Investigations of improved cooling effectiveness for ramp film cooling with compound angle film cooling jets

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Krishna Anand Vasu Devan Nair Girija Kumari ◽  
Parammasivam Kanjikoil Mahali
Keyword(s):  
Film Cooling ◽  
Flat Surface ◽  
Flow Characteristics ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Content Type ◽  
Film Cooling Effectiveness ◽  
Ramp Test ◽  
Cooling Hole ◽  
Compound Angle

Purpose This paper aims to investigate the film cooling effectiveness (FCE) and mixing flow characteristics of the flat surface ramp model integrated with a compound angled film cooling jet. Design/methodology/approach Three-dimensional numerical simulation is performed on a flat surface ramp model with Reynolds Averaged Navier-Stokes approach using a finite volume solver. The tested model has a fixed ramp angle of 24° and a ramp width of two times the diameter of the film cooling hole. The coolant air is injected at 30° along the freestream direction. Three different film hole compound angles oriented to freestream direction at 0°, 90° and 180° were investigated for their performance on-ramp film cooling. The tested blowing ratios (BRs) are in the range of 0.9–2.0. Findings The film hole oriented at a compound angle of 180° has improved the area-averaged FCE on the ramp test surface by 86.74% at a mid-BR of 1.4% and 318.75% at higher BRs of 2.0. The 180° film hole compound angle has also produced higher local and spanwise averaged FCE on the ramp test surface. Originality/value According to the authors’ knowledge, this study is the first of its kind to investigate the ramp film cooling with a compound angle film cooling hole. The improved ramp model with a 180° film hole compound angle can be effectively applied for the end-wall surfaces of gas turbine film cooling.

scholarly journals Effect of Inlet Compound Angle of Backward Injection Film Cooling Hole

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 808
Author(s):  
Yoon Seong Jeong ◽  
Jun Su Park
Keyword(s):  
Numerical Analysis ◽  
Film Cooling ◽  
Flow Characteristics ◽  
Cooling Effectiveness ◽  
Combustion Gas ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Film Cooling Holes ◽  
Compound Angle

Backward injection film cooling holes were studied to improve film cooling effectiveness using simple cylindrical holes, and this principle was applied to an actual gas turbine. Although film cooling effectiveness was improved using a backward injection film cooling hole, the backward flow of combustion gas from the backward injection cooling hole was one of the major reasons for cracks in the hot components. To prevent cracks and backward flow in the backward injection film cooling hole, this study changed the inlet compound angle of the backward injection film cooling hole. Numerical analysis using CFX v. 17.0 was performed to calculate the flow characteristics and film cooling effectiveness of backward injection film cooling. Aa a result, the effect of the inlet compound angle of the backward injection film cooling hole was confirmed to prevent the backward flow, which increased upon increasing the inlet compound angle. This study shows that the backward flow and cracks in the backward injection film cooling hole can be prevented simply by changing the inlet compound angle.

Comparative analysis on the film cooling mechanisms of elliptical and cylindrical holes with 90° compound angle

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guohua Zhang ◽  
Gongnan Xie ◽  
Bengt Ake Sunden
Keyword(s):  
Film Cooling ◽  
Cross Sectional ◽  
Cooling Effectiveness ◽  
Content Type ◽  
Film Cooling Effectiveness ◽  
Cylindrical Model ◽  
Blowing Ratio ◽  
Elliptical Model ◽  
Lift Off ◽  
Compound Angle

Purpose In this study, numerical simulations are performed to compare the adiabatic film cooling effectiveness and reveal the difference of film cooling mechanisms of two models with the same geometries and cross-section areas of film holes’ exits at three typical blowing ratios (M = 0.5, 1 and 1.5). The two models are an elliptical model and a cylindrical model with 90° compound angle, respectively. Design/methodology/approach Three different cases are considered in this work and the baseline is the model with a cylindrical film hole. The same boundary conditions and a validated turbulence model (realizable k-ε) are adopted for all cases. Findings The results show that both the elliptical and cylindrical models with 90° compound angle can enhance the film cooling effectiveness compared with the baseline. However, the elliptical model performs well at lower blowing ratios and in the near region at each blowing ratio because of the wider width of the film hole’s exit. The cylindrical model with 90° compound angle provides better film cooling effectiveness in the further downstream area of the film hole at higher blowing ratio because of the less lift-off and better coolant coverage in the larger x/D region along the mainstream direction. Originality/value Overall, it can be concluded that although the elliptical and cylindrical models with 90° compound angle have identical hole exits, the different inlet direction and cross-sectional geometry affect the flow structures when the coolant enters, moves through and exits the hole and finally different film cooling results appear.

