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De Azevedo C.G.,Brazilian Space Research Institute | de Andrade J.C.,Brazilian Space Research Institute | de Souza Costa F.,Brazilian Space Research Institute
Energy | Year: 2015

Environmental concerns and uncertainties in oil supply motivate the development of new combustion technologies using biofuels. Flameless combustion is a promising technology capable of operating with high thermal efficiency, reduced pollutant emissions and low operational costs. This work presents an experimental study of a flameless compact combustion system for burning hydrous ethanol, 96%v/v using a blurry injector to atomize the fuel. Relatively uniform sprays with small droplets and narrow cone angles were obtained, favoring the operation of the flameless combustor. The flameless combustion regime was observed under several operational conditions, through the determination of temperature profiles and flue-gas composition. For a 2kW thermal input, the flameless regime occurred with excess air coefficients 1.65-2.45, temperatures 690-921°C, NOx emissions 2.55-3.08ppm and UHC (unburned hydrocarbons) emissions 1.43-1.10ppm. For a 4kW thermal input, the flameless regime occurred with excess air coefficients 1.21-1.80, temperatures 810-1002°C, NOx emissions 1.98-2.16ppm and UHC emissions 1.53-2.25ppm. The temperature profiles measured during the flameless regime were relatively homogeneous inside the combustion chamber with very low emissions, compared to the conventional flame regime. © 2015 Elsevier Ltd. Source


De Azevedo C.G.,Brazilian Space Research Institute | De Andrade J.C.,Brazilian Space Research Institute | Costa F.D.S.,Brazilian Space Research Institute
Renewable Energy | Year: 2016

Atomization plays an important role in combustion and propulsion systems, including applications in transportation and power generation. The uncertainties in oil supply and environmental concerns motivate the development of new combustion technologies using biofuels, capable of operating with high thermal efficiency, low operational cost and reduced environmental impact. Flameless combustion is a promising technology that allows the reduction of pollutant emissions with high combustion efficiency. This work describes the characteristics of soy methyl ester (SME) sprays produced by a blurry injector. Characteristics droplet diameters, discharge coefficients, air-to-liquid mass ratios, air and liquid pressures and spray cone angles were experimentally determined. Three nozzle tip configurations have been tested: cylindrical, conical and conical-cylindrical. All nozzles configurations have presented high atomization efficiency, yielding relatively small characteristics diameters (SMD and MMD) and narrow spray cone angles, favoring its application in compact combustion systems. © 2015 Elsevier Ltd. All rights reserved. Source


Azevedo C.G.,Brazilian Space Research Institute | De Andrade J.C.,Brazilian Space Research Institute | De Souza Costa F.,Brazilian Space Research Institute
Atomization and Sprays | Year: 2013

This paper analyses the effects of nozzle geometry on sprays produced by a blurry injector using water as test fluid. Significant differences on the sprays formed by the injector were observed for cylindrical, conical-cylindrical, and conical nozzle exit configurations. Several operational characteristics were determined, including average droplet diameters, discharge coefficients, air-to-liquid mass ratios, and spray cone angles. Conical and cylindrical-conical nozzles have shown similar behavior and higher atomization efficiency, yielding smaller Sauter mean diameters and mass median diameters than the cylindrical nozzle. Nevertheless, they presented lower discharge coefficients and required higher airto- liquid mass ratios, air flow rates, and air exit velocities than the cylindrical nozzle. © 2013 by Begell House, Inc. Source


Toledo R.C.,Brazilian Space Research Institute | Travelho J.S.,Brazilian Space Research Institute | An C.Y.,Brazilian Space Research Institute | Bandeira I.N.,Brazilian Space Research Institute
Microgravity Science and Technology | Year: 2014

The study of heat transfer during the free fall of PbSn droplets is important to optimize the alloy solidification conditions in drop tubes. In this paper a model of heat transfer by conduction is applied in the solidification of PbSn eutectic alloys in a 3 m length drop tube installed at Associate Laboratory of Sensors and Materials of the Brazilian Space Research Institute (LAS/INPE). Drop tubes are one of the most suitable and low cost options to provide a microgravity environment on the ground. © 2014, Springer Science+Business Media Dordrecht. Source


An C.Y.,Brazilian Space Research Institute | Toledo R.C.,Brazilian Space Research Institute | Boschetti C.,Brazilian Space Research Institute | Ribeiro M.F.,Brazilian Space Research Institute | Bandeira I.N.,Brazilian Space Research Institute
Microgravity Science and Technology | Year: 2014

The Brazilian Microgravity Program is mainly based on experiments carried out on sounding rockets. A solidification furnace, capable of producing temperatures up to 900 C, was developed to process metal and semiconductor alloys in microgravity environment. This paper describes a solidification experiment made in this furnace during a parabolic flight, with two eutectic alloys. The behavior of the eutectic alloys PbSn with 26.1 Pb at. % composition, and PbTe with 10.9 Pb at. % composition were presented and compared with laboratory solidifications carried out in the same furnace and thermal cycle. It was concluded that the formation of dendritic structures in PbSn alloy is related to the presence of sedimentation and convective flow during solidification, and the size of these structures is connected to the solidification time. Thus, in the microgravity alloy, there was no formation of dendritic structures and the profile of solute distribution remained constant throughout the sample. For the PbTe eutectic alloy the microgravity conditions have not caused significant changes compared to the earth solidified sample. © 2013 Springer Science+Business Media Dordrecht. Source

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