Simultaneous Equivalence Ratio and Flame Structure Measurements in Multipoint Injectors Using PLIF

2008 ◽  
Author(s):  
Frederic Grisch ◽  
Mikael Orain ◽  
Eric Jourdanneau ◽  
Christian Guin
Keyword(s):  
Equivalence Ratio ◽  
Flame Structure

Emission Measurements and CH* Chemiluminescence of a Staged Combustion Rig for Stationary Gas Turbine Applications

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Warren G. Lamont ◽  
Mario Roa ◽  
Scott E. Meyer ◽  
Robert P. Lucht
Keyword(s):  
Combustion Zone ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Exhaust Gas ◽  
Staged Combustion ◽  
High Pressure Turbine ◽  
Transverse Jet ◽  
Sampling Probe ◽  
Good Agreement

An optically accessible combustion rig was constructed to study the combustion characteristics of a reactive jet in a vitiated crossflow. The rig features two staged combustion zones. The main combustion zone is a swirl stabilized dump combustor. The second combustion zone, which is axially downstream from the main combustion zone, is formed by a transverse jet injecting either fuel or a premixed fuel/air mixture into the vitiated stream. The rig was designed to investigate the transverse jet conditions, equivalence ratio, and momentum ratios that produce low NOx and give an adequate temperature rise before the simulated high pressure turbine. A water-cooled sampling probe extracts exhaust gas downstream for emission measurements. As a baseline, the main combustion zone was fired without the transverse jet and the results compare closely to the work of previous researchers. The emission survey with the transverse jet found several conditions that show a benefit of staging compared to the baseline of firing only the main combustion zone. The flame structure from the transverse jet was captured using high speed CH* chemiluminescence, which shows the extent of the flame front and its penetration depth into the vitiated stream. The chemiluminescence images were averaged and compared to the Holdeman correlation, which showed good agreement for injection with fuel only but poorer agreement when premixed.

The Structure of Two-Stage Counterflow n-Heptane-Air Flames

2000 ◽  
Author(s):  
S. K. Aggarwal ◽  
H. S. Xue
Keyword(s):  
Strain Rate ◽  
Reaction Zone ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Premixed Combustion ◽  
Premixed Flame ◽  
Partially Premixed Combustion ◽  
Reaction Zones ◽  
Partially Premixed ◽  
Partially Premixed Flame

Partially premixed flames are formed by mixing air (in less than stoichiometric amounts) into the fuel stream prior to the reaction zone, where additional air is available for complete combustion. Such flames can occur in both laboratory and practical combustion systems. In advanced gas turbine combustor designs, such as a lean direct injection (LDI) combustor, partially premixed combustion represents an impotent mode of burning. Spray combustion often involves partially premixed combustion due to the locally fuel vapor-rich regions. In the present study, the detailed structure of n-heptane/air partially premixed flame in a counterflow configuration is investigated. The flame is computed by employing the Oppdif code and a detailed reaction mechanism consisting of 275 elementary reactions and 41 species. The partially premixed flame structure is characterized by two-stage burning or two distinct but synergistically coupled reaction zones, a rich premixed zone on the fuel side and a ‘nonpremixed zone on the air side. The fuel is completely consumed in the premixed zone with ethylene and acetylene being the major intermediate species. The reactions involving the consumption of these species are found to be the key rate-limiting reactions that characterize interactions between the two reaction zones, and determine the overall fuel consumption rate. The flame response to the variations in equivalence ratio and strain rate is examined. Increasing equivalence ratio and/or strain rate to a critical value leads to merging of the two reaction zones. The equivalence ratio variation affects the rich premixed reaction zone, while the variation in strain rate predominantly affects the nonpremixed reaction zone. The flame structure is also characterized in terms of a modified mixture fraction (conserved scalar), and laminar flamelet profiles are provided.

Dynamics and Stability Limits of Syngas Combustion in a Swirl-Stabilized Combustor

2008 ◽  
Author(s):  
Raymond L. Speth ◽  
H. Murat Altay ◽  
Duane E. Hudgins ◽  
Ahmed F. Ghoniem
Keyword(s):  
High Speed ◽  
Equivalence Ratio ◽  
Fluid Dynamic ◽  
Flame Structure ◽  
Low Frequency ◽  
Operating Conditions ◽  
Video Data ◽  
Combustion Dynamics ◽  
Lean Blowout ◽  
Operating Modes

The combustion dynamics, stability bands and flame structure of syngas flames under different operating conditions are investigated in an atmospheric pressure swirl-stabilized combustor. Pressure measurements and high-speed video data are used to distinguish several operating modes. Increasing the equivalence ratio makes the flame more compact, and in general increases the overall sound pressure level. Very close to the lean blowout limit, a long stable flame anchored to the inner recirculation zone is observed. At higher equivalence ratios, a low frequency, low amplitude pulsing mode associated with the fluid dynamic instabilities of axial swirling flows is present. Further increasing the equivalence ratio produces unstable flames oscillating at frequencies coupled with the acoustic eigenmodes. Additionally, a second unstable mode, coupled with a lower eigen-mode of the system, is observed for flames with CO concentration higher than 50%. As the amount of hydrogen in the fuel is increased, the lean flammability limit is extended and transitions between operating regimes move to lower equivalence ratios.

