Assessment of Turbulence Models for a Single-Injector Cooling Flow

2022 ◽  
Author(s):  
Dennis A. Yoder
Keyword(s):  
Turbulence Models ◽  
Cooling Flow

Computational Predictions of Heat Transfer and Film-Cooling for a Turbine Blade With Nonaxisymmetric Endwall Contouring

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbine Engine ◽  
Cooling Flow ◽  
Endwall Contouring ◽  
Dynamics Simulations ◽  
Endwall Film Cooling

Three-dimensional contouring of the compressor and turbine endwalls in a gas turbine engine has been shown to be an effective method of reducing aerodynamic losses by mitigating the strength of the complex vortical structures generated at the endwall. Reductions in endwall heat transfer in the turbine have been also previously measured and reported in literature. In this study, computational fluid dynamics simulations of a turbine blade with and without nonaxisymmetric endwall contouring were compared to experimental measurements of the exit flowfield, endwall heat transfer, and endwall film-cooling. Secondary kinetic energy at the cascade exit was closely predicted with a simulation using the SST k-ω turbulence model. Endwall heat transfer was overpredicted in the passage for both the SST k-ω and realizable k-ε turbulence models, but heat transfer augmentation for a nonaxisymmetric contour relative to a flat endwall showed fair agreement to the experiment. Measured and predicted film-cooling results indicated that the nonaxisymmetric contouring limits the spread of film-cooling flow over the endwall depending on the interaction of the film with the contour geometry.

Direct Numerical Simulation of a Film Cooling Jet

2004 ◽  
Author(s):  
Frank Muldoon ◽  
Sumanta Acharya
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Film Cooling ◽  
Dissipation Rate ◽  
Turbulence Models ◽  
Numerical Data ◽  
Rate Equations ◽  
Wall Function ◽  
Accurate Representation ◽  
Cooling Flow

Direct Numerical Simulation (DNS) of a film cooling jet is presented. In DNS no turbulence models are introduced, and the turbulent length scales in the flow field are fully resolved. Therefore the calculations are expected to provide an accurate representation of reality, and the numerical data can be used to understand the flow physics and to compute turbulence budgets. In this paper, a DNS for an inclined jet at a jet Reynolds number of 3068 is presented. Statistics for the various budgets in the turbulence kinetic energy and dissipation rate equations are computed and presented to provide a basis for improvements to the turbulence models. A new wall function based on DNS results for a film cooling flow is presented.

The Optimal Distribution of Pin Fins for Blade Tip Cap Underside Cooling

2013 ◽  
Author(s):  
Gustavo A. Ledezma ◽  
Ronald S. Bunker
Keyword(s):  
Turbulence Models ◽  
Geometric Optimization ◽  
Pin Fin ◽  
Cooling Flow ◽  
Liquid Crystal Thermography ◽  
Optimization Study ◽  
Pin Fins ◽  
Rans Turbulence Models ◽  
Optimal Spacing ◽  
Blade Tip

This article presents a geometric optimization study to maximize the total heat transfer rate between an array of discrete pin fins and the surrounding serpentine cooling flow. The fins are installed on the tip cap underside of a High Pressure Turbine blade model. The study has three parts. In the first, the numerical model is validated against experimental data obtained with liquid crystal thermography. In the second part, the heat and fluid flow performance of the pin fin assembly is simulated numerically, using RANS turbulence models in the range 25,000 < Re < 100,000 and Pr ∼ 0.7. The effect of varying the spacing and the tip cap boundary condition is investigated. In the last part of the study it is shown that the optimal spacing between the pin fins can be correlated following the same theoretical arguments derived in previous investigations that used simpler geometries.

