OPTIMIZATION OF TURBINE CASCADE SQUEALER TIP COOLING DESIGN BY COMBINING SHAPING AND FLOW INJECTION

2021 ◽  
pp. 1-12
Author(s):  
Penghao Duan ◽  
Li He
Keyword(s):  
Film Cooling ◽  
Computational Cost ◽  
Sudden Expansion ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Aerodynamic Efficiency ◽  
Film Cooling Effectiveness ◽  
Tip Leakage ◽  
Conventional Film ◽  
Conventional Optimization

Abstract In this study, a turbine squealer tip is optimized by a multi-objective genetic algorithm (MOGA) with varying squealer heights and tip cooling configurations. The three objectives selected are the aerodynamic efficiency, the film cooling effectiveness and the surface temperature variance. The multi-scale methodology is implemented to reduce the computational cost and to skip the meshing of cooling holes. Two optimization approaches are compared: a) a conventional method that optimizes an uncooled shape first and then the cooling configuration sequentially, and b) a method that optimize shaping and cooling concurrently. The concurrent method is found to obtain a heat transfer performance that is not achieved by the conventional optimization. Moreover, by adding the cooling, the performance ranking of the uncooled blades in terms of the aerodynamic efficiency is changed. These observations are due to the strong interaction between the coolant and the tip leakage flow. They indicate that the coolant injected at the tip is not passive as expected in the conventional film cooling designs. By altering the tip leakage flow structure, the coolant can reduce the tip leakage loss, which contradicts the conventional wisdom that the added coolant should always lead to extra losses due to the extra mixing. More detailed observations of the flow field indicate that the influence of the squealer height towards the aerodynamic efficiency is caused by two competing effects: the blockage effect to reduce the tip leakage mass flow rate and the sudden expansion loss effect to generate additional losses.

Optimization of Turbine Squealer Tip Cooling Design by Combining Shaping and Flow Injection

2020 ◽  
Author(s):  
P. H. Duan ◽  
L. He
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heat Transfer Performance ◽  
Leakage Flow ◽  
Fluid Temperature ◽  
Transfer Performance ◽  
Tip Leakage Flow ◽  
Aerodynamic Efficiency ◽  
Tip Leakage ◽  
Conventional Film

Abstract In this study, a turbine squealer tip is optimized by a multi-objective genetic algorithm (MOGA) with varying the squealer heights and the tip cooling configurations. The three objectives selected are the aerodynamic efficiency, the film cooling effectiveness and the surface fluid temperature variance. The multi-scale methodology is implemented to reduce the computational cost and to skip the meshing of cooling holes. Two optimization approaches are compared: a) a conventional method that optimizes an uncooled shape first and then the cooling configuration sequentially, and b) a method that optimize shaping and cooling concurrently. The concurrent method is found to obtain a heat transfer performance that is not achieved by the conventional optimization. Moreover, by adding the cooling, the performance ranking of the uncooled blades in terms of the aerodynamic efficiency is changed. These observations are due to the strong interaction between the coolant and the tip leakage flow. They indicate that the coolant injected at the tip is not passive as expected in the conventional film cooling designs. By altering the tip leakage flow structure, the coolant can reduce the tip leakage loss, which contradicts the conventional wisdom that the added coolant should always lead to extra losses due to the extra mixing. More detailed observations of the flow field indicate that the influence of the squealer height towards the aerodynamic efficiency is caused by two competing effects: the blockage effect to reduce the tip leakage mass flow rate and the sudden expansion loss effect to generate additional losses. The heat transfer performance can be significantly influenced by increasing the squealer height because of the trapped coolant in the cavity.

Numerical Prediction of Film Cooling and Heat Transfer With Different Film-Hole Arrangements on the Plane and Squealer Tip of a Gas Turbine Blade

2004 ◽  
Author(s):  
Huitao Yang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Heat ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Tip Leakage ◽  
High Heat Transfer

The blade tip is one area that experiences high heat transfer due to the strong tip leakage flow. One of the common methods is to apply film cooling on tip to reduce the heat load. To get a better film cooling, different arrangements of film holes on the plane and squealer tips have been numerically studied with the Reynolds stress turbulence model and non-equilibrium wall function. The present study investigated three types of film-hole arrangements: 1) the camber arrangement: the film cooling holes are located on the mid-camber line of tips, 2) the upstream arrangement: the film holes are located upstream of the tip leakage flow and high heat transfer region, and 3) two rows arrangement: the camber and upstream arrangements are combined under the same amount of coolant. In addition, three different blowing ratios (M = 0.5, 1 and 1.5), are evaluated for film cooling effectiveness and heat transfer coefficient. The predicted heat transfer coefficients are in good agreement with the experimental data, but the film cooling effectiveness is over predicted on the blade tips.

