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Numerical Analysis and PIV Measurements of tip Vortex in an Axial Rotor with Skewed-Swept Blade at Its Leading Edge

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Journal of Thermal Science 2004年第1期13卷 16-23页

作者： Guanghui Wu Lijie Zheng Keqi Wu Huazhong Univ Sci & Technol Sch Energy & Power Engn Wuhan 430074 Peoples R China

Based on the characteristics of axial fans of outdoor units of centralized air-conditioners, using the finite-volume method, applying three-dimensional steady Reynolds-averaged Navier-Stokes equations coupled with Spalart-Allmaras turbulence model equation, and adopting SIMPLE algorithm, numerical analysis is made and applied to analyze the internal flow field of axial rotors with skewed-swept blade at its leading edge. This numerical simulation mainly investigates the formation and development of the tip vortex. Based on the tip vortex characteristics that have been captured, the internal flow numerical results are compared with those obtained by the PIV experiments. This comparison indicates a good agreement between numerical results and PIV results, thus proving the validity of the numerical simulation. In addition, based on the internal flow analyses of the axial rotor with skewed-swept blade at its leading edge, different flow phenomena features are presented. These flow features can be used for further improvements of the present rotor performance characteristics.

关键词： axial rotor with skewed-swept blade at its leading edge numerical simulation tip vortex PIV experiment

Investigation of the Unsteady Disturbance in tip Region of a Contra-Rotating Compressor near Stall

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Journal of Thermal Science 2019年第5期28卷 962-974页

作者： CHEN Weixiong WANG Yangang WANG Hao School of Power and Energy Northwestern Polytechnical University

The present study investigated the spectrum characteristics of unsteady disturbance and the tip leakage vortex evolution during pre-stall process for a contra-rotating axial compressor(CRAC). Transient numerical simulation was carried out in a single passage of the CRAC. The original transient fluctuation and oscillation of the tip leakage vortex structure with varying flow capacity of the CRAC were revealed using circle-like pattern figure and phase-locked root mean square(PLRMS). Additionally, the tip leakage flow in terms of vortex structure evolution was visualized for the sake of revealing the flow mechanism during pre-stall process. Results show that the unsteady fluctuation first appears at φ=0.3622, and the fluctuation frequency is 2.86 BPF. Unsteady disturbance source is mainly located at the tip side of the downstream rotor leading edge. From the choking point to the near stall condition, tip leakage vortex is always found in the tip leading edge of the upstream rotor. In addition, the tip leakage vortex of upstream rotor remains in the same place over time, i.e., no fluctuation, even when the downstream rotor entered into stall state. Such a phenomenon indicates that the stall point of the contra-rotating compressor is determined by the downstream rotor. Moreover, the maximum fluctuation position is mainly concentrated on the interface between the mainstream and the tip leakage vortex of the downstream rotor. By throttling the compressor, the angle between the main leakage vortex and the circumferential direction decreases gradually. When the main leakage vortex touches and continuously impacts on the leading edge of the adjacent blade, the unsteady disturbance, which is different from that of BPF, appears firstly.

关键词： contra-rotating axial compressor blade passing frequency tip leakage flow unsteady disturbance source phase-locked RMS

Study on leakage flow characteristics of radial inflow turbines at rotor tip clearance

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Science China(Technological Sciences) 2008年第8期51卷 1125-1136页

作者： DENG QingHua NIU JiuFang FENG ZhenPing Institute of Turbomachinery Xi’an Jiaotong UniversityXi’an 710049China

tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow caused by relative motion between casing and rotor tip, and the pressure difference between pressure side and suction side at rotor tip, play important roles in tip clearance leakage flow. The more the rotor tip speed increases and tip clearance height decreases, the more the scraping effect acts. Though the leakage velocity of tip clearance at midsection and exducer regions changes less when the rotor rotational speed is changing, the distance between passage vortex and rotor suction side varies in evidence. Main leakage flow rate of tip clearance takes place at region of exducer tip and some seal configurations will be quite effective for cutting leakage flow if these configurations are arranged over midsection and exducer of the radial inflow rotor.

