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).
Summary of findings from Langley Field on single-cylinder engine tests regarding combustion chamber design and detonation.
| Identifier | ExFiles\Box 173\2\ img202 | |
| Date | 3rd March 1954 guessed | |
| SGW ORRGE By LRF / HS{Lord Ernest Hives - Chair} / Rm{William Robotham - Chief Engineer} HS.{Lord Ernest Hives - Chair} I. LANGLEY FIELD As you know, Langley Field concentrate on single cylinder work and are more particularly interested in injection generally. However they did a considerable amount of single cylinder work for the Allison Engine and therefore it was interesting to get their reactions on the things we are mostly concerned with, combustion chamber design. Question I. I asked them what improvement with regard to detonation they thought the pent house roof as exemplified by the Allison had over the pancake type as on the Conqueror. Their reply was surprising. They said that given the best spark plug position they would not say that they could tell the difference judging by aural tests. They had got higher B.M.E.P. out of the Allison engine but they attributed this to better volumetric efficiency due to the inclined valves. They asked me why I expected less detonation and it was difficult to tell them. Question II. Asked what they had been able to do with spark plugs with regard to reducing detonation. They carried out a comprehensive investigation with the Allison cylinder. They found that two plugs were greatly better than one but any number greater than two, no matter where placed, made little difference, i.e., two were as good as anything. The best arrangement was diametrically opposite, the difference between different diameters was not very great. One plug could with advantage be fired ahead of the other but was not very sensitive. They had run up to five plugs firing at the same time. Question III. Had they any evidence that turbulence would reduce detonation. Only conclusive evidence on a two stroke petrol injection engine where four poppet valves all exhausted in the head and the inlet charge was taken in radially at the base of the cylinder. By varying the angle of the guide vanes they could cut out or bring up audible detonation at will. Question IV. Did they think the pent house cylinder head had any advantages over the pancake other than improved vol efficiency. Yes, it gave more room for the valves. Question V.{VIENNA} Had they had cracking between the valve inserts. Yes, particularly on their high boost single cylinder units. Every time they were able to bring water passages right down in between the valves the trouble disappeared. When boosting up to 5-7 lbs/sq" they had actually found that they could with advantage make the exhaust valves larger than the inlet valves. | ||