Effects of Swirl Velocities From Fan Assemblies Mounted on Lifting Surfaces

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Alexandros Terzis ◽  
Charilaos Kazakos ◽  
Nikolaos Papadopoulos ◽  
Anestis Kalfas ◽  
Pavlos K. Zachos ◽  
...  
Keyword(s):  
Flight Control ◽  
Film Cooling ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Vortex Pair ◽  
Main Stream ◽  
Injection Hole ◽  
Two Fluids ◽  
Swirl Velocity ◽  
Wide Range

The penetration of a jet of fluid into a traversal moving stream is a basic configuration of a wide range of engineering applications, such as film cooling and V/STOL aircrafts. This investigation examines experimentally the effect of blowing ratio of fans in crossflow, and numerically, the effect of the swirl velocity of jets in crossflow, downstream of the injection hole. The experimental results indicated an agreement with typically straight jets in crossflow (no vorticity), illustrating that the trace of the jet, remains close to the wall and subsequently enhance cooling at low blowing ratios in the case of turbine blade applications. However, the rotation of the jet results in an imparity between the two parts of the counter rotating vortex pair and as a consequence, the injected fluid not only bends in the direction of the main stream but also diverts in the direction of the rotation in order to conserve its angular momentum. The induction of the swirl velocity on the injected jet destructs one of the two parts of the kidney vortex, which entrains fluid from the crossflow to the jet promoting the mixing between the two fluids while the trace of a swirled jet remains closer to the wall downstream of the injection hole. Finally, the use of contrarotating jet or fan configurations reduces the wall shear stress in a very great extent, leading to better thermal protection of turbine blades, as well as cancels out the yaw torques of each fan separately, resulting in better flight control of typical lift surface.

Effects of the Swirl Velocity of a Jet in Crossflow From Fan Assemblies Mounted on Lifting Surfaces

2010 ◽  
Author(s):  
Alexandros Terzis ◽  
Charilaos Kazakos ◽  
Nikolaos Papadopoulos ◽  
Anestis I. Kalfas ◽  
Pavlos K. Zachos ◽  
...  
Keyword(s):  
Flight Control ◽  
Film Cooling ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Cross Flow ◽  
Vortex Pair ◽  
Main Stream ◽  
Injection Hole ◽  
Swirl Velocity ◽  
Wide Range

The penetration of a jet of fluid into a traversal moving stream is a basic configuration of a wide range of engineering applications, such as film cooling and V/STOL aircrafts. This investigation examines experimentally the effect of blowing ratio of fans in cross flow, and numerically, the effect of the swirl velocity of jets in cross flow, downstream of the injection hole. The experimental results indicated an agreement with typically straight jets in cross flow (no vorticity), illustrating that the trace of the jet, remains close to the wall and subsequently enhance cooling at low blowing ratios in the case of turbine blade applications. However, the rotation of the jet results in an imparity between the two parts of the counter rotating vortex pair (CVP), and as a consequence, the injected fluid not only bends in the direction of the main stream but also diverts in the direction of the rotation, in order to conserve its angular momentum. The induction of the swirl velocity on the injected jet destructs one of the two parts of the kidney vortex which entrains fluid from the cross flow to the jet promoting the mixing between the two fluids, while the trace of a swirled jet remains closer to the wall downstream of the injection hole. Finally, the use of contra rotating jet or fan configurations reduces the wall shear stress in a very great extent, leading to better thermal protection of turbine blades, as well as cancels out the yaw torques of each fan separately, resulting in better flight control of typical lift surface.

