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).
The S.U. Automatic Carburetter for aero engines, detailing its design, operation, and advantages.
| Identifier | ExFiles\Box 31\5\ Scan277 | |
| Date | 20th December 1934 | |
| AERO ENGINES. S.U. AUTOMATIC CARBURETTER. INTRODUCTION. The S.U. carburetter Company have submitted for test and development, an aero engine carburetter which is entirely automatic in its action as regards maintaining the correct mixture proportions at altitude and also for providing an aneroid mixture for high boost conditions. This design has been put forward to meet the increasing demand for fuel economy of aircraft for the purpose of increasing the range, and being self-contained, eliminates the fitting of the Hobson Penn and similar automatic control units which are being advocated by the Air Ministry as separate control units for our own aero engine carburetters. DESCRIPTION. The carburetter, which is adapted to fit a Kestrel Vl.{V. Lewis / Mr Valentine} engine, consists of the usual type of float chamber, diffusers etc., and has two main jets, the orifices of which can be varied by tapered needles. These tapered needles are regulated automatically through the medium of aneroids which are enclosed in cylindrical chambers in the carburetter body, one of the aneroids being open to the intake pressure the variation of which allows the aneroid to expand or contract and the movement is transmitted by suitable links to the tapered needle to maintain the correct fuel flow at altitudes. The other aneroid which is similarly disposed is connected to the pressure side of the blower. This aneroid is adjusted to a predetermined pressure and any pressure in the induction pipe in excess of the aneroid pressure will compress the aneroid and regulate the needle to increase the orifice and so increase the fuel flow for excess boost pressures. ADVANTAGES. It will be noted from the description that the whole functioning of the carburetter is self controlled and as the initial setting consists of adjusting the tapered needles to a specific consumption/power output basis, the functioning of successive carburetters is identical, dependent only on the accuracy of the tapered needles, which can be guaranteed. The uniformity of each engine as regards fuel flow is the chief advantage to be gained, plus the automatic richening which will adjust itself progressively for any boost pressure to the extent of allowing full throttle take off conditions. | ||