Experimental and Numerical Film Effectiveness Downstream a Row of Compound Angle Film Holes

2003 ◽  
Author(s):  
A. Khanicheh ◽  
M. E. Taslim
Keyword(s):  
High Temperature ◽  
Film Cooling ◽  
Computational Study ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Film Cooling Holes ◽  
Compound Angle

High component lifetimes of modern gas turbines can be achieved by cooling the airfoils effectively. Film cooling is commonly employed on the airfoils and other engine hot section surfaces in order to protect them from the high thermal stress fields created by exposure to combustion gases. Complex geometries as well as optimized cooling considerations often dictate the use of compound-angled film cooling hole. In the present experimental and computational study, the effects that two different compound angle film cooling hole injection configurations have on film cooling effectiveness are investigated. Film cooling effectiveness measurements have been made downstream of a single row of compound angle cylindrical holes with a diameter of 7.5 mm, and a single row of compound angle, diffuser-shaped holes with an inlet diameter of 7.5 mm. The cylindrical holes were inclined (α=25°) with respect to the coverage surface and were oriented perpendicular to the high-temperature airflow direction. The diffuser-shaped holes had a compound angle of 45 degrees with respect to the high temperature air flow direction and, similar to the cylindrical film holes, a 25-deg angle with the coverage surface. Both geometries were tested over a blowing ratio range of 0.7 to 4.0. Surface temperatures were measured along four longitudinal rows of thermocouples covering the downstream area between two adjacent holes. The results showed that the best overall protection over the widest range of blowing ratios was provided by the diffuser-shaped film cooling holes. Compared with the cylindrical hole results, the diffuser-shaped expansion holes produced higher film cooling effectiveness downstream of the film cooling holes, particularly at high blowing ratios. The increased cross sectional area at the shaped hole exit compared to that of the cylindrical hole lead to a reduction of the mean velocity, thus the reduction of the momentum flux of the jet exiting the hole. Therefore, the penetration of the jet into the main flow was reduced, resulting in an increased cooling effectiveness. A commercially available CFD software package was used to study film cooling effectiveness downstream of the row of holes. Comparisons between the experimentally measured and numerically calculated film effectiveness distributions showed that the computed results are in reasonable agreement with the measured results. Therefore, CFD can be considered as a viable tool to predict the cooling performance of different film cooling configurations in a parametric study. A more realistic turbulence model, possibly adopting a two-layer model that incorporates boundary layer anisotropy, in the computational study may improve the predicted results.

Effect of Upstream Step on Flat Plate Film-Cooling Effectiveness Using PSP

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Joshua Grizzle ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Axial Angle ◽  
Step Effect ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
State Pressure

The effect of a step positioned upstream of a row of film-cooling holes on the film-cooling effectiveness is studied systematically using the steady state pressure sensitive paint technique. The upstream step effect is studied on four separate hole geometries: simple angled (axial angle of 30 deg) and compound angled (axial angle of 30 deg and compound angle of 45 deg) and cylindrical and fan-shaped film-cooling holes. Each plate considered has seven holes, each hole 4 mm in diameter. The plates with cylindrical holes have a spacing of 3 diameters (12 mm) between the centers of two consecutive holes while the fan-shaped holes have a spacing of 3.75 diameters (15 mm). Three different step heights (12.5%d, 25%d, and 37.5%d) are studied. The effect of the width of the step is also studied; the distance of the step upstream of the hole and the positioning of the step downstream of the film-cooling hole. Four separate blowing ratios are reported for all tests: M=0.3, M=0.6, M=1.0, and M=1.5. All studies have been conducted with a mainstream of 25 m/s velocity at an ambient temperature of 22°C. Results indicate an increase in film-cooling effectiveness in the region near the hole due to the upstream step for all the plates considered. This increase due to the step is found to be most significant in the case of compound angled cylindrical holes and least significant in the case of simple angled fan-shaped holes.

scholarly journals Film Cooling Effectiveness and Heat/Mass Transfer Coefficient Measurement Around a Conical-Shaped Hole With a Compound Angle Injection

1999 ◽  
Author(s):  
H. H. Cho ◽  
D. H. Rhee ◽  
B. G. Kim
Keyword(s):  
Mass Transfer ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Hole Geometry ◽  
Compound Angle

The present study investigates local film cooling effectiveness values and heat/mass transfer coefficients around a conical-shaped film cooling hole with compound angle orientations. Three types of film cooling hole geometry are compared in this study; one is cylindrical hole geometry with constant cross section and the others are shaped hole geometries with conically-enlarged hole exits. The shaped holes have cylindrical passage sections at the hole inlet region to obtain a certain pressure drop through the holes. One shaped hole expands 4° in all directions from the middle of hole to the exit. The other shaped hole has the tilted center-line by 4° between the conical and metering holes and is enlarged by 8° to downstream side. The hole area ratios of the exit to the inlet are 2.55 and 2.48, respectively. The compound-angled film cooling jet is ejected through the single holes, which are inclined at 30° to the surface based on the metering hole and are rotatable in lateral direction from 0° to 90°. The blowing rates are changed from 0.5 to 2.0. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients and local adiabatic/impermeable wall film cooling effectiveness around the injection hole. The results indicate that the injected jet protects the surface effectively with low blowing rates and spreads more widely with the compound angle injections than the axial injection. For the shaped hole enlarged by 4° in all directions, the penetration of jet is reduced and higher cooling performance is obtained even at relatively high blowing rates because the increased hole exit area reduces hole exit velocity. Furthermore, the film cooling effectiveness is fairly uniform near the hole due to the wide lateral spreading of coolant with the expanded cooling hole exit.