Parametric Study on Anti-Vortex Film Cooling Hole Arrangements

2014 ◽  
Vol 660 ◽  
pp. 664-668
Author(s):  
Kamil Abdullah ◽  
Hazim Fadli Aminnuddin ◽  
Akmal Nizam Mohammed
Keyword(s):  
Film Cooling ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Vortex Pair ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Lateral Film ◽  
Lift Off

Film cooling has been extensively used to provide thermal protection for the external surface of the gas turbine blades. Numerous number of film cooling holes designs and arrangements have been introduced. The main motivation of these designs and arrangements are to reduce the lift-off effect cause by the counter rotating vortices (CRVP) produce by cylindrical cooling hole. One of the efforts is the introduction of newly found anti-vortex film cooling design. The present study focuses on anti-vortex holes arrangement consists of a main hole and pair of smaller holes. All three holes share a common inlet with the outlet of the smaller holes varies base on it relative position towards the main hole. Three anti-vortex holes arrangements have been considered; downstream anti-vortex hole arrangement (DAV), lateral anti-vortex hole arrangement (LAV), and upstream anti-vortex hole arrangement (UAV). In addition, a single hole (SH) film cooling has also been considered as the baseline. The investigation make used of ANSYS CFX software ver. 14. The investigations are made through Reynolds Average Navier Stokes analyses with the application of shear k-ε turbulence model. The results show that the anti-vortex designs produce significant improvement in term of film cooling effectiveness and distribution. The LAV arrangement shows the best film cooling effectiveness distribution among all considered cases and is consistent for all blowing ratios (BR). The results also unveil the formation of new vortex pair on both side of the primary hole CRVP. Interaction between the new vortices and the main CRVP structure reduce the lift off explaining the increased lateral film effectiveness.

scholarly journals Numerical Prediction of Film Cooling Effectiveness and the Associated Aerodynamic Losses With a Three-Dimensional Calculation Procedure

1990 ◽  
Author(s):  
G. H. Dibelius ◽  
R. Pitt ◽  
B. Wen
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Reverse Flow ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Temperature Pattern ◽  
Main Stream ◽  
Cooling Efficiency ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Losses

Film cooling of turbine blades by injecting air through holes or slots affects the main stream flow. A numerical model has been developed to predict the resulting three-dimensional flow and the temperature pattern under steady flow conditions. An elliptic procedure is used in the near injection area to include reverse flow situations, while in the upstream area as well as far downstream a partial-parabolic procedure is applied. As first step an adiabatic wall has been assumed as boundary condition, since for this case experimental data are readily available for comparison. At elevated momentum blowing rates, zones of reverse flow occur downstream of the injection holes resulting in a decrease of cooling efficiency. A variation of the relevant parameters momentum blowing rate m, injection angle α and ratio of hole spacing to diameter s/d revealed the combination of m ≈ 1, α ≈ 30° and s/d ≈ 2 to be the optimum with respect to the averaged cooling efficiency and to the aerodynamic losses. Cooling is more efficient with slots than with a row of holes not considering the related problems of manufacture and service life. The calculated temperature patterns compare well with the experimental data available.

Effects of an Embedded Vortex on Injectant From a Single Film-Cooling Hole in a Turbulent Boundary Layer

1990 ◽  
Vol 112 (3) ◽  
pp. 428-436 ◽  
Author(s):  
P. M. Ligrani ◽  
W. Williams
Keyword(s):  
Heat Transfer ◽  
Vortex Core ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Stream Velocity ◽  
Vortex Center ◽  
Injection Hole ◽  
Cooling Hole

Effects of embedded longitudinal vortices on heat transfer in turbulent boundary layers with injection from a single film-cooling hole are described. These results were obtained at a free-stream velocity of 10 m/s, with a film-cooling hole inclined 30 deg to the horizontal and a blowing ratio of about 0.50. The ratio of vortex core diameter to injection hole diameter was 1.58, and the ratio of circulation to injection velocity time hole diameter was about 3.16. Coolant distributions and spatially resolved heat transfer measurements indicate that injection hole centerlines must be at least 2.9–3.4 vortex core diameters away from the vortex center in the lateral direction to avoid significant alterations to wall heat transfer and distributions of film coolant. Under these circumstances, protection from film cooling is evident at least up to 55 hole diameters downstream of injection. When the injection hole is closer to the vortex center, secondary flows convect most injectant into the vortex upwash and thermal protection from film cooling is destroyed for streamwise locations from the injection hole greater than 17.5 hole diameters.

