Compressible Gas Flow in Nozzle Taking Boundary Layer into Consideration : (Part 4, The Case of Fully Developed Laminar Layer, Experiments with Ring-Nozzle, and General Conclusion)

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  • 境界層を考えた圧縮流体のノズル内流動 : 第4報, 完全に発達した層流の場合と総合結論
  • キョウカイソウ オ カンガエタ アッシュク リュウタイ ノ ノズル ナイ リュウドウ 4

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The longitudinal velocity and the pressure distribution of compressible gas flow passing through a small nozzle are mainly determined by the characteristic Reynold's Number RεN=(S2/L) (us0/v0) (us0, v0 are the local sonic speed and dynamic viscosity of gas before entering the nozzle respectively, S, L are the hydraulic radius and length of nozzle respectively) The cases for ReN>10 and 0.7<fb<1.4 (fb is the convergency of nozzle) were already covered by the previous reports of these series. In the present report, the remained case for ReN<10, where the fully developed boundary layers of both walls contact with each other as in the case of the Poiseuille's flow, is analysed theoretically. The flow coefficient, mean pressure, and the critical back pressure in this case are calculated and added to the results of previous reports to complete the full theoretical curves of the performance of nozzle flow. Experiments are conducted using a ring-nozzle with atomospheric air sucked by a steam ejector. Their results show good agreements to the theory. The main results are as follows : the change of mean pressure is not so steep against ReN, while the flow coefficient and critical back pressure show considerable decrease in the range of 10>ReN>0.5.

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