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 merits of an exhaust-heated throttle compared to a vaporizer scheme and hot air methods for fuel delivery.
| Identifier | ExFiles\Box 75\2\ scan0273 | |
| Date | 5th October 1921 guessed | |
| .. Oyl - G 51021 Sheet #3. This car was fitted with collector rings. of the second type illustrated in print No. XA-1289 so that it proves that these are very effective. We are sure from previous experiments that without the collector rings the cylinders would have been slightly wet, although not nearly so wet as with the standard induction pipe. 3. Exhaust Heated Throttle: We do not think that the exhaust heated throttle is the right thing to combine with the vaporizer scheme, because the exhaust heated throttle is designed to heat the fuel without considerably heating the air. The vaporizer scheme does the same thing in a more effective way. I think that the ideal combination would be the vaporizer for collecting and boiling off the liquid fuel combined with a very effective supply of hot air to the carburetter, at all positions of the throttle before half open, and a supply of cold air to the carburetter at throttle positions from half to full open. The advantage of hot air at partial throttles is that it raises the compression pressure for a given development of power and so raises the efficiency of the engine at partial throttles to a considerable extent. Prof. Anderson is heating the air to a temperature of 400°F.{Mr Friese} at partial throttles. The hot air appears to be a most efficient way of evaporating the gasoline if it is combined with a jet which properly sprays the gasoline into small drops. This is proved by the fact that a blast of hot air is the most effective means used by the gasoline companies for cracking crude oil, the retort method of cracking having been abandoned in favor of the air blast method. Air is used for this purpose at a temperature of 1000°F.{Mr Friese} or more. Another advantage of the hot air is that it is more sensitive to changes in conditions. What I mean to say is that when the throttle is fully opened, the air is immediately cold and available for developing the full power, whereas with any hot spot scheme the device remains hot for a considerable time after opening the throttle. The reverse is equally true when the throttle is closed from full open to half open - the air is immediately hot as is required for efficiency, whereas with the hot spot it takes some time to heat up. | ||