Mixing of Multiple Jets With a Confined Subsonic Crossflow in a Cylindrical Duct

James D Holdeman,Clifford E Smith,Victor L Oechsle,G Scott Samuelsen,David S Liscinsky

doi:10.1115/96-gt-482

James D Holdeman, Clifford E Smith + Show 3 more

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https://doi.org/10.1115/96-gt-482

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Abstract

This paper summarizes NASA-supported experimental and computational results on the mixing of a row of jets with a confined subsonic crossflow in a cylindrical duct. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex 3-D flowfield in the combustion chambers in gas turbine engines. The principal observations were that the momentum-flux ratio and the number of orifices were significant variables. Jet penetration was critical, and jet penetration decreased as either the number of orifices increased or the momentum-flux ratio decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the number of orifices was proportional to the square-root of the momentum-flux ratio. In the cylindrical geometry, planar variances are very sensitive to events in the near-wall region, so planar averages must be considered in context with the distributions. The mass-flow ratios and orifices investigated were often very large (mass-flow ratio >1 and ratio of orifice area-to-mainstream cross-sectional area up to 0.5), and the axial planes of interest were sometimes near the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations. The results shown also seem to indicate that non-reacting dimensionless scalar profiles can emulate the reacting flow equivalence ratio distribution reasonably well. The results cited suggest that further study may not necessarily lead to a universal “rule of thumb” for mixer design for lowest emissions, because optimization will likely require an assessment for a specific application.

Highlights

Jets-in-crossflow have been exteasively treated in the literature
Orifice configurations can be optimized for any J, a greater downstream distance is required for equivalent mixing if either J and/or the optimum number of orifices is small
Will often require a tradeoff between effective initial mixing and effective mixing in the wall region downstream of the plane of injection. (C) The results cited suggest that further study may not necessarily lead to a universal "rule of thumb" for mixer design for lowest emissions, because optimization will likely require an assessment for a specific application. (D) The results shown seem to indicate that nonreacting dimensionless scalar profiles can emulate the reacting flow equivalence ratio distribution reasonably well

Summary

Introduction

Jets-in-crossflow have been exteasively treated in the literature. Flows in which this is an integral constituent occur in a number of areas important in combustion and energy science and technology. Several reports and papers have been published since the previous summary was presented that address cylindrical configurations. These include Cline et al ( 1995), Hatch et al (l995a, b), Holdeman et al (l992), Holdeman ( 1993), Howe et al (l991), Kroll et al ( 1993), Leong et al (1995), Liscinsky et al (1993), Oechsle et al ( 19921994), Oechsle and Holdeman ( 1995), Richards and Samuelsen (1992), Smith et al ( 1991), Sowa et al ( 1994), Talpal-. Likar et al ( 1992), Winow ich et al ( L991 ), Yang et al ( 1992), Zhu and Lai (1995)

Description of the Flowfield

Results and Discussion

Orifices

Design Procedure

Summary of Results