Clearance Reduction and Performance Gain Using Abradable Material in Gas Turbines

2008 ◽  
Author(s):  
Iacopo Giovannetti ◽  
Manuele Bigi ◽  
Massimo Giannozzi ◽  
Dieter R. Sporer ◽  
Filippo Cappuccini ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Leakage Flow ◽  
Performance Gain ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Hot Gas ◽  
Industrial Gas Turbines ◽  
Basic Parameters ◽  
Component Shape ◽  
And Performance

An improvement in the energy efficiency of industrial gas turbines can be accomplished by developing abradable seals to reduce the stator/rotor gap to decrease the tip leakage flow of gases in the hot gas components of the turbine. “ABRANEW” is a project funded by the European Commission aimed at developing a high temperature abradable material capable of controlled abrasion and resistant to erosion and oxidation. In order to define the basic parameters such as the component shape, the existing gap, the expected gap reduction, the seal thickness and other geometric parameters, a comprehensive review of the design of the blade/shroud/casing system was performed.

Effect of Turbine Blade Tip Cooling Configuration on Tip Leakage Flow and Heat Transfer

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Sergen Sakaoglu ◽  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

Abstract The pressure difference between suction and pressure sides of a turbine blade leads to tip leakage flow, which adversely affects the first-stage high-pressure (HP) turbine blade tip aerodynamics. In modern gas turbines, HP turbine blade tips are exposed to extreme thermal conditions requiring cooling. If the coolant jet directed into the blade tip gap cannot counter the leakage flow, it will simply add up to the pressure losses due to leakage. Therefore, the compromise between the aerodynamic loss and the gain in tip-cooling effectiveness must be optimized. In this paper, the effect of tip-cooling configuration on the turbine blade tip is investigated numerically from both aerodynamics and thermal aspects to determine the optimum configuration. Computations are performed using the tip cross section of GE-E3 HP turbine first-stage blade for squealer and flat tips, where the number, location, and diameter of holes are varied. The study presents a discussion on the overall loss coefficient, total pressure loss across the tip clearance, and variation in heat transfer on the blade tip. Increasing the coolant mass flow rate using more holes or by increasing the hole diameter results in a decrease in the area-averaged Nusselt number on the tip floor. Both aerodynamic and thermal response of squealer tips to the implementation of cooling holes is superior to their flat counterparts. Among the studied configurations, the squealer tip with a larger number of cooling holes located toward the pressure side is highlighted to have the best cooling performance.

A Study of the Heat Transfer in Winglet and Squealer Rotor Tip Configurations for a Non-Cooled HPT Blade Based on CFD Calculations

2013 ◽  
Author(s):  
Lucilene Moraes da Silva ◽  
Jesuino Takachi Tomita
Keyword(s):  
Rotor Blade ◽  
Energy Transfer Process ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Hot Gas ◽  
Turbine Performance ◽  
Blade Row ◽  
The Common

HPT operate at high pressure and temperatures. One of the most important loss sources is the tip leakage flow on the rotor tip region. The flow that leaks in this region does not participate in the energy transfer process between the hot gas and rotor blade row. Hence, the main flow suffers a penalty to maintain the energy conservation. To try decreasing this mass flow leakage some techniques can be applied. The most common are the winglet and squealer rotor tip configuration. These techniques improve the turbine performance, but some attention should be taken into account because the temperature distribution changes on this region for different tip configurations. In this work, the winglet and squealer tip geometries are compared with the common flat tip configuration. The analysis was performed for design and off-design conditions. The HPT developed in the E3 program was used as baseline turbine to explore the differences of the flowfield on the rotor tip region. The results are compared and discussed in detail.

Effect of Turbine Blade Tip Cooling Configuration on Tip Leakage Flow and Heat Transfer

2019 ◽  
Author(s):  
Sergen Sakaoglu ◽  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

Abstract The pressure difference between suction and pressure sides of a turbine blade leads to the so-called phenomenon, the tip leakage flow, which most adversely affects the first-stage high-pressure (HP) turbine blade tip aerodynamics. In modern gas turbines, HP turbine blade tips are also exposed to extreme thermal conditions requiring the use of tip cooling. If the coolant jet directed into the blade tip gap cannot counter the leakage flow, it will simply add up to the pressure losses due to this leakage flow. Therefore, it is necessary to handle the design of tip cooling in such a way that the compromise between the aerodynamic loss and the gain in the tip cooling effectiveness is optimized. In this paper, the effect of tip cooling configuration on the turbine blade tip is investigated numerically both from the aerodynamics and thermal aspects in order to determine the optimum tip cooling configuration. The studies are carried out using the tip cross-section of General Electric E3 (Energy Efficient Engine) HP turbine first-stage blade for two different tip geometries, squealer tip and flat tip, where the number, location, and diameter of the cooling holes are varied. The study presents a discussion on the overall loss coefficient, the total pressure loss across the tip clearance, and the variation of heat transfer on the blade tip. The aerodynamic and heat transfer results are compared with the experimental data from literature. It is observed that increasing the coolant mass flow rate by using more holes or by increasing the hole diameter results in a decrease in the area-averaged Nusselt number on the tip floor, as expected. The findings show that both aerodynamic and thermal response of the squealer tips to the implementation of cooling holes is superior to their flat counterparts. Among the studied configurations, the squealer tip with larger number of cooling holes located towards the pressure side is highlighted as the configuration having the best cooling performance.

