Experimental study of evaporating jets of superheated iso-octane.

Author(s)

Marcelo Mendes Vieira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2005-08-16

Examining board members

José Roberto Simões Moreira; Fernando de Almeida Franca; Julio Cesar Passos; Marcos de Mattos Pimenta; Celso Luiz da Silva

• Advisor: José Roberto Simões Moreira

Abstract

The main goal of this thesis is to present results of experiments with flashing liquid jets of iso-octane. The experiments were carried out with a liquid jet issuing from a small nozzle into a low-pressure chamber. High degrees of metastability were obtained as the liquid jet expanded within the nozzle. Injection pressure and temperature were controlled to the desired testing values for a few seconds, which were found long enough to reach and keep the steady state regime. The photographic documentation of the phenomenon was obtained from a \"Schlieren\" set up using CCD camera. The \"back-lightening\" visualization technique was also used in order to compare both image techniques and to unveil some flashing phenomenon details. Analyses of these images with the help of mathematical filters as well as other image manipulating techniques enabled a qualitative visualization of the flashing liquid jet structure and geometry leaving the nozzle. Three liquid jet regimes were observed: (1) continuous liquid jet (2) partially atomized, and (3) evaporation with the presence of shock waves. In this latter case, we speculate that the evaporation took part on the liquid jet surface, which had the approximate shape of a cone. Also it was employed the oblique evaporation wave theory to explain some of the behavior of the overall evaporation process. The tests were carried out using three conical-converging nozzles made of different materials: a 0.3 mm exit diameter steel nozzle, a 0.8 mm exit diameter steel nozzle, and a 0.35 mm exit diameter glass nozzle. (AU)