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).
Technical memorandum comparing anti-chamber and direct injection compression ignition engines.
| Identifier | ExFiles\Box 133\3\ scan0036 | |
| Date | 27th February 1939 | |
| Rm.{William Robotham - Chief Engineer} 1128? Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner}1/G.27.2.39. COMPRESSION IGNITION ENGINES. Our visit to A.E.C. with Rm.{William Robotham - Chief Engineer} was very profitable, because it confirmed the information we have previously obtained from Leylands. A.E.C. who have been building anti-chamber cylinder heads for years have recently gone over to a direct injection, so they are able to compare both types. We can now analyse the short comings of the turbulence chamber cylinder head :- (1). It has about 10% higher fuel consumption. (2). There is heat loss to the water which is quite a problem to deal with on bus work. (3). It has to have heater plugs for starting. (4). Lubricating oil consumption is particularly bad. The development of this engine went through all 'Comet' stages and finished up with Mark lll. The Whirlpool chamber was not a success. With each of these different Comet chambers it was necessary to design and meticulously develop different swirl cavities in the piston top. On the same engine for instance if the stroke was altered the piston top had to be altered. This can not be done right away. It is a case of keep on trying, and the only evidence of correct swirl is by observing the carbon formation on the piston and the marks made by the spray holes. In the direct injection engine they have striven to get the nozzle as near as possible to the centre of the cylinder, it happens to be 5 m/m.{Mr Moon / Mr Moore} off centre. The desirable feature is to get good cooling for the nozzle. An improvement was made when the nozzle boss was altered from a casting to an inserted copper tube. There are four nozzle holes of about .010 to .016 dependent on the size of the engine. The limit of engine speed which is 2,000 revs. is controlled by the carboning up of the nozzle holes. When one of the nozzle holes becomes choked overheating occurs and the nozzle tip burns off. The swirl on this head is initiated by the mask on the inlet valve. | ||