Vinicius Zacarias Madela
Luís F. de A. Pauliny
Carlos A. Gurgel Veras -gurgel@enm.unb.br
Universidade de Brasília - Faculdade de Tecnologia - Departamento de Engenharia Mecânica
Asa Norte, 70910-900  Brasília - DF

Fernando de S. Costa -fernando@cptec.inpe.br
Instituto Nacional de Pesquisas Espaciais - Laboratório Associado de Combustão e Propulsão
Rod. Presidente Dutra km 40, 12630-000 Cachoeira Paulista - SP

A utilização de mecanismos detalhados de queima de hidrocarbonetos em códigos comerciais de dinâmica dos fluidos computacional é inviabilizada pela demanda excessiva de memória computacional e velocidade de processamento. A análise, porém, pode ser realizada por uma cadeia de reatores do tipo "perfectly stirred" (PSR) e "plug flow" (PFL) baseada em análise preliminar do escoamento por intermédio de dinâmica dos fluidos computacional. Os resultados indicam a validade na aplicação da técnica de cadeia de reatores em problemas complexos de dinâmica dos fluidos com reação química principalmente no que se refere ao estudo das emissões. O presente trabalho apresenta os resultados obtidos na simulação da câmara de combustão de microturbinas multicombustíveis. Particularmente, são apresentadas as previsões para a queima de metano e de diesel. Para tal foram utilizadas as rotinas apropriadas do código computacional CHEMKIN III.

Palavras-chave: Combustão, turbinas, CHEMKIN III
 
 

Fábio Luís Fassani fassani@fem.unicamp.br
Alex Álisson Bandeira Santos absantos@fem.unicamp.br
Leonardo Goldstein Junior leonardo@fem.unicamp.br
State University of Campinas
College of Mechanical Engineering, Department of Fluid and Thermal Engineering

Carlos Alberto Ferrari ferrari@ifi.unicamp.br
State University of Campinas
Physics Institute, Department of Quantum Electronics

Soot particles are produced during the high temperature pyrolysis or combustion of hydrocarbons. The emission of soot from a combustor, or from a flame, is determined by the competition between soot formation and its oxidation. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of the induced air diffusion on the soot axial distribution concentration in a premixed acetylene/air flame was studied. The flame was generated in a vertical axis burner in which the fuel - oxidant mixture flow was surrounded by a nitrogen discharge coming from the annular region between the burner tube and an external concentric tube. The nitrogen flow provided a shield that protected the flame from the diffusion of external air, enabling its control. The burner was mounted on a step-motor driven, vertical translation table. The use of several air-to-fuel ratios made possible to establish the sooting characteristics of this flame, by measuring soot concentration along the flame height with a non-intrusive laser light absorption  technique.

Keywords: Combustion, Flame, Soot Formation, Laser
 

John Jairo Ramírez Behaine - jbehaine@logos,upb.edu.co
Universidad Pontificia Bolivariana, Centro de Investigaciones para el Desarrollo Integral,
Grupo de Investigaciones Ambientales A.A. 56006-Medellín, Colombia.

Caio Glauco Sánchez - caio@fem.unicamp.br
Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica, Departamento de
Engenharia Térmica e de Fluidos. Cx. P. 6088 - 13083-970 - Campinas, SP, Brasil.

Reduction of H2S during the Mineral Coal Gasification Using the Dolomite Addition in a Fluidized Bed Reactor Brazilian mineral coal from Candiota mine (Rio Grande do Sul State) was gasified with air in a atmospheric fluidized bed reactor at laboratory scale. Experimental essays carried out in a 0.2 m internal diameter reactor permited both, to evaluate the gasifier operation at different air factors without dolomite particles addition, and to study the effect adsorvent on the capture hidrogen sulfide (H2S), contained in the generated gas. Test were done with and without the use of dolomite. Without using dolomite, the maximum gas lower heating value was 2.2 MJ/Nm 3 and the cold gas thermal eficiency was close to 43%, operating at an air factor between 0.45 and 0.60. During the experimental test with dolomite , a maximum reduction of 58% for H2S was attained using a molar ratio of Ca/S equal to 4. Literature review showed higher capture eficiencies, even at lower molar ratio (Ca/S). Variances were probably caused by low residense times in the gas-solid interation, considering the used buble fluidization regime.

