Investigation on Mixing Characteristics of Methane Fuel in Low Emission Combustor

2020 ◽  
Author(s):  
Enhui Liu ◽  
Xiao Liu ◽  
Hongtao Zheng ◽  
Jinghe Lu ◽  
Zhihao Zhang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Fuel Injection ◽  
Near Field ◽  
Velocity Ratio ◽  
Pollutant Emission ◽  
Windward Side ◽  
Leeward Side ◽  
Low Emission ◽  
Mixing Characteristics

Abstract With the increasingly environmental problems and strict pollutant emission limits, pollutant emission has become a critical consideration for gas turbine. Mixing uniformity index of fuel-air has a significant effect on NOx emission. Previous works conducted basic research on mixing mechanism based on jet in crossflow, while few people studied a single real swirler channel in gas turbine combustor. The present work aims to bridge this gap and investigates the effects of fuel injection from the windward and leeward sides on the fuel concentration distribution and mixing uniformity index, based on a typical radical swirler channel. The qualitative analysis of velocity field and vortices structure and the quantitative analysis of velocity ratio and uniformity index are carried out. Due to the presence of sharp corner at the inlet of swirler, a recirculation zone is formed by the flow separation. The recirculation zone at the leeward side decreases the flow velocity and increases the area and time for fuel-air mixing. The velocity ratio plays a key role in the characteristics of flow and mixing. Under the same inlet conditions, the effective velocity ratio (R = 40) in the near field of the leeward side is about 10 times that of windward side (R = 4), and the maximum jet depth can be achieved in the near field. Therefore, the outlet uniformity index on the windward and leeward sides are 38.85% and 49.43%, respectively. From the perspective of mixing uniformity, fuel injection from the leeward side is beneficial to realize quick mixing in short distance. The present study is expected to provide insightful information for understanding mixing characteristics of methane fuel in low emission combustor.

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 Testing of a FuelFlex Dry-Low-NOx Micromix Combustor for Industrial Gas Turbine Applications With Variable Hydrogen Methane Mixtures

2019 ◽  
Author(s):  
H. H.-W. Funke ◽  
N. Beckmann ◽  
S. Abanteriba
Keyword(s):  
Gas Turbine ◽  
Experimental Studies ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
Pollutant Emission ◽  
Pure Hydrogen ◽  
Negative Effects ◽  
Low Emission ◽  
Combustion Properties ◽  
Fuel Mixtures

Abstract The negative effects on the earth’s climate make the reduction of the potent greenhouse gases carbon-dioxide (CO2) and nitrogen oxides (NOx) an imperative of the combustion research. Hydrogen based gas turbine systems are in the focus of the energy producing industry, due to their potential to eliminate CO2 emissions completely as combustion product, if the fuel is produced from renewable and sustainable energy sources. Due to the difference in the physical properties of hydrogen-rich fuel mixtures compared to common gas turbine fuels, well established combustion systems cannot be directly applied for Dry Low NOx (DLN) hydrogen combustion. The paper presents initial test data of a recently designed low emission Micromix combustor adapted to flexible fuel operation with variable fuel mixtures of hydrogen and methane. Based on previous studies, targeting low emission combustion of pure hydrogen and dual fuel operation with hydrogen and syngas (H2/CO 90/10 vol.%), a FuelFlex Micromix combustor for variable hydrogen methane mixtures has been developed. For facilitating the experimental low pressure testing the combustion chamber test rig is adapted for flexible fuel operation. A computer-controlled gas mixing facility is designed and installed to continuously provide accurate and homogeneous hydrogen methane fuel mixtures to the combustor. An evaluation of all major error sources has been conducted. In the presented experimental studies, the integration-optimized FuelFlex Micromix combustor geometry is tested at atmospheric pressure with hydrogen methane fuel mixtures ranging from 57 vol.% to 100 vol.% hydrogen in the fuel. For evaluating the combustion characteristics, the results of experimental exhaust gas analyses are applied. Despite the design compromise, that takes into account the significantly different fuel and combustion properties of the applied fuels, the initial results confirm promising operating behaviour, combustion efficiency and pollutant emission levels for flexible fuel operation. The investigated combustor module exceeds 99.4% combustion efficiency for hydrogen contents of 80–100% in the fuel mixture and shows NOx emissions less than 4 ppm corrected to 15 vol.% O2 at the design point.

