New Designs of Novel Holes Based on Cylindrical Configurations for Improving Film Cooling Effectiveness

2018 ◽  
Author(s):  
Rui Zhu ◽  
Gongnan Xie ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Cylindrical Hole ◽  
Two Stage ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Vortex Pairs ◽  
Shaped Hole ◽  
Lift Off

In modern gas turbines, film cooling technology is the most common and efficient way to provide thermal protection for hot parts. To improve film cooling effectiveness, different kinds of shaped holes have been designed, but most of them are complicated and difficult to machine. In this study, four cases of novel film cooling hole design, all based on cylindrical holes, are numerically studied. One is a single, two-stage cylindrical hole, whose downstreamhalf-length has a diameter D while the upstreamhalf-length has a diameter D/2. A second has a cylindrical primary hole with two smaller secondary holes located symmetrically about the centerline of the primary hole and downstream of the primary hole. The three holes of this second design are then combined to make a single shaped hole, constituting a third case, called the tri-circular shaped hole. The entry part of the third case is replaced by a cylindrical hole with a diameter of half the primary hole diameter, making a fourth case called the two-stage tri-circular shaped hole. Film cooling effectiveness and surrounding thermal and flow fields are numerically investigated for all four cases using various blowing ratios. It is shown from the simulation that the two-stage cylindrical hole cannot improve film cooling effectiveness. The primary hole with two secondary holes can enhance film cooling performance by creating anti-kidney vortex pairs, which will weaken jet lift-off, caused by the kidney vortex pairs, from the primary hole. The tri-circular shaped hole will provide better film cooling effectiveness near the hole area, and is not sensitive to blowing ratio. The two-stage structure for tri-circular shaped hole provides better film coverage because it changes the flow structure inside the channel and decreases jet penetration.

Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1998 ◽  
Vol 120 (3) ◽  
pp. 549-556 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Shaped Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated include a cylindrical hole and two holes with a diffuser-shaped exit portion (i.e., a fan-shaped and a laid-back fan-shaped hole). The flow conditions considered are the crossflow Mach number at the hole entrance side (up to 0.6), the crossflow Mach number at the hole exit side (up to 1.2), and the blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system, which provides a two-dimensional distribution of the film-cooling effectiveness in the near field of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fan-shaped hole provides a better lateral spreading of the ejected coolant than the fan-shaped hole, which leads to higher laterally averaged film-cooling effectiveness. Coolant passage cross-flow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

scholarly journals Adiabatic Wall Effectiveness Measurements of Film-Cooling Holes With Expanded Exits

1997 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Thermal Protection ◽  
Lateral Spreading ◽  
Cylindrical Hole ◽  
Adiabatic Wall ◽  
Camera System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

This paper presents detailed measurements of the film-cooling effectiveness for three single, scaled-up film-cooling hole geometries. The hole geometries investigated include a cylindrical hole and two holes with a diffuser shaped exit portion (i.e. a fanshaped and a laidback fanshaped hole). The flow conditions considered are the crossflow Mach number at the hole entrance side (up to 0.6), the crossflow Mach number at the hole exit side (up to 1.2), and the blowing ratio (up to 2). The coolant-to-mainflow temperature ratio is kept constant at 0.54. The measurements are performed by means of an infrared camera system which provides a two-dimensional distribution of the film-cooling effectiveness in the nearfield of the cooling hole down to x/D = 10. As compared to the cylindrical hole, both expanded holes show significantly improved thermal protection of the surface downstream of the ejection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the ejected coolant than the fanshaped hole which leads to higher laterally averaged film-cooling effectiveness. Coolant passage crossflow Mach number and orientation strongly affect the flowfield of the jet being ejected from the hole and, therefore, have an important impact on film-cooling performance.

A Numerical Investigation on the Performance of Novel Sister Shaped Single-Hole Configurations for Film Cooling Flow

2014 ◽  
Author(s):  
Siavash Khajehhasani ◽  
Bassam A. Jubran
Keyword(s):  
Film Cooling ◽  
The Novel ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Blowing Ratio ◽  
Single Hole ◽  
Attached Flow ◽  
Shaped Hole ◽  
Lift Off

The film cooling performance using novel sister shaped single-hole (SSSH) schemes are numerically investigated in the present study. The downstream, upstream and up/downstream SSSH configurations are formed by merging the discrete sister holes to the primary injection hole through a series of specific orientations. The obtained results are compared with a conventional cylindrical hole and a forward diffused shaped hole. The RANS simulations are performed using the realizable k-ε model with the standard wall function. Results are presented for low and high blowing ratios of 0.25 and 1.5, respectively. The film cooling effectiveness is notably increased for the novel shaped holes, particularly at the high blowing ratio of 1.5. Furthermore, a considerable decrease in the jet lift-off has been achieved for the proposed film hole geometries, wherein fully attached flow to the wall surface is observed for the upstream and up/downstream SSSH schemes.

