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).
Comparative analysis of engine power, consumption, and combustion chamber design for various engines.
| Identifier | ExFiles\Box 179b\3\ img169 | |
| Date | 1st February 1933 | |
| -3- He/H4.9/KLT.2.33. curve is remarkably flat in the range tested. The lubricating oil consumption was 0.022 lb/BHP/Hr. Typical power curves and consumption loops for a Daimler-Benz 6 cylinder C.I. lorry engine 4.07" bore, 6.50" stroke, are shown in Fig.5. The combustion chamber design of this engine is similar in principle to that of the aero engine described above. The bore and stroke are, however, both less for the lorry engine, and the speed range is wider and different. The best consumption is 0.441 lbs/BHP/Hr. at 1100 r.p.m. and is therefore considerably worse than the consumption of the aero engine at 1750 r.p.m. (0.42 lb/BHP/Hr) at maximum output. It has been frequently stated that the poor performance of the Benz lorry engine is due to the heat losses occurring at the small holes in the vaporiser, which is probably correct, and hence that this type of combustion chamber must necessarily be unsuited for aero work. The curves of Fig.4, however, show the fallacy of this argument. By constructing a larger cylinder which is not required to work over such a wide speed range (an aero engine is virtually a constant speed engine) it has evidently been found possible to retain the essential working principle and reduce these losses to a very great extent. If the Benz engine can be thus improved, it is possible (and even probable) that the proposed R.R. 2 stroke engine (5" x 6.5") running at 1400 r.p.m. may show a considerable improvement in consumption over the A.E.C. - Ricardo engine (4.3" x 5.5") which employs the same form of combustion chamber and works over a speed range of 400 r.p.m. to 2600 r.p.m. The consumption loop of the A.E.C. engine at 1500 r.p.m. is given in Fig.6 and plotted on the same diagram is the estimated consumption of the proposed 2 stroke engine at 1400 r.p.m. with 5 lbs. boost, from which it is seen that the estimated consumption is very modest. On the basis of the Daimler-Benz engine, the consumption should be ultimately much better than this. | ||