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).
Report discussing fuel vaporization methods, including hot spots, vaporizers, and weirs for engine carburetters.
| Identifier | ExFiles\Box 75\2\ scan0310 | |
| Date | 9th September 1921 | |
| contd. -2- This is dependent on the principle of re-blowing, and fails of course at low speeds full throttle. Still, one can believe that it would do a lot of good on the average car, and I am going to get a set for mine as soon as it is available for my type of car. It is quite similar to your "weirs", We believe that the vaporiser scheme is right and sufficient without the hot throttle. Caswell has started warm and run without excessive sooting up (though with a lot of exhaust smoke) on straight kerosene, with the vaporiser scheme without any other source of heat except the standard carburetter water jackets and low-speed hot-air intake. The hot spot idea has always been to evaporate the fluid without heating the gas, and the vaporizer scheme seems the only way to do this effectively. The hot spot idea attempts to do this in a less effective way, and we think is superfluous when a properly devised vaporiser scheme is used. Starting is easy with your pilot jet scheme and a vaporizer to catch the "slugs" of liquid fuel, which otherwise do all the damage and which the ordinary hot spot scheme does nothing to prevent because it does not get hot in time. Again, there always is, and always will be, a proportion of light constituents in the gasoline which will make starting possible without the addition of heat, because the oil companies have to unload this light stuff somewhere, since they are not allowed to put it in kerosene. You will say, quite rightly, that we have laid stress on the necessity for getting "dry" gas into the cylinders, and now that you have given it to us, we say we don't want it but are content to collect the liquid off the walls, and let it go at that. I admit the inconsistency, but we have found the internal condition of the cylinders so remarkably good after over 2000 miles running with the vaporiser scheme without other means of heat, that we have come to believe that the "core" of mixture which enters the cylinders is virtually dry (or so thoroughly atomized as to be readily fired) and that the liquid stuff is practically all on the walls. So that, with the use of your weirs, we should expect very excellent results indeed without the hot throttle. The "dryness" of our mixture (not taking account of the fluid on the walls) ought to be excellent as compared with the average car (a) because of the atomizing effect of our ring-type jets, which we know to be very good as compared with the conventional pin-hole jets, and (b) because our induction pipe is so long and has so many kinks and bends in it, that any liquid drops contd:- | ||