Enhanced Film Cooling Effectiveness by Integration of Horn-Shaped and Cylindrical Holes

2017 ◽  
Author(s):  
Rui Zhu ◽  
Gongnan Xie ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Turbine Blades ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Transverse Tensile ◽  
First Case ◽  
Cylindrical Holes ◽  
Shaped Hole

In search of improved cooling of gas turbine blades, the thermal performances of two different film cooling hole geometries (horn-shaped and cylindrical) are investigated in this numerical study. The horn-shaped hole is designed from a cylindrical hole by expanding the hole in the transverse direction to double the hole size at the exit. The two hole shapes are evaluated singly and in tandem. The tandem geometry assumes three configurations made by locating the cylindrical hole at three different positions relative to the horn-shaped hole such that their two axes remain parallel to one another. One has the cylindrical hole downstream from the center of the horn-shaped hole, a second has the cylindrical hole to the left of (as seen by the flow emerging from the horn-shaped hole) and at the same streamwise location as the horn-shaped hole (θ = 90°) and the third has an intermediate geometry between those two geometries (downstream and to the left of the horn-shaped hole - θ = 45°). It is shown from the simulation results that the cooling effectiveness values for the θ = 45° and 90° cases are much better than that for θ = 0° (the first case), and the configuration with θ = 45° exhibits the best cooling performance of the three tandem arrangements. These improvements are attributed to the interaction of vortices from the two different holes, which weakens the counter-rotating vortex pairs inherent to film cooling jet to freestream interaction, counteracts with the lift forces, enhances transverse tensile forces and, thus, enlarges the film coverage zone by widening the flow attachment region. Overall, this research reveals that integration of horn-shaped and cylindrical holes provides much better film cooling effectiveness than cases where two cylindrical film cooling holes are applied with the same tandem configuration.

Experimental Investigation on the Flat-Plate Film Cooling Enhancement Using the Vortex Generator Downstream for the Cylindrical Hole and Fan-Shaped Hole Configurations

2019 ◽  
Author(s):  
Chao Zhang ◽  
Jie Wang ◽  
Xin Luo ◽  
Liming Song ◽  
Jun Li ◽  
...  
Keyword(s):  
Film Cooling ◽  
Vortex Generator ◽  
Cylindrical Hole ◽  
Combined Model ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Shaped Hole ◽  
Hole Model

Abstract In our experiments, the film cooling performance of the configurations combined the different hole with the vortex generator was investigated experimentally, measured by the infrared camera. Four different configurations were studied at the blowing ratio varying at M = 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. In all cases, the Reynold number of the mainstream based on the hole diameter remained at Re = 8000, and the density ratio kept at DR = 1.7. Experimental results show that for the two models combining the cylindrical hole and fan-shaped hole with the vortex generator respectively, the film cooling performance becomes better when the blowing ratio increases from M = 0.5 to M = 2.0, and then decreases when the blowing ratio increases from M = 2.0 to M = 3.0. The model combining the fan-shaped hole with the vortex generator performs the best among the four models at each blowing ratio. Its film attachment holds the most extensive lateral distribution and its overall film cooling effectiveness could keep at a high level at a wide range of blowing ratios from M = 1.0 to M = 3.0. The combined model of the fan-shaped hole could improve the area-averaged film effectiveness at most 25.5% than that of the single hole model at M = 2.0. Moreover, the combined model of the cylindrical hole could improve the area-averaged film cooling effectiveness at most 431% than that of the single cylindrical hole model at M = 3.0.

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.

Film Cooling From Circular and Elliptical Exit Shaped Holes With Sister Hole Influence

2013 ◽  
Author(s):  
Siavash Khajehhasani ◽  
B. A. Jubran
Keyword(s):  
Film Cooling ◽  
Experimental Results ◽  
Considerable Decrease ◽  
Cylindrical Pipe ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Common ◽  
Shaped Hole ◽  
Lift Off ◽  
Inclined Angle

