• Title/Summary/Keyword: Secondary Flow and Loss

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The Experimental Investigation of the Secondary Flow and Losses Within the Plane Turbine Cascade Passage (선형터빈 케스케이드 통로내의 2차 유동과 손실에 관한 연구)

  • 이기백;양장식;나종문
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.784-795
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    • 1995
  • This paper represents the results of the experiments of the three-dimensional flow and the aerodynamic loss caused by the three-dimensional flow within the plane bucket blades. To research the secondary flow and the aerodynamic loss, the large-scale plane bucket blade of lst-stage in the low pressure steam turbine is made of FRP. The detailed investigation of the secondary flow and the aerodynamic loss using 5-hole pressure probe within turbine cascade has been carried out in the low speed wind tunnel. The limiting streamlines of the suction and endwall surface have been visualized by the oil film method. The flow visualization of the secondary flow has been performed by the laser light sheet technique and image processing system. By using the method mentioned above, it is possible to observe the evolution of the pitchwise mass-averaged flow deviation angle and total pressure loss coefficient, the secondary flow, and the aerodynamic loss through the cascade.

Tip Clearance Effect on Through-Flow and Performance of a Centrifugal Compressor

  • Eum, Hark-Jin;Kang, Young-Seok;Kang, Shin-Hyoung
    • Journal of Mechanical Science and Technology
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    • v.18 no.6
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    • pp.979-989
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    • 2004
  • Numerical simulations have been performed to investigate tip clearance effect on through-flow and performance of a centrifugal compressor which has the same configuration of impeller with six different tip clearances. Secondary flow and loss distribution have been surveyed to understand the flow mechanism due to the tip clearance. Tip leakage flow strongly interacts with mainstream flow and considerably changes the secondary flow and the loss distribution inside the impeller passage. A method has been described to quantitatively estimate the tip clearance effect on the performance drop and the efficiency drop. The tip clearance has caused specific work reduction and additional entropy generation. The former, which is called inviscid loss, is independent of any internal loss and the latter, which is called viscous loss, is dependent on every loss in the flow passage. Two components equally affected the performance drop as the tip clearances were small, while the efficiency drop was influenced by the viscous component alone. The additional entropy generation was modeled with all the kinetic energy of the tip leakage flow. Therefore, the present paper can provide how to quantitatively estimate the tip clearance effect on the performance and efficiency.

Experimental Study on Effects of Inlet Boundary Layer Thickness and Boundary Layer Fence in a Turbine Cascade (터빈 캐스케이드 입구경계층 두께와 경계층 펜스 효과에 대한 실험적 연구)

  • Jun, Y.M.;Chung, J.T.
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.853-858
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    • 2000
  • The working fluid from the combustor to the turbine stage of a gas turbine makes various boundary layer thickness. Since the inlet boundary layer thickness is one of the important factors that affect the turbine efficiency. It is necessary to investigate secondary flow and loss with various boundary layer thickness conditions. In the present study, the effect of various inlet boundary layer thickness on secondary flow and loss and the proper height of the boundary layer fences for various boundary layer thickness were investigated. Measurements of secondary flow velocity and total pressure loss within and downstream of the passage were taken under 5 boundary layer thickness conditions, 16, 36, 52, 69, 110mm. It was found that total pressure loss and secondary flow areas were increased with increase of thickness but they were maintained almost at the same position. At the fellowing research about the boundary layer fences, 1/6, 1/3, 1/2 of each inlet boundary layer thickness and 12mm were used as the fence heights. As a result, it was observed that the proper height of the fences was generally constant since the passage vortex remained almost at the same position. Therefore once the geometry of a cascade is decided, the location of the Passage vortex and the proper fence height are appeared to be determined at the same time. When the inlet boundary layer thickness is relatively small, the loss caused by the proper fence becomes bigger than endwall loss so that it dominates secondary loss. In these cases the proper fence hight is decided not by the cascade geometry but by the inlet boundary layer thickness as previous investigations.

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An experimental study on the secondary flow and losses in turbine cascades (익렬 통로 내의 2차유동 및 손실에 관한 실험 연구)

  • Jeong, Yang-Beom;Sin, Yeong-Ho;Kim, Sang-Hyeon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.1
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    • pp.12-24
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    • 1998
  • The paper presents the mechanism of secondary flows and the associated total pressure losses occurring in turbine cascades with turning angle of about 127 and 77 degree. Velocity and pressure measurements are taken in seven traverse planes through the cascade passage using a prism type five hole probe. Oil-film flow visualization is also conducted on blade and endwall surfaces. The characteristics of the limiting streamlines show that the three dimensional separation is an important flow feature of endwall and blade surfaces. The larger turning results in much stronger contribution of the secondary flows to the loss developing mechanism. A large part of the endwall loss region at downstream pressure side is found to be very thin when compared to that of the cascade inlet and suction side endwall. Evolution of overall loss starts quite early within the cascade and the rate of the loss growth is much larger in the blade of large turning angle than in the blade of small turning angle.

Numerical Evaluation of Flow and Performance of Turbo Pump Inducers

  • Shim, Chang-Yeul;Kang, Shin-Hyoung
    • Journal of Mechanical Science and Technology
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    • v.18 no.3
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    • pp.481-490
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    • 2004
  • Steady state flow calculations are executed for turbo-pump inducers of modern design to validate the performance of Tascflow code. Hydrodynamic performance of inducers is evaluated and structure of the passage flow and leading edge recirculation are also investigated. Calculated results show good coincidence with experimental data of static pressure performance and velocity profiles over the leading edge. Upstream recirculation, tip leakage and vortex flow at the blade tip and near leading edge are main sources of pressure loss. Amount of pressure loss from the upstream to the leading edge corresponds to that of whole pressure loss through the blade passage. The viscous loss is considerably large due to the strong secondary flow. There appears more stronger leading edge recirculation for the backswept inducer, and this increases the pressure loss. However, blade loading near the leading edge is considerably reduced and cavitation inception delayed.

