Based on the experiences previously obtained from the experimental study of plain jet atomization under cross flowing air stream and under supersonic air flow, the authors designed and studied a serious of internal mixing sonic flow air assist atomizers for heavy oil application. The contradiction between the requirements for fine spray (for high combustion completeness) and for long flame (for flame rigidity) often existing in industrial furnace has been solved. Good data were obtained which can be used for the design of such kind atomizers. By properly choosing the configuration and geometrical dimensions of the atomizer, also by choosing suitable values for mixing chamber pressure, air–liquid ratio, it is possible to have very fine spray and desirable flame length. The results showed that the ratio of mixing chamber pressure to air supply pressure should be in the range of 0.6 to 0.7. For atmospheric pressure combustion furnace, such air assist atomizer needs 0.4 MPa compressed air to have sonic flow at nozzle exit. This type of air assist atomizer has already been put into industrial operation.

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