An aerothermal study of the influence of squealer width and height near a HP turbine blade

Senel, Cem Berk; Maral, Hıdır; Kavurmacıoğlu, Levent; Camcı, Cengiz

doi:10.1016/j.ijheatmasstransfer.2017.12.017

Cited by 54 publications

(12 citation statements)

References 28 publications

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“…With the groove depth increases to 3% of blade span, leakage flow would be weakened. Senel et al [ 9 ] revealed the influence of squealer width and height on the aerothermal performance of a high pressure turbine blade by numerical calculation. They found that a proper squealer width and height was critical to reduce aerodynamic loss and heat transfer, which is the same as Yang and Feng’s [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Chen

Yuan

2018

Entropy

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In unshrouded turbine rotors, the tip leakage vortices develop and interact with the passage vortices. Such complex leakage flow causes the major loss in the turbine stage. Due to the complex turbulence characteristics of the tip leakage flow, the widely used Reynolds Averaged Navier–Stokes (RANS) approach may fail to accurately predict the multi-scale turbulent flow and the related loss. In order to effectively improve the turbine efficiency, more insights into the loss mechanism are required. In this work, a Delayed Detached Eddy Simulation (DDES) study is conducted to simulate the flow inside a high pressure turbine blade, with emphasis on the tip region. DDES results are in good agreement with the experiment, and the comparison with RANS results verifies the advantages of DDES in resolving detailed flow structures of leakage flow, and also in capturing the complex turbulence characteristics. The snapshot Proper Orthogonal Decomposition (POD) method is used to extract the dominant flow features. The flow structures and the distribution of turbulent kinetic energy reveal the development of leakage flow and its interaction with the secondary flow. Meanwhile, it is found that the separation bubble (SB) is formed in tip clearance. The strong interactions between tip leakage vortex (TLV) and the up passage vortex (UPV) are the main source of unsteady effects which significantly enhance the turbulence intensity. Based on the DDES results, loss analysis of tip leakage flow is conducted based on entropy generation rates. It is found that the viscous dissipation loss is much stronger than heat transfer loss. The largest local loss occurs in the tip clearance, and the interaction between the leakage vortex and up passage vortex promotes the loss generation. The tip leakage flow vortex weakens the strength of up passage vortex, and loss of up passage flow is reduced. Comparing steady and unsteady effects to flow field, we found that unsteady effects of tip leakage flow have a large influence on flow loss distribution which cannot be ignored. To sum up, the current DDES study about the tip leakage flow provides helpful information about the loss generation mechanism and may guide the design of low-loss blade tip.

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Section: Introductionmentioning

confidence: 99%

Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Chen

Yuan

2018

Entropy

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“…A detailed validation of the specific computational method used in this paper is provided in Senel et al [23]. Although [23] focuses on the aerothermal influence of squealer width and height, it uses the identical tip geometry of the Axial Flow Turbine Research Facility (AFTRF) and the same computational approach used in this publication.…”

Section: Methodsmentioning

confidence: 99%

“…Although [23] focuses on the aerothermal influence of squealer width and height, it uses the identical tip geometry of the Axial Flow Turbine Research Facility (AFTRF) and the same computational approach used in this publication.…”

Section: Methodsmentioning

confidence: 99%

Performance of Partial and Cavity Type Squealer Tip of a HP Turbine Blade in a Linear Cascade

Kavurmacıoğlu

Maral

Senel

et al. 2018

International Journal of Aerospace Engineering

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Three-dimensional highly complex flow structure in tip gap between blade tip and casing leads to inefficient turbine performance due to aerothermal loss. Interaction between leakage vortex and secondary flow structures is the substantial source of that loss. Different types of squealer tip geometries were tried in the past, in order to improve turbine efficiency. The current research deals with comparison of partial and cavity type squealer tip concepts for higher aerothermal performance. Effects of squealer tip have been examined comprehensively for an unshrouded HP turbine blade tip geometry in a linear cascade. In the present paper, flow structure through the tip gap was comprehensively investigated by computational fluid dynamic (CFD) methods. Numerical calculations were obtained by solving three-dimensional, incompressible, steady, and turbulent form of the Reynoldsaveraged Navier-Stokes (RANS) equations using a general purpose and three-dimensional viscous flow solver. The two-equation turbulence model, shear stress transport (SST), has been used. The tip profile belonging to the Pennsylvania State University Axial Flow Turbine Research Facility (AFTRF) was used to create an extruded solid model of the axial turbine blade. For identifying optimal dimensions of squealer rim in terms of squealer height and squealer width, our previous studies about aerothermal investigation of cavity type squealer tip were utilized. In order to obtain the mesh, an effective parametric generation has been utilized using a multizone structured mesh. Numerical calculations indicate that partial and cavity squealer designs can be effective to reduce the aerodynamic loss and heat transfer to the blade tip. Future efforts will include novel squealer shapes for higher aerothermal performance.

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“…Senel et al. 12 analyzed the vortex structures in the cavity by numerical simulation and found that cavity flow is divided into two legs as PS and SS legs of cavity vorticity. The larger the PS cavity vortex, the stronger the blocking effect on pass-over flow and the more obvious the decrease of the tip leakage mass flow rate.…”

Section: Introductionmentioning

confidence: 99%

Effect of arbitrary blade tip design on tip leakage flow

Jin¹,

Song²,

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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Tip geometry modification is frequently used to suppress the tip leakage flow in the turbine cascade however a universally beneficial tip geometry modification design has not been fully discovered. In this paper, the two-surface coupling arbitrary blade tip design method in three-dimensional physical space which satisfies the simple trigonometric function law is proposed and the mathematical parametric description is presented. The effects of different arbitrary blade tips on tip leakage flow have been studied numerically in a highly loaded axial turbine cascade. The aerodynamic performance of different tips is assessed by the tip leakage mass flow rate and the total pressure loss coefficient at the exit section. The Kriging model and genetic optimization algorithm are used to optimize the arbitrary blade tips to obtain the optimal arbitrary blade tip. Compared with the flat tip, the tip leakage mass flow rate is decreased by 10.57% and the area-average total pressure loss coefficient at the exit section is reduced by 8.91% in the optimal arbitrary blade tip.

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An aerothermal study of the influence of squealer width and height near a HP turbine blade

Cited by 54 publications

References 28 publications

Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Performance of Partial and Cavity Type Squealer Tip of a HP Turbine Blade in a Linear Cascade

Effect of arbitrary blade tip design on tip leakage flow

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