Single droplet impingement of urea water solution on heated porous surfaces

• Published in: International journal of heat and mass transfer Vol. 181; p. 121836
• Main Authors: Kuhn, C., Schweigert, D., Kuntz, C., Börnhorst, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2021; Elsevier BV
• Subjects: Breakup; Chemical reduction; Diesel engines; Droplet impingement; Droplets; Exhaust gases; Exhaust systems; Impingement; Porosity; Regime map; Selective catalytic reduction; Splash; Surface properties; Surface roughness; Ureas; Wall temperature; Wetting; Wetting boundary; Splash; Porosity; Regime map; Droplet impingement; Wetting boundary
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2021.121836

•Additional regimes: Partial rebound and partial rebound with breakup.•Leidenfrost point is shifted to higher temperatures with increasing pore diameter.•The wetting boundary is highly dependent on K.•Splash boundary is dependent on surface roughness and topography. [Display omitted] The droplet/wall interaction of urea water solution on surfaces with varying properties is one decisive element for the detailed understanding of liquid film formation in the exhaust gas system of diesel-powered engines. An experimental study was conducted on the single droplet impingement of urea water solution on porous steel surfaces. The outcome of droplet impact was investigated under variation of droplet momentum, wall temperature and surface properties such as pore diameter and surface roughness. Droplet impact is recorded by high-speed shadowgraphy. The results allow the development of regime maps describing the hydrodynamic and thermal phenomena deposition, splash, boiling induced breakup, total rebound and rebound with breakup as a function of dimensionless parameters. Based on systematic investigations the influence of surface properties on the transition boundaries can be shown. The porosity of the sample leads to a significant shift of the wetting boundary to higher temperatures, as the evolving vapour between droplet and surface can escape through the pores. The regimes partial rebound with breakup and partial rebound are introduced to describe the single droplet impingement on porous surfaces. The experimental results serve as database for modelling the droplet/wall interaction in the selective catalytic reduction system.