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).
4-stroke vs 2-stroke engine development, and methods for testing nozzle spray and delivery rates.
| Identifier | ExFiles\Box 179b\3\ img141 | |
| Date | 6th February 1933 guessed | |
| -3- They have nearly completed their investigation programme on the 4 cycle engine, and hence done a little work on the 2-stroke. They are of the opinion that the 2 cycle is the only possible scheme for the C.I. aero engine. They are not enthusiastic about the 4-stroke and have no intention of doing any full scale work on it, however, building a new single unit and also intend to make a full scale engine on the 2 stroke scheme. Packards are still working on their engine but at present are not producing any aero engines. They had a very clever unit for showing the behaviour of spray nozzles under actual working conditions. Same cyl. as first mentioned scheme - non turbulent head - but the valves replaced by thick glass plates (Fig.3.) The pump drive gear was made to give one injection only when put into gear and the air was admitted by ports at the cyl. base, and arrangements were made for boosting. The air space between the glass was under air press. to 300 lbs/sq.in. to help to equalise the press. on the windows. A camera was set up and the illumination was from the discharge of condensers. By altering the phasing of the condenser discharge an instantaneous picture could be taken at any part of the cycle - and the resulting picture was in silhouette form. The complete cycle can be obtained. They get the results under the actual conditions of temperature and pressure. They say this has been very valuable in the development of nozzles. They then test out on the actual engine. Testing Rate of Delivery of Nozzles. A nozzle is set up in front of a rotating disc in which is cut a slot 2° wide. The phase of this disc can be adjusted in relation to the pump delivery. The injection is caught in a sort of unspillable ink well. Inside this is a coarse gauze packed with metal wool to prevent splashing out. The amount collected - which is weighed - can be determined for different phases of the delivery. A curve of delivery rate can then be obtained. (Fig.4). Visual Observations of Spray from Nozzles. The nozzle is fitted up in a box and illuminated by an oscilloscope which can be altered in phase. A French type of oscilloscope is used which is more brilliant than the one we use, and photographs can be taken. The whole operation can be seen and it can be noted if dribbling occurs. | ||