A Numerical Investigation on the Effect of Hydrogen and Syngas Addition on the Ignition of JP-8 Surrogates

2012 ◽  
Author(s):  
Thomas Helma ◽  
S. K. Aggarwal
Keyword(s):  
Numerical Investigation ◽  
Ignition Delay ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Flame Structure ◽  
Flame Temperature ◽  
Kinetic Mechanism ◽  
Smoke Point ◽  
Temperature Profiles ◽  
Two Component

A numerical study is carried out investigating the effect of hydrogen and syngas addition on the ignition of two JP-8 surrogates, a two-component surrogate and a six-component surrogate. This six-component surrogate has previously been found to accurately simulate the smoke point, volatility, flame temperature profiles, and extinction limits of JP-8, while the two component surrogates has been shown to reproduce the flame structure predicted with the six-component surrogate. CHEMKIN 10101 is used to simulate ignition in a closed homogenous reactor under adiabatic and isobaric conditions. The parameters include temperature ranging from 850–1250 K, pressure of 20 atm, and equivalence ratio ϕ = 1.0. The CRECK-0810 kinetic mechanism, involving 341 species and 9173 reactions, is used to model the ignition chemistry. For the conditions studied, the addition of H2 or syngas in small quantities has no effect on the ignition behavior of either the surrogates or their individual components. Addition of H2 or syngas in larger quantities increases and decreases the ignition delay at low and high temperatures, respectively. For the conditions investigated, the ignition behavior of both the surrogates is predominantly determined by the ignition chemistry of n-dodecane.

Liftoff behaviors and flame structure of dimethyl ether jet flame in CH4/air vitiated coflow

2019 ◽  
Vol 233 (8) ◽  
pp. 1039-1046 ◽  
Author(s):  
Wei Fu ◽  
Fengyu Li ◽  
Haitao Zhang ◽  
Bolun Yi ◽  
Yanju Liu ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
High Speed ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
High Speed Photography ◽  
Flame Stability ◽  
Jet Flames ◽  
Jet Flame ◽  
Field Temperature ◽  
Vitiated Coflow

The objective of this paper is to investigate the flame structure and liftoff behaviors of a dimethyl ether central jet in CH4/air vitiated coflow in a coflow burner. The liftoff behaviors of dimethyl ether jet flames in the air flow were studied firstly. The flame stability of the burner was analyzed by measuring the flow field temperature with thermocouples. By changing the coflow rate and CH4 equivalence ratio, the liftoff behaviors of dimethyl ether jet flames under different vitiated coflow environments were discussed. The jet flame structure was also analyzed qualitatively by high-speed photography.

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.

scholarly journals The Effect of Fuel Injection Location on Supersonic Hydrogen Combustion in a Cavity-Based Model Scramjet Combustor

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 193 ◽  
Author(s):  
Eunju Jeong ◽  
Sean O’Byrne ◽  
In-Seuck Jeung ◽  
A. F. P. Houwing
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Flow Direction ◽  
Flame Structure ◽  
Flow Characteristics ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Total Enthalpy ◽  
Scramjet Combustor ◽  
Injection Location

Supersonic combustion experiments were performed using three different hydrogen fuel-injection configurations in a cavity-based model scramjet combustor with various global fuel–air equivalence ratios. The configurations tested were angled injection at 15° to the flow direction upstream of the cavity, parallel injection from the front step, and upstream injection from the rear ramp. Planar laser-induced fluorescence of the hydroxyl radical and time-resolved pressure measurements were used to investigate the flow characteristics. Angled injection generated a weak bow shock in front of the injector and recirculation zone to maintain the combustion as the equivalence ratio increased. Parallel and upstream injections both showed similar flame structure over the cavity at low equivalence ratio. Upstream injection enhanced the fuel diffusion and enabled ignition with a shorter delay length than with parallel injection. The presence of a flame near the cavity was determined while varying the fuel injection location, the equivalence ratio, and total enthalpy of the air flow. The flame characteristics agreed with the correlation plot for the stable flame limit of non-premixed conditions. The pressure increase in the cavity for reacting flow compared to non-reacting flow was almost identical for all three configurations. More than 300 mm downstream of the duct entrance, averaged pressure ratios at low global equivalence ratio were similar for all three injection configurations.

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