Effects of starlike control discs on flow structures and combustion capability

Abstract

The mixing efficiency between the air and fuel play an important role in the combustion capability. The flow structures behind a conventional nozzle were modulated using circular, three-pointed-starlike, and six-pointed-starlike control discs to investigate the characteristic flow behaviors, mixing ability, and combustion capability. The starlike tips generated flow eddies that strengthened the recirculation effect and lowered the stagnation saddle point. The smoke-streak flow structures behind the six-pointed-star control disc were classified as five characteristic flow modes: jet flow, vortex shedding, transition flow, gap flow, and turbulence flow. In the turbulence-flow mode, the turbulence intensity (T.I.) exhibited a considerable increase, and the six-pointed-starlike control disc exhibited the highest T.I. The concentration of CO2 behind the control disc was lower than that behind the conventional nozzles. In the combustion and flame investigation, the direct photograph and Schlieren flame structures show four flame patterns: jet flame, flickering flame, swirling flame and lifted flame. For six-pointed-starlike disc, the flame length is shortened about 44.5%, and the integral combustion capability is doubled with comparing that of pure-jet nozzle due to high turbulence intensity causing the high mixing rate between the air and propane; and then the combustion capability improves. (C) 2021 Elsevier Ltd. All rights reserved.