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Experimental Study of Effects of Tip Geometry on the Flow Field in a turbine cascade Passage

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Journal of Thermal Science 2015年第1期24卷 1-9页

作者： MA Hongwei WANG Lixiang National Key Laboratory of Science and Technology on Aero-Engines Collaborative Innovation Center of Advanced Aero-Engine School of Energy & Power Engineering Beihang University

This study investigates the effects of blade tip geometry on the flow field of a turbine cascade at the incidence angle of 0 degree experimentally. The tests were performed in a low-speed turbine cascade wind tunnel. The Reynolds number based on the blade chord was about 172300 at the exit. Traverses of the exit flow field were made in order to measure the overall performance. The effects of using fiat tip and grooved tip with a chord-wise channel were studied. The case with the flat tip is referenced as the baseline. The tip clearances are all 1 mm measuring 0.84 percent of the blade span. The depth of channel is *** flow field at 10% chord downstream from the cascade trailing edge was measured at 38 span-wise positions and 26 pitch-wise positions using a mini five-hole pressure probe. The static pressure distribution on the tip end wall is measured at 16 pitch-wise stations and 17 chord-wise stations. Results show that there exists great pressure gradient in the pressure side for the fiat tip and the pressure side squealer tip, which means strong leakage flow. The pressure gradient from the pressure side to the suction side is greatly decreased for the grooved tip, and the resulting leakage flow is weaker. The core of the leakage vortex moves closer to the suction side for the pressure side squealer tip and farther away from the suction side for the suction side squealer tip. The pressure side squealer has little advantages over the fiat tip in improving the flow capacity and reducing the overall losses. The suction side squealer tip and grooved tip can effectively decrease the intensity of the tip leakage vortex, improve the flow capacity and reduce loss of the turbine cascade passage and the grooved tip performs the best.

关键词： blade tip geometry turbine cascade flow field effect

Influences of Incidence Angle on 2D-Flow and Secondary Flow Structure in Ultra-Highly Loaded turbine cascade

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Journal of Thermal Science 2014年第1期23卷 13-21页

作者： Hoshio Tsujita Atsumasa Yamamoto Department of Mechanical Engineering Hosei University3-7-2Kajino-choKoganei-shiTokyo Japan

An increase of turbine blade loading can reduce the numbers of blade and stage of gas turbines. However, an increase of blade loading makes the secondary flow much stronger because of the steep pitch-wise pressure gradient in the cascade passage, and consequently deteriorates the turbine efficiency. In this study, the computations were performed for the flow in an ultra-highly loaded turbine cascade with high turning angle in order to clarify the effects of the incidence angle on the two dimensional flow and the secondary flow in the cascade passage, which cause the profile loss and the secondary loss, respectively. The computed results showed good agreement with the experimental surface oil flow visualizations and the blade surface static pressure at mid-span of the blade. The profile loss was strongly increased by the increase of incidence angle especially in the positive range. Moreover, the positive incidences not only strengthened the horseshoe vortex and the passage vortex but also induced a new vortex on the end-wall. Moreover, the newly formed vortex influenced the formation of the pressure side leg of horseshoe vortex.

关键词： turbine cascade Incidence Angle Numerical Analysis Secondary Flow

Topology and Vortex Structures of turbine cascade with Different Tip Clearances

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Chinese Journal of Aeronautics 2002年第1期15卷 18-26页

作者：韩万金杨庆海黄洪雁贾琳 Academy of Energy Science and Engineering Harbin Institute of Technology Harbin 150001 China

This paper uses the topology theory to analyze the surface flowspectrums of straight, positively curved and negatively curvedcascades with relative tip clearances of 0.023 and 0.036, findsapparent differences of topology and vortex structures in the bladetip and the suction side wall corner of single type of cascade withthis two clearances, and studies the mechanism of the differenceformation as well as their effects o the energy loss.

