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 design and performance, focusing on oil consumption, supercharging, valve cooling, and fuel economy.
| Identifier | ExFiles\Box 23\4\ Scan071 | |
| Date | 26th February 1932 | |
| -2- was naturally an advantage in giving better heat dissipation from the coolers. They experience the usual variation in oil consumption and the average consumption is about 14 pts/hr. All their larger models, apart from the supercharged engines, have a rotating impeller - or mixer - to assist in distribution. The distribution they claim is very good and greatly assisted by the impeller. The case of the radial engine is, however, different to ours because the cylinders are fed radially from equally spaced ports round the impeller. The supercharged engines do not use diffuser vanes but the delivery space round the impeller expands in section to the delivery ports for each cylinder. Very light valves are used and they are experimenting with sodium filled exhaust valves. One model they showed me was filled from the head end and a taper plug swaged in. This scheme did not look very good but they have not tested this one in an engine. It is interesting to note that they have found no improvement in the reduction of audible detonation by the use of salt cooled valves which is the same result we obtained on the Kestrel. With regard to detonation they place little faith in the audible method of recording and are making tests with thermo couples in the gas starter plug to see the connection between audible detonation and temperature rise. They are at the present time taking a very active interest in fuel consumptions and Major Green says they are going to run us very closely in the question of economy under cruising conditions. He admits it is necessary with air cooled engines to run fairly rich at full power to keep the cylinder and valve temperatures down but under cruising conditions (throttled) they can get down to water cooled figures. Running below weakest maintained - cruising loads - has given them lower cylinder temperatures but a slight increase in valve temperatures. They, however, claim to have sufficient in hand with valves to permit this economy operation. They are going to test out a Farnborough automatic mixture control and hope to be able to arrange a setting permitting sufficient over richness for the full power and "take off" conditions with correction permitting operation below the weakest maintained position when cruising. They are also arranging to do a series of consumption tests in flight with the object of improving range. | ||