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 the effects of fitting an air vessel to the supply pipe of a fuel pump.
| Identifier | ExFiles\Box 179b\3\ img100 | |
| Date | 1st February 1933 | |
| 210 The sum of the lag and injection period is given in Col.5 Table 3. Theoretically, delivery commences at the instant suction port closes and ceases the instant the spill port opens. This neglects compressibility of fuel oil and finite rate of opening of spill port. For normal injection with the R.R. pump this period is 19° (pump), see Appendix 1. The difference between the figs. in column 5 and 19° shows how long injection continues after the spill port opens. This is a minimum for hole No.1 (6.5°) and a maximum for holes 3 and 4 (8.75°). Exact determination of the end of injection is a matter of some difficulty and hence too great reliance must not be placed in this comparison. EFFECT OF AIR VESSEL ON THE SUPPLY PIPE. With the suction chamber hole opposite the supply pipe open, the effect of fitting an air vessel in the supply pipe near the pump on the delivery, pump lag and injection period speed curves, was investigated. Pressure pulses set up in the supply pipe by the action of the pump plunger may seriously interfere with the filling of the pump chamber particularly at certain critical speeds and the function of the air vessel is to damp down these pressure oscillations. The effect of the air vessel on delivery at maximum injection is shown in Fig.5. The form of the curve was practically unchanged but the quantity delivered per cycle was reduced by about 0.015 ccs at all speeds. A reduction in the spill was noticed which became more marked at the lower speeds. Fig.6. indicates the effect of the air vessel on the Discharge-Control position curve. At the higher injection quantities the air vessel reduces the delivery for a given control position but the curves cross at a static injection setting of approximately 10° and below this the effect of the air vessel is to increase the delivery for a given control position. The effect of the air vessel on the pump lag and injection period curves at normal injection is exhibited in Fig.7. At 1000 R.P.M. the lag is 1.5° greater with an air vessel than without one, but at 340 R.P.M. it is slightly less. The injection period at 1000 R.P.M. is 1.5° greater without an air vessel than with one but below 800 R.P.M. there is no appreciable effect. It is concluded from these tests that there is nothing to be gained by fitting an air vessel to the pump. | ||