The influence of aspect ratio on the iso-thermal flow characteristics of multiple confined jets

• Published in: Physics of fluids (1994) 2018-12, Vol.30 (12), p.125108
• Main Authors: Long, Shen, Lau, Timothy C. W., Chinnici, Alfonso, Tian, Zhao Feng, Dally, Bassam B., Nathan, Graham J.
• Format: Article
• Language: English
• Subjects: Aspect ratio; Combustion chambers; Cylindrical chambers; Dependence; Flow characteristics; Fluid dynamics; Fluid flow; Inclination angle; Jets; Nozzles; Parameter identification; Particle image velocimetry; Reynolds number; Turbulent flow; Velocity measurement
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.5063500

We report a systematic study of the interaction between four rotationally symmetric jets within a cylindrical chamber obtained with particle image velocimetry, under conditions relevant to a wide range of practical applications including the hybrid solar receiver combustor. The geometry consists of a cylindrical cavity with four inlet jets (representing four burners), which are configured in an annular arrangement and aligned at an inclination angle (αj) to the axis with a tangential component (azimuthal angle θj) to generate a swirl in the chamber. The configurations of αj = 25° were assessed with two azimuthal angles θj = 5° and 15°, a range of chamber aspect ratios (Lc/Dc), and a fixed nozzle Reynolds number of ReD = 10 500. The experimental results reveal a significant dependence of the mean and turbulent flow-fields on the aspect ratio Lc/Dc for the values of αj and θj considered here. Three different flow regimes and their controlling parameters were identified within the range 1 ≤ Lc/Dc ≤ 3. The dependence of the flow characteristics on the chamber length Lc was weak within 1.5 < Lc/Dc ≤ 3, but significant for 1 ≤ Lc/Dc ≤ 1.5. It was also found that the value of Lc/Dc has a controlling influence on the position and strength of large-scale recirculation regions, together with the extent of flow unsteadiness, although this influence is reduced as θj is increased.