Effect of Internal Coolant Crossflow on the Effectiveness of Shaped Film-Cooling Holes

2003 ◽  
Vol 125 (3) ◽  
pp. 547-554 ◽  
Author(s):  
Michael Gritsch ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Turbine Blades ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Wide Range

Film-cooling was the subject of numerous studies during the past decades. However, the effect of flow conditions on the entry side of the film-cooling hole on film-cooling performance has surprisingly not received much attention. A stagnant plenum which is widely used in experimental and numerical studies to feed the holes is not necessarily a right means to re-present real engine conditions. For this reason, the present paper reports on an experimental study investigating the effect of a coolant crossflow feeding the holes that is oriented perpendicular to the hot gas flow direction to model a flow situation that is, for instance, of common use in modern turbine blades’ cooling schemes. A comprehensive set of experiments was performed to evaluate the effect of perpendicular coolant supply direction on film-cooling effectiveness over a wide range of blowing ratios (M=0.5…2.0) and coolant crossflow Mach numbers Mac=0…0.6. The coolant-to-hot gas density ratio, however, was kept constant at 1.85 which can be assumed to be representative for typical gas turbine applications. Three different hole geometries, including a cylindrical hole as well as two holes with expanded exits, were considered. Particularly, two-dimensional distributions of local film-cooling effectiveness acquired by means of an infrared camera system were used to give detailed insight into the governing flow phenomena. The results of the present investigation show that there is a profound effect of how the coolant is supplied to the hole on the film-cooling performance in the near hole region. Therefore, crossflow at the hole entry side has be taken into account when modeling film-cooling schemes of turbine bladings.

Effect of blowing ratio on Film-Cooling effectiveness of Ginkgo Shaped Holes: A numerical approach

2021 ◽  
Author(s):  
Muhammad Awais ◽  
Reaz Hasan ◽  
Md. Hamidur Rahman
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Bottom Surface ◽  
Inlet Temperature ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Lift Off

Modern gas turbine engines operate at significantly high temperatures to improve thermal efficiency and power output to a greater extent. The enhancement in rotor inlet temperature (RIT) increases the heat transfer rate to the turbine blades which requires sophisticated cooling schemes to maintain the blade temperature in acceptable levels. Therefore, the present work refers to the numerical investigation of film cooling technique applied in gas turbines. The cooling performance of two different shaped holes namely Ginkgo Forward (GF) and Ginkgo Reverse (GR)) were investigated in terms of centerline and local lateral effectiveness and comprehensive comparison was made with the cooling performance of cylindrical (CY) hole. The investigations were performed at two density ratios (DR=1.6, 2.0) and three different blowing ratios (BR=1.0, 1.5 and 2.0). At all the operating conditions, the results demonstrated significant augmentation in centerline and lateral effectiveness when GR shaped hole was employed followed by the GF and CY cooling holes. For shaped holes, the low velocity gradient through the film alleviated jet lift off and turbulence intensity resulting in decreased entrainment of hot gas to bottom surface. To conclude, the lateral coverage due to the shaped cooling holes significantly enhanced the thermal protection and overall cooling performance.

