Influence of Different Rim Widths and Blowing Ratios on Film Cooling Characteristics for a Blade Tip

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Jin Wang ◽  
Bengt Sundén ◽  
Min Zeng ◽  
Qiu-wang Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Film Cooling ◽  
Three Dimensional ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Blade Tip ◽  
Film Cooling Holes

Three-dimensional simulations of the squealer tip on the GE-E3 blade with eight film cooling holes were carried out. The effect of the rim width and the blowing ratio on the blade tip flow and cooling performance were revealed. Numerical simulations were performed to predict the leakage flow and the tip heat transfer with the k–ɛ model. For the squealer tip, the depth of the cavity is fixed but the rim width varies to form a wide cavity, which can decrease the coolant momentum and the tip leakage flow velocity. This cavity contributes to the improvement of the cooling effect in the tip zone. To investigate the influence on the tip heat transfer by the rim width, numerical simulations were performed as a two-part study: (1) unequal rim width study on the pressure side and the suction side and (2) equal rim width study with rim widths of 0.58%, 1.16%, and 1.74% of the axial chord (0.5 mm, 1 mm, and 1.5 mm, respectively) on both the pressure side rim and the suction side rim. With different rim widths, the effect of different global blowing ratios, i.e., M = 0.5, 1.0 and 1.5, was investigated. It is found that the total heat transfer rate is increasing and the heat transfer rates on the rim surface (RS) rapidly ascend with increasing rim width.

Influence of Different Rim Widths on Leakage Flow

2011 ◽  
Author(s):  
Jin Wang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Numerical Simulations ◽  
Film Cooling ◽  
Three Dimensional ◽  
Suction Side ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blowing Ratio ◽  
Calculation Results ◽  
Blade Tip ◽  
Film Cooling Holes

Three-dimensional simulations of squealer tip on GE-E3 blade with eight film cooling holes were numerically studied. The effect of the rim width and the blowing ratio on the blade tip flow was revealed. Numerical simulations were performed to predict the leakage flow and the tip heat transfer with the k-ε model. For the squealer tip, the depth of the cavity is the same and the width of the shoulder varies to form a narrow rim and a wide cavity, which can decrease the coolant momentum and the tip leakage flow velocity. This cavity contributes to the improvement of the cooling effect in the tip zone. To investigate the leakage flow influenced by the rim width, numerical simulations were made at four different models which have different rim widths of 0.58%, 0.89%, 1.16% and 1.74% axial chord (0.5mm, 0.77mm, 1 mm and 1.5mm, respectively) on both the pressure side rim and the suction side rim. From the simulated results, mathematical equations of mass flow rate of the leakage flow and the blowing ratio were proposed. With different rim widths, the effect of different global blowing ratios of M = 0.5, 1.0 and 1.5 is investigated. In addition, calculation results of squealer tip and flat tip were compared. The simulation results are validated with some limited experimental data in the open literatures.

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.

Numerical Study of Blade Tip Cooling at High Speed With Tip and Pressure-Side Coolant Injections

2018 ◽  
Author(s):  
Zhihua Zhou ◽  
Songtao Wang ◽  
Shaowen Chen
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Suction Side ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Film Cooling Effectiveness ◽  
Coolant Injection ◽  
High Heat Transfer ◽  
Blade Tip ◽  
Cavity Floor

The tip clearance between turbine blade and stationary casing leads to the exposure of blade tip to high temperature gas and contributes to a high thermal load in this region. Then it is necessary to perform cooling on the blade tip. Moreover, the tip leakage flow in a high speed brings complex aerothermal conditions to the blade tip. The blade tip film cooling on the transonic squealer tip is investigated in this research. The effects of tip and pressure-side coolant injections on the blade tip heat transfer are discussed. And the influences of total pressure ratio of coolant to main flow and endwall moving on the film cooling are considered. Firstly, the reliability of a commercial CFD code with different turbulence models was first validated by contrasting with the experimental results. The heat flux and isentropic Ma number predicted with the BSL k-ω model shows a better agreement with the test data. Then the mesh independency study was performed. The mesh with tip and pressure-side injection hole is generated by in-house code. For the tip without film cooling at outlet Mach number of 0.96, the squealer tip shows a high heat transfer at front of the tip cavity floor caused by the impingement of tip leakage flow, besides the suction-side rim has high heat transfer coefficient. With the tip coolant injection, the tip coolant is pushed towards the cavity pressure-side and provides better coverage in this region. At the front of cavity floor near suction-side, there is almost no coolant coverage then it shows little cooling effects. The coolant discharges from the tip over the suction-side rim thereby the heat transfer near the trailing edge is less affected by the tip coolant injection. With the pressure-side near tip film cooling, the coolant injection shows high film-cooling effectiveness at low coolant stagnation pressure and lift off blade surface at high coolant stagnation pressure. The endwall motion increases the total heat load of the blade tip by increase heat load at cavity floor and suction-side near tip region and the reduces film-cooling effectiveness.

