Swirl Effects on Distributed Combustion for Near Zero Emission Gas Turbine Application

2010 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Vaibhav K. Arghode ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
High Heat ◽  
Spontaneous Ignition ◽  
Experimental Investigations ◽  
Diffusion Combustion ◽  
Swirl Intensity ◽  
Zero Emission ◽  
Colorless Distributed Combustion

Previous investigations of Colorless Distributed Combustion (CDC) demonstrated significant improvement in combustor’s performance. CDC is characterized by high recirculation of product gases, fast mixing, spontaneous ignition and distributed reaction, leading to avoidance of hotspots and much lower NOx emissions. In this investigation, CDC is sought with focus on tailored mixture preparation before ignition using swirl and achieving distributed combustion for developing near zero emission combustion under gas turbine combustion conditions. Numerical and experimental investigations have been performed on a cylindrical combustor. Different fuel injection and hot gases exit arrangements have been considered. Air was injected tangentially to produce vortical structure in the flow and produce high swirl intensity. Results obtained show ultra low NO emissions (∼3 PPM) at high heat release intensity of 36 MW/m3-atm at an equivalence ratio (Φ) of 0.6. The role of premixed and diffusion combustion is also examined.

Colorless Distributed Combustion (CDC) With Swirl for Gas Turbine Application

2010 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Vaibhav K. Arghode ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Hot Spot ◽  
Stability Limit ◽  
High Heat ◽  
Experimental Investigations ◽  
Gas Turbine Combustor ◽  
Swirl Flows ◽  
Thermal Nox ◽  
Colorless Distributed Combustion

Colorless Distributed Combustion (CDC) can provide significant improvement in gas turbine combustor performance. CDC is characterized by uniform thermal field in the entire combustion chamber, thus avoiding hot-spot regions for low NOx emissions (thermal NOx) and significantly improved pattern factor. In this paper, colorless distributed combustion with swirl is investigated in detail to seek the beneficial aspects of CDC and swirl flows with focus on developing ultra low emissions of NO and CO, and much improved pattern factor. Experimental investigations have been performed using a cylindrical combustor with different modes of fuel injection, swirling air injection and gas exit stream location of the combustor. Air was injected tangentially to impart swirl to the flow inside the combustor. Results showed very low levels of NO (∼3PPM) and CO (∼70PPM) emissions at equivalence ratio of 0.7 at a high heat release intensity of 36MW/m3atm with non-premixed mode of combustion. Results have also been obtained on lean stability limit and OH* chemiluminescence under both premixed and non-premixed conditions.

Non-Premixed and Premixed Colorless Distributed Combustion for Gas Turbine Application

2010 ◽  
Author(s):  
Vaibhav Arghode ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Spontaneous Ignition ◽  
Combustion Mode ◽  
Acoustic Signatures ◽  
Combustion Modes ◽  
Sound Levels ◽  
Colorless Distributed Combustion ◽  
Gas Recirculation

Non-premixed and premixed modes of Colorless Distributed Combustion (CDC) are investigated for application to gas turbine combustors. The CDC provides significant improvement in pattern factor, reduced NOx emission uniform thermal field in the entire combustion zone for it to be called as a isothermal reactor, and lower sound levels. Basic requirement for CDC is mixture preparation through good mixing between the combustion air and product gases so that the reactants are at much higher temperature to result in hot and diluted oxidant stream at temperatures that are high enough to auto-ignite the fuel and oxidant mixture. With desirable conditions one can achieve spontaneous ignition of the fuel with distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation two non-premixed combustion modes and one premixed combustion mode that provide potential for CDC is examined. In all the configurations the air injection port is positioned at the opposite end of the combustor exit, whereas the location of fuel injection ports is changed to give different configurations. The results are compared for global flame signatures, exhaust emissions, acoustic signatures, and radical emissions using experiments and flow field, gas recirculation and mixing using numerical simulations. Ultra low NOx emissions are observed for both the premixed and non-premixed combustion modes, and almost colorless flames (no visible flame color) have been observed for the premixed combustion mode. The non-premixed mode was also provided near colorless distributed combustion. The reaction zone is observed to be significantly different in the two non-premixed modes.

