Influence of various mesh types in nozzle flows

Namen diplomske naloge je ugotoviti vpliv tipa mreže na izračunane karakteristike toka goriva v vbrizgalni šobi, oziroma v izvrtini za vbrizg goriva. Za preučitev vpliva mrež sta bili narejeni dve mreži v programskem paketu FIRE. Vsaka izmed mrež je bila uporabljena dvakrat. Najprej je bil na vstopu v obravnavani del injektorja predpisan masni pretok goriva v odvisnosti od časa in tlak na izstopu, nato pa je bilo na isti mreži definirano gibanje igle (in s tem gibanje mreže) in tlaka na vstopu in izstopu. V naslednjem koraku so bili predstavljeni rezultatati pridobljeni z obema mrežama za vsak pristop posebej, kjer je bilo potrjeno dobro ujemanje rezultatov med samima mrežama. Nato je sledila še primerjava vseh štirih izračunov in ugotovljeno je bilo, da se vrednosti tlaka in hitrosti zelo razlikujejo. Kljub temu je težko reči ali sta načina primerljiva, saj je nadaljnje raziskovanje pokazalo zelo dobro primerljivost rezultatov za druge vstopne podatke.The purpose of this diploma work is to investigate the influence of various mesh types on flow characteristics inside of a fuel injector nozzle. For investigative purposes, two meshes in the software package FIRE have been created. Each of them was used two times. First, a time-dependent mass flow rate has been defined at the inlet region and pressure was defined at the outlet. The same mesh was later used to perform a simulation with a defined needle lift curve (and hereby the mesh movement) and inlet and outlet pressure. In the next step, the obtained results of the same approach for both meshes have been presented and a good match between the two meshes was confirmed. The results of all four calculations were compared next and dramatically different results were observed. In spite of that it is very hard to say whether the approaches are comparable. Further research showed good matching of the two approaches for different input data