Numerical simulation of film cooling for gas turbine blades PDF Download

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

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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: Ernst Rudolf Georg Eckert
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 44

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Summary: Transpiration and film cooling promise to be effective methods of cooling gas-turbine blades; consequently, analytical and experimental investigations are being conducted to obtain a better understanding of these processes. This report serves as an introduction to these cooling methods, explains the physical processes, and surveys the information available for predicting blade temperatures and heat-transfer rates. In addition, the difficulties encountered in obtaining a uniform blade temperature are discussed, and the possibilities of correcting these difficulties are indicated. Air is the only coolant considered in the application of these cooling methods.

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: Bengt Sundén
Publisher: Witpress
ISBN:
Category : Medical
Languages : en
Pages : 544

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Book Description
This title presents and reflects current active research on various heat transfer topics and related phenomena in gas turbine systems. It begins with a general introduction to gas turbine heat transfer, before moving on to specific areas.

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

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Author: Guoguang Su
Publisher:
ISBN:
Category :
Languages : en
Pages :

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A computational study of three-dimensional turbulent flow and heat transfer was performed in four types of rotating channels. The first type is a rotating rectangular channel with V-shaped ribs. The channel aspect ratio (AR) is 4:1, the rib height-to-hydraulic diameter ratio (e/Dh) is 0.078 and the rib pitch-to-height ratio (P/e) is 10. The rotation number and inlet coolant-to-wall density ratio were varied from 0.0 to 0.28 and from 0.122 to 0.40, respectively, while the Reynolds number was varied from 10,000 to 500,000. Three channel orientations (90degrees, -135 degrees, and 135 degrees from the rotation direction) were also investigated. The second type is a rotating rectangular channel with staggered arrays of pinfins. The channel aspect ratio (AR) is 4:1, the pin length-to-diameter ratio is 2.0, and the pin spacing-to-diameter ratio is 2.0 in both the stream-wise and span-wise directions. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150 degrees with respect to the plane of rotation. In the rotating two-pass rectangular channel with 45-degree rib turbulators, three channels with different aspect ratios (AR=1:1; AR=1:2; AR=1:4) were investigated. Detailed predictions of mean velocity, mean temperature, and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rib height is fixed as constant and the rib-pitch-to-height ratio (P/e) is 10, but the rib height-to-hydraulic diameter ratios (e/Dh) are 0.125, 0.094, and 0.078, for AR=1:1, AR=1:2, and AR=1:4 channels, respectively. The channel orientations are set as 90 degrees, the rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. The last type is the rotating two-pass smooth channel with three aspect ratios (AR=1:1; AR=1:2; AR=1:4). Detailed predictions of mean velocity, mean temperature and Nusselt number for two Reynolds numbers (Re=10,000 and Re=100,000) were carried out. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.13 to 0.40, respectively. A multi-block Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure.

Author: R.S. Amano
Publisher: WIT Press
ISBN: 1845649060
Category : Science
Languages : en
Pages : 253

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Book Description
Due to the requirement for enhanced cooling technologies on modern gas turbine engines, advanced research and development has had to take place in field of thermal engineering. Among the gas turbine cooling technologies, impingement jet cooling is one of the most effective in terms of cooling effectiveness, manufacturability and cost. The chapters contained in this book describe research on state-of-the-art and advanced cooling technologies that have been developed, or that are being researched, with a variety of approaches from theoretical, experimental, and CFD studies. The authors of the chapters have been selected from some of the most active researchers and scientists on the subject. This is the first to book published on the topics of gas turbines and heat transfer to focus on impingement cooling alone.