A Detailed Analytical Study of Hydrogen Reaction in a Novel Micromix Combustion System

2018 ◽  
Author(s):  
Ramzi Ben Abdallah ◽  
Vishal Sethi ◽  
Pierre Q. Gauthier ◽  
Andrew Martin Rolt ◽  
David Abbott
Keyword(s):  
Gas Turbine ◽  
Analytical Study ◽  
Fuel Injection ◽  
Numerical Models ◽  
Cross Flow ◽  
Diffusion Combustion ◽  
Thermal Boundary Conditions ◽  
Auto Ignition ◽  
Combustion Properties ◽  
Analytical Tools

Liquid hydrogen is considered a technically feasible fuel for all gas turbine applications including propulsion systems [1]. However, the exceptional combustion properties of hydrogen will make fundamental changes to gas turbine combustion systems essential. Micromixing, with a novel cross-flow fuel-injection feature and a large plurality of injection holes offers miniaturised diffusive combustion without the risk of auto-ignition or flashback. A detailed analytical study has been performed to explore combustion behaviour of hydrogen in the micro-diffusion combustor concept. The aims are to investigate a broad range of analytical tools and sensitivities related to hydrogen micromix combustion numerical modelling. Comparative studies based on a number of RANS and LES simulations were carried out to down-select suitable numerical models for species transport, turbulence, chemistry and thermochemistry. Simulation results were found to be particularly sensitive to the species diffusion effects. The study was then extended to identify proper thermal boundary conditions capable of replicating experimental work. A thorough discussion of the findings is provided. The study has generated a novel micromix-injector geometry promising to yield ultra-low NOx emissions. This paper sheds light on the difficulties encountered in modelling the combustion of a gaseous fuel (hydrogen) in a novel micro-diffusion combustion chamber and suggests effective approaches to overcome them. It also identifies additional benefits related to hydrogen as a fuel.

Relight Envelope of a Military Gas Turbine Engine: An Experimental Study

2008 ◽  
Author(s):  
R. K. Mishra ◽  
G. Gouda ◽  
B. S. Vedaprakash
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Full Scale ◽  
Test Facility ◽  
Turbine Engines ◽  
Engine Fuel ◽  
Gas Turbine Engines ◽  
Turbine Engine ◽  
Start Up

A twin spool low bypass turbofan engine under development and its combustor in full-scale were tested independently at altitude conditions to establish the relight envelope of the engine. Demonstration of relight capability and defining its boundary are mandatory for military gas turbine engines and for single engine application in particular. The engine was first subjected to windmill to establish its windmilling characteristics. The full engine was then tested for light-off in an altitude test facility simulating windmilling conditions from 4 to 12 km altitude with flight Mach numbers from 0.2 to 1.0. The relight boundary is defined based on the successful light-off points achieved from engine tests. Similar tests were carried out on the full-scale combustion chamber in a stand-alone mode simulating altitude conditions at engine flame-out. The combustor test has defined the light-off and lean blow out limits of the at each point on the relight boundary. The information of fuel-air ratio at light-off and blow-out is very useful in setting the engine fuel schedule for altitude operation and relight. In this paper an attempt is made to highlight various tests carried out on engine and its combustor to define the relight boundary of the engine. The paper also emphasizes the experience of combustor development and associated problems in meeting the relight challenges of military engines. These problems include the necessity of higher fuel-air ratio at high altitudes, the role of additional localized fuel injection through start-up atomizers, and effect of single igniter on relight characteristics. The relight envelope demonstrated by the engine is very satisfactory to meet the first flight requirement where the flight mission generally concentrate in the zone of 0.6 to 0.8 Mach and altitude does not exceed 10 to 12 km. Combustor and atomizer modification is needed to improve relight performance and to shift the boundary to further left.

Mixture Preparation Effects on Distributed Combustion for Gas Turbine Applications

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta ◽  
Kenneth M. Bryden ◽  
Sang C. Lee
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Hot Spot ◽  
Turbine Blades ◽  
Active Species ◽  
Low Noise ◽  
Spontaneous Ignition ◽  
Air Cooling ◽  
Nox Emissions ◽  
Mixing Process

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (∼10 ppm) and CO (∼21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3-atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.

