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).
Carburettor design, fuel metering, and a comparison with Pratt & Whitney and Bendix systems.
| Identifier | ExFiles\Box 27\3\ Scan232 | |
| Date | 15th May 1939 guessed | |
| 26 It is important to realise that the fuel metering device is not affected by the actual fuel pressure, but by the pressure difference acting on the control diaphragms. With the fuel pressure capable of being raised, no trouble from boiling of the fuel at the injection nozzle need be experienced. The accompanying sketch shows the basic principle of the carburettor. No boost control is fitted at present, but its incorporation should present little difficulty. '' In a short discussion with Mr.Mock whohas developed the carburettor, he said that considerable difficulty had been experienced through poor air distribution through the blower, especially at low throttle openings, and that means were being developed to improve the distribution. Mr.Hobbs was also very satisfied with the automatic power and mixture control which Pratt & Whitney have had in use for some years on the old float type Stromberg carburettor. The Navy is making regular flights of 4-engined flying boats to Honolulu, over 2000 miles, and on these flights the consumption of the four engines does not vary by 10 gallons. Americans were inclined to be amused at our much wider variations. They place a great deal of reliance on the exhaust gas analyser, which they say is accurate down to a fuel-air ratio of .068,(14.7:1). Pratt & Whitney claim a cruising consumption of .42 lb/HP/hour, and an average consumption, block to block including take-off and climb, of .45 lb/HP/hour. On the test bed they prefer to work to fuel-air ratio rather than fuel flow, and their test beds are all equipped with air flow meters. The Bendix people are now producing a version of the automatic power and mixture control which is not quite so accurate as that used by Pratt & Whitney. | ||