Numerical Modeling of Flame Lift-Off Phenomenon in a Combustion Chamber With Three Cylinder Methane Fuel Injector

1992 ◽  
Author(s):  
T. O. Mohieldin ◽  
S. K. Chaturvedi
Keyword(s):  
Flame Structure ◽  
Primary Objective ◽  
Two Dimensions ◽  
Fuel Injector ◽  
Lifted Flame ◽  
Fuel Jet ◽  
Fast Chemistry ◽  
Jet Velocity ◽  
Lift Off ◽  
Langley Research Center

Abstract This work summarizes results for a three cylinder fuel injector that has been adopted as a model for investigating combustion phenomenon in the 8-Foot High Temperature Tunnel (HTT) at NASA Langley Research Center. The primary objective here is to understand the flame lift-off phenomenon in the three cylinder fuel injector geometry in two-dimensions. Three chemistry models, namely fast chemistry, one-step kinetics and two-step kinetics are employed in conjunction with a computational fluid dynamics code to analyze the flame structure and flame lift-off characteristics downstream of the fuel injector. Effects of fuel jet velocity and chemistry model on the flame lift-off phenomenon from the injector surface are analyzed by considering simultaneously the combined convection (outside the cylinders) and conduction (inside the cylinders). Results indicate that as the fuel jet velocity is increased, the flame is transformed from a wrap around configuration to a clearly lifted flame configuration. Of the three chemistry models considered in the present study, only the two-step chemistry model predicts a clearly lifted flame. The ability of the CFD code to predict lifted flame is important since a slightly lifted but stable flame is of paramount importance to the operation of the combustor.

scholarly journals Numerical study of turbulent normal diffusion flame CH4-air stabilized by coaxial burner

2013 ◽  
Vol 17 (4) ◽  
pp. 1207-1219 ◽  
Author(s):  
Zouhair Riahi ◽  
Ali Mergheni ◽  
Jean-Charles Sautet ◽  
Ben Nasrallah
Keyword(s):  
Equivalence Ratio ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Flame Structure ◽  
Premixed Combustion ◽  
Air Jet ◽  
Fuel Jet ◽  
Jet Velocity ◽  
Lift Off

The practical combustion systems such as combustion furnaces, gas turbine, engines, etc. employ non-premixed combustion due to its better flame stability, safety, and wide operating range as compared to premixed combustion. The present numerical study characterizes the turbulent flame of methane-air in a coaxial burner in order to determine the effect of airflow on the distribution of temperature, on gas consumption and on the emission of NOx. The results in this study are obtained by simulation on FLUENT code. The results demonstrate the influence of different parameters on the flame structure, temperature distribution and gas emissions, such as turbulence, fuel jet velocity, air jet velocity, equivalence ratio and mixture fraction. The lift-off height for a fixed fuel jet velocity is observed to increase monotonically with air jet velocity. Temperature and NOx emission decrease of important values with the equivalence ratio, it is maximum about the unity.

Study on lifted flame stabilization under different background pressures

2021 ◽  
pp. 1-19
Author(s):  
Qiushi Qin ◽  
Zhijun Wu ◽  
Alessandro Ferrari
Keyword(s):  
High Speed ◽  
Imaging System ◽  
Experimental Tests ◽  
Combustion Products ◽  
Jet Flow ◽  
Flame Stabilization ◽  
Lifted Flame ◽  
Jet Velocity ◽  
Lift Off ◽  
Pdf Model

