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 indicator diagrams showing the effects of fuel injection timing and engine speed on combustion pressures.
| Identifier | ExFiles\Box 165\4\ img379 | |
| Date | 1st October 1936 guessed | |
| clear from the diagrams that the increase of pressure is very rapid, and that quite soon a vigorous flow must take place from the auxiliary chambers into the main chamber. also the forms of the diagrams are consistent with the view that the mixing and combustion of the fuel takes place in an orderly manner. That combustion in general in the main chamber takes place later than in the auxiliary chamber (It is emphasized in justice to the engine that the Full Load B.M.E.P. of 95.6 lb/sq. in. was obtained with a barometric pressure of only 28.1 inches.) Fig. 11. MAIN COMBUSTION CHAMBER (FIXED COMPRESSION RATIO 12.0:1) VERY LATE INJECTION LATE INJECTION NORMAL INJECTION EARLY INJECTION Fig. 12. MAIN COMBUSTION CHAMBER (FIXED COMPRESSION RATIO 12.0:1) 800 R.P.M. 1000 R.P.M. 1200 R.P.M. 1120 R.P.M. In view of the order of the pressures shown in Fig. 10, the influence of the injection setting is of special interest. Four tests were accordingly made at constant speed and B.M.E.P. but with different settings of the point of injection. Indicator diagrams taken from the main chamber, Fig. 11 show, as would be expected, that the maximum pressures increase steadily with advance of injection, in the usual manner. Measurement of the corresponding fuel consumptions gave from late to early 0.515 lb., 0.497 lb., 0.405 lb., 0.407 lb. per B.H.P. hour. There is thus no incentive, with this design, to advance the point of injection to improve the fuel consumption at the expense of increasing the maximum cylinder pressures. It further appeared of interest to examine the influence of speed on the pressures in the main chamber with the engine under nearly full load. Four tests were made at constant B.M.E.P. The Indicator diagrams given in Fig. 12 show no consistent variation in the maximum pressure with increase of speed, but in all cases the values are moderate. It was thus shown by the 'Farnboro' Indicator that the designers' claims were fulfilled and that the action of the gases during combustion was identical with that anticipated, the indicator diagrams providing valuable data unobtainable by other means. DOBBIE McINNES & CLYDE LTD., SOLE MAKERS MANUFACTURERS OF ENGINEERING AND NAVIGATIONAL INSTRUMENTS, 57 BOTHWELL STREET, GLASGOW. AND AT SOUTH SHIELDS, LIVERPOOL, & LONDON. | ||