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Technical Memorandum

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National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135–3191

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National Aeronautics and Space Administration

Washington, DC 20546–0001

Available electronically at http://gltrs.grc.nasa.gov/GLTRS

June 1991

NASA TM–105180

AIAA–91–2459

E–6478

WU–537–02–21–00

A03

Experimental Study of Cross-Stream Mixing in a Cylindrical Duct

A. Vranos, D.S. Liscinsky, B. True, and J.D. Holdeman

Dilution; Jet mixing flow; Gas turbines; Combustion chamber; Can; Emissions

Unclassified -Unlimited

Subject Category: 07

Prepared for the 27th Joint Propulsion Conference cosponsored by AIAA, SAE, ASME, and ASEE, Sacramento,

California, June 24–27, 1991. A. Vranos, D.S. Liscinsky, B. True, United Technologies Research Center, East Hartford,

Connecticut 06108; J.D. Holdeman, NASA Lewis Research Center. Responsible person, J.D. Holdeman, (216) 433–5846.

An experimental investigation of cross stream injection and mixing has been conducted with application to a low NOx

combustor for the HSCT. Mixing in a cylindrical chamber has been studied for transverse injection from slanted slot and

round orifice injectors. Momentum ratio, density ratio, and injector geometry were the primary variables. Slanted slots of

various size, aspect ratio, and number were studied. Quantitative measurement of injectant concentration distributions were

obtained by planar digital imaging of the Mie-scattered light from an aerosol seed uniformly mixed with the injectant. The

unmixedness, defined as the ratio of the r.m.s. concentration fluctuation to mean concentration in a plane perpendicular to

the main flow direction, was found to be primarily a function of momentum ratio and injector spacing. An optimum

spacing is indicated. Unmixedness is also a function of orifice size, or mass flow ratio, but the mass flow dependence can

be accounted for by normalizing the unmixedness with its maximum theoretical value. The data indicate that a density ratio

greater than unity retards mixing. It was found that above a certain momentum flux ratio, mixing with slanted slot injectors

was better than with round hole injectors. Video tapes of the mixing at very low stream velocity indicate different jet/jet

and jet/mainstream interactions for the two types of injectors.

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