On Prediction of Tip Leakage Flow and Heat Transfer in Gas Turbines

2004 ◽  
Author(s):  
Fadil Mumic ◽  
Daniel Eriksson ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Numerical Study ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow And Heat Transfer

A numerical study has been performed to simulate the tip leakage flow and heat transfer on the first stage of a high-pressure turbine, which represents a modern gas turbine blade geometry. The low Re k-ω (SST) model is used to model the turbulence. Calculations are performed for both a flat and a squealer blade tip for three different tip gap clearances. The computations were carried out using a single blade with periodic conditions imposed along the boundaries in the circumferential (pitch) direction. The predicted tip heat transfer and static pressure distributions show reasonable agreement with experimental data. It was also observed that the tip clearance has a significant influence on local tip heat transfer coefficient distribution. The flat tip blade provides a higher overall heat transfer coefficient than the squealer tip blade.

The Effect of the Operating Conditions of the Last Turbine Stage on the Performance of an Axial Exhaust Diffuser

2011 ◽  
Author(s):  
Victor Opilat ◽  
Joerg R. Seume
Keyword(s):  
Gas Turbines ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Pressure Recovery ◽  
Test Facility ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Inlet Flow ◽  
Tip Leakage

The exhaust diffusers studied in this paper are installed behind the last turbine stage of gas turbines, including those used in combined cycle power plants. For the design of efficient diffusers, the effects caused by the last turbine stage need to be taken into account. In the present paper, results are presented to estimate the performance of a diffuser operating under a variation of multiple modelling parameters: tip leakage flow, the swirl, and the rotating blade wakes. To provide a better understanding of the flow parameters, a test facility with a turbine stage simulator is used to model these flow effects and an optical endoscopic planar measurement technique based upon Particle Image Velocimetry (PIV) is applied. The pressure recovery is estimated for various turbine conditions using a variety of relevant parameters. Within a range of conditions, a PIV study is performed to try to understand the typical flow phenomena which influence the performance of axial diffusers. The rise of turbulent energy in the inlet flow positively affects the diffuser performance. A small positive swirl angle in the inlet flow (behind the rotating bladed wheel in experiments) has a stabilizing effect on the diffuser. The tip leakage flow from the last turbine stage can also positively affect the pressure recovery in the diffuser.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

Development of the Tip-Leakage Flow Downstream of a Planar Cascade of Turbine Blades: Vorticity Field

1989 ◽  
Author(s):  
M. Yaras ◽  
S. A. Sjolander
Keyword(s):  
Simple Model ◽  
Turbine Blades ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Vorticity Field ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Blade Row ◽  
Axisymmetric Structure ◽  
Insight Into

The paper presents detailed measurements of the tip-leakage flow emerging from a planar cascade of turbine blades. Four clearances of from 1.5 to 5.5 percent of the blade chord are considered. Measurements were made at the trailing edge plane, and at two main planes 1.0 and 1.56 axial chord lengths downstream of the cascade. The results give insight into several aspects of the leakage flow including: the size and strength of the leakage vortex in relation to the size of the tip gap and the bound circulation of the blade; and the evolution of the components of vorticity as the vortex diffuses laterally downstream of the blade row. The vortex was found to have largely completed its roll-up into a nearly axisymmetric structure even at the trailing edge of the cascade. As a result, it was found that the vortex could be modelled surprisingly well with a simple model based on the diffusion of a line vortex.

Study of the Standard k-ε Model for Tip Leakage Flow in an Axial Compressor Rotor

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Yanfei Gao ◽  
Yangwei Liu ◽  
Luyang Zhong ◽  
Jiexuan Hou ◽  
Lipeng Lu
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Axial Compressor ◽  
Leakage Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor

AbstractThe standard k-ε model (SKE) and the Reynolds stress model (RSM) are employed to predict the tip leakage flow (TLF) in a low-speed large-scale axial compressor rotor. Then, a new research method is adopted to “freeze” the turbulent kinetic energy and dissipation rate of the flow field derived from the RSM, and obtain the turbulent viscosity using the Boussinesq hypothesis. The Reynolds stresses and mean flow field computed on the basis of the frozen viscosity are compared with the results of the SKE and the RSM. The flow field in the tip region based on the frozen viscosity is more similar to the results of the RSM than those of the SKE, although certain differences can be observed. This finding indicates that the non-equilibrium turbulence transport nature plays an important role in predicting the TLF, as well as the turbulence anisotropy.

Flow Structures in the Tip Region for a Transonic Compressor Rotor

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Juan Du ◽  
Feng Lin ◽  
Jingyi Chen ◽  
Chaoqun Nie ◽  
Christoph Biela
Keyword(s):  
Numerical Simulations ◽  
Reference Frame ◽  
Three Dimensional ◽  
Flow Structures ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Tip Leakage Flows

Numerical simulations are carried out to investigate flow structures in the tip region for an axial transonic rotor, with careful comparisons with the experimental results. The calculated performance curve and two-dimensional (2D) flow structures observed at casing, such as the shock wave, the expansion wave around the leading edge, and the tip leakage flow at peak efficiency and near-stall points, are all captured by simulation results, which agree with the experimental data well. An in-depth analysis of three-dimensional flow structures reveals three features: (1) there exists an interface between the incoming main flow and the tip leakage flow, (2) in this rotor the tip leakage flows along the blade chord can be divided into at least two parts according to the blade loading distribution, and (3) each part plays a different role on the stall inception mechanism in the leakage flow dominated region. A model of three-dimensional flow structures of tip leakage flow is thus proposed accordingly. In the second half of this paper, the unsteady features of the tip leakage flows, which emerge at the operating points close to stall, are presented and validated with experiment observations. The numerical results in the rotor relative reference frame are first converted to the casing absolute reference frame before compared with the measurements in experiments. It is found that the main frequency components of simulation at absolute reference frame match well with those measured in the experiments. The mechanism of the unsteadiness and its significance to stability enhancement design are then discussed based on the details of the flow field obtained through numerical simulations.

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