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).
Direct injection spark ignition engine performance, nozzle development, and comparison with carburation.
| Identifier | ExFiles\Box 179b\3\ img142 | |
| Date | 6th February 1933 | |
| -4- These schemes seem very useful for nozzle development - and quite simple. Direct Injection Spark Ignition. A very neat engine of 5.6 X 7 with four valves was used. The valves were inclined and the spray nozzle was in the side of the cyl. head, spraying directly at the inlet valves as this gave good mixing. (Fig.5). A Stromberg downdraught carb. was used between the engine and the blower, which could be either used as a carburetter or simply as throttles for the air for comparative purposes. The spray nozzle holder was the same as used in the C.I. engine. A 6 hole sprayer was used. The pump was the same Krupp type. The engine had 7/1 comp. ratio and was boosted to 3" Hg. Standard service fuel employed with 87 octane value. This engine gives 204 lbs/sq.in. B.M.E.P. - 1.6. 209 lbs. actual with 5 lbs. subtracted for the blower power which is separately driven. 2000 R.P.M. They have not been a higher speed as the balance of the engine above 2000 is not good and it tries to leave the bedplate. Con. .5 lbs/BHP/Hr. They are now getting down to .45 lbs. con. The injection control is linked with the throttle but they do not need much throttling of the air over the upper range - i.e. good economy. It is found that to get good tick over the air throttles must be close up to the valve ports. Big advantage in M.E.P. found by using from 120º to 140º valve overlap. Scavenging effect but only effective when using boost. This cannot be used with ordinary carburation due to blowing out charge and giving heavy consumptions. These curves (Fig.6) show the effect of overlap and injection compared with carburation. Injection pressure is 500 lbs/sq.in. and the period of injection is 40º and starts immediately the exhaust valve closes. It is found advantageous to inject fuel early, as if delayed the turbulent effect is lost. Turbulence soon appears to die out. | ||