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).
Comparison of engine performance and oil temperatures between high and low rate oil circulation systems.
| Identifier | ExFiles\Box 36\2\ scan 224 | |
| Date | 8th June 1929 guessed | |
| contd :- -3- 7/1 but continued above 2500 r.p.m. This would indicate that similar performance could be obtained from our engine by permitting it to operate at a higher speed by means of a suitable air screw. The Napier reduction gear we understand gives approx. the same ratio therefore we could expect approx. the same airscrew efficiency and a reproduction of the 10.A. performance. Some interesting curves were shown to us of oil temperatures taken under precisely similar conditions on each machine. The point of interest lies in the fact that the 7/1 engine had the original oiling scheme - i.e. grooves in bearings and high rate of circulation with 35 lbs/sq.in. pressure - while the 6/1 engine had the later scheme with the oil pipes in the crank pins, the pump reduced to two-thirds the previous size and the pressure 57 to 60 lbs/sq.in. The former we refer to as high rate circulation and the latter as low rate circulation. With the high rate circulation the outlet oil reached a steady temp. of 103°C while the low rate circulation reached a steady temp. of 90°C. The machines were flown simultaneously at the same altitude - 8000 ft. and at the same r.p.m. (2250) The temperature rise across the engine was the same in each case i.e. 9°C but it must be remembered in our case the circulation would be about two-thirds that of the other due to the reduced pump. Assuming the rate of heat dissipation to be proportional to the difference between the mean oil temp. and the air temp. it would indicate an advantage of 14.5% in favour of the low rate | ||