Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2–Natural Gas–Air Mixtures

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Matthias Utschick ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Atmospheric Pressure ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Air Flow ◽  
Fuel Injector ◽  
Safe Operation ◽  
Trailing Edge ◽  
Turbine Model

Flashback (FB) and self-ignition in the premixing zone of typical gas turbine swirl combustors in lean premixed operation are immanent risks and can lead to damage and failure of components. Thus, steady combustion in the premixing zone must be avoided under all circumstances. This study experimentally investigates the flame holding propensity of fuel injectors in the swirler of a gas turbine model combustor with premixing of H2–natural gas (NG)–air mixtures under atmospheric pressure and proposes a model to predict the limit for safe operation. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). A cylindrical duct and a window in the swirler made of quartz glass allow the application of optical diagnostics (OH* chemiluminescence and planar laser induced fluorescence of the OH radical (OH-PLIF)) inside the swirler. The fuel–air mixture was ignited with a focused single laser pulse during steady operation. The position of ignition was located inside the swirler in proximity to a fuel injection hole. If the flame was washed out of the premixing zone not later than 4 s after the ignition, the operation point was defined as safe. Operation points were investigated at three air mass flows, three air ratios, two air preheat temperatures (573 K and 673 K), and 40 to 100 percent per volume hydrogen in the fuel composed of hydrogen and natural gas. The determined safety limit for atmospheric pressure yields a similarity rule based on a critical Damköhler number. Application of the proposed rule at conditions typical for gas turbines leads to these safety limits for the A2EV burner: With the TEIs, the swirler can safely operate with up to 80 percent per volume hydrogen content in the fuel at an air ratio of two. With the JIC injector, safe operation at stoichiometric conditions and 95 percent per volume hydrogen is possible.

Flame Holding in the Premixing Zone of a Gas Turbine Model Combustor After Forced Ignition of H2-NG-Air-Mixtures

2016 ◽  
Author(s):  
Matthias Utschick ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Atmospheric Pressure ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Air Flow ◽  
Fuel Injector ◽  
Safe Operation ◽  
Trailing Edge ◽  
Damage And Failure ◽  
Turbine Model

Flashback and self-ignition in the premixing zone of typical gas turbine swirl combustors in lean premixed operation are immanent risks and can lead to damage and failure of components. Thus, steady combustion in the premixing zone must be avoided under all circumstances. This study experimentally investigates the flame holding propensity of fuel injectors in the swirler of a gas turbine model combustor with premixing of H2-NG-air-mixtures under atmospheric pressure and proposes a model to predict the limit for safe operation. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). A cylindrical duct and a window in the swirler made of quartz glass allow the application of optical diagnostics (OH* chemiluminescence and Planar Laser Induced Fluorescence of the OH radical (OH-PLIF)) inside the swirler. The fuel-air-mixture was ignited with a focused single laser pulse during steady operation. The position of ignition was located inside the swirler in proximity to a fuel injection hole. If the flame was washed out of the premixing zone not later than four seconds after the ignition the operation point was defined as safe. Operation points were investigated at three air mass flows, three air ratios, two air preheat temperatures (573 K, 673 K) and 40 to 100 percent per volume hydrogen in the fuel composed of hydrogen and natural gas. The determined safety limit for atmospheric pressure yields a similarity rule based on a critical Damköhler number. Application of the proposed rule at conditions typical for gas turbines leads to these safety limits for the A2EV burner: With the TEIs the swirler can safely operate with up to 80 percent per volume hydrogen content in the fuel at an air ratio of two. With the JIC injector safe operation at stoichiometric conditions and 95 percent per volume hydrogen is possible.

Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2-Air-Mixtures

2016 ◽  
Author(s):  
Matthias Utschick ◽  
Daniel Eiringhaus ◽  
Christian Köhler ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
High Speed ◽  
Air Flow ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Injector ◽  
Trailing Edge ◽  
Fuel Concentration ◽  
Turbine Model

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2-air-mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally. The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with High-speed-Particle-Image-Velocimetry (PIV) and Highspeed-Laser-Induced-Fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2-air-mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation. We notice flashback in the core flow due to Combustion Induced Vortex Breakdown (CIVB) and Turbulent upstream Flame Propagation (TFP) near the wall dependent on the injector type. The Flashback Resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states. The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in oder to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.

Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2–Air Mixtures

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Matthias Utschick ◽  
Daniel Eiringhaus ◽  
Christian Köhler ◽  
Thomas Sattelmayer
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
High Speed ◽  
Air Flow ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Injector ◽  
Trailing Edge ◽  
Fuel Concentration ◽  
Turbine Model

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2–air mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally. The A2EV swirler concept exhibits a hollow, thick-walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow injector (JICI)). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector (TEI)). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with high-speed particle image velocimetry (PIV) and high-speed laser-induced fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2–air mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation. We notice flashback in the core flow due to combustion-induced vortex breakdown (CIVB) and turbulent flame propagation (TFP) near the wall dependent on the injector type. The flashback resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states. The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in order to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.

Insertion of Electrostatically Charged Fuel Atomization Technology Into a U.S. Navy Shipboard Gas Turbine Engine

2004 ◽  
Author(s):  
David P. Guimond ◽  
Matthew E. Thomas ◽  
Roberto DiSalvo ◽  
Adam Elliot ◽  
D. Scott Crocker
Keyword(s):  
Numerical Modeling ◽  
Gas Turbine ◽  
System Integration ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Research Effort ◽  
Injection System ◽  
Particulate Emissions ◽  
Fuel Injector ◽  
Electrostatic Charging

Recent breakthroughs in the field of hydrocarbon fuel electrostatic charging techniques have now permitted the opportunity for the Navy to consider implementing this technology into shipboard gas turbines. This research effort is focused toward electrostatic atomization insertion into a U.S. Navy Shipboard Rolls Royce Corporation 501-K research engine at the Naval Surface Warfare Center, Carderock Division (NSWCCD). Specific milestones achieved thus far include: (a) Spray demonstration of an electrostatically boosted 501-K gas turbine fuel injector prototype at fuel flows from 40 PPH to 250 PPH. (b) Electrostatic charging effect measurements on the droplet size and patternation of a 501-K simplex atomizer configuration. (c) Numerical modeling of the influence electrostatic charging has on secondary atomization breakup and predicted particulate emissions. This paper documents results associated with injector conceptual design, electrode integration, atomization measurements, numerical modeling and fuel injection system integration. Preliminary results indicate electrostatic boosting may be capable of reducing particulate emissions up to 80% by inserting the appropriate fuel injector.

Influence of Fuel Injection Location in a Small Radial Swirler Low NOx Combustor for Micro Gas Turbine Applications

2019 ◽  
Author(s):  
Gordon E. Andrews ◽  
Su Kim
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Micro Gas Turbine ◽  
Optimum Position ◽  
Pilot Fuel ◽  
Wall Injection ◽  
Injection Location

Abstract The influence of fuel injection location in a low NOx (1) micro-gas turbine [MGT] in the ∼50kWe (kW electric) size range was investigated, for NG and propane, to extend the power turn down using a pilot fuel injector. The low NOx main combustor (1) was a radial swirler with vane passage fuel injection and had ultra-low NOx emissions of 3ppm at 15% O2 at 1800K with natural gas, NG at a combustion intensity of 11.2 MW/m2bara (MW thermal). This was a 40mm diameter outlet eight bladed radial swirler in a 76mm diameter combustor, investigated at 740K air temperature at atmospheric pressure. However, power turn down was poor and the present work was undertaken to determine the optimum position of pilot fuel injection that would enable leaner mixtures to be burned at low powers. Central injection of pilot fuel was investigated using 8 radial outward holes. This was compared with pilot fuel injected at the 76mm wall just downstream of the 40mm swirler outlet. It was show that the central injection pilot was poor with a worse weak extinction than for radial passage fuel injection. The 76mm outlet wall injection was much more successful as a pilot fuel location and had a weak extinction of 0.18Ø compared with 0.34Ø for vane passage fuel injection. NOx emissions were higher for wall fuel injection, but were still relatively low at 16ppm at 15% oxygen for natural gas. This indicates that wall fuel injection could be combined with vane passage fuel injection to improve the micro-gas turbine low NOx performance across the power range.

scholarly journals Two-Phase Flow Phenomena in Gas Turbine Compressors with a Focus on Experimental Investigation of Trailing Edge Disintegration