关键词： microturbine radial inflow turbine rotor tip clearance

Investigation on meshing and dynamic characteristics of spur gears with tip relief under wear fault

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Science China(Technological Sciences) 2019年第11期62卷 1948-1960页

作者： HUANGFU YiFan CHEN KangKang MA Hui LI Xu YU Xi ZHAO BaiShun WEN BangChun School of Mechanical Engineering and Automation Northeastern UniversityShenyang 110819China Key Laboratory of Vibration and Control of A ero~Propulsion Systems Ministry of Education of ChinaNortheastern UniversityShenyang 110819China Sate Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Combining the loaded tooth contact analysis(LTCA)method and the gear dynamic model,a wear prediction model for spur gears with tip relief is *** simulated wear depth is verified by the experimental results in a published *** on the wear profile,the mesh stiffness and the tooth root stress obtained from the proposed model are compared with those obtained from the finite element *** to the finite element method,the proposed method can greatly reduce the computation *** effects of the tip relief and surface wear on the meshing and the dynamic characteristics are *** tip relief can greatly decelerate the surface *** tip relief and slight wear can decrease the tooth interference and reduce the system ***,the effects of the rotational speed on the wear depth are also studied and it is found that the quasi-static model is applicable to wear prediction when the rotational speed is away from the harmonic resonance peak.

关键词： spur gears tip relief surface wear mesh stiffness dynamic characteristics

Research on active disturbance rejection control method for turbine blade tip clearance

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Science China(Technological Sciences) 2019年第10期62卷 1795-1804页

作者： WANG WeiMin SHAO Xing LI QiHang Gao JinJi HAO ZeRui Beijing Key Laboratory of Health Monitoring and Self-Recovery for High-End Mechanical Equipment Beijing University of ChemicalTechnologyBeijing100029China Department of Mechanical Engineering Tsinghua UniversityBeijing100084China

Blade tip clearance(BTC) is one of the key factors affecting the efficiency and reliability of high performance turbomachinery such as heavy duty steam turbines, aircraft engines and other gas turbo machines. The self-adjusting ability of BTC according to the operation condition changing is important to meet the requirement of performance. In this paper, the principle and method of adjusting the BTC by controlling the axial displacement of the rotor were proposed and studied. The basic principle is that the BTC of the turbomachinery with a conical tail shroud will be affected by the axial displacement of rotor and thereby can be adjusted by controlling the axial position of rotor, which can be adjusted by the controllable oil pressure acting on the thrust bearing. To reach a higher control precision, lower noise and model perturbation, an adaptive quasi-sliding mode control(AQSMC) algorithm based on the disturbance observer(DOB) was designed, and numerical and experimental investigations were carried out. The numerical simulation results show that this algorithm can not only effectively suppress the disturbance, but also, compared with the general reaching law, effectively reduce the chattering and transient high gain switching effect of the closed-loop controller system and avoid the instability caused by the controller. Based on the DOB-AQSMC algorithm, the BTC was stabilized within 2 s with no overshoot and no misalignment in the test rig, and this algorithm achieves a better control performance than the proportion-integral-differential(PID) algorithm. These achievements can be used to push forward the intelligent turbomachinery development.

