Influence of cooling air jets on the aerodynamic and aerothermal losses and cooling effectiveness of air-cooled radial flameholder

2022 ◽  
Vol 172 ◽  
pp. 107355
Author(s):  
Yuqian Chen ◽  
Yuxin Fan ◽  
Qixiang Han
Keyword(s):  
Cooling Effectiveness ◽  
Air Jets ◽  
Cooling Air

Experimental Study on Racetrack-Shaped Holes Impingement Cooling With Bump Type Roughening Element

2012 ◽  
Author(s):  
Chiyuki Nakamata ◽  
Yoji Okita ◽  
Takashi Yamane ◽  
Yoshitaka Fukuyama ◽  
Toyoaki Yoshida
Keyword(s):  
Experimental Study ◽  
Flow Condition ◽  
Reynolds Numbers ◽  
Main Flow ◽  
The Other ◽  
Relative Location ◽  
Target Plate ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Cooling Air

Cooling effectiveness of an impingement cooling with array of racetrack-shaped impingement holes is investigated. Two types of specimens are investigated. One is a plain target plate and the other is a plate roughened with bump type elements. Sensitivity of relative location of bump to impingement hole on the cooling effectiveness is also investigated. Experiments are conducted under three different mainflow Reynolds numbers ranging from 2.6×105 to 4.7×105, with four different cooling air Reynolds numbers for each main flow condition. The cooling air Reynolds numbers are in the range from 1.2×103 to 1.3×104.

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.

Phantom Cooling of Nozzle Trailing Edge Discharge on Blade Surface and Platform

2014 ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Secondary Flows ◽  
Blade Surface ◽  
Suction Surface ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Cooling Flow ◽  
Discharge Velocity ◽  
Cooling Design ◽  
Cooling Air ◽  
Triangular Zone

Phantom cooling is defined as the cooling redistribution on airfoil surfaces and endwalls due to airfoil cooling discharges and leakages. Understanding of this effect has become especially critical in recent years, because of the restricted amount of cooling air for the achievement of higher efficiency. The phantom cooling effect of the first stage nozzle trailing edge discharge on the first stage blade surfaces and platform are studied numerically with URANS. Both time-dependent and time-averaged cooling effectiveness distributions on the rotor under the influence of vane trailing edge discharge are presented with different discharge velocity ratios. The results show that the nozzle trailing edge ejection affects the suction and pressure side cooling of the blade as well as the platform. The effects on the triangular zones of suction surface are evident, especially the bottom and top zones which are better cooled. Under the influence of passage secondary flows and rotating, different coolant discharge velocity ratios which resulted in different inlet angles have an effect on the phantom cooling distribution. In general, the cooling air discharged from the trailing edge of the first stage nozzle influences the temperature distribution on the blade, which can substantially improve the cooling efficiency in the bottom triangular zone. This suggests that accounting for phantom cooling can improve the cooling design and if actively controlled save cooling flow.

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.

Characterization of Advanced Combustor Cooling Concepts for Metallic Walls and Oxide Ceramic Matrix Composites in a Reacting Flow

2014 ◽  
Author(s):  
Thomas Behrendt ◽  
Tim Richter ◽  
Anna-Samira Söhngen
Keyword(s):  
Degrees Of Freedom ◽  
Ceramic Matrix Composites ◽  
Reacting Flow ◽  
Oxide Ceramic ◽  
Matrix Composites ◽  
Similar Reduction ◽  
Cooling Effectiveness ◽  
Air Jet ◽  
Manufacturing Techniques ◽  
Cooling Air

Effusion or full-coverage cooling is a promising approach to cooling especially the walls of lean combustors where the cooling air consumption is to be reduced significantly. Due to typical velocity distributions and cooling air pressure drop in a combustor the effectiveness can be further increased by reducing the cooling air momentum. Double skin designs like impingement effusion cooling offer a significant improvement but at the drawback of a complex and expensive manufacturing process. In this contribution different advanced cooling concepts offering a similar reduction of the cooling air jet momentum in a single skin design for metal and ceramic walls are characterized under realistic conditions. Lateral trenches as well as effusion holes with 90° turns are used. Their total cooling effectiveness is compared to a plain single skin effusion cooling concept. A configuration with cooling air flowing parallel to the surface into lateral trenches revealed the highest and most uniform distribution of the cooling effectiveness. The metallic samples are manufactured using additive manufacturing offering additional degrees of freedom in the cooling design in comparison to conventional manufacturing techniques.

