水素ディーゼル機関の基礎的研究 (第1報 -非定常水素噴流の混合気形成の解析-)

In this study, the mixture formation processes of high pressure hydrogen jets were investigated using a constant-volume vessel. The mixture formations of steady gas jets injected into atmospheric pressure ambient are well known. However, there are few works about the mixture formations of high pressure hydrogen jets injected into high pressure ambient. Also, in gas releases having a pressure ratio of exit pressure to ambient pressure greater than 1.89, underexpanded jet will be formed. So the mixture formations of high pressure gas jets are different from those of steady gas jets. Therefore, in this study, the jet flows near the nozzle exit and developing process of high pressure hydrogen jets were observed by shadowgraph photography with changing conditions of injection, ambient, and orifice diameter. In addition, the fuel distributions of unsteady jets were analyzed with Rayleigh scattering measurements. The conclusions of this study are shown as follows: (1) The pressure ratio has significant effects on underexpanded jet structures. (2) The jet penetration predicted by the modified momentum theory was in reasonable agreement with the experimental results for various condition of orifice diameter. (3) In the case of the smaller orifice, comparatively uniform mixtures distributed in the downstream region.application/pd