The effect of aspect ratio on the flow characteristics of a Hybrid Solar Receiver Combustor

Abstract

We present a systematic experimental study of the interaction between four rotationally-symmetric jets within a cylindrical chamber, under conditions relevant to a wide range of practical applications, including the Hybrid Solar Receiver Combustor (HSRC). The HSRC geometry is simplified here to 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. In this study, we assess the configurations of αj = 25° and θj = 5°. The length of the chamber was varied from Lc = 148 mm to 74 mm and the diameter of the chamber was Dc = 74 mm, resulting in an aspect ratio of Lc/Dc = 2, 1.5 and 1. The inlet Reynolds number for each injected jet and the number of jets were fixed at ReD = 10,500 and 4, respectively. Velocity data obtained with Particle Image Velocimetry (PIV) were used to characterise the large-scale flow field within the selected experimental configurations. The results reveal a significant dependence of the mean flow-field on the aspect ratio Lc/Dc for the value of αj and θj considered here. More specifically, it was found that Lc/Dc can influence the position of the external recirculation zone (ERZ), the strength of the central resulting jet, and the recirculation rate (Kv).