Showing papers by "Vasudevan Raghavan published in 2012"
TL;DR: In this article, the interaction of micron-sized coal particles entrained into lean methane-air premixed flames was investigated and the effects of different coal dust concentrations (10−300g/m 3 ) entrained in the mixture of methane-Air at three lean equivalence ratios, ϕ, of 0.75, 0.80 and 0.85, on the laminar burning velocity were studied experimentally.
51 citations
TL;DR: In this paper, three thermocouples placed along the symmetry plane of the wedge cross-section at various heights from the apex (lowermost, middle and top) are used to record the transient temperature data.
38 citations
TL;DR: In this paper, numerical simulations of the evaporation of stationary, spherical, two-component liquid droplets in a laminar, atmospheric pressure, forced convective hot-air environment are presented.
23 citations
TL;DR: In this paper, a comprehensive numerical model has been developed to analyze the isolated sodium droplet combustion in a mixed convective environment, where the governing equations for mass, momentum, species and energy conservation have been solved in axisymmetric cylindrical coordinates using the Finite Volume Method (FVM).
13 citations
11 citations
Journal Article•
24 Jan 2012-World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering
TL;DR: In this article, stationary hotwire measurements are carried out to investigate the characteristics of a round free jet in its potential core region (0 ≤ x/d ≤ 10), calculated based on the jet exit mean v locity and the nozzle diameter.
Abstract: In this work, stationary hot-wire measurements are carried out to investigate the characteristics of a round free jet in its potential core region (0 ≤ x/d ≤ 10). Measurements are carried out on an incompressible round jet for a range of Reynolds numbers from 4000 to 8000, calculated based on the jet exit mean v locity and the nozzle diameter. The effect of flow velocity on the d velopment characteristics of the jet in the core region is an alyzed. Timeaveraged statistics, spectra of velocity and its hi gher order moments are presented and explained . Keywords—Contoured nozzle, hot-wire anemometer, Reynolds number, velocity fluctuations, velocity spectra.
10 citations
TL;DR: In this paper, the influence of coflow and partial air premixing on liquid petroleum gas (LPG) flames in a lab-scale co-flow burner is investigated.
Abstract: Investigation of the influence of coflow and partial air premixing on liquid petroleum gas (LPG) flames in a lab-scale co-flow burner is presented. Primary air is supplied along with LPG in the inner core, and secondary air is supplied through the annulus region of the burner. Digital images are analyzed to study the flame shape, color, height, radius, and qualitative laminar flame speed. Concentrations of product gases and emission species are measured using a digital gas analyzer. Results indicate that in a dual air stream configuration, the partial premixing is optimum at % primary air value of around 45%.
9 citations
Journal Article•
TL;DR: In this article, the authors deal with an experimental investigation of the flame characteristics of premixed Liquefied Petroleum Gas (LPG) -air mixtures with different equivalence ratios on a multi-hole matrix burner.
Abstract: This paper deals with an experimental investigation of the flame characteristics of premixed Liquefied Petroleum Gas (LPG) - air mixtures with different equivalence ratios on a multi-hole matrix burner. Lowest possible fuel-lean mixing conditions are envisaged. Results show that the flame pattern changes into four different types which are oscillatory flames in the middle region, flames with oscillations along the centerline, flames with very little oscillations and stable flames from all the holes. Species concentration measurements are performed with the help of gas analyzer and the results show that the concentrations of carbon-monoxide and oxygen decreases, whereas that of carbon-dioxide and nitric oxide increases with increase in the volumetric flow rate of LPG and air mixture. In addition to this, temperature measurements are carried out using a K-type thermocouple over the burner surface at different heights. Temperature contours for each plane have been presented.
8 citations
TL;DR: In this article, an experimental and numerical investigation of unconfined methane-oxygen laminar premixed flames was conducted using pure methane and pure oxygen mixtures having different equivalence ratios.
Abstract: Numerical and experimental investigations of unconfined methane-oxygen laminar premixed flames are presented. In a lab-scale burner, premixed flame experiments have been conducted using pure methane and pure oxygen mixtures having different equivalence ratios. Digital photographs of the flames have been captured and the radial temperature profiles at different axial locations have been measured using a thermocouple. Numerical simulations have been carried out with a C2 chemical mechanism having 25 species and 121 reactions and with an optically thin radiation sub-model. The numerical results are validated against the experimental and numerical results for methane-air premixed flames reported in literature. Further, the numerical results are validated against the results from the present methane-oxygen flame experiments. Visible regions in digital flame photographs have been compared with OH isopleths predicted by the numerical model. Parametric studies have been carried out for a range of equivalence rati...
