Droplet impacts are rarely normal to the target substrate during thermal spray processing because of droplet dispersion in the spray cone or because the substrate is moving. A model for droplet spreading and solidification after off-normal impact on a cold substrate was developed. This model is based on Madejski’s energy conservation model but uses a three-dimensional velocity field, which satisfies the no slip condition at the solid front, the no shear condition at the free surface as well as the continuity equation. Furthermore, the present model assumes the shape of the spreading droplet to have a non-axisymmetric shape (limaçon perimeter and a uniform height). Stefan solidification is assumed. A mechanical energy balance is used to describe the deformation of the spreading droplet. The resulting integro-differential equation is solved numerically using a modified Euler predictor-corrector method. This model was validated by comparison with existing energy-conservation models in the case of normal impact. The results indicate both a decrease in the final splat diameter and a decrease in the expansion rate of the spreading droplet as the impact angle increases, as measured from the normal axis. The resulting impacts are therefore less efficient as the impact angle increases.
{"title":"Micro-Scale Aspects of Spray Deposition Processing: A Semi-Analytical Model for Droplet Spreading and Solidification at Off-Normal Impact Angles","authors":"S. Johnson, J. Delplanque","doi":"10.1115/imece2000-1496","DOIUrl":"https://doi.org/10.1115/imece2000-1496","url":null,"abstract":"\u0000 Droplet impacts are rarely normal to the target substrate during thermal spray processing because of droplet dispersion in the spray cone or because the substrate is moving. A model for droplet spreading and solidification after off-normal impact on a cold substrate was developed. This model is based on Madejski’s energy conservation model but uses a three-dimensional velocity field, which satisfies the no slip condition at the solid front, the no shear condition at the free surface as well as the continuity equation. Furthermore, the present model assumes the shape of the spreading droplet to have a non-axisymmetric shape (limaçon perimeter and a uniform height). Stefan solidification is assumed. A mechanical energy balance is used to describe the deformation of the spreading droplet. The resulting integro-differential equation is solved numerically using a modified Euler predictor-corrector method. This model was validated by comparison with existing energy-conservation models in the case of normal impact. The results indicate both a decrease in the final splat diameter and a decrease in the expansion rate of the spreading droplet as the impact angle increases, as measured from the normal axis. The resulting impacts are therefore less efficient as the impact angle increases.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128336053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Previous study of carrier gas flow in rapid chemical vapor deposition (RCVD) reactors has been limited mostly to numerical simulations and flow visualizations. In the present work flow regimes were observed and temperatures were measured in a vertical axisymmetric pedestal RCVD reactor using flow visualization and Rayleigh light scattering (RLS) for noninvasive temperature measurement. Flow visualizations revealed that the flow undergoes complex transitions between stable flow regimes as heating occurs. The two dominant stable flow regimes were buoyant stable (BS) and momentum stable (MS). RLS was used to determine the instantaneous carrier gas temperature at discrete points in the test section. The flow regimes and their transition points were easily recognized and agreed with flow visualization data. The flow visualizations and RLS tests showed identifiable trends in transition points between flow regimes and in the types of regimes encountered. These trends were dependent on Grashof number and Reynolds number.
{"title":"Flow Regimes and Transitions in a Rapid Chemical Vapor Deposition Reactor Using Flow Visualization and Rayleigh Light Scattering","authors":"Angelo G. Mathews, J. Peterson","doi":"10.1115/imece2000-1479","DOIUrl":"https://doi.org/10.1115/imece2000-1479","url":null,"abstract":"\u0000 Previous study of carrier gas flow in rapid chemical vapor deposition (RCVD) reactors has been limited mostly to numerical simulations and flow visualizations. In the present work flow regimes were observed and temperatures were measured in a vertical axisymmetric pedestal RCVD reactor using flow visualization and Rayleigh light scattering (RLS) for noninvasive temperature measurement. Flow visualizations revealed that the flow undergoes complex transitions between stable flow regimes as heating occurs. The two dominant stable flow regimes were buoyant stable (BS) and momentum stable (MS). RLS was used to determine the instantaneous carrier gas temperature at discrete points in the test section. The flow regimes and their transition points were easily recognized and agreed with flow visualization data. The flow visualizations and RLS tests showed identifiable trends in transition points between flow regimes and in the types of regimes encountered. These trends were dependent on Grashof number and Reynolds number.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125461443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.
