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).
Article from 'The Autocar' magazine discussing and illustrating various designs of engine silencers.
| Identifier | ExFiles\Box 152\3\ scan0016 | |
| Date | 13th July 1912 | |
| 74 THE AUTOCAR, July 13th, 1912. Silencers. The Sunbeam silencer (fig. 19) is likewise open to a similar objection. There are two parallel pipes, after passing through the first of which the gases emerge into the shell and are then passed through the other and thence into the atmosphere. Strictly speaking, the expansion chamber should come first, as in this case it is conceivable that the gases are warmed up again after being once cooled. This, of course, is of little importance, provided their velocity be uniform at this point. Fig. 22.—The Napier silencer with multi-tube sound-wave trap in the exit pipe. Fig. 20 illustrates the Dennis arrangement, which is similar to the Cadillac, except that, instead of annular spaces between the concentric chambers, there are perforations for the gases to pass through. They become progressively cooler, but the expansion chambers increase in volume instead of vice versâ. Fig. 23.—The Daimler silencer. In the Lanchester, Napier, and Daimler silencers the cooling of the gases is very well looked after. In the first (fig. 21), after leaving the first expansion chamber, the exhaust is passed along a long annular space immediately inside the outer walls of the shell. A single set of perforations is used in the inlet, and an annular gap to the second chamber, from which a straight pipe proceeds. The arrangement of the Napier (fig. 22) is similar, except that there are four sets of perforations. At the exit orifice a sound-wave trap is installed, and consists of a considerable number of small tubes, keyed together like a small section of a honeycomb radiator. The effect of these is similar to that of the fan-shaped tail-pipe shown in fig. 2. In the Daimler device, the design of which is obvious from fig. 23, we have practically two silencers in tandem, with an expansion chamber between them. The cooling is progressive, and the silencer as a silencer is certainly effective. Fig. 24 shows a very interesting and ingenious design which is known as the Dunlop ejector silencer. The principle is unusual. A portion of the exhaust gases is directed to the main expansion chamber, the other portions being taken down a straight stepped tube placed immediately opposite the inlet. Three deflecting cones are fixed in the first chamber and three in the second, into which a portion of the gases in the central tube can make their escape. The rest of the gases in the latter pass right down to a conical nozzle, where they are claimed to have an injector action upon the gas in the second expansion chamber, in the egress of which it accordingly assists. A similar action takes place at the step of the central tube. High-speed gas entering the second chamber without passing through the first exercises an injector influence upon that which is already in the first and helps to draw it past the cones. Fig. 24.—The Dunlop “ejector” silencer. Fig. 25 illustrates a suggested form of silencer embodying the straight pipe principle with the disadvantage of impractical length partially removed. To get the best effect the helical pipe would need to have a gradually decreasing pitch, and might be divided into a number of sections of progressively smaller diameter. It would not, however, be easy or cheap to manufacture this type of silencer, and the suggestion is introduced simply because such an arrangement forms probably one of the best methods of cooling the exhaust gases with the minimum of resistance. W. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} ASTON. Fig. 25.—A suggested form of silencer embodying the straight pipe principle. A Toll Dispute at Bursledon Bridge (Faded and partially illegible text of a court report follows) | ||