An Experimental Study on Methane/Oxygen-Air Combustion With a Rapidly Mixed Type Tubular Flame Burner

2011 ◽  
Author(s):  
Baolu Shi ◽  
Tatsuya Kowari ◽  
Daisuke Shimokuri ◽  
Satoru Ishizuka
Keyword(s):  
Experimental Study ◽  
Diffusion Flame ◽  
Turbulent Combustion ◽  
Mixed Type ◽  
Diffusion Flames ◽  
Kinetic Mechanism ◽  
Pure Oxygen ◽  
Extinction Limit ◽  
Wide Range ◽  
Flame Burner

Methane/oxygen-air combustion has been attempted by using a rapidly mixed type tubular flame burner with four slits, from two of which a fuel is injected and from another two an oxidizer is injected. The oxygen concentration (molar) in the oxygen-air oxidizer has been varied from 21% (air) to 100% (pure oxygen). Results show that uniform tubular flame combustion can be obtained for a wide range of equivalence ratios, if the oxygen molar concentration in the oxygen-air oxidizer is less than about 50%. Above 50%, however, very intense turbulent combustion occurs frequently and the circular-shaped tubular flame is deformed as oval-shaped for most equivalence ratios. The uniform tubular flame range is reduced and quite limited in the vicinity of lean condition. Detailed observations show that for pure (or near pure) oxygen oxidizer, two diffusion flames are established between the fuel and oxidizer streams at the exits of the fuel slits, which prevents fuel from mixing with oxygen, resulting in a violent turbulent combustion downstream the slits. With use of a burner with smaller slit width, however, formation of the diffusion flame is inhibited and a uniform tubular flame can be established, although still limited close to the lean extinction limit. To fully understand the flame characteristics above, the burning velocities are calculated for various equivalence ratios as well as for various oxygen concentrations in the oxygen-air oxidizer using the CHEMKIN PREMIX code with the GRI kinetic mechanism.

Direct Numerical Simulation of Turbulent Spray Combustion

2000 ◽  
Author(s):  
J. Réveillon
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Diffusion Flame ◽  
Turbulent Combustion ◽  
Diffusion Flames ◽  
Combustion Model ◽  
Two Phase ◽  
Complex Interactions ◽  
The Rich ◽  
Global And Local

Abstract Turbulent combustion of two-phase flows is studied by 2D direct numerical simulation. A spray of droplets is injected inside a jet with a preheated coflow. Triple flames appear to represent the global structure of the flame around the spray. Attention is focused upon global and local flame structures and droplet histories. A whole range of combustion phenomena are observed and described. The observed prevailing occurrence, for example, of the rich premixed flame compared to the diffusion flame is of great importance for any turbulent combustion model which must accurately estimate the heat release rate. This prevailing structure depends strongly on the droplet size and combustion. A competition between premixed and diffusion regimes may also occur. It has been shown that in some cases, local clusters of droplets are able either to cross the main flame front and burn in pure oxidizer or to break through the diffusion flame. It is observed that very complex interactions can emerge locally between premixed flames, diffusion flames and droplets.

D211 Pure Oxygen Combustion with a Rapidly-Mixed Type Tubular Flame Burner

2010 ◽  
Vol 2010 (0) ◽  
pp. 293-294
Author(s):  
Satoru Ishizuka ◽  
Daisuke Shimokuri ◽  
Tatsuya Kowari ◽  
Bao Lu Shi ◽  
Jie Hu
Keyword(s):  
Mixed Type ◽  
Pure Oxygen ◽  
Flame Burner

scholarly journals An Experimental Study on the Flame Structure Control in a Rapidly Mixed Type Tubular Flame Burner

2012 ◽  
Vol 78 (785) ◽  
pp. 185-193
Author(s):  
Daisuke SHIMOKURI ◽  
Yoshiro ETO ◽  
Kimiaki KIMURA ◽  
Naohiko GOKITA ◽  
Enrei WANG ◽  
...  
Keyword(s):  
Experimental Study ◽  
Mixed Type ◽  
Flame Structure ◽  
Structure Control ◽  
Flame Burner

