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).
Cooperative fuel research, discussing test apparatus, octane numbers of motor gasoline, and cooperative testing procedures.
| Identifier | ExFiles\Box 27a\4\ Scan068 | |
| Date | 1st November 1931 | |
| 112 REFINER AND NATURAL GASOLINE MANUFACTURER NOVEMBER, 1931 Cooperative Fuel Research Apparatus (Continued from page 86) nite conditions of its operation which were: full load; 600 r.p.m.; 212° F.{Mr Friese} jacket temperature; full throttle; mixture ratio and spark set for maximum power. Even under these conditions, the values may vary somewhat from time to time as is common with engines, particularly at the higher compression ratios, depending apparently upon changes in conditions not included among those specified, such, for instance, as amount of carbon in the combustion chamber. But, to the approximate degree in which these data apply, this engine just begins to knock on an average regular gasoline (62.5 octane number) at a compression ratio of 3.85:1; whereas conventional automobile engines, when clean, operate without knock on such a gasoline at compression ratios higher than 3.85:1 by amounts varying from 0.5 to 1.5 ratios. These differences are due to differences in the construction of the engines and in the conditions under which they operate. OCTANE NUMBER OF MOTOR GASOLINE Presented also on the chart, Figure 3, is a summary in terms of octane number of the results of the Twenty-third Semi-annual Motor Gasoline Survey of the U. S. Bureau of Mines, Part III.3 Included in this survey were 312 individual samples from 19 cities, collected in March, 1931. Of these samples 207 were of competitive-price gasolines, and 105 premium-price gasolines. The measurements of anti-knock quality in terms of octane number as given were made by the Bureau of Standards using the “C. F.{Mr Friese} R.{Sir Henry Royce}” apparatus and method which is described in this report. As the chart shows, competitive-price gasolines cover the range 40 to 78 octane number, with the average of all at 62.5. Premium-price gasolines cover the range 60 to 89 octane number, with the average of all at 77. (One single isolated sample of premium-price gasoline which came at 50 octane number has been omitted from the summary as just given). These results not only represent the first generally available survey of the anti-knock qualities of the gasolines available over the country, but they are also the first comprehensive results to be expressed in terms that have the same meaning to everyone. TEST PROCEDURE The “tentative recommended practice for making knock tests,” which forms Appendix II, was drawn up by the sub-committee as representing their best combined knowledge based upon the present state of the art. With regard to the matter of procedure, it should be said, however, that no organized or comprehensive experimentation has yet been done directly on method. The apparatus in its present form has not been available long enough to permit it. Such information as was available for the preparation of the outline of procedure was, therefore, that which was based upon the individual experiences of members of the sub-committee, and that which was gathered incidentally in the various programs of investigation carried out during the development of the apparatus and during the experimentation upon the matter of reference fuels. It is, therefore, to be expected that some revisions in the matter of method of test will need to be made as more experience is obtained with the present equipment, and as knowledge of the knock-testing art increases. COOPERATIVE TESTS Using the apparatus as developed, which is described above and in more detail in Appendix I, and following the tentative procedure outlined in Appendix II, the last program of cooperative tests was carried out during August on a series of eight fuels. These fuels were made up in such a way that the composition of each was known to those who prepared them, but not to any member of the sub-committee. All results of the tests were reported in octane numbers, but ratings were made in two ways: 1, directly against mixtures of normal heptane and iso-octane; and, 2, against secondary reference fuels which had first been rated by comparison with normal heptane and iso-octane. The secondary reference fuels used by all laboratories were the same, and consisted of mixtures of the standard reference fuels “A” and “B” as supplied by the Standard Oil Development Company (see footnote 4, Appendix II), and of mixtures of standard reference fuel “B” and benzene. Although unknown to the members of the sub-committee, these same basic fuels (plus tetra ethyl lead in one instance) were used for making up the fuels to be rated. This gave an opportunity to test out the apparatus and procedure, first, for consistency of the results obtained by different laboratories when making ratings directly against normal heptane and iso-octane; and, second, for the “true” error of tests when fuels of the same constitution are matched against each other. A summary of the results, based upon analyses of individual laboratory reports, as made by H.{Arthur M. Hanbury - Head Complaints} K.{Mr Kilner} Cummings and D.{John DeLooze - Company Secretary} B. Brooks of the Bureau of Standards, is given in Table 1. For the reason that, as it developed following the tests, an error had occurred in mixing one of the fuels, “B-3,” so that the different batches of it were not uniform, the results on this sample have been omitted from the tabulation. The summarized results presented in Table 1 show that when measurements were made directly against heptane and octane, the average deviations from the mean in octane numbers for the different fuels varied from 1.4 octane numbers to 0.35 octane number. The mean of all these average deviations was 0.8 octane number. In a similar manner, when measurements | ||