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).
With calculations regarding vane dimensions and airflow characteristics for a supercharger.
| Identifier | ExFiles\Box 42\3\ Scan047 | |
| Date | 1st December 1926 guessed | |
| contd :- -2- vanes to the exact dimensions as given by R.A.E., due to inter- fe-rence. The vanes we have not got are shewn in accompanying figure. The throat of the venturi formed by adjacent vanes is out of position and also wider than the dimension recommended. The clearance between the rotor and the vanes is also greater than recommended. Estimation of width required at throat of vanes. Assumed peripheral velocity of rotor = 810 ft/sec. Velocity along vane axis at throat = 810 / (cos 9o 42') = 822 ft/sec. Air passing through supercharger = 56 lbs/min. Assumed density at vane throat = .064 lbs/su.ft. Volume of air passing diffuser throats = 56 / .064 = 875 cu.ft/min. Let N = number of vanes. x = width of throat. Then vane area at throat normal to gas flow = (Nx X .55) / 144 sq.ft. Volume of air passing through throats = velocity X area of throat ∴ 875 = (822 X Nx.55) / (60 X 144) ∴ Nx = 4.65 sq.ins. If N = 39 Then x = .119" This value of x is considerably lower than the dimension of .200" as given by R.A.E., and allowance must probably be made for the loss in velocity in the clearance space. We suggest that we make an experimental diffuser with the same vane angles as we now possess, but with a throat width of .150". contd :- | ||