Keywords: Coal Gasification, Gaseous Desulfurization, Hydrogen Sulfide, Fluidized Bed.
 
 

Sérgio Araújo - ssaraujo@iem.efei.br
EFEI - Escola Federal de Engenharia de Itajubá
Av. BPS, 1303 - Itajubá - 37500-000 - MG
Rogério J. Da Silva - rjsilva@iem.efei.br

More and more, the cement industries have used their rotative kilns for the destruction of industrial residues. In the time that the demand of residues for the co-processing grows in these kilns, also increases the concern which refers to the pollutants emissions. It is known that to burn wastes which contain materials with presence of halogens above of certain levels can contribute to the production of organic composites known as dioxins and furans. The cement kilns are really a good option for co-processing because the residence time of the gases in its interior is big enough to guarantee a complete destruction of organic composites, but depending on the type and where the residues are introduced, it cannot have a great condition for the dioxins and furans destruction. This article look for to do an analysis of the factors that get the dioxins and furans formation inside the rotative kilns, considering the restrictions with relationship to the types of co-processed residues, the percentage of substitution of traditional fuels, feeding points, and control equipments. The analysis of temperature profiles and of the time of permanence of the gases in the different internal zones of the kiln allows an accompaniment of the reactions involved in the process of it burns.

Keywords: Dioxins, Furans, Cement, Kinetics, Combustion.
 
 

Waldir A. Bizzo - bizzo@fem.unicamp.br
Leonardo Goldstein Jr. - leonardo@fem.unicamp.br
André L. Cardoso
Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Departamento de Engenharia Térmica e de Fluidos
Caixa Postal 6122 - 13083-970 Campinas SP

Paulo R. Tardin Jr. - paulotardin@usf.com.br
Universidade São Francisco, Centro de Ciências Exatas e Tecnológicas
13251-900 - Itatiba SP

Thermal incineration has been in use for the treatment and disposal of hazardous wastes. The secondary combustion chamber plays an important role on controlling the efficiency of waste destruction and the emissions of products of incomplete combustion. For monitoring the process in real time, a continuous analysis of total hydrocarbons (THC) and CO is used. This work studied the effect of the swirl number in the CO and THC emissions, using three toluene concentration in the incinerated waste and two excess air values. Tests were performed experimentally in a cylindrical horizontal combustion chamber, with thermal insulation, a variable swirl burner, a sample gas probe and a continuous THC analyzer. Increasing the swirl number reduced the THC and CO emissions for an air excess of 42%, but increased the emissions for the air excess of 19%. The size of the plug flow region influenced the combustion efficiency, and the effects were different according to the air excess and the toluene concentration in the waste. The relation CO/THC remained nearly unchanged during the tested conditions.

Keywords: combustion; incineration; pollution; carbon monoxide; total hydrocarbons.
 
 

Carlos Alberto Rocha Pimentel - cpimentel@iae.cta.br
Centro Técnico Aeroespacial, Instituto Tecnológico de Aeronáutica
CTA/ITA/IEAA - 12228-900 - São José dos Campos, SP, Brasil
L.F. Figueira da Silva, B. Deshaies - da-silva@lcd.ensma.fr
Laboratoire de Combustion et de Détonique, UPR 9028 du CNRS - ENSMA
86960 Futuroscope, France
João Luiz F. Azevedo - azevedo@iae.cta.br
Centro Técnico Aeroespacial, Instituto de Aeronáutica e Espaço
CTA/IAE/ASE-N - 12228-904 - São José dos Campos, SP, Brasil

Resumo. Um estudo numérico da combustão dentro do escoamento supersônico bidimensional, de uma mistura reativa H2 - ar é apresentado.  O objetivo do presente trabalho é investigar a ignição dos gases premisturados atrás de uma onda de choque oblíquoa estabilizada por um diedro, assim como, a estrutura que se forma na região de transição a qual separa a onda de choque oblíqua da onda de detonação oblíqua.  Além disso, é feito um estudo preliminar das condições aerodinâmicas que podem levar uma onda de detonação oblíqua relaxar até a formação de uma onda de detonação oblíqua do tipo Chapman-Jouguet.  Para este propósito, é usado um código computacional em volumes finitos, em malha não estruturada e uma técnica de refinamento adaptativo.  As propriedades físico-químicas são funções da composição química da mistura reativa, temperatura e pressão, e são calculadas utilizando o código computacional CHEMKIN-II.

