scholarly journals High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

Aerospace ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 124 ◽  
Author(s):  
Danesh Tafti ◽  
Cody Dowd ◽  
Xiaoming Tan
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Turbine Blades ◽  
Computational Cost ◽  
Reynold Number ◽  
Secondary Flows ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Eddy Simulation ◽  
Turbulent Statistics

Cooling of gas turbine blades is critical to long term durability. Accurate prediction of blade metal temperature is a key component in the design of the cooling system. In this design space, spatial distribution of heat transfer coefficients plays a significant role. Large-Eddy Simulation (LES) has been shown to be a robust method for predicting heat transfer. Because of the high computational cost of LES as Reynolds number (Re) increases, most investigations have been performed at low Re of O(104). In this paper, a two-pass duct with a 180° turn is simulated at Re = 100,000 for a stationary and a rotating duct at Ro = 0.2 and Bo = 0.5. The predicted mean and turbulent statistics compare well with experiments in the highly turbulent flow. Rotation-induced secondary flows have a large effect on heat transfer in the first pass. In the second pass, high turbulence intensities exiting the bend dominate heat transfer. Turbulent intensities are highest with the inclusion of centrifugal buoyancy and increase heat transfer. Centrifugal buoyancy increases the duct averaged heat transfer by 10% over a stationary duct while also reducing friction by 10% due to centrifugal pumping.

Laminar and Transitional Boundary Layer Structures in Accelerating Flow With Heat Transfer

1986 ◽  
Vol 108 (1) ◽  
pp. 116-123 ◽  
Author(s):  
K. Rued ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Pressure Gradients ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients ◽  
Layer Structures ◽  
Flow Heat

The accurate prediction of heat transfer coefficients on cooled gas turbine blades requires consideration of various influence parameters. The present study continues previous work with special efforts to determine the separate effects of each of several parameters important in turbine flow. Heat transfer and boundary layer measurements were performed along a cooled flat plate with various freestream turbulence levels (Tu = 1.6−11 percent), pressure gradients (k = 0−6 × 10−6), and cooling intensities (Tw/T∞ = 1.0−0.53). Whereas the majority of previously available results were obtained from adiabatic or only slightly heated surfaces, the present study is directed mainly toward application on highly cooled surfaces as found in gas turbine engines.

Turbulent Flow and Heat Transfer in Variable Geometry U-Bend Blade Cooling Passage

2009 ◽  
Author(s):  
Krishna Guntur ◽  
R. S. Amano ◽  
Jose Martinez Lucci
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Model Simulation ◽  
Turbine Blades ◽  
Higher Order ◽  
Secondary Flows ◽  
Gas Turbine Blades ◽  
Cooling Passage ◽  
Les Model

In modern gas turbine blades it has been a common practice to use cooling passages in gas turbine blades. In cooling processes blades have excessive thermal stresses, causing creep, oxidizing and also melting in some cases. Therefore fully understanding of the flow characteristics in the U-bend is important in designing cooling passages. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, and to improve the cooling performance, both refined turbulence models and higher-order numerical schemes are indispensable tools for turbine designers. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method achieves accurate computations. The three-dimensional turbulent flows and heat transfer in a square U-bend duct are numerically studied by using a Large Eddy Simulation (LES) model. Simulation using k-ω, k-ε and RSM models has been previously reported, and used here to compare with the LES simulation. The finite volume method incorporated with higher-order bounded interpolation scheme has been employed in the present study. The objective of this study is to validate the simulation of LES model with the experimental results. Three different Reynolds numbers, 36000, 60000 and 100000, were used. This study concludes that the RSM is a better model, for Re = 36,000 and 60,000.

Calculation of Heat Transfer to Convection-Cooled Gas Turbine Blades

1985 ◽  
Vol 107 (3) ◽  
pp. 620-627 ◽  
Author(s):  
W. Rodi ◽  
G. Scheuerer
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Complex Nature ◽  
Surface Boundary ◽  
Transfer Coefficients ◽  
Free Stream Turbulence ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients

A mathematical model is presented for calculating the external heat transfer coefficients around gas turbine blades. The model is based on a finite-difference procedure for solving the boundary-layer equations which describe the flow and temperature field around the blades. The effects of turbulence are simulated by a low-Reynolds number version of the k-ε turbulence model. This allows calculation of laminar and transitional zones and also the onset of transition. Applications of the calculation method are presented to turbine-blade situations which have recently been investigated experimentally. Predicted and measured heat transfer coefficients are compared and good agreement with the data is observed. This is true especially for the pressure-surface boundary layer which is of a rather complex nature because it remains in a transitional state over the full blade length. The influence of various flow phenomena like laminar-turbulent transition and of the boundary conditions (pressure gradient, free-stream turbulence) on the predicted heat transfer rates is discussed.

