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Doctoral Thesis
Author of thesis: Ing. Ondřej Cejpek, Ph.D.
Acad. year: 2024/2025
Supervisor: prof. Ing. Jan Jedelský, Ph.D.
Reviewers: prof. Ing. Jan Vimmr, Ph.D., Ing. Darina Liederhausová, Ph.D., Ing.Paed.Igip
Sprays are deployed across industrial sectors, energy production, and agriculture, influencing everything from chemical processes to combustion efficiency. Atomizers are typically developed and tested in controlled laboratory conditions that lack external ambient flow, which significantly impacts the spray characteristics. Understanding the interaction between sprays and surrounding flows is crucial for designing efficient atomizers for practical environments. This work deals with pressure-swirl and effervescent atomizers under cross and counter-flow conditions. Advanced optical measurement techniques such as high-speed visualisation and Phase Doppler Anemometry are used to analyse droplet/gas interactions. It was found that atomizers featuring less stable liquid atomization, under no ambient flow conditions, may be more suitable atomizer for high-speed cross-flow. Relative velocity between the liquid sheet and the cross-flow significantly affects the breakup length, which can be accurately predicted by Linear instability analysis under cross-flow. In counterflow arrangements, reducing liquid velocity can decrease gas side pressure loss (ΔP) and flow maldistribution. Our findings revealed that an overall droplet size distribution must be included in the ΔP model to provide accurate predictions. Due to flow maldistribution, entrained droplets can be significantly larger than predicted by the assumption of uniform velocity. The results of this thesis provide new insights and clarify previously unknown aspects of spray behaviour under realistic conditions.
Pressure swirl atomizer, effervescent atomizer, impinging effervescent atomizer, ambient flow, cross and counter-flow, liquid sheet breakup, high-speed visualization, Phase Doppler Anemometry
Date of defence
09.01.2025
Result of the defence
Defended (thesis was successfully defended)
Process of defence
Student zodpověděl všechny položené dotazy. Prokázal vysokou odbornou úroveň a přínos výzkumný v uvedené oblasti. Řešené téma je aktuální s aplikační perspektivou.
Language of thesis
English
Faculty
Fakulta strojního inženýrství
Department
Energy Institute
Study programme
Power Engineering (D-ENE-P)
Composition of Committee
prof. Ing. Jiří Pospíšil, Ph.D. (předseda) Ing. Darina Liederhausová, Ph.D. (člen) prof. Ing. Jan Vimmr, Ph.D. (člen) doc. Ing. Vítězslav Máša, Ph.D. (člen) doc. Ing. Marek Mlkvik, Ph.D. (člen) Ing. Matouš Zaremba, Ph.D. (člen)
Supervisor’s reportprof. Ing. Jan Jedelský, Ph.D.
Grade proposed by supervisor: A
Reviewer’s reportprof. Ing. Jan Vimmr, Ph.D.
Reviewer’s reportIng. Darina Liederhausová, Ph.D., Ing.Paed.Igip
Responsibility: Mgr. et Mgr. Hana Odstrčilová