Numerical Investigations of Cooling Enhancement With Internal Ribs and External Coolant Film

2012 ◽  
Author(s):  
Zhixin Feng ◽  
Zhongwang Dou ◽  
Jianhua Wang ◽  
Shiyan Ma ◽  
Zhiqiang Zhang
Keyword(s):  
Film Cooling ◽  
Influence Factors ◽  
Numerical Approach ◽  
Cooling Effectiveness ◽  
Numerical Investigations ◽  
Wall Film ◽  
Ansys Cfx ◽  
Cooling Enhancement ◽  
Energy Equations ◽  
Cooling Air

Experimental and numerical investigations were carried out to study the average cooling performance of two different rectangular structures: 1) purely ribbed channel (only ribs were periodically embedded inner the wall of the structure); 2) combined structure of film cooling with the ribs (in the ribbed wall, film holes were periodically drilled). To create a similar environment of gas turbine blade, the experiments were performed at a high temperature mainstream, and the ambient temperature cooling air passed through the channel with the direction normal to the mainstream. In the experimental and numerical investigations, the overall cooling effect contributed by the heat conduction through channel’s wall and convections including internal ribbed wall and external film cooling was considered. In the numerical investigation, 3D conservation equations including mass, momentum, energy, turbulence eddy frequency and turbulence kinetic energy equations were solved with ANSYS-CFX, and the hybrid mesh technique and shear stress transport (SST) k-ω model were adopted. This numerical approach was validated by the experimental data. Using the validated numerical approach, the influence factors on the overall cooling effectiveness are discussed, and the effects of the internal ribs and external film cooling are numerically compared by the two structures. The relationship of the overall cooling effectiveness averaged over the rectangular surface with the mainstream Reynolds number, mass flow ratio and temperature ratio of the mainstream to cooling air, as well as the blowing ratio injected through the film holes was fitted by the numerical results.

scholarly journals Effects of Various Modeling Schemes on Mist Film Cooling Simulation

2005 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Turbulence Models ◽  
Cooling Effectiveness ◽  
Air Supply ◽  
Cooling Enhancement ◽  
Simulation Results ◽  
Density Ratios ◽  
Slot Film Cooling ◽  
Cooling Air

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on the simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Using a 2-D slot film cooling simulation with a fixed blowing angle and blowing ratio shows a 2% mist injected into the cooling air can increase the cooling effectiveness about 45%. The RNG k-ε model, RSM and the standard k-ε turbulence model with the enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance is affected negatively by the plenum in this study, which alters the velocity profile and turbulence intensity at the jet exit plane. The results of this paper can serve as the qualification reference for future more complicated studies including 3-D cooling holes, different blowing ratios, various density ratios, and rotational effect.

scholarly journals Parametric Study on Geometrical Arrangement of Sister Hole

2015 ◽  
Vol 773-774 ◽  
pp. 373-377
Author(s):  
Kamil Abdullah ◽  
Firdauz Amon ◽  
Mas Fawzi Mohd Ali
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Gas Turbines ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Geometrical Arrangement ◽  
Numerical Investigations ◽  
Ansys Cfx ◽  
Cooling Hole ◽  
The Common

Modern gas turbines require a sophisticated cooling scheme to remove the heat from its component to ensure it durability. One of the common techniques applied in the cooling scheme is film cooling The present study focuses numerical investigation of an sister cooling hole design. The investigations make use of commercial CFD software, ANSYS CFX. The numerical investigations have been carried out at Reynolds number, Re = 21,000 involving three differens blowing ratios, BR = 0.5, 1.0, and 1.5. Four different cases have been considered; STA, STB STC and SH. The results show promising improvement in terms of film cooling effectiveness with the implementation of sister holes in certain geometrical arrangements.

scholarly journals Effects of Various Modeling Schemes on Mist Film Cooling Simulation

2007 ◽  
Vol 129 (4) ◽  
pp. 472-482 ◽  
Author(s):  
Xianchang Li ◽  
Ting Wang
Keyword(s):  
Turbulence Intensity ◽  
Film Cooling ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Cooling Effectiveness ◽  
Air Supply ◽  
Cooling Enhancement ◽  
Simulation Results ◽  
Density Ratios ◽  
Cooling Air

