An experimental study of the mixing behaviour of an acoustically pulsed air jet with a confined crossflow

Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

“…The length to achieve a given mixed state has therefore been shortened by 70%, in this case, and the mixing has been significantly increased by acoustic excitation, which is in agreement with Ref. (8). It will also be noticed improvement in mixing and reduction in length to reach a given mixed state may therefore be expected for powers greater than 90W (V /V.…”

“…6, when compared with that for the cold flow study of Ref. (8), shows about 34% less penetration at X/D = 2.86 for the hot crossflow "no-drive" and "with-drive". This difference between the thermal and velocity jet trajectories has been previously observed and discussed by Kamotani and Greber ( 12 ) and Ramsey and Goldstein ( 13 ).…”

“…The profiles are in general much flatter, with temperature minima much reduced, therefore demonstrating that the acoustic drive has strongly increased entrainment and mixing. The inflection in the upper portion of the profile at X/D = 1.43 (and X/D = 2.86 0 profile) may be due to the action of the toroidal vortices (8).…”

“…1, is the same as that used in Ref. ( 8 ) except for the provision of a combustor upstream of the test section to heat the crossflow, and the inclusion of a bank of 17 chromel-alumel thermocouples to make temperature traverses in selected planes in the test section. The fuel used was natural gas burning in air supplied by a 56 kW blower.…”

Measurements of the Entrainment Coefficient of Acoustically Pulsed Axisymmetric Free Air Jets

“…To this end Vermeulen, et al (9) made the first direct measurements of entrainment by acoustically pulsed air jets, and found that the entrainment was increased by up to 6 times for distances greater than 15 diameters axially downstream of the orifice exit plane. Further work (10), (11) on the mixing of an acoustically excited air jet with a confined crossflow showed that penetration could be increased about 100%, and mixing by at least 34% three diameters downstream of the injection orifice. Since, for a typical combustor jet mixing is perhaps of most importance over the first 15 jet diameters, an extension of Hill's (2) work to include local entrainment rate measurements in the initial region of pulsed jets is desirable.…”