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).
Proposed scheme for improvements in carburetter design.
| Identifier | ExFiles\Box 5\4\ 04-page224 | |
| Date | 13th December 1929 | |
| HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} MR. CLAREMONT. FROM R.{Sir Henry Royce} Copy to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} S. X5080 RS{Sir Henry Royce's Secretary}/M3.12.29. X.7080. X.5080. IMPROVEMENTS IN CARBURETTERS In motor car work the call for power from the engine varies very greatly, namely, at all speeds with all loads, from the engine idling round slowly with the throttle nearly closed, to the highest engine revs. with the throttle wide open, so that it makes the carburetter problem a particularly exacting one, as at all these demands the mixture strength should be maintained at the best possible proportions - (Correct metering), and the atomization good, (requiring maintained vigorous suction.) My impression is that the above cannot be obtained entirely satisfactorily with a carburetter of the fixed type (i.e. fixed size of air passages, and fixed size of fuel jets.) Also there are disadvantages in most of these known as the expanding type, in which the air and fuel passages increase from zero upwards with the speed of the engine. In this attempt to solve the difficulty I use a carburetter of the fixed type, but much too small for the full speed, full throttle work, (i.e. full HP,) and supplement this (in effect increasing its size) by increasing both the air and fuel passages. It has the following combination- (1) The usual slow running device, its action controlled by the closing of the throttle (throttle edge carburation) (2) A main venturi of from one third to one half the area necessary for full speed and power. (3) An extra air valve of much larger capacity than is usual (i.e. to correct the natural increase in mixture strength.) This extra large increase of extra air is permissible, and becomes possible because of (4) (i.e. the auto: expansion of the fuel restriction.) (4) A main jet or standpipe in (2) preferably of the emulsion type, fed from a restriction which is controlled automatically with the movements of the extra air valve. It will be noted that this scheme avoids the difficulty of an entirely expanding carburetter from near zero, which is very susceptible when it is at its smallest openings, because in the scheme here proposed these are fixed quantities which can be set once and for all time. (1) | ||