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).
Engine tests concerning fuel accumulation in the volute, carburettor positioning, and venturi efficiency.
| Identifier | WestWitteringFiles\U\January1930-April1930\ Scan072 | |
| Date | 25th January 1930 | |
| -2- in excess of that actually experienced on the engines. As an average - in cold damp weather, the worst conditions - we find about 55 to 60 c.c. collect in the volute in 15 mins., idling at about 600 r.p.m. If we turn to the curve showing the fuel delivery plotted against induction pipe depression, we see that the unit is capable of working well in excess of any amount which would accumulate in the volute. Another important point brought out by these tests which should be considered when arranging the position of the unit on the engine, is that the efficiency is considerably increased by having a petrol head on the venturi (See our previous memo HS{Lord Ernest Hives - Chair}/ACL/MJ. 25.1.30) This means that the unit should be positioned below the volute. Probably it could be built on, or form, part of the bottom half of the carburetter. This would save one pipe, viz. the connection pipe to the carburetter intake, and probably another because the drain passage from the volute could be formed in the castings. Another point is that the venturi needs accurate finishing. Roughly formed venturi contours and inaccurately drilled fuel holes quickly impair the efficient operation. Since writing the above we have carried out some tests with this scheme on an engine on the hangar and obtained very good results. First of all we ran an engine, with the suction drain in operation, for a quarter of an hour at ticking over speed (600 r.p.m.) with the idling mixture set over rich. At the end of this time the engine was stopped when only 4 c.c. of fuel was | ||