Impact of an Upstream Film-Cooling Row on Mitigation of Secondary Combustion in a High Fuel-Air Environment

2012 ◽  
Author(s):  
Brian T. Bohan ◽  
David L. Blunck ◽  
Marc D. Polanka ◽  
Stanislav Kostka ◽  
Naibo Jiang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Film Cooling ◽  
Laser Induced Fluorescence ◽  
Turbine Engines ◽  
Experimental Film ◽  
Gas Turbine Engines ◽  
Negative Effects ◽  
Secondary Combustion ◽  
Planar Laser ◽  
Negative Impacts

In advanced gas turbine engines that feature very short combustor sections, an issue of fuel-rich gases interacting with downstream components exists. In all of these engines there are regions downstream of the primary combustion section that will require the use of film-cooling in the presence of incompletely reacted exhaust. This will lead to the possibility of additional combustion reactions resulting from the combination of unburnt fuel and oxygen-rich cooling films. Research has been accomplished to understand this secondary reaction process. This experimental film-cooling study expands the previous investigations by attempting to reduce or remove the negative effects that result from secondary combustion in the coolant film. An upstream row of holes was added to a row of previously tested shaped coolant holes to understand if the reactions could be mitigated at the downstream locations. Several combinations of cooling schemes were investigated and the heat flux downstream was measured. Planar Laser Induced Fluorescence (PLIF) was used to measure OH concentration in the combustion zones to understand where the reactions occurred. It was discovered that creating a full sheet of air upstream could effectively protect the downstream row from the negative impacts of the fuel-rich crossflow.

Impact of an Upstream Film-Cooling Row on Mitigation of Secondary Combustion in a Fuel Rich Environment

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Brian T. Bohan ◽  
David L. Blunck ◽  
Marc D. Polanka ◽  
Stanislav Kostka ◽  
Naibo Jiang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Film Cooling ◽  
Turbine Engines ◽  
Experimental Film ◽  
Double Row ◽  
Secondary Combustion ◽  
Significant Damage ◽  
Planar Laser ◽  
Secondary Reactions ◽  
Reactive Gases

In advanced gas turbine engines that feature very short combustor sections, an issue of fuel-rich gases interacting with the downstream turbine components can exist. Specifically, in combustors with high fuel-to-air ratios, there are regions downstream of the primary combustion section that will require the use of film-cooling in the presence of incompletely reacted exhaust. Additional combustion reactions resulting from the combination of unburnt fuel and oxygen-rich cooling films can cause significant damage to the turbine. Research has been accomplished to understand this secondary reaction process. This experimental film-cooling study expands the previous investigations by attempting to reduce or mitigate the increase in heat flux that results from secondary combustion in the coolant film. Two different upstream cooling schemes were used to attempt to protect a downstream fan-shaped cooling row. The heat flux downstream was measured and compared between ejection with air compared to nitrogen in the form of a heat flux augmentation. Planar Laser Induced Fluorescence (PLIF) was used to measure relative OH concentration in the combustion zones to understand where the reactions occurred. A double row of staggered normal holes was unsuccessful at reducing the downstream heat load. The coolant separated from the surface generating a high mixing regime and allowed the hot unreacted gases to penetrate underneath the jets. Conversely, an upstream slot row was able to generate a spanwise film of coolant that buffered the reactive gases off the surface. Essentially no secondary reactions were observed aft of the shaped coolant hole ejection with the protective slot upstream. A slight increase in heat transfer was attributed to the elevated freestream temperature resulting from reactions above the slot coolant. Creating this full sheet of coolant will be a key toward future designs attempting to control secondary reactions in the turbine.

