scholarly journals EVALUATION OF THE RANS TURBULENCE MODEL PREDICTIVE CAPABILITY OF FLAT PLATE FILM COOLING

2021 ◽  
Vol 850 (1) ◽  
pp. 012020
Author(s):  
F Ferdaus ◽  
N Raghukiran
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Turbulence Models ◽  
Lateral Spreading ◽  
Test Surface ◽  
Ansys Fluent ◽  
Cooling Hole ◽  
Cooling Behavior ◽  
Mass Flow Rates ◽  
Theoretical Results

Abstract The two-equation turbulence models used for the present study are the commonly used standard k-ॉ model and k-ω model. In order to achieve this target, numerical simulation was initiated in Ansys Fluent to simulate a flow over a flat test surface with a diameter of 4mm straight, circular film cooling hole at angled injections of 25°, 30°, 35°and 40°. The comparison between the numerical calculations and the theoretical results showed the standard k-ω turbulence model gave better predictions against those with the standard k-ω turbulence models. The ability of k-ω model in closely predicting the cooling behavior is due to the precise modeling of the lateral spreading of the film. The isotropic two-equation turbulence models exhibited a huge dissent. The results also indicated that increasing the mass flow rates in the mainstream channels reduces the temperature distribution along the stream-wise direction.

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 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.

Computational Study of Jet-in-Crossflow and Film Cooling Using a New Unsteady-Based Turbulence Model

2005 ◽  
Author(s):  
D. Scott Holloway ◽  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Computational Study ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Turbulence Models ◽  
Streamwise Velocity ◽  
Pressure Side ◽  
Good Test ◽  
Jet In Crossflow

This paper documents a computational investigation of the unsteady behavior of jet-in-crossflow applications. Improved prediction of fundamental physics is achieved by implementing a new unsteady, RANS-based turbulence model developed by the authors. Two test cases are examined that match experimental efforts previously documented in the open literature. One is the well-documented normal jet-in-crossflow, and the other is film cooling on the pressure side of a turbine blade. All simulations are three-dimensional, fully converged, and grid-independent. High-quality and high-density grids are constructed using multiple topologies and an unstructured, super-block approach to ensure that numerical viscosity is minimized. Computational domains include the passage, film hole, and coolant supply plenum. Results for the normal jet-in-crossflow are for a density ratio of 1 and velocity ratio of 0.5 and include streamwise velocity profiles and injected flow or “coolant” distribution. The Reynolds number based on the average jet exit velocity and jet diameter is 20,500. This represents a good test case since normal injection is known to exaggerate the key flow mechanisms seen in film-cooling applications. Results for the pressure side film-cooling case include coolant distribution and adiabatic effectiveness for a density and blowing ratio of 2. In addition to the in-house model that incorporates new unsteady physics, CFD simulations utilize standard, RANS-based turbulence models, such as the “realizable” k-ε model. The present study demonstrates the importance of unsteady physics in the prediction of jet-in-crossflow interactions and for film cooling flows that exhibit jet liftoff.

scholarly journals Application of different turbulence models for improving construction of small-scale boiler fired by solid fuel

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 809-823
Author(s):  
Nebojsa Manic ◽  
Vladimir Jovanovic ◽  
Dragoslava Stojiljkovic ◽  
Zagorka Brat
Keyword(s):  
Turbulence Model ◽  
Solid Fuel ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Experimental Tests ◽  
Computer Hardware ◽  
Small Scale ◽  
Heat Output ◽  
Ansys Fluent ◽  
Model Fluid

Due to the rapid progress in computer hardware and software, CFD became a powerful and effective tool for implementation turbulence modeling in defined combustion mathematical models in the complex boiler geometries. In this paper the commercial CFD package, ANSYS FLUENT was used to model fluid flow through the boiler, in order to define velocity field and predict pressure drop. Mathematical modeling was carried out with application of Standard, RNG, and Realizable k-? turbulence model using the constants presented in literature. Three boilers geometry were examined with application of three different turbulence models with variants, which means consideration of 7 turbulence model arrangements in FLUENT. The obtained model results are presented and compared with data collected from experimental tests. All experimental tests were performed according to procedures defined in the standard SRPS EN 303-5 and obtained results are presented in this paper for all three examined geometries. This approach was used for improving construction of boiler fired by solid fuel with heat output up to 35 kW and for selection of the most convenient construction.

Numerical Prediction of a Multistage Centrifugal Pump Performance With Stationary and Moving Mesh

2015 ◽  
Author(s):  
Alessandro Nocente ◽  
Tufan Arslan ◽  
Torbjørn K. Nielsen
Keyword(s):  
Centrifugal Pump ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Transient State ◽  
Computational Effort ◽  
Phase Flow ◽  
Two Phase ◽  
Ansys Fluent ◽  
Performance Report

The present work reviews a comparison between calculations of a steady and unsteady three dimensional (3D) flow past the diffuser channels of a centrifugal pump. The commercial software ANSYS Fluent has been used. The considered domain is one of the three stages, since each has exactly the same design. In the first part, simulations are carried out at the best efficiency point (BEP) both steady and transient state, single phase flow and four different turbulence models. Results are compared with the performance report from the manufacturer. In the second part, only the realizable k-ε turbulence model has been taken into account. The simulations have been repeated for different mass flows and the results were again compared with the data from the manufacturer. The comparison performed in the first part shows that integral quantities results are not sensibly influenced by the turbulence model. The comparison at different mass flow shows that the steady state simulations demonstrated to be a good approximation of the transient state, always containing the error within an acceptable limit. The minor computational effort needed makes it attractive to be used for further investigations which will involve two-phase flow studies on the same pump.

