• The KSFM Journal of Fluid Machinery
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• v.15 no.4
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• pp.33-41
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• 2012

In the present work, a parametric study on double-jet film-cooling has been carried out to enhance the film-cooling effectiveness using three-dimensional Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as the turbulence closure. The lateral ejection angles and the lateral and streamwise distance between the centers of the cooling holes are chosen as the geometric parameters. The spatially averaged film-cooling effectiveness averaged over an area of 8 hole diameters in width and 30 hole diameters in streamwise length is used to evaluate the performance of film-cooling. The parameter of the lateral distance has the largest impact on the film cooling effectiveness compared to the others. On the other hand, the parameter of streamwise distance gives the least influence on the film cooling effectiveness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.577-586
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• 1999

Two problems with jet injection through the cylindrical film cooling hole are 1) penetration of jet into mainstream rather than covering the surface at high blowing rates and 2) nonuniformity of the film cooling effectiveness in the lateral direction. Compound angle injection is employed to reduce those two problems. Compound angle injection increases the film cooling effectiveness and spreads more widely. However, there is still lift off at high blowing rates. Shaped film cooling hole is a possible means to reduce those two problems. Film cooling with the shaped hole is investigated in this study experimentally. Film cooling hole used in present study is a shaped hole with conically enlarged exit and Inlet-to-exit area ratio is 2.55. Naphthalene sublimation method has been employed to study the local heat/mass transfer coefficient and film cooling effectiveness for compound injection angles and various blowing rates around the shaped film cooling hole. Enlarged hole exit area reduces the momentum of the jet at the hole exit and prevents the penetration of injected jet into the mainstream effectively. Hence, higher and more uniform film cooling effectiveness values are obtained even at relatively high blowing rates and the film cooling jet spreads more widely with the shaped film cooling hole. And the injected jet protects the surface effectively at low blowing rates and spreads more widely with the compound angle injections than the axial injection.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.59-64
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• 2014

The kidney vortex is the important factor adversely influencing film cooling effectiveness. In general, double jet film-cooling hole is designed to overcome the kidney vortex by generating anti-kidney vortices. In this study, the film cooling characteristics and the effectiveness of the double jet film cooling hole were numerically investigated with various area ratios of the first($A_1$) and second($A_2$) cooling hole($A_1/A_2$=0.8, 1.0, 1.25) and lateral ejection angle(${\alpha}$ = $30^{\circ}$, $45^{\circ}$, $60^{\circ}$) as the design parameters. The effects of lateral distance between the first and second row holes are investigated. Numerical study was performed by using ANSYS CFX with the shear stress transport(SST) turbulence model. The film cooling effectiveness and temperature distribution were graphically depicted with various flow and geometrical conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2590-2600
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• 1993

The present paper describes numerical predictions for the film cooling effectiveness from a row of hole at various injection ratios and injection alngles.Numerical calculations were performed to investigate film cooling effectiveness and the characteristics of flow and temperature distributions in the region near the downstream of injection hole including the region of adverse pressure gradient. The elliptic 3-dimensional governing equations with variable thermal properties were solved by SIMPLE algorithm. The results showed that the presence of adverse pressure gradient in the region near the downstream of injection hole induces large temperature gradient. At injection angle of $35^{\circ}$ the average film cooling effectiveness was increased as increased of injection ratio up to 1.0. At injection angle of $90^{\circ}$ however, the average film cooling effectiveness was decreased from injection ratio larger than 0.4.

• The KSFM Journal of Fluid Machinery
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• v.19 no.4
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• pp.13-18
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• 2016

The various film cooling hole shapes have been proposed for effective external cooling of gas turbine blade. In this study, the film cooling effectiveness by three different hole shapes (cylindrical hole, $15^{\circ}$ angle anti-vortex hole, 30-7-7 fan-shaped hole) were examined experimentally. Pressure Sensitive Paint (PSP) technique was used to measure the film cooling effectiveness. The coolant to mainstream density ratio was 1.0 and three blowing ratios of 0.5, 1.0, and 2.0 were considered. Results clearly showed that the effect of hole shape on the distribution of film cooling effectiveness. For the cylindrical hole case, the film cooling effectiveness decreased remarkably as the blowing ratio increased due to the jet lift off. Because of large hole exit area and low coolant momentum, the 30-7-7 fan-shaped hole case showed the highest film cooling effectiveness at all blowing ratio, followed by the anti-vortex hole case.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.655-663
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• 2013