Minimization of Heat Load Due to Secondary Reactions in Fuel Rich Environments

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Andrew T. Shewhart ◽  
Marc D. Polanka ◽  
Jacob J. Robertson ◽  
Nathan J. Greiner ◽  
James L. Rutledge
Keyword(s):  
Heat Flux ◽  
Film Cooling ◽  
Turbine Blades ◽  
Local Heat ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Gas Turbine Engines ◽  
Engine Efficiency ◽  
Secondary Reactions ◽  
Local Heat Flux

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow, and augmented heat transfer to the blade arises. This result is contrary to the purpose of film cooling. In this environment, there is a competing desire to consume any free radicals prior to the flow entering the rotor stage while still maintaining surface temperatures below the metal melting temperature. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream cooling. Results were evaluated based on net heat flux reduction (NHFR) and a new wall absorption (WA) parameter which combined the additional heat available from these secondary reactions with the length of the resulting flame to determine which schemes protected the wall more efficiently. Two particular schemes showed promise. The two row upstream configuration reduced the overall augmentation of heat by creating a short, concentrated reaction area. Conversely, the roll forward configuration minimized the local heat flux enhancement by spreading the reaction area over the surface being cooled.

Relative Effects of Velocity- and Mixture-Coupling in a Thermoacoustically Unstable, Partially-Premixed Flame

2021 ◽  
Author(s):  
Ashwini Karmarkar ◽  
Isaac Boxx ◽  
Jacqueline O'Connor
Keyword(s):  
Gas Turbine ◽  
Equivalence Ratio ◽  
Oscillation Mode ◽  
Laser Induced Fluorescence ◽  
Stereoscopic Particle Image Velocimetry ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Planar Laser Induced Fluorescence ◽  
Planar Laser ◽  
The Impact

Abstract Combustion instability, which is the result of a coupling between combustor acoustic modes and unsteady flame heat release rate, is a severely limiting factor in the operability and performance of modern gas turbine engines. This coupling can occur through different coupling pathways, such as flow field fluctuations or equivalence ratio fluctuations. In realistic combustor systems, there are complex hydrodynamic and thermo-chemical processes involved, which can lead to multiple coupling pathways. In this study, we use a model gas turbine combustor with two concentric swirling nozzles of air, separated by a ring of fuel injectors, operating at an elevated pressure of 5 bar. The flow split between the two streams is systematically varied to observe the impact on the flow and flame dynamics. High-speed stereoscopic particle image velocimetry, OH planar laser-induced fluorescence, and acetone planar laser-induced fluorescence are used to obtain information about the velocity field, flame, and fuel-flow behavior, respectively. Depending on the flow conditions, a thermoacoustic oscillation mode or a hydrodynamic mode, identified as the precessing vortex core, is present. Our results show that, for this combustor system, changing the flow split between the two concentric nozzles can alter the dominant harmonic oscillation modes in the system, which can significantly impact the dispersion of fuel into air, thereby modulating the local equivalence ratio of the flame. This insight can be used to design instability control mechanisms in real gas turbine engines.

Effects of Hot Streaks on Adiabatic Effectiveness for a Film Cooled Turbine Vane

2004 ◽  
Author(s):  
Krishnakumar Varadarajan ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Field Measurements ◽  
Suction Side ◽  
Experimental Program ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Hot Streak ◽  
Effectiveness Data

Turbine guide vanes in gas turbine engines are typically subjected to localized “hot streaks” emanating from the combustor. This experimental program examined how these hot streaks affect the film cooling performance for these vanes. Adiabatic effectiveness tests were conducted on the showerhead and suction side regions of the vane. Particular attention was placed on how to scale that adiabatic effectiveness data obtained with a hot streak to correctly predict the adiabatic effectiveness. Thermal field measurements were made to determine the temperature gradients for the hot streak near the wall. These experiments showed that the effect of the hot streak on the adiabatic effectiveness could be accounted for by using an “adjusted” mainstream temperature equal to the hot streak temperature at the wall of the vane.

