An Analytical Model for Over-Shroud Leakage Losses in a Shrouded Turbine Stage

El-Dosoky, M.F.; Rona, Aldo; Gostelow, J. P.

doi:10.1115/gt2007-27786

Cited by 7 publications

(2 citation statements)

References 6 publications

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“…The effects of tip clearance on tip leakage loss and its breakdown are shown in Figure 7. For shrouded turbines, the loss values were obtained by calculating the mass-averaged entropy loss coefficient, 47 which equals…”

Section: Effect Of Tip Clearance On Shrouded and Unshrouded Turbine Aerodynamicsmentioning

confidence: 99%

Comparative investigation of tip leakage flow and its effect on stage performance in shrouded and unshrouded turbines

Gao

Zheng

Zhang

et al. 2012

Proceedings of the Institution of Mechanical Engineers, Part G:

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In order to provide reference for the choice of the turbine architecture in specific application, comparative investigation was conducted to investigate the shrouded and unshrouded rotor tip leakage flows by means of the commercial CFX software, which modeled the flow in a 1.5-stage turbine. Tip leakage loss production mechanisms as well as the effects of tip clearance and pitch–chord ratio on tip leakage and stage performances were discussed and compared in this article. Numerical results show that, the leakage flow at the shroud cavity inlet effectively removes the boundary layer at rotor leading edge, and then reduces the casing secondary flows inside rotor passage. There is a break-even tip clearance at which both the shrouded and unshrouded turbines have the same efficiency, and if tip clearance is less than it, the unshrouded turbine performs better than the shrouded turbine. Compared to the unshrouded turbine, the shrouded turbine can reduce the sensitivity of turbine performances to changes in tip clearance. Moreover, at the given relative change in leakage flow, the relative change in work is approximately twice the relative change in efficiency. Besides, pitch–chord ratio has the different impact on the tip leakage mixing processes in shrouded and unshrouded turbines. It is effective to achieve lower tip leakage losses by turning the leakage flows to reduce mixing losses in shrouded turbines, and by blade tip design or tip clearance treatment to reduce the tip leakage flow in unshrouded turbines.

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Section: Effect Of Tip Clearance On Shrouded and Unshrouded Turbine Aerodynamicsmentioning

confidence: 99%

Comparative investigation of tip leakage flow and its effect on stage performance in shrouded and unshrouded turbines

Gao

Zheng

Zhang

et al. 2012

Proceedings of the Institution of Mechanical Engineers, Part G:

View full text Add to dashboard Cite

show abstract

“…Thus, multidimensional coupling computational fluid dynamics (CFD) method, as an effective approach for simulating complex flow systems, was widely applied [12][13][14][15]. El-Dosoky et al [16] presented an analytical model that uses directly measurable flow quantities to predict the effects of leakage flow on the shrouded turbine stage performance. They concluded that an injection angle of 90 deg could increase the mixing loss by about 28% compared to that injecting parallel to the main flow.…”

Section: Introductionmentioning

confidence: 99%

Effects of Double-Side Labyrinth Seals on Aerodynamic Performance in a Transonic Shrouded Turbine Stage

Weihang

Chen

Liu

et al. 2020

Journal of Engineering for Gas Turbines and Power

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Labyrinth seals on both rotor casing and blade tip as an effective method to control the leakage flowrate of the shroud and improve aerodynamic performances in a transonic turbine stage are investigated in this study. Compared to the case without the labyrinth seal structure, the cases with three different types of sealing teeth have been shown to reduce significantly the tip leakage flow by computational simulations. The double-side sealing teeth case reduces the leakage flowrate mleakage/mpassage from 3.4% to 1.3% and increases the efficiency by 1.4%, which is the maximum efficiency improvement of all cases. The sealing structures increase the loss inside the shroud while reducing the momentum mixing between shroud leakage flow and mainstream. Therefore, the circumferential distribution of leakage velocity is changed, as well as the distribution of high-loss zones at turbine outlet. Furthermore, the leakage-vortex loss, which is associated with the blockage effect of sealing structure to the tip leakage flow, gains more improvement than the passage-vortex at the rotor outlet section in double-side seal case. In addition, it has also been found that with a larger gap at tip, the double-side seal has better effects of reducing the leakage flow and improving the aerodynamic performance in the transonic turbine stage.

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