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Self-lubricating bidirectional carbon fiber reinforced smart aluminum composites by squeeze infiltration process

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Journal of Materials Science & Technology 2019年第11期35卷 2559-2569页

作者： K.M.Sree Manu L.Ajay Raag T.P.D.Rajan B.C.Pai Vijay Petley Shweta Namdeo Verma CSIR-National institute for Interdisciplinary Science and Technology TrivandrumIndia gas turbine research Establishment(GTRE) BangaloreIndia

Self-lubrication is one of the smart material properties required for producing components with enhanced wear resistance and low coefficient of friction.Bidirectional(BD)satin weave polyacrylonitrile(PAN)based carbon fiber(Cf)fabric preform was successfully infiltrated with Al 6061 alloy by squeeze infiltration process.The infiltrated composite shows uniform distribution of carbon fibers in the matrix with the elimination of porosities,fiber damage and close control on the formation of deleterious aluminum carbide(Al4C3)phase.Cf/Al composite exhibits remarkable wear resistance compared to unreinforced alloy due to the formation of self-lubricating tribolayer on the pin surface,which intercepts the contact of matrix metal to counter surface.The BD carbon fiber enhanced the hardness and compressive strength of the composite by restraining the plastic flow behavior of matrix.High resolution transmission electron microscopy shows the presence of Al2O3 and MgAl2O4 spinel,confirmed by EDS and SAD pattern,at the composite interface.The composite shows a lower density of 2.16 g/cm^3 which is a major ad vantage for weight reduction compared to the monolithic alloy(2.7 g/cm^3).

关键词： Metal matrix composites Squeeze infiltration Aluminum Carbon fiber fabric Tribology Microstructure

Experimental and Computational Analysis of the Unstable Flow Structure in a Centrifugal Compressor with a Vaneless Diffuse

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 127-139页

作者： Xiang Xue Tong Wang Gas Turbine Research Institute Shanghai Jiao Tong University

The unstable flow phenomena in compressors, such as stall and surge, are closely related to the e ciency and the operating region. It is indispensable to capture the unstable flow structure in compressors and understand the mechanism of flow instability at low flow rates. Cooperated with the manufacturer, an industrial centrifugal compressor with a vaneless di user is tested by its performance test rig and our multi-phase dynamic measurement system. Many dynamic pressure transducers are circumferentially mounted on the casing surface at seven radial locations, spanning the impeller region and the di user inlet region. The pressure fields from the design condition to surge are measured in details. Based on the multi-phase dynamic signals, the original location of stall occurring can be determined. Meanwhile, the information of the unstable flow structure is obtained, such as the circumferential mode and the propagating speed of stall cells. To get more details of the vortex structure, an unsteady simulation of this tested compressor is carried out. The computational result is well matched with the experimental result and further illustrates how the unstable flow structure in the impeller region gradually a ects the stability of the total machine at low flow rates. The dynamic mode decomposition(DMD) method is applied to get the specific flow pattern corresponding to the stall frequency. Both experimental and computational analysis show that the flow structure at a particular radial location in the impeller region has a great impact on the stall and surge. Some di erences between the computational and experimental result are also discussed. Through these two main analytical methods, an insight into the unstable flow structure in an industrial compressor is gained. The result also plays a crucial role in the guidance of the compressor stabilization techniques.

关键词： Unstable flow Vortex structure Centrifugal compressor Vaneless diffuser

A New Methodology for Early Detection of Thermoacoustic Combustion Oscillations Based on Permutation Entropy

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Journal of Thermal Science 2023年第6期32卷 2310-2320页

作者： LI Yao HU Chunyan SHEN Youhao HAN Bo YANG Jinhu XU Gang Key Laboratory of Light Duty gas turbine Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China Innovation Academy for Light-Duty gas turbine Chinese Academy of SciencesBeijing100190China

We carry out a series of experimental investigations in a model combustor to detect a precursor of thermoacoustic combustion oscillations based on permutation entropy,which can amplify the subtle changes effected in the time sequence to identify the anomaly.By changing the flame’s location or the fuel flow to a value,an abrupt switch from aperiodic small-amplitude oscillations to periodic large-amplitude oscillations would occur in pressure fluctuations.The characteristic frequency of combustion oscillation is obtained by spectral analysis,with which a modified algorithm of the permutation entropy is proposed.The impact evaluation on key parameters such as moving step sizes and window sizes reveals that the moving data permutation entropy has strong robustness,and can accurately detect the onset of thermoacoustic oscillations.Further nonlinear analysis exhibits peculiar dynamics of the combustion system,which result in specific patterns in the time series and provide a theoretical basis for anomaly detection.Our results suggest that the permutation entropy has a certain potential in early warning and detection of combustion oscillations.

