Abstract
Cooling air jet turning needs to develop a supersonic nozzle that is capable of supplying high speed air jet at turning point. In this study, supersonic Convergent-Divergent nozzle (supersonic C-D nozzle), which can make stagnation-cold-air up to the sound speed in the convergent section and expand the cold air to supersonic speed in the divergent section, are designed on an assumption of thermal equilibrium under isentropic expansion (no change in entropy). Experimental evaluation of the supersonic air jet clarifies that the C-D nozzle is more advantageous than present convergent nozzle for the cooling air jet turning since the potential core of the C-D nozzle goes over 13 mm (max. 37 mm). As for cooling ability of the cold air jet in the potential core, average heat transfer coefficients of the cold air jet are 1,000-1,400W/(m2K) depending on both pressure of chamber p0 and impinging jet air P. The optimum supply condition of each nozzle is verified experimentally and expressed using non-dimensional parameters, Reynolds number Re and Nusselt number Nu.
