Conjugate Heat Transfer Enhancement of an Internal Blade Pin-Finned Tip-Wall

2009 ◽  
Author(s):  
Gongnan Xie ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Conjugate Heat Transfer ◽  
Gas Flow ◽  
Turbine Blades ◽  
Thermal Design ◽  
Inlet Temperature ◽  
Computational Domain ◽  
Pin Fins ◽  
Blade Tip

To improve gas turbine performance, the operating temperature has been increased continuously. However, the heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Cooling methods are therefore needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to the hot gas flow and is difficult to cool. A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the three-dimensional turning effect and impingement. Increasing internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip with internal pin-fins has been investigated numerically using a conjugate heat transfer approach. The computational model consists of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap. The computational domain includes the fluid region and the solid pins as well as the solid tip regions. Turbulent convective heat transfer between the fluid and pins, and heat conduction within pins and tip are simultaneously computed. The inlet Reynolds numbers are ranging from 100,000 to 600,000. Details of the 3D fluid flow and heat transfer over the tip surface are presented. A comparison of the overall performance of the two models is presented. It is found that due to the combination of turning impingement and pin-fin cross flow, the heat transfer coefficient of the pin-finned tip is a factor of about 3.0 higher than that of a smooth tip. This augmentation is achieved at the cost of a pressure drop penalty of about 7%. With the conjugate heat transfer method, not only the simulated model is close to the experimental model, but also the distribution of the external tip heat transfer can be relevant for thermal design of turbine blade tips.

scholarly journals Computational Modeling and Thermal Paint Verification of Film-Cooling Designs for an Unshrouded High-Pressure Turbine Blade

1999 ◽  
Author(s):  
Steven G. Gegg ◽  
Nathan J. Heidegger ◽  
Ronald A. Mikkelson
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Turbine Blade ◽  
Film Cooling ◽  
Data Exchange ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
High Pressure Turbine ◽  
Extreme High Temperature ◽  
Blade Tip

High pressure turbine blades are exposed to an extreme high temperature environment due to increasing turbine inlet temperature. High heat fluxes are likely on the blade pressure surface. Other regions, such as the trailing edge and blade tip may be difficult to cool uniformly. Unshrouded blades present an additional challenge due to the pressure driven transport of hot gas across the blade tip. The blade tip region is therefore prone to severe thermal stress, fatigue and oxidation. In order to develop effective cooling methods, designers require detailed flow and heat transfer information. This paper reports on computational aerodynamics and heat transfer studies for an unshrouded high pressure turbine blade. The emphasis is placed on the application of appropriate 3-D models for the prediction of airfoil surface temperatures. Details of the film cooling model, boundary conditions and data exchange with heat transfer models are described. The analysis approach has been refined for design use to provide timely and accurate results. Film cooling designs are to be tailored for the best coverage of the blade tip region. Designs include near-tip pressure side films and blade tip cooling holes. Hole placement and angle are investigated to achieve the best coolant coverage on the blade tip. Analytical results are compared to a thermal paint test on engine hardware. In addition to film cooling strategies, other aerodynamic/heat transfer design approaches are discussed to address the cooling requirements for an unshrouded blade.

Augmented Heat Transfer of Internal Blade Tip Wall With Pin-Fins

2009 ◽  
Author(s):  
G. N. Xie ◽  
B. Sunde´n ◽  
L. Wang ◽  
E. Utriainen
Keyword(s):  
Heat Transfer ◽  
Computational Models ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Inlet Temperature ◽  
Gas Flows ◽  
Pin Fin ◽  
Pin Fins ◽  
Blade Tip

The heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Cooling methods are therefore much needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to the hot gas flows. A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip cap taking advantage of the three-dimensional turning effect and impingement. Improving internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip has been investigated numerically. The computational models consist of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap, and a smooth two-pass channel. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible and stationary. The detailed 3D fluid flow and heat transfer over the tip surfaces are presented. The overall performance of the two models is evaluated. It is found that the pin-fins make the counter-rotating vortices towards pin-fin surfaces, resulting in continuous turbulent mixing near the pin-finned tip. Due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of as much as 1.84 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 35%. It is suggested that the pin-fins could be used to enhance blade tip heat transfer and cooling.

A Numerical Study on Conjugate Heat Transfer for Supercritical CO2 Turbine Blade With Cooling Channels

2020 ◽  
Author(s):  
Akshay Khadse ◽  
Andres Curbelo ◽  
Ladislav Vesely ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Supercritical Co2 ◽  
Conjugate Heat Transfer ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
Cooling Channels ◽  
Blade Cooling ◽  
Turbine Inlet