关键词： thermoacoustic combustion oscillation permutation entropy moving data anomaly detection precursors

Noise reduction for temperature-sensitive paint measurement contaminated by strong background radiation in a high enthalpy hypersonic tunnel

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Acta Mechanica Sinica 2021年第1期37卷 20-26,I0002页

作者： Di Peng Xu Liu Lingrui Jiao Ziyan Li Xin Wen Chaokai Yuan Guilai Han Yunfeng Liu Yingzheng Liu Zonglin Jiang Gas Turbine Research Institute/School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China institute of Mechanics Chinese Academy of SciencesBeijing100190China

The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings.We proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint(TSP)measurement in a hypersonic flow with Ma=6.5 and T_(0)=3525 K.The TSP was applied on an inlet ramp model,and the images were taken by a high-speed camera at 2 kHz under a modulated excitation.The strong background radiation led to a low signal-to-noise ratio and significant errors for the first half of the 130-ms test duration.Accordingly,three noise reduction methods were developed and evaluated based on temporal reconstruction,spatial reconstruction and robust principal component analysis(RPCA),respectively.The RPCA method showed the best performance that successfully recovered high-quality TSP data for a majority of test duration(t≥40 ms).

关键词： Temperature-sensitive paint Time-resolved measurement Hypersonic flow Background radiation

Experimental Study on Inducement and Development of Flow Instabilities in a Centrifugal Compressor with Different Diffuser Types

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Journal of Thermal Science 2020年第2期29卷 435-444页

作者： XUE Xiang WANG Tong Gas Turbine Research Institute Shanghai Jiao Tong UniversityShanghai 200240China

A centrifugal compressor is a typical compressed air energy storage device. In order to ensure the safety of the compressed energy storage process in the compressor, the internal unsteady flow phenomena need to be closely monitored, especially some serious ones like stall and surge. It is necessary to explore the mechanism of flow instabilities under different conditions. A centrifugal air compressor was tested with a vaneless diffuser and a variable vaned diffuser with five different vane setting angles, respectively. Various diffuser types resulted in various modes of flow instabilities prior to surge. The vaneless region between the impeller and the diffuser was focused on. Multiple high-speed sensors were arranged along the circumferential direction. The pressure signals at all these positions were being measured and collected in real time as the compressor was slowly throttled into surge. This paper emphasizes on the influence of matching between the impeller and the diffuser on the flow instability. The experimental results showed that the diffuser vane setting angle affected the stall characteristics. Due to the asymmetry of the volute, the circumferential pressure distribution was always severely distorted prior to surge. A high-pressure region appeared near the volute tongue, and a low-pressure region was formed away from the volute tongue. In the case of the vaned diffuser with non-design installation angle and the vaneless diffuser, the rotating stall signal was originated in the low-pressure region and propagated circumferentially. However, in the case of the vaned diffuser with the design installation angle, the circumferential high-pressure region became the most sensitive region for the generation of stall, and another form of instability occurred there. Both the inducement and development of these flow instabilities have been studied. The dynamic experimental research on the compressor matching different types of diffusers could be a good case supplement.

关键词： compressed air energy storage centrifugal compressor flow instability stall

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温敏漆应用于高超声速燃烧辐射环境的方法

Acta Mechanica Sinica 2023年第8期39卷 67-76页

作者：苑朝凯孟凡钊刘旭刘云峰连欢刘应征彭迪 institute of Mechanics Chinese Academy of Sciences Beijing China School of Engineering Science University of Chinese Academy of Sciences Beijing China Gas Turbine Research Institute/School of Mechanical Engineering Shanghai Jiao Tong University Shanghai China

热防护系统设计需要高空间分辨率的热流密度场测量方法来获取热流密度峰值及其对应的空间位置然而, 燃烧产生的背景辐射严重阻碍了现有热流密度场测量方法的应用. 为了解决该难题, 提出了一种适用于强辐射燃烧环境的热流密度场测... 详细信息

热防护系统设计需要高空间分辨率的热流密度场测量方法来获取热流密度峰值及其对应的空间位置然而, 燃烧产生的背景辐射严重阻碍了现有热流密度场测量方法的应用. 为了解决该难题, 提出了一种适用于强辐射燃烧环境的热流密度场测量方法, 基本思想是利用温敏漆测量燃烧室外壁面温度的变化历程结合三维瞬态热传导反问题的求解确定内壁面热流密度场分布. 文中详细介绍了测量系统构成、数据处理方法及温敏漆涂层厚度对测量结果的影响, 最后给出了数值和实验结果验证了该方法的可行性.

