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.

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.

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.

Numerical Evaluation of the Performance of the Sister–Shaped Single–Hole Schemes on Turbine Blade Leading Edge Film Cooling

2015 ◽  
Author(s):  
Siavash Khajehhasani ◽  
Bassam Jubran
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Numerical Evaluation ◽  
Leading Edge ◽  
Lateral Spread ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Hole ◽  
Shaped Hole ◽  
Lift Off

In the present study, a numerical evaluation of the performance of the sister-shaped single-hole (SSSH) schemes (downstream, upstream and up/downstream) on the leading edge of AGTB-B1 high pressure turbine blade cascade is carried out. Simulations are performed at three blowing ratios of 0.7, 1.1 and 1.5. Predicted results are compared to the single cylindrical hole and a 15° forward-diffused shaped hole. The realizable k-ε model combined with the standard wall function is used to model the flow field; wherein, the predicted pressure field was in a good agreement with the available experimental data. At the high blowing ratios of 1.1 and 1.5, a noticeable improvement in the film cooling effectiveness and the lateral spread of the cooling jet has been observed for the upstream and up/downstream SSSH schemes, in particular on the suction side. The downstream SSSH configuration provided almost similar film cooling effectiveness values to that of the forward diffused shaped hole for all blowing ratios on both the pressure and suction sides of the blade. Note that the obtained film cooling effectiveness for the downstream SSSH scheme at high blowing ratios was disappointing in comparison with other SSSH schemes where much higher film cooling effectiveness values were obtained. The mixing of the coolant with the high mainstream flow at the leading edge of the blade is considerably decreased for the upstream and up/downstream SSSH schemes and more adhered coolant to the blade’s surface is observed than with other configurations. Moreover, the jet lift-off is notably diminished for the upstream and up/downstream SSSH compared to other hole geometries.

Film Cooling From Novel Sister Shaped Single-Holes

2014 ◽  
Author(s):  
Siavash Khajehhasani ◽  
Bassam Jubran
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
Navier Stokes ◽  
The Novel ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Shaped Hole ◽  
Lift Off

A numerical investigation of the film cooling performance from novel sister shaped single-holes (SSSH) is presented in this paper and the obtained results are compared with a single cylindrical hole, a forward diffused shaped hole, as well as discrete sister holes. Three types of the novel sister shaped single-hole schemes namely downstream, upstream and up/downstream SSSH, are designed based on merging the discrete sister holes to the primary hole in order to reduce the jet lift-off effect and increase the lateral spreading of the coolant on the blade surface as well as a reduction in the amount of coolant in comparison with discrete sister holes. The simulations are performed using three-dimensional Reynolds-Averaged Navier Stokes analysis with the realizable k–ε model combined with the standard wall function. The upstream SSSH demonstrates similar film cooling performance to that of the forward diffused shaped hole for the low blowing ratio of 0.5. While it performs more efficiently at M = 1, where the centerline and laterally averaged effectiveness results improved by 70% and 17%, respectively. On the other hand, the downstream and up/downstream SSSH schemes show a considerable improvement in film cooling performance in terms of obtaining higher film cooling effectiveness and less jet lift-off effect as compared with the single cylindrical and forward diffused shaped holes for both blowing ratios of M = 0.5 and 1. For example, the laterally averaged effectiveness for the downstream SSSH configuration shows an improvement of approximately 57% and 110% on average as compared to the forward diffused shaped hole for blowing ratios of 0.5 and 1, respectively.

Turbine Vane Endwall Film Cooling From Cross-Row Configuration With Simulated Upstream Leakage Flow

2017 ◽  
Author(s):  
Nafiz H. K. Chowdhury ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Companion Paper ◽  
Leakage Flow ◽  
Blow Down ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Lift Off ◽  
Endwall Cooling

The performance of a full coverage film cooling configuration called cross-row (CR) configuration including upstream inlet leakage flow was studied by measuring the adiabatic film cooling effectiveness distribution using PSP technique. Experiments were conducted in a blow-down wind tunnel cascade facility at the isentropic exit Mach number of 0.5 corresponding to inlet Reynolds number of 3.8 × 105, based on axial chord length. A free-stream turbulence level was generated as high as 19% with a length scale of 1.7 cm at the inlet. The results are presented as two-dimensional adiabatic film cooling effectiveness distributions on the endwall surface with corresponding spanwise averaged distributions. The focus of this study is to investigate the effect of coolant-to-mainstream mass flow ratio (MFR) and density ratio (DR) on the proposed endwall cooling design. Initially, increased MFR for the endwall cooling and upstream leakage levels up the local adiabatic cooling effectiveness and yields relatively uniform coverage on the entire endwall. However, in either case, highest MFR does not provide any improvement as endwall cooling suffered from the jet lift-off and leakage coolant coverage restricted by the downstream near-wall flow field. Results also indicated a density ratio of 1.5 provides the best performance. Finally, a fair comparison is made with another design called axial-row (AR) configuration from a companion paper.