In traditional film cooling configuration, coolant is injected through a cylindrical pipe with an inclined angle (0<α<90), which results in an elliptical exit shaped hole (EESH) at the blade surface. The present study makes use of an elliptical injection coolant pipe that leads to a circular exit shaped hole (CESH). The film cooling effectiveness and the associated flow for both cases of circular and elliptical shaped holes are numerically investigated. A comparison between the predicted results and the available experimental results from the literature for blowing ratios of M = 0.5 and 1, clearly indicated a better agreement with the experimental results when the realizable k-ε model was used. Further, the results indicate that the circular exit shaped hole improves the centerline and laterally averaged adiabatic effectiveness, particularly, at a higher bowing ratio of 1. The analysis of the vortex generation downstream of the jet for both exit shaped holes, shows a considerable decrease in the jet lift-off where the coolant flow tends to adhere more to the surface and hence, provides a better film cooling protection for the circular exit shaped hole, in comparison with the common elliptical exit shaped hole. The influence of sister holes on film cooling performance tends to be more effective with circular exit shaped hole than that with elliptical exit shaped hole.

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.

The NEKOMIMI Cooling Technology: Cooling Holes With Ears for High-Efficient Film Cooling

2011 ◽  
Author(s):  
Karsten Kusterer ◽  
Anas Elyas ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Experimental Investigations ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
High Efficient ◽  
Cylindrical Holes ◽  
Cooling Technology ◽  
Lift Off ◽  
Cooling Air

Further improvement of the thermal efficiency of modern gas turbines can be achieved by a further reduction of the cooling air amount. Therefore, it is necessary to increase the cooling effectiveness, so that the available cooling air fulfils the cooling task even if the amount has been reduced. Due to experimental and numerical efforts, it is well understood today that aerodynamic mixing processes are enhanced by counter-rotating vortices (CRV) in the cooling jets and lead to jet lift-off effects. Thus, the film-cooling effectiveness is reduced soon behind the cooling air ejection through the holes. Due to that basic understanding, different technologies for improving film cooling have been developed. Some of them focus on establishing anti-counter-rotating vortices (ACRV) inside the cooling jet that prevent the hot gas from flowing underneath the jet and, thus, avoid the lift-off effect. One of these technologies is the double-jet film cooling (DJFC), invented by the authors, where the special arrangement of two cylindrical holes lead to a cooling jet with such an anti-vortex system. However, beside the advantage that the holes are simple cylindrical holes, one disadvantage is that appropriate supply with cooling air for both holes is sometimes difficult to be established in real configurations. Thus, the authors have followed the idea to transfer the original double-jet film cooling principle to a special configuration with merged holes. Thus, in that case only one air supply is necessary but the anti-vortex effect has been preserved. The derived cooling technology has been named NEKOMIMI technology. The paper explains the principle of that technology. Results from experimental investigations including film cooling effectiveness measurements for the new technology are presented. The results are compared to conventional cooling hole configurations showing the tremendous positive effect in reaching highest film cooling effectiveness for the new configuration at M = 1.5 and partly for M = 1. Numerical investigations for the M = 1.5 case indicate that the existence of the ACRV is the likely reason for the enhanced cooling performance of the new configuration.

Film Cooling Effectiveness Comparison Between Shaped- and Double Jet Film Cooling Holes in a Row Arrangement

2010 ◽  
Author(s):  
Karsten Kusterer ◽  
Anas Elyas ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Experimental Comparison ◽  
Comparison Study ◽  
Surface Cooling ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Shaped Hole ◽  
Cooling Air ◽  
Cooling Technique

The improvement of the thermal efficiency of modern gas turbines can be achieved by reducing the needed cooling air amount. Consequently it is required to increase the cooling efficiency of applied cooling technologies. Streamwise ejection from a cylindrical hole causes kidney vortices which transport hot gas underneath the cooling jet and leads the cooling jet to lift off from the surface. Cooling performance is highly increased by using the shaped hole technique, which weakens the kidney vortex structure. However the formation of secondary flows can not completely be avoided by using shaped holes instead of cylindrical holes. Another promising film cooling technology is the double-jet film cooling, which prevents the cooling jet from lifting off the surface and raises the lateral spreading of the cooling air by generating an anti kidney vortex. This paper presents a comparison of the film cooling effectiveness between the shaped film cooling technique and the novel double jet film cooling technique for the high blowing ratios M = 1, M = 1.5 and M = 2. Various geometries of fan-shaped holes with lateral expansion angles of 10°, 14° and 18° are used for the comparison study. It can be shown that the shaped hole row arrangement provides higher cooling values in a slight region near to the hole exits, while the double jet film cooling technique shows a obvious cooling advantage in the further downstream area for high blowing ratios. Furthermore recent results of an on-going experimental comparison study between the double jet, trench and cylindrical technique are presented, which proves the advantage capability of the double jet film cooling.

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