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Numerical and experimental study of bleed impact in multistage axial compressors

Chinese Journal of Aeronautics 2023年第2期36卷 1-16页

作者： Baojie LIU Xinwei ZHUANG Guangfeng AN xianjun yu Research Institute of Aero-Engine Beihang UniversityBeijing 100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics Beijing 100191China School of Energy and Power Engineering Beihang UniversityBeijing 100191China

In this study,the influence of inter-stage bleeding on the compressor performance and inter-stage flow field of a multistage axial compressor is investigated by both experimental and numerical *** experiment is conducted on a four-stage low-speed axial compressor,and a specific computational model is built to simulate the experiment environment *** illuminate the fluid mechanisms of bleeding effect in detail,both the experiment and the simulation are carried out twice,i.e.,in the first time,the mass flow rate upstream the bleed location is constant under different bleed rate conditions;while in the second time,the mass flow rate downstream the bleed location is constant under different bleed rate *** results demonstrate that inter-stage bleeding has little influence on upstream compressor characteristics,and affects the upstream flow field only in the rear half of the *** bleed effect on the downstream flow field is embodied in the variation of an incoming flow profile,an increase as the compressor inlet flow coefficient ***,such an effect is only significant on compressor characteristics at small flow coefficient *** multistage compressors,the variation of compressor characteristics and flow field caused by inter-stage bleeding is the comprehensive result of the bleeding and the variation of the upstream working *** addition,the comparison between numerical and experimental results shows that the flow moves towards top half of span through the downstream rotor passage in the numerical simulation,whereas the trend of flow field variation with different bleed rates at the outlet of the downstream rotor and stator is the same with that at the inlet of the downstream rotor in the experiment,which means that the numerical method has overestimated the radial mixing intensity of the flow.

关键词： Compressor characteristics Inter-stage bleeding Low-speed compressor experiment Multistage axial compressor Spanwise mixing

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Modeling of the Double Leakage and Leakage Spillage Flows in Axial Flow Compressors

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Journal of Thermal Science 2014年第2期23卷 103-113页

作者： DU Hui yu xianjun LIU Baojie National Key Laboratory of Science & Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power EngineeringBeihang University

A model to predict the double leakage and tip leakage leading edge spillage flows was developed. This model was combined by a TLV trajectory model and a TLV diameter model and formed as a function of compressor one-dimensional design parameters, i.e. the compressor massflow coefficient, Ф and compressor loading coeffi- cient, ψ, and some critical blade geometrical parameters, i.e. blade solidity, a, stagger angle, βs, blade chord length, C, and blade pitch length, S. By using this model, the double leakage and tip leakage leading edge spillage flow could be predicted even at the compressor preliminary design process. Considering the leading edge spillage flow usually indicates the inception of spike-type stall, i.e. the compressor is a tip critical design, this model could also be used as a tool to choose the critical design parameters for designers. At last, some experimental data from literature was used to validate the model and the results proved that the model was reliable.

关键词： tip leakage vortex double leakage leading edge spillage flow modeling axial compressor turbo-machinery

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Method for utilizing PIV to investigate high curvature and acceleration boundary layer flows around the compressor blade leading edge

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Chinese Journal of Aeronautics 2022年第12期35卷 72-88页

作者： Baojie LIU Xiaobin XU xianjun yu Guangfeng AN Research Institute of Aero-Engine Beihang UniversityBeijing 100083China National Key Laboratory of Science&Technology on Aero-Engine Aero-Thermodynamics Beihang UniversityBeijing 100083China School of Energy and Power Engineering Beihang UniversityBeijing 100083China