Investigation of Distributed Combustion for Gas Turbine Application: Forward Flow Configuration

2010 ◽  
Author(s):  
Vaibhav K. Arghode ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
High Efficiency ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Spontaneous Ignition ◽  
Forward Flow ◽  
Combustion Modes ◽  
Flow Configurations ◽  
Thermal Intensity ◽  
Jet Characteristics

Colorless Distributed Combustion (CDC) has been investigated here for high efficiency and ultra low pollution gas turbine combustors applications. In this paper forward flow configurations have been examined. Basic requirement for CDC is carefully tailored mixture preparation prior to ignition through a combination of product gas recirculation, controlled mixing between the fresh combustion air and recirculated gases to form hot and diluted oxidizer. Rapid mixing between the injected fuel and hot oxidizer is desirable prior to spontaneous ignition of the mixture in the entire combustion zone to achieve distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation forward flow modes are considered in which three non-premixed and one premixed combustion mode have been examined that showed favorable CDC combustion conditions. In the forward flow configurations the air injection port is positioned at a location opposite to the combustor exit. The location of fuel injection ports is changed to give different configurations. The thermal intensity for the present investigation is 28MW/m3-atm simulating gas turbine conditions. Increase in thermal intensity (lower combustion volume) presents many challenges, such as, lower residence time, lower recirculation of gases and confinement effects on the jet characteristics. The results are presented on the global flame signatures, exhaust emissions, and emission of radical species using experiments and flowfield dynamics using numerical simulations. Ultra low NOx emissions are found for both the premixed and non-premixed combustion modes investigated here. The reaction zone is observed to be significantly different in different combustion modes.

Experimental Observation of Jet Flow and Liquid Exploding Emission From Mini/Micro Tubes During Boiling

2008 ◽  
Author(s):  
D. Wu ◽  
X. F. Peng ◽  
B. X. Wang
Keyword(s):  
Thin Liquid Film ◽  
Temperature Drop ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Experimental Investigations ◽  
Jet Flows ◽  
Bubble Generation ◽  
Heating Wire

A series of experimental investigations were conducted to visually observe the fundamental features of boiling nucleation of water in micro capillary tubes covered with transparent metal film and ethanol in mini tubes winded with a heating wire as a heater. Normally, boiling nucleation and/or bubble generation were not observed even at very high heat fluxes compared with usual nucleate boiling situations. In mini tubes violent jet flows formed and played an important role of triggering the emission, while in micro tubes the liquid and/or vapor was instantaneously emitted as the applied heat flux reached a certain high value, rather than initialing nucleate boiling and jet flows which was much weaker than exploding emission. After the exploding emission, an ultra thin liquid film formed on the tube wall and evaporated intensely, causing a perceptible wall temperature drop.

Impact of Biodiesel on Fuel Preparation and Emissions for a Liquid Fired Gas Turbine Engine

2007 ◽  
Author(s):  
Christopher Bolszo ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Gas Turbine ◽  
Diesel Fuel ◽  
Fuel Injection ◽  
Engine Performance ◽  
Compositional Analysis ◽  
Gas Turbine Engine ◽  
Fuel Injector ◽  
Turbine Engine ◽  
Fuel Distillate

This paper reports the fuel injection, vaporization, and emissions characteristics when running a 30 kW gas turbine engine on biodiesel (B99), and diesel fuel distillate # 2. Compositional analysis is used to assess the distillation of these fuels and a comparison is made with ethanol. The role of the liquid properties on fuel preparation and the subsequent engine performance is also assessed. The results show that while compositionally simple, biodiesel features some properties that result in inferior atomization and longer evaporation times compared to DF2. In addition, the overall spray behavior differs substantially in terms of density and width. The measured NO and CO emissions levels produced by the engine reveal significant increases with the use of biodiesel which is expected given the inferior fuel preparation characteristics. It appears reasonable to modify the fuel injector in order to overcome the deleterious effects observed for biodiesel. The benefits of blending biodiesel and ethanol in order to eliminate duel fuel operation during cold startup are discussed.

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