DEMEC - Departamento do Curso de Engenharia Mecânica

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Browsing DEMEC - Departamento do Curso de Engenharia Mecânica by Author "Carvalho Junior, João Andrade de"

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    Experimental investigation of flameless combustion of biodiesel.
    (2022) Silva, Edson Orati da; Veríssimo, Anton Skyrda; Rocha, Ana Maura Araújo; Costa, Fernando de Souza; Carvalho Junior, João Andrade de
    A laboratory-scale combustor was investigated under flameless biodiesel combustion. The biofuel was used due to its importance as a green fuel substitute for conventional fossil diesel, in order to reduce the emission of greenhouse gases. The combustor design was based on the phenomenon of internal recirculation, whose intensity is determined by the airflow jet momentum rate through its air intake nozzle. This investigation is important to identify the physicochemical phenomena that govern flameless combustion of liquid fuels, in addition to determining the operating parameters of the burner. A pressure swirl atomizer was used to atomize the biodiesel. The influence of biodiesel temperature and pressure on the droplet size was investigated. Results show that after a certain liquid pressure and preheating temperature, the droplet size does not vary. The combustor aerodynamics promoted adequate mixing of fuel vapor in the vicinity of the droplet interface with diluted oxidant, as a result of high airstream jet momentum rate, leading to distributed combustion reactions. The experimental results showed that combustion at high rates of excess air and preheated air fulfilled the typical characteristics of flameless combustion due to the indistinguishable flame limits, reduced combustion noise levels, absence of soot emissions and low emissions of NOx and CO, simultaneously. On the other hand, combustion in low excess air resulted in the stabilization of a bright yellowish flame with high soot emissions together with a sharp increase in CO emissions. The droplet size has a significant influence on the establishment of stable combustion. For droplet sizes above 35 mm it was impossible to keep the burning of the biodiesel. NOx and CO emissions were affected by the excess air and temperature variations.
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    Tire pyrolysis oil in Brazil : potential production and quality of fuel.
    (2020) Gamboa, Alexander Alberto Rodriguez; Rocha, Ana Maura Araújo; Santos, Leila Ribeiro dos; Carvalho Junior, João Andrade de
    he application of tire pyrolysis technology in a country will be feasible whenever competitive and attractive products are produced. In this work, quantitative and qualitative evaluation of the potential of tire pyrolysis oil (TPO) in Brazil was carried out. The quantitative evaluation consisted of determining the amount of feedstock (waste tires) available and the volume of TPO that can be produced in Brazil per year. The qualitative evaluation was applied to a sample of TPO produced in Brazil, determining its main atomization properties: specific mass, viscosity and surface tension. In addition, a theoretical comparison of the quality of TPO spray was performed, comparing the expected mass median diameter for TPO and diesel oil (DO) spray. The results of the quantitative evaluation showed that it is possible to produce around 230 to 280 thousand m3 per year of TPO, equivalent to about 2% of the onshore petroleum and fuel oil (FO) produced in Brazil for both cases. Meanwhile, the qualitative evaluation showed that the TPO produced in Brazil has greater ease of atomization in relation to the FO produced and marketed in the country. However, preserving the quality of TPO requires proper storage, since prolonged exposure to the environment increases its viscosity by up to four times, and can change it from medium oil (22.3o API) to heavy oil (14.1o API).