scholarly journals Effects of casing motion on tip leakage flow and film-cooling effectiveness of squealer tips

2017 ◽  
Vol 12 (2) ◽  
pp. JTST0025-JTST0025 ◽  
Author(s):  
Fengna CHENG ◽  
Haiping CHANG ◽  
Jingyang ZHANG ◽  
Jingzhou ZHANG
Keyword(s):  
Film Cooling ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Tip Leakage

Characteristics of Tip Leakage Flow of the Turbine Blade With Cutback Squealer and Coolant Injection

2010 ◽  
Author(s):  
Jianhua Wang ◽  
Yalin Liu ◽  
Xiaochun Wang ◽  
Zhineng Du ◽  
Shijie Yang
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Flow Characteristics ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Coolant Injection ◽  
Blade Tip ◽  
Film Cooling Holes ◽  
Numerical Program

Experimental and numerical investigations of the tip leakage flow characteristics between turbine blade tip and stator wall (shroud) were conducted by a particle image velocimetry (PIV) system and the commercially available software CFX 11.0. A three-time scaled profile of the GE-E3 blade was used as specimen. Two rows of cylindrical film-cooling holes with 1.5mm diameter were arranged in the blade tip. One row with 5 holes was placed in pressure side just below the groove floor, and the other with 11 holes was equidistantly arranged on the tip along the mid camber line. To exhibit the generation and movement of leakage vortex, and to compare the coolant injection effects from different rows, several typical velocity profiles were captured by the PIV system. The experimental results were used as a data source to validate the turbulence model and numerical program. To better understand the mixing characteristics of the coolant injected from different rows with the leakage flow, the fluid fields of the leakage vortex and coolant flow were simulated, and the leakage mass rates from the blade tip in different coolant injection cases and different gaps were quantitatively estimated by the validated numerical program.

Multi-Objective Optimization of Turbine Blade Tip With Film Cooling Holes

2021 ◽  
Author(s):  
Shuai Yang ◽  
Min Zhang ◽  
Yan Liu ◽  
Jinguang Yang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Pareto Optimum ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Multi Objective ◽  
Film Cooling Holes

Abstract Tip leakage flow is inevitable due to the tip clearance over rotor blades in turbines. This phenomenondeteriorates blade aerodynamic performance and induces severe thermal damage to the tip surface.Introduction of cooling jets to the tip can effectively controls the tip leakage flow and improves the tip heat transfer. Therefore, this paper aims to optimize film cooling holes on a flat tip of a subsonic cascade and an topology-optimized tip of a transonic cascade. A design variable is a material parameter defined at each grid node along the blade camber line. This idea is based on the topology optimization method. The objective is to minimize blade energy loss and maximize tip heat transfer intensity. A response surface optimization based on the design of experiment (DOE) analysis is employed, and a multi-objective Genetic Algorithm is used to get Pareto optimum solutions. During the DOE process, a CFD method using injection source terms is integrated for numerical simulations to reduce computational costs. Optimized tip film cooling holes are finally re-constructed. The influence of the newly designed tip cooling holes configuration on blade aero-thermal performance is evaluated via CFD simulations using body-fitted mesh. Results show that compared with the uniform arrangement of cooling film holes along the axial direction, all the optimized film cooling holes can improve both blade aerodynamic performance and tip heat transfer performance.

The Influence of Rotating Speed on Film Cooling Characteristics on GE-E3 Blade Tip With Different Tip Configurations

2009 ◽  
Author(s):  
D. H. Zhang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Rotating Speed ◽  
Tip Leakage ◽  
Blowing Ratio ◽  
Blade Tip ◽  
Cooling Air

