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

本研究的目的是开发一种适用于高效率工业机械的超音速塞式喷嘴系统，包括吹灰器、气体雾化、喷嘴和高速氧气燃料涂层。阐明了由于多股气流在同一管道内汇合而产生的堵塞现象，即复合流堵塞现象，对超音速塞式喷管系统的发展具有重要意义。为此，我们在塞式喷嘴的基础上，开展了复合堵塞的研究。(1)通过TVD数值计算定性地阐明了塞式喷管中过膨胀、正确膨胀和欠膨胀的流动特性。(2)研究了圆柱体在正确膨胀的超音速射流中的绕流特性。结果表明，圆柱体上的压力系数比用势流理论得到的结果要小，特别是当圆柱体位于射流的势核区时。圆柱体上的速度分布强烈地依赖于圆柱体前方激波下游的流动马赫数。(3)采用考虑两股流混合的简单流动模型，计算了复合堵塞发生在出口时的临界压力比。计算结果与实验数据吻合较好。(4)复合堵塞时，在出口下游观察到的激波形式几乎与管道中心线对称。TVD计算结果与实验结果一致。(5)可以用复合声波的一维理论定性地解释复合窒息现象。

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.