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 valve timing, noise reduction, and the introduction of Venturi valve seats with a diagram.
| Identifier | ExFiles\Box 134\1\ scan0009 | |
| Date | 14th July 1937 | |
| -4- Rm{William Robotham - Chief Engineer}/Ed{J. L. Edwards}7/R.14.7.37. The phenomenon of increasing depression with increasing power was brought up, but no reason other than resonance could be found. It was suggested by Ricardo that an improvement might be effected by making the exhaust valve close rather later, thus giving more time to clear out the exhaust gases. To compensate for the increased overlap, however, it would then be necessary to make the inlet opening somewhat later. It is thought by the Writer that this arrangement might be quite satisfactory when employing the following:- (1) A large exhaust valve would help, having a similar effect to closing the valve later. It still would have to be used in conjunction with a later closing however. (2) A large inlet valve would tend to compensate for the shortened inlet duration. In this way, it is thought that a compromise may be struck between large valves, and a valve timing to suit tick-over and slow running, and also keep exhaust silencer losses down to a minimum. From the point of view of noise, a gradual opening of the exhaust valve was suggested, in that instead of allowing the gasses to come out with a sudden bang, they would be more slowly released; this, however, has the disadvantage of increasing the exhaust valve temperature. III. Venturi Valve Seats. A considerable number of air flow tests have been carried out with various flairing and masking of the valves, and also with various shapes of valves and throats. Most of the work has been done on Diesel engine cylinders and heads, and a brief resume of results is as follows:- (1) Venturi Seats. The sketch shows the inlet port on a Diesel engine fitted with a Venturi valve seat. This engine gives a very good performance, but so far a direct comparison with and without venturi seats has not been done. 19/16" 1 7/8" | ||