Particle Image Velocimetry(PIV)is a well-developed and contactless technique in experimental fluid mechanics,but the strong velocity gradient and streamline curvature near the wall substantially limits its accuracy *** paper presents a data processing procedure combining conventional PIV and newly developed Mirror Interchange(MI)based Interface-PIV for the measurement of the boundary layer parameter development in the blade leading edge *** synthetic particle images are used to analyze the measurement errors in the entire ***,three types of errors,namely the errors caused by the Window Deformation Iterative Multigrid(WIDIM)algorithm,the discrete data interpolation and integration,and the wall offset uncertainty,comprise the main measurement ***,the errors due to the discrete data interpolation and integration and the WIDIM algorithm comprise the mean bias,which can be corrected through the error analysis method proposed in the present ***,the errors due to the WIDIM algorithm and the wall offset uncertainty contribute to the measurement *** fluid dynamics-based synthetic particle flows were generated to verify the newly developed PIV data processing procedure and the corresponding error analysis *** showed that the data processing method could improve the accuracy of PIV measurements for boundary layer flows with high curvature and acceleration and even with significant flow separation ***,the data processing method is also applied in a PIV experiment to investigate the boundary layer flows around a compressor blade leading edge,and several credible boundary flow parameters were obtained.

关键词： Boundary layer measurement Compressor blade leading edge Mirror interchange method Particle image velocimetry Planar cascade experiment

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Exploration of acceptable operating range for a compression system in a double bypass engine

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Chinese Journal of Aeronautics 2023年第9期36卷 111-122页

作者： Ruoyu WANG xianjun yu Baojie LIU Guangfeng AN Research Institute of Aero-Engine Beihang UniversityBeijing 102206China National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics Beijing 102206China

The variable cycle engine is distinguished by its highly adjustable compression system,whose aerodynamic characteristic is extremely *** explore the regulation range of a double bypass engine compression system,a multi-dimensional analysis method is developed,through which the coupling mechanism between the compressor component and the bypass is *** operation zones of the compressor components and the bypass system are proposed,and the operation range of the compression system is obtained by calculating the overlapping part of the operation *** results show that in the double bypass mode,there exists a minimum mode selector valve area and a minimum core driven fan stage stall margin that ensures a feasible bypass flow,the two parameters correspond to each *** the given fan and core driven fan stage conditions,the maximum value of the inner bypass ratio is restricted by the upper limit of the forward variable area bypass injector and the maximum Mach number in the total bypass,while the minimum value of the inner bypass ratio depends on the lower limit of the forward variable area bypass injector geometry and the system recirculation *** single bypass mode is a unique condition of the double bypass mode,as the operation zone of the compressor component degenerates from a two-dimensional surface to a straight *** are multiple bypass states available in the single bypass mode,while the regulation range of the bypass ratio is jointly restricted by the operation range of the high pressure compressor and the aerodynamic boundary of the forward variable area bypass injector.

关键词： Compression system Coupling effect Matching mechanism Multi-dimensional method Operation range Variable cycle engine

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Relationship between the Flow Blockage of Tip Leakage Vortex and its Evolutionary Procedures inside the Rotor Passage of a Subsonic Axial Compressor

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Journal of Thermal Science 2013年第6期22卷 522-531页

作者： DU Hui yu xianjun ZHANG Zhibo LIU Baojie National Key Laboratory of Science & Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power EngineeringBeihang University

The near casing flow fields inside the rotor passage of a 1.5 stage axial compressor with different blade-loading levels and tip gap sizes were measured by using stereoscopic particle image velocimetry(SPIV). Based on a carefully defined blockage extracting method, the variations of blockage parameter inside the blade passage were analyzed. It was found that the variation of blockage parameter appeared as a non-monotonic behavior inside the blade passage in most cases. This non-monotonic behavior became much more remarkable as the blade loading increases or mass flow rate *** variations of the blockage parameter inside the blade passage had close relation to the evolutionary procedures of the tip leakage vortex(TLV). The destabilization of the TLV caused a rapid increasing of the blockage parameter. After the TLV lost the features of a concentrated streamwise vortex,the blockage parameter usually got a peak value. And then, because of the intense turbulent mixing between the TLV low momentum flow and its surrounding flows, the flow deficit inside the TLV recovered.

