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978-3-8439-4270-6, Reihe Thermodynamik

Florian Weckenmann
Experimental Investigation of Isolated Fluid Particles under Extreme Conditions

182 Seiten, Dissertation Universität Stuttgart (2019), Softcover, A5

Zusammenfassung / Abstract

The temperature and pressure conditions of modern combustion engines can easily exceed the critical point of the injected fuel. A generally accepted physical model of the governing processes is still lacking and subject of great controversy within the scientific community. This thesis has the goal to establish a broad experimental database, to develop and evaluate new measurement techniques and to gain a better understanding of the encountered physical phenomena of supercritical fluid injections. First, an experimental set-up has been developed, which enables the injection of isolated fluid droplets/particles into a sub- and supercritical test atmosphere. A wide range of measurement techniques was applied: e.g. the shadowgraphy technique (mono and stereo), the diffuse light technique and the Differential Infrared Thermography (DIT) technique. The latter with the goal to measure the temperature of the injected fluid. Experiments at subcritical conditions were carried out to characterize the performance of the experimental set-up and establish a comprehensive database of droplet experiments. Numerous experiments at supercritical test conditions were conducted with temperature and pressure of the test atmosphere being well above the critical point of the injected fluid. No evidence for a transition of the acetone fluid particles from a sub- to a supercritical state could be detected during the observable falling space, even at the maximal reduced pressure of pr = 1.28 and the maximal reduced temperature of Tr =1.08. Even an increase in the reduced pressure to pr =1.78, realized for the pentane test campaign, showed no evidence of a sub- to supercritical transition of the fluid particle. Finally, the applicability, performance and limits of the DIT technique, applied to single, isolated fluid particles, were investigated.