Publication detail
Unsteadiness and Spatio-Temporal Statistics in Intermediate Effervescent Spray Region
DOHNAL, M. HÁJEK, J. VONDÁL, J.
Czech title
Nestacionarita a časoprostorové statistiky v přechodové oblasti šumivého spreje
English title
Unsteadiness and Spatio-Temporal Statistics in Intermediate Effervescent Spray Region
Type
conference paper
Language
en
Original abstract
Multipoint statistics theory of the ideal spray was used to investigate temporal spray stability. The analysis focused on intermediate spray region, i.e. between dense and self-similar regions. Arrival time and diameter are the studied characteristics of the droplets. Two size classes, with droplet diameters of 50 and 100 μm, were selected for steadiness analysis. The two size classes were used to investigate temporal droplet behaviour using their arrival time. Chi-square test was used to provide unsteadiness criterion. Data were collected by dual-phase Doppler anemometry (PDA) at three planes perpendicular to the spray axis (x/D = 20,40,60). At each plane, there were several measuring points spanning the spray radius, starting from the spray centreline (r/x = 0) to the spray cone boundary (r/x = 0.5). The effervescent breakup mechanism is shown to produce spray unsteadiness, which is however significant only away from spray axis. In a narrow cone around the spray axis, the spray is steady on a significance level of 5 %. This result provides guidance for assessment of effervescent spray unsteadiness. The data show unexpectedly similar levels of unsteadiness for gas-liquid ratios between 5 and 15 %. This has implications for combustion applications of effervescent spray, where unsteadiness is an undesirable property.
Czech abstract
Teorie vícebodových statistik ideálního spreje byla použita ke zkoumání časové stability spreje. Analýza se zaměřila na přechodový (střední) obast spreje, ležící mezi oblastí hustého a sobě-podobného spreje. Čas příletu a průměr jsou studovanými charakteristikami kapiček. Dvě třídy velikosti kapek, s průměrem 50 až 100 um, byly vybrány pro analýzu stacionarity. Tyto dvě velikostní kategorie byly použity pro vyšetřování časového chování kapiček pomocí času jejich příletu. Byl použit Chi-kvadrát test jako kritérium nestacionarity. Data byly zjišťovány s užitím duální fázové Dopplerovské anemometrie (PDA) na třech rovinách kolmých k ose spreje (x / D = 20,40,60). V každé rovině bylo několik měřicích bodů, napříč přes poloměr spreje, počínaje od jeho osy (r / x = 0) po jeho kuželový okraj (r / x = 0,5). BYlo prokázáno, že šumivý mechanismus atomizace produkuje nestacionaritu, která je však významná pouze mimo osu spreje. V úzkém kuželi kolem osy spreje je sprej stacionární na hladině významnosti 5%. Tento výsledek poskytuje návod k posuzování nestacionarity šumivých sprejů. Data ukazují nečekaně podobné úrovně nestacionarity pro poměr plyn-kapalina mezi 5 a 15%. To má důsledky pro spalovací aplikace šumivého spreje, kde nestabilita je nežádoucí vlastnost.
English abstract
Multipoint statistics theory of the ideal spray was used to investigate temporal spray stability. The analysis focused on intermediate spray region, i.e. between dense and self-similar regions. Arrival time and diameter are the studied characteristics of the droplets. Two size classes, with droplet diameters of 50 and 100 μm, were selected for steadiness analysis. The two size classes were used to investigate temporal droplet behaviour using their arrival time. Chi-square test was used to provide unsteadiness criterion. Data were collected by dual-phase Doppler anemometry (PDA) at three planes perpendicular to the spray axis (x/D = 20,40,60). At each plane, there were several measuring points spanning the spray radius, starting from the spray centreline (r/x = 0) to the spray cone boundary (r/x = 0.5). The effervescent breakup mechanism is shown to produce spray unsteadiness, which is however significant only away from spray axis. In a narrow cone around the spray axis, the spray is steady on a significance level of 5 %. This result provides guidance for assessment of effervescent spray unsteadiness. The data show unexpectedly similar levels of unsteadiness for gas-liquid ratios between 5 and 15 %. This has implications for combustion applications of effervescent spray, where unsteadiness is an undesirable property.
Keywords in English
CFD; stirred tank; multiphase; simulation; mixing
RIV year
2015
Released
01.10.2015
Publisher
Aidic Servizi Srl
Location
Milano, Italy
ISBN
978-88-95608-36-5
ISSN
2283-9216
Book
CHEMICAL ENGINEERING TRANSACTIONS - VOL.45
Volume
45
Pages from–to
1027–1032
Pages count
6
BIBTEX
@inproceedings{BUT117284,
author="Miloslav {Dohnal} and Jiří {Hájek} and Jiří {Vondál},
title="Unsteadiness and Spatio-Temporal Statistics in Intermediate Effervescent Spray Region",
booktitle="CHEMICAL ENGINEERING TRANSACTIONS - VOL.45",
year="2015",
volume="45",
month="October",
pages="1027--1032",
publisher="Aidic Servizi Srl",
address="Milano, Italy",
isbn="978-88-95608-36-5",
issn="2283-9216"
}