Numerical Simulation of Flow in Turbine Blade Film Cooling PDF Download

Author: Saravanakanthan Rajendran
Publisher:
ISBN:
Category : Aerothermodynamics
Languages : en
Pages :

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Author: Douglas Stenger
Publisher:
ISBN:
Category :
Languages : en
Pages : 98

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The present study is a three-dimensional numerical investigation of the effectiveness of film cooling for a turbine blade leading-edge model with both a single and a three-hole cooling configuration. The model used has the same dimensions as those in the experimental investigation of Ou and Rivir (2006). It consists of a half cylinder with a flat after-body, and well represents the leading edge of a turbine blade. The single coolant hole is situated approximately at the spanwise center of the cylindrical model, and makes an angle of 21.5 degrees to the leading edge and 20 degrees to the spanwise direction. For the three-hole configuration, the center hole is positioned the same as the single hole in the single-hole configuration, with the adjacent holes located at a spanwise distance of 37.4 mm on either side of the center hole. Multi-block grids were generated using GridGen, and the flows were simulated using the flow solver Fluent. A highly clustered structured C-grid was developed around the leading edge of the model. The outer unstructured-grid domain represents the wind tunnel as used in the experimental study of Ou and Rivir (2006), and the leading-edge model is located at the center of the domain. Simulations were carried out for blowing ratios, M, ranging from 0.75 to 2.0. Turbulence was represented using the k-? shear-stress transport (SST) model, and the flow was assumed to have a free-stream turbulence intensity of 0.75%. Two types of boundary conditions were used to represent the blade wall: an adiabatic surface, and a conductive surface. The adiabatic-wall results over-predicted the film-cooling effectiveness in the far downstream region for low blowing ratios. Also, in the vicinity of the cooling hole, an increase in blowing ratio resulted in higher film cooling effectiveness than observed in the experiments. It should be noted that the steady RANS-based turbulence model used under-predicts the interaction between the coolant and mainstream flow near the cooling-pipe exit. The conductive-wall results show a much closer agreement with experimental data for film effectiveness as compared to the adiabatic-wall predictions. Simulations were also performed with higher values of turbulence intensity at the cooling-hole inlet, and these predicted the coolant-mainstream interaction and the film-cooling effectiveness more accurately. Finally, a novel concept of pulsing the coolant flow was implemented so as to achieve film-cooling effectiveness equivalent to that with constant cooling, but with reduced overall coolant air, thereby enhancing turbine efficiency. Pulsed cooling with pulsing frequency PF = 5 and 10Hz, and duty cycle DC = 50%, shows the greatest cooling effects. The three-hole cooling results indicate that the 49 mm spanwise distance used for computing the spanwise-averaged values for film-cooling effectiveness accounts for all of the film-coolant spreading provided by the single hole. Also, the neighboring cooling holes contribute little film cooling to the 49 mm spanwise distance. The most significant new finding in this work is that the inclusion of wall conductance is the main factor responsible for reproducing the experimental data.

Author: Laurene D. Dobrowolski
Publisher:
ISBN:
Category :
Languages : en
Pages : 436

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Computations and experiments were run to study heat transfer and overall effectiveness for a simulated turbine blade leading edge. Computational predictions were run for a film cooled leading edge model using a conjugate numerical method to predict the normalized "metal" temperatures for the model. This computational study was done in conjunction with a parallel effort to experimentally determine normalized metal temperatures, i.e. overall effectiveness, using a specially designed high conductivity model. Predictions of overall effectiveness were higher than experimentally measured values in the stagnation region, but lower along the downstream section of the leading edge. Reasons for the differences between computational predictions and experimental measurements were examined. Also of interest was the validity of Taw as the driving temperature for heat transfer into the blade, and this was examined via computations. Overall, this assumption gave reasonable results except near the stagnation line. Experiments were also conducted on a leading edge with no film cooling to gain a better understanding of the additional cooling provided by film cooling. Heat flux was also measured and external and internal heat transfer coefficients were determined. The results showed roughly constant overall effectiveness on the external surface.

Author: Jason B. Blitz
Publisher:
ISBN:
Category : Gas-turbines
Languages : en
Pages : 384

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Author: Harbi Ahmed Daud
Publisher:
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Category :
Languages : en
Pages :