Dynamics of Large-Scale Structures for Jets in a Crossflow

1999 ◽  
Vol 121 (3) ◽  
pp. 577-587 ◽  
Author(s):  
F. Muldoon ◽  
S. Acharya
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Computational Study ◽  
Near Field ◽  
Velocity Ratio ◽  
Leeward Side ◽  
Dynamic Features ◽  
Mean Velocity ◽  
Large Scale Structures ◽  
Scale Structures

Results of a three-dimensional unsteady computational study of a row of jets injected normal to a crossflow are presented with the aim of understanding the dynamics of the large-scale structures in the region near the jet. The jet to crossflow velocity ratio is 0.5. A modified version of the computer program (INS3D), which utilizes the method of artificial compressibility, is used for the computations. Results obtained clearly indicate that the near-field large-scale structures are extremely dynamic in nature, and undergo breakup and reconnection processes. The dynamic near-field structures identified include the counterrotating vortex pair (CVP), the horseshoe vortex, wake vortex, wall vortex, and shear layer vortex. The dynamic features of these vortices are presented in this paper. The CVP is observed to be a convoluted structure interacting with the wall and horseshoe vortices. The shear layer vortices are stripped by the crossflow, and undergo pairing and stretching events in the leeward side of the jet. The wall vortex is reoriented into the upright wake system. Comparison of the predictions with mean velocity measurements is made. Reasonable agreement is observed.

Modeling of Gas Turbine Fuel Nozzle Spray

1995 ◽  
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 2-D 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 air-assist 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 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 present 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.

Further Studies of Alternative Jet Fuels

2009 ◽  
Author(s):  
Christopher J. Mordaunt ◽  
Seong-Young Lee ◽  
Vickey B. Kalaskar ◽  
Amy Mensch ◽  
Robert J. Santoro ◽  
...  
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Combustion Instability ◽  
Combustion Efficiency ◽  
Liquid Fuels ◽  
Pollutant Emission ◽  
Fischer Tropsch ◽  
Mixing Processes

Future gas turbine technology may require that liquid fuels play an additional role as a coolant over a wide range of combustion-chamber operating conditions. Additionally, in order to satisfy greater efficiency and performance goals, gas turbine operating temperatures and pressures are steadily increasing. Given the desire to reduce dependence on foreign fuels and that current hydrocarbon fuels, such as JP-8, are prone to thermal or catalytic decomposition at such elevated conditions, there is great interest in utilizing alternatively-derived liquid fuels. The successful development of a versatile, multiple-use fuel must achieve the desired operational characteristics of high combustion efficiency, excellent combustion stability, acceptable pollutant emission levels, and compatibility with current engine seals. Combustion instability represents a critical area of concern for future gas turbine engines that may burn alternative fuels. Combustion instability is characterized by large, unsteady combustion-chamber pressure oscillations which occur at the characteristic frequencies associated with the acoustic modes of the combustor. The occurrence of combustion-driven instabilities is closely tied to the details of the injection and fuel-air mixing processes, the heat release characteristics, and the degree to which heat release rate couples with the acoustics of the combustor. Additionally, the efficiency and emissions characteristics are also largely determined by the fuel injection, atomization, and mixing processes associated with combustion. As fuel properties and composition vary, effects on combustion efficiency and emissions, especially the formation of nitrogen oxides (NOx) and soot, can be expected. Therefore, changes in these processes attributed to differing fuel properties can have a dramatic affect on the combustion characteristics and require careful consideration through a well-coordinated combustion research program. The current study investigates whether a coal-based aviation fuel, JP-900, which has the required thermal stability attributes, also satisfies the engine combustion requirements. Additionally, a Fischer-Tropsch fuel and a volumetric 50/50 blend of JP-8 and the Fischer-Tropsch fuel are studied. Previous studies of coal-based fuels have shown that soot production can be a significant problem due to the higher aromatic content than found in conventional fuels. However, improvements in the fuel refinement processes have helped reduce this problem. Experiments included in this current research effort involve studying the combustion instability patterns, the pollutant emission levels, and sooting propensity of coal-based and Fischer-Tropsch fuels as compared to JP-8. The experimental setup consists of an optically-accessible model gas turbine dump combustor, with provisions for laser extinction measurements, which utilizes a Delavan hollow-cone pressure atomizer for fuel injection.