Numerical Investigation of Convective Heat Transfer and Pressure Drop for Ribbed Surfaces in the Bend Part of a U-Duct

2012 ◽  
Author(s):  
Tareq Salameh ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Gas Turbine Blades ◽  
Cross Section Area ◽  
Duct Geometry ◽  
Energy Equations

This work concerns two-dimensional numerical simulations of the flow and temperature fields inside smooth and ribbed bend (turn) parts of a U-duct with relevance for internal tip cooling of gas turbine blades. The ribs are placed internally on the outermost bend surface. The renormalization group (RNG) k-ε turbulence model was used to solve the momentum and energy equations inside the bend (turn) part as well in the supply and return straight parts of the U-duct. For the ribbed surface three different rib configurations were simulated, namely (a) single rib at three different rib positions, i.e., inlet, middle and outlet, (b) two ribs for three different configurations, i.e., at the inlet and middle, at the middle and outlet as well as at the inlet and outlet, and (c) three ribs. The rib height-to-hydraulic diameter ratio, e/Dh, was 0.1, the pitch ratios were 13.5 and 27 and the Reynolds number was 20000. The details of the duct geometry were as follows: the cross section area of the straight part was 50×50 mm2, the inside length of the bend part was 240 mm. The results were compared with experimental data obtained at similar conditions. The numerical results were closer to the experimental ones for those cases with the rib at the inlet position than for the cases with the rib at the middle position. The case of two ribs at the inlet and middle gave the highest heat transfer coefficients while the case of a single rib at the middle gave the highest local pressure coefficient of all cases.

Aerodynamic Performance of Porous Gas Turbine Blades

1969 ◽  
Vol 73 (705) ◽  
pp. 789-796 ◽  
Author(s):  
F. J. Bayley ◽  
G. R. Wood
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
High Heat ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Aero Engines ◽  
Cooling Air

If maximum gas temperatures aire to rise appreciably above 1500°K, the value currently achieved in advanced aero-engines, alternatives to the present internal convective methods of air-cooling the first-stage turbine blades will have to be sought. One of the most promising developments lies in the use of porous blade materials, through which cooling air can be “effused” or “transpired”. In a recent paper Bayley and Turner have shown that by the combination of high heat transfer coefficients within the interstices of the porous material, and a reduction in heat transfer rate by injection into the boundary layer on the hot-gas side of the blade, effective cooling rates can be achieved.

Determination of Heat Transfer Coefficients Around a Blade Surface From Temperature Measurements

1979 ◽  
Author(s):  
D. K. Mukherjee
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Main Stream ◽  
Blade Surface ◽  
Transfer Coefficients ◽  
Gas Turbine Blades ◽  
Heat Transfer Coefficients

To design cooled gas turbine blades, heat transfer coefficients around its surface are required. The calculated heat transfer data under operating conditions in the turbine are often inaccurate and require experimental verification. A method is presented here to determine the heat transfer coefficients around the blade surface and in the coolant channels. This requires measurements of the main stream and coolant temperatures together with the outer surface temperature distribution at varying mass flows. In order to conduct these tests in a gas turbine, test blades have to be specially prepared allowing the variation and measurement of coolant mass flow.

Thermal Analysis of Cooling System in a Gas Turbine Transition Piece

2011 ◽  
Author(s):  
Jun Su Park ◽  
Namgeon Yun ◽  
Hokyu Moon ◽  
Kyung Min Kim ◽  
Sin-Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Cooling System ◽  
Structural Information ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Transfer Coefficients ◽  
Transition Piece ◽  
Inlet Conditions

This paper presents thermal analyses of the cooling system of a transition piece, which is one of the primary hot components in a gas turbine engine. The thermal analyses include heat transfer distributions induced by heat and fluid flow, temperature, and thermal stresses. The purpose of this study is to provide basic thermal and structural information on transition piece, to facilitate their maintenance and repair. The study is carried out primarily by numerical methods, using the commercial software, Fluent and ANSYS. First, the combustion field in a combustion liner with nine fuel nozzles is analyzed to determine the inlet conditions of a transition piece. Using the results of this analysis, pressure distributions inside a transition piece are calculated. The outside of the transition piece in a dump diffuser system is also analyzed. Information on the pressure differences is then used to obtain data on cooling channel flow (one of the methods for cooling a transition piece). The cooling channels have exit holes that function as film-cooling holes. Thermal and flow analyses are carried out on the inside of a film-cooled transition piece. The results are used to investigate the adjacent temperatures and wall heat transfer coefficients inside the transition piece. Overall temperature and thermal stress distributions of the transition piece are obtained. These results will provide a direction to improve thermal design of transition piece.

Cooling of a Finned Cylinder by a Jet Flow of Air

2002 ◽  
Author(s):  
F. Gori ◽  
F. De Nigris ◽  
E. Pippione ◽  
G. Scavarda
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Flow ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Electric System ◽  
Heavy Trucks ◽  
Turbo Compressor ◽  
University Of Rome ◽  
The University

The paper describes a patented proposal to use jets of air in the cooling system of heavy trucks. Preliminary tests have been carried out, in the Heat Transfer Laboratory of the University of Rome “Tor Vergata”, to evaluate the heat transfer characteristics of a jet flow of air, impinging onto an externally finned cylinder. The cylinder is internally heated with an electric system. Thermocouples, located inside the cylinder, allow to measure the wall temperatures, in order to calculate the local and average convective heat transfer coefficients. A preliminary design of the practical apparatus, applied to heavy trucks, has been done in cooperation with Iveco. Nozzles are designed to be put after the fan of heavy trucks to converge air, in the form of jets, onto the tube where the charged air is flowing from the outlet of the turbo-compressor. The efficiency of the jet flow increases the cooling performances but, due to the high temperature at the outlet of the turbo-compressor, it may not be enough. The heat transfer cooling performances are enhanced if the tube to be cooled is externally finned. Some preliminary experiments have been carried out in a real scale bank test of an heavy truck engine at the Engineering Testing Laboratories Department of Iveco. Comparisons are done between the experiments and a simple theoretical model. Some conclusions are drawn about the cooling at different fluid dynamics conditions of the impinging jets.

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