Palavras-chave: Escoamento reativo, Combustão supersônica, Onda de choque oblíqua, Onda de detonação oblíqua.
 
 

Arima, M. N.
Krieger, G. C. - guenther@usp.br
Universidade de São Paulo
Escola Politécnica -Departamento de Engenharia Mecânica

The formation of CO and CO2 in a methane turbulent diffusion flame is investigated in the present work. Three models are used to perform the simulation: Eddy Break Up (EBU), Eddy Dissipation Concept (EDC) and Equilibrium Chemistry with Presumed PDF (EQUIL). The turbulent flow is modeled using the k -å model. In the Presumed PDF model, fast chemistry is assumed for the combustion model. In the EBU model, the average chemical source for the species transport equation is constructed using the turbulent quantities turbulent kinetic energy and the dissipation ratio of k. In the EDC model, a reduced mechanism encompassing 14 species is integrated in a perfectly stirred reactor and used as averaged source term. From the obtained results, can be concluded that the EQUIL and EDC models reproduce the flame structure in good agreement with the experimental data, except the CO concentration. The EBU is not able to capture the kinetic effects, which are of paramount importance in the CO and CO2 formation. Further work to properly estimate the parameters of the EDC model, would give better results concerning the CO formation.

Keywords: Turbulent Reactive Flows, Metane, Numerical Simulation, Emissions
 
 

Marcos R. Mafra - mmafra@feq.unicamp.br
Waldir A. Bizzo - bizzo@fem.unicamp.br
Fábio Luis Fassani - fassani@fem.unicamp.br
Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Departamento de Engenharia Térmica e de Fluidos
Caixa Postal 6122 - 13083-970 Campinas, SP, Brasil

The use of incinerators on industrial waste treatment requires the knowledge of its pollutant gases emissions. Thermal oxidation of the gases produced by waste volatilization takes place within the combustion chamber, whose typical parameters are high air excess and high temperature. These parameters favours NOx production. In this paper, the effects of air injection by swirl jets on the combustion and gas emission characteristics were studied. Temperature and gas concentration profiles within the chamber were obtained for two swirl numbers in two level of gas exit temperature. Results showed that the temperature fluctuations were higher for low swirl numbers, thus causing high rates of NOx formation. It was shown, however, that the main NOx formation route was the thermal one.

Keywords: Combustion; Pollution Control; NOx Emission; Swirl Number.
 
 

Antonio Luiz Pacifico - pacifico@ipt.br
Jurandir Itizo Yanagihara - jiy@usp.br
Universidade de São Paulo, Depto. Eng. Mecânica - EPUSP
Av. Prof. Mello Morais, 2231 - 05508-900 - São Paulo, SP, Brasil

In this research work, the effects of the operational and geometrical parameters on the mixing point pressure in Y-jet atomizers were studied using an experimental apparatus working with air and water. The results show that the mixing point pressure is very dependent on the diameter ratio of the mixing duct and the air port and the water supply pressure ratio. A correlation to predict the mixing point pressure was developed and showed a good agreement with the experimental data. With this correlation it is possible to predict the occurrence of the critical condition for the air flow at the exit of the its port.

Keywords: Y-jet atomizers, Two-phase flow, Air-water, Geometric study
 
 

Fernando de Souza Costa - fernando@cptec.inpe.br
José Carlos dos Santos - jcarlos@cptec.inpe.br
INPE, Laboratório Associado de Combustão e Propulsão
C.P. 01, Cachoeira Paulista, 12630-000, SP, Brasil

Carlos Alberto Gurgel Veras - gurgel@enm.unb.br
Universidade de Brasília, Departamento de Engenharia Mecânica
Asa Norte, 70910-900, Brasilia, DF, Brasil

João Andrade de Carvalho-Jr - joao@feg.unesp.br
UNESP, Departamento de Energia

Av. Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá, 12500-000, SP, Brasil
David V. Sandberg - David.Sandberg@orst.edu
USDA Forest Service, 3200 SW Jefferson Way, Corvallis, Oregon 97331, USA