The film cooling phenomenon of flat tip (with or without a trench) and squealer tip on GE-E3 blade in rotating state was numerically studied. The effect of tip configuration, rotating speed and blowing ratio on the blade tip flow and cooling performance was revealed. It was found that the squealer tip and the flat tip with trenched hole have comparability in configuration: both have a cavity at the end of the film hole. So the coolant momentum and the tip leakage flow velocity in the cavity are decreased, which contributes to the improvement of the cooling effect. Because of the bigger cavity of the squealer tip than that of the flat tip with trenched hole, the cooling air and the leakage flow mix adequately in the cavity, the squealer tip can get the highest cooling effectiveness and the lowest heat transfer coefficient value both in stationary and rotating state, and the flat tip with trenched hole follows. With the increase of rotating speed, for all the three configurations, the area-averaged cooling effectiveness decreases and the area-averaged heat transfer coefficient increases. At the same time, the tip leakage flow entraps the cooling air moving toward the leading edge. And with the increase of the blowing ratio, for all the configurations, the area-averaged cooling effectiveness increases while the area-averaged heat transfer coefficients decreases.

Controlling Leakage Flows Over a Rotor Blade Tip Using Air-Curtain Injection: Part I — Aero-Thermal Performance of Rotor Tips

2019 ◽  
Author(s):  
Xing Yang ◽  
Qiang Zhao ◽  
Zhao Liu ◽  
Zhenping Feng ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Leakage Flow ◽  
Efficiency Improvement ◽  
Tip Leakage Flow ◽  
Air Curtain ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Blade Tip ◽  
Cooling Air ◽  
Blade Tips

Abstract The rotor casing of gas turbine engines is generally cooled with cooling air from compressors and then the cooling air is discharged into the passage flow of the rotor. In this paper, a novel design both for the blade tip leakage flow control and for the rotor casing and tip cooling is proposed. Cooling air is injected through a pair of inclined rows of discrete holes positioned between 30% and 50% axial chord downstream of the blade leading edge in the casing. The casing injection forms as air-curtain within the blade tip gap, and inhibits the development of the tip leakage flows and provides secondary-order cooling for the rotor tip. Air injection from the rotor casing onto flat and recessed blade tips is investigated using numerical simulations that is validated by extensive aerodynamic and heat transfer experimental data. Flow and film cooling over the blade tip and turbine overall aerodynamic performance are examined in detail for two casing injection rates. Comparisons between flat tip without casing injection (baseline) case and the casing injection cases show that the air-curtain injection significantly alters the flow structures near the casing by modifying the development and migration of the tip leakage flow. The air-curtain injection over the flat and recessed tips both generates turbine stage overall aerodynamic efficiency improvement due to the sealing effects of the casing injection, but the efficiency gain depends on the competing results between the sealing effects and the “over-blown” effects of the air-curtain injection. Applying a recess to the blade tip is generally detrimental to the efficiency improvement by the air-curtain injection. In addition to efficiency improvement, secondary-order cooling effects from the casing injection are found to provide considerable thermal protection for the blade tips. However, increasing injection rate reduces the film cooling performance over the rotor tip surfaces. The recessed tip could present better film cooling effectiveness than the flat tip in the presence of the air-curtain.

Influence of Different Shoulder Widths on Film Cooling Characteristics on GE-E3 Blade Tip

2010 ◽  
Author(s):  
Jin Wang ◽  
D. H. Zhang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Film Cooling ◽  
Three Dimensional ◽  
Asymmetric Structure ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Flow Measurements ◽  
Tip Leakage ◽  
Film Cooling Holes

Three-dimensional simulations of squealer tip on GE-E3 blade with eight film cooling holes were numerically studied. Numerical simulations were performed to predict the leakage flow and the tip heat transfer in the tip-gap region with the κ-ε model. For the squealer tip, the depth of the cavity is 2.42 mm, and the width of the shoulder is 0.77 mm, which forms a narrow rim and a wide cavity, decreasing the coolant momentum and the tip leakage flow velocity. The cavity contributes to the improvement of the cooling effect. In view of the absence of detailed three-dimensional flow measurements in the tip region of the blade and current lack of related literatures, it is necessary to fix attention on the shoulder width. To investigate the leakage flow influenced by the rim width, the paper used the asymmetric structure. The rim width in pressure surface in the tip-gap region is different from the one in suction surface. Numerical simulations were made at three different models, which were 0.77 mm, 1.22 mm and 1.67 mm respectively on the pressure side rim, and which were 0.77 mm, 2.27 mm and 3.77 mm respectively on the suction side rim. The rim width has a significant influence on local tip heat transfer coefficient distribution and the tip leakage flow. The detailed information was obtained under global blowing ratios of M = 0.5, 1.0 and 1.5. In addition, varying rim width models of squealer tip without film cooling holes were compared with those with film cooling holes.

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.

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