Development of Supersonic Plug Nozzle System for High Efficiency of Industrial Machinery including Sootblowers

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The purpose of the present investigation is to develop a supersonic plug nozzle system for high efficiency of industrial machinery including sootblowers, gas atomization, jet burner and high velocity oxygen fuel coatings. It has been clarified that the choking phenomena due to the confluence of the some streams in a single duct, i.e., compound flow choking phenomena are of importance to develop the supersonic plug nozzle system. Therefore, we have carried out a study on compound choking as well as on a plug nozzle. The conclusions obtained in the present study are summarized as the following.(1)The characteristics of the overexpanded , correctly-expanded, and underexpanded flows from a plug nozzle have been qualitatively clarified by TVD numerical computations.(2)Flowfield around a circular cylinder placed in correctly-expanded supersonic jets has been studied. As the results, the pressure coefficient on the cylinder is found smaller than that obtained by potential flow theory around a cylinder, especially, when the cylinder is located in the potential core region of the jets. The velocity distribution on the cylinder strongly depends on the flow Mach number just downstream of the shock wave generated in front of the cylinder. (3)The critical pressure ratio across a convergent duct when the compound choking occurs at the duct exit were calculated by a simple flow model where the mixing of the two streams was taken into consideration. The calculated results agree well with the experimental data. (4)The form of the shock waves observed downstream of the duct exit when compound choking occurs is almost symmetric with respect to the duct centerline. TVD computation shows the same results with the experiments. (5)One can qualitatively explain compound choking phenomena by a one-dimensional theory of compound sound waves.