Numerical Benchmark of Nonconventional RANS Turbulence Models for Film and Effusion Cooling

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Cosimo Bianchini ◽  
Luca Andrei ◽  
Antonio Andreini ◽  
Bruno Facchini
Keyword(s):  
Film Cooling ◽  
Eddy Viscosity ◽  
Computational Study ◽  
Turbine Blades ◽  
Density Ratio ◽  
Turbulence Models ◽  
Single Row ◽  
Turbulent Reynolds Number ◽  
Wide Range ◽  
Asme Turbo Expo

Over the course of the years, several turbulence models specifically developed to improve the predicting capabilities of conventional two-equations Reynolds-averaged Navier–Stokes (RANS) models have been proposed. They have, however, been mainly tested against experiments only comparing with standard isotropic models, in single hole configuration and for very low blowing ratio. A systematic benchmark of the various nonconventional models exploring a wider range of application is hence missing. This paper performs a comparison of three recently proposed models over three different test cases of increasing computational complexity. The chosen test matrix covers a wide range of blowing ratios (0.5–3.0) including both single row and multi-row cases for which experimental data of reference are available. In particular the well-known test by Sinha et al. (1991, “Film-Cooling Effectiveness Downstream of a Single Row of Holes with Variable Density Ratio,” J. Turbomach., 113, pp. 442–449) at BR = 0.5 is used in conjunction with two in-house carried out experiments: a single row film-cooling test at BR = 1.5 and a 15 rows test plate designed to study the interaction between slot and effusion cooling at BR = 3.0. The first two considered models are based on a tensorial definition of the eddy viscosity in which the stream-span position is augmented to overcome the main drawback connected with standard isotropic turbulence models that is the lower lateral spreading of the jet downwards the injection. An anisotropic factor to multiply the off diagonal position is indeed calculated from an algebraic expression of the turbulent Reynolds number developed by Bergeles et al. (1978, “The Turbulent Jet in a Cross Stream at Low Injection Rates: A Three-Dimensional Numerical Treatment,” Numer. Heat Transfer, 1, pp. 217–242) from DNS statistics over a flat plate. This correction could be potentially implemented in the framework of any eddy viscosity model. It was chosen to compare the predictions of such modification applied to two among the most common two-equation turbulence models for film-cooling tests, namely the two-layer (TL) model and the k–ω shear stress transport (SST), firstly proposed and tested in the past respectively by Azzi and Lakeal (2002, “Perspectives in Modeling Film Cooling of Turbine Blades by Transcending Conventional Two-Equation Turbulence Models,” J. Turbomach., 124, pp. 472–484) and Cottin et al. (2011, “Modeling of the Heat Flux For Multi-Hole Cooling Applications,” Proceedings of the ASME Turbo Expo, Paper No. GT2011-46330). The third model, proposed by Holloway et al. (2005, “Computational Study of Jet-in-Crossflow and Film Cooling Using a New Unsteady-Based Turbulence Model,” Proceedings of the ASME Turbo Expo, Paper No. GT2005-68155), involves the unsteady solution of the flow and thermal field to include the short-time response of the stress tensor to rapid strain rates. This model takes advantage of the solution of an additional transport equation for the local effective total stress to trace the strain rate history. The results are presented in terms of adiabatic effectiveness distribution over the plate as well as spanwise averaged profiles.

The Influences of Off-Design Incidence Angle and Discrete Hole Shapes on Film Cooling Effectiveness

1986 ◽  
Author(s):  
Shao-Yen Ko ◽  
Deng-Ying Liu ◽  
Jian-Guo Jia ◽  
Fu-Kang Tsou
Keyword(s):  
Carbon Dioxide ◽  
Film Cooling ◽  
Convex Surface ◽  
Incidence Angle ◽  
Turbine Blades ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Ejection Angle ◽  
Wide Range

Detailed tests have been conducted in the cascade heat transfer wind tunnel in order to investigate film cooling effectiveness of single and double-row discrete holes on the leading edge of the pressure surface of a turbine blade. Mass transfer analogy has been used in this experiment. Carbon dioxide was added to the cooling air. The concentration distribution of the carbon dioxide downstream of the cooling film was measured by chromatograph. Two sets of testing blades with discrete holes of different shapes were used. The first set had round holes with diameter of 1.5 mm, and the ejection angle was 70°. The second set had rectangular holes with width of 1.0 mm and whose ratio of length to width was 5, the ejection angle being 90°. The holes between rows were arranged in staggered pattern. It was found that the incidence angle has strong influence on film cooling of turbine blades. The film cooling effectiveness near the ejection hole on the pressure surface (concave surface) is higher than that on a flat plate and on a suction surface (convex surface). Over a wide range of blowing ratio M, the film cooling effectiveness of rectangular hole is much higher than round holes.