Preliminary Study of Low Emission Gas Turbine Combustor With Airblast Fuel Atomizer

1976 ◽  
Vol 98 (1) ◽  
pp. 15-22
Author(s):  
K. Yamanaka ◽  
K. Nagato
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Tube Wall ◽  
Combustion Stability ◽  
Exhaust Emission ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Low Emission ◽  
New Type ◽  
Preliminary Study

Recent papers describe that an airblast fuel atomizer is very effective for reducing emissions from a gas turbine and this type of fuel injector is being applied to practical engines. This paper deals with the new type of airblast fuel atomizer AFIT which comes from “Airblast Fuel Injection Tube” that makes fuel to break up into droplets by atomizing air at several small holes on the tube wall and fuel is well mixed with atomizing air instantly at the exits of holes. Regarding this AFIT, the fuel spray characteristics, combustion stability which is usually narrow for the combustor with an airblast fuel atomizer at lower engine speeds and exhaust emission levels are experimented and its effectiveness is discussed.

Combustion Control by Vortex Breakdown Stabilization

2002 ◽  
Vol 128 (4) ◽  
pp. 679-688 ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Peter Flohr ◽  
Ephraim J. Gutmark
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Fuel Injection ◽  
Vortex Breakdown ◽  
Full Scale ◽  
Operating Conditions ◽  
Scale Model ◽  
Recirculation Region ◽  
Pressure Pulsations ◽  
Secondary Fuel

Flame anchoring in a swirl-stabilized combustor occurs in an aerodynamically generated recirculation region which is a result of vortex breakdown (VBD). The characteristics of the recirculating flow are dependent on the swirl number and on axial pressure gradients. Coupling with downstream pressure pulsations in the combustor affects the VBD process. The present paper describes combustion instability that is associated with vortex breakdown. The mechanism of the onset of this instability is discussed. Passive control of the instability was achieved by stabilizing the location of vortex breakdown using an extended lance. The reduction of pressure pulsations for different operating conditions and the effect on emissions in a laboratory scale model atmospheric combustor, in a high pressure combustor facility, and in a full scale land-based gas-turbine are described. The flashback safety, one of the most important features of a reliable gas turbine burner, was assessed by CFD, water tests, and combustion tests. In addition to the passive stabilization by the extended lance it enabled injection of secondary fuel directly into the recirculation zone where the flame is stabilized. Tests were conducted with and without secondary fuel injection. Measurements and computations optimized the location of the extended lance in the mixing chamber. The effect of variation of the amount of secondary fuel injection at different equivalence ratios and output powers was determined. Flow visualizations showed that stabilization of the recirculation zone was achieved. Following the present research, the VBD stabilization method has been successfully implemented in engines with sufficient stability margins and good operational flexibility. This paper shows the development process from lab scale tests to full scale engine tests until the implementation into field engines.

Dynamics of Large-Scale Structures for Jets in a Crossflow

1998 ◽  
Author(s):  
Frank Muldoon ◽  
Sumanta Acharya
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Computational Study ◽  
Near Field ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Leeward Side ◽  
Mean Velocity ◽  
Large Scale Structures ◽  
Scale Structures

Results of a three dimensional unsteady computational study of a row of jets injected normal to a cross-flow are presented with the aim of understanding the dynamics of the large scale structures in the region near the jet. The jet to cross-flow velocity ratio is .5. A modified version of the computer program (INS3D) which utilizes the method of artificial compressibility is used for the computations. Results obtained clearly indicate that the near field large scale structures are extremely dynamical in nature, and undergo breakup and reconnection processes. The dynamical near field structures identified include the counter rotating vortex pair (CVP), the horseshoe vortex, wake vortex, wall vortex and the shear layer vortex. The dynamical features of these vortices are presented in this paper. The CVP is observed to be a convoluted structure interacting with the wall and horseshoe vortices. The shear layer vortices are stripped by the crossflow, and undergo pairing and stretching events in the leeward side of the jet. The wall vortex is reoriented into the upright wake system. Comparison of the predictions with mean velocity measurements is made. Reasonable agreement is observed.

