Physics-based Scaling Laws for Confined and Unconfined Transverse Jets.

摘要

An experimental study was conducted to explore the mixing properties of single and multiple confined transverse jets. A new physics-based scaling law variable was developed based on unconfined transverse jet trajectories. This variable accounts for both entrainment and drag momentum transport mechanisms which cause the jet deflection. The utility of this parameter under confined conditions was considered. It was observed that this new scaling parameter does correlate both qualitative and quantitative measures of the mean mixture properties, in particular prior to any jet-wall interactions. It was found that no local optimum mixing condition was present for two and three jets. For six jets, the behavior changed dramatically, with the emergence of a local optimum mixing state that is consistent with previous data collected for gas turbine geometries (Holdeman 1993). It is apparent that the local optimum observed for six jets involves jet penetration to a finite radial position while spreading in the cross plane, leading to the jets blending together resulting in a highly uniform mean mixture fraction distribution. When the number of jets is three or less, this blending process cannot occur due to the excessive distance between the jets. Jet impaction at the pipe center facilitates mixing for two and three jets, while degrading uniformity for six jets.