Amilcar Porto Pimenta

CH and C2 radicals characterization in natural gas turbulent diffusion flames

This paper reports the construction of an axisymmetric nonpremixed piloted jet burner, with well-defined initial and boundary conditions, known as the Delft burner, to assess turbulence-chemistry interaction in non-premixed turbulent flames. Detailed experimental information is described, involving hot-wire anemometry, thin-wire thermocouples and chemiluminescence visualization measurements. Radial profile of the axial mean velocity indicates excellent agreement between flow patterns developed within Delft installation and the one described herein. Chemiluminescence emissions from CH and C

Phenomenological model of particulate matter emission from direct injection diesel engines

A new phenomenological model is introduced by applying established conceptual models for direct injection combustion to develop a mathematical description of events. The model has the capability to predict particulate mass output, as well as a particulate mass history over a single combustion event. The model was developed in a Matlab-Simulink environment to promote modularity. Results of particulate mass output from single cylinder laboratory engine, and six-cylinder vehicular engine were used to determine the validity of the predictions made. Although predicted values do not perfectly match measured values, there is certainly reasonable agreement.

Experimental Evaluation of Low Pressure-Swirl Atomizer Applied Engineering Design Procedure

In a pressure-swirl atomizer a swirling motion is imparted to the fuel leading it, under the action of centrifugal forces, to spread out in the shape of a hollow cone as soon as it leaves the exit orifice. This kind of atomizer is used in gas turbines and liquid-propellant rockets. The need to minimize the combustor length usually leads to spray angles around 90 deg. The present work presents a procedure to design and verify the experimental behavior for low pressure-swirl atomizers. This atomization condition is especially important, for example, in the case of gas turbine operation under idle regime. The Sauter mean diameter and the spray-cone angle are evaluated and made to fit the calculated atomizer dimensions. The Sauter mean diameter is obtained through the use of a model originally developed for fan-spray atomizers and extended for pressure-swirl atomizers. A pressure-swirl atomizer was manufactured following this design procedure. The discharge coefficient, the spray-cone angle, and the Sauter mean diameter were evaluated experimentally and compared with the theory used to design the atomizer displaying a good matching. The spray Sauter mean diameter was measured with a laser scattering system.

DIAGNÓSTICO DA ESTRUTURA DE FRENTES DE DETONAÇÃO POR MEIO DE FOLHAS COM FULIGEM

This work deals with a method for detonation wave front diagnostics through soot foils. The main goal is to develop the method for further detonation research to be developed at the Instituto Tecnologico de Aeronautica (ITA), Brazil. The method consists in the use of smooth plates with soot impregnated surface, exposed to the medium where detonation will occur. The passing wave front selectively removes the soot, revealing triple points trajectories present on detonation waves structure. The trajectory tracks forms a distinctive pattern, like fish scale, called detonation cell. The main evaluating parameter is the detonation cell width, a dimension associated with the mixture’s detonability. The soot deposition technique was tested, varying fuels, deposition time and deposition position. Six test runs were made, were in two occasions detonation cells were detected in the soot. The detonation cells were measured through optical techniques, then were compared with a theoretical model and light emissions measurements, validating results. Detonation cell sizes measured pointed out changes in Chapman-Jouguet velocity on detonation propagation within flow fluctuations usual in Pulse Detonation Engine (PDE). Keywords: Combustion, Detonation, Diagnostics, PDE.