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This thesis examines the cooling performance and the flow on a gas turbine blade. Numerical and experimental methods are described and implemented to assess the influence of film cooling effectiveness. A modem gas turbine blade geometry has been used. The blade is considered as a solid body with the blade cross section from hub to shroud varying with a degree of skewness. Computational Fluid Dynamics (CFD) is employed to assess blade film cooling effectiveness via simulation of the effect of varying blowing ratios (BR=l, 1.5 and 2), varying coolant fluid temperature (Tc=153 K and Tc=287.5 K), various angles of injection (35°,45° and 60°), increasing the number of cooling holes (32 and 42) and increasing the cooling holes diameter (D= 0.5 mm and 1mm). A full three-dimensional finite-volume method has been utilized in this study via the FLUENT 6.3 code with a k-s (RN G) turbulence model. Results of the CFD models were carefully validated by studying aerodynamic flow and heat transfer in turbine blade film cooling performance. A two-dimensional channel and NACA 0012 airfoil were selected to investigate turbulence effects. The solution accuracy is assessed by carrying out a sensitivity analysis of mesh type and quality effects with enhancement wall treatment and standard wall function effects also addressed for turbulent boundary layers. In this study, four different turbulence models were utilized (S-A, k-c:, (RNG), and (SST) k-w). The computations were compared with available Direct Numerical Simulation (DNS) and experimental data. Good correlation was observed when using the RNG turbulence model in comparison with other turbulence models. Film cooling effectiveness and heat transfer along a flat plate has been analyzed for four different plate materials, namely steel, carbon steel, copper and aluminum, with 30° angle of injection. The cooling holes arrangement was simulated for a hole diameter of D= 1 mm and different sections of the blade showing cooling effectiveness and heat transfer characteristic variation with increasing (BR = 0.5, 1). Furthermore a symmetrical single hole at 35° angle of injection was studied both the solid and shell plate cases. Cooling effectiveness numerical results were compared with available experimental data and the effect of material thermal properties for the solid plate on cooling performance evaluated. Numerical modeling has clearly identified that there is no benefit in reducing the number of holes as this decreases film cooling effectiveness. The experimental investigation showed the effect of increasing volumetric flow rate VO=1000, 800 and 600 cm3/min, as a term of the blowing ratio (BR) and angle of injection (35°,45° and 60°) for a modem gas turbine blade specimen using Thermal Paint Technology (TPT) and a Thermal Wind Tunnel (TWT). Both methods confirmed that the blade specimen with angle of injection of 45°, blowing ratio of BR=2 (which corresponds to 1000cm3/min), cooling holes diameter D=lmm and 42 holes developed a better film cooling effectiveness compared with the 35° and 60° cases. In addition TPT is a sufficient and relatively easy method for evaluating temperature distributions in experimental studies.

Author: Dieter Bohn
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Presented at the International Gas Turbine and Aeroengine Congress &Exhibition Birmingham, UK - June 10-13, 1996.

Author: Abdul Hafid M. Elfaghi
Publisher:
ISBN:
Category : Turbines
Languages : en
Pages : 216

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The development of high performance gas turbines requires high turbine inlet temperatures that can lead to severe thermal stresses in the turbine blades, particularly in the first stages of the turbine. Therefore, the major objective of gas- turbine designers is to determine the thermal and aero-dynamical characteristics of the turbulent flow in the turbine cascade. This work is a numerical simulation of fluid flow and heat transfer in the turbine blade using different two-equation turbulence models. The turbulence models used here were based on the eddy viscosity concept, which determined the turbulent viscosity through time-averaged Navier-Stokes differential equations. The most widely accepted turbulence models are the two-equation models, which involves the solution of two transport equations for the turbulent kinetic energy, k, and its rate of dissipation, & or In the present simulation, four two-equation turbulence models were used, the standard k-& model, the modified Chen-Kim k-& model, RNG model and Wilcox standard k - OJ turbulence model. A comparison between the turbulence models and their predictions of the heat flux on the blade were carried out. The results were also compared with the available experimental results obtained from a research carried out by Arts et at. (1990) at the von Karman Institute of Fluid Dynamics (VKI). The simulation was performed using the general-purpose computational fluid dynamics code, PHOENICS, which solved the governing fluid flow and heat transfer equations. An H-type, body-fitted-co-ordinate (BFC) grid was used and upstream and downstream periodic conditions were specified. The grid system used was, sufficiently fine and the results were grid independent. All models demonstrated good heat transfer predictions for the pressure side except close to the leading edge. On the suction side, standard model over-predicted the heat transfer, whereas Chen-Kim, RNG and k - OJ models captured the overall behaviour quite well. Unlike k - OJ model, all k - & models generated very high turbulence levels in the stagnation point regions, which gave rise to the heat transfer rates close to the leading edge.

Author: Ali A. Ameri
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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Author: Chaitanya D Ghodke
Publisher: SAE International
ISBN: 0768095026
Category : Technology & Engineering
Languages : en
Pages : 238

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Gas turbines play an extremely important role in fulfilling a variety of power needs and are mainly used for power generation and propulsion applications. The performance and efficiency of gas turbine engines are to a large extent dependent on turbine rotor inlet temperatures: typically, the hotter the better. In gas turbines, the combustion temperature and the fuel efficiency are limited by the heat transfer properties of the turbine blades. However, in pushing the limits of hot gas temperatures while preventing the melting of blade components in high-pressure turbines, the use of effective cooling technologies is critical. Increasing the turbine inlet temperature also increases heat transferred to the turbine blade, and it is possible that the operating temperature could reach far above permissible metal temperature. In such cases, insufficient cooling of turbine blades results in excessive thermal stress on the blades causing premature blade failure. This may bring hazards to the engine's safe operation. Gas Turbine Blade Cooling, edited by Dr. Chaitanya D. Ghodke, offers 10 handpicked SAE International's technical papers, which identify key aspects of turbine blade cooling and help readers understand how this process can improve the performance of turbine hardware.

Author: A. Heselhaus
Publisher:
ISBN:
Category :
Languages : en
Pages :

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