This doctoral dissertation describes the investigation of a new spray production mechanism using impinging liquid jets (twin-jet sprays), with the aims of acquiring a deeper understanding of the applied spray mechanism, a feasibility study of the application in IC engines and an evaluation of this concept. The thesis was organized into two parts. First, fundamental properties of twin-jet sprays oriented towards fuel injection were studied. The breakup length of a liquid jet was measured optically using orifices with a similar geometry to conventional injectors. Empirical correlations were provided in different jet breakup regimes. Similar to liquid jets, the breakup behavior of twin-jet sprays was also categorized in an Oh-Re diagram. Five dominant mechanisms were found and explained. Their boundaries were determined experimentally in relation to the jet Re and Oh. Based on this understanding, influencing parameters of the mean droplet size was normalized into three dimensionless numbers. The mean droplet size of twin-jet sprays was measured under various operating conditions which are very closed to fuel injection. Based on the measurements, a linear analysis was carried out on the liquid sheet and a theoretical model was derived to predict the Sauter-Mean-Diameter of twin-jet sprays. Comparing with the measurements, the correlation offers a very good agreement. Furthermore, velocity distributions were measured on both liquid sheet and spray plane. The results show a similar sheet velocity to the jet velocity, but the local spray velocity is proportional to the square root of jet velocity. These results were applied in the modeling of the spray angles of twin-jet sprays. The smaller angle was modeled as the maximum sheet amplitude at the breakup divided by the sheet breakup length, whereas the larger spray angle was modeled by the mass and momentum conservation of the interacting elliptical area. Both correlations show good agreement with the measurements. On the basis of the fundamental studies, injectors with ...
Twin-Jet Sprays for Fuel Direct Injection ; Doppelstrahl-Sprays für Kraftstoff-Direkteinspritzung
2016-01-01
Theses
Electronic Resource
English
DDC: | 629 |
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