Browsing by Author "Abdala, Antar M. M."

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CFD Simulations of Film Cooling Effectiveness and Heat Transfer for Annular Film Hole
(SPRINGER HEIDELBERG, 2016) Abdala, Antar M. M.; Elwekeel, Fifi N. M.
The increasing turbine entry temperature has placed demands for improvements in engine cooling, and the work described in this paper is the development of a new film cooling configuration to meet this demand. In this study, numerical simulations were performed to predict the improvement in film cooling performance with novel film hole called an annular film hole. The film cooling performance parameters such as heat transfer coefficient (h), film cooling effectiveness ( and the net heat flux reduction (NHFR) over flat plate were investigated and compared with other configurations. Velocity profiles, pressure coefficient and turbulence kinetic energy contours were discussed. Four mass flow rates of secondary flow fluid were used to investigate the effects of film coolant velocity on the film cooling performance behavior. Results indicate that an annular film hole gives high film effectiveness, low heat transfer coefficient and higher NHFR compared to rectangular and circular film holes. The average values of laterally averaged film cooling effectiveness of the annular film hole increased to 106 and 328.5% compared with the rectangular and circular film holes at moderate flow rate, respectively. This difference is attributable to decreasing the jet vertical velocity component in a case of the annular hole. Also the low and high heat transfer coefficient regions were described for annular hole in detail.
Effect of mist cooling technique on exergy and energy analysis of steam injected gas turbine cycle
(PERGAMON-ELSEVIER SCIENCE LTD, 04/05/2016) Abdala, Antar M. M.; Elwekeel, Fifi N. M
The common cogeneration application is steam injected gas turbine. By using cogeneration, it can be obtained with the greatest benefit from fuel energy. In steam injected gas turbine the heat of exhaust gases is used to produce the steam, and this steam injects to combustion chamber. In the present work, the generated steam not only will be directed to the combustion chamber but also will be used to cool the blade turbine by using a closed loop. In this study, the effect of addition mist to steam as coolant fluid was investigated. The energy and exergy analyses for steam injected gas turbine cycle with a closed loop cooling technique by using steam and steam/mist were investigated. The investigation was made at varied values of steam coolant temperature, mist fraction, mist temperature, pressure ratio, turbine inlet temperature and blade temperature. These parameters affected network, plant efficiency, energy ratio, fuel conversion ratio and exergy efficiency. The results show that the efficiency can reach 47.2% at low coolant temperature with a mist fraction of 2%. The coolant heat gain is enhanced at lower mist temperature, so the blade surface temperature can be improved with mist addition to steam. At a mist fraction of 2% exergy efficiency is decreased by 0.03% than that for exergy efficiency of steam only. (C) 2015 Elsevier Ltd. All rights reserved.
EFFECTS OF FILM HOLE EXIT RADIUSING ON FILM COOLING PERFORMANCE
(AMER SOC MECHANICAL ENGINEERS, 2016) Abdala, Antar M. M.; Elwekeel, Fifi N. M.; Zheng, Qun
In the present study, theoretical investigation of film cooling effectiveness and heat transfer behavior for radiusing of film hole exit was evaluated. Seven rounding radii of R=0.0D, 0.06D, 0.08D, 0.1D, 0.3D, 0.5D and 0.8D were investigated. The film cooling effectiveness, the heat transfer coefficient, net heat flux ratio and discharge coefficient were investigated. Four mass flow rates in the range of 0.00044: 0.0018[kg/s] were used to investigate the effects of coolant velocity on the film cooling performance. Results show that using the film hole exit radiusing helps in improvement the film cooling effectiveness. The radius of R=0.5D shows higher film cooling effectiveness among the other radii. The spatially average laterally film cooling effectiveness and net heat flux ratio of R=0.5D outperforms the case of R=0.0D at all mass flow rates except at higher rates the values are lower. Discharge coefficient of R=0.5D shows enhancement than R=0.0D with the pressure ratios. Interpretation of the low and high heat transfer coefficient regions for radii of R=0.5D and R=0.0D depending on the flow structures was explained in detail.
Effects of mist and jet cross-section on heat transfer for a confined air jet impinging on a flat plate
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2016) Elwekeel, Fifi N. M.; Abdala, Antar M. M.
Convective heat transfer to an impinging air jet is known to yield high local and area-average Nusselt numbers. We simulate this heat transfer over a wide range of study parameters, including Reynolds number and mist mass fraction, and three jet shapes: circular, half circuit, and quarter circuit. Simulations show that when compared with air only, mist provides higher heat-transfer enhancements for the first two shapes but is insignificant for the third. The area-average Nusselt number is higher by similar to 100% for the half-circuit jet than for the circular jet for both single-phase air and mist. With 0.5% mist, the area average Nusselt number of the circular jet is enhanced by 41% at Reynolds number 10000. (C) 2016 Elsevier Masson SAS. All rights reserved.
Energy Analysis of Recuperated Gas Turbine Cycles with Mist Blade Cooling
(AMER SOC MECHANICAL ENGINEERS, 2016) Elwekeel, Fifi N. M.; Abdala, Antar M. M.; Zheng, Qun
The present work investigates the effects of mist injection in turbine blade cooling line and the investigation parameters on the performance parameters. The investigation parameters are ambient temperature, ambient relative humidity, and compressor pressure ratio and turbine inlet temperature. The performance parameters are coolant ratio, plant efficiency, heat regeneration rate and specific fuel consumption. This study is conducted on simple recuperated cycle (SRC), recuperated cycle with closed loop cooling (RCCLC) and recuperated cycle with film cooling (RCFC). The results show that by mist, the compressor pressure ratio can be extended to 11 to achieve optimum efficiency. The plant efficiency of RCCLC increases by 2.5% than that for SRC.
Upstream and Downstream Step Curvature Effects on Film Cooling Effectiveness and Flow Structures
(SPRINGER, 2015) Elwekeel, Fifi N. M.; Abdala, Antar M. M.; Huang, Diangui
In this study, computational simulations were made using ANSYS CFX to predict the influence of upstream and downstream step curvature radii on the film cooling effectiveness. Five upstream steps and four downstream steps with different curvature radii were studied. The curvature radii of these steps of R = 1.64D, 2D, 3D, 4D, and 5D were used. The film cooling effectiveness (eta) of these steps was investigated and compared with experiment. The near-field flow phenomena such as the pressure coefficient and the jet trajectories were discussed. Results indicate that the step position in the upstream of a film hole has a higher effect on the film cooling effectiveness compared with the downstream position. The film cooling effectiveness increases in the case of the upstream curved steps at lower radii due to entrapping more coolant in the region upstream of a hole. The results show that the pressure difference has an important effect to draw the coolant in the upstream region of a film hole compared with the case without step.