Numerical Analysis of Impingement/Effusion Cooling Effectiveness on Flat Plates

2015 ◽  
Author(s):  
Ivin Ignatious ◽  
Jayakumar Janardanan Sarasamma
Keyword(s):  
High Temperature ◽  
Control Volume ◽  
Electrical Power ◽  
Hybrid Scheme ◽  
Flat Plates ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Adiabatic Cooling ◽  
Temperature Combustion ◽  
Cooling Air

The impingement/effusion cooling is a method of using cooling air to protect the hot combustor liner surfaces from high temperature effectively. This paper investigates the impingement/effusion cooling over two perforated flat plates and proposes a better cooling scheme for high temperature combustion liners in aircrafts and electrical power generation application. The adiabatic cooling effectiveness distribution over the liner surface is numerically studied by control volume technique in CFD. In this hybrid scheme the hydraulic diameter (d) of the hole is 1mm and impingement plate is provided with holes normal to the plate over its whole length of 250d. While effusion plate has only 20 rows of holes inclined at 30° to its surface. The effect of blowing ratio (BR) over this hybrid scheme of cooling is studied for different BR of 0.5, 1.0, 1.5 and 2.0. It has been found that the area averaged effectiveness increases steeply for BR 0.5 to 1.0 but further increase in BR results only in a small increase. The results also show that increasing the hole diameter increases averaged effectiveness while increasing the center-to-center spacing decreases averaged effectiveness.

Improved Trench Film Cooling With Shaped Trench Outlets

2011 ◽  
Author(s):  
Habeeb Idowu Oguntade ◽  
Gordon E. Andrews ◽  
Alan Burns ◽  
Derek B. Ingham ◽  
Mohammed Pourkashanian
Keyword(s):  
Mass Flow ◽  
Film Cooling ◽  
Cross Flow ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Vertical Slot ◽  
Superior Surface ◽  
Cooling Air ◽  
Computational Predictions

This paper presents the influence of the shaped trailing edge of trench outlets on film cooling effectiveness and aerodynamics. A 90° outlet wall to a trench will give a vertical slot jet into the cross flow and it was considered that improvements in the cooling effectiveness would occur if the trailing edge of the trench outlet was bevelled or filleted. CFD approach was used for these investigations which started with the predictions of the conventional sharp edged trench outlet for two experimental geometries. The computational predictions for the conventional sharp edged trench outlet were shown to have good agreement with the experimental data for two experimental geometries. The shaped trailing edge of the trench outlet was predicted to improve the film cooling effectiveness. The bevelled and filleted trench outlets were predicted to further suppress vertical jet momentum and give a Coanda effect that allowed the cooling air to attach to the downstream wall surface with a better transverse spread of the coolant film. The new trench outlet geometries would allow a reduction in film cooling mass flow rate for the same cooling effectiveness. Also, it was predicted that reducing the coolant mass flow per hole and increasing the number of holes gave, for the same total coolant mass flow, a much superior surface averaged cooling effectiveness for the same cooled surface area.

Spatial Arrangement Dependance of Cooling Performance of an Integrated Impingement and Pin Fin Cooling Configuration

2005 ◽  
Author(s):  
Chiyuki Nakamata ◽  
Yoji Okita ◽  
Shinsuke Matsuno ◽  
Fujio Mimura ◽  
Masahiro Matsushita ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Thermal Performance ◽  
Gas Flow ◽  
Internal Heat ◽  
Spatial Arrangement ◽  
Main Concern ◽  
Cooling Effectiveness ◽  
Pin Fin ◽  
Cooling Air ◽  
Side Flow

Experimental and numerical studies were conducted for the development of the integrated impingement and pin-fin cooling configuration. In the development, the spatial arrangements of impingement hole, pin-fin and film cooling (discharge) hole were the main concern. The temperature measurement was performed for different test pieces with various spatial arrangements to clarify the cooling effectiveness variation with the arrangement and the other cooling parameters. Experiments were conducted with 673K hot gas flow and room temperature cooling air. The Reynolds number of gas side flow was 380000 and cooling air Reynolds number was 5000–30000. Test plate surface temperatures were measured using an infrared camera. The cooling effectiveness obtained from the experiment for one specimen was different from that for a specimen that had the same pin density but a different spatial arrangement. So it was confirmed that an arrangement of hole and pin, as well as pin density, was an important parameter. CFD analysis was also conducted to make clear how spatial arrangement affected internal heat transfer characteristics. Pressure losses were also evaluated for each specimen, and total thermal performance was compared. A basic configuration with one pin at the center of a unit area showed the most superior total thermal performance.

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