{"title":"Leakage Flow and Heat Transfer Over Shrouded Turbine Blades","authors":"Yumin Xiao, R. Amano","doi":"10.1115/imece2000-1458","DOIUrl":"https://doi.org/10.1115/imece2000-1458","url":null,"abstract":"In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125281681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The process of film cooling is known to severely disturb the boundary layer around a turbine airfoil. Since most film-cooled airfoils have more than one injection station, the flow field approaching a row of film cooling holes could be altered by the presence of an upstream cooling station. To investigate this possibility, an experimental investigation was conducted on the suction side of a scaled-up turbine vane. Adiabatic effectiveness measurements were made downstream of a single row of cooling holes both with and without the upstream showerhead holes operating. A range of suction side blowing ratios, 0.3 ≤ M ≤ 1.3, were investigated with large-scale mainstream turbulence intensities of Tu∞ = 0.5% and Tu∞ = 21%. The effects of the showerhead coolant were evaluated at an engine-typical showerhead blowing ratio of Msh = 1.6, with three of the six rows of cooling holes in the showerhead directed towards the suction side of the airfoil. Experiments were conducted with a coolant-to-mainstream density ratio of DR = 1.6. An infrared camera was used to obtain spatially-resolved surface temperature measurements, which were corrected for conduction effects and converted to adiabatic effectiveness. The results showed that showerhead coolant had a strong impact on suction side adiabatic effectiveness levels under low mainstream turbulence. Although effectiveness levels increased with the showerhead operating, the suction side coolant jets increased dispersion of the showerhead coolant. Under high mainstream turbulence conditions, there was very little interaction between the showerhead coolant and the suction side coolant jets. Adiabatic effectiveness levels were considerably lower than those for the low turbulence case, which was partially due to increased dispersion of the showerhead coolant upstream of the suction side holes. The superposition model over-predicted adiabatic effectiveness levels under low mainstream turbulence conditions, but was very effective in predicting the combined performance of the showerhead and the suction side cooling holes under high mainstream turbulence conditions.
{"title":"Effects of Showerhead Cooling on Turbine Vane Suction Side Film Cooling Effectiveness","authors":"Marcia I. Ethridge, J. M. Cutbirth, D. Bogard","doi":"10.1115/imece2000-1462","DOIUrl":"https://doi.org/10.1115/imece2000-1462","url":null,"abstract":"\u0000 The process of film cooling is known to severely disturb the boundary layer around a turbine airfoil. Since most film-cooled airfoils have more than one injection station, the flow field approaching a row of film cooling holes could be altered by the presence of an upstream cooling station. To investigate this possibility, an experimental investigation was conducted on the suction side of a scaled-up turbine vane. Adiabatic effectiveness measurements were made downstream of a single row of cooling holes both with and without the upstream showerhead holes operating. A range of suction side blowing ratios, 0.3 ≤ M ≤ 1.3, were investigated with large-scale mainstream turbulence intensities of Tu∞ = 0.5% and Tu∞ = 21%. The effects of the showerhead coolant were evaluated at an engine-typical showerhead blowing ratio of Msh = 1.6, with three of the six rows of cooling holes in the showerhead directed towards the suction side of the airfoil. Experiments were conducted with a coolant-to-mainstream density ratio of DR = 1.6. An infrared camera was used to obtain spatially-resolved surface temperature measurements, which were corrected for conduction effects and converted to adiabatic effectiveness. The results showed that showerhead coolant had a strong impact on suction side adiabatic effectiveness levels under low mainstream turbulence. Although effectiveness levels increased with the showerhead operating, the suction side coolant jets increased dispersion of the showerhead coolant. Under high mainstream turbulence conditions, there was very little interaction between the showerhead coolant and the suction side coolant jets. Adiabatic effectiveness levels were considerably lower than those for the low turbulence case, which was partially due to increased dispersion of the showerhead coolant upstream of the suction side holes. The superposition model over-predicted adiabatic effectiveness levels under low mainstream turbulence conditions, but was very effective in predicting the combined performance of the showerhead and the suction side cooling holes under high mainstream turbulence conditions.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"98 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123063781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The warpage of thermoset composite structures during the manufacturing process is a direct consequence of residual stress development. The capability to predict residual stresses is crucial to the manufacture of dimensionally accurate composite structures. This paper is focused on understanding the fundamental issues leading to residual stresses in thermoset polymer composites and their effect on the dimensional accuracy of the manufactured components. Special emphasis is placed on the simulation of autoclave curing and hot pressing. A three-dimensional coupled thermo-chemo-viscoelastic model is developed to simulate the heat transfer, curing, residual stresses and deformation of a composite part during the entire cure cycle. The predicted values of curvature for cross-ply graphite-epoxy laminates agree well with experimental observations. The numerical result indicates that a significant fraction of the residual stress develops before cooldown. Detailed studies are also performed to examine the springforward phenomenon in L-shaped composite parts. The finite element results show that mold design (male vs. female mold), mold thermal expansion, and part thickness all play an important role on the final shape of the parts.
