Thermal Validation of a Heat Shield Surface for a High Lift Blade Profile

2011 ◽  
Author(s):  
M. Cochet ◽  
W. Colban ◽  
M. Gritsch ◽  
S. Naik ◽  
M. Schnieder
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Heat Shield ◽  
Transfer Coefficients ◽  
High Lift ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
The Impact

Low emission requirements for heavy-duty gas turbines can be achieved with flat combustor temperature profiles, reducing the combustor peak temperature. As a result, the heat load on the first stage heat shield above the first stage blade increases. High lift airfoils cause increased thermal loading on the heat shield above the blade tip and impact the unavoidable secondary flows, including complex vortex flows. Cascade tests have been performed on a blade with a generic high lift profile and the results on the heat shield are presented. A transient thermochromic liquid crystal measurement technique was used to obtain heat transfer coefficients on the heat shield surface. Several variations of blade tip clearance were investigated, and the impact on heat transfer coefficients is shown. Computational fluid dynamics predictions are compared to the experimental data to interpret the data and validate the CFD.

Validation of a First Vane Platform Cooling Design

2011 ◽  
Author(s):  
Joerg Krueckels ◽  
William Colban ◽  
Michael Gritsch ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Design Data ◽  
High Lift ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients

Low emission requirements for large industrial gas turbines can be achieved with flat combustor temperature profiles reducing the combustor peak temperature. As a result the heat load on the first stage vane platforms increases and platform film cooling is an important requirement. Furthermore, high lift airfoils generate stronger secondary flows including complex vortex flows over the platforms, which impacts heat transfer coefficients and film cooling. Cascade tests have been performed on a high lift profile with a platform film configuration and will be presented. The linear cascade was operated at engine representative Mach numbers. Pressure measurements are compared to design data to ensure correct operating conditions and periodicity of the cascade. The thermochromic liquid crystal measurement technique is used to obtain adiabatic film cooling effectiveness. The upstream gap (corresponding to the gap between the combustor and turbine) and the purge air exiting this gap are included in the investigations. The effect of the purge air on the recovery temperature is very strong and needs to be taken into account for the layout of the cooling scheme. The heat transfer coefficient distribution on the platform is obtained for an uncooled configuration using a transient infrared imaging technique with heat flux reconstruction. Computational fluid dynamics (CFD) assessments are used to support the validation results. Heat transfer coefficients and the effect of the purge air on adiabatic wall temperatures are compared with experimental results.

Influence of Passage Flow on Tip Film Cooling Characteristics

2012 ◽  
Author(s):  
Jin Wang ◽  
Yong Yu ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio ◽  
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 different blade spans and different blowing ratios on the tip flow and cooling performance was revealed with the k-ε model. For the squealer tip, the depth of the cavity and the height of the tip clearance were fixed, the influence of different spans (10%, 25%, 50%, 75% and 100% span) on the tip heat transfer was investigated. It was found that the velocity field above the blade tip and the heat transfer distribution on the groove floor for the 10% span (cut-back span) model had no difference from that for the 100% span (whole span) model obviously. However, the leakage flow for the 10% span model showed larger interaction with the passage flow. With different spans, the effect of different blowing ratios, i.e., M = 0.4, 0.8 and 1.2, was investigated. Increasing the blowing ratio (from M = 0.4 to 1.2) increased the film cooling effectiveness and made the heat transfer coefficients of all the models smaller. Because the cut-back model for the 10% span had similar tip flow field with the 100% span model, the simulation for the 10% span model could be used to find out the tip flow and heat transfer for the 100% span model.

Three-Dimensional RANS Prediction of Gas-Side Heat Transfer Coefficients on Turbine Blade and Endwall

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Radial Profile ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Heat Transfer Coefficients ◽  
The Impact

This paper presents a study using 3D computational fluid dynamics (CFD) based on Reynolds-averaged Navier-Stokes (RANS) equations to predict turbine gas-side heat transfer coefficients (HTC) on the entire airfoil and endwall. The CFD results at different spanwise sections and endwall have been compared with the flat-plate turbulent boundary layer correlation and with the data in a NASA turbine rotor passage with strong secondary flows, under three different flow conditions. The enhancement effects of secondary flow vortices on the blade surface and endwall heat transfer rate have been examined in detail. Analyses were conducted for the impact of Reynolds number and exit Mach number on heat transfer. The SST, k-ɛ, V2F, and realizable k-ɛ turbulence models have been assessed. The classical log-law wall-functions have been found to be comparable to the wall-integration methods but with much reduced sensitivity to inlet turbulence conditions. The migration of hot gas was simulated with a radial profile of inlet temperature. CFD results for mid-span HTCs of two other airfoils were also compared with test data. Overall, results are encouraging and indicate improved HTC and temperature predictions from 3D CFD could help optimize the design of turbine cooling schemes.

