Role of mainstream flow velocity in film cooling in a duct

Kuo, S.P.; Zhang, Neng-Li; Yang, Wen‐Jei

doi:10.2514/3.800

Cited by 9 publications

(4 citation statements)

References 8 publications

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“…Martelli et al [22] found that the parameters like axial distance from the injection point, the slot height and blowing ratio affected film cooling performance. O'Connor et al [23] and Kuo et al [24] investigated the role of main stream flow velocity. Kuo et al [24] reported that film cooling is effective in subsonic flow compared to supersonic flow.…”

Section: Literature Reviewmentioning

confidence: 99%

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Effect of injector configuration in rocket nozzle film cooling

2015

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List of symbols A injCross-sectional area of the nozzle at the coolant injection point (m 2 ) A throat Cross-sectional area of the throat of the nozzle (m 2 ) AR Area ratio (dimensionless) BR Blowing ratio (dimensionless) c p Specific heat (J kg −1 K −1 ) Hz Unit of frequency (cycles per second) hp Horse power (1 hp = 746 W) J Diffusion flux (kg m −2 s −1 ) p Static pressure (N m −2 ) r Radial coordinate (mm) Re Reynolds number (dimensionless) Sc Schmidt number (dimensionless) TuTurbulence intensity (%)Mass fraction of the component (dimensionless) Greek lettersDegree of film cooling effectiveness (dimensionless) ΔT Temperature difference between surface and ambient (K) Subscripts c CoolantAbstract Experimental and numerical investigations are carried out to analyze the effect of coolant injector configuration on overall film cooling performance in a divergent section of a rocket nozzle. Two different injector orientations are investigated: (1) shaped slots with a divergence angle of 15° (semi-divergent injector) (2) fully divergent slot (fully divergent injector). A 2-dimensional, axis-symmetric, multispecies computational model using finite volume formulation has been developed and validated against the experimental data. The experiments provided a consistent set of measurements for cooling effectiveness for different blowing ratios ranging from 3.7 to 6. Results show that the semi divergent configuration leads to higher effectiveness compared to fully divergent slot at all blowing ratios. The spatially averaged effectiveness results show that the difference between the two configurations is significant at higher blowing ratios. The increase in effectiveness was around 2 % at BR = 3.7 whereas it was around 12 % in the case of BR = 6. Numerical results show the presence of secondary flow recirculation zones near the jet exit for both the injectors. An additional recirculation zone present in the case of fully divergent injector caused an increase in mixing of the coolant and mainstream, and a reduction in film cooling performance.

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Section: Literature Reviewmentioning

confidence: 99%

“…O'Connor et al [23] and Kuo et al [24] investigated the role of main stream flow velocity. Kuo et al [24] reported that film cooling is effective in subsonic flow compared to supersonic flow. However experiments by Aupoix et al [25] revealed that film cooling is much more efficient in supersonic flows than subsonic flows.…”

Section: Literature Reviewmentioning

confidence: 99%

Effect of injector configuration in rocket nozzle film cooling

2015

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“…The impact of the interaction between the wall jet and the mainstream on cooling performance under different conditions has been analyzed in various studies ([ 20 , 21 , 22 , 23 ]). All these studies pertain to flat/cylindrical surface configurations.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Film Cooling Effectiveness in a Supersonic Nozzle

Somasekharan

Srikrishnan

Kumar

et al. 2023

Entropy

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Film cooling as applied to rocket nozzles is analyzed numerically with emphasis on the assessment of the effect of the mixing of coolant with the hot stream. Cooling performance, as characterized by cooling effectiveness, is studied for three different coolants in the three-dimensional, turbulent flow field of a supersonic convergent-divergent nozzle operating with a hot stream temperature of 2500 K over a range of blowing ratios. The coolant stream is injected tangentially into the mainstream using a diffuser-type injector. Parameters influencing the effectiveness, such as coolant injector configuration and mixing layer, are analyzed. Thermal and species mixing between the coolant and the mainstream are investigated with regard to their impact on cooling effectiveness. The results obtained provide insight into the film cooling performance of the gases and the heat transfer characteristics associated with these three gases. An injector taper angle of 30° results in the most effective cooling among the configurations considered (0°, 15°, 30° and 45°). Mixing of the coolant with the hot stream is examined based on the distributions of velocity, temperature and species. The higher values of cooling effectiveness for Helium are attributed to its thermophysical properties and the reduced rate of mixing with the hot stream. The results further indicate that through optimization of the blowing ratio and the coolant injector configuration, the film cooling effectiveness can be substantially improved.

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“…These experiments demonstrated that the swirl in the mainstream had a significant effect on the film-cooling performance. The role of mainstream flow velocity in a film-cooling duct was studied by O'Connor and Haji-Sheikh [20] and Kuo et al [21]. Kuo et al's experimental observations revealed film cooling to be effective in subsonic flow, but not in supersonic flow.…”

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confidence: 99%

Internal Wall-Jet Film Cooling with Straight Cylindrical Holes

Shine

Kumar

Suresh

2012

Journal of Thermophysics and Heat Transfer

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Experimental and computational results are presented that describe gaseous film-cooling performance of straight cylindrical cooling holes inside a cylindrical test section similar to a rocket combustion chamber. Experiments were performed using hot air as the core gas and gaseous nitrogen as the film coolant. A three-dimensional multispecies computational model using finite volume formulation has been developed and validated against the experimental data. Film-cooling performance is predicted for a variety of imposed geometrical parameters and blowing ratios. Results show local and spatially averaged performance change with blowing ratio due to differences in the magnitude of vortices created downstream of the coolant injection and the jet exit momentum. It is observed that higher mixing of coolant with the mainstream and high vorticity levels negates the presence of more coolant availability at higher blowing ratios and results in an optimum blowing ratio for a given geometric configuration. Higher effectiveness is obtained for the conjugate walls throughout the test section except at regions very close to the coolant injection. High conductive walls produced a negative heat flux condition immediately downstream of the coolant jet exit, indicating that a highly conductive wall is not a proper choice for internal wall-jet film-cooling applications. The results could provide useful input for analysis and optimization of straight cylindrical coolant holes.

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Role of mainstream flow velocity in film cooling in a duct

Cited by 9 publications

References 8 publications

Effect of injector configuration in rocket nozzle film cooling

Effect of injector configuration in rocket nozzle film cooling

Enhancement of Film Cooling Effectiveness in a Supersonic Nozzle

Internal Wall-Jet Film Cooling with Straight Cylindrical Holes

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