A DIMENSIONLESS DESIGN FRAMEWORK AND MECHANISTIC STUDY OF A PERFORATED-WALL TRANSVERSE-JET MIXER FOR RAPID COOLING OF HIGH-TEMPERATURE GAS STREAMS

Abstract

In conventional aero-engine testing, the combustor and afterburner are usually evaluated separately, which increases cost and energy consumption because two high-temperature sources are required. This study proposes a flange-type mixer for integrated testing, in which ambient air is transversely injected to cool the combustor exhaust through jet-induced mixing. RANS simulations were conducted for 16 flange configurations at a jet-to-mainstream temperature ratio of 0.14 and a mass flow ratio of 1.0, and the numerical approach was assessed against experimental measurements. The results show that mixing is strongly affected by the number of holes and the momentum ratio, and is further influenced by the inlet-pipe-to-hole feeding characteristics of the flange. Recirculation occurs only when the momentum ratio is 3009 and the number of holes is 36 or less, but it does not result in distinctly better mixing. Meanwhile, azimuthal asymmetry and hole-to-hole maldistribution may, in some cases, enhance downstream mixing by producing alternating strong and weak jets and locally increasing penetration. To unify jet-trajectory behavior across configurations, a nondimensional analysis was conducted, and a modified Holdeman-type trajectory correlation was developed for the present confined circumferential injection. In addition, a feeding-imbalance index was proposed. When combined with the penetration metric, it improved the correlation with mixing performance. These findings provide guidance for the design of compact mixers for high-enthalpy integrated test systems.