关键词： turbine cascade blade tip clearance flow visualization topology andvortex structures

Numerical investigation on the self-excited oscillation of wet steam flow in a supersonic turbine cascade

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Progress in Natural Science:Materials International 2006年第9期16卷 988-992页

作者： LI Liang, SUN Xiuling, LI Guojun and FENG Zhenping (School of Energy & Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China) School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The self-excited flow oscillation due to supercritical heat addition during the condensation process in wet steam turbine is an important issue. With an Eulerian/Eulerian model, the self-excited oscillation of wet steam flow in a supersonic turbine cascade is investigated . A proper inlet supercooling results in the transition from steady flow to self-excited oscillating flow in the cascade of steam turbine. The frequency dependency on the inlet supercooling is not monotonic. The flow oscillation leads to non-synchronous periodical variation of the inlet and outlet mass flow rate. The aerodynamic force on the blade varies periodically due to the self-excited flow oscillation. With the frequency lies between 18.1-80.64 Hz, the oscillating flow is apt to act with the periodical variation of the inlet supercooling due to sta-tor rotor interaction in a syntonic pattern, and results in larger aerodynamic force on the blade. The loss in the oscillating flow increases 20.64% compared with that in the steady flow.

关键词： self-excited oscillation wet steam turbine cascade condensation.

TOPOLOGY AND VORTEX STRUCTURES OF A CURVING turbine cascade WITH TIP CLEARANCE (Ⅱ)- TOPOLOGICAL FLOW PATTERN AND VORTEX STRUCTURE IN THE TRANSVERSE SECTION OF A BLADE cascade

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Applied Mathematics and Mechanics(English Edition) 2002年第8期23卷 958-962页

作者：杨庆海黄洪雁韩万今 Academy of Energy Science and Engineering Harbin Institute of Technology Harbin P R China

By means of ink trace visualization of the flows in conventional straight, positively curved and negatively curved cascades with tip clearance, and measurement of the aerodynamic parameters in transverse section, and by appling topology theory, the topological structures and vortex structure in the transverse section of a blade cascade were analyzed. Compared with conventional straight cascade, blade positive curving eliminates the separation line of the upper passage vortex, and leads the secondary vortex to change from close separation to open separation, while blade negative curving effects merely the positions of singular points and the intensities and scales of vortex.

关键词： turbine cascade tip clearance curving cascade transverse section flow field topological flow pattern and vortex structure

Investigation of Internal Flow in Ultra - Highly Loaded turbine cascade by PIV Method

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Journal of Thermal Science 2000年第3期9卷 193-198页

作者： A.Senoo S.MizukiandH.Tsujita 等 AllNipponAirwaysCo. Ltd.1－8－8HanedaAirportOta－kuTokyoJapan144－0041 Dept.ofMechanicalEngineering HoseiUniversity3－7－2Kajino－machiKoganeiTokyoJaPAN184－8584

The highly loaded turbine blades are able to reduce both the number of blades and the stages of turbojet-engines. In this study, PIV(Particle Image Velocimetry) method is used for the measurements of the secondary flow in ultra-highly loaded turbine blade cascades. The results obtained by the PIV method clearly show the complicated behavior of the secondary flow in the cascade. The horseshoe vortex and the passage vortex are observed inside the cascade. Moreover, the wake generated by the accumulation of the low energy fluid by the passage vortex near the suction side and that discharged toward downstream of the trailing edge has been recognized.

关键词： PIV turbine cascade secondary flow.

Experimental Investigations of the Three-DimensionalFlow in a Large Deflection turbine cascade with Tip Clearance

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Journal of Thermal Science 1998年第3期7卷 149-164页

作者： M.Govardhan S.S.S.R.K.Sastri V.S.Vishnubhotla ThermalurbomachinesLab DepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartmentofMechanicalEngineeringIndianInstituteofTechnologyMadrasChennai600036IndiaThermalurbomachinesLabDepartment

