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).
Calculation of the performance of an Autovac fuel system at high altitudes.
| Identifier | WestWitteringFiles\J\May1923\ Scan39 | |
| Date | 9th May 1923 guessed | |
| ACTION OF AUTOVAC AT HIGH ALTITUDES. The ratio of the pressure in the inside of induction manifold to that on the outside will remain constant. Proved by Mr. Clerk for streamline flow and may be taken to hold good for this particular case. The quantity of petrol supplied by Autovac will vary as the sq.root of the pressure difference. By pressure difference is meant the suction head of petrol minus the head of petrol in the Autovac feed pipe - or :- Q ∝ √H - h where H = suction on petrol in ins. water. h = head of petrol in pipe reduced to ins.water. ∴ Q will be reduced by the ratio √((Ha - h) / (Ho - h)) { Ha = suction at alt. a.{Mr Adams} , Ho = suction at sea level Take an altitude of 10,000 ft. Atmos. pressure = 9.7 lbs.sq.in. approx. ∴ H 10,000 / Ho = 9.7 / 14.7 In the case of a tank half-full - Ho at 2000 R.P.M. = 92 ins. water. ∴ H 10,000 = (92 X 9.7) / 14.7 = 60.71 ins. water. ∴ Q at 10,000 to 2000 R.P.M. = Qo √((60.71 - 19.89) / (92 - 19.89)) = 72.2 √ (40.82 / 72.11) = 54.31 pts/hr. ∴ 54.31 pts/hr. at 10,000 ft. against 72.2 pts/hr at sea level at 1000 R.P.M. = 20.75 pts/hr. ACL. | ||