A study of fuel sprays in high temperature diesel type combustion
Abstract
Light scattering measurements and high speed photography, with the purpose of discovering droplet penetration distance and evaporation time, have been made during transient diesel type combustion in a constant volume bomb. The optical setup used for the light scatter experiment is similar to an LDV, except that a single beam is focused to form a probe volume, and scattered light is collected 8 degrees off axis from the incident beam. Three fuels were used; a number two diesel test fuel, normal pentane, and ethyl alcohol. Each of these fuels was injected into vitiated air at three different conditions of temperature and pressure; T = 700 K (P = 22.3 bar), T = 1200 K (P = 38.1 bar), and T = 1770 K (P = 56.3 bar). The light scatter measurement technique is considered to be an effective tool for studying fuel sprays in real, engine-like conditions, and it is relatively easy to implement. The technique provides relative measurements of droplet density at a location and time in the combustion chamber. A photodiode also provides measurements of flame luminance at the same location and time as the light scatter measurement. From a series of these measurements throughout the chamber, it is possible to draw conclusions concerning the spray shape and penetration distance, droplet evaporation history, development of the burning plume, and interactions between the flame and the fuel spray. Results of the experiments show that droplets were formed in the shear layer of the atomizing spray for all conditions tested, even though the gas temperature was above the critical temperature of the fuels. Burning and nonburning sprays were found to behave differently under similar injection conditions with the presence of a flame affecting the spray penetration and evaporation time. Measurements of droplet density vs. distance downstream of the injector orifice show evidence that droplet breakup predominates over coalescence as droplets move downstream in the jet.
Degree
Ph.D.
Advisors
Ferguson, Purdue University.
Subject Area
Mechanical engineering
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