关键词： blade tip clearance turbomachinery active disturbance rejection control DOB-AQSM method

Numerical Simulation of Aerodynamic Characteristics of Helicopter Rotor with tip Slots

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第6期35卷 942-951页

作者： Chen Rongqian Wang Xu Cheng Qiyou Zhu Chengxiang You Yancheng School of Aerospace Engineering Xiamen UniversityXiamen 361005P.R.China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412002P.R.China Science and Technology on Rotorcraft Aeromechanics Laboratory China Helicopter Research and Development InstituteJingdezhen 333001P.R.China

Effects of tip slots on the aerodynamic characteristics of helicopter rotor were investigated numerically by solving three-dimensional Navier-Stokes equations based on unstructured overset grids *** delayed detached eddy simulation (IDDES) based on the Spalart-Allmaras turbulence model and adaptive grid refinement technique were *** slots in the rotor blade tip were designed on the base of Caradonna-Tung rotor to study the effect of tip *** results show that tip slots are able to introduce the airflow from the leading edge and turn it in the spanwise direction to be ejected out of the face at the rotor blade tip,which can reduce the strength of the rotor blade tip vortex and accelerate the dissipation *** tip slots may lead to the decrease of airfoils' lift coefficient at the root of the rotor blade,it can increase the lift coefficient of airfoils at the rotor blade tip,so the lift of the rotor with tip slots is almost the same as that of the rotor without tip *** addition,tip slots can also reduce the intensity of the tip shock wave,which is beneficial to reduce the wave drag of the rotor.

关键词： tip slots tip-vortex alleviation helicopter rotor numerical simulation

Experimental study about nano-deformation field near quasi-cleavage crack tip

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Science China Mathematics 2000年第9期43卷 963-968页

作者：邢永明戴福隆杨卫FML Department of Engineering Mechanics Tsinghua University Beijing 100084 China

Using the nano-moiré method, we measure the near tip nanoscopic deformation on the [111] plane of single crystal silicon with a loaded quasi-cleavage crack running in the [110] direction. The measured strain distribution ahead of the crack tip agrees with the linear elastic fracture mechanics prediction up to 10 nm from the crack tip. Dislocations of Peierls type are detected and they extend from the crack tip over a length of hundreds of Burgers vectors.

关键词： nano-moiré method brittle materials crack tip Peierls dislocation deformation.

Investigation of atomic structure ahead of crack tip by STM and AFM

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Science China(Technological Sciences) 1998年第4期41卷 411-417页

作者：李晓冬王燕斌褚武扬王琛白春礼 1. Department of Materials Physics University of Science and Technology Beijing 100083 Beijing China 2. Institute of Chemistry Chinese Academy of Sciences 100080 Beijing China

The nanostructure and atomic structure ahead of the crack tip of highly oriented pyrolytic graphite has been studied by using scanning tunneling microscopy (STM) and that of mica by using atomic force microscopy (AFM). There are many small voids or vacancy clusters ahead of the crack tip, which can migrate with time and result in the crack tip propagating because of the interaction force between the STM pinpoint and the sample. The nanostructure and atomic structure of loaded crack tip on (001) surface of mica has been observed by AFM. The results show that there exists a severely distorted region about 10 nm in width ahead of the loaded crack tip, and in this region there are many vacancies and vacancy clusters. Around this region there is an abnormal elastic region about 110 nm in width.

关键词： STM AFM crack tip atomic image abnormal elastic region.

Research on a Diamond tip Wear Mechanism in Atomic Force Microscope-based Micro/nano-machining

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High Technology Letters 2001年第3期7卷 84-89页

作者：赵清亮 Precision Eng. Research Institute Harbin Institute of Technology Harbin 150001 China

The object is to investigate the wear of an atomic force microscope (AFM) diamond tip when conducting micro/nano machining on single crystal silicon surface. The experimental research and theoretical analysis were carried out on the worn tip in terms of wear rate, wear mechanism and the effect of the tip wear on micro machining process. The wear rate was calculated as 1.7(10～10mm 3/(N·m) by using a theoretical model combined with the experimental results. Through an integration of an AFM observation on the worn tip features with the FEM simulation of the stress distribution, in addition to the unit cutting force calculation on the AFM diamond tip, the wear mechanism of the AFM diamond tip was concluded as mainly chemical wear, and the wear process was also elaborated as well.

关键词： Atomic force microscope diamond tip single crystal silicon micro/nano machining chemical wear