8 citations
TL;DR: In this article, the authors investigated the combined effects of downstream surface (over fire region) temperature conditions and angular orientation of condensed fuel surface, on the flame characteristics and compared the differences in the structure of the laminar diffusion flames.
7 citations
TL;DR: In this article, the authors present numerical simulations of a core methane jet diffusion flame with a fuel lean mixture (consisting of methane and hydrogen, in different proportions) in the co-flow.
TL;DR: In this article, the effects of axial vibrations of a tubular burner on the characteristics of laminar premixed methane-air flames are investigated, and the effect of the frequency and amplitude of the burner vibrations on the flame height oscillations are studied.
Abstract: Mechanical vibrations in a burner are found to affect the characteristics of premixed flames. In the present experimental investigation, the effects of axial vibrations of a tubular burner on the characteristics of laminar premixed methane-air flames are investigated. The effect of the frequency and amplitude of the burner vibrations on the flame height oscillations are studied. At a low frequency of around 10 Hz, no effect of vibrations on flame characteristics is observed. At frequencies higher than 10 Hz, the amplitude of flame height oscillations is found to increase with increase in both frequency and amplitude of burner vibrations for the range of frequencies and amplitudes considered.
TL;DR: In this article, the effects of axial vibrations on the characteristics of laminar diffusion flames are investigated systematically and the amplitude of flame height oscillations is found to increase with increase in both frequency and amplitude of burner vibrations.
Abstract: Mechanical vibrations introduced in diffusion flame burners significantly affect the flame characteristics. In this experimental study, the effects of axial vibrations on the characteristics of laminar diffusion flames are investigated systematically. The effect of the frequency and amplitude of the vibrations on the flame height oscillations and flame stability is brought out. The amplitude of flame height oscillations is found to increase with increase in both frequency and amplitude of burner vibrations. Vibrations are shown to enhance stability of diffusion flames. Although flame lifts-off sooner with vibrations, stability of the flame increases.
TL;DR: In this article, a thermodynamic model for predicting the vaporization characteristics of binary and ternary hydrocarbon fuel droplets under atmospheric pressure and normal gravity conditions is presented, which employs activity coefficients based on UNIFAC group contribution method.
Abstract: The present study presents a thermodynamic model for predicting the vaporization characteristics of binary and ternary hydrocarbon fuel droplets under atmospheric pressure and normal gravity conditions. The model employs activity coefficients based on UNIFAC group contribution method and evaluates the vapor-liquid equilibrium of binary and ternary droplets. The gas-phase properties have been evaluated as a function of temperature and mixture molecular weight. The model has been validated against the experimental data available in literature. The validated model is used to predict the vaporization characteristics of binary and ternary fuel droplets at atmospheric pressure under normal gravity. Results show multiple slopes in the droplet surface regression indicating preferential vaporization of fuel components based on their boiling point and volatility. The average evaporation rate is dictated by the ambient temperature and also by composition of the mixture.
TL;DR: In this paper, an axisymmetric numerical reactive flow model, with C2 detailed mechanism for describing methane oxidation in air and an optically thin radiation sub-model, is used in simulations.
Abstract: Abstract Interactions of fuel-rich and fuel-lean mixtures and formation of interlinked multiple flame zones are observed in gas turbines and industrial furnaces. For fundamentally understanding such flames, numerical investigation of heat and mass transport, and chemical reaction processes, in laminar, counter flowing partially premixed rich and lean streams of methane and air mixtures, is presented. An axisymmetric numerical reactive flow model, with C2 detailed mechanism for describing methane oxidation in air and an optically thin radiation sub-model, is used in simulations. The numerical results are validated against the experimental results from literature. The equivalence ratios of counter flowing rich and lean reactant streams and the resulting strain rates have been varied. The effect of these parameters on the flame structure is presented. For a given rich and lean side equivalence ratios, by varying the strain rates, triple, double and single flame zones are obtained.