Hot Streak Characterization of High-Performance Double-Serpentine Exhaust Nozzles at Design Conditions

Abstract

The characterization and mitigation of hot streak phenomena in double-serpentine exhaust nozzles have strategic, operational, and tactical implications for future airborne weapon systems. However, airframe integration increases the risk for material failure due to exposure of downstream components to high-temperature gases from the high-performance convergent-divergent nozzle. The formation of hot streaks must be understood if mitigation strategies are to be developed. To that end, this paper establishes a set of novel characterization parameters based on the temperature distribution and flow conditions at the nozzle exit. Hot streak phenomena observed for a set of serpentine exhaust nozzles with varying geometries are compared using a modified Dean number (called the White number) that accounts for arbitrary cross-sectional area and streamline curvature changes. Using these parameters and computational fluid dynamics, quantifiable differences are observed in the distribution and intensity of hot flow at the nozzle exit. The results show that hot steak phenomena are most prominent for nozzles with a lower White number. The results also provide insight into flow physics acting as primary drivers of hot streak phenomena. The effects of bulk engine swirl are considered and exhibit a significant impact on surface temperature distribution and the formation of hot streaks.