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).
The design and performance of different cylinder heads and combustion chambers.
| Identifier | ExFiles\Box 134\2\ scan0006 | |
| Date | 19th March 1935 | |
| -2- possible to pick out potentially smooth and potentially rough combustion chambers from a series by using these curves. Attached are such curves plotted for the standard Bentley and Ramp Cylinder Heads. An attempt to plot a similar curve for the high power head had to be abandoned owing to the difficulty of calculation, but as a first approximation it appeared to show a greater rate of increase of volume with flame travel than the standard Bentley head. It is suggested that a plaster cast might usefully be made of the high power head combustion chamber and cut with a spherical cutter, to obtain its volume distribution with relation to the sparking plug. An examination of the curve shows the potentially smoother operation of the ramp head. It would appear that the high power head might be improved from this point of view by modification in plug position, but it should be appreciated that the plug on the far side, which already exists in the head and which one would anticipate is in a suitable position for smoothness of combustion, has already been tested, and it has been found that the engine would not run steadily on this plug. Ricardo also found that with this type of cylinder head it was essential to have the sparking plug in such a position that it was swept by the flow of mixture through the throat. It is suggested that the two-valve ramp head might be given some further consideration, particularly as it has a potentially smooth type of combustion chamber. Also, the maximum valve sizes which can be used are not limited by the length of the engine as they are on our existing designs. We feel that it is very desirable that if we are to depart from our present well tried design of car cylinder head, it should definitely be towards a smoother head, as apart from limitations on valve diameter, the only criticism which can be made against the standard turbulent head is that it is not particularly smooth. E/PSN. | ||