 The thesis defense by Mr. Seied Davood Musavian, a Ph.D. candidate in aerospace engineering, entitled " Experimental explanation of the interaction of heterogeneous collision jets", will be held on 2023-Augost-10 at 10:00 (Tehran time) at the Iranian University of Science and Technology (IUST) Mechanical Faculty. The members of the Space Propulsion Research Laboratory (SPRL) invite all interested parties in this field and the other relevant areas to participate in this defense.
AbstractAtomization is the process of breaking down a liquid volume into a spray of small droplets. This process includes the break up of the liquid jet or the liquid sheet that comes out of the injector. In this study, we attempted to compare the behavior of a liquid nitrogen jet, a liquid nitrogen jet impingement, and a liquid nitrogen/methanol semi-cryogenic jet to that of a water jet and a water jet impingement. In addition, the behavior of water jet impingement at various speeds has been studied. Photography was utilized to study the various patterns created during this interaction. The speed of liquid nitrogen jets was increased from 12 to 34 m/s, and the Reynolds number was increased from 50,000 to 136,000. A water jet with a speed of 4-8 m/s has a Rayleigh breakup model, a speed of 8-20 m/s has a first wind-induced breakup model, and speeds over 20 m/s have a multiple peels model. By qualitatively comparing the photos taken of the water jet impingement, the range of velocity and Reynolds number of closed rims, periodic droplets, open rims, and fully developed models were determined. The results revealed a significant insight: when Reynolds numbers exceed 30000, the average droplet diameter measures approximately 80 µm. The study's initial phase employed the liquid nitrogen subcooling technique by holding it at low pressureو so that the liquid nitrogen jet exiting the injector into the high-pressure test chamber became a subcooled liquid. The subsequent stages involved exploring the atomization of the jet and the impact of liquid nitrogen jet impingement. Within the range of speeds examined, the breakup model of sub-cooled liquid nitrogen jet impingement in the test chamber is a fully developed model and The impinging jet's surface took on an entirely undulating character. The comparison of liquid nitrogen jet impingement with water jet impingement at equivalent speeds indicated that the former exhibited a quicker breakup due to its lower viscosity and surface tension. Also, due to lower surface tension, heat transfer, and evaporation, the diameter of droplets and ligaments resulting from the impinging of two liquid nitrogen jets is smaller than water. In the impinging of liquid nitrogen/methanol jets, the formation of the vapor phase at the impinging point of the two jets caused the formation of instabilities in the liquid sheet and caused the accelerated breakup. Notably, the vapor phase disrupted the formation of the regular concentric sectors that typically appear in water sheets.
Keywords:
Atomization; Cryogenic jet impingement; Unlike jet impingement; Liquid nitrogen / methanol jet impingement
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