Numerical simulation is performed in this study to explore film-cooling enhancement by injecting mist into the cooling air with a focus on investigating the effect of various modeling schemes on simulation results. The effect of turbulence models, dispersed-phase modeling, inclusion of different forces (Saffman, thermophoresis, and Brownian), trajectory tracking, and mist injection scheme is studied. The effect of flow inlet boundary conditions (with/without air supply plenum), inlet turbulence intensity, and the near-wall grid density on simulation results is also included. Simulation of a two-dimensional (2D) slot film cooling with a fixed blowing angle and blowing ratio shows a 2% mist (by mass) injected into the cooling air can increase the cooling effectiveness about 45%. The renormalization group (RNG) k-ε model, Reynolds stress model, and the standard k-ε turbulence model with an enhanced wall treatment produce consistent and reasonable results while the turbulence dispersion has a significant effect on mist film cooling through the stochastic trajectory calculation. The thermophoretic force slightly increases the cooling effectiveness, but the effect of Brownian force and Saffman lift is imperceptible. The cooling performance deteriorates when the plenum is included in the calculation due to the altered velocity profile and turbulence intensity at the jet exit plane. The results of this paper can provide guidance for corresponding experiments and serve as the qualification reference for future more complicated studies with 3D cooling holes, different blowing ratios, various density ratios, and rotational effect.

Enhancement of Film Cooling Effectiveness Using Rectangular Winglet Pair

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Prakhar Jindal ◽  
Shubham Agarwal ◽  
R. P. Sharma ◽  
A. K. Roy
Keyword(s):  
Film Cooling ◽  
Complete Solution ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Geometrical Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Enhancement ◽  
The Common

This study deals with the film cooling enhancement in a combustion chamber by the use of rectangular winglet vortex generators (VGs). Rectangular winglet pair (RWP) in both the common-flow up and the common-flow down configuration is installed upstream of a coolant injection hole on the lower chamber wall. A three-dimensional numerical approach with complete solution of Navier–Stokes (NS) equations closed by the k–ɛ turbulence model is used for analyzing the effect of VG installation on film cooling effectiveness enhancement. The effect of RWP orientation is investigated to deduce the best configuration which is then optimized in terms of its geometrical parameters including its upstream distance from the hole and the angle it makes with the incoming flow. Results obtained show that a RWP located upstream of the coolant hole in common-flow down configuration gives the best effectiveness enhancement with certain other geometrical parameters specified. A novel “mushroom” adiabatic distribution scheme for film cooling effectiveness and temperature has been discussed in the paper. This characteristic scheme is developed as a result of RWPs' vortices interaction with the coolant inlet jet and the hot mainstream flow. A detailed discussion of the mechanisms and the flow field properties underlying the effectiveness enhancement and other phenomenon observed has also been presented in the paper.

Experimental and Numerical Investigations of the NEKOMIMI Film Cooling Technology

2012 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
Ryozo Tanaka ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Film Cooling ◽  
Gas Turbines ◽  
Mixing Processes ◽  
Cooling Effectiveness ◽  
Numerical Investigations ◽  
Hot Gas ◽  
Cooling Technology ◽  
Lift Off ◽  
Cooling Air

The improvement of the thermal efficiency of modern gas turbines can be achieved by reducing the required 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 liftoff effects. Novel film cooling technologies 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 NEKOMIMI film cooling, which is derived from the original double-jet film cooling (DJFC).

Experimental and numerical investigations of overall cooling effectiveness on a vane endwall with jet impingement and film cooling

2019 ◽  
Vol 148 ◽  
pp. 1148-1163 ◽  
Author(s):  
Xing Yang ◽  
Zhansheng Liu ◽  
Qiang Zhao ◽  
Zhao Liu ◽  
Zhenping Feng ◽  
...  
Keyword(s):  
Film Cooling ◽  
Jet Impingement ◽  
Cooling Effectiveness ◽  
Numerical Investigations

Pressure Side and Cutback Trailing Edge Film Cooling in a Linear Nozzle Vane Cascade at Different Mach Numbers

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Giovanna Barigozzi ◽  
Antonio Perdichizzi ◽  
Silvia Ravelli
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Pressure Side ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Mach Numbers ◽  
Nozzle Guide ◽  
Cooling Air ◽  
Momentum Boundary Layer

Tests on a specifically designed linear nozzle guide vane cascade with trailing edge coolant ejection were carried out to investigate the influence of trailing edge bleeding on both aerodynamic and thermal performance. The cascade is composed of six vanes with a profile typical of a high pressure turbine stage. The trailing edge cooling features a pressure side cutback with film cooling slots, stiffened by evenly spaced ribs in an inline configuration. Cooling air is ejected not only through the slots but also through two rows of cooling holes placed on the pressure side, upstream of the cutback. The cascade was tested for different isentropic exit Mach numbers, ranging from M2is = 0.2 to M2is = 0.6, while varying the coolant to mainstream mass flow ratio MFR up to 2.8%. The momentum boundary layer behavior at a location close to the trailing edge, on the pressure side, was assessed by means of laser Doppler measurements. Cases with and without coolant ejection allowed us to identify the contribution of the coolant to the off the wall velocity profile. Thermochromic liquid crystals (TLC) were used to map the adiabatic film cooling effectiveness on the pressure side cooled region. As expected, the cutback effect on cooling effectiveness, compared to the other cooling rows, was dominant.

