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).
High-octane aviation fuels, anti-knock compounds, and their application in aircraft engines.
| Identifier | ExFiles\Box 150\1\ scan0208 | |
| Date | 29th September 1936 guessed | |
| - 2 - temperature for different specific fuel consumptions when using various octane number fuels (A.S.T.M.) in a 1930 Cyclone 600 H.P. engine and a 1935 Cyclone 800 H.P. engine. The latter curve, indicating the minimum specific consumption possible without either misfiring or a sharp rise in cylinder head temperature, illustrates a significant and important benefit obtainable with high octane fuels. The advantages of high compression ratio other than increase in air cycle efficiency may, therefore, logically include the possibility of operating at leaner air fuel mixtures. Suitable fuels permit of such leanness without excessive head temperatures. When engines are designed to cruise at best economy on a given fuel, serious limitations are encountered at full power take-off, during climbing and in emergency conditions. These limitations are overcome in practice either by providing a special fuel of higher octane number than required for cruising or by operating at rich mixtures when delivering full power. Neither is a satisfactory solution, the first because of obvious reasons necessitating dual tankage, fuel control and a personal factor in pilot conduct; the second for reasons of economy. With super octane fuels it would appear that full power take-off will be possible without full rich adjustment and coincidentally have cruising at mixtures approaching the misfiring point without approaching critical head temperatures. The experience of air lines and engine manufacturers has shown that, with present design and existing materials, a moderate concentration of Tetraethyl Lead is desirable in controlling and stabilizing combustion in high output engines and at the present time the best blended fuel would appear to be one of approximately 100 Army Octane Number containing 3 cc. of lead per gallon. Introduction to Main Subject Petroleum chemists the world over have for many years been seeking new materials suitable as high anti-knock fuels by themselves or as blending agents in the preparation of base stocks to which some anti-knock compound such as Tetraethyl Lead could be added in small quantities to give the desired high anti-knock value. Technical Iso-Octane is one such material already made commercially available. The petroleum industry has now succeeded in providing a new material to supplement technical Iso-Octane. This material is Isopropyl Ether. Contrary to the behavior of Ethyl Ether which is a violent knock inducer, Isopropyl Ether along with some other ethers has been found to be an exceptionally good anti-knock fuel. During the past eight years experimentation has progressed on this material and methods of manufacture studied until at this time it appears to be an important factor in the successful solution of the high anti-knock fuel problem. Full scale multi-cylinder engine tests, mentioned later, have demonstrated its remarkable anti-knock qualities and in physical characteristics it apparently meets the requirements of present day military and commercial aviation fuel specifications when blended with aviation gasoline in proportions to give 100 octane with 3 cc. of lead tetraethyl. | ||