{"title":"Effects of the Manufacturing Process on the Dimensional Accuracy of Thermoset Composites","authors":"Qi Zhu, P. Geubelle","doi":"10.1115/imece2000-1490","DOIUrl":"https://doi.org/10.1115/imece2000-1490","url":null,"abstract":"\u0000 The warpage of thermoset composite structures during the manufacturing process is a direct consequence of residual stress development. The capability to predict residual stresses is crucial to the manufacture of dimensionally accurate composite structures. This paper is focused on understanding the fundamental issues leading to residual stresses in thermoset polymer composites and their effect on the dimensional accuracy of the manufactured components. Special emphasis is placed on the simulation of autoclave curing and hot pressing. A three-dimensional coupled thermo-chemo-viscoelastic model is developed to simulate the heat transfer, curing, residual stresses and deformation of a composite part during the entire cure cycle. The predicted values of curvature for cross-ply graphite-epoxy laminates agree well with experimental observations. The numerical result indicates that a significant fraction of the residual stress develops before cooldown. Detailed studies are also performed to examine the springforward phenomenon in L-shaped composite parts. The finite element results show that mold design (male vs. female mold), mold thermal expansion, and part thickness all play an important role on the final shape of the parts.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131171269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Heat transfer by phase change is an attractive method of cooling since large amounts of heat can be removed with relatively small temperature differences. Droplet cooling is one method whereby very high heat transfer rates coupled with good temperature uniformity across surfaces can be provided, which is important in microelectronics where even small temperature gradients across the chip can cause component failure. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. Significant time and space resolved variations in wall heat fluxes were exhibited during boiling and evaporation. The droplet behavior with wall interaction was simultaneously viewed using a high-speed digital video camera. Local heat transfer measurements can provide much needed information regarding the relevant wall heat transfer mechanisms by pinpointing when and where large amounts of heat are removed. This study should result in benchmark data against which numerical calculations can be compared.
{"title":"Heat Transfer Characteristics of Single Droplet Cooling Using a Microscale Heater Array","authors":"Jungho Lee, Jungho Kim, K. Kiger, B. Horacek","doi":"10.1115/imece2000-1497","DOIUrl":"https://doi.org/10.1115/imece2000-1497","url":null,"abstract":"Heat transfer by phase change is an attractive method of cooling since large amounts of heat can be removed with relatively small temperature differences. Droplet cooling is one method whereby very high heat transfer rates coupled with good temperature uniformity across surfaces can be provided, which is important in microelectronics where even small temperature gradients across the chip can cause component failure. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. Significant time and space resolved variations in wall heat fluxes were exhibited during boiling and evaporation. The droplet behavior with wall interaction was simultaneously viewed using a high-speed digital video camera. Local heat transfer measurements can provide much needed information regarding the relevant wall heat transfer mechanisms by pinpointing when and where large amounts of heat are removed. This study should result in benchmark data against which numerical calculations can be compared.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114585159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A three dimensional numerical analysis of a solid irradiated by a moving laser heat source in a quasi-steady state is carried out. The thermophysical properties of the material are considered to be temperature dependent. The dependence of the solution on the radiative and convective heat losses, the latter due to an impinging jet on the upper surface, is highlighted; the dependence of the temperature distribution on the Reynolds number of the jet is also presented. Different thicknesses and widths are shown to have discrepant influences on the induced thermal fields for a Gaussian laser source. The parametric analysis shows the thermal profiles to be strongly dependent on the jet Reynolds number. The thermal field is almost symmetric with respect to the spot center for a Peclet number equal to 0.1. The thermal penetration decreases as the Peclet number increases.
{"title":"A Parametric Study of the Quasi-Steady State Temperature Field by a Moving Heat Source for Surface Treating","authors":"N. Bianco, O. Manca","doi":"10.1115/imece2000-1486","DOIUrl":"https://doi.org/10.1115/imece2000-1486","url":null,"abstract":"\u0000 A three dimensional numerical analysis of a solid irradiated by a moving laser heat source in a quasi-steady state is carried out. The thermophysical properties of the material are considered to be temperature dependent. The dependence of the solution on the radiative and convective heat losses, the latter due to an impinging jet on the upper surface, is highlighted; the dependence of the temperature distribution on the Reynolds number of the jet is also presented. Different thicknesses and widths are shown to have discrepant influences on the induced thermal fields for a Gaussian laser source. The parametric analysis shows the thermal profiles to be strongly dependent on the jet Reynolds number. The thermal field is almost symmetric with respect to the spot center for a Peclet number equal to 0.1. The thermal penetration decreases as the Peclet number increases.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131576228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper investigates the need to develop an advanced control system for plasma spray deposition. The limitations and performance capability of both feed forward and real-time control are evaluated. Critical system characteristics for developing such controllers are experimentally identified including dominant nonlinearalities; dynamics, cross-coupling, distributions, and sensor issues.
