MIXING ANALYSIS OF AXIALLY OPPOSED ROWS OF JETS INJECTED INTO CONFINED CROSS-FLOW

A CFD parametric study was performed to analyze axially opposed rows of jets mixing with crossflow in a rectangular duct. Isothermal analysis was conducted to determine the influence of lateral geometric arrangement on mixing. Two lateral arrangements were analyzed: 1) inline (jets' centerlines aligned with each other on top and bottom walls) and 2) staggered (jets' centerlines offset with each other on top and bottom walls). For a jet-to-mainstream mass-now ratio (MR) of 2.0, design parameters were systematically varied for jet-to-mainstream momentum-nux ratios J between 16-64, and orifice spacing-to-duct height ratios S/H between 0.125-1.5. Comparisons were made between geometries optimized for S/H at a specified J. Inline configurations had a unique spacing for best mixing at a specified J. In contrast, staggered configurations had two ''good mixing'' spacings for each J, one corresponding to optimum inline spacing and the other corresponding to optimum wall-impinging jet spacing. The inline configurations, due to their smaller orifice size at optimum S/H, produced better initial mixing characteristics. At downstream locations (e.g., axial distance-to-duct height ratio of 1.5), the optimum staggered configuration produced better mixing than the optimum inline configuration for J of 64; the opposite results were observed for J of 16. Increasing J resulted in better mixing characteristics if each configuration was optimized with respect to orifice spacing. For jet-to-mainstream MRs of 2.0, the optimum mixing equation [(S/H)root J = C] of Holdeman was substantiated, except the optimum mixing constant C increased by a factor of 1.8 for two-sided inline configurations.