Turbulent mixing of coaxial nozzle flows with a central-lobed mixer

Ching Man Yu, X.G. Xu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

18 Citations (Scopus)

Abstract

The turbulent mixing of turbulent, confined, coaxial nozzle flows with a central-lobed mixer were determined by measurement using a two-component fiber-optic laser Doppler anemometer at a Reynolds number of 5.1 × 104 (based on an inner circular nozzle diameter Di = 30 mm and bulk mean velocity Ur of the two streams at 1.7 m/s). The ratio of the annular mean to the core mean velocity was 2:1. The boundary-layer thicknesses in the nozzle exit plane were about 3% of the inner circular nozzle diameter. Altogether, three central-lobed mixer configurations were tested, including four-, five-, and six-lobed nozzles. A blunt leading-edge circular central nozzle (i.e., a coaxial jet arrangement) was also measured as a basis for comparison. The results showed that the streamwise vorticity originated from two sources: the geometry of the lobe and the gap between the lobe nozzle peaks and the inner annular wall. The former result was important to enhance the mixing between the two coflowing streams, whereas the latter result was important to the mixing between the annular flow and the surrounding still fluid. No streamwise vorticity would be generated if the size of the gap was larger than 15% of the inner circular nozzle diameter. Furthermore, when flow separation appeared at the lobe peaks, the strength of the streamwise vorticity generated by the gap would be strengthened with a consequence of enhancing the mixing between the annular flow and the surrounding still fluid; the number of the lobes also played an important role in the mixing processes. A center plug was found to be effective in enhancing the mixing between the two coflowing streams by eliminating the flow separation at the lobe peak regions for the six-lobed case, but with a consequence of suppressing the streamwise vorticity generated by the gap.
Original languageEnglish
Pages (from-to)517-524
Number of pages8
JournalJournal of Propulsion and Power
Volume13
Issue number4
Publication statusPublished - 1 Jul 1997
Externally publishedYes

ASJC Scopus subject areas

  • Aerospace Engineering
  • Fuel Technology
  • Mechanical Engineering
  • Space and Planetary Science

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