Computational Predictions of Heat Transfer and Film-Cooling for a Turbine Blade With Non-Axisymmetric Endwall Contouring

2010 ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
Atul Kohli ◽  
Christopher Lehane
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbine Engine ◽  
Cooling Flow ◽  
Endwall Contouring ◽  
Dynamics Simulations ◽  
Endwall Film Cooling

Three-dimensional contouring of the compressor and turbine endwalls in a gas turbine engine has been shown to be an effective method of reducing aerodynamic losses by mitigating the strength of the complex vortical structures generated at the endwall. Reductions in endwall heat transfer in the turbine have been also previously measured and reported in the literature. In this study, computational fluid dynamics simulations of a turbine blade with and without non-axisymmetric endwall contouring were compared to experimental measurements of the exit flowfield, endwall heat transfer and endwall film-cooling. Secondary kinetic energy at the cascade exit was closely predicted with a simulation using the SST k-ω turbulence model. Endwall heat transfer was overpredicted in the passage for both the SST k-ω and realizable k-ε turbulence models, but heat transfer augmentation for a non-axisymmetric contour relative to a flat endwall showed fair agreement to the experiment. Measured and predicted film-cooling results indicated that the non-axisymmetric contouring limits the spread of film-cooling flow over the endwall depending upon the interaction of the film with the contour geometry.

scholarly journals Computation of a Leading–Edge Film Cooling Flow Over an Experimental Geometry

1997 ◽  
Author(s):  
Siddharth Thakur ◽  
Jeffrey Wright ◽  
Wei Shyy
Keyword(s):  
Film Cooling ◽  
Turbulence Models ◽  
Leading Edge ◽  
Correction Algorithm ◽  
Wall Functions ◽  
Cooling Flow ◽  
Test Geometry ◽  
Key Features ◽  
Grid Points ◽  
Experimental Geometry

Computations are performed to simulate a leading edge film cooling flow over an experimental test geometry. An in-house CFD–heat transfer code based on a pressure correction algorithm is used for the computations. The code allows the use of multiple blocks in the domain with discontinuous grid lines while maintaining flux conservation at block interfaces. A second–order TVD–based controlled variation scheme (CVS) is used for discretization, along with k–ε models with options of using wall functions or low–Reynolds number modifications. From the viewpoint of incorporating CFD into the design process with fast turn–around times, the approach taken in this study is to attempt to simulate the key features of the flowfield with a reasonable grid size, preferably consisting of no more than 250,000 grid points. In order to attain the desired accuracy with these constraints, effective combinations of grid distribution, discretization operators and turbulence models are investigated, and the sensitivity of the computed solution to these factors examined. The results agree qualitatively with the experimental data though some notable quantitative differences can be observed. An attempt is made to explain the key features of the flowfield resulting from the interaction of coolant jets with the hot freestream.

An Investigation Into Numerical Analysis Alternatives for Predicting Re-Ingestion in Turbine Disc Rim Cavities

2012 ◽  
Author(s):  
Antonio Guijarro Valencia ◽  
Jeffrey A. Dixon ◽  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Peter E. J. Smith ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Turbulence Models ◽  
Research Programme ◽  
Paper Analysis ◽  
Main Stream ◽  
Cfd Modelling ◽  
Cooling Flow ◽  
Air Supply ◽  
Modelling Techniques ◽  
Cooling Air

Reliable means of predicting ingestion in cavities adjacent to the main gas path are increasingly being sought by engineers involved in the design of gas turbines. In this paper, analysis is to be presented that results from an extended research programme, MAGPI, sponsored by the EU and several leading gas turbine manufactures and universities. Extensive use is made of CFD modelling techniques to understand the aerodynamic behaviour of a turbine stator well cavity, focusing on the interaction of cooling air supply with the main annulus gas. The objective of the study has been to benchmark a number of CFD codes and numerical techniques covering RANS and URANS calculations with different turbulence models in order to assess the suitability of the standard settings used in the industry for calculating the mechanics of the flow travelling between cavities in a turbine through the main gas path. The modelling methods employed have been compared making use of experimental data gathered from a dedicated two-stage turbine rig, running at engine representative conditions. Extensive measurements are available for a range of flow conditions and alternative cooling arrangements. The limitations of the numerical methods in calculating the interaction of the cooling flow egress and the main stream gas, and subsequent ingestion into downstream cavities in the engine (i.e. re-ingestion), have been exposed. This has been done without losing sight of the validation of the CFD for its use for predicting heat transfer, which was the main objective of the partners of the MAGPI Work-Package 1 consortium.

