DETONATION FRONT STRUCTURE DIAGNOSTICS THROUGH SOOTED FOILS

Abstract

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 Tecnológico de Aeronáutica (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.