Experimental and Numerical Studies of Ethanol Flames

2006 ◽  
Author(s):  
Priyank Saxena ◽  
Forman A. Williams
Keyword(s):  
Diffusion Flame ◽  
Radiation Effects ◽  
Diffusion Flames ◽  
Premixed Flames ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Detailed Chemistry ◽  
Partially Premixed ◽  
Partially Premixed Flame ◽  
Fuel Stream

This paper reports results of experimental and numerical investigations of ethanol-air diffusion flames and partially premixed flames at an air-side strain rate of 100 s−1, in a counterflow geometry. The diffusion flame consists of prevaporized fuel, with mole fraction of 0.3, diluted with nitrogen in the fuel stream, and plant air as the oxidizer stream. The partially premixed flame includes prevaporized fuel in air partially premixed to an equivalence ratio of 2.3 in the fuel stream, and plant air as the oxidizer stream. Temperature profiles were measured by thermocouple, and concentration profiles of the stable species C2H5OH, CO, CO2, H2, H2O, O2, N2, CH4, C2H6, and C2H2+C2H4 were measured by gas chromatography of samples withdrawn by a fine probe. Computational studies involved numerical integration of the conservation equations, with detailed chemistry, transport and radiation effects included, to calculate the structures of the counterflow flames. A chemical-kinetic mechanism consisting of 235 elementary steps and 46 species with recently published reaction-rate parameters was developed and tested for these flames. The proposed mechanism, which produces reasonable agreement with previous measurements of ignition, freely propagating premixed flames and diffusion-flame extinction, also yields good agreement with much of the present data, although there are quite noticeable differences between predicted and measured peak C2H6 concentrations. These differences and the desirability of additional tests of other predictions and of tests under other conditions motivate further research.

Modeling of Turbulent Combustion Process and Lean Blowout of Diffusion and Premixed Flames Using a Combined Approach

2009 ◽  
Author(s):  
Yu. G. Kutsenko ◽  
A. A. Inozemtsev ◽  
L. Y. Gomzikov
Keyword(s):  
Diffusion Flame ◽  
Turbulent Combustion ◽  
Diffusion Flames ◽  
Premixed Flames ◽  
Combustion Process ◽  
Combustion Model ◽  
Main Zone ◽  
Lean Blowout ◽  
No Formation ◽  
No Emissions

Most of the modern combustor’s designs use staged concepts for reducing thermal NO emissions. Usually, a combustion process takes place inside the main zone, which uses very lean premixed fuel/air mixtures. A diffusion pilot zone supports combustion process inside a lean main zone. Thermal NO formation process takes place predominantly inside hot diffusion flame. So, operation modes of pilot and main zones must be arranged to provide low NO emissions of pilot zone and maintain flame stability inside the main zone simultaneously. In this paper, a new turbulent combustion model is presented. This model allows to model diffusion and premixed flames and takes into account various physical processes, which lead to flame destabilization. The model uses an equation for reaction progress variable. Within the considered approach this equation has two source terms. These terms are responsible for different conditions of combustion process: diffusion flames and premixed flames, and distributed reacting zones. This paper studies the problem, concerning modeling of lean blowout process of diffusion flame front. To test the proposed combustion model we have simulated lean blowout process inside combustion zone of a gas turbine combustor. Good predictions of lean blowout limits were obtained.

