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).
Analysis of engine power drop tests investigating various fuels, injector nozzles, and the effects of fuel line leakage.
| Identifier | ExFiles\Box 179b\3\ img207 | |
| Date | 1st February 1933 | |
| -17- and at 95 mins. it suddenly decreased from 89 lbs/sq.in. to 82 lbs/sq.in. and remained more or less constant at this for the remainder of the test. The value of this test was destroyed by excessive leakage at the fuel line indicator valve. Diagrams taken before and after the power drop show no appreciable differences. The needle valve was discoloured as before. A test (3d) was now run using a new R.R-Bosch nozzle with ball race steel body and K.A.8 needle and the results are plotted in Figs. 11 and 12. The power was now fairly steady at 90 lbs/sq.in. and with no sign of a sudden power drop. The needle was only slightly discoloured. Hence, although the discolouration was somewhat less with Persian gas oil than with Anglo Persian airship oil, it does not appear probable that the discolouration of the needle valve in C.I.2 and not in C.I.1 is due to any change in the fuel oil. The difference in the initial boiling point of air ship and Persian Gas oil made no apparent difference to the power drop and hence the cause may not be vapourisation. As a last test to find the cause of the power drop it was thought that the addition of petrol to the fuel would render this much more marked if it were due to vapourisation of the more volatile fractions of the fuel. A test of 70 mins. duration (3e) was run using a fuel consisting of 10% petrol and 90% Airship Diesel oil and results are plotted in Fig.13. The power rose slightly from 92 lbs/sq.in. to 94 lbs/sq.in. and there was no sign of a power drop. There was slight discolouration of the injector needle. It was concluded from this test that with the improved cooling of the injector used in this series of tests the temperature of the injector was not sufficient to cause vapourisation of the fuel in the nozzle even with a volatile constituent added such as petrol. Hence, although vapourisation may have played a part in the sudden power drop with the original cooling system, any variations in power now observed must be wholly or mainly due to some other cause. The only tests in this series which showed a power drop were 3b and 3c and in which leakage occurred in the fuel line. When the injection system was in order no power drop occurred although the magnitude of the power was not the same in all the tests. | ||