Mohamed Qenawy - Academia.edu (original) (raw)
Papers by Mohamed Qenawy
Journal of Thermal Science
International Journal of Thermal Sciences, 2022
Journal of Turbomachinery, 2020
An experimental study was conducted to investigate the influence of mainstream oscillations on sp... more An experimental study was conducted to investigate the influence of mainstream oscillations on spatio-temporal variation of leading-edge film cooling effectiveness. The investigation utilized fast-response pressure-sensitive paint (Fast-PSP) technique at high frame rate. During the experiment, coolant (i.e., CO2, DR = 1.53) was discharged into three rows of cylindrical holes. Various blowing ratios (i.e., M = 0.50, 0.75, 1.00, and 1.50) were tested under the steady (i.e., f = 0 Hz) and oscillating (i.e., f = 7 Hz and 25 Hz) conditions. The measured instantaneous effectiveness was analyzed in terms of time-averaged and phase-averaged results. The results revealed that the mainstream oscillation, consisting of simultaneous pressure and velocity oscillation, significantly influences the behavior of the film cooling effectiveness. The time-averaged effectiveness significantly decreased at high oscillating frequency (i.e., 13.0–19.8% reduction at M = 0.50, f = 25 Hz compared with f = 0 H...
International Journal of Heat and Mass Transfer, 2020
In this study, the film cooling effectiveness of a turbine vane endwall was quantified using the ... more In this study, the film cooling effectiveness of a turbine vane endwall was quantified using the pressuresensitive paint (PSP) technique. With circular holes serving as the baseline, a barchan-dune shaped ramp (BDSR) was compared side by side to examine its endwall cooling performance in a single-passage wind tunnel at Ma = 0.84. Carbon dioxide was used as coolant, which was discharged into the endwall model. The slot was fed by a constant blowing ratio of M = 0.3, while the coolant holes were set to be M = 0.5, 1.0, 1.5, and 2.0. The results showed an asymmetrical coolant distribution for both circular holes and BDSR, with the highest cooling effectiveness near the suction side (SS) and the lowest near the pressure side (PS). This behavior was caused by the passage flow structures, where the coolant aligned with the vortex lines and flowed toward the SS. Compared with the baseline, the BDSR demonstrated significantly increased cooling performance in the near-SS regions. The presence of a dune ramp is particularly beneficial for endwall cooling at high blowing ratios. As revealed by numerical simulations, the induced anticounter-rotating vortex pair (CRVP) in the BDSR countervails the detrimental effect of CRVP and greatly improves the endwall cooling performance.
Journal of Engineering for Gas Turbines and Power, 2020
Wind-tunnel testing of turbines cascade is an important technique for quantifying the realistic c... more Wind-tunnel testing of turbines cascade is an important technique for quantifying the realistic conditions of turbine-vane film cooling. However, the complex and expensive facilities needed for the multipassage design of such wind tunnels have prompted the introduction of the single-passage design strategy. In this contribution, detailed procedures for building a novel single-passage transonic wind-tunnel using additive manufacturing are presented. In addition, the detailed flow structure caused by the passage was investigated. The proposed design was evaluated step-by-step using an integrated model that successively comprised two-dimensional (2D) periodic passage simulation, 2D single-passage simulation, three-dimensional (3D) single-passage simulation, construction, and testing. The proposed design was found to achieve flow periodicity at transonic flow conditions with relatively low-flow consumption. The results were validated by comparison to the available literature data. In ad...
Journal of Turbomachinery, 2020
The flow structures and unsteady behaviors of a flat plate film cooling flow behind a single row ... more The flow structures and unsteady behaviors of a flat plate film cooling flow behind a single row of circular holes fed by internal crossflow were extensively investigated. The investigation was achieved experimentally using fast-response pressure-sensitive paint (PSP) at a high frame rate and numerically using large-eddy simulation (LES). During the experiment, the coolant flow was discharged from discrete holes (i.e., a row of circular holes with 3D spacing, 6.5D entry length, and 35 deg incline angle) via a crossflow channel. Two blowing ratios (M = 0.4 and 0.8) were tested at a density ratio of DR = 0.97. The measured unsteadiness caused by the predicted flow structure over the coolant surface was identified by spatial correlation. The unsteady signatures were decomposed and demonstrated by proper orthogonal decomposition (POD). The results reveal that the flow structure plays the main role in cooling performance and its instability. The internal flow produced a vortex tube struc...