Abstract A numerical experimental investigation is presented for a steady methane lifted-flame and a non-reaction jet flow in a co-flow of hot combustion products from lean premixed air/hydrogen combustion. A pressurized vitiated co-flow burner has been employed to study the methane lifted flame and non-reaction jet flow under different background pressures. The lift-off height has been measured with a high-speed camera, and the central jet flow velocity has been measured by means of a Schlieren imaging system. The experimental results show that the lift-off height decreases for an increment in the background pressure and in the co-flow temperature. As far as the experimental tests on the non-reaction jet flow is concerned, the jet velocity becomes extinct faster as the background pressure rises. The evolution of the jet velocity has been proved to be another important factor that affects the lift-off height under different background pressures, in addition to the fuel autoignition delay. The simulation data led with a RANS/PDF model show that an increment in the background pressure makes the temperatures increase and induces a brighter yellow part of lifted flame, which leads to more soot production. This proves that the flame is not completely premixed. On the other hand, the Schlieren images of a non-reaction jet flow highlight that the flame is partially premixed, since the edge of the jet is not well defined, as the jet penetration increases with time.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2005 ◽  
Vol 127 (1) ◽  
pp. 187-196 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven nonpremixed turbulent flames.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2001 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

Abstract The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty, direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven, non-premixed turbulent flames.

Effect of CO2 Dilution on Flame Structure and Soot and NO Formations in CH4-Air Nonpremixed Flames

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Arindam Samanta ◽  
Ranjan Ganguly ◽  
Amitava Datta
Keyword(s):  
Flame Structure ◽  
Flame Length ◽  
Nonpremixed Flames ◽  
Fuel Flow Rate ◽  
Heating Value ◽  
Flame Radiation ◽  
Fuel Flow ◽  
Fuel Jet ◽  
Jet Velocity ◽  
Fuel Stream

In the present work, a numerical analysis has been presented to show the variations in flame structure, flame radiation, and formations of soot and NO in methane-air laminar nonpremixed flames with different CO2 dilutions of fuel. It is observed that the flame length reduces as the dilution of the fuel stream by CO2 increases while maintaining constant fuel jet velocity at the burner tip. However, the flame length remains almost unchanged with different blends of CH4 and CO2 if the burner loading (i.e., fuel flow rate×heating value of fuel) is kept constant. Both soot and NO formations decrease monotonically when the CO2 fraction in the fuel is increased. The radiation from the flame also decreases when CO2 dilution of the fuel is increased, particularly, when the fuel jet velocity is maintained constant.

Lifted flame structure of coannular jet flames in a triple port burner

2011 ◽  
Vol 33 (1) ◽  
pp. 1195-1201 ◽  
Author(s):  
Kazuhiro Yamamoto ◽  
Shinya Kato ◽  
Yusuke Isobe ◽  
Naoki Hayashi ◽  
Hiroshi Yamashita
Keyword(s):  
Flame Structure ◽  
Jet Flames ◽  
Lifted Flame

Comparison of the Flame Characteristics of Turbulent Circular and Elliptic Jets in a Crossflow

2002 ◽  
Vol 124 (3) ◽  
pp. 197-203 ◽  
Author(s):  
S. R. Gollahalli ◽  
D. Pardiwalla
Keyword(s):  
Flame Structure ◽  
Flux Ratio ◽  
Major Axis ◽  
Minor Axis ◽  
No Production ◽  
Sampling System ◽  
Computer Data ◽  
Rate Of Increase ◽  
Jet Velocity ◽  
Lower Limits

This study was directed to understand the coupling effects of the noncircular geometry of the burner and a crossflow on the combustion of gas jets. This paper compares the characteristics of turbulent propane jet flames from circular (diameter=0.45 cm) and elliptic (major axis/minor axis=3) burners of equivalent exit area in a crossflow. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access and capable of wind speeds up to 12.5 m/s. The burners were fabricated with metal tubes. Instrumentation included a Pt-Pt/13% Rh thermocouple, a quartz-probe gas sampling system, chemiluminescent and nondispersive infrared analyzers, a video-recorder, and a computer data acquisition system. The measurements consisted of the upper and lower limits of jet velocity for a stable flame, flame configuration, and visible length. Flame structure data including temperature profiles and concentration profiles of CO2,O2, CO, and NO were obtained in a two-zone flame configuration (at jet to crossflow momentum flux ratio=0.11), where a planar recirculation exists in the wake of the burner tube followed by an axisymmetric tail. The relative emission indicators of CO and NO were estimated from the composition data. Results show that the upper and lower limits of the fuel jet velocity increase with the crossflow velocity for all burners, and the rate of increase is highest for the elliptic burner with its minor axis aligned with the crossflow. That burner configuration also produces the longest flame. The relative emission indicators show that the CO production is lower and NO production is higher with elliptic burners than with circular burners in crossflow.

