Review and upgrade of a bulk flow model for the analysis of honeycomb gas seals based on new high pressure experimental data/Pregled in nadgradnja modela kompresijskega pretoka pri analizi plinskih satnih tesnil na podlagi visokotlacnega eksperimenta

The design of the gas seals used in centrifugal compressors and axial turbines requires to consider not only their aptitude to reduce leakage, but also their contribution to the overall dynamics of the machine. Honeycomb and hole pattern annular seals are often employed in compressors for the end balance piston seal or as the central balance piston seal in a back-to-back arrangement. In contrast to labyrinth seals, they show a beneficial damping effect. In order to obtain an effective tool for predicting the leakage and the dynamic response of honeycomb seals, a bulk flow model has been devised in the past and, implemented in numerical codes, it is presently used in the design process. This kind of codes, however, require simplifying assumptions: in particular, one reference code available to the authors adopts the hypothesis of isothermal process. As the required level of confidence in seal design is increasing, an experimental validation and possibly some refinement are needed. In this work, the bulk flow model was reviewed and the sensitivity to different hypotheses was explored. New experimental data from a high pressure test rig were compared with the results of simulations. Keywords: gas seals, rotordynamics, honeycomb structures, vibration control Pri zasnovi plinskih tesnil za centrifugalne kompresorje in aksialne turbine je potrebno upostevati tako tesnilno sposobnost tesnil kot tudi vpliv tesnil na dinamski odziv stroja. Pri kompresorjih so satna tesnila ter tesnila z luknjastim vzorcem pogosto uporabljana za tesnenje ravnoteznega bobna, ki se nahaja na koncu gredi ali na sredini gredi pri simetricni konfiguraciji kompresorja. V primerjavi z labirintnimi tesnili satna tesnila izkazujejo boljse dusilne lastnosti. V preteklosti je bilo razvitih in numericno implementiranih vec modelov kompresijskega pretoka, ki predstavljajo efektivno orodje za napoved puscanja in dinamskega odziva satnih tesnil ter se s pridom uporabljajo v procesu razvoja kompresorja. V obstojecih modelih je privzetih vec poenostavitev; model, s katerim razpolagajo avtorji, na primer privzame hipotezo izotermalnega procesa. Z visanjem zahtevane stopnje zanesljivosti razvojnega procesa prihaja do potreb po eksperimentalni validaciji numericnega modela ter morebitnih izboljsav le-tega. V clanku je izdelan pregled modela kompresijskega toka iz vidika obcutljivostne analize pri razlicnih temeljnih hipotezah. Rezultati numericnih simulacij so primerjani z eksperimentalno pridobljenimi