A New Assumed PDF Turbulent Combustion Model for Multi-Step Chemistry

2005 ◽  
Author(s):  
Baifang Zuo ◽  
David L. Black ◽  
Clifford E. Smith
Keyword(s):  
Monte Carlo ◽  
Turbulent Combustion ◽  
Diffusion Flames ◽  
Mixture Fraction ◽  
Premixed Flames ◽  
Flame Stabilization ◽  
Combustion Model ◽  
Main Stream ◽  
Wide Range ◽  
Partially Premixed

The effect of turbulence on chemical reactions is known to be important in many gas turbine combustor applications. There are only a few established models that can capture turbulence-combustion interaction in CFD codes, and all of these models are either very expensive (e.g. Monte Carlo PDF model) or limited in what types of flames can be analyzed (e.g. laminar flamelet). Assumed PDF models have been a popular choice because they are inexpensive and can handle all flame types (e.g. diffusion, premixed and partially premixed). However, assumed PDF models are typically restricted to single, one-step global mechanisms; or are a function of species and quickly become computationally expensive. CFD Research Corporation has recently developed and validated a new assumed PDF turbulence chemistry interaction model for multi-step chemistry. The model adopts an assumed, two-variable joint-PDF to model a wide-range of turbulent reacting flows. The two variables defining the PDF are the mixture fraction and reaction progress, representing species diffusion and flame propagation. A significant advantage of this new approach is its wide range of applicability for premixed, diffusion, and partially premixed flames. Allowing more detailed chemistry for species and combustion predictions enables complex chemical reaction processes including pollutant formation, flame ignition, and flame quenching to be studied. The model is also computationally efficient, with only a minor increase in computational expense with either species or number of global reaction steps. The newly developed model was first validated using a diffusion flame from a piloted burner developed at the University of Sydney. Three different methane bulk jet velocities were used to investigate the model’s behavior on turbulent diffusion flames. Simulation data were compared with the experimental measurements and the simulation results performed by Pope (Masri and Pope, 1990) using a velocity-composition joint PDF transport equation solved by the Monte Carlo method. To validate the model on premixed flames, the data of Moreau et al. (Moreau et al., 1974, 1976, 1977) were used. Data were collected on a mixing layer stabilized burner, where the main flow into the combustor was a premixed mixture of methane and air. Parallel to the main stream, a pilot stream of hot combustion products at 2000 K was injected for flame stabilization. The results demonstrate the wide applicability of the new model for practical, turbulent combustion applications.

scholarly journals Evaluation of Emission Model for Diffusion Flame, Rich/Lean, and Premixed Lean Combustors

1993 ◽  
Author(s):  
N. K. Rizk ◽  
H. C. Mongia
Keyword(s):  
Diffusion Flame ◽  
Variable Structure ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Emission Model ◽  
Nox Formation ◽  
Model Calculations ◽  
Lean Combustion ◽  
Wide Range

A recently developed emission model was used to predict the emission characteristics of a gas turbine combustor. The model involves a multiple-step reaction scheme that addresses the breakup of the fuel into an intermediate hydrocarbon compound of variable structure. The reaction rate expressions developed in the present approach simulated the results obtained using a detailed chemical kinetic mechanism over a wide range of operation that is typically encountered in a conventional diffusion flame combustor, as well as low NOx rich/quench/lean, and premixed/prevaporized lean combustion concepts. The modeling of the combustor involves dividing the combustor into a number of reactors representing various combustion and near wall regions of the combustor. The calculations showed that the fuel reaction could proceed at a completely different rate depending on the conditions prevailing in each region of the combustor. The model results also indicated that at idle power mode the initial rate of NOx formation was high. However, due to the subsequent admission of air, no further addition to the NOx concentration was predicted at downstream locations. At high power levels, the fuel rich region near the combustor dome inhibits the formation of NOx. The admission of air in this case brings the fuel/air mixture close to the stoichiometric value causing a significant amount of NOx to form. The model calculations agreed quite well with the measured data of the combustor.

E221 Pure Oxygen Combustion with a Rapidly-Mixed Type Tubular Flame Burner (2^ Report)

2011 ◽  
Vol 2011 (0) ◽  
pp. 313-314
Author(s):  
Syuhei Matsuda ◽  
Tatsuya Kowari ◽  
Bao Lu Shi ◽  
Daisuke Shimokuri ◽  
Satoru Ishizuka
Keyword(s):  
Mixed Type ◽  
Pure Oxygen ◽  
Flame Burner
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