The Influence of Dilution Hole Geometry on Jet Mixing

Abstract

Measurements have been made on a fully annular test facility, downstream of a row of heated dilution jets injected normally into a confined cross-flow at a momentum flux ratio of 4. The investigation concentrated on the consistency of mixing between the jets, as indicated by the regularity of the temperature pattern around the cross-flow annulus. When the heated air was supplied from a representative feed annulus, the exit velocity profile across each plunged hole was significantly altered and caused a distortion of the temperature distribution in the ensuing jet. The degree of distortion varies in a random manner, so that each jet has its own mixing characteristics thereby producing irregularity of the temperature pattern around the annulus. With the same approach and operating conditions some of the plunged dilution holes were modified, and tests on this modified sector indicated a significant improvement in the circumferential regularity of the temperature pattern. Further tests showed these modifications to the dilution holes had a negligible effect on the values of the discharge coefficients.

Coherent contribution to turbulent mixing of a jet in cross flow

“…This asymmetry is more evident in the contour maps of temperature rms ( Figure 2c) and vertical turbulent heat transport term (Figure 2e), resulting in a 'skew' symmetry of certain parameters about the line z -zc = y, as a referee validly suggested. The asymmetry has been attributed by the present authors [4] to the three-dimensional character of the jet trajectory at the exit of the nozzle, as suggested by Carotte and Stevens [6]. In the light of the results of this work, however, the asymmetry is also considered to be the fingerprint of the large-scale structure reported here (notice the similarity in shape between the contour map of the vertical turbulent heat transport term wT I in Figure 2e, and the map of the coherent part of this quantity in Figure 20.…”

Design methodology for a lean premixed prevaporized can combustor

“…The intense mixing between the cross flow and jet is a result of the development of a turbulent shear layer around the periphery of the je t and eddies formed in the jet wakes (C arrotte & Stevens, 1990). This rate of mixing is affected by (Lefebvre, 1999):…”