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).
Page from a publication discussing secondary reference fuels, octane number definition, and anti-knock quality of gasoline.
| Identifier | ExFiles\Box 27a\4\ Scan067 | |
| Date | 1st November 1931 | |
| 88 REFINER AND NATURAL GASOLINE MANUFACTURER NOVEMBER, 1931 reau of Standards will stand ready to make referee tests on samples of the same material submitted by purchasers in case any question arises as to purity. Also, as a result of the efforts of the sub-committee group, octane is now in the process of manufacture, and will be for sale by the chemical firm of Rohm and Haas, Philadelphia. The same arrangements are being made for the certification of the purity of this material by the Bureau of Standards, as is the case with the heptane. The price on the heptane will be $25 a gallon. That of the octane has not as yet been determined, but is expected to be appreciably lower. SECONDARY REFERENCE FUELS The necessarily high cost of producing the pure hydrocarbons, normal heptane and iso-octane, precludes their use as reference fuels in routine laboratory testing. It is, therefore, necessary for testing laboratories to provide themselves with suitable secondary reference fuels which have been carefully calibrated in terms of the two primary reference fuels, normal heptane and iso-octane. As is stated in footnote 4 of Appendix II, two such secondary reference fuels, one of 50 octane number and the other of 68, have been made available to interested laboratories by the Standard Oil Company of New Jersey. Work is now in progress by this company to extend the range of the scale covered by blends of these two fuels, and to make the calibration curves furnished with them correspond in all details to the “tentative recommended practice for making knock tests,” as given in Appendix II. OCTANE NUMBER DEFINED AND ILLUSTRATED The octane number of any gasoline is the percentage of octane by volume in the mixture of octane and heptane that just matches the gasoline in anti-knock quality, as determined in the apparatus described and by the procedure specified. Thus, if under these conditions the gasoline is matched by a mixture of 60 parts octane and 40 parts heptane, its octane number is 60. If it is a better gasoline, so that it is just matched by an 80 octane-20 heptane mixture, its octane number is 80. Variations in engine conditions have such a large effect upon knock that the relative anti-knock qualities of fuels may vary with changes in such factors as temperature, spark advance, throttle setting, and mixture ratio. In some instances these variations may be large. Consequently, the octane numbers of gasolines are determined under definite conditions. These conditions as tentatively settled on, are given in detail in the outline of procedure, Appendix II. It should not fail to be said, however, that in spite of all these precautions, there appear to be some instances in which the octane number of gasoline does not give an altogether dependable measure of how it will knock in every engine. The chief reason for this appears to be that automobile engines do not always operate under the maximum conditions just enumerated. These limitations, and the desire to evaluate them properly and to remove them wherever possible, constitute one of the important reasons for the continued existence of this sub-committee. [Chart Text] SUMMARY 23rd SEMI-ANNUAL MOTOR GASOLINE SURVEY RANGE PREMIUM-PRICE GASOLINES, MARCH, 1931, 60 TO 95 AVERAGE AT 77 RANGE COMPETITIVE-PRICE GASOLINES, MAR. 1931, 40 TO 78 AVERAGE AT 62.5 APPROXIMATE VALUES FOR C. F.{Mr Friese} R.{Sir Henry Royce} VARIABLE-COMPRESSION ENGINE. OCTANE NUMBER CRIT. COMP. RATIO CRIT. COMP. PRESSURE B.M.E.P. AT 600 R.P.M. FIGURE 3 Chart of the Octane Number Scale of Anti-Knock Quality Showing also the following: 1, the approximate relationships to the octane number scale of critical compression ratio, critical compression pressure, and brake mean effective pressure for the “C. F.{Mr Friese} R.{Sir Henry Royce}” engine at 600 r.p.m.; 2, the octane number ranges of the motor gasolines sold over the country in March, 1931. Figure 3 is a chart of the octane number scale. At the left, graduated from 0 to 100, is the actual octane number scale. Scale 2 to the right of it shows for the “C. F.{Mr Friese} R.{Sir Henry Royce}” engine how the approximate compression ratio at which knock just begins relates to the octane number scale. Thus, a compression ratio of 4.0:1 in this engine corresponds to a gasoline of 67 octane number. In a similar manner, scale 3 shows for this same engine how the compression pressure for incipient knock relates to an octane number, and scale 4 gives similar information on brake mean effective pressure at 600 r.{Sir Henry Royce} p. m.{Mr Moon / Mr Moore} It is important to note that these scales of compression ratio, compression pressure, and brake mean effective pressure at which knock just begins, as related to octane numbers, are approximate only. They apply only to this particular engine under the defi- (Continued on page 112) | ||