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).
Test report detailing the investigation into fuel boiling within a carburetter and its effects on engine performance.
| Identifier | ExFiles\Box 179b\3\ img044 | |
| Date | 17th January 1931 | |
| -2- remained perfectly steady throughout. Further running, in the form of three tests of 5 minutes duration at 2500 R.P.M. with smaller throttle openings down to 230 BHP. was carried out with similar results, making a total of 35 minutes duration under ideal conditions, without the slightest trace of freezing of either diffusers or throttles. The results satisfied the A.I.D. and are conclusive as regards reproducing the trouble on the test bed. The fuel boiling which was next investigated is reported to be indicated by excessive flooding of the carburetter, following a richening of the mixture after a backfire, which is sufficient to stop the engine running, the flooding continuing after the engine stops. It would appear that if fuel boiling occurs, it would be indicated by progressive richening of the mixture as the water jacket temperature increased, as the lighter factions of the constituents of the fuel boiled off in turn, and increasing the consumption and richness of the mixture, by entering the air stream in a gaseous state, instead of being carburetted in the normal manner. In this case the fuel flow into the air stream would be the quantity of fuel supplied by the normal functioning, plus the amount of fuel boiled off. The maximum intensity of the fuel boiling would be shewn at the smallest throttle openings, by reason of the smaller quantity of fuel being used, and allowing the bulk of the floatchamber capacity to be in contact with the water heating for longer periods. In this respect it should be noted that when running at 485 BHP. with a fuel consumption of 254 pts/hr. the whole of the floatchamber capacity of 1.1 pts. is being changed every 15 seconds. To observe this effect the engine was run at a low power with a fuel consumption of 93 pts/hr. equivalent to a change of fuel in the floatchamber every 43 seconds. After the engine had settled down the water temperature was allowed to increase from 60° to 100° outlet in 10 minutes, and run at 100° for a further 10 minutes, during the whole test the fuel consumption did not vary from the original 93 pts/hr. and the power maintained throughout. These preceding tests were all carried out on Shell D.T.D.134 fuel, and it was thought that possibly the | ||