• 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.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.1 s.24
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• pp.117-124
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• 2006

Experiments on film cooling were performed with a small scale rocket engine homing liquid oxygen (LOx) and Jet A-1(jet engine fuel). Film coolants(Jet A-1 and water) were injected through the film cooling injector. Film cooled length and the outside wall temperature of the combustor were determined for chamber pressure, and the different geometries(injection angle) with the flow rates of film coolant. The loss of characteristic velocity due to film cooling was determined for the case of film cooling with water and Jet A-1. As the coolant flow increases, the outside wall temperatures decrease but the decrease in the outside wall temperatures reduced over the 8 percent film coolant flow rate. The efficiency of characteristic velocity was decreased with the Increase of the film coolant flow rate.

• 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.

• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.48-54
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• 2005

An experimental study was carried out to investigate the effect of film cooling in the lab-scale liquid rocket engine using liquid oxygen(LOx) and Jet A-1(Jet engine fuel) as propellants. Film coolants(Jet A-1 and water) was injected through the film cooling injector. The outside wall temperature of the combustor and film cooled length were determined for chamber pressure, mixture ratio, and the different geometries(injection angle) with the percent film coolant flow rate. The loss of characteristic velocity was determined for the case of film cooling with water and Jet A-1. As chamber pressure increased, the outside wall temperature increased in the nozzle but unchanged over the 9 percent film coolant flow rate for the combustion chamber used in this study. Characteristic velocity wasn't affected with the mixture ratio over the 9 percent film coolant flow rate.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.10-18
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• 2009

Numerical simulation has been performed in this study to investigate the capabilities of turbulence modeling schemes on estimating the film cooling at a referenced parallel wall jet-nozzle configuration. Also a additional simulation has been performed for film cooling under 2-dimensional axis symmetry conditions at a parallel wall jet-nozzle configuration. It was concluded that the best turbulence model is the standard $k-{\epsilon}$ model with enhanced wall functions. Also a additional simulation showed the film cooling characteristics that are resonable physically.

• 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.

• 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.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1121-1136
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• 2002

The flow characteristics of film coolant issuing into turbulent boundary layer developing on a convex surface have been investigated by means of flow visualization and three-dimensional velocity measurement. The Schlieren optical system with a spark light source was adopted to visualize the jet trajectory injected at 35° and 90° inclination angles. A five-hole directional pressure probe was used to measure three-dimensional mean velocity components at the injection angle of 35°. Flow visualization shows that at the 90° injection, the jet flow is greatly changed near the jet exit due to strong interaction with the crossflow. On the other hand, the balance between radial pressure gradient and centrifugal force plays an important role to govern the jet flow at the 35° injection. The velocity measurement shows that at a velocity ratio of 0.5, the curvature stabilizes downstream flow, which results in weakening of the bound vortex structure. However, the injectant flow is separated from the convex wall gradually, and the bound vortex maintains its structure far downstream at a velocity ratio of 1.98 with two pairs of counter rotating vortices.

• 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.