Abstract The first stage of turbine in a Brayton cycle faces the maximum temperature in the cycle. This maximum temperature may exceed creep temperature limit or even melting temperature of the blade material. Therefore, it becomes an absolute necessity to implement blade cooling to prevent them from structural damage. Turbine inlet temperatures for oxy-combustion supercritical CO2 (sCO2) are promised to reach blade material limit in near future foreseeing need of turbine blade cooling. Properties of sCO2 and the cycle parameters can make Reynolds number external to blade and external heat transfer coefficient to be significantly higher than those typically experience in regular gas turbines. This necessitates evaluation and rethinking of the internal cooling techniques to be adopted. The purpose of this paper is to investigate conjugate heat transfer effects within a first stage vane cascade of a sCO2 turbine. This study can help understand cooling requirements which include mass flow rate of leakage coolant sCO2 and geometry of cooling channels. Estimations can also be made if the cooling channels alone are enough for blade cooling or there is need for more cooling techniques such as film cooling, impingement cooling and trailing edge cooling. The conjugate heat transfer and aerodynamic analysis of a turbine cascade is carried out using STAR CCM+. The turbine inlet temperature of 1350K and 1775 K is considered for the study considering future potential needs. Thermo-physical properties of this mixture are given as input to the code in form of tables using REFPROP database. The blade material considered is Inconel 718.

The Effects of an Excited Impinging Jet on the Local Heat Transfer Coefficient of Aircraft Turbine Blades

1988 ◽  
Author(s):  
P. J. Disimile ◽  
D. M. Paule
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Primary Objective ◽  
Inlet Temperature

The primary objective of this paper is to present the results of research into the effects of periodic excitation upon the local heat transfer characteristics of a turbine blade cooled by an impinging jet of air. A curved plate (used to simulate the inner leading edge of a turbine blade) was subjected to a two-dimensional jet flow field (Re = 10,000) with a superimposed periodic acoustic disturbance. When compared to the naturally disturbed flow, the excited flow field was found to reduce the local Nusselt number and cool the blade less efficiently (by as much as ten percent in the extreme cases). The results of the study appear to indicate that harmonic disturbances present a serious controlling factor in the quest for optimization of turbine blade cooling techniques. By isolating dominant frequencies in gas turbine engines and working to suppress them, the authors believe it possible to make significant contributions towards the desired increase in turbine inlet temperature.

Computational Modeling of Tip Heat Transfer to a Superscale Model of an Unshrouded Gas Turbine Blade

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Brian M. T. Tang ◽  
Pepe Palafox ◽  
Brian C. Y. Cheong ◽  
Martin L. G. Oldfield ◽  
David R. H. Gillespie
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Computational Study ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Tip Leakage Flow ◽  
Blade Tip

Control of over-tip leakage flow between turbine blade tips and the stationary shroud is one of the major challenges facing gas turbine designers today. The flow imposes large thermal loads on unshrouded high pressure (HP) turbine blades and is significantly detrimental to turbine blade life. This paper presents results from a computational study performed to investigate the detailed blade tip heat transfer on a sharp-edged, flat tip HP turbine blade. The tip gap is engine representative at 1.5% of the blade chord. Nusselt number distributions on the blade tip surface have been obtained from steady flow simulations and are compared with experimental data carried out in a superscale cascade, which allows detailed flow and heat transfer measurements in stationary and engine representative conditions. Fully structured, multiblock hexahedral meshes were used in the simulations performed in the commercial solver FLUENT. Seven industry-standard turbulence models and a number of different tip gridding strategies are compared, varying in complexity from the one-equation Spalart–Allmaras model to a seven-equation Reynolds stress model. Of the turbulence models examined, the standard k-ω model gave the closest agreement to the experimental data. The discrepancy in Nusselt number observed was just 5%. However, the size of the separation on the pressure side rim was underpredicted, causing the position of reattachment to occur too close to the edge. Other turbulence models tested typically underpredicted Nusselt numbers by around 35%, although locating the position of peak heat flux correctly. The effect of the blade to casing motion was also simulated successfully, qualitatively producing the same changes in secondary flow features as were previously observed experimentally, with associated changes in heat transfer with the blade tip.

Research on Aerodynamic Characteristics of Air-Cooled Turbine Blade with Conjugate Heat Transfer Method

2013 ◽  
Vol 732-733 ◽  
pp. 270-275
Author(s):  
Jing Jing Zhang ◽  
Lian Fu Wang ◽  
Xiang Jun Fang
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Conjugate Heat Transfer ◽  
Air Flow ◽  
Aerodynamic Characteristics ◽  
Cooling Effect ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Transfer Method ◽  
Aero Engines

In order to improve the performance of aero engines, trying to increase the turbine inlet temperature is an important way. But the turbine inlet temperature of modern aero engines can be more than 2000 K, which is far more than what the materials can bear. So advanced cooling technologies should be introduced to solve this problem. Using the conjugate heat transfer method, this paper researched the aerodynamic characteristics of a certain turbine blade with complex cooling structures. Some conclusions can be drawn: the velocity of the air flow and different distributions of coolant flow for turbine blade with multiple cooling air inlets have great influence on the cooling effect; the cooling effect decreases as the temperature ratio decreases; with the same mass cold gas, the less film cooling holes, the worse cooling effect; therefore, a reasonable air flow distribution plays an important role in obtaining good cooling effect.

