Secondary Flow Loss Reduction in a Turbine Cascade with a Linearly Varied Height Streamwise Endwall Fence

Kumar, Krishna N.; Govardhan, M.

doi:10.1155/2011/352819

Cited by 25 publications

(11 citation statements)

References 28 publications

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“…In the present work, the turbulence model utilized in all the cases is one of the variants of the well-known turbulence model available within CFDRC, known as the shear stress transport (SST) model, which employ averaged governing equations to solve for the mean flow quantities and provide the distribution of the turbulent viscosity that is needed in the approximations of the Equation (2). The predictions utilizing this model were validated and compared with the experimental data by many researchers [40][41][42] and found that the SST model provided the most appropriate prediction of behavior of similar cases such as film cooling. The SST model is a two equation model presented by Menter.…”

Section: Turbulence Modelmentioning

confidence: 99%

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Numerical investigations of fluid flow and heat transfer characteristics in solar air collector with curved perforated baffles

El‐Said

2020

Engineering Reports

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In this article, an improved double-pass solar air heater with multiple curved perforated baffles is proposed; the solar air heater can enhance the heat transfer between air and heat absorber plate sufficiently by using a perforated baffles. At the same time, to reduce the flow resistance of air, a curved shape was created on the baffles. This research is aimed at evaluating a novel solar air heater design in terms of its thermal efficiency and temperature distributions within the solar air heater in forced convection. This investigation is performed based on numerical simulations in two-dimensional, steady, incompressible Navier-Stokes and energy equations utilizing CFDRC software with the shear stress transport turbulence model. The main factors including the hole diameter, baffle inclination angle, and air mass flow rate were evaluated. The effects of these factors on the thermal efficiency of solar air heater and the temperature and pressure difference between the inlet and outlet were analyzed. The results obtained for the different cases show that the maximum thermal efficiency of the air heater is about 77% at air mass flow rate = 0.03 kg/s, hole diameter = 3 mm, and baffle angle = 7 • . However, the work section pressure drop across this new solar air heater is varied between about 15.05 and 1.7 N/m 2 . These numerical results are important for the application of this improved solar air heater and show that the curved perforated baffles in the air channel is a crucial factor for improving of collector performance. K E Y W O R D Scurved baffle, heat transfer, performance improvement, solar air heater INTRODUCTIONA solar air heater (SAH) is a straightforward heating system that converts solar energy into thermal energy. Thanks to their sustainability, portability, and ease of use and installation, SAHs have been applied to a variety of purposes, such as space heating, preheating for industrial applications, and drying of various materials. 1 SAHs are also commonly employed Abbreviations: CFD, computational fluid dynamics; SAH, solar air heater; SST, shear stress transport.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Section: Turbulence Modelmentioning

confidence: 99%

“…This model utilizes a blending function that allows switching between the k-model in the sub and log layer and the -model in the outer region of the boundary layer and in free-shear flows. 35 The complete formulation of the SST model is given as follows 40 :…”

Section: Turbulence Modelmentioning

confidence: 99%

Numerical investigations of fluid flow and heat transfer characteristics in solar air collector with curved perforated baffles

El‐Said

2020

Engineering Reports

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“…Endwall fence technique has been utilized to reduce secondary flow loss in turbine cascades for a long history. Experimental investigations of (Kawai 1994) and Govardhan and Kumar (2011) found that fence with 1/3 height of the inlet boundary layer thickness when located half a pitch away from the blade suction side is optimal. Moreover, (Moon and Koh 2001) have simulated the complicated vortex structure of flow field in turbine cascade with and without endwall fence, which leads to an understanding on the formation of counter-rotating streamwise fence vortex and explains the mechanism of controlling secondary flow development.…”

Section: Introductionmentioning

confidence: 99%

Control 0f Secondary Crossflow in a High-Speed Compressor Cascade by Endwall Fences with Varying Locations

