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).
Supplement to a report on detonation, discussing the challenges of obtaining consistent H.U.C.R. values due to fuel deposits.
| Identifier | ExFiles\Box 58\2\ Scan017 | |
| Date | 1st March 1931 | |
| B.Tr{Capt. F. W. Turner - Finance} seen Ry. 86000 Supplement to A.M.L. Report No. 108A, March, 1931. Air Ministry Laboratory Imperial College of Science, S.W.7. Detonation, Spark Plug Position and Engine Speed. S U P P L E M E N T. Determinations of H.U.C.R. given in report no. 108a were made by the method described in an earlier publication (1), but to obtain consistent results it was necessary to maintain the combustion space and spark plugs in clean condition. The errors due to accumulated deposits are particularly serious when the fuels contain benzole or metallic dope in large proportion. Moreover, the H.U.C.R. values for a series of fuels may depend on the order of use, for example, starting with clean plugs and engine, the H.U.C.R. for a petrol-benzole mixture will be higher before a doped petrol has been used in the engine than afterwards. Similarly, the H.U.C.R. for a gum-free fuel will be higher before a gumming fuel has been used, than afterwards. Consequently, when fuels of dissimilar natures are compared consistent relative H.U.C.R. values cannot be obtained when the supply to the engine is repeatedly switched over from one to another. The deposits remaining on spark plugs after a doped fuel has been used are especially effective in reducing the H.U.C.R. subsequently obtained for a benzole mixture and careful cleaning does not destroy the effect entirely. The present practice is to set aside a pair of plugs for use with petrol ethyl fluid mixtures only and to clean them whenever the concentration of ethyl fluid in the fuel is altered greatly. A second pair of plugs is kept for use with undoped fuels only. Experiments with doped and undoped fuels are made in separate groups always beginning a group with a clean combustion space. The intention is to determine the H.U.C.R. for any particular fuel in the conditions produced by it in the combustion space and all experiments described recently have been made in this way. (1) King and Moss, Measurement of Detonation, "Engineering", Vol. 78, page 219, 1929. 55-2 | ||