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).
Visit to Coventry Climax Engines Ltd. to discuss the O.H.1 engine design, covering cylinder head form, plug position, and throat size.
| Identifier | ExFiles\Box 134\2\ scan0090 | |
| Date | 9th November 1936 | |
| FILE, IVOT SENT OUT. 1129 9.11.36. COVENTRY CLIMAX ENGINES LTD. On the 5th inst. a visit was paid by the writer and Mr. Pearson of the Design Dept. to the above firm for the purpose of discussing the O.H.1 type of engine which Messrs. Coventry Climax Ltd. have put into production. Numerous points were discussed with Mr. Lee the chief engineer and Mr. Wooddisse, the chief designer, amongst which were cylinder head shapes and forms and the critical points thereof, throat gas velocities, valve temperatures, smoothness, and various other items. It is now proposed to deal with these in detail. Cylinder Head Form. It is necessary in designing the combustion space to take care that no organised swirl in either a horizontal or vertical plane takes place, or the engine becomes fluffy at the higher speeds. Various head designs were shown us, and it would appear that taking them all round, the combustion chamber form, at present in use on our unit, is as good as any. A figure of merit for the cylinder head shape was suggested by Mr. Wooddisse, and consisted of graphing the ratio of the maximum pressure to the I.M.E.P. against the speed, and the flatter this curve turned out to be the more efficient the head. It is proposed to try this out on our own engines as it appears that it would probably give us a tentative figure of merit for smoothness. Plug Position. It was noticed that most of the plugs were situated about the centre of the head, between the throat and the exhaust valve. However the information given on that point was uncertain and no definite conclusions could be drawn. Throat Size. It seems that this size is very critical, both from the smoothness point of view and for high speed detonation which has been experienced by the Coventry Climax as well as ourselves. They use a throat gas velocity of approximately 60 ft/sec/1000 R.P.M. equivalent to about 52.5 ft/sec/1000 R.P.M. for our unit. Actually our velocity through the throat is about 45 ft/sec/1000 R.P.M. and it would appear that a slightly higher velocity might prove advantageous. In any case a different size of throat would probably do away with high speed detonation, though whether smaller or larger would best be determined by trial and error. continued. | ||