Numerical Study of Heat Transfer and Cooling Effectiveness on a Flat-Tip Turbine Blade

2013 ◽  
Author(s):  
Qihe Huang ◽  
Jiao Wang ◽  
Lei He ◽  
Qiang Xu
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Numerical Study ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study is performed to simulate the tip leakage flow and heat transfer on the first stage rotor blade tip of GE-E3 turbine, which represents a modern gas turbine blade geometry. Calculations consist of the flat blade tip without and with film cooling. For the flat tip without film cooling case, in order to investigate the effect of tip gap clearance on the leakage flow and heat transfer on the blade tip, three different tip gap clearances of 1.0%, 1.5% and 2.5% of the blade span are considered. And to assess the performance of the turbulence models in correctly predicting the blade tip heat transfer, the simulations have been performed by using four different models (the standard k-ε, the RNG k-ε, the standard k-ω and the SST models), and the comparison shows that the standard k-ω model provides the best results. All the calculations of the flat tip without film cooling have been compared and validated with the experimental data of Azad[1] and the predictions of Yang[2]. For the flat tip with film cooling case, three different blowing ratio (M = 0.5, 1.0, and 1.5) have been studied to the influence on the leakage flow in tip gap and the cooling effectiveness on the blade tip. Tip film cooling can largely reduce the overall heat transfer on the tip. And the blowing ratio M = 1.0, the cooling effect for the blade tip is the best.

Numerical Study of Flow and Heat Transfer on a Blade Tip With Different Leakage Reduction Strategies

2003 ◽  
Author(s):  
Sumanta Acharya ◽  
Huitao Yang ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Flow Rates ◽  
Leakage Reduction ◽  
Flow And Heat Transfer ◽  
Reduction Strategies ◽  
Blade Tip

Numerical calculations are performed to explore different strategies for reducing tip leakage flow and heat transfer on the GE-E3 High-Pressure-Turbine (HPT) rotor blade. The calculations are performed for a single blade with periodic conditions imposed along the two boundaries in the circumferential-pitch direction. Several leakage reduction strategies are considered, all for a tip-clearance of 1.5% of the blade span, a pressure ratio (ratio of inlet total pressure to exit static pressure) of 1.2, and an inlet turbulence level of 6.1%. The first set of leakage reduction strategies explored include different squealer tip configurations: pressure-side squealer, suction-side squealer, mean-camber line squealer, and pressure plus suction side squealers located either along the edges of the blade or moved inwards. The suction-side squealer is shown to have the lowest heat transfer coefficient distribution and the lowest leakage flow rates. Two tip-desensitization strategies are explored. The first strategy involves a pressure-side winglet shaped to be thickest at the location with the largest pressure difference across the blade. The second strategy involves adding inclined ribs on the blade tip with the ribs normal to the local flow direction. While both strategies lead to reduction in the leakage flow and tip heat transfer rates, the ribbed tip exhibits considerably lower heat transfer coefficients. In comparing the two desensitization schemes with the various squealer tip configurations, the suction side squealer still exhibits the lowest heat transfer coefficient and leakage flow rates.

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

2003 ◽  
Author(s):  
Arun K. Saha ◽  
Sumanta Acharya ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Average Heat Transfer Coefficient ◽  
Tip Leakage Flow ◽  
Average Heat ◽  
Flow And Heat Transfer ◽  
Blade Tip

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.

Aerodynamic Investigation of the Tip Leakage Flow for Blades With Different Tip Squealer Geometries at Transonic Conditions

2009 ◽  
Author(s):  
Toma´sˇ Hofer ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Suction Side ◽  
Loss Coefficient ◽  
Leakage Flow ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Gap Flow ◽  
Tip Gap Flow

Modern high pressure turbines operate at high velocity and high temperature conditions. The gap existing above a turbine rotor blade is responsible for an undesirable tip leakage flow. It is a source of high aerodynamic losses and high heat transfer rates. A better understanding of the tip flow behaviour is needed to provide a more efficient cooling design in this region. The objective of this paper is to investigate the tip leakage flow for a blade with two different squealer tips and film-cooling applied on the pressure side and through tip dust holes in a non-rotating, linear cascade arrangement. The experiments were performed in the VKI Light Piston Compression Tube facility, CT-2. The tip gap flow was investigated by oil flow visualisations and by wall static and total pressure measurements. Two geometries were tested — a full squealer and a partial suction side squealer. The measurements were performed in the blade tip region, including the squealer rim and on the corresponding end-wall for engine representative values of outlet Reynolds and Mach numbers. The main flow structures in the cavity were put in evidence. Positive influence of the coolant on the tip gap flow and on the aerodynamic losses was found for the full squealer tip case: increasing the coolant mass-flow increased the tip gap flow resistance. The flow through the clearance therefore slows down, the tip gap mass-flow and the heat transfer respectively decreases. No such effect of cooling was found in the case of the partial suction side squealer geometry. The absence of a pressure side squealer rim resulted in a totally different tip gap flow topology, indifferent to cooling. The influence of cooling on the overall mass-weighted thermodynamic loss coefficient, which takes into account the different energies of the mainstream and coolant flows was found marginal for both geometries. Finally the overall loss coefficient was found to be higher for the partial suction side squealer tip than for the full squealer tip.

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.

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