关键词：热传导反问题高空间分辨率辐射环境涂层厚度热防护系统密度峰值数据处理方法测量系统

Comparative Study on Different Methods for Prediction of Thermal Insulation Performance of Thermal Barrier Coating Used on turbine Blades

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Journal of Thermal Science 2024年第1期33卷 172-189页

作者： ZHANG Zhixin ZENG Wu ZHANG Xiaodong ZENG Yuntao Advanced gas turbine Laboratory Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Key Laboratory of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Innovation Academy for Light-duty gas turbine Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

As turbine inlet temperature gets higher and higher,thermal barrier coating(TBC) is more and more widely used in turbine blades.For turbine blades with TBC,it is of great significance to evaluate the temperature distribution of its substrate metal quickly and accurately,especially during the design stage.With different degrees of simplification such as whether to consider the change of the geometric size of the fluid domain by TBC and whether to consider the planar heat conduction in TBC,three different methods used in conjugate heat transfer(CHT) simulation to model the TBC of the turbine blades have been developed and widely used by researchers.However,little research has been conducted to investigate the influence of the three methods on the temperature distribution of turbine blade.To fill this gap,three geometric models were designed.They are a solid conduction model with a substrate metal layer and a TBC layer,a transonic turbine vane with internal cooling and TBC,and a plate cylindrical film hole cooling model with TBC.Different methods were used in these geometric models and their differences were carefully analyzed and discussed.The result shows that for the conduction model used in this paper,with the same TBC surface temperature distribution,the difference between the three methods is very small and can be ignored.For a transonic turbine vane with internal cooling,regarding the local maximum temperature of the substrate-TBC interface,the largest difference between the method in which TBC is considered as a thermal resistance or a virtual layer of cells and the method in which three-dimensional heat conduction equation of TBC is solved occurs at the trailing edge.The difference near the leading edge is below 2K.When employed to the film cooling model,the difference of the laterally averaged temperature of the substrate-TBC interface can be 8 K which is mainly due to the change of the length to diameter ratio of the film cooling hole by TBC.If the substrate thickness is reduced by the thickness of TBC wh

关键词： turbine blade thermal barrier coating conjugate heat transfer film cooling hole

Numerical Investigation of the Effects of Rising Angle on Intermediate turbine Duct and Nearby turbines

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Journal of Thermal Science 2017年第5期26卷 421-430页

作者： LIU Hongrui JI Lucheng LIU Jun DU Qiang LIU Guang WANG Pei DU Meimei School of Aerospace Engineering Beijing Institute of Technology Laboratory of Light-duty gas-turbine Institute of Engineering Thermophysics Chinese Academy of Sciences Petroleum Production Engineering research institute of Huabei Oilfield Company

In order to improve the efficiency, ultra-high bypass ratio engine attracts more and more attention because of its huge advantage, which has larger diameter low pressure turbine(LPT). This trend will lead to aggressive(high diffusion) intermediate turbine duct(ITD) design. It is necessary to guide the flow leaving high pressure turbine(HPT) to LPT at a larger diameter without any severe loss generating separation or flow disturbances. In this paper, eight ITDs with upstream swirl vanes and downstream LPT nozzle are investigated with the aid of numerical method. These models are modified from a unique ITD prototype, which comes from a real engine. Key parameters like area ratio, inlet height, and non-dimensional length of the ITDs are kept unchanged, while the rising angle(radial offset) is the only changed parameter which ranges from 8 degrees to 45 degrees. In this paper, the effects of rising angle(RA) on ITD, as well as nearby turbines, will be analyzed in detail. According to the investigation results, RA could be as large as 40 degrees in such model of this paper to escape separation; When RA increases, local inlet flow field of LPT nozzle appears to be with apparent variation; while a positive result is that outlet flow field could be kept almost unchanged through modifying blade profile. On the other hand, it seems optimistic that the overall total pressure loss could be kept nearly equivalent among different RA cases. And a valuable conclusion is that outer wall curvature is more important for pressure loss, which advises a clear direction for optimizing ITD.

关键词： Intermediate turbine Duct Rising Angle Flow Field Analysis

High temperature creep mechanisms of a single crystal superalloy: A phasefield simulation and microstructure characterization

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Progress in Natural Science:Materials International 2020年第3期30卷 366-370页

作者： Ronghai Wu Yunsong Zhao Yanfei Liu Xing Ai School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Beijing institute of Aeronautical Materials AECC Sichuan gas turbine Establishment AECC Hunan Aviation Power Plant research institute

The high temperature creep behavior of a single crystal Ni-based superalloy was studied by combined experimental and numerical methods. The creep test results showed that the creep curves exhibited a three-stage feature. The qualitative explanations for each stage of the creep curves were carried out based on the microstructure characterizations of γ/γ′ phases and dislocations. An elastoplasticity incorporated phase-field model was developed to provide quantitative understanding on directional coarsening(rafting) of γ′ phase. The simulation results showed that the directionality of γ′ coarsening was induced by both dislocation activity in γchannels and elastic inhomogeneity between γ and γ’ phases, therein the dislocation activity played a major role.This findings provide new insights into the design of novel single crystal superalloys with improved creep properties.

关键词： Creep mechanism Dislocation activity Phase-field method Single crystal superalloy