Spray Characteristics of CWM by a Pneumatic Internal Mixing Atomizer.

Abstract

This paper describes pneumatic atomization test results of Coal-Water-Mixture (CWM) conducted at Babcock-Hitachi K.K. The main purpose of our study is to delineate the effects of CWM properties and the atomizer structure on spray characteris-tics.In order to obtain the necessary data concerning the structure of atomizers and to de-termine the optimum atomizing conditions, numerous experiments have been carried out under various liquid flow rates and air-to-liquid mass ratios using water instead of CWM for various types of internal mixing atomizers. As a result, it has been clarified that ato-mization improves as the liquid flow rate increases provided that the air-to-liquid mass ratio is kept constant. The optimum configurations of the exit ports has been determined ex-perimentally in the aim of reducing spray droplet sizes.The test results achieved in the experiments using various CWMs suggest that pseudo-plastic CWMs are easier to atomize than CWMs of other apparent rheological characteris-tics; that is, pseudo-plastic CWMs reduce the amount of coarser droplets produced by disin-tegration of film-like CWM at the exit ports of the atomizer.The mathematical expression of the spray mean droplet sizes of CWMs and water de-rived from the present study for pneumatic internal mixing atomizers correlated with the test results.