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 development tests for nozzles, valve sizes, and side injection configurations.
| Identifier | ExFiles\Box 133\3\ scan0071 | |
| Date | 8th March 1939 | |
| -2- Nozzles. Lapped holes were not much better than plain holes, but an effect was observed if the holes were excessively rough due to poor drilling. Carbon deposit was also encountered, and after certain periods (no times stated) a power drop of some 5 MEP would be experienced. This could be completely recovered by cleaning out the holes. Volumetric Efficiency & Compression Pressure. The large size inlet valves (2.050") were found to give an increase of some 2% in volumetric efficiency and compression pressure over the smaller valves (1.950). Side Injection. A series of tests were carried out using a side injector of the inverted type and a special piston with the combustion space cut out of one side, the rest of the piston being about .050" from the cylinder head. The original arrangement gave a C.R. of 12.0 and starting was found to be very difficult. This was improved by raising the C.R. to 14.2, but the performance was very poor, the engine developing only 50.9 lbs/sq.in. at 1.305 lbs/BHP/hr. consumption with a very dirty exhaust. An examination of the fuel spray showed very poor atomisation, with an indefinite start and very bad dribbling, conditions which were not relieved by the use of a 25% higher rate cam. As development of the nozzle progressed, a power of 83.2 lbs/sq.in. was ultimately obtained with a fuel consumption of .557 lbs/BHP/hr. using a three hole nozzle arranged as a horizontal fan, with 45° between the holes. Each hole was .019" dia. x .055" long. A clear exhaust was experienced at all loads under 74 lbs/sq.in., a rather surprising feature in view of the high consumption. This may be due to late burning brought about by the air trapped between the piston and the head not being released until late in the stroke. | ||