Ⅱ型机）的气动性能进行了分析。更加真实地揭示了它们内部的流动情况，并分析了它们的改进思想和方法。其中Ｉ型机是应用“平均设计”思想设计的早期跨音压气机，Ⅱ型机是其成功的改型机。     

高负荷风扇级的特性实验与流场分析

为了探索高负荷风扇级的流场特性,积累这方面的设计经验,在压比和效率特性之外,还分别利用三孔针和总压耙对所实验风扇级的出口有关参数进行了测量。同时,为了辅助分析问题,借助了CFD研究了转静根部的匹配问题。对根部区域的实验和计算现象进行了重点讨论,并指出了不足和进一步改进的方向。     

飞行控制系统故障检测方法研究

以某型飞机为研究对象，论述了一种基于模型的自修复飞行控制系统故障检测方法。首先提出了通过等价空间法产生残差序列，并对残差序列进行概率比检测，以获得一定置信度下的检测结果。同时舵面损伤故障的概率比检测采用预警检验、校验检测与隔离检测相结合的方法。最后，对所设计的故障检测方法进行了数字仿真研究。仿真结果验证了该方法具有较高的准确性和实时性，为飞行控制系统故障检测提供了一种有效的手段。     

转子叶尖间隙测量在风扇和压气机性能试验中的应用

通过在发动机风扇和压气机部件性能试验中对转子叶尖间隙随试验状态变化进行的实测,分析间隙变化对性能的影响,阐述间隙测量的重要性,提出不同应用场合下间隙测量的方法和一些建议。     

跨声速轴流压气机级全工况三维流场数值分析

以LV－SGS－GE隐式格式和MUSCL TVD迎风格式为基础，结合壁面函数方法和简单的混合长度湍流模型，对三维可压缩雷诺平均N－S方程进行求解。叶列间参数的传递采用混合平面方法并应用了微机网络并行计算技术。计算得到了NASA 35号低展弦比、跨声速轴流压气机组70％和90％设计转速下的全工况性能曲线，并重点分析了其中一些典型工况下的内部流场。计算与实验结果的对比表明，此方法能快速得到三维粘性流场的流动特性且计算精度较高，可用来模拟跨声速轴流压气机组内的全工况三维粘性流动。