The Effect of an Upstream Dune-Shaped Shells on Forward and Backward Injection Hole Film Cooling

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Fatima Ben Ali Kouchih ◽  
Khadidja Boualem ◽  
Mustapha Grine ◽  
Abbes Azzi
Keyword(s):  
Film Cooling ◽  
Transport Model ◽  
Weighted Average ◽  
Turbulence Models ◽  
Injection Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Barchan Dune ◽  
Shear Stress Transport Model ◽  
Cooling Design

Abstract This article presents the numerical results of a new film cooling design that combines the backward injection hole with Barchan-dune-shaped shells (BH-BDS).The performance of this novel design in improving the film cooling effectiveness is compared to other configurations, forward injection hole (FH), backward injection hole (BH), and the configuration that combines the forward injection with Barchan-dune-shaped shells (FH-BDS). Three blowing ratios are considered in this article, M = 0.5, 1.0, and 1.5. The air coolant was injected through holes inclined at 35 and 155 deg for forward and backward cases, respectively. The lateral-averaged film cooling effectiveness and the distribution of adiabatic film cooling efficiency are studied using commercial software ansys-cfx. Three turbulence models, including the k–ω shear stress transport model, standard k–ε, and renormalization group theory (RNG) k–ε are examined in this investigation. The RNG k–ε model is adopted for the present simulation. The main result of this study reveals that the presence of upstream dune-shaped shells with backward hole yield a better film cooling effectiveness especially at higher blowing ratios (M ≥ 1). At M = 1.5, the FH-BDS and BH-BS cases provide an improvement in the area weighted average film cooling approximately about 24.79% and 10.56%, respectively. The BH-BDS design reduces the pressure loss as compared to BH.

A Parametric Numerical Study of the Effects of Freestream Turbulence Intensity and Length Scale on Anti-Vortex Film Cooling Design at High Blowing Ratio

2013 ◽  
Author(s):  
Timothy W. Repko ◽  
Andrew C. Nix ◽  
James D. Heidmann
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Numerical Study ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Cooling Effectiveness ◽  
Length Scales ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Design

An advanced, high-effectiveness film-cooling design, the anti-vortex hole (AVH) has been investigated by several research groups and shown to mitigate or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low freestream turbulence levels. [1, 2] The effects of increased turbulence on the AVH geometry were previously investigated and presented by researchers at West Virginia University (WVU), in collaboration with NASA, in a preliminary CFD study [3] on the film effectiveness and net heat flux reduction (NHFR) at high blowing ratio and elevated freestream turbulence levels for the adjacent AVH. The current paper presents the results of an extended numerical parametric study, which attempts to separate the effects of turbulence intensity and length-scale on film cooling effectiveness of the AVH. In the extended study, higher freestream turbulence intensity and larger scale cases were investigated with turbulence intensities of 5, 10 and 20% and length scales based on cooling hole diameter of Λx/dm = 1, 3 and 6. Increasing turbulence intensity was shown to increase the centerline, span-averaged and area-averaged adiabatic film cooling effectiveness. Larger turbulent length scales were shown to have little to no effect on the centerline, span-averaged and area-averaged adiabatic film-cooling effectiveness at lower turbulence levels, but slightly increased effect at the highest turbulence levels investigated.

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.

Film Cooling Effectiveness for Short Film Cooling Holes Fed by a Narrow Plenum

1999 ◽  
Vol 122 (3) ◽  
pp. 553-557 ◽  
Author(s):  
C. A. Hale ◽  
M. W. Plesniak ◽  
S. Ramadhyani
Keyword(s):  
Film Cooling ◽  
Short Film ◽  
Injection Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Hole Geometry ◽  
Thin Walled ◽  
Film Cooling Holes

The adiabatic, steady-state liquid crystal technique was used to measure surface adiabatic film cooling effectiveness values in the near-hole region X/D<10. A parametric study was conducted for a single row of short holes L/D⩽3 fed by a narrow plenum H/D=1. Film cooling effectiveness values are presented and compared for various L/D ratios (0.66 to 3.0), three different blowing ratios (0.5, 1.0, and 1.5), two different plenum feed configurations (co-flow and counterflow), and two different injection angles (35 and 90 deg). Injection hole geometry and plenum feed direction were found to affect short hole film cooling performance significantly. Under certain conditions, similar or improved coverage was achieved with 90 deg holes compared with 35 deg holes. This result has important implications for manufacturing of thin-walled film-cooled blades or vanes. [S0889-504X(00)00603-6]

Comparison of Four Different Two-Equation Models of Turbulence in Predicting Film Cooling Performance

2006 ◽  
Author(s):  
Jawad S. Hassan ◽  
Savas Yavuzkurt
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Turbulence Models ◽  
Accurate Solution ◽  
Diameter Ratio ◽  
Lateral Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Blowing Ratio