Simulation of a Multi-Stage Cooling Scheme for Gas Turbine Engines: Part I

2007 ◽  
Author(s):  
M. Ghorab ◽  
I. Hassan ◽  
M. Beauchamp
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Gap Height ◽  
Internal Gap

This paper presents heat transfer characteristics for a Multi-Stage Cooling Scheme (MSCS) design applicable to high temperature gas turbine engines in aerospace and electric power generation. The film cooling and impingement techniques are considered concurrently throughout this study. The proposed design involves passing cooling air from the inside of the turbine blade to the outside through three designed stages. The coolant air is passed through a circular hole into an internal gap creating an impingement of air inside the blade. It then exits through a sequence of two differently shaped holes onto the blade’s external surface. The film cooling effectiveness is enhanced by increasing the internal gap height and offset distance. This effect is significantly diminished however by changing the inclination angle from 90° to 30° at large gap height. The coolant momentum became more uniform by creating the internal gap consequently the coolant air is spread closer to the external blade surface. This reduces jet liftoff as the air exits its hole and also provides internal cooling for the blade. The hole exit positioned on the outer surface of the blade is designed to give a positive and a wide downstream lateral spreading. The MSCS demonstrates greater film cooling effectiveness performance than traditional schemes.

Minimization of Heat Load due to Secondary Reactions in Fuel Rich Environments

2014 ◽  
Author(s):  
Andrew T. Shewhart ◽  
Marc D. Polanka ◽  
Jacob J. Robertson ◽  
Nathan J. Greiner ◽  
James L. Rutledge
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Local Heat ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Gas Turbine Engines ◽  
Engine Efficiency ◽  
Secondary Reactions ◽  
Local Heat Flux ◽  
Metal Melting

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow and augmented heat transfer to the blade arises. This result is contrary to the purpose of film cooling. In this environment there is a competing desire to consume any free radicals prior to the flow entering the rotor stage while still maintaining surface temperatures below the metal melting temperature. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream cooling. Results were evaluated based on a new Wall Absorption parameter which combined the additional heat available from these secondary reactions with the length of the resulting flame to determine which schemes protected the wall more efficiently. Two particular schemes showed promise. The two row upstream configuration reduced the overall augmentation of heat by creating a short, concentrated reaction area. Conversely, the roll forward configuration minimized the local heat flux enhancement by spreading the reaction area over the surface being cooled.

scholarly journals Effects of Bulk Flow Pulsations on Film Cooling From Different Length Injection Holes at Different Blowing Ratios

1998 ◽  
Author(s):  
H. J. Seo ◽  
J. S. Lee ◽  
P. M. Ligrani
Keyword(s):  
Film Cooling ◽  
Bulk Flow ◽  
Turbine Engines ◽  
Pulsation Frequency ◽  
Gas Turbine Engines ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Temperature Distributions ◽  
Flow Interactions ◽  
Flow Pulsations

Bulk flow pulsations in the form of sinusoidal variations of velocity and static pressure at injectant Strouhal numbers from 0.8 to 10.0 are investigated as they affect film cooling from a single row of simple angle holes. Similar flow variations are produced by potential flow interactions and passing shock waves near turbine surfaces in gas turbine engines. Time-averaged temperature distributions, phase-averaged temperature distributions, adiabatic film cooling effectiveness values, and iso-energetic Stanton numbers show that important alterations to film cooling protection occur as pulsation frequency, coolant Strouhal number, blowing ratio, and non-dimensional injection hole length are changed. Overall, the pulsations affect film performance end behavior more significantly both as L/D decreases, and as blowing ratio decreases.