Enhancement of Film Cooling Effectiveness Using Upstream Ramp

2012 ◽  
Author(s):  
Paresh Halder ◽  
Abdus Samad
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Surface Heat Flux ◽  
High Performance ◽  
Flat Surface ◽  
Surface Heat ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole

Film cooling is widely used in high-performance gas turbines to reduce surface heat flux and placing a ramp at the upstream of film cooling hole improves film cooling effectiveness. In this work, RANS based numerical simulations were carried out for a flat surface having two rows of injection holes and an upstream ramp. The parameters which were considered in this computation were different blowing ratios (M = 0.6, 1.0 and 1.6) and upstream ramp angles (α = 14° to 24°). Surface effectiveness was increased with increase in angle of upstream ramp and blowing ratio but further increasing these parameters decreased the effectiveness. The downstream of the second row hole effectiveness was more than that of the upstream hole for high blowing ratios in case of without ramp.

Numerical Simulation of Hole Shapes Effect on Film Cooling Effectiveness and Aerodynamics Loss over Flat Plate

2012 ◽  
Vol 614-615 ◽  
pp. 216-221 ◽  
Author(s):  
Ruo Ling Dong ◽  
Hong Hui Shi ◽  
Wei Chen ◽  
Xiao Dong Zhang
Keyword(s):  
Numerical Simulation ◽  
Flat Plate ◽  
Film Cooling ◽  
Flow Characteristics ◽  
Low Loss ◽  
Simple Method ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Compound Angle

A numerical simulation was conducted to investigate the flow characteristics, film cooling effectiveness and aerodynamics loss over flat plate. Three types of shaped holes, separately, cylindrical hole, laterally diffused hole and converging-expanding hole were studied with 35°inclination angle and 0°compound angle. The inlet diameter of the hole in this paper is 12.7 mm, giving a L/D ratio of 3.5 at a mainstream velocity of 20m/s, turbulence intensity 2%, and temperature ratio to cooling jet 1.97, with blowing ratio M equaling to 0.5. Realizable k-ε turbulence model, standard wall function and SIMPLE method for pressure-velocity coupling were used .The coefficients η and ξ were calculated to analyze cooling effectiveness and aerodynamics loss. Both high film cooling effectiveness and low loss are found with laterally diffused hole. While optimizing the hole geometry in film cooling, cooling effectiveness and aerodynamics loss should been considered simultaneously.

Effect of Upstream Step on Flat Plate Film Cooling Effectiveness Using PSP

2008 ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Joshua Grizzle ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Axial Angle ◽  
Step Effect ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
State Pressure

The effect of a step positioned upstream of a row of film cooling holes on the film cooling effectiveness is studied systematically using the steady state Pressure Sensitive Paint (PSP) technique. The upstream step effect is studied on four separate hole geometries: simple angled (axial angle 30°) and compound angled (axial angle 30°, compound angle 45°) cylindrical and fan-shaped film cooling holes. Each plate considered has 7 holes, each hole 4mm in diameter. The plates with cylindrical holes have a spacing of 3 diameters (12mm) between the centers of two consecutive holes, while the fan-shaped holes have a spacing of 3.75d (15mm). Three different step heights (12.5%d, 25%d and 37.5%d) are studied. Also studied is the effect of the width of the step; the distance of the step upstream of the hole and the positioning of the step downstream of the film-cooling hole. Four separate blowing ratios are reported for all tests: M = 0.3, M = 0.6, M = 1.0 and M = 1.5. All studies have been conducted with a mainstream of 25m/s velocity at an ambient temperature of 22C. Results indicate an increase in film-cooling effectiveness in the region near the hole due to the upstream step for all the plates considered. This increase due to the step is found to be most significant in the case of compound angled cylindrical holes and least significant in the case of simple angled fan-shaped holes.

Numerical Study on Film-Cooling Effectiveness for Various Film-Cooling Hole Schemes

2011 ◽  
Author(s):  
Sun-min Kim ◽  
Ki-Don Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Influential Parameters

Film-cooling has been widely used as the important alternative to protect the turbine blade. Since the film-cooling hole geometry is one of the most influential parameters for film-cooling performance, various film-cooling hole schemes have been developed to increase cooling performance for the past few decades. 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 fan-shaped, crescent, louver, and dumbbell holes. For analyzes of the turbulent flow and film-cooling, three-dimensional Reynolds-averaged Navier-Stokes analysis has been performed with shear stress transport turbulence model. The validation of numerical results has been performed in comparison with experimental data. The flow characteristics and film-cooling performance for each hole shape have been investigated and evaluated in terms of local- and averaged film-cooling effectivenesses.

Sign in / Sign up

Export Citation Format

Share Document