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 91
Author(s):  
Adrian Schlottke ◽  
Bernhard Weigand
Keyword(s):  
Experimental Investigation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Two Phase Flow ◽  
Droplet Diameter ◽  
Air Flow ◽  
Diameter Distribution ◽  
Phase Flow ◽  
Trailing Edge ◽  
Two Phase

Two-phase flow in gas turbine compressors occurs, for example, at heavy rain flight condition or at high-fogging in stationary gas turbines. The liquid dynamic processes are independent of the application. An overview on the processes and their approach in literature is given. The focus of this study lies on the experimental investigation of the trailing edge disintegration. In the experiments, shadowgraphy is used to observe the disintegration of a single liquid rivulet with constant liquid mass flow rate at the edge of a thin plate at different air flow velocities. A two side view enables calculating droplet characteristics with high accuracy. The results show the asymptotic behavior of the ejected mean droplet diameters and the disintegration period. Furthermore, it gives a detailed insight into the droplet diameter distribution and the spreading of the droplets perpendicular to the air flow.

Performance Prediction of Gas Turbine Under Different Strategies Using Low Heating Value Fuel

2013 ◽  
Author(s):  
Edson Batista da Silva ◽  
Marcelo Assato ◽  
Rosiane Cristina de Lima
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Equivalence Ratio ◽  
Safe Operation ◽  
Engine Operation ◽  
Heating Value ◽  
Gasification Process ◽  
Surge Margin ◽  
And Performance ◽  
Industrial Gas Turbine

Usually, the turbogenerators are designed to fire a specific fuel, depending on the project of these engines may be allowed the operation with other kinds of fuel compositions. However, it is necessary a careful evaluation of the operational behavior and performance of them due to conversion, for example, from natural gas to different low heating value fuels. Thus, this work describes strategies used to simulate the performance of a single shaft industrial gas turbine designed to operate with natural gas when firing low heating value fuel, such as biomass fuel from gasification process or blast furnace gas (BFG). Air bled from the compressor and variable compressor geometry have been used as key strategies by this paper. Off-design performance simulations at a variety of ambient temperature conditions are described. It was observed the necessity for recovering the surge margin; both techniques showed good solutions to achieve the same level of safe operation in relation to the original engine. Finally, a flammability limit analysis in terms of the equivalence ratio was done. This analysis has the objective of verifying if the combustor will operate using the low heating value fuel. For the most engine operation cases investigated, the values were inside from minimum and maximum equivalence ratio range.

Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Experimental Studies ◽  
Temperature Variations ◽  
Auto Ignition ◽  
Chamber Temperature ◽  
Transient Events ◽  
Significant Effort

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Development and Integration of the Dual Fuel Combustion System for the MGT Gas Turbine Family

2021 ◽  
Author(s):  
Bernhard Ćosić ◽  
Frank Reiss ◽  
Marc Blümer ◽  
Christian Frekers ◽  
Franklin Genin ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Distribution System ◽  
Gas Turbines ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Liquid Fuels ◽  
Dual Fuel ◽  
Gaseous Fuels ◽  
Supply And Distribution ◽  
Industrial Gas Turbines

Abstract Industrial gas turbines like the MGT6000 are often operated as power supply or as mechanical drives. In these applications, liquid fuels like 'Diesel Fuel No.2' can be used either as main fuel or as backup fuel if natural gas is not reliably available. The MAN Gas Turbines (MGT) operate with the Advanced Can Combustion (ACC) system, which is capable of ultra-low NOx emissions for gaseous fuels. This system has been further developed to provide dry dual fuel capability. In the present paper, we describe the design and detailed experimental validation process of the liquid fuel injection, and its integration into the gas turbine package. A central lance with an integrated two-stage nozzle is employed as a liquid pilot stage, enabling ignition and start-up of the engine on liquid fuel only. The pilot stage is continuously operated, whereas the bulk of the liquid fuel is injected through the premixed combustor stage. The premixed stage comprises a set of four decentralized nozzles based on fluidic oscillator atomizers, wherein atomization of the liquid fuel is achieved through self-induced oscillations. We present results illustrating the spray, hydrodynamic, and emission performance of the injectors. Extensive testing of the burner at atmospheric and full load high-pressure conditions has been performed, before verification within full engine tests. We show the design of the fuel supply and distribution system. Finally, we discuss the integration of the dual fuel system into the standard gas turbine package of the MGT6000.

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