EXPERIMENTAL STUDY OF THE INLET FLOW IN A NON-PREMIXED COMBUSTION CHAMBER

The evaluation, validation and development of the models used in computation fluid dynamics requires the availability of experimental data for which the boundary conditions, especially the conditions of the inlet flow, are well defined. Laser diagnostics techniques provide experimental data used in computational fluid dynamics and are a powerful tool for measurements of the mean properties and fluctuations of the turbulent flow because they are non-intrusive methods, with high repetition rate and high spatial and temporal resolution. Therefore, in the present work an experimental study of the inlet flow (inert and combusting flows) in a non-premixed combustion chamber is presented. The velocity measurements were carried out using a laser Doppler velocimeter at the entrance region of the combustion chamber. An asymmetry on the mean flow and an increase on the total velocity fluctuations with the increase of the equivalence ratio was observed. The major effect on the increase of the equivalence ratio was a presence of a coherent movement on large scales associated to the flame brush dynamics

The general position number and the iteration time in the P3 convexity

In this paper, we investigate two graph convexity parameters: the iteration time and the general position number. Harary and Nieminem introduced in 1981 the iteration time in the geodesic convexity, but its computational complexity was still open. Manuel and Klav\v{z}ar introduced in 2018 the general position number of the geodesic convexity and proved that it is NP-hard to compute. In this paper, we extend these parameters to the P3 convexity and prove that it is NP-hard to compute them. With this, we also prove that the iteration number is NP-hard on the geodesic convexity even in graphs with diameter two. These results are the last three missing NP-hardness results regarding the ten most studied graph convexity parameters in the geodesic and P3 convexities

Virtual laboratories in (bio)chemical engineering education

In the last decades, Information and Communications Technologies (ICT) have been promoting the creation and adoption of new learning and teaching styles. Virtual laboratories, by overcoming some limitations of conventional hands-on experiments, have been adopted as a complement or in substitution of laboratory sessions. This paper describes the design and implementation of two virtual labs for biochemical engineering education intended for students at the BSc degree. One of the virtual labs is intended to fully replace the hands-on experiment and consists on the determination of the correlation between oxygen transfer rate, aeration rate and agitation power in a reactor. The other virtual lab consists on the determination of the residence time distribution (RTD) in continuous stirred tanks series and was implemented to support the physical experiments rather than replacing them. The virtual labs provide the students a learning platform covering the fundamentals underlying the experiment, its pre-visualization and simulation. The effectiveness of the implemented system was evaluated through direct experimentation and survey (through questionnaires) with students taking the chemical technology lab course. For the RTD virtual Lab, and based on specific learning outcomes, teachers could assess significant improvement in students’ performance in the lab and also a more thorough discussion of the results in the reports. The survey results show that, in average, considering the two virtual labs and several classes, 93% of the students consider the virtual labs of great utility.Universidade do Minho (UM) - “Programa Qualidade

Cradle-to-gate assessment of bacterial cellulose production

In an increasing environmental conscious world, Life Cycle Assessment (LCA) is an important tool for estimate environmental impact of processes and products. This work aims to determine the environmental impacts of the production of bacterial cellulose (BC) intended to be used as a food additive. BC is a biopolymer produced mainly by Gram-negative acetic acid bacteria such as Glunoacetobacter xylinum. BC structure consist in glucose monomers arranged in a unique nanostructure, exhibiting numerous great properties, leading to wide range of applications in different areas including as a food product or as food addictive, and in high-value-added niche markets such as medical applications and cosmetic industry[1]. The LCA (cradle-to-gate) was simulated in GaBi Software (ThinkStep), using ReCiPe 2016 method to estimate the Life Cycle Impact Assessment (LCIA). LCIA translates emissions and resource extractions into a limited number of environmental impact scores (environmental impact categories) by means of the so-called characterization factors. The study includes not only the production of BC, the energy and the equipment used, but also the extraction of natural resources and their transformation and the disposal of the produced waste (Cradle-to-gate). The functional unit of this LCA was defined as 1 kg of BC packed in a plastic container and a carton box. Results presented in 18 midpoints impact categories show that the sodium hydroxide, carton package, and plastic package productions are responsible for considerable impacts. The production of sodium hydroxide and carton package are also responsible for considerable amount of water resources and emissions to the environment.info:eu-repo/semantics/publishedVersio

A STEADY PSEUDO-COMPRESSIBILITY APPROACH BASED ON UNSTRUCTURED HYBRID FINITE VOLUME TECHNIQUES APPLIED TO TURBULENT PREMIXED FLAME PROPAGATION

A pseudo-compressibility method for zero Mach number turbulent reactive flows with heat release is combined with an unstructured finite volume hybrid grid scheme. The spatial discretization is based on an overlapped cell vertex approach. An infinite freely planar flame propagating into a turbulent medium of premixed reactants is considered as a test case. The recourse to a flamelet combustion modeling for which the reaction rate is quenched in a continuous way ensures the uniqueness of the turbulent flame propagation velocity. To integrate the final form of discretized governing equations, a three-stage hybrid time-stepping scheme is used and artificial dissipation terms are added to stabilize the convergence path towards the final steady solution. The results obtained with such a numerical procedure prove to be in good agreement with those reported in the literature on the very same flow geometry. Indeed, the flame structure as well as its propagation velocity are accurately predicted thus confirming the validity of the approach followed and demonstrating that such a numerical procedure will be a valuable tool to deal with complex reactive flow geometries

Virtual laboratories in (bio)chemical engineering education

"Qualidade” of the Universidade do Minho

Extreme events of precipitation in the rainy season of the state of Bahia.

Abstract: The increase of frequency and intensity of extreme precipitation events has generated consequences for biodiversity of natural systems, economic and life losses. In particular, the state of Bahia has been the scene of an increase of severe droughts in almost its entirety and outbreaks of floods that serve as a warning to the future. In this regard, the objective of this work was to analyze the frequency of occurrence of extreme events of precipitation between 1981 and 2010 of Bahia.Resumo em português: Eventos extremos de precipitação na estação chuvosa do estado da Bahia. SIC 2013

Classificação de anos secos e chuvosos em zonas pluviometricamente homogêneas no Estado da Bahia.

O conhecimento da distribuição espaço-temporal das chuvas pode orientar a tomada de decisão sobre as medidas necessárias para minimizar os danos decorrentes da irregularidade dessa variável. Em particular, o Estado da Bahia apresenta um cenário com alta variabilidade na precipitação pluvial, decorrente da conjunção de diferentes sistemas meteorológicos que atuam nessa região, bem como, de um relevo constituído por planícies, vales, serras e montanhas (BARSOSA, 2000). As técnicas de mineração de dados são uma alternativa promissora para identificar zonas pluviométricas homogêneas e analisar o comportamento das séries temporais (HAN; KAMBER, 2011). Neste sentido, o objetivo deste trabalho foi identificar as zonas pluviometricamente homogêneas e classificar climaticamente os anos com relação à precipitação, em cada região associada com a produtividade agrícola do Estado