From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page discussing the principles of gas flow through an ideal expanding nozzle and a sharp orifice.
| Identifier | ExFiles\Box 36\1\ scan 021 | |
| Date | 1st February 1919 | |
| Contd. -9- afterwards an increase and this variation of area determines the ideal nozzle for an expanding gas. [Diagram of a converging-diverging nozzle with labels A, B and flow arrow] The discharge of gas per unit area of cross section greatest at the throat of this nozzle, and the pressure at the throat bears to the internal pressure the limiting ratio ( 2 / (n+1) ) ^ (n / (n-1)) Returning to the case of the sharp orifice, when P2/P1 is less than this limiting ratio, the stream adjusts itself so that the pressure at the vena contracta is equal to the external pressure and the vena contracta of the stream corresponds under these circumstances to a cross section of the ideal nozzle occurring before the throat as at AA{D. Abbot-Anderson} above. When P2/P1 - this limiting ratio, the vena contracta of the stream corresponds to the throat of the ideal nozzle and the vena con-tracta or throat pressure is the external pressure. But when P2/P2 is less than the limiting ratio the vena contracta still corresponds to the throat of the ideal nozzle, and not to a cross section of the nozzle occurring after the throat as at BB. For now the expansion of the gas during passage through the vena contracta causes the gas particles in describing curved paths, to produce by their centrifugal | ||