Ralf Gielow - ralf@met.inpe.br
INPE, Divisão de Ciências Meteorológicas
C.P. 515, São José dos Campos, 12201-970, SP, Brasil

This work describes temperature and heat flux measurements in logs obtained during prescribed burns at Alta Floresta, Mato Grosso, in the arc of deforestation of the Amazon basin. Different phases of burning were followed by measuring temperatures in several points inside the falled logs, including drying, devolatilization, flaming, calcination and smoldering phases. The effects of the drying period and convection in the border were analyzed. The collected data can be useful in the numerical modelling and in analytical studies of biomass combustion, specially in the conditions of forest clearing for soil preparation, as made by farmers in the Amazon region. The knowledge of flamability conditions in the fallen tree areas and in the virgin forest allow to indicate the more appropriate conditions for burns, with lower risks of fire spread to neighbour areas. Also it allows to quantify more precisely the effects of biomass burning on global warming.

Keywords: combustion, biomass, smoldering, temperatures, Amazonia
 
 

Ailton Durigon - ailton@uniplac.rct-sc.br
Universidade do Planalto Catarinense - UNIPLAC, Departamento de Ciências Exatas e
Tecnológicas, Cx. P. 525 - 88509-900 - Lages, SC, Brasil

Viktor G. Krioukov - kriukov@main.unijui.tche.br
Universidade Regional do Noroeste do Estado do Rio Grande do Sul - UNIJUI,
Departamento de Tecnologia, Cx. P. 560 - 98700-000 - Ijuí, RS, Brasil

Valdeci J. Costa - vcosta@iscc.com.br
Universidade do Planalto Catarinense - UNIPLAC, Departamento de Ciências Exatas e
Tecnológicas, Cx. P. 525 - 88509-900 - Lages, SC, Brasil

The work analyses the soot formation in the combustion processes of hydrocarbons and is devoted the research of the initial stage or chemical phase. To describe the physical-chemical phenomena, the mathematical model uses the equations of the chemical kinetics in their exponential form, where the group of the elementary reactions form a system of algebraic-differential stiff equations. The database was complemented with information about some hydrocarbon, including soot that comes with chemical formula HC4. The model was compared with experimental data. The numerical simulations were accomplished for the ambient reagents: C2H2 + air and C3H8 + air, temperatures are considered in interval of 400 K to 2000 K; oxidant excess' coefficients of ( ox á ) of 0,1 to 1, through which final compositions are analysed and substance's behaviour, and soot's emission as well.

Keywords: Soot, Combustion, Hydrocarbon, Mathematical Model
 
 

Valdeci José Costa
UNIPLAC - Universidade do Planalto Catarinense, Departamento de Ciências Exatas e
Tecnológicas , Lages, SC, Brasil, CP 525, CEP 88.509-900
Email: vcosta@iscc.com.br

Viktor Krioukov
UNIJUÍ - Universidade Regional do Estado do Rio Grande do Sul, Programa de Pós-
Graduação em Modelagem Matemática, CP 560, CEP 98.700-000 Ijuí RS - Brasil
Email: kriukov@main.unijui.tche.br

Clóvis Raimundo Maliska
UFSC - Universidade Federal de Santa Catarina. Departamento de Engenharia Mecânica.
Florianópolis, SC, Brasil, CP 476, CEP 88.040
Email: maliska@sinmec.ufsc.br

In this work I propose a numeric study destined to the combustion of wet pulverized coal in reacting flow. The mathematical model is composed by equations for the concentration of the substances in the reacting flow, written based in the chemical kinetics and exponential form, conservation equations and devolatilization equations, combustion of the carbon and residues. The study detects fluctuation among the temperatures of the gas and of the particles. The inclusion of the humidity as constituent part of the volatile matter doesn't affect the performance of the model, however, its presence alters the temperature profiles and the gaseous composition. With the increase of the humidity in the coal have a slight reduction in the time of combustion of the particle, what agrees with experimental data. The model foresees an increment in the difference Tp-Tg and a smaller production of CO with the increase of the wetness rate. The volatile ones, in spite of they have its fraction relatively reduced with the wetness presence they are liberated more slowly with its increment, provoking change in the position of front flame.

