Nozzle Exit Flow Characteristics for Square-edged and Rounded Inlet Geometries

Abstract

This study was conducted to provide some insight into effects of nozzle inlet shape on turbulent flow characteristics. It was motivated by the recognized importance of nozzle geometry on atomization and subsequent combustion of liquid fuels. Flow coefficient and nozzle exit turbulence data have been obtained with incompressible air flow in two nozzles having rounded and and square-edged inlet geometries respectively. Photon correlation laser Doppler velocimetry was used to measure the mean velocities and turbulence intensities. For operation with equal mass flow rates, the square-edged inlet nozzle requires a greater pressure drop and produces higher turbulence intensities than a nozzle with a well rounded inlet. The higher turbulence level which we observed with the square-edged inlet nozzle correlates with wider spray dispersion angles observed by Reitz and Bracco (1979) as the nozzle inlet radius is decreased.