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).
Engine development experiments concerning injectors, injection pumps, air swirl, and volumetric efficiency.
| Identifier | ExFiles\Box 133\3\ scan0065 | |
| Date | 6th March 1939 | |
| -5- Rm{William Robotham - Chief Engineer}/Ed.{J. L. Edwards}4/MH.{M. Huckerby}6.3.39. Comparison of Injectors - Cont'd.{John DeLooze - Company Secretary} Due to the form of the jet, which has little divergence, this type of nozzle is unsuited to no-swirl conditions, but gives a BMEP of 92.6 lbs/sq.in. when swirl is introduced. Injection Pump Experiments. The rate of injection on the Bosch cam was increased by 25% but little or no difference was made by employing this on the R.A.E. injector unless a lighter valve was used, when a fair improvement was noted. The injection pressure was increased slightly by using this cam, but pressures otherwise were more or less unchanged. The spill ports on the pump plunger were modified to provide a sudden pressure drop on opening the ports, but no particular improvement was observed and it is doubtful if any effect was felt at the injector. Tests also showed that at high injection pressures, the "anti-dribble" valve fitted to the Bosch pump has very little effect on power output, merely acting as a non-return valve, unless the displacement was increased very considerably above its original setting (.0035 cu.ins. to .0065 cu. ins.) Rotational Air Swirl. The best method of inducing swirl, as found during the previous 100 hours running, was by fitting masks to the inlet valve seats. This arrangement was found to be very susceptible to the mask dimensions, and slight manufacturing errors were quite sufficient to upset the running. It was accordingly decided that optimum conditions were obtained with a condition of no swirl. (N.B. It is considered with this head that quite possibly an organised swirl would be forced by the domed head in conjunction with the pointed top piston, this providing all the necessary turbulence for good combustion). Volumetric Efficiency. With high lift cams, and standard valves a volumetric efficiency of 84.2% was obtained at 2000 R.P.M. It was noted, however, that the valve timing setting for optimum volumetric efficiency did not necessarily give the highest power output, due presumably to alterations of air swirl brought about by the altered timing. | ||