Characteristics of Partially Premixed Elliptic Burner Flames in Coflow-Velocity Air Streams

2004 ◽  
Author(s):  
P. Hariharan ◽  
S. R. Gollahalli
Keyword(s):  
Aspect Ratio ◽  
Equivalence Ratio ◽  
Peak Temperature ◽  
Baseline Condition ◽  
Flame Height ◽  
Air Velocity ◽  
Exit Velocity ◽  
Partially Premixed ◽  
Air Streams ◽  
Co Emission

This paper presents the results of an extension of the previous study where the effects of jet equivalence ratio and burner geometry on the characteristics of partially premixed propane/hydrogen/air flames at a coflow air velocity of 3 m/s were presented. The results here pertain to the experiments where the coflow velocity was doubled to understand the effects of coflow. Two different burner geometries (Circular, and 3:1 aspect ratio-AR elliptical burners) were used in the experiments with circular burner flames as baseline condition. During the study, the exit velocity was held constant at 20 m/s for all conditions. Stability tests indicated that circular burner flames were more stable than the 3:1AR elliptical burner flames at quiescent conditions. At 6 m/s coflow air velocity, stability of both the circular and the 3:1AR elliptic flames was enhanced. Circular burner flames were longer than 3:1AR elliptical burner flames. Introduction of 6 m/s coflow air velocity reduced the flame height. Global NO and CO emission indices decreased considerably after the introduction of coflow air in both burners. Peak temperature of circular burner flames was higher than that of 3:1AR elliptic burner at all conditions. Inflame concentration measurements were also taken in near-burner (25% flame height), midflame (50% flame height) and far-burner (75% flame height) regions.

Effect of Equivalence Ratio and Burner Geometry on the Characteristics of Laminar Premixed Flames at Moderate Coflow

2004 ◽  
Author(s):  
P. Hariharan ◽  
S. R. Gollahalli
Keyword(s):  
Aspect Ratio ◽  
Equivalence Ratio ◽  
Premixed Flames ◽  
Combustion Efficiency ◽  
Flame Height ◽  
No Production ◽  
Air Velocity ◽  
Burner Flame ◽  
Jet Velocity ◽  
The Stability

The importance of studying laminar premixed flames lies in applications such as gas ranges and ovens, heating appliances and Bunsen burners. With the current demand for large amounts of economical, clean power, there is a need for research in increasing the combustion efficiency. Laminar premixed Propane/Hydrogen/Air flames with 3 m/s coflow and without coflow, with a variation of jet equivalence ratio (JEQ) from 0.5 to 4 for 20 m/s jet velocity, have been studied experimentally to determine the interactions of burner geometry of premixed flames and coflow. Two different burner geometries (circular burner, and 3:1 aspect ratio (AR) burners) were used in the experiments. The stability tests indicated that for 20 m/s jet velocity both at quiescent and coflow conditions the circular burner was more stable than the 3:1AR elliptical burner. Flame height studies indicated that circular burner flames were taller than the 3:1AR elliptical burner flames. However, there was a reduction in flame height when coflow air velocity of 3 m/s was introduced. Temperature profile indicated a higher peak temperature for circular burners followed by elliptical burner, both at quiescent and coflow conditions. The introduction of moderate coflow showed a decrease in NO production rate. In order to explain the structure of the flame in detail and various mechanisms that lead to the explanation of global flame characteristics, inflame concentration measurements were taken in near burner (25% of flame height), mid burner (50% of flame height) and far burner (75% of flame height) regions of the flame.