NETL Research Efforts on Development and Integration of Advanced Material Systems and Airfoil Cooling Configurations for Future Land-Based Gas Turbine Engines

2014 ◽  
Author(s):  
M. A. Alvin ◽  
J. Klinger ◽  
B. McMordie ◽  
M. Chyu ◽  
S. Siw ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Low Cost ◽  
Oxide Dispersion Strengthened ◽  
Advanced Materials ◽  
Turbine Engines ◽  
Internal Cooling ◽  
Gas Turbine Engines ◽  
Near Surface ◽  
Material Systems

As future land-based gas turbine engines are being designed to operate with inlet temperatures exceeding 1300°C (2370°F), efforts at NETL have been focused on developing advanced materials systems that are integrated with novel airfoil cooling architectures. Recent achievements in the areas of low cost diffusion bond coat systems applied to single- and poly-crystalline nickel-based superalloys, as well as development of thin nickel-based oxide dispersion strengthened layers are presented in this paper. Integration of these material systems with commercially cast, novel, pin-fin internal cooling airfoil arrays, tripod film cooling hole architectures, trailing edge cooling geometries, and near surface micro-channel concepts is also presented.

The Effect of Internal Crossflow on the Adiabatic Effectiveness of Compound Angle Film Cooling Holes

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
John W. McClintic ◽  
Sean R. Klavetter ◽  
James R. Winka ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
...  
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Experimental Studies ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Experimental Conditions ◽  
Turbine Engine ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes ◽  
Compound Angle

In gas turbine engines, film cooling holes are often fed by an internal crossflow, with flow normal to the direction of the external flow around the airfoil. Many experimental studies have used a quiescent plenum to feed model film cooling holes and thus do not account for the effects of internal crossflow. In this study, an experimental flat plate facility was constructed to study the effects of internal crossflow on a row of cylindrical compound angle film cooling holes. There are relatively few studies available in literature that focus on the effects of crossflow on film cooling performance, with no studies examining the effects of internal crossflow on film cooling with round, compound angled holes. A crossflow channel allowed for coolant to flow alternately in either direction perpendicular to the mainstream flow. Experimental conditions were scaled to match realistic turbine engine conditions at low speeds. Cylindrical compound angle film cooling holes were operated at blowing ratios ranging from 0.5 to 2.0 and at a density ratio (DR) of 1.5. The results from the crossflow experiments were compared to a baseline plenum-fed configuration. This study showed that significantly greater adiabatic effectiveness was achieved for crossflow counter to the direction of coolant injection.

scholarly journals Dry Low Emissions Combustor Development

1998 ◽  
Author(s):  
Narendra D. Joshi ◽  
Hukam C. Mongia ◽  
Gary Leonard ◽  
Jim W. Stegmaier ◽  
Ed. C. Vickers
Keyword(s):  
Film Cooling ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Oxidation Reactions ◽  
Entire Family ◽  
Passive Devices ◽  
Key Characteristics ◽  
Lean Premixed ◽  
Fuel Staging ◽  
Full Power

Lower Emissions have become key characteristics of most new gas turbine engines over the last several years. The ‘lean premixed’ approach has been used in the development of the Dry Low Emissions (DLE) technology. The LM6000 and the LM2500 combustors employ a triple dome design with staging of fuel and air flows to achieve lean-premixed operation from light-off to full power. This technology permits the operator to run with reduced emissions of NOx as well as CO and UHC over a wide load setting. Emissions goals of 25 ppm have been successfully met at site rating conditions for the entire family of LM DLE products. The DLE combustor operates on the mid dome at light-off, the inner and the outer domes are brought on progressively, as the engine is loaded. The combustor utilizes a small quantity of air for dome and liner cooling as most of the combustor air is mixed with fuel in the premixers. Backside cooling enhancements permit the reduction of film cooling, which can cause quenching of CO oxidation reactions. Combustion acoustics are controlled by the use of passive devices on the exterior of the engine as well as by fuel staging within premixers and by the use of a control system which senses and alters the combustor operation to limit acoustics. The DLE technology meets the emissions and reliability needs of the industry with limited package modifications. This paper describes the DLE technology, developed to meet the needs of the industry. Critical design features including the Double Annular Counter-Rotating Swirler (DACRS) premixer, the triple annular dome design, the heat shield design and the staging sequence are discussed, in addition to the field experience gained on the LM2500 and LM6000 DLE models.

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