The capabilities of four two-equation turbulence models in predicting film cooling effectiveness were investigated and their limitations as well as relative performance are presented. The four turbulence models are the standard, RNG, and realizable k-ε models as well as the standard k-ω model all found in the FLUENT CFD code. In all four models, the enhanced wall treatment has been used to resolve the flow near solid boundaries. A systematic approach has been followed in the computational setup to insure grid-independence and accurate solution that reflects the true capabilities of the turbulence models. Exact geometrical and flow-field replicas of an experimental study on discrete-jet film cooling were generated and used in FLUENT. A pitch-to-diameter ratio of 3.04, injection length-to-diameter ratio of 4.6 and density ratios of 0.92 and 0.97 were some of the parameters used in the film cooling analysis. Furthermore, the study covered two levels of blowing ratio (M = 0.5 and 1.5) at an environment of low free-stream turbulence intensity (Tu = 0.1%). The standard k-ε model had the most consistent performance among all considered turbulence models and the best centerline film cooling effectiveness predictions with the results deviating from experimental data by only ±10% and about 20–60% for the low (M = 0.5) and high (M = 1.5) blowing ratio cases, respectively. However, centerline side-view and surface top-view contours of non-dimensional temperature for the standard k-ε cases revealed that the good results for film cooling effectiveness η compared to the experimental data were due to a combination of an over-prediction of jet penetration in the normal direction with an under-prediction of jet spread in the lateral direction. The standard k-ω model completely failed to produce any results that were meaningful with under-predictions of η that ranged between 80 and 85% for the low blowing ratio case and over-predictions of about 200% for the high blowing ratio case. Even though the RNG and realizable models showed to have better predicted the jet spread in the lateral direction compared to the standard k-ε model, there were some aspects of the flow, such as levels of turbulence generated by cross-flow and jet interaction, that were not realistic resulting in errors in the η prediction that ranged from −10% to +80% for the M = 0.5 case and from −80% to +70% for the M = 1.5 case. As a result of this study at this point it was concluded that the standard k-ε model have the most promising potential among the two-equation models considered. It was chosen as the best candidate for further improvement for the simulation of film cooling flows.

Evaluation of Two-Equation Models of Turbulence in Predicting Film Cooling Performance Under High Free Stream Turbulence

2007 ◽  
Author(s):  
Savas Yavuzkurt ◽  
Jawad S. Hassan
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Turbulence Models ◽  
Accurate Solution ◽  
Diameter Ratio ◽  
Tube Length ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Density Ratios

The capabilities of four two-equation turbulence models in predicting film cooling effectiveness under high free stream turbulence (FST) intensity (Tu = 10%) were investigated and their performance are presented and discussed. The four turbulence models are: the standard k-ε, RNG, and realizable k-ε models as well as the standard k-ω model all four found in the FLUENT CFD code. In all models, the enhanced wall treatment has been used to resolve the flow near solid boundaries. A systematic approach has been followed in the computational setup to insure grid-independence and accurate solution that reflects the true capabilities of these models. Exact geometrical and flow-field replicas of an experimental study on discrete hole film cooling were generated and used in FLUENT. A pitch-to-diameter ratio of 3.04, injection tube length-to-diameter ratio of 4.6 and density ratios of 0.92 and 0.97 were some of the parameters used in the film cooling analysis. The study covered two levels of blowing ratios (M = 0.5 and 1.5) at an environment of what is defined as high initial free-stream turbulence intensity (Tu = 10%). Performance of these models under a very low initial FST were presented in a paper by the authors in Turbo Expo 2006. In that case, the standard k-ε model had the most consistent performance among all considered turbulence models and the best centerline film cooling effectiveness predictions under very low FST. However, after the addition of high FST in the free-stream, even the standard k-ε model started to deviate greatly from the experimental data (up to 200% over-prediction) under high blowing ratios (M = 1.5). The model which performed the best under high FST but low blowing ratios (M = 0.5) is still the standard k-ε model. In all cases only standard k-ε model results match the trends of data for both cases. It can be said that under high FST with high M all the models do not do a good job of predicting the data. It was concluded that these deviations resulted from the effects of both high FST and high M. Under high M, near the injection holes deviations could result from the limitations of Boussinesq hypothesis relating the direction of Reynolds stress to the mean strain rate. Also, it seems like all models have trouble including the effects of high FST by not being able to take into account high levels of diffusion of turbulence from the free stream. However, standard k-ε model still looks like the best candidate for further improvement with the addition of new diffusion model for TKE under high FST.

A Numerical and Experimental Investigation of the Slot Film-Cooling Jet With Various Angles

2005 ◽  
Vol 127 (3) ◽  
pp. 635-645 ◽  
Author(s):  
Rongguang Jia ◽  
Bengt Sundén ◽  
Petre Miron ◽  
Bruno Léger
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Cross Flow ◽  
Turbulence Models ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Recirculation Bubble ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Present Solution