Numerical Investigation of a Laser-Drilled Cooling Hole

2017 ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Average Height ◽  
Conical Nozzle ◽  
Film Cooling Effectiveness ◽  
Hole Area ◽  
Cooling Hole ◽  
Common Technique ◽  
Mass Flow Rates ◽  
Percussion Laser Drilling

Modern aeroengines utilized effusion cooling technology to further protect the components from degrading at the operating temperatures. Most studies did not address the influence of the manufacturing process used to form the cooling holes on the flow physics where percussion laser drilling was a common technique that produced irregularly shaped holes with roughened surfaces. The investigated as-drilled hole surface was statistically homogeneous, non-isotropic, and generally composed of gradually transitioning plateaus that had imperfections with an average height of 0.32 hole diameters. A conjugate heat transfer CFD study was completed on cylindrical, conical nozzle, and as-drilled holes, all yielding the same hole mass flow rates, with the realizable k-ε turbulence model at representative engine conditions. The cylindrical hole had higher film cooling effectiveness due to lower effluent velocity, and better in-hole heat transfer performance due to higher on-average in-hole flow velocities. The as-drilled hole had nominally better film cooling than the conical nozzle hole due to the higher in-hole turbulence production caused by the roughened surface texture. Ultimately, the hole area profile more significantly influenced the averaged metal temperature.

Film Cooling and Thermal Field Measurements for Staggered Rows of Rectangular-Shaped Film Cooling Holes

2003 ◽  
Author(s):  
Dong Ho Rhee ◽  
Youn Seok Lee ◽  
Young Bong Kim ◽  
Hyung Hee Cho
Keyword(s):  
Film Cooling ◽  
Lateral Spreading ◽  
Temperature Fields ◽  
Test Surface ◽  
Spanwise Direction ◽  
Rectangular Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular-shaped film cooling holes with various blowing rates. Three different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit and a circular hole are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. The holes are spaced 3d apart in the spanwise direction and 4d apart in the streamwise direction with a staggered arrangement. Temperature fields are acquired using a three-axis traversing system equipped with a thermocouple rake. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. The results show that the rectangular-shaped holes provide better performance than the cylindrical holes because the penetration of coolant is reduced and the lateral spreading of coolant is promoted. For rows of film cooling holes, the film cooling performance decreases with increasing blowing rate. However, the difference of hole shapes and blowing rates for film cooling performance is reduced with increasing the row of cooling holes.

Experimental and Computational Comparisons of Fan-Shaped Film-Cooling on a Turbine Vane Surface

2005 ◽  
Author(s):  
W. Colban ◽  
K. A. Thole ◽  
M. Haendler
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Turbulence Models ◽  
Complex Flow ◽  
Ir Camera ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Film Cooling Holes

The flow exiting the combustor in a gas turbine engine is considerably hotter than the melting temperature of the turbine section components, of which the turbine nozzle guide vanes see the hottest gas temperatures. One method used to cool the vanes is to use rows of film-cooling holes to inject bleed air that is lower in temperature through an array of discrete holes onto the vane surface. The purpose of this study was to evaluate the row-by-row interaction of fan-shaped holes as compared to the performance of a single row of fan-shaped holes in the same locations. This study presents adiabatic film-cooling effectiveness measurements from a scaled-up, two-passage vane cascade. High resolution film-cooling measurements were made with an infrared (IR) camera at a number of engine representative flow conditions. Computational fluid dynamics (CFD) predictions were also made to evaluate the performance of some of the current turbulence models in predicting a complex flow such as turbine film-cooling. The RNG k-ε turbulence model gave a closer prediction of the overall level of film-effectiveness, while the v2-f turbulence model gave a more accurate representation of the flow physics seen in the experiments.

Experimental Investigations on Aero-Thermal Interaction of Film Cooling Air Ejected From Multiple Shallow Angle Cooling Holes: Effect of Freestream Turbulence

2013 ◽  
Author(s):  
Kamil Abdullah ◽  
Ken-ichi Funazaki
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Test Model ◽  
Thermal Interaction ◽  
Freestream Turbulence ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Test Models ◽  
Cooling Hole

The objective of the present study is to investigate the aero-thermal interaction of the secondary air injected from multiple shallow angled film cooling holes. The focus is on the influence of freestream turbulence on the film cooling effectiveness and secondary flow field. For the experiments, infrared thermography and Laser Doppler Velocimetry (LDV) were employed. The experiments were conducted at a Reynolds number based on the hole diameter, ReD = 6200 at blowing ratio, BR = 1.0 and 2.0. Two flat plate test models; TMA and TMG, have been considered, which involved twenty cylindrical holes constituting a matrix composed of four rows with five holes in each row. The cooling holes for both test models were inclined at 20° in the streamwise direction with the lateral pitch, Pz = 6D for TMA and 3D for TMG. Two different freestream turbulence levels have been considered for both the aerodynamic and thermal investigations. The results of LDV show two distinct dynamics for each test model which influence the flow field differently. Consequently, the thermal field produced a distinctive film cooling effectiveness distribution of each test model. Higher freestream turbulence level enhances the mixing in the vicinity of the vortical structure thus deterring the film cooling effectiveness just downstream of the cooling hole but aids to lateral spreading of the coolant further downstream of the cooling hole, providing greater film effectiveness coverage.

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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