Flame Structure and Pollutant Emission Characteristics of a Burning Kerosene Spray With Injection of Diluents

The effects of injection rate of gaseous additives on the characteristics of liquid spray flames

A comparative study of the structure of burning sprays of number 2 and SRC-II fuel oils

An experimental study of combustion characteristics and structure of interacting 2, 3, and 5 propane jets in a cross flow is presented. The separation distance between the burners was set at 8, 12, and 16 exit diameters. The ratio of jet momentum flux to cross flow momentum flux was varied over a range of 44-390. Flame length, blowout stability, temperature, radiation emission, and concentrations of CO, NO, and O2 are measured. The effects of number of jets, their separation distance, and their geometrical arrangement relative to cross flow, on flame length, radiation and stability characteristics are examined. The changes in the radial profiles of temperature, and concentrations of CO, O2, and NO are studied as functions of separation distance and ratio of jet momentum flux to cross flow momentum flux of 3-jet flames. The range between the upper and lower stability limits of the jet velocity of lifted flames in cross flow is higher for multiple-jet flames than for single-jet flames. A third limi...

Model calculation of steady upward flame spread over a thin solid in reduced gravity

The effect of pressure on the flame structure in the wake of a burning hydrocarbon droplet

Abstract-Data are presented on the structure of propane diffusion flames burning in a concentric stream of air, with and without the addition of diluents (carbon dioxide and nitrogen) to the fuel jet and air stream. The flame length and the fraction of heat release radiated are documented as functions of diluent concentrations in fuel jet and air stream. The effects of diluent addition on the temperature profiles, composition profiles showing species CO2, H2O, CO, N2, O2, C3H8,NO and pyrolysis species of C3H8 and axial profiles of radiant power emitted are also presented. The results show that the diluents reduce flame length, stability, radiation and concentrations of nitric oxide in the flames. The effects of diluents on the flame structure can be attributed primarily to the changes in concentrations of various species rather than to the changes in temperature. The problems of using flue gas recirculation in large combustion systems are indicated.

Buoyancy effects on the flame structure in the wakes of burning liquid drops

The stability, radiation, and structure of laminar axisymmetric CH4/NH3/air diffusion flames have been studied using photographic images, spectrally resolved measurements of flame radiation, and the spatial distribution of temperature and major species mole fractions obtained by spontaneous Raman scattering. The fit procedure for the Raman spectra of NH3 includes a hitherto unquantified overtone feature, whose inclusion in the fit significantly improves the NH3 fraction obtained. Nitrogen is used to replace NH3 to separate chemical effects of NH3 addition from those due to dilution. The results show that NH3 addition drastically reduces radiation from carbon-containing species, with progressively increasing strong chemiluminescence from excited NO2 and NH2, indicating a substantial change in flame chemistry. While the Rayleigh/Mie scattering from soot particles is still observed in the Raman spectra at 28% NH3 addition, 46% NH3 in the fuel is seen to suppresses soot formation effectively. The measured axial and radial profiles of temperature and major species indicate a substantial contribution from radial transport from the reaction zone, seriously complicating the relation between composition, mixture fraction, and the corresponding equilibrium temperature and mole fractions.

Flame structure and radiation characteristics of CO/H2/CO2/air turbulent premixed flames at high pressure

IN a recent communication1 by one of us, substantial evidence was given of the suppression of the D-line sodium radiation in hydrogen flames by additives—such as carbon dioxide and other polyatomic molecules—which likewise inhibit the chemiluminescence of manganese-promoted calcium oxide in contact with the flames. It was considered that the effect of the additive was greatly to reduce the concentration of hydrogen atoms, the presence of which is necessary for the chemiluminescent effect referred to.

The aspect ratio effects of elliptic co-flow on the structure of a turbulent propane diffusion flame from a circular tube have been presented. Pollutant emission, flame radiation, flame structure, and soot concentration have been measured. The fuel jet exit Reynolds number is 2700, and the exit Reynolds number for the co-flow is 4010 and 8025 based on the minor and major axis respectively. The results are compared with the measurements from the experiments in a circular co-flow, which is the baseline condition for the present study. The pollution characteristics and the structure of the flame in the elliptic co-flow are significantly different from those in the circular co-flow. The NO emission is higher and the CO emission is lower in the elliptic co-flow. Elliptic co-flow flame produces less soot than circular co-flow flame. The study shows that the elliptic co-flow aspect ratio has a controlling influence on various combustion characteristics. In general, it is seen that as the aspect ratio of the elliptic co-flow is increased from 2:1 to 4:1, the entrainment of air increases and thus the combustion characteristics are enhanced. Compared to 2:1 AR co-flow flames, the flames with 4:1 AR co-flow are more stable, have a lower flame height, produce more NO and less CO, the flame peak temperature is higher, are less sooty, and radiate less. Flame spectral measurements show that the 4:1 aspect ratio flames produce more OH, CH, C2 and H2O radicals in the near-burner region than the 2:1 co-flow flames as a result of higher fuel oxidation.

A mathematical model was developed to predict radial and axial temperature profiles in an induction-coupled plasma torch. The model employed temperature dependent physical properties and included radiation heat loss. Temperature fields based on the model were calculated for an atmospheric pressure argon plasma. Computed radial temperature profiles were in agreement with experimental profiles reported in the literature. The gas flow rate and flow pattern in the torch did not greatly affect the radial temperature profiles in the hottest region of the torch under ordinary operating conditions, also in agreement with experiment. A one-dimensional analysis was developed which predicted these hot-spot profiles accurately. The plasma model was also found to accurately predict distribution of energy losses from the plasma. Based on the equilibrium current density and temperature profiles provided by the model, the question of the existence of local thermodynamic equilibrium was re-examined. It was concluded that equilibrium is closely approached in the high-temperature central portion of the plasma, in agreement with previous investigators; however, nonequilibrium conditions can exist in the region of high temperature gradient at the plasma edge.

The effects of elliptic co-flow on the structure of a turbulent propane diffusion flame have been presented. The interaction of the fuel jet and coflow shear layer enhances the mixing behavior of the flow-field, which tends to improve the combustion characteristics of diffusion flames. Non-axisymmetric exit jet geometries are characterized by better mixing and increased fluid entrainment. Better mixing results in higher fluid entrainment in the jet core, which is desirable for the low pollution from a diffusionally controlled combustion environment. In the present study, the interaction of an elliptic jet co-flow with a propane jet flame issued from a circular tube burner has been studied. Pollutant emission, flame radiation, flame structure, and soot concentration have been measured. The exit Reynolds number of the fuel jet is 5670 and the exit Reynolds number for the coflow is 2700 based on the minor diameter. The results are compared with the measurements from the experiments in a circular co-flow which is the base line condition for the present study. The pollution characteristics and the flame structure of the flame in the elliptic co-flow are significantly different from those in the circular coflow. The NO emission is higher and the CO emission is lower in the elliptic co-flow. Elliptic co-flow flame produces less soot than circular co-flow flame. The elliptic co-flow jet grows quicker than that of circular co-flow and the center line velocity decay is more rapid in elliptic co-flow flame C dcfc E El r Ucf Uj w X NOMENCLATURE Circular co-flow Circular co-flow jet diameter Elliptic co-flow Emission Index (g/kg of fuel) Radial distance Co-flow jet exit velocity Fuel jet exit velocity Soot concentration (g/cc) Axial distance

Nitrogen oxides emissions in turbulent hydrogen jet non-premixed flames: Effects of coaxial air and flame radiation

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.