{"title":"System Characterization and Plasma-Particle Distribution Analysis for Development of a Closed Loop Control for Plasma Spray","authors":"M. Gevelber, D. Wroblewski, J. Fincke, W. Swank","doi":"10.1115/imece2000-1500","DOIUrl":"https://doi.org/10.1115/imece2000-1500","url":null,"abstract":"\u0000 This paper investigates the need to develop an advanced control system for plasma spray deposition. The limitations and performance capability of both feed forward and real-time control are evaluated. Critical system characteristics for developing such controllers are experimentally identified including dominant nonlinearalities; dynamics, cross-coupling, distributions, and sensor issues.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130840549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Czochralski (Cz) growth during seeding and shouldering of silicon single crystal has been studied. During seeding, the diameter increases from a small value to the desired value of the fully-grown crystal. The convection in the melt, conduction in the crystal and radiation from the melt surface and crystal, surface tension at the free surface of the melt and crystal rotation have been considered to investigate the effect of seeding on thermal transport. The rotational Reynolds number, the radiation from the crystal and Marangoni number are varied to investigate their effect on the interface shape. A few selected cases have been studied using a cylindrical crystal to understand the effect of geometry on the heat transfer rate and subsequently on the interface shape. The governing equations are solved using the curvilinear finite volume discretization scheme and the grids are redistributed using the multizone adaptive grid generation after each iteration. The movement of free surface is taken care by employing suitable equations for energy and stress balance. Results show the dependency of both the radiation from the crystal and rotation of the crystal on the interface shape.
{"title":"Thermal Transport During Seeding and Shouldering in the Czochralski Crystal Growth","authors":"A. Saha, H. Zhang, V. Prasad","doi":"10.1115/imece2000-1483","DOIUrl":"https://doi.org/10.1115/imece2000-1483","url":null,"abstract":"\u0000 Czochralski (Cz) growth during seeding and shouldering of silicon single crystal has been studied. During seeding, the diameter increases from a small value to the desired value of the fully-grown crystal. The convection in the melt, conduction in the crystal and radiation from the melt surface and crystal, surface tension at the free surface of the melt and crystal rotation have been considered to investigate the effect of seeding on thermal transport. The rotational Reynolds number, the radiation from the crystal and Marangoni number are varied to investigate their effect on the interface shape. A few selected cases have been studied using a cylindrical crystal to understand the effect of geometry on the heat transfer rate and subsequently on the interface shape. The governing equations are solved using the curvilinear finite volume discretization scheme and the grids are redistributed using the multizone adaptive grid generation after each iteration. The movement of free surface is taken care by employing suitable equations for energy and stress balance. Results show the dependency of both the radiation from the crystal and rotation of the crystal on the interface shape.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124736193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of discrete delta-shaped tabs on the film cooling performance from a row of cylindrical holes is investigated. The holes are inclined at 35° along the streamwise direction. Three tab locations are investigated: (1) tabs placed along the upstream edge of the hole; (b) tab placed along the downstream edge of the hole; and (3) tabs placed along the lateral edges of the hole. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and free-stream turbulence intensity in the low speed wind tunnel are 8.5 m/s and 6% respectively and the Reynolds number based on hole diameter is 6375. Three blowing ratios of 0.56, 1.13, and 1.7 are tested. Results show that the tab placed upstream of the hole covering the 33% of the hole exit provides the highest film effectiveness compared to other tab locations studied. This is because the jet lift-off in the presence of the tabs is reduced and there is greater lateral spreading of the jet.
{"title":"Film Cooling on a Flat Surface With a Single Row of Cylindrical Angled Holes: Effect of Discrete Tabs","authors":"S. Ekkad, H. Nasir, S. Acharya","doi":"10.1115/imece2000-1455","DOIUrl":"https://doi.org/10.1115/imece2000-1455","url":null,"abstract":"\u0000 The effect of discrete delta-shaped tabs on the film cooling performance from a row of cylindrical holes is investigated. The holes are inclined at 35° along the streamwise direction. Three tab locations are investigated: (1) tabs placed along the upstream edge of the hole; (b) tab placed along the downstream edge of the hole; and (3) tabs placed along the lateral edges of the hole. Measurements were carried out in a low-speed wind tunnel using the transient liquid crystal technique. The mainstream velocity and free-stream turbulence intensity in the low speed wind tunnel are 8.5 m/s and 6% respectively and the Reynolds number based on hole diameter is 6375. Three blowing ratios of 0.56, 1.13, and 1.7 are tested. Results show that the tab placed upstream of the hole covering the 33% of the hole exit provides the highest film effectiveness compared to other tab locations studied. This is because the jet lift-off in the presence of the tabs is reduced and there is greater lateral spreading of the jet.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122850690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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