Numerical simulations coupled with laser Doppler velocimetry (LDV) experiments were carried out to investigate a slot jet issued into a cross flow, which is relevant in the film cooling of gas turbine combustors. The film-cooling fluid injection from slots or holes into a cross flow produces highly complicated flow fields. In this paper, the time-averaged Navier-Stokes equations were solved on a collocated body-fitted grid system with the shear stress transport k−ω, V2F k−ϵ, and stress-ω turbulence models. The fluid flow and turbulent Reynolds stress fields were compared to the LDV experiments for three jet angles, namely, 30, 60, and 90 deg, and the jet blowing ratio is ranging from 2 to 9. Good agreement was obtained. Therefore, the present solution procedure was also adopted to calculations of 15 and 40 deg jets. In addition, the temperature fields were computed with a simple eddy diffusivity model to obtain the film-cooling effectiveness, which, in turn, was used for evaluation of the various jet cross-flow arrangements. The results show that a recirculation bubble downstream of the jet exists for jet angles larger than 40 deg, but it vanishes when the angle is <30deg, which is in good accordance with the experiments. The blowing ratio has a large effect on the size of the recirculation bubble and, consequently, on the film cooling effectiveness. In addition, the influence of boundary conditions for the jet and cross flow are also addressed in the paper.

The Effect of High Freestream Turbulence on Film Cooling Effectiveness

1994 ◽  
Author(s):  
Jeffrey P. Bons ◽  
Charles D. MacArthur ◽  
Richard B. Rivir
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Plate Boundary ◽  
Constant Density ◽  
Freestream Turbulence ◽  
Injection Hole ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row

This study investigated the adiabatic wall cooling effectiveness of a single row of film cooling boles injecting into a turbulent flat plate boundary layer below a turbulent, zero pressure gradient freestream. Levels of freestream turbulence (Tu) up to 17.4% were generated using a method which simulates conditions at a gas turbine combustor exit. Film cooling was injected from a single row of five 35 degree slant-hole injectors (length/diameter = 3.5. pitch/diameter = 3.0) at blowing ratios from 0.55 to 1.85 and at a nearly constant density ratio (coolant density/freestream density) of 0.95. Film cooling effectiveness data is presented for Tu levels ranging from 0.9% to 17% at a constant freestream Reynolds number based on injection hole diameter of 19000. Results show that elevated levels of freestream turbulence reduce film cooling effectiveness by up to 70% in the region directly downstream of the injection hole due to enhanced mixing. At the same time, high freestream turbulence also produces a 50–100% increase in film cooling effectiveness in the region between injection boles. This is due to accelerated spanwise diffusion of the cooling fluid, which also produces an earlier merger of the coolant jets from adjacent holes.

Investigation of Film Cooling Effectiveness on Squealer Tip of a Gas Turbine Blade

2009 ◽  
Author(s):  
Dianliang Yang ◽  
Zhenping Feng ◽  
Xiaobing Yu
Keyword(s):  
Film Cooling ◽  
Turbulence Models ◽  
Tip Clearance ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blade Height ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Rotating Blade ◽  
Division Line

The effect of the film cooling holes arrangements and the blowing ratio on the tip film cooling effectiveness in a rotating blade with the squealer tip was investigated by using numerical methods in this paper. The first stage rotor blade with squealer tip of GE-E3 engine high pressure turbine was adopted to perform this study. The tip clearance was specified as 1% of the blade height, and the groove depth was specified as 2% of the blade height. The different turbulence models were checked by Kim’s experiment data [1] in 1995, and the standard k-ε turbulence model was chosen to predict the film cooling effectiveness on the blade tip. The film holes were arranged at the tip camber line, the tip division line, the tip pressure side and the pressure surface near tip, respectively. The effect of the holes position on the tip film cooling effectiveness in the rotating blade was studied. The effect of the blowing ratio was analyzed for the cases that the film holes were placed at the tip division line and the pressure surface near tip. The results show that the area-averaged tip film cooling effectiveness reaches the highest when the film holes are placed along the tip division line, and the tip leakage mass flow rate can be reduced by placing the film holes on the pressure surface near tip.

Numerical Investigation of Adiabatic and Conjugate Film Cooling Effectiveness on a Single Cylindrical Film-Cooling Hole

2004 ◽  
Author(s):  
Mahmood Silieti ◽  
Eduardo Divo ◽  
Alain J. Kassab
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Turbulence Models ◽  
Temperature Fields ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Dimensional Distribution ◽  
Lift Off

This paper documents a computational investigation of the film-cooling effectiveness of a 3-D gas turbine endwall with one cylindrical cooling hole. The simulations were performed for an adiabatic and conjugate heat transfer models. Turbulence closure was investigated using five different turbulence models; the standard k-ε model, the RNG k-ε model, the realizable k-ε model, the standard k-ε model, as well as the SST k-ω model. Results were obtained for a blowing ratio of 2.0, and a coolant-to-mainflow temperature ratio of 0.54. The simulations used a dense, high quality, O-type, hexahedral grid. The computed flow/temperature fields are presented, in addition to local, two-dimensional distribution of film cooling effectiveness for the adiabatic and conjugate cases. Results are compared to experimental data in terms of centerline film cooling effectiveness downstream cooling-hole, the predictions with realizable k-ε turbulence model exhibited the best agreement especially in the region for (x/D ≤ 6). All turbulence models predicted the jet lift-off. Also, the results show the effect of the conjugate heat transfer on the temperature (effectiveness) field in the film-cooling hole region and, thus, the additional heating up of the cooling jet itself.

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