Characterisation of confinement and impingement effects on the near field of axisymmetric jets
Résumé
Laser Doppler Anemometry and Particle Image Velocimetry are applied to a domestic burner configuration to determine the effect of geometrical
parameters and gas density on the flow field and on the entrainment process. The flow field is that of a confined jet impinging onto a plate. The main design parameters of the experimental devices may be adjusted to modify the confinement ratio and the distance from the outer section of the injector to the stagnation plate. The impinging distance is known to influence the structure of the flow field, mostly when the stagnation plate is in the near field region of the jet. Two density ratios were studied: an isodensity (Rp = l) and a light jet (Rp = 0.55). The two nominal flow rates were investigated, associated with low Reynolds turbulent jets and laminar jets. A totally transparent new device was manufactured in quartz.
This new device presents greater optical accesses for PIV measurements inside the burner. Several configurations were investigated for the different gases and impinging distances: free jets, confmed jets, impinging jets, and confined impinging jets (whole burner configurations). The effect of burner geometry and gas density on the flow field and on the entrainment process is determined.