Effects of Vortices With Different Circulations on Heat Transfer and Injectant Downstream of a Single Film-Cooling Hole in a Turbulent Boundary Layer

1991 ◽  
Vol 113 (3) ◽  
pp. 433-441 ◽  
Author(s):  
P. M. Ligrani ◽  
C. S. Subramanian ◽  
D. W. Craig ◽  
P. Kaisuwan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Vortex Core ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Injection Hole ◽  
Cooling Hole

Results are presented that illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a single film-cooling hole in a turbulent boundary layer. Attention is focused on the changes resulting as circulation magnitudes of the vortices are varied from 0.0 to 0.15 m2/s. Mean temperature results are presented that show how injectant is distorted and redistributed by vortices, along with heat transfer measurements and mean velocity surveys. Injection hole diameter is 0.952 cm to give a ratio of vortex core diameter to hole diameter of about 1.5–1.6. The free-stream velocity is maintained at 10 m/s, and the blowing ratio is approximately 0.5. The film-cooling hole is oriented 30 deg with respect to the test surface. Stanton numbers are measured on a constant heat flux surface with a nondimensional temperature parameter of about 1.5. Two different situations are studied: one where the injection hole is beneath the vortex downwash, and one where the injection hole is beneath the vortex upwash. For both cases, vortex centers pass well within 2.9 vortex core diameters of the centerline of the injection hole. To quantify the influences of the vortices on the injectant and local heat transfer, the parameter S is used, defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. When S is greater than 1.0–1.5, injectant is swept into the vortex upwash and above the vortex core by secondary flows, and Stanton number data show evidence of injectant beneath the vortex core and downwash near the wall for x/d only up to 33.6. For larger x/d, local Stanton numbers are augmented by the vortices by as much as 23 percent relative to film-cooled boundary layers with no vortices. When S is less than 1.0–1.5, some injectant remains near the wall beneath the vortex core and downwash where it continues to provide some thermal protection. In some cases, the protection provided by film cooling is augmented because of vortex secondary flows, which cause extra injectant to accumulate near vortex upwash regions.

scholarly journals Effect of combined hole configuration on film cooling with and without mist injection

2018 ◽  
Vol 22 (5) ◽  
pp. 1923-1931
Author(s):  
Ke Tian ◽  
Jin Wang ◽  
Chao Liu ◽  
Jakov Baleta ◽  
Li Yang ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Cylindrical Hole ◽  
Inlet Temperature ◽  
Main Stream ◽  
Engine Efficiency ◽  
Hole Configuration ◽  
Harsh Environmental Condition ◽  
Droplet Sizes

Turbine blades operate under a harsh environmental condition, and the inlet temperature of gas turbines is increasing with requirement of high engine efficiency. Some cooling schemes are adopted to prevent these blades from the thermal erosion of the hot mainstream. Film cooling technology is used widely and effectively in gas turbines. The coolant air is suppressed to the wall by the main-stream after jetting out of the film hole. A new hole configuration is first pro-posed to improve the film cooling characteristics in this paper. Comparison be-tween a conventional cylindrical hole and a new combined hole is conducted by CFD, and effects of various blowing ratios and droplet sizes are also investigated. Results show that the combined hole configuration provides a wider coverage than that in the cylindrical hole configuration case at high blowing ratios (M = 1.0 and M = 1.5). In addition, the film cooling with mist injection also provides a significant enhancement on cooling performance especially for the combined hole case with a small droplet size (10?5 m).

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