International Journal of Heat and Mass Transfer, 2019
The effect of mainstream oscillations on spatio-temporal variation of adiabatic effectiveness was... more The effect of mainstream oscillations on spatio-temporal variation of adiabatic effectiveness was quantified extensively by the fast-response pressure-sensitive paint (fast-PSP) technique. During the experiment, nitrogen (N 2) was used as the coolant and was discharged from a 35°-inclined round hole. While the steady state (i.e., f = 0 Hz) was selected as the baseline, the oscillating cases were assessed in great detail to explore the frequency effect (i.e., f = 5, 10, and 20 Hz with a fixed amplitude) on film cooling performance. Measured instantaneous effectiveness results (i.e., g) were analyzed in terms of the ensembleaveraged (i.e., g) and phase-averaged results (i.e., e g), where the latter one was further analyzed through triple decomposition. The ensemble-averaged results showed a strong effect of mainstream oscillations on adiabatic effectiveness: compared to the steady state, a reduction of 30-35% was observed in effectiveness for the M = 0.4 at f = 20 Hz cases. As for the phase-averaged results, a relatively weak dependence was observed at 5 Hz with respect to the phase angles. However, as the frequency increased to 20 Hz, obtained effectiveness exhibited a strong correlation with the velocity phase, where its contour was found to become longer and shorter during periodic cycles. In general, mainstream oscillations have a significant impact on the film cooling behavior. They not only degrade the cooling effectiveness, but also increase the unsteadiness in film cooling.
Proceedings of Global Power & Propulsion Society, 2019
The film cooling vortical structure behind a cylindrical hole fed by internal crossflow was inves... more The film cooling vortical structure behind a cylindrical hole fed by internal crossflow was investigated by large eddy simulation (LES). The simulation was performed on a single simple cylindrical hole (i.e., a spacing of 3D, an entry length of 6.5D, and an injection angle of 35 o). Two blowing ratios (M = 0.40 and 0.80) were simulated with a density ratio of 0.97. The results were validated in comparison with the measured data. The vortical structures were identified by the Q-criterion coherent isosurface and their unsteady signatures were identified by the standard deviation (SD). The vortical structures were demonstrated to play the main role in cooling performance and its instability. The internal flow was significantly produced a vortex tube structure, which responsible for the shear vortex (Kelvin-Helmholtz instabilities) between the coolant and the mainstream at the hole exit. As a result, it forced the legs of the counter-rotating vortex pair (CRVP) to widely spread and enhance the coolant effectiveness downstream.
The effect of mainstream oscillations on double-row holes film cooling effectiveness was experime... more The effect of mainstream oscillations on double-row holes film cooling effectiveness was experimentally investigated. During the experiment, carbon dioxide (CO2) was used as the coolant and was discharged from 35°inclined double-row holes with in-line and staggered arrangement. As a baseline study, a single row injection was pre-considered and the double-row film cooling cases with periodic freestream were assessed in detail to explore the frequency effect (i.e. set to 5 Hz and 25 Hz with fixed amplitude) on adiabatic effectiveness. The adiabatic effectiveness was measured by fast-response pressuresensitive paint (fast-PSP) and was further analysed in term of the time-averaged (̅) and phase-averaged (̃) results. The time-averaged results showed that double-row could restrain the negative effects of mainstream oscillations and enhance the positive effects, compared with the baseline. The phaseaveraged results showed that the double-row could have more stable coolant coverage than single row. Moreover, the staggered arrangement had comprehensive better protection than the in-line at high blowing ratio, but at lower blowing ratio reversed.