Analysis of LPG diffusion flame in tube type burner

2019 ◽  
Vol 13 (3) ◽  
pp. 5278-5293
Author(s):  
Vipul Patel ◽  
Rupesh Shah
Keyword(s):  
Diffusion Flame ◽  
Emission Characteristic ◽  
Flame Stability ◽  
Liquefied Petroleum Gas ◽  
Air Velocity ◽  
Length Fraction ◽  
Low Emission ◽  
Tube Type ◽  
Stability Limits ◽  
Co Emission

The present research aims to analyse diffusion flame in a tube type burner with Liquefied petroleum gas (LPG) as a fuel. An experimental investigation is performed to study flame appearance, flame stability, Soot free length fraction (SFLF) and CO emission of LPG diffusion flame. Effects of varying air and fuel velocities are analysed to understand the physical process involved in combustion. SFLF is measured to estimate the reduction of soot. Stability limits of the diffusion flame are characterized by the blowoff velocity. Emission characteristic in terms of CO level is measured at different equivalence ratios. Experimental results show that the air and fuel velocity strongly influences the appearance of LPG diffusion flame. At a constant fuel velocity, blue zone increases and the luminous zone decreases with the increase in air velocity. It is observed that the SFLF increases with increasing air velocity at a constant fuel velocity. It is observed that the blowoff velocity of the diffusion flame increases as fuel velocity increases. Comparison of emission for flame with and without swirl indicates that swirl results in low emission of CO and higher flame stability. Swirler with 45° vanes achieved the lowest CO emission of 30 ppm at Φ = 1.3.

Numerical Analysis of Equivalence Ratio Fluctuations in a Partially Premixed Gas Turbine Combustor Using Large Eddy Simulations

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Ping Wang ◽  
Qian Yu ◽  
Prashant Shrotriya ◽  
Mingmin Chen
Keyword(s):  
Reaction Mechanism ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Premixed Flames ◽  
Large Eddy Simulations ◽  
Combustion Model ◽  
Inlet Channel ◽  
Large Eddy ◽  
Partially Premixed Flames ◽  
Partially Premixed

In the present work, the fluctuations of equivalence ratio in the PRECCINSTA combustor are investigated via large eddy simulations (LES). Four isothermal flow cases with different combinations of global equivalence ratios (0.7 or 0.83) and grids (1.2 or 1.8 million cells) are simulated to study the mixing process of air with methane, which is injected into the inlet channel through small holes. It is shown that the fluctuations of equivalence ratio are very large, and their ranges are [0.4, 1.3] and [0.3, 1.2] for cases 0.83 and 0.7, respectively. For simulating turbulent partially premixed flames in this burner with the well-known dynamically thickened flame (DTF) combustion model, a suitable multistep reaction mechanism should be chosen aforehand. To do that, laminar premixed flames of 15 different equivalence ratios are calculated using three different methane/air reaction mechanisms: 2S_CH4_BFER, 2sCM2 reduced mechanisms and GRI-Mech 3.0 detailed reaction mechanism. The variations of flame temperature, flame speed and thickness of the laminar flames with the equivalence ratios are compared in detail. It is demonstrated that the applicative equivalence ratio range for the 2S_CH4_BFER mechanism is [0.5, 1.3], which is larger than that of the 2sCM2 mechanism [0.5, 1.2]. Therefore, it is recommended to use the 2S_CH4_BFER scheme to simulate the partially premixed flames in the PRECCINSTA combustion chamber.

Temperature Measurements in High-Velocity Air Streams

1945 ◽  
Vol 12 (1) ◽  
pp. A25-A32
Author(s):  
H. C. Hottel ◽  
A. Kalitinsky
Keyword(s):  
Axial Flow ◽  
Extensive Study ◽  
Recovery Factor ◽  
Scale Model ◽  
Kinetic Temperature ◽  
Flat Plates ◽  
Air Velocity ◽  
Theoretical Predictions ◽  
Air Streams ◽  
Thermocouple Junction

