Development of Supersonic Convergent-Divergent Nozzle of Rectangular Cross-Section for Cooling Air Grinding

Abstract

This study provides a useful guideline for design of supersonic convergent-divergent nozzle (C-D nozzle) of rectangular cross-section for the cooling air grinding. The C-D nozzles as trial products in various sizes are produced on an assumption of the isentropic flow of the perfect gas. Distributed total pressure of the air flow out of the nozzle is measured to estimate the potential core length LPC. Dependences of LPC on air flow parameters are validated under the correct expansion condition. The frictional exclusion caused near the inner wall is correlated with Reynolds number in physical state of the exit part. It appears behavior of the air flow without the frictional exclusion is in agreement with that of the isentropic flow. Both effects of the taper in the divergent part and aspect ratio of the cross-section at the throat on LPC are clarified experimentally. A proper design procedure, which can determine configuration of C-D nozzle, is shown by arranging the experimental results and is related with required LPC with the optimum air supply condition.