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 pump spill curves and lag-speed curves under various conditions.
| Identifier | ExFiles\Box 179b\3\ img098 | |
| Date | 1st February 1933 | |
| -8- The spill curves also show an increase at the highest and lowest speeds. The tendency is most marked for all 6 holes open and hole No.1. Discharge-control position curves are given on Figs. 3, 6, 11, 15 corresponding to 6 holes unplugged, No.1, 3, 2 and 2 holes respectively. A comparison of these curves will show that they change but little under the various conditions. PUMP LAG. Pump lag-speed curves are shown in Figs. 4, 7, 9, 16 and 18. These all show the same characteristic of increase in pump lag with decrease in pump speed but the magnitude of the lag is affected very considerably by the position and number of suction chamber holes open, as will be seen from Col.3 of Table 3. As regards number of holes, at 1000 R.P.M., normal injection (.235 ccs/cycle), it will be noticed that with 6 holes unplugged the lag is negative (-14º). This means that the delivery began at the nozzle 14º (pump) before the suction ports were closed. With 2 holes open it was +1 and with only one hole it averaged about +3.0. These figures suggest that a negative lag will be obtained if more than 2 holes are left unplugged. This would result in a long injection period, a falling off in sharpness of the jet and excessive after burning in the engine. At 336 R.P.M. all the lags are positive but decrease as the number of holes open increases. The variation in lag (16º) with speed with all holes open is excessive for the speed range tested (336-1000 R.P.M.). It is reduced to 4.5º with 2 holes and with one hole is about 3.0º. This is also shown in Table 3 column 7. So far as pump lag is concerned, these tests show that the best characteristic is given by a single suction chamber hole. There is little to choose between holes 1, 2, 3 & 4. | ||