Abstract When a stream of air is partially stopped by an inserted temperature probe, the temperature increase due to the conversion of kinetic energy affects the reading of the probe. The fraction of the total kinetic temperature rise which is registered by the probe, i.e., the so-called “recovery factor” of the probe, is a function of a number of variables. Tests dealing with the effect of probe shape and air velocity on this recovery factor, and with the influence of radiation on the accuracy of the measurements, are reported in this paper. Bare-wire probes gave recovery factors of approximately 0.65 in transverse flow and, in axial flow, approached 0.87 as the air velocity increased (in good agreement with theoretical predictions for flow over flat plates). With a spherical enlargement at the thermocouple junction, recovery approached 0.75. Recovery of twisted-wire couples varied from 0.72 to 0.83. A reduced-scale model of the Franz probe was found unsatisfactory after extensive study. Two simpler probes were developed, having high recovery (above 0.98 as velocity approaches sonic) and satisfactory insensitivity to yaw and radiation errors.

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.

scholarly journals Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

2017 ◽  
Author(s):  
Javier Marrero Santiago ◽  
Antoine Verdier ◽  
Alexis Vandel ◽  
Gilles Godard ◽  
Gilles Cabot ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Ignition Process ◽  
Flow Properties ◽  
Air Velocity ◽  
Mean Velocity ◽  
Local Flow ◽  
Ignition Probability ◽  
Piv Measurements ◽  
Mean Values ◽  
Local Equivalence

Laser ignition was investigated in the swirled, confined CORIA Rouen Spray Burner under ultra-lean conditions (Φ=0.61) with n-heptane as the liquid fuel. Ignition probability was calculated for different spark locations and compared to the non-ignited local flow properties. Mean velocity components of the carrier flow were measured by PDA under spray presence and without spray, and are compared to mean values from PIV. PIV measurements provide information on the instantaneous airflow and the total strain rate. Fuel droplet size-velocity data was measured by PDA. Toluene-PLIF images were acquired to provide information on the local equivalence ratio and the flammability factor. Results show that the outer recirculation zone (ORZ) has a flammability factor close to 1 and the highest ignition probability (~80%). These results have a high correlation with the air velocity field and turbulent kinetic energy. Instantaneous equivalence ratio images and shear rate-velocity fields give important information on local segregation of the flow properties that help to understand the ignition process. The present work provides a useful database for numerical simulations and industry, plus new insight on spray ignition.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4674

Combustion Properties of Partially-Premixed Turbulent Flames of Soy Methyl Ester and Diesel Blends

2010 ◽  
Author(s):  
Nikhil S. Dhamale ◽  
Ramkumar N. Parthasarathy ◽  
Subramanyam R. Gollahalli
Keyword(s):  
Reynolds Number ◽  
Methyl Ester ◽  
Alternative Energy ◽  
Turbulent Flame ◽  
Energy Resource ◽  
Turbulent Flames ◽  
Flame Height ◽  
Combustion Properties ◽  
Partially Premixed ◽  
Soy Methyl Ester

Soy methyl ester (SME) is a biofuel that is a renewable alternative energy resource and is produced by the transesterification of soy oil; it is carbon-neutral and low in sulphur content. The objective of this study was to document the combustion characteristics of blends of SME and No 2 diesel fuel in a partially-premixed turbulent flame environment. The experiments were conducted at an initial equivalence ratio of 7 and three Reynolds numbers (based on the injector diameter and the bulk burner-exit velocity of the air/fuel mixture): 2700, 3600 and 4500. Three blends, B25, B50 and B75 corresponding to 25, 50 and 75% volume concentration of SME were studied. The liquid fuel was completely vaporized and mixed with air before exiting the burner. The radiative heat fraction measured in the SME flames was lower than the corresponding value in pure diesel flames and increased with Reynolds number. The global emission measurements indicated that the NOx emissions from the SME-diesel blend flames were lower than those from the pure diesel flame. At quarter and half flame height the temperature peaked at the edge of the flame where as for three quarters the temperature peaked at the centerline of the flame. In-flame NOx concentrations decreased with an increase in Reynolds number. The CO emission index decreased with the increase in the SME concentration in the fuel blend and decreased with the increase in Reynolds number.

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