Showing papers by "Vasudevan Raghavan published in 2022"
TL;DR: In this article , the spread of a ground fire over pine needle bed of the Siberian boreal forests (Pinus silvestris) in still air has been reported and careful experiments have been conducted to reveal the effects of the bed width, fuel moisture content, fuel load, and the packing ratio on flame spread rate, temperature distributions in both gas and condensed phases.
Abstract: Systematic experiments and complementing numerical simulations have been reported for the first time to understand the spread of a ground fire over pine needle bed of the Siberian boreal forests (Pinus silvestris) in still air. Using equipment and instrumentations specifically developed for the purpose, careful experiments have been conducted to reveal the effects of the bed width, fuel moisture content, fuel load, and the packing ratio on flame spread rate, temperature distributions in both gas and condensed phases. Temperatures are measured using fine thermocouples fixed at various locations from the bed surface. The surface temperature of the bed during flame propagation has been measured using a micro-thermocouple inserted in a single pine needle in the bed as well as using an infrared (IR) camera. Further, for the first time, the total and radiant heat fluxes from the flame to the bed surface have been measured using compact cooled sensors placed inside the needle bed, over which the flame propagates. In order to understand more about the flow field and flame spread process, a 3D numerical model based on the Fire Dynamics Simulator (FDS) has been used to simulate few of the experiments. The processes governing pine needle pyrolysis, char oxidation, gas phase combustion and radiation have been modeled using simplified approaches reported in literature. The model is capable of predicting experimentally measured flame propagation velocities for most of the cases quite well.
2 citations
TL;DR: In this paper , the ANSYS Fluent model was used to evaluate the flame characteristics of laminar cross-flow non-premixed biogas-air flames established in a boundary layer.
Abstract: This study presents the flame characteristics of laminar cross-flow non-premixed biogas-air flames established in a boundary layer using ANSYS Fluent. The validated numerical model is comprehensive enough to include variable thermo-physical properties, multi-component diffusion, short chemical kinetics mechanism, and optically thin approximation-based radiation model. Fuel is injected at a uniform velocity and the air is supplied perpendicular to it. Predicted and the in-house experimental biogas flames are qualitatively compared in terms of flame extents. The fuel flow rate has been varied from 0.02 m/s to 0.04 m/s to study the effects of power rating on the flame characteristics. At a given fuel flow rate, the airflow rate is incremented in steps to study the effects of forced convection on the characteristics and stability of the flames. Furthermore, the effects of the length of the flat plate upstream of the leading edge of the fuel injector plate on the flame anchoring location have been studied. The structure and characteristics of the reactive boundary layer are explained by using fields of temperature, velocity, mass fractions of major species, stoichiometric equivalence ratio, and Damköhler number. The reactive boundary layer fueled by methane is compared with that of biogas.
TL;DR: In this paper , a multi-slot burner with five fuel slots and six air slots arranged in an alternate manner has been analyzed, where the power rating of the burner is kept as 10 kW and the air flow rate is fixed at 400% of stoichiometric air required for the net fuel flow rate.
Abstract:
Characteristics of impinging flames from a multi-slot burner fueled by synthetic gas is studied using a comprehensive numerical model. A multi-slot burner with five fuel slots and six air slots arranged in an alternate manner has been analyzed. The power rating of the burner is kept as 10 kW and the air flow rate is fixed at 400% of stoichiometric air required for the net fuel flow rate. The numerical model incorporates a short chemical kinetic mechanism, variable thermo-physical properties, full multi-component diffusion, thermal diffusion and a radiation sub-model. The location of the solid surface from the burner exit, primary air in fuel stream, dimensions of solid surfaces and their temperatures have been varied to study the heat flux distributions from impinging flames. Results show that the location of the solid surface from the burner ports and partial premixing affect the heat transfer characteristics. The heat fluxes received by the side and top surfaces depend on the characteristics of neighbouring flames located around the central flame. The heat flux distribution and the net heat flux received by the surface are found to be uniform and optimum at a height of 90 mm from burner exit. Mass fraction of CO is affected by heating height and partial premixing. It remains almost constant for varying temperature of the impinging surfaces. Primary aeration of 20% is found to be optimum for higher net heat flux and lower CO emissions.
01 Jan 2022
TL;DR: In this article, sufficient details of a flame's flow, temperature and species fields are required in order to understand the characteristics of the flame, and the authors propose a method to obtain these details.
Abstract: In order to understand the characteristics of a flame, sufficient details of its flow, temperature and species fields are required.