Study on Side-Jet Injection Near a Duct Entry With Various Injection Angles

[+] Author and Article Information
Tong-Miin Liou, Chin-Chun Liao, Shih-Hui Chen, Hsin-Ming Lin

Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan 30043, R.O.C.

J. Fluids Eng 121(3), 580-587 (Sep 01, 1999) (8 pages) doi:10.1115/1.2823508 History: Received November 23, 1998; Revised May 13, 1999; Online December 04, 2007


Turbulent flowfields resulting from an oblique jet injecting from a rectangular side-inlet duct into a rectangular main duct with an aspect ratio 3.75 without a forced crossflow are presented in terms of laser-Doppler velocimetry measurements. The main focuses are the effects of the side-jet angle (θ) and side-jet flow rate (Qs ) on the mass entrainment upstream of side-jet port and the flowfield in the rectangular duct. The side-inlet angles investigated were 30, 45, and 60 deg and Reynolds numbers based on the air density, rectangular duct height and bulk mean velocity were in the range of 7.1 × 103 to 3.6 × 104 corresponding to Qs values of 1 × 103 to 5 × 103 L/min. The present study suggests the presence of a critical side-injection angle θc (30 ≤ θc ≤ 45 deg) above which a recirculation zone appears in the rectangular duct, whereas below which the recirculation zone is absent. For the more tangential angle (θ = 30 deg), almost as much fluid is entrained into the main duct as was injected from the side jet. The mean flow field in the rectangular duct is found to be a weak function of the Reynolds-number for the range of Qs investigated. In addition, a simple linear correlation between the mass entrainment upstream of the side-jet port and side-injection angle is obtained. Complementary flow visualizations and numerical computations with an algebraic Reynolds stress model were also performed. The discrepancies between measured and computed results are documented.

Copyright © 1999 by The American Society of Mechanical Engineers
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