Experimental Investigation and Optimal Design on the Film Cooling Performance of Fan-Shaped Hole With Vortex Generator Fed by Crossflow

2021 ◽  
Author(s):  
Jie Wang ◽  
Chao Zhang ◽  
Xuebin Liu ◽  
Liming Song ◽  
Jun Li ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Vortex Generator ◽  
Optimized Design ◽  
Combined Model ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Shaped Hole

Abstract Aiming at investigating the effects of crossflow and vortex generator on film cooling characteristics of fan-shaped hole, the film cooling performance was measured experimentally by infrared camera. The blowing ratio is fixed at 0.5 and 1.5. The Reynolds number of the mainstream based on the hole diameter remains at 7000 and the inlet Reynolds number of crossflow is 40000. The experimental results show that the film cooling performance becomes better when the blowing ratio increases from 0.5 to 1.5 for each model, and the film cooling performance becomes worse under the influence of crossflow. When the blowing ratio is 1.5, the area-averaged film cooling effectiveness of the fan-shaped hole model with vortex generator decreases by 16.6% because of the influence of crossflow. The combined model always performs better compared with the model without vortex generator under all working conditions. When the blowing ratio becomes 1.5, under the influence of crossflow, the area-averaged film cooling effectiveness of the combined model could increase by 14.8%, compared with the model without vortex generator. To further improve the film cooling performance, the global optimization algorithm based on the Kriging method and the CFD technology are coupled to optimize the combined model under crossflow condition at the high blowing ratio, and the optimized design is verified by experiments. The experimental results show that the area-averaged film cooling effectiveness of the optimized design increases by 17.8% compared with the reference model.

Numerical Analysis on the Leading Edge Film Cooling of Bifurcation Holes for Gas Turbine Blade

2021 ◽  
Author(s):  
Zhonghao Tang ◽  
Gongnan Xie ◽  
Honglin Li ◽  
Wenjing Gao ◽  
Chunlong Tan ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Turbulence Models ◽  
Leading Edge ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Lift Off

Abstract Film cooling performance of the cylindrical film holes and the bifurcated film holes on the leading edge model of the turbine blade are investigated in this paper. The suitability of different turbulence models to predict local and average film cooling effectiveness is validated by comparing with available experimental results. Three rows of holes are arranged in a semi-cylindrical model to simulate the leading edge of the turbine blade. Four different film cooling structures (including a cylindrical film holes and other three different bifurcated film holes) and four different blowing ratios are studied in detail. The results show that the film jets lift off gradually in the leading edge area as the blowing ratio increases. And the trajectory of the film jets gradually deviate from the mainstream direction to the spanwise direction. The cylindrical film holes and vertical bifurcated film holes have better film cooling effectiveness at low blowing ratio while the other two transverse bifurcated film holes have better film cooling effectiveness at high blowing ratio. And the film cooling effectiveness of the transverse bifurcated film holes increase with the increasing the blowing ratio. Additionally, the advantage of transverse bifurcated holes in film cooling effectiveness is more obvious in the downstream region relative to the cylindrical holes. The Area-Average film cooling effectiveness of transverse bifurcated film holes is 38% higher than that of cylindrical holes when blowing ratio is 2.

Effects of Blowing Ratio on Multiple Shallow Angle Film Cooling Holes

2012 ◽  
Vol 225 ◽  
pp. 49-54 ◽  
Author(s):  
Kamil Abdullah ◽  
Ken Ichi Funazaki
Keyword(s):  
Temperature Field ◽  
Surface Temperature ◽  
Film Cooling ◽  
Cooling Effectiveness ◽  
Ir Camera ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hole Configuration ◽  
The Common ◽  
Film Cooling Holes

This paper presents the investigation on the effects of the blowing ratio of multiple shallow angle film cooling holes. Multiple film cooling holes having a shallow hole angle (θ = 20°), arranged to perform in-line hole configuration has been considered in the present study. The investigation focuses on the effects of high blowing ratio of the film cooling effectiveness which have been carried out at ReD= 3100 and BR = 2.0, 3.0 and 4.0. The experiments make use of the IR camera in capturing the surface temperature to determine the film cooling effectiveness. The contours of the film cooling effectiveness distribution together with plots on laterally average film cooling effectiveness along the x/D are presented. The discussions have been made with a support of the temperature field captured at x/D = 3, 13, 23, and 33. The results clearly show the benefit of the employment of shallow hole angle (θ = 20°) at high blowing ratio which is much more superior in comparison to the common hole configuration (θ = 35°).

Effectiveness of Normal and Angled Slot Cooling

2004 ◽  
Author(s):  
A. C. Smith ◽  
J. H. Hatchett ◽  
A. C. Nix ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Fluid Dynamic ◽  
Current Experiment ◽  
Cfd Simulations ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Mach Numbers ◽  
Lift Off

An experimental and numerical investigation was conducted to determine the film cooling effectiveness of a normal slot and angled slot under realistic engine Mach number conditions. Freestream Mach numbers of 0.65 and 1.3 were tested. For the normal slot, hot gas ingestion into the slot was observed at low blowing ratios (M &lt; 0.25). At high blowing ratios (M &gt; 0.6) the cooling film was observed to “lift off” from the surface. For the 30° angled slot, the data was found to collapse using the blowing ratio as a scaling parameter. Results from the current experiment were compared with the subsonic data previously published. For the angle slot, at supersonic freestream Mach number, the current experiment shows that at the same x/Ms, the film-cooling effectiveness increases by as much as 25% as compared to the subsonic case. The results of the experiment also show that at the same x/Ms, the film cooling effectiveness of the angle slot is considerably higher than the normal slot, at both subsonic and supersonic Mach numbers. The flow physics for the slot tests considered here are also described with computational fluid dynamic (CFD) simulations in the subsonic and supersonic regimes.

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