Results obtained from an experbontal study of the threedimensional flow survey within and exit of a large defiection linear turbine cascade are presented for a tip clearance levels of 0.08, 1.5, 3.0 percent of chord and compared with the help of boundary layer probes and that within and exit of a blade passage was done with a miniaturised five hole probe. End wall and blade tip surface static pressures were also obtained, in addition to flow visualisation studies. A strong horse-shoe vortex forms in front of the leading edge for zero clearance whereas this vortex does not appear for 3 percent clearance indicating that for large clearance the pressure forces have dominating infiuence than the viscous forces. In addition to normally known clearance vortex, a small tip separation vortex was noticed on the blade tip surface inside the tip gap. Due to the area contraction caused by the tip separation vortex, the fluid movign towards the tip gap from the pressure side is accelerated. Downstream of the vortex, the endwall pressure increases due to flow mixing. Both vortices increase in size and strength along the chord. The miring is incomplete in the aft portion of the blade. The tip gap velocity profiles exhibit wak like characteristics especially at axial positions where the mixing is incomplete. The passage vortex in the present investigations did not diminish with increase in clearance. The discharge coefhcient and the total pressure loss coefficient within the tip gap show similar tendency with lower values near the leading and trailing edge regions.

关键词： turbine cascade tip clearance vortex tip separation vortex horse-shoe vor-tex total pressure loss coefficient discharge coefficient

Effect of Streamwise Fences on Secondary Flows and Losses in a Twodimensional turbine Rotor cascade

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Journal of Thermal Science 2006年第4期15卷 296-305页

作者： M.Govardhan A.Rajender J.P.Umang Thermal Turbomachines Laboratory Department of Mechanical EngineeringIndian Institute of Technology MadrasChennai 600036India

To control secondary flows, streamwise fences were attached to end wall of a linear turbine rotor cascade. The cascade had 8 blades of 400 mm long and 175 mm chord. The blades deflected the flow by 120°. The fences were made out of 0.7 mm thick brass sheet and the heights of the fences were 14 mm, 18 mm respectively. The curvature of the fences was the same as that of the blade camber line. The fences were fixed normal to the end wall and at half pitch away from the blades. The experimental program consists of total pressure, static pressure measurements at the inlet and outlet of the cascade, by using five-hole probe. In addition, static pressure on the blade suction surface and pressure surface was also obtained. Fences are effective in preventing the movement of the pressure side leg of the horseshoe vortex. Consequently the accumulation of low energy fluid on the suction surface is minimised. End wall losses are reduced by the fences due to weakening of the end wall cross flow.

关键词： turbine cascade streamwise fences loss core lift coefficient

Experimental Investigation of Aerodynamic Performance due to Blade Tip Clearance in a Gas turbine Rotor cascade

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Journal of Thermal Science 2022年第1期31卷 173-178页

作者： CHUNG Jinmoo BAEK Seungchan HWANG Wontae Department of Mechanical Engineering Seoul National UniversitySeoul 08826Republic of Korea Institute of Advanced Machines and Design Seoul National UniversitySeoul 08826Republic of Korea Institute of Engineering Research Seoul National UniversitySeoul 08826Republic of Korea

This study examines how the complex flow structure within a gas turbine rotor affects aerodynamic loss. An unshrouded linear turbine cascade was built, and velocity and pressure fields were measured using a 5-hole probe. In order to elucidate the effect of tip clearance, the overall aerodynamic loss was evaluated by varying the tip clearance and examining the total pressure field for each case. The tip clearance was varied from 0% to 4.2% of blade span and the chord length based Reynolds number was fixed at 2×10^(5). For the case without tip clearance, a wake downstream of the blade trailing edge is observed, along with hub and tip passage vortices. These flow structures result in profile loss at the center of the blade span, and passage vortex related losses towards the hub and tip. As the tip clearance increases, a tip leakage vortex is formed, and it becomes stronger and eventually alters the tip passage vortex. Because of the interference of the secondary tip leakage flow with the main flow, the streamwise velocity decreases while the total pressure loss increases significantly by tenfold in the last 30% blade span region towards the tip for the 4.2% tip clearance case. It was additionally observed that the overall aerodynamic loss increases linearly with tip clearance.

关键词： gas turbine turbine cascade aerodynamic loss tip clearance tip leakage