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超音速塞式喷嘴系统，用于工业机械的高效率，包括吹灰器，气体雾化，射流燃烧器和高速氧燃料涂层。已经阐明，由于一些流在单个管道中汇合而导致的阻塞现象，即，复合流阻流现象对超音速塞式喷管系统的发展具有重要意义。为此，我们在研究塞式喷管的同时，也进行了复合扼流的研究。现将本研究得出的结论总结如下。（1）通过TVD数值计算，定性地阐明了塞式喷管过膨胀、正确膨胀和欠膨胀流动的特性。（2）研究了超声速适当膨胀射流中圆柱的绕流场。计算结果表明，当圆柱位于射流势核区时，圆柱上的压力系数比用势流理论得到的压力系数小。圆柱体上的速度分布强烈地依赖于在圆柱体前面产生的激波下游的流动马赫数。（3）采用考虑两股气流混合的简单流动模型，计算了收敛通道出口发生复合阻塞时的临界压比。计算结果与实验数据吻合较好。（4）复合扼流时，在出口下游观察到的激波形状相对于管道中心线几乎是对称的。TVD计算结果与实验结果一致。（5）可以用一维复合声波理论定性地解释复合扼流现象。

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.