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 analysis of Isopropyl Ether as a blending agent in aviation fuels, discussing its properties, economy, and availability.
| Identifier | ExFiles\Box 150\1\ scan0212 | |
| Date | 29th September 1936 guessed | |
| - 6 - (a) Blended in commercial aviation gasolines, a fuel of 100 Army octane is possible with 40% of Isopropyl Ether without exceeding 3 cc. of lead tetraethyl. (b) The blending value of Isopropyl Ether is slightly superior to the blending value of technical Iso-Octane in unleaded blends and also superior for any fixed amount of lead tetraethyl in the corresponding blends. (c) When blended with 74-75 octane gasoline, and without exceeding 3 cc. of lead per gallon, an octane number of approximately 101-102 is the maximum possible when using technical Iso-Octane as a blending agent, whereas Isopropyl Ether will give at least 105 in concentrations of about 65% or over. (d) The amount of lead tetraethyl necessary to meet a given octane number is less for Isopropyl Ether than for technical Iso-Octane in blends containing the same percentage concentrations. Economy The question of cruising range possible with various fuels naturally raises the question of the limitation of Isopropyl ether blends due to its 5-6% lower heat of combustion on a volume basis. Offhand it would appear that the range would be reduced correspondingly for a given tank capacity. This is not necessarily the case. It has already been pointed out that increasing compression ratio permits of operating at leaner air fuel mixtures. It has also been shown that the maximum Army octane number of a blend containing not over 3 cc. of lead per gallon is about four points higher for the Isopropyl ether than for the best technical Iso-octane blend. Data are lacking on actual performance but from the best figures available it would appear that compression ratio could be increased - or possibly supercharger boost increased - to permit of operating at about a 10% lower specific fuel consumption, thus compensating for the lower heating value. There are indications also, that for equal 100 Army octane rating fuels, the Isopropyl ether blend will permit of a leaner mixture without exceeding critical head temperature - and providing compression ratio is high enough to permit of very lean mixtures - again compensating for its inherently lower heating value. Needless to state this discussion applies only to comparisons with 100% hydrocarbon fuels of 100 Army Octane Number. The Isopropyl ether blends of 100 Army Octane Numbers are far superior to all fuels of lower Octane Number. Availability Of particular interest when proposing a new and different fuel is the question of potential supplies of raw materials as related to potential demand. The total U.S. consumption for all grades of aviation fuels was 63,000,000 gallons for 1934 and is estimated as 88,500,000 gallons for 1936. | ||