Dynamic simulation of the motion of capsules in pipelines

1995 ◽  
Vol 286 ◽  
pp. 201-227 ◽  
Author(s):  
J. Feng ◽  
P. Y. Huang ◽  
D. D. Joseph
Keyword(s):  
Lift Force ◽  
Two Dimensions ◽  
Inertial Forces ◽  
Stress Distributions ◽  
Three Stages ◽  
Heavy Crude ◽  
Lift Off ◽  
Experimental Values ◽  
Transient Oscillations ◽  
Core Flows

In this paper we report results of two-dimensional simulations of the motion of elliptic capsules carried by a Poiseuille flow in a channel. The numerical method allows computation of the capsule motion and the fluid flow around the capsule, and accurate evaluation of the lift force and torque. Results show that the motion of a capsule which is heavier than the carrying fluid may be decomposed into three stages: initial lift-off, transient oscillations and steady flying. The behaviour of the capsule during initial lift-off and steady flying is analysed by studying the pressure and shear stress distributions on the capsule. The dominant mechanism for the lift force and torque is lubrication or inertia or a combination of the two under different conditions. The lift-off velocity for the ellipse in two dimensions is compared with experimental values for cylindrical capsules in pipes. Finally, the mechanisms of lift for capsules are applied to flying core flows, and it is argued that inertial forces are responsible for levitating heavy crude oil cores lubricated by water in a horizontal pipeline.

Autoignition and flame lift-off behavior of a fuel jet mixing with turbulent hot air coflow

2020 ◽  
Author(s):  
Suhui Li ◽  
Wenkai Qian ◽  
Haoyang Liu ◽  
Guijun Liu ◽  
Min Zhu
Keyword(s):  
Jet Mixing ◽  
Hot Air ◽  
Fuel Jet ◽  
Lift Off

Flow Field Derived Equivalent Reactor Networks for Accurate Chemistry Simulation in Gas Turbine Combustors

2009 ◽  
Author(s):  
Scott A. Drennan ◽  
Chen-Pang Chou ◽  
Anthony F. Shelburn ◽  
Devin W. Hodgson ◽  
Cheng Wang ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Flame Structure ◽  
Cost Effective ◽  
Fuel Injector ◽  
Accurate Analysis ◽  
Detailed Chemistry ◽  
Reactor Networks ◽  
Detailed Kinetics ◽  
Time Required

A method has been developed in which the flow field predicted by Computational Fluid Dynamics (CFD) is automatically condensed into an Equivalent Reactor Network (ERN), composed of well stirred reactors, allowing rapid and accurate analysis of emissions. This paper presents the effectiveness of utilizing an ERN that is a direct abstraction of the computational flow field for combustion analysis. The CFD results are divided into reactors using various filters on flow-field variables to construct an ERN that represents the 3-D combustor flow field and flame structure. Detailed kinetics can then be used in ERN simulations to analyze effects of fuel composition and operating condition on emissions. The technique is applied to a commercial industrial gas turbine combustor fuel injector and compared against experimental emissions results. Sensitivity of emissions predictions to different parameters in the network extraction is also presented. Parameter variations in fuel flow rate are applied to the ERN to obtain relative impacts of fuel-air ratio on the emissions of NOx without requiring new CFD solutions. This automatic approach has been found to reduce the time required to construct and analyze flow field derived ERNs with detailed chemistry by 90%. A local calculation of Damko¨hler number, important for stability analysis, is also presented. This calculation also uses abstracted information from the CFD flow field and detailed-kinetics simulations for more accurate, cost-effective analysis.

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