Development of a Jet-Stabilized Low-Emission Combustor for Liquid Fuels

2015 ◽  
Author(s):  
Anton Zizin ◽  
Oliver Lammel ◽  
Michael Severin ◽  
Holger Ax ◽  
Manfred Aigner
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Soot Formation ◽  
Flame Stabilization ◽  
Liquid Fuels ◽  
Cfd Modeling ◽  
Design Parameters ◽  
Spray Cone ◽  
Low Emission ◽  
Flame Shape

In this work the ongoing development of a jet-stabilized FLOX®(Flameless Oxidation)-type low-emission combustor for liquid fuels is described. The desired application of this concept is a micro gas turbine range extender for next generation car concepts. Diesel DIN EN 590 was used to operate the combustor, which is very similar to other fuels like bio-diesel, light heating oil and kerosene and therefore provides a link to other gas turbine applications in power generation. The investigation of flame stabilization of jet flames as well as fuel atomization, spray dispersion and evaporation is essential for the design of an effective and reliable combustor for liquid fuels. An axisymmetric single-nozzle combustion chamber was chosen for the initial setup. A variety of burner configurations was tested in order to investigate the influence of different design parameters on the flame shape, the flame stability and emissions. Two pressure atomizers and one air-blast atomizer were combined with two types of air nozzles and two different burner front plates (axisymmetric and off-centered jet nozzle). Finally, a twelve nozzle FLOX® combustor with pre-evaporator was designed and characterized. The combustor was operated at atmospheric pressure with preheated air (300° C) and in a range of equivalence ratios φ between 0.5 and 0.95 (λ = 1.05–2). The maximum thermal power was 40 kW. For each combustor configuration and operating condition the flame shape was imaged by OH*-chemiluminescence, together with an analysis of the exhaust gas emissions. Laser sheet imaging was used to identify the spray geometry for all axisymmetric combustors. Wall temperatures were measured for two configurations using temperature sensitive paints, which will be utilized in future CFD modeling. The results show a dependence of NOx emissions on the flame’s lift-off height, which in turn is defined by the spray properties and evaporation conditions. The tendency to soot formation was strongly dependent on the correlation of the recirculation zone to the spray cone geometry. In particular, strong soot formation was observed when unevaporated droplets entered the recirculation zone.

Injection of Kerosene Into a High-Temperature and High-Speed Air Crossflow

2020 ◽  
Author(s):  
Wang Yulan ◽  
Mu Yong ◽  
Fan Xiongjie ◽  
Zhao Qianpeng ◽  
Xu Gang
Keyword(s):  
High Temperature ◽  
Weber Number ◽  
High Speed ◽  
Fuel Injection ◽  
Air Flow ◽  
Windward Side ◽  
Leeward Side ◽  
Inertia Force ◽  
Fuel Flow ◽  
Jet Trajectory

Abstract The jet of kerosene into high-temperature and high-speed air crossflow was studied experimentally, to study the characteristics of penetration and evaporation in afterburner. A fuel injection bar with a 0.6 mm diameter plain orifice was used in the experiment. The angle between jet and air flow was 90°. The tests were conducted at atmospheric pressure. The air temperature was between 400 °C to 800 °C, and the air velocity increased from 100 m/s to 250 m/s, which was close to the working condition of the afterburner. The jet flow rate also increased from 5 kg/h to 40 kg/h. Fuel-PLIF was used to visualize the trajectory and structure of the jet trajectory. It was observed that the core region of the jet (the largest volume flow) was close to the windward side, and the leeward side of the jet had a relatively wide peripheral area due to the shear of the high-speed airflow. The jet trajectory is affected by viscosity force, inertia force and surface tension in different proportion under high-temperature and high-speed airflow. The jet penetration is related to the momentum ratio (q), air flow Weber number (We0), and aerodynamic Weber number (Wea). In experiment, q ranged from 2 to 236, We0 ranged from 72 to 735, and Wea ranged from 0.36–41. The relationship between penetration to these variables was established. The plume width and evaporation distance under different test conditions were compared. The results show that the plume width varied within a narrow range in high-temperature and high-speed air crossflow, and the fuel evaporation distance was much more affected by the fuel flow than the airflow condition, basically in a linear correlation with fuel flow. The results are of great significance to the size design and arrangement of the stabilizers in afterburners.

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