3D RANS Prediction of Gas-Side Heat Transfer Coefficients on Turbine Blade and Endwall

2011 ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Radial Profile ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Wall Functions ◽  
Heat Transfer Coefficients ◽  
The Impact

This paper presents a study using 3D computational fluid dynamics (CFD) based on Reynolds-averaged Navier-Stokes (RANS) equations to predict turbine gas-side heat transfer coefficients (HTC) on the entire airfoil and endwall. The CFD results at different spanwise sections and endwall have been compared with the flat-plate turbulent boundary layer correlation and with the data in a NASA turbine rotor passage with strong secondary flows, under three different flow conditions. The enhancement effects of secondary flow vortices on the blade surface and endwall heat transfer rate have been examined in detail. Analyses were conducted for the impact of Reynolds number and exit Mach number on heat transfer. The SST, k-ε, V2F, and realizable k-ε turbulence models have been assessed. The classical log-law wall-functions have been found to be comparable to the wall-integration methods, but with much reduced sensitivity to inlet turbulence conditions. The migration of hot gas was simulated with a radial profile of inlet temperature. CFD results for mid-span HTCs of two other airfoils were also compared with test data. Overall results are encouraging and indicate improved HTC and temperature predictions from 3D CFD could help optimize the design of turbine cooling schemes.

scholarly journals Heat Transfer and Flow on the Blade Tip of a Gas Turbine Equipped With a Mean-Camberline Strip

2001 ◽  
Vol 123 (4) ◽  
pp. 704-708 ◽  
Author(s):  
A. A. Ameri
Keyword(s):  
Heat Transfer ◽  
Sharp Edge ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Large Power ◽  
Tip Leakage ◽  
Numerical Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
Convective Heat Transfer Coefficients

Experimental and computational studies have been performed to investigate the detailed distribution of convective heat transfer coefficients on the first-stage blade tip surface for a geometry typical of large power generation turbines (>100 MW). In a previous work the numerical heat transfer results for a sharp edge blade tip and a radiused blade tip were presented. More recently several other tip treatments have been considered for which the tip heat transfer has been measured and documented. This paper is concerned with the numerical prediction of the tip surface heat transfer for radiused blade tip equipped with mean-camberline strip (or “squealer” as it is often called). The heat transfer results are compared with the experimental results and discussed. The effectiveness of the mean-camberline strip in reducing the tip leakage and the tip heat transfer as compared to a radiused edge tip and sharp edge tip was studied. The calculations show that the sharp edge tip works best (among the cases considered) in reducing the tip leakage flow and the tip heat transfer.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low Speed Cascade

2003 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83 × 105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

The Impact of Fin Deformation on Condensation Heat Transfer Coefficients in Internally Grooved Tubes

2013 ◽  
Author(s):  
Sunil Mehendale
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Thermal Contact ◽  
Heat Pumps ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Condensing Heat Transfer ◽  
The Impact ◽  
Tube Expansion

In HVACR equipment, internally enhanced round tube (microfin) designs such as axial, cross-grooved, helical, and herringbone are commonly used to enhance the boiling and condensing performance of evaporators, condensers, and heat pumps. Typically, such tubes are mechanically expanded by a mandrel into a fin pack to create an interference fit between the tube outside surface and the fin collar to minimize the thermal contact resistance between tube and fin. However, during this expansion process, the internal enhancements undergo varying amounts of deformation, which degrades the in-tube thermal performance. Extensive data on condensing heat transfer coefficients in microfin tubes have been reported in the open literature. However, researchers have seldom used expanded tubes to acquire and report such data. Hence, it is always questionable to use such pristine tube data for designing heat exchangers and HVACR systems. Furthermore, the HVACR industry has been experiencing steeply rising copper costs, and this trend is expected to continue in coming years. So, many equipment manufacturers and suppliers are actively converting tubes from copper to aluminum. However, because of appreciable differences between the material properties of aluminum and copper, as well as other manufacturing variables, such as mandrel dimensions, lubricant used, etc., tube expansion typically deforms aluminum fins more than copper fins. Based on an analysis of the surface area changes arising from tube expansion, and an assessment of the best extant in-tube condensation heat transfer correlations, this work proposes a method of estimating the impact of tube expansion on in-tube condensation heat transfer. The analysis leads to certain interesting and useful findings correlating fin geometry and in-tube condensation thermal resistance. This method can then be applied to more realistically design HVACR heat exchangers and systems.

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.

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