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).
Technical paper discussing combustion roughness in side-valve engines, focusing on detonation, pressure rise, and flame front characteristics.
| Identifier | ExFiles\Box 134\2\ scan0005 | |
| Date | 19th March 1935 | |
| 4005 1129 E/PSN.1/MN.19.3.35. To. [REDACTED] Copy to Mr. [REDACTED] Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer} COMBUSTION ROUGHNESS. A great deal of work has been done in America in recent years on the investigation of the characteristics of side valve combustion chambers. Much of this work has been directed towards evaluating the effect of the various factors which influence detonation and smoothness of combustion, with the result that a great deal of information is now available which can be applied to the analysis of the characteristics of any combustion chamber. Possibly one of the most striking developments has been that of the none compact combustion chamber for side valve engines, with long flame travel giving smooth combustion and reasonable freedom from detonation. Smoothness of combustion depends in a given engine chiefly on the rate of pressure rise measured in lbs/sq.inch per degree of crank angle, and to a smaller extent on the acceleration of the rate of pressure rise at the commencement of combustion. This latter effect might be likened to that of the toe on a cam, in that the commencement of the pressure rise should be gradual so as to ease the load on to the piston. Once combustion has started the rate of pressure rise depends on the rate at which the mixture can be burnt. This in turn, depends on two main factors:- flame velocity and the area of the flame front. It can be assumed, with a fair degree of accuracy that the flame front spreads out from the sparking plug in a spherical manner, thus, curves can be drawn for any combustion chamber showing the fractional volume enclosed by the flame front plotted against flame travel. In general it can be said that the greater the rate of increase of volume enclosed by the flame front with flame travel, the higher will be the rate of pressure rise. This assumes the same flame velocity for all combustion chambers, but in general the flame velocity will tend to be greater in those combustion chambers which have a high rate of increase of volume with flame travel. So that the effect of flame velocity will be to exaggerate further the differences in rates of pressure rise, which might be deduced from the combustion chamber volume curves. It should be appreciated that deductions made from these curves must be of a general nature, as so many other factors have some influence on the rate of pressure rise, but nevertheless, it should be | ||