Several studies of film cooling were accomplished with a secondary flow channel parallel to the main flow. In real turbine blades, however, the direction of the secondary flow channel is generally normal to the main flow. Thus, this study performs a numerical analysis to investigate the effects of the direction of secondary flow on the effectiveness of double-jet film cooling. The blowing ratio is 1 and 2, and the lateral injection angle is $22.5^{\circ}$. The parallel channel case creates a well-developed anti-kidney vortex with a blowing ratio of 1, and the laterally averaged film cooling effectiveness of the parallel channel is enhanced compared to the normal channel. The normal channel shows higher performance with a blowing ratio of 2. Both cases show high film cooling effectiveness. These phenomena can be attributed to a high blowing ratio and flow rate rather than an anti-kidney vortex.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.530-533
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• 2010

This paper presents numerical analysis and design optimization of various turbine blade cooling techniques with three-dimensional Reynolds-averaged Navier-Stokes(RANS) analysis. The fluid flow and heat transfer have been performed using ANSYS-CFX 11.0. A fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness with the radial basis neural network method. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. The impingement jet cooling has been performed to investigate heat transfer characteristic with geometry variables. Distance between jet nozzle exit and impingement plate, inclination of nozzle and aspect ratio of nozzle hole are considered as geometry variables. The area averaged Nusselt number is evaluated each geometry variables. A rotating rectangular channel with staggered array pin-fins has been investigated to increase heat transfer performance ad to decrease friction loss using KRG modeling. Two non-dimensional variables, the ratio of the eight diameter of the pin-fins and ratio of the spacing between the pin-fins to diameter of the pin-fins selected as design variables. A rotating rectangular channel with staggered dimples on opposite walls are formulated numerically to enhance heat transfer performance. The ratio of the dimple depth and dimple diameter are selected as geometry variables.

• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.60-66
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• 2015

Conjugate heat transfer analysis was performed to investigate the flow and cooling performance of the high pressure turbine nozzle of gas turbine engine. The CHT code was verified by comparison between CFD results and experimental results of C3X vane. The combination of k-${\omega}$ based SST turbulence model and transition model was used to solve the flow and thermal field of the fluid zone and the material property of CMSX-4 was applied to the solid zone. The turbine nozzle has two internal cooling channels and each channel has a complex cooling configurations, such as the film cooling, jet impingement, pedestal and rib turbulator. The parabolic temperature profile was given to the inlet condition of the nozzle to simulate the combustor exit condition. The flow characteristics were analyzed by comparing with uncooled nozzle vane. The Mach number around the vane increased due to the increase of coolant mass flow flowed in the main flow passage. The maximum cooling effectiveness (91 %) at the vane surface is located in the middle of pressure side which is effected by the film cooling and the rib turbulrator. The region of the minimum cooling effectiveness (44.8 %) was positioned at the leading edge. And the results show that the TBC layer increases the average cooling effectiveness up to 18 %.

• Journal of computational fluids engineering
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• v.16 no.4
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• pp.92-99
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• 2011

In order to protect the turbine blade from working fluid of high temperature, many cooling techniques such as internal convection cooling, film cooling, impinging jet cooling and thermal barrier coating have been developed. With all other things, film-cooling has been widely used as the important alternative. In the present work, numerical analysis has been performed to investigate and to compare the film-cooling performance of various film-cooling hole schemes such as cylindrical, crescent, louver, and dumbbell holes. To analyze the turbulent flow and the film-cooling mechanism, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been assessed in comparison with experimental data. The characteristics of fluid flow and the film-cooling performance for each shaped hole have been investigated and evaluated in terms of centerline, laterally averaged and spatially averaged film-cooling effectivenesses. Among the film cooling holes, the dumbbell shaped hole shows better film-cooling effectiveness than the other shaped holes. And the louver and cylindrical shaped hole show the worst film cooling performance, and concentrated flows on near the centerline only.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.470-483
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• 1990

Turbulent jet in a crossflow, issuing from a row of holes on a convex surface of 90 .deg. bend duct, is predicted by a 3-dimensional numerical method. The Cartesian coordinate system in adopted in upstream and downstream tangents and the cylindrical polar coordinate system in curved region. The Reynolds stresses and heat fluxes are obtained from a standard k-e model in the core region and van Driest model in the vicinity of the wall. The governing equations are discretized by a finite volume method and solutions are obtained by a locally elliptic calculation procedure. Pressure and convective terms are treated by SIMPLE algorithm and hybrid scheme respectively. A vortex initially induced by the injected jet has been built up due to the interaction with the secondary flow caused by pressure gradient and centrifugal force. The vortex structure has a strong influence on the wall cooling effectiveness. Another vortex like horseshoe is formed in the vicinity of the injection hole and its strength is getting weak as it moves downward.