Journal of Thermal Science
International Journal of Thermal Sciences, 2022
Journal of Turbomachinery, 2020
An experimental study was conducted to investigate the influence of mainstream oscillations on sp... more An experimental study was conducted to investigate the influence of mainstream oscillations on spatio-temporal variation of leading-edge film cooling effectiveness. The investigation utilized fast-response pressure-sensitive paint (Fast-PSP) technique at high frame rate. During the experiment, coolant (i.e., CO2, DR = 1.53) was discharged into three rows of cylindrical holes. Various blowing ratios (i.e., M = 0.50, 0.75, 1.00, and 1.50) were tested under the steady (i.e., f = 0 Hz) and oscillating (i.e., f = 7 Hz and 25 Hz) conditions. The measured instantaneous effectiveness was analyzed in terms of time-averaged and phase-averaged results. The results revealed that the mainstream oscillation, consisting of simultaneous pressure and velocity oscillation, significantly influences the behavior of the film cooling effectiveness. The time-averaged effectiveness significantly decreased at high oscillating frequency (i.e., 13.0–19.8% reduction at M = 0.50, f = 25 Hz compared with f = 0 H...
International Journal of Heat and Mass Transfer, 2020
In this study, the film cooling effectiveness of a turbine vane endwall was quantified using the ... more In this study, the film cooling effectiveness of a turbine vane endwall was quantified using the pressuresensitive paint (PSP) technique. With circular holes serving as the baseline, a barchan-dune shaped ramp (BDSR) was compared side by side to examine its endwall cooling performance in a single-passage wind tunnel at Ma = 0.84. Carbon dioxide was used as coolant, which was discharged into the endwall model. The slot was fed by a constant blowing ratio of M = 0.3, while the coolant holes were set to be M = 0.5, 1.0, 1.5, and 2.0. The results showed an asymmetrical coolant distribution for both circular holes and BDSR, with the highest cooling effectiveness near the suction side (SS) and the lowest near the pressure side (PS). This behavior was caused by the passage flow structures, where the coolant aligned with the vortex lines and flowed toward the SS. Compared with the baseline, the BDSR demonstrated significantly increased cooling performance in the near-SS regions. The presence of a dune ramp is particularly beneficial for endwall cooling at high blowing ratios. As revealed by numerical simulations, the induced anticounter-rotating vortex pair (CRVP) in the BDSR countervails the detrimental effect of CRVP and greatly improves the endwall cooling performance.
Journal of Engineering for Gas Turbines and Power, 2020
Wind-tunnel testing of turbines cascade is an important technique for quantifying the realistic c... more Wind-tunnel testing of turbines cascade is an important technique for quantifying the realistic conditions of turbine-vane film cooling. However, the complex and expensive facilities needed for the multipassage design of such wind tunnels have prompted the introduction of the single-passage design strategy. In this contribution, detailed procedures for building a novel single-passage transonic wind-tunnel using additive manufacturing are presented. In addition, the detailed flow structure caused by the passage was investigated. The proposed design was evaluated step-by-step using an integrated model that successively comprised two-dimensional (2D) periodic passage simulation, 2D single-passage simulation, three-dimensional (3D) single-passage simulation, construction, and testing. The proposed design was found to achieve flow periodicity at transonic flow conditions with relatively low-flow consumption. The results were validated by comparison to the available literature data. In ad...
Journal of Turbomachinery, 2020
The flow structures and unsteady behaviors of a flat plate film cooling flow behind a single row ... more The flow structures and unsteady behaviors of a flat plate film cooling flow behind a single row of circular holes fed by internal crossflow were extensively investigated. The investigation was achieved experimentally using fast-response pressure-sensitive paint (PSP) at a high frame rate and numerically using large-eddy simulation (LES). During the experiment, the coolant flow was discharged from discrete holes (i.e., a row of circular holes with 3D spacing, 6.5D entry length, and 35 deg incline angle) via a crossflow channel. Two blowing ratios (M = 0.4 and 0.8) were tested at a density ratio of DR = 0.97. The measured unsteadiness caused by the predicted flow structure over the coolant surface was identified by spatial correlation. The unsteady signatures were decomposed and demonstrated by proper orthogonal decomposition (POD). The results reveal that the flow structure plays the main role in cooling performance and its instability. The internal flow produced a vortex tube struc...