Investigation of a Rotor Blade With Tip Cooling Subject to a Nonuniform Temperature Profile

2020 ◽  
Author(s):  
Harika S. Kahveci
Keyword(s):  
Heat Transfer ◽  
Temperature Profile ◽  
Turbine Blade ◽  
Inlet Temperature ◽  
Pressure Side ◽  
Tip Leakage Flow ◽  
Engine Operation ◽  
Pressure Losses ◽  
Blade Tip ◽  
The Impact

Abstract One of the challenges in the design of a high-pressure turbine blade is that a considerable amount of cooling is required so that the blade can survive high temperature levels during engine operation. Another challenge is that the addition of cooling should not adversely affect blade aerodynamic performance. Besides, the tip region of a blade is exposed to further complexities due to tip leakage flow that is known to affect flow features and to cause additional pressure losses. The typical flat tips used in designs have evolved into squealer form that implements rims on the tip, which has been reported in several studies to achieve better heat transfer characteristics as well as to decrease pressure losses at the tip. This paper demonstrates a numerical study focusing on a squealer turbine blade tip that is operating in a turbine environment matching the typical design ratios of pressure, temperature and coolant blowing. The blades rotate at a realistic rpm and are subjected to a turbine rotor inlet temperature profile that has a nonuniform shape. For comparison, a uniform profile is also considered as it is typically used in computational studies for simplicity. The model used in the simulations is the tip section of the GE-E3 first stage blade. Two different configurations with and without cooling are considered using the same tip geometry. The cooled blade tip has seven holes on the tip floor lined up near the blade pressure side. The paper demonstrates the impact of the temperature profile nonuniformity and the addition of cooling on the complex blade tip flow field and heat transfer. Results confirm that these boundary conditions are the drivers for loss generation, and they further increase losses when combined. Temperature profile migration is not pronounced with a uniform profile, but shows distinct features with a nonuniform profile for which hot gas migration toward the blade pressure side is clearly observed. The blade tip also receives higher coolant coverage when subject to the nonuniform profile.

Optimization of a high pressure turbine blade tip cavity with conjugate heat transfer analysis

2016 ◽  
Vol 30 (12) ◽  
pp. 5529-5538 ◽  
Author(s):  
Jinuk Kim ◽  
Young Seok Kang ◽  
Dongwha Kim ◽  
Jihyeong Lee ◽  
Bong Jun Cha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Turbine Blade ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Analysis ◽  
High Pressure Turbine ◽  
Blade Tip

Simultaneous Prediction of External Flow-Field and Temperature in Internally Cooled 3-D Turbine Blade Material

2000 ◽  
Author(s):  
Zhen-Xue Han ◽  
Brian H. Dennis ◽  
George S. Dulikravich
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Conjugate Heat Transfer ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Heat Fluxes ◽  
Bulk Temperature ◽  
Transfer Coefficients ◽  
Internally Cooled

A two-dimensional (2-D) and a three-dimensional (3-D) conjugate heat transfer (convection-conduction) prediction codes were developed where the compressible turbulent flow Navier-Stokes equations are solved simultaneously in the flow-field and in the solid material of the structure thus automatically predicting correct magnitudes and distribution of surface temperatures and heat fluxes. The only thermal boundary conditions are the convection heat transfer coefficients specified on the surfaces of the internal coolant flow passages and the coolant bulk temperature of internally cooled gas turbine blade. This approach eliminates the need to specify hot surface temperature or heat flux distribution. The conjugate codes use hybrid unstructured triangular/quadrilateral grids in 2-D and unstructured prismatic grids in 3-D throughout the flow-field and in the surrounding structure. The codes are capable of conjugate heat transfer prediction in arbitrarily shaped internally cooled configurations. The computer codes have been successfully tested on internally cooled turbine airfoil cascades and 3-D turbine blades by the conjugate solution of the flow-field and the temperature field inside the structure.

Numerical Evaluation of Pin Fin Inclination by Conjugate Heat Transfer Simulation With URANS

2015 ◽  
Author(s):  
Takashi Yamane
Keyword(s):  
Heat Transfer ◽  
Thermal Conduction ◽  
Conjugate Heat Transfer ◽  
Turbine Blades ◽  
Flow Region ◽  
Cooling Performance ◽  
Pin Fin ◽  
Blade Cooling ◽  
Pin Fins ◽  
Heat Transfer Simulation

Short pin fins are often used as one of the blade cooling technologies inside the trailing edge of turbine blades. In our previous study we focused on the effects of pin inclination for overall cooling performance especially including heat conduction between the pins and endwall by both experiments and the conjugate heat transfer simulations, then the forwardly inclined pin-fins are found to effectively enhance the cooling, but we also found that the steady conjugate heat transfer simulation underestimates the cooling performance of the straight pin-fins due to highly unsteady flow structure. In this study the URANS is coupled with the steady thermal conduction by using the time smoothing method in the flow region, thus the underestimate of the heat transfer for the straight pin-fins was significantly improved.

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