Numerical Evaluation of Flow and Performance of Turbo-Pump Inducers (터보펌프 인듀서의 유동 및 성능의 수치적 평가)

  • Shim, Chang-Yeul;Kang, Shin-Hyoung
    • 유체기계공업학회:학술대회논문집
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    • 2001.11a
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    • pp.243-249
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    • 2001
  • Steady state flow calculations are executed for turbo-pump inducers of modem design to validate the performance of Tascflow code. Hydrodynamic performance is evaluated and structure of the passage flow and leading edge recirculation are also investigated. Calculated results show good coincidence with experimental data of static pressure performance and velocity profiles over the leading edge. Upstream recirculation, tip leakage and vortex flow at the blade tip and near leading edge are main source of pressure loss. Amount of pressure loss from the upstream to the leading edge corresponds to that of pressure loss through the whole blade. The total viscous loss is considerably large due to the strong secondary flow.

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Experimental Study on Effects of the Contoured Endwall on the Three-Dimensional Flow in a Turbine Nozzle Guide Vane Cascade (곡면 끝벽을 갖는 터빈 노즐 안내깃 캐스케이드내 3차원 유동장에 관한 실험적 연구)

  • Yun, Won-Nam;Chung, Jin-Taek
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1975-1980
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    • 2004
  • The three-dimensional flow in a turbine nozzle guide vane passage causes large secondary loss through the passage and increased heat transfer on the blade surface. In order to reduce or control these secondary flows, a linear cascade with a contoured endwall configuration was used and changes in the three-dimensional flow field were analyzed and discussed. Measurements of secondary flow velocity and total pressure loss within the passage have been performed by means of five-hole probes. The investigation was carried out at fixed exit Reynolds number of $4.0{\times}10^5$. The objective of this study is to document the development of the three-dimensional flow in a turbine nozzle guide vane cascade with modified endwall. The results show that the development of passage vortex and cross flow in the cascade composed of one flat and one contoured endwalls are affected by the flow acceleration which occurs in contoured endwall side. The overall loss is reduced near the flat endwall rather than contoured endwall.

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A Study on Prediction of Metal Loss by Flow-Accelerated Corrosion in the CANDU NPP Secondary Piping Systems (침부식에 의한 CANDU형 원전 2차측 배관의 감육 예측에 관한 연구)

  • Shim, S.H.;Song, J.S.;Yoon, K.B.;Hwang, K.M.;Jin, T.E.;Lee, S.H.;Kim, W.S.
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.616-621
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    • 2001
  • Flow-accelerated corrosion(FAC) is a phenomenon that results in metal loss from piping, vessels, and equipment made of carbon steel. FAC occurs only under certain conditions of flow, chemistry, geometry, and material. Unfortunately, those conditions are in much of the high-energy piping in nuclear and fossil-fueled power plants. Also, for domestic NPP secondary pipings whose operating time become longer, more evidences of FAC have been reported. The authors are studying on FAC management using CHECWORKS, computer code developed by EPRI. This paper is on the prediction results of metal loss by FAC in the one of CANDU type NPP secondary piping systems.

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Off-Design Performance Prediction of an Axial Flow Compressor Stage Using Simple Loss Correlations (간단한 손실모델을 이용한 단단축류압축기 탈설계점 성능예측)

  • 김병남;정명균
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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    • pp.3357-3368
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    • 1994
  • Total pressure losses required to calculate the total-to-total efficiency are estimated by integrating empirical loss coefficients of four loss mechanisms along the mean-line of blades as follows; blade profile loss, secondary flow loss, end wall loss and tip clearance loss. The off-design points are obtained on the basis of Howell's off-design performance of a compressor cascade. Also, inlet-outlet air angles and camber angle are obtained from semi-empirical relations of transonic airfoils' minimum loss incidence and deviation angles. And nominal point is replaced by the design point. It is concluded that relatively simple loss models and Howell's off-design data permit us to calculate the off-design performance with satisfactory accuracy. And this method can be easily extended for off-design performance prediction of multi-stage compressors.

Numerical Analysis on Effects of the Boundary Layer Fence Equipped on the Hub of Rotor in the First Stage Axial Flow Gas Turbine (1단 축류 가스터빈내 동익의 허브면에 장착된 경계층 펜스의 효과에 대한 수치 해석적 연구)

  • Yoon, Deok-Kyu;Kim, Jae-Choon;Kim, Dae-Hyun;Lee, Won-Suk;Chung, Jin-Taek
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.2
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    • pp.8-16
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    • 2009
  • The objective of this study is to investigate the three-dimensional turbulence flow characteristics of a rotor passage of an one-stage axial flow gas turbine and to investigate the effects of a boundary layer fence installed on the hub endwall of the rotor passage. Secondary flows occurring within the rotor passage (e.g. horseshoe vortex, passage vortex, and cross flow) cause secondary loss and reduce turbine efficiency. To control these secondary flows, a boundary layer fence measuring half the height of the thickness of the inlet boundary layer was installed on the hub endwall of the rotor passage. This study was performed numerically. The results show that the wake and secondary flows generated by the stator reduced the rotor load to constrain the development of cross flow and secondary flow reinforced by the rotor passage. In addition, the secondary vortices occurring within the rotor passage were reduced by the rotation of the rotor. Although, the boundary layer fence induced additional vortices, giving rise to an additional loss of turbine, its presence was shown to reduce the total pressure loss when compared to effects of the case without fence regardless of the relative position of blades by enervating secondary vortices occurred within the rotor passage.