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 detonation tests, focusing on the effects of ignition plugs and engine speed.
| Identifier | ExFiles\Box 1\3\ B001_X 93-page47 | |
| Date | 1st March 1926 guessed | |
| contd :- -3- jackets and find that if anything it is slightly less than when we run on benzol which eliminates detonation. During this test it was found that if we fitted ignition plugs which cause pre-ignition, the heat flow to the jackets immediately went up. We have one particular set of plugs which, although one could not appreciate the pre-ignition, the heat flow consistently went up 100 B.T.U's with these plugs compared with standard plugs. We do not think that these results would apply to all engines. For instance, on our aero engines, if we get detonation, the power immediately drops. (2) The factor of engine speed on detonation is usually disregarded by investigators on this phenomenon. We however made the following test and proved that speed is a definite factor. For this test the I.M.E.P. was kept constant over the whole range of speed by adjustment of the throttle. We proved conclusively that as the speed increased, detonation became less audible. Detonations disappear when a speed of 1750 r.p.m. was reached. The constant I.M.E.P. was 110 lbs. Keeping the I.M.E.P. constant seems to be an important point because for a given set of conditions the pressure appears to have considerable influence on detonation. We think the fading away of audible detonations with increase in speed is mostly due to greater turbulence and not due to a higher rate of pressure drop in relation to time caused by the greater piston speed, because detonation pressures of very high values have been observed on indicator diagrams and this has taken place at practically constant volume before contd :- | ||