Laser diagnostics of gun-type spray (clustering and compound-cluster combustion of liquid spray)

Nobuyuki Kawahara, Yuji Ikeda, Tsuyoshi Nakajima

Research output: Contribution to journalArticlepeer-review

Abstract

A concept of "compound-cluster combustion" is proposed in order to investigate an applicability of group combustion theory to practical spray combustion, in which strong turbulent coherent vortex is formed and influenced spray behavior significantly. This turbulent coherent structure causes inhomogeneous droplet distribution and its population, and causes interphase exchange of properties and combustion under the effects of preferential interactions. In application of group combustion theory to practical spray combustion, these points were taken into account and phase Doppler measurement (PDA) data was analyzed : there are multiple clusters, characterized by their size and followabiliy (Stokes effect) ; clusters of different droplet sizes are produced at the same time in the flow field; the turbulent scale on cluster formation should be considered by the droplet's inter-arrival time statistics. In this research, PDA measurement with high sampling-rates and high validation- rates was carried out by optimizing the PDA set-up parameters. The integral length scale of each size cluster and the inter-arrival time statistics of the droplets can be obtained, based on the instantaneous droplet velocities as well as, but also Stokes' number, cluster size and inter-arrival time. The size-classified group combustion number is evaluated by the experimental data to demonstrate the applicability of group combustion theory. The interaction between the turbulent coherent vortex and small droplets of less than 30 μm generates essential clusters of the droplets and its combustion can be characterized by group combustion. The size of these clusters corresponds to the integral scale of the turbulent vortices. The effect of turbulent coherent structure on compound- cluster formation is examined and this effect is successfully evaluated by the Stokes effect.

Original languageEnglish
Pages (from-to)841-848
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
Volume67
Issue number655
DOIs
Publication statusPublished - Mar 2001
Externally publishedYes

Keywords

  • Droplet cluster
  • Droplet dispersion
  • Droplet followability
  • Group combustion
  • Oil burner
  • Phase doppler anemometer
  • Spray combustion

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering

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