Keywords: Mathematical model, wet, pulverized coal combustion.
 
 

Fachini F.F.- fachini@yabae.cptec.inpe.br
Instituto Nacional de Pesquisas Espaciais,
12630-000, Cachoeira Pta - SP, Brazil.
Williams F.A. - faw@ames.ucsd.edu
Seshadri K. - seshadri@cauvery.ucsd.edu
Mechanical and Aerospace Engineering Department
Center for Combustion and Energy Research,
University of California, San Diego,
La Jolla CA 92093, USA.

The method of rate-ratio assympotics is employed in the analysis of a n- heptane counter ow di_usion ame to specify the extinction conditions. The oxidation of
the n-heptane is represented by a mechanism of four-global reactions. The _rst reaction describes the attack of the fuel by the H-radical and the other three reactions correspond to the oxidation of CO and H2, and are the same reactions found in the oxidation of methane. The counter ow con_guration imposes a stretch on the ame, which can lead to extinction. Extinction is observed for low values of stretch when radiative energy loss is large and for high values of stretch because reaction is incomplete. The results show ame extinction for low and high stretch levels and the conditions for no existence of ames.

Keywords:. Di_usion Flame, Extinction, Rate-Ratio Asymptotics, n-Heptane.
 
 

Edson G. Moreira Filho .- edson@lmt.coppe.ufrj.br
Albino J.K. Leiroz . - leiroz@ime.eb.br
Department of Mechanical and Materials Engineering
Instituto Militar de Engenharia
22290-270 - Rio de Janeiro, RJ, Brazil

A numerical study of droplet surface regression effects on the interference generated flow patterns within the liquid-phase of an infinite linear array of spherical droplets in the absence of surrounding convective effects is discussed in the present work. The transient evolution of the flow field, obtained using an axisymmetric vorticity-stream function approach, show the development of two toroidal vortices surrounded by a viscous boundary layer close the liquid-gas interface and by a internal wake in the stream axis region. The evolution of the temperature field is also analyzed. An analytical grid generation procedure is used in order to transform the moving-boundary physical domain into a fixed-boundary computational domain and to cluster points in the droplet surface near field, where pronounced gradients are expected. The transformed equations are discretized using the Finite Difference Method and the resulting system of algebraic equations is solved by iterative methods with local error control. Results indicate that velocity and temperature distribution inside individual stream droplets are significantly different from patterns found for isolated droplets in convective streams. Besides, comparison with results where the droplet surface regression is neglected show that the flow and temperature field developments are delayed by the moving boundary effect.

Keywords: Droplet Combustion, Droplet Vaporization, Numerical Methods, Convection, Moving Boundary.
 
 

Pedro Teixeira Lacava - lacava@aer.ita.cta.br
Amilcar Porto Pimenta - amilcar@aer.ita.cta.br
Instituto Tecnológico de Aeronáutica, Divisão de Engenharia Aeronáutica
Pça. Mal. Eduardo Gomes, 50, Vila das Acácias, São José dos Campos, SP, Brasil CEP: 12228-900

João Andrade de Carvalho Jr. - joao@feg.unesp.br
Universidade Estadual Paulista, Campus de Guaratinguetá, Depto. de Energia
Av. Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá -SP, Brasil, CEP: 12500-000

Marco Aurélio Ferreira
Instituto Nacional de Pesquisas Espaciais, Laboratório Associado de Combustão e Propulsão
Rod. Presidente Dutra, km 40, Cachoeira Paulista, SP, Brasil, CEP: 12700-000

The use of oxygen to enrich the oxidizer can be an attractive alternate to increase incineration rates of a combustion chamber originally designed to operate with air. For a certain fuel flow rate, if some incineration parameters are held constant (as combustion chamber temperature, turbulence level and residence time), an increase of incineration rates becomes possible with injection of oxygen. This work presents an experimental evaluation of combustion air enrichment in a combustion chamber designed to incinerate aqueous residues using diesel as fuel and air as oxidizer.

Keywords: Combustion, Incineration, Enriched Flames, Pollutant Emissions