An Investigation of the Effects of Film Cooling in a High-Pressure Aeroengine Turbine Stage

2005 ◽  
Author(s):  
Kam S. Chana ◽  
Mary A. Hilditch ◽  
James Anderson
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Phase Iii ◽  
Cooling Effectiveness ◽  
Aerodynamic Efficiency ◽  
Cooling Flow ◽  
External Cooling ◽  
Improved Design ◽  
Density Ratios ◽  
Cooling Air

Cooling is required to enable the turbine components to survive and have acceptable life in the very high gas temperatures occurring in modern engines. The cooling air is bled from the compression system, with typically about 15% of the core flow being diverted in military engines and about 20% in civil turbofans. Cooling benefits engine specific thrust and efficiency by allowing higher cycle temperatures to be employed, but the bleed air imposes cycle penalties and also reduces the aerodynamic efficiency of the turbine blading, typically by 2–4%. Cooling research aims to develop and validate improved design methodologies that give maximum cooling effectiveness for minimum cooling flow. This paper documents external cooling research undertaken in the Isentropic Light Piston Facility at QinetiQ as part of a European collaborative programme on turbine aerodynamics and heat transfer. In Phase I, neither the ngv nor the rotor was cooled; cooling was added to the ngv only for Phase II, and to the rotor and ngv in Phase III. Coolant blowing rates and density ratios were also varied in the experiments. This paper describes the ILPF and summarises the results of this systematic programme, paying particular attention to the variation in aerofoil heat transfer with changing coolant conditions, and the effects coolant ejection has on the aerofoil’s aerodynamic performance.

Nekomimi Film Cooling Holes Configuration Under Conjugate Heat Transfer Conditions

2014 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Tobias Wüllner ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Secondary Flow ◽  
Flow Structure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling Effectiveness ◽  
Cooling Flow ◽  
Secondary Flow Structure ◽  
Cooling Air

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result in increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. Today it is common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also called kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRVs. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry. The NEKOMIMI configuration and two conventional cooling hole configurations (cylindrical and shaped holes) has been investigated numerically under adiabatic and conjugate heat transfer conditions. The influence of the conjugate heat transfer on the secondary flow structure has been analysed. In conjugate heat transfer calculations, it cannot directly derived from the surface temperature distribution if the reached cooling effectiveness values are due to the improved hole configuration with improved secondary flow structure or due to the heat conduction in the material. Therefore, a methodology has been developed, to distinguish between cooling effectiveness due to heat conduction in the material and film cooling flow over the surface. The numerical results shows that for the NEKOMIMI configuration, 77% of the reached overall cooling effectiveness is due to film cooling with improved flow structure in the secondary flow (ACRV) and 23% due to heat conduction in the material. For the cylindrical hole configuration, 10% of the reached overall cooling effectiveness is due to the film cooling flow structure and 90% due to heat conduction in the material.

Highest-Efficient Film Cooling by Improved NEKOMIMI Film Cooling Holes: Part 1 — Ambient Air Flow Conditions

2013 ◽  
Author(s):  
Karsten Kusterer ◽  
Nurettin Tekin ◽  
Frederieke Reiners ◽  
Dieter Bohn ◽  
Takao Sugimoto ◽  
...  
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Air Flow ◽  
Ambient Air ◽  
Flow Conditions ◽  
Test Rig ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Technology ◽  
Cooling Air

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result to an increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. It is a today common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also mentioned as kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRV. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry. The original configuration was found to be difficult for manufacturing even by advanced manufacturing processes. Thus, the improvement of this configuration has been reached by a set of geometry parameters, which lead to configurations much easier to be manufactured but preserving the principle of the NEKOMIMI technology. Within a numerical parametric study several advanced configurations have been obtained and investigated under ambient air flow conditions similar to conditions for a wind tunnel test rig. By systematic variation of the parameters a further optimization with respect to highest film cooling effectiveness has been performed. A set of most promising configurations has been also investigated experimentally in the test rig. The best configuration outperforms the basic configuration by 17% regarding the overall averaged adiabatic film cooling effectiveness under the experimental conditions.

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