Experimental and numerical investigation of the iso-thermal flow characteristics within a cylindrical chamber with multiple planar-symmetric impinging jets

Abstract

We present a joint experimental and numerical study of the flow structure within a cylindrical chamber generated by planar-symmetric isothermal jets, under conditions of relevance to a wide range of practical applications, including the Hybrid Solar Receiver Combustor (HSRC) technology. The HSRC features a cavity with a coverable aperture to allow it to be operated as either a combustion chamber or a solar receiver, with multiple burners to direct a flame into the chamber and a heat exchanger that absorbs the heat from both energy sources. In this study, we assess the cases of two or four inlet jets (simulating the burners), configured in a planar-symmetric arrangement and aligned at an angle to the axis (αj) over the range of 0°–90°, at a constant inlet Reynolds number of ReD = 10 500. The jets were positioned in the same axial plane near the throat and interact with each other and the cavity walls. Measurements obtained with particle image velocimetry were used together with numerical modeling employing Reynolds-averaged Navier-Stokes methods to characterize the large-scale flow field within selected configurations of the device. The results reveal a significant dependence of the mean flow-field on αj and the number of inlet jets (Nj). Four different flow regimes with key distinctive features were identified within the range of αj and Nj considered here. It was also found that αj has a controlling influence on the extent of back-flow through the throat, the turbulence intensity, the flow stability, and the dominant recirculation zone, while Nj has a secondary influence on the turbulence intensity, the flow stability, and the transition between each flow regime.

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

“…The experimental studies of Boushaki and Sautet 4 employing Particle Image Velocimetry (PIV) showed that an increase in α j from 0 • to 30 • leads to a significant increase in the magnitude of mean and turbulent velocity fields within the jet merging region. Similarly, the PIV measurements of Long et al 10,11 found a strong dependence on jet angles (α j and θ j ) of the instantaneous and mean flow-fields generated with multiple symmetric jets. However, to the best of our knowledge, little or no information is available for the key geometrical parameters (e.g., L c and D c ) of the confined space for multiple jet configurations, although the aspect ratio of geometry has been found to have a significant influence on the flow-fields of free jet impingement [17][18][19] and cavity flow.…”

“…The present experimental arrangement is similar to that reported previously, 10,11 so only the key experimental apparatus and parameters are described here. Planar Particle Image Velocimetry (PIV) was employed to investigate the mean and RMS flow-fields with the MIJCC configurations.…”

“…7 Of particular interest here are those configurations featuring multiple jets of relevance to the Hybrid Solar Receiver Combustor (HSRC) under development at the University of Adelaide. [8][9][10][11][12] This device features a cavity that is operable as either a solar receiver or a combustion chamber equipped with multiple burners to direct fuel and air into the main cavity and tubular heat exchangers to transfer the thermal energy to the heat transfer fluid. The burners are configured in an annular ring and aligned at an inclination angle (α j ) relative to the axis of the cavity and/or at an azimuthal angle (θ j ) relative to the axis of the burner, resulting in a swirling flow within the main cavity.…”

“…Previous investigations of the flow-fields within the HSRC revealed a significant effect of the jet angles (α j and θ j ) on the strength and position of the large-scale recirculation which is critical for achieving desirable flow regimes. 10,11 In addition, the aspect ratio of L c /D c has a strong influence on thermal efficiency and a) Author to whom correspondence should be addressed: shen.long@adelaide. edu.au capital cost.…”

“…Previous studies of flow-fields generated with multiple symmetric jets within a confined space revealed that the flow structure depends strongly on the arrangement and geometrical features of jets. 3,4,10,11,[13][14][15][16] Chammem et al 3 defined the flow structure downstream from the jet impingement point (P i ) as the "resulting jet flow" and that upstream as the "upstream reverse flow" noting that these flow features are significantly influenced by α j . The experimental studies of Boushaki and Sautet 4 employing Particle Image Velocimetry (PIV) showed that an increase in α j from 0 • to 30 • leads to a significant increase in the magnitude of mean and turbulent velocity fields within the jet merging region.…”