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).
Inadequate fuel supply in supercharger carburetters, specifically regarding the float chambers and needle valve.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan101 | |
| Date | 16th April 1928 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/ACL. c. to BD.{Mr Berend} Wors. c. to [obscured] c. to [obscured] RR.F. SUPERCHARGER CARBURETTERS. FLOAT CHAMBERS AND NEEDLE VALVE. X3933 In a previous report we pointed out that the supercharger carburetter would not supply an adequate amount of fuel for the full power demands of the engine when operating under the minimum specified fuel head of 18". Tests made of the fuel flow through the carburetter proved that the chief restriction took place at the float chamber needle valve seat which allowed a flow of only 234 pts/hr. under a gravity head of eighteen inches and 350 pts/hr. with the needle valve completely removed. As an indication of the fuel demand on the float chamber under flying conditions we may consider the engine operating at full throttle at 10,000 ft. and restoring 480 HP. without use of the mixture control - an assumption which is justified because in practice mixture correction is seldom resorted to much below 10,000 ft. Further assume the ground level specific consumption to be .534 pts/HP/hr. (actual value). The mixture would richen at a rate inversely proportional to the square root of the change in air density and would result in a consumption of approximately 300 pts/hr. at 10,000 ft. Actually during level flight the engine speed would increase with a corresponding increase in the consumption. For ground boosting the demand would be in excess of this and it is naturally [illegible] contd :- | ||