Chen¹,

Yang²,

Zhong³

2019

Proceedings of Global Power &Amp; Propulsion Society

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It is well known that the secondary flow, including vortexes, boundary layer, and three-dimensional separation, is detrimental to the efficiency and stability in the axial compressor. As a passive secondary flow control technique, the endwall fence is considered to overcome the adverse pressure gradient by blocking the crossflow. On this paper, a steady computational study is carried out in a high-speed compressor cascade. Two categories of fence configurations, i.e., embedded in the front and the back of flow passage, have been investigated. For each category, the fence position is selected at 7 locations ranging from 20% to 80% pitch length away from the blade pressure surface, the interval between each case is 10% pitch length. In the comparison between the datum and the fenced cascade, the case of 50% pitch length away from the blade suction surface in the category of front fences is most effective in the improvement of the aerodynamic performance. At the design point, this case decreases the loss coefficient and the blockage coefficient by 6.3% and 6.5%, respectively. Meanwhile, it increases the absolute value of the flow turning angle by 0.9%. From the perspective of the vortex structure, both optimum fences in the front and back category can suppress the passage vortex by inducing the counter-rotating fence vortex, of which scale has a relationship with the contact area between fence surface and the crossflow. Last but not least, the fenced cascade with an optimum performance both in loss mechanism and vortex structure has been investigated under varying inlet incidences. The comparison analysis of the baseline and optimum fence and demonstrates that there is a reduction of the loss exists at negative incidences while an augment occurs at positive incidences. In summary, the optimum case of endwall fence can effectively weaken the endwall loss and thereby enlarge the cascade operating range under negative incidences.

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“…Moser et al [8] designed an optimized radially profiled axisymmetric casing for a guide vane of a steam turbine stage that reduced the stage loss over a wide range of pressure ratios. Kumar and Govardhan [9] applied a streamwise end wall fence to reduce secondary flow losses in a linear turbine cascade. They predicted reductions in the exit flow angle deviation, secondary flow losses, and the magnitude and spanwise penetration of the passage vortex.…”

Section: Introductionmentioning

confidence: 99%

Optimization of the non-axisymmetric stator casing of a 1.5 stage axial turbine

Kadhim

Rona

Gostelow

et al. 2018

International Journal of Mechanical Sciences

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The interaction of secondary flows with the main passage flow in turbomachines results in entropy generation and in aerodynamic loss. This loss source is most relevant to low aspect ratio blades. One approach for reducing this flow energy loss is by end-wall contouring. However, limited work has been reported on using non-axisymmetric end-walls at the stator casing and on its interaction with the tip leakage flow. In this paper, a non-axisymmetric end-wall design method for the stator casing is implemented through a novel surface definition, towards mitigating secondary flow losses. This design is tested on a three-dimensional axial turbine RANS model built in OpenFOAM Extend 3.2, with − SST turbulence closure. Flow analysis confirm the foundations of the new surface definition approach, which is implemented using Alstom Process and Optimization Workbench (APOW) software. Computer-based optimization of the surface topology is demonstrated towards automating the design process of axial turbines in an industrial design workflow. The design is optimized using the total pressure loss across the first stator and across the full stage, as the target function. Numerical predictions of the 1.5 stage axial turbine show the positive impact of the optimized casing design on the efficiency that increases by 0.69% against the benchmark axisymmetric stage from RTWH Aachen, which is validated against experiment. The new non-axisymmetric casing is also beneficial at off-design condition. The effective mitigation of the secondary flows is predicted to give a 0.73% efficiency gain off-design.

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Secondary Flow Loss Reduction in a Turbine Cascade with a Linearly Varied Height Streamwise Endwall Fence

Cited by 25 publications

References 28 publications

Numerical investigations of fluid flow and heat transfer characteristics in solar air collector with curved perforated baffles

Numerical investigations of fluid flow and heat transfer characteristics in solar air collector with curved perforated baffles

Control 0f Secondary Crossflow in a High-Speed Compressor Cascade by Endwall Fences with Varying Locations

Optimization of the non-axisymmetric stator casing of a 1.5 stage axial turbine

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