International Journal of Heat and Mass Transfer, 2019
The effect of mainstream oscillations on spatio-temporal variation of adiabatic effectiveness was... more The effect of mainstream oscillations on spatio-temporal variation of adiabatic effectiveness was quantified extensively by the fast-response pressure-sensitive paint (fast-PSP) technique. During the experiment, nitrogen (N 2) was used as the coolant and was discharged from a 35°-inclined round hole. While the steady state (i.e., f = 0 Hz) was selected as the baseline, the oscillating cases were assessed in great detail to explore the frequency effect (i.e., f = 5, 10, and 20 Hz with a fixed amplitude) on film cooling performance. Measured instantaneous effectiveness results (i.e., g) were analyzed in terms of the ensembleaveraged (i.e., g) and phase-averaged results (i.e., e g), where the latter one was further analyzed through triple decomposition. The ensemble-averaged results showed a strong effect of mainstream oscillations on adiabatic effectiveness: compared to the steady state, a reduction of 30-35% was observed in effectiveness for the M = 0.4 at f = 20 Hz cases. As for the phase-averaged results, a relatively weak dependence was observed at 5 Hz with respect to the phase angles. However, as the frequency increased to 20 Hz, obtained effectiveness exhibited a strong correlation with the velocity phase, where its contour was found to become longer and shorter during periodic cycles. In general, mainstream oscillations have a significant impact on the film cooling behavior. They not only degrade the cooling effectiveness, but also increase the unsteadiness in film cooling.
Proceedings of Global Power & Propulsion Society, 2019
The film cooling vortical structure behind a cylindrical hole fed by internal crossflow was inves... more The film cooling vortical structure behind a cylindrical hole fed by internal crossflow was investigated by large eddy simulation (LES). The simulation was performed on a single simple cylindrical hole (i.e., a spacing of 3D, an entry length of 6.5D, and an injection angle of 35 o). Two blowing ratios (M = 0.40 and 0.80) were simulated with a density ratio of 0.97. The results were validated in comparison with the measured data. The vortical structures were identified by the Q-criterion coherent isosurface and their unsteady signatures were identified by the standard deviation (SD). The vortical structures were demonstrated to play the main role in cooling performance and its instability. The internal flow was significantly produced a vortex tube structure, which responsible for the shear vortex (Kelvin-Helmholtz instabilities) between the coolant and the mainstream at the hole exit. As a result, it forced the legs of the counter-rotating vortex pair (CRVP) to widely spread and enhance the coolant effectiveness downstream.
The effect of mainstream oscillations on double-row holes film cooling effectiveness was experime... more The effect of mainstream oscillations on double-row holes film cooling effectiveness was experimentally investigated. During the experiment, carbon dioxide (CO2) was used as the coolant and was discharged from 35°inclined double-row holes with in-line and staggered arrangement. As a baseline study, a single row injection was pre-considered and the double-row film cooling cases with periodic freestream were assessed in detail to explore the frequency effect (i.e. set to 5 Hz and 25 Hz with fixed amplitude) on adiabatic effectiveness. The adiabatic effectiveness was measured by fast-response pressuresensitive paint (fast-PSP) and was further analysed in term of the time-averaged (̅) and phase-averaged (̃) results. The time-averaged results showed that double-row could restrain the negative effects of mainstream oscillations and enhance the positive effects, compared with the baseline. The phaseaveraged results showed that the double-row could have more stable coolant coverage than single row. Moreover, the staggered arrangement had comprehensive better protection than the in-line at high blowing ratio, but at lower blowing ratio reversed.