关键词： tip leakage vortex flow blockage unsteady flow axial compressor turbomachinery

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Using tandem blades to break loading limit of highly loaded axial compressors

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Chinese Journal of Aeronautics 2022年第4期35卷 165-175页

作者： Baojie LIU Chuanhai ZHANG Guangfeng AN Du FU xianjun yu Research Institute of Aero-Engine Beihang UniversityBeijing 100083China School of Energy and Power Engineering Beihang UniversityBeijing 100083China Gree Electric Appliances Inc.of ZhuhaiZhuhai 519070China

It is confirmed that tandem-blade configurations have potential to enlarge the flow turning in two-dimension(2D) studies. However, the potential of tandem blades to enlarge the design space for highly loaded axial compressors was rarely investigated in open literatures. The present work aims to show the capability of tandem blades to break the loading limit of conventional blades for highly loaded compressors. The 2D models of the maximum static pressure rise derived in previous work were validated by a large amount experimental data, which showed a good agreement. An E parameter was defined to evaluate the stall margin of compressor based on the theoretical models, which indicated that the tandem blade was able to increase the loading limit of axial compressors. A single-blade stage with a loading coefficient of 0.46(based on the blade tip rotating speed) was designed as the baseline case under the guidance of the E parameter. A tandem-blade stage was then designed by ensuring that the velocity triangles were similar to the single-blade stage. The performances of both stages were investigated experimentally. The results showed that the maximum efficiency of the tandem-blade stage was 92.8%, 1% higher than the single;the stall margin increased from 16.9% to 22.3%. Besides, the maximum pressure rise of tandem rotors was beyond the loading limit of 2D single-blade cascades, which confirmed the potential of tandem blades to break the loading limit of axial compressors.

关键词： Cascades Highly loaded axial compressors Loading limit Single blades Tandem blades

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Breaking the geometry-performance tradeoff in compressor deviation modeling:Nested principal component analysis

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Chinese Journal of Aeronautics 2024年第9期37卷 131-149页

作者： Mingzhi LI xianjun yu Dejun MENG Guangfeng AN Baojie LIU Research Institute of Aero-Engine Beihang UniversityBeijing 100191China National Key Laboratory of Science&Technology on Aero-Engine Aero-Thermodynamics Beihang UniversityBeijing 100191China AECC Shenyang Engine Research Institute Shenyang 110015China

Uncertainties in the aerodynamic performance of compressors,introduced by manufacturing variations,have received more and more attentions in recent *** deviation model plays a crucial role in evaluating this uncertainty and facilitating robust ***,current deviation models with a few variables cannot simultaneously achieve a precise geometric approximation of deviation and provide an accurate assessment of performance *** paper introduces a novel deviation modeling method named Nested Principal Component Analysis(NPCA)to break this *** this method,both geometry-based and performance-based modes are utilized to describe manufacturing *** considering aerodynamic sensitivity,surface deformations that significantly impact aerodynamic performance can be extracted for deviation *** demonstrate the superiority of this newly proposed method,ninety-eight newly manufactured compressor rotor blades were measured using a coordinate measurement machine,and both NPCA and Principal Component Analysis(PCA)were employed to model the real manufacturing *** results indicate that,in comparison to the PCA method,the NPCA method achieves an equivalent level of accuracy in geometric reconstruction and evaluation of mean ***,the same level of accuracy can be obtained with eight NPCA modes and fifty PCA modes when assessing the scatter in aerodynamic ***,the working mechanism of the NPCA method for accurate uncertainty quantification was further investigated.

关键词： Manufacturing variation Uncertainty quantification Dimension reduction Aerodynamics Flow mechanism

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Development of a deviation package method for low-cost robust optimization in compressor blade design

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Chinese Journal of Aeronautics 2024年第4期37卷 166-180页

Manufacture variations can greatly increase the performance variability of compressor blades. Current robust design optimization methods have a critical role in reducing the adverse impact of the variations, but can be affected by errors if the assumptions of the deviation models and distribution parameters are inaccurate. A new approach for robust design optimization without the employment of the deviation models is proposed. The deviation package method and the interval estimation method are exploited in this new approach. Simultaneously, a stratified strategy is used to reduce the computational cost and assure the optimization accuracy. The test case employed for this study is a typical transonic compressor blade profile, which resembles most of the manufacture features of modern compressor blades. A set of 96 newly manufactured blades was measured using a coordinate measurement machine to obtain the manufacture variations and produce a deviation package. The optimization results show that the scatter of the aerodynamic performance for the optimal robust design is 20% less than the baseline value. By comparing the optimization results obtained from the deviation package method with those obtained from widely-used methods employing the deviation model, the efficiency and accuracy of the deviation package method are demonstrated. Finally, the physical mechanisms that control the robustness of different designs were further investigated, and some statistical laws of robust design were extracted.