The Optimal Distribution of Pin Fins for Blade Tip Cap Underside Cooling

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Gustavo A. Ledezma ◽  
Ronald S. Bunker
Keyword(s):  
Turbulence Models ◽  
Geometric Optimization ◽  
Pin Fin ◽  
Cooling Flow ◽  
Liquid Crystal Thermography ◽  
Optimization Study ◽  
Pin Fins ◽  
Rans Turbulence Models ◽  
Optimal Spacing ◽  
Blade Tip

This article presents a geometric optimization study to maximize the total heat transfer rate between an array of discrete pin fins and the surrounding serpentine cooling flow. The fins are installed on the tip cap underside of a high-pressure turbine blade (HPTB) model. The study has three parts. In the first, the numerical model is validated against experimental data obtained with liquid crystal thermography. In the second part, the heat and fluid flow performance of the pin fin assembly is simulated numerically, using RANS turbulence models in the range 25,000 < Re < 100,000 and Pr ∼ 0.7. The effect of varying the spacing and the tip cap boundary condition is investigated. In the last part of the study, it is shown that the optimal spacing between the pin fins can be correlated following the same theoretical arguments derived in the previous investigations that used simpler geometries.

Towards an Understanding of Traverse Migration in the High Pressure Stage of a Gas Turbine: Effects of Geometry Fidelity and Turbulence Modelling

2017 ◽  
Author(s):  
Karthik Srinivasan ◽  
Simon Bather
Keyword(s):  
High Pressure ◽  
Turbulence Model ◽  
Film Cooling ◽  
Hot Spot ◽  
Turbulence Models ◽  
Turbulence Modelling ◽  
Turbine Stage ◽  
Cooling Flow ◽  
Component Design ◽  
Radial Profiles

The aerodynamic design of a turbine stage requires the accurate prediction of radial profiles of pressure, temperature and velocity at various axial locations within the turbine stage. In the case of hot gas path components like the High Pressure Turbine (HPT), which is located downstream of the combustor, the location of the hot spot and its migration through the stage is critical in arriving at an appropriate aerofoil cooling flow requirement and distribution. In addition, the migration of the flow and the evolution of the temperature traverse through the stage impacts the aerodynamic efficiency of the stage. This is predicted using CFD techniques and has been an inevitable part of the design process. Typically, the fidelity of the computational model evolves with the component design. During early design phases, simplistic geometry is used for the simulations and progressively the fidelity is increased to resolve the geometrical features of interest, like that of the end wall film cooling and rim seal cavity geometries. The present paper provides an improved understanding of the temperature evolution in a HP turbine stage, particularly with respect to the geometry fidelity and the choice of turbulence models. Computational analyses are carried out using the Rolls-Royce in-house CFD solver, HYDRA. The geometry fidelity comparisons dealt with are discrete endwall cooling holes vs. equivalent slot and explicit cavity resolution vs. patch surface techniques. In addition, comparisons of traverses predicted using the k-Epsilon realizable turbulence model and SST k-Omega model are presented and debated. The influence of the geometry fidelity and turbulence model on the evolution of radial distribution through the stage is presented along with supporting flow field interpretations. It is concluded that the slot representation of platform cooling flow is satisfactory to replicate the overall traverse at the exit of the High Pressure Nozzle during early stages of design. The near wall temperature gradient would be lower and in the present case the Horse Shoe Vortex (HSV) at the endwalls are not observed with discrete cooling flow modelling which indicates probable aerodynamic impact. The choice of turbulence modelling could have significant impact on the traverse prediction in comparison to the geometry approximations.

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