Showing papers by "Vasudevan Raghavan published in 2013"
TL;DR: In this article, a two-phase numerical simulation of transient vaporization of a moving spherical water droplet is presented to study the evaporation characteristics of moving water droplets under conditions typically observed in nuclear reactor during a loss of coolant accident.
42 citations
TL;DR: In this article, a two-phase numerical model is presented to simulate transient vaporization of a spherical two-component liquid fuel droplet, which considers variation of thermo-physical properties in both liquid and vapor phases, as functions of temperature and species concentrations.
19 citations
TL;DR: In this article, a semi-empirical analysis concerning the mass burning rate characteristics of biodiesel-diesel blends is presented based on the data measured using porous sphere experiments, and a correlation for evaluating instantaneous burning rate of BDI blended fuels has been proposed for practical applications.
Abstract: Blended fuels such as biodiesel–diesel blends are being extensively used in practical devises such as engines. The burning characteristics of blended fuels are quite different than that of the individual fuels and need to be understood. In this study, a semiempirical analysis concerning the mass burning rate characteristics of biodiesel–diesel blends is presented based on the data measured using porous sphere experiments. Finally, a correlation for evaluating instantaneous burning rate of biodiesel–diesel blended fuels has been proposed for practical applications. Further, using this correlation, transient burning characteristics of blended biodiesel–diesel droplet in suspended mode have been studied for different blend compositions. Multiple modes of burning regimes are identified for the blended fuels.
9 citations
TL;DR: In this article, three dust samples namely, wheat flour, Pittsburgh seam coal and powder river basin coal, are tested with both fresh and weathered dust samples and the results show that the weathered sample is expected to ignite at a different hot plate temperature as compared to that of a fresh sample, when tested in a standard test method (ASTM E 2021).
Abstract: Weathering of coal and other cellulosic dusts occur due to the process of wetting and subsequent drying, or by subjecting them to a temperature higher than the ambient temperature for prolonged time periods. The first type of weathering occurs in a wetted storage. The second type of weathering occurs when a dust processing unit stores and maintains the dust deposit at an elevated temperature. As a result of weathering, the physical and thermal properties of the dust may change. Therefore, the weathered dust sample is expected to ignite at a different hot plate temperature as compared to that of a fresh sample, when tested in a standard test method (ASTM E 2021). In this study, three dust samples namely, wheat flour, Pittsburgh seam coal and powder river basin coal, are tested. These dust samples are subjected to one or both types of weathering. Thermogravimetric analysis and standard ignition tests are carried out with both fresh and weathered dust samples. Estimation of the activation energies and reactivity, and measurement of the minimum surface temperature for the onset of ignition have been carried out for all the cases. The implications of the observed results on industrial safety related to combustible dust layers are discussed.
8 citations
01 Jan 2013
TL;DR: In this article, the effects of holding geometry on spontaneous combustible dust ignition are studied using lab-scale experiments and a mathematical model and the results predicted by the mathematical model compare well with the trends shown by the experimental data.
Abstract: Effects of holding geometry on spontaneous combustible dust ignition are studied. Spontaneous ignition of coal dust deposited on a flat hot surface (1D case) and trapped between two hot surfaces (2D geometry), forming the shape of a wedge, is analyzed using lab-scale experiments and a mathematical model. The solution is obtained by assuming a temperature polynomial of third (one-dimensional) and fifth order (two-dimensional), in the energy conservation equation where the source term is defined using a 1-step Arrhenius type equation. The angle in wedge configuration is varied from 10° to 150° in steps of 10°. The results predicted by the mathematical model compare well with the trends shown by the experimental data. Consequent safety measures associated with dust layers trapped in corners or wedges are discussed.
7 citations
1 citations
TL;DR: In this article, the effect of small scale turbulence on the development of the round jet is experimentally studied using hot wire anemometry, where small scale structures present in the jet slowed down the jet mixing characteristics and there by retards the decay rate in the near field region.
Abstract: Abstract The effect of the small scale turbulence on the development of the round jet is experimentally studied using hot wire anemometry. The small scale turbulence is generated by placing a grid having grid spacing near the nozzle exit. Experiments are carried out for the range of Reynolds numbers (4000, 6000 and 8000). It is observed that the small scale structures present in the jet slows down the jet mixing characteristics and there by retards the decay rate in the near-field region. It is observed that in the grid disturbed jets, the ratio of the turbulent kinetic energy to mean-flow kinetic energy is relatively lower than that of the undisturbed jet without any grid. From the spectral analysis, it is observed that the grid disturbed jets has higher energy content than that of the undisturbed jets.