关键词： Manufacture variations Robust design optimization Compressor leading edge Aerodynamics Physical mechanism

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New insights into component matching mechanism in the compression system of double bypass engine

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Propulsion and Power Research 2024年第1期13卷 118-131页

作者： Ruoyu Wang xianjun yu Baojie Liu Guangfeng An Research Institute of Aero-Engine Beihang UniversityBeijing 100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics Beihang UniversityBeijing 100191China

Variable cycle engine(VCE)is one of the most promising technologies for the next-generation aircraft,the matching of different components in the compression system is a key difficulty VCE *** investigate the component matching mechanisms in the VCE compression system,an advanced throughflow program is employed to calculate the characteristic lines of each component,and a zero-dimensional method is developed to cap-ture the component performance deviation during the coupling working *** setting the compressor stall and choke conditions as the boundary,the operation range of the compression system isfirst clarified,and the aerodynamic performance in the operation zone is discussed,thus providing a theoretical basis for optimization of the engine operating con-trol *** show that the efficiency of the coreflow is optimum at the left-bottom corner of the operation region,while the total pressure ratio peaks at the right-top area,hence a balance is needed when deciding the matching *** of component control pa-rameters will change the position of the operation zone,as well as the corresponding aerody-namic *** the core driven fan stage rotating speed can improve the total bypass ratio,yet the total pressure ratio of the coreflow will be *** the core driven fan stage inlet guide vane can increase the total bypass ratio without changing the core flow aerodynamic performance *** bypass ratio of the compression system can also be increased by increasing the fan stall margin or decreasing its rotating speed,both ways will decrease the total pressure ratio of the core *** of the study will benefit the variable cycle engine design process in operation point evaluation and thermodynamic cycle optimization.

关键词： Matching analysis Double bypass engine Compression system Operation zone Aerodynamic performance

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Epigenetic regulation in the tumor microenvironment:molecular mechanisms and therapeutic targets

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Signal Transduction and Targeted Therapy 2023年第6期8卷 2795-2820页

作者： Jing Yang Jin Xu Wei Wang Bo Zhang xianjun yu Si Shi Department of Pancreatic Surgery Fudan University Shanghai Cancer CenterShanghaiChina Department of Oncology Shanghai Medical CollegeFudan UniversityShanghaiChina Shanghai Pancreatic Cancer Institute ShanghaiChina Pancreatic Cancer Institute Fudan UniversityShanghaiChina

Over decades,researchers have focused on the epigenetic control of DNA-templated *** modification,DNA methylation,chromatin remodeling,RNA modification,and noncoding RNAs modulate many biological processes that are crucial to the development of *** of the epigenome drives aberrant transcriptional programs.A growing body of evidence suggests that the mechanisms of epigenetic modification are dysregulated in human cancers and might be excellent targets for tumor *** has also been shown to influence tumor immunogenicity and immune cells involved in antitumor ***,the development and application of epigenetic therapy and cancer immunotherapy and their combinations may have important implications for cancer ***,we present an up-to-date and thorough description of how epigenetic modifications in tumor cells influence immune cell responses in the tumor microenvironment(TME)and how epigenetics influence immune cells internally to modify the ***,we highlight the therapeutic potential of targeting epigenetic regulators for cancer *** the complex interplay between epigenetics and cancer immunology to develop therapeutics that combine thereof is challenging but could yield significant *** purpose of this review is to assist researchers in understanding how epigenetics impact immune responses in the TME,so that better cancer immunotherapies can be developed.

关键词： therapeutic mechanisms template

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