The Possibilities of Creosote for Oil Engines
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Encouraging and Helpful Information in Report by Home Fuels Sub-committee of the Diesel Engine Users Association on Experiments with Blended and Doped • Creosote Fuels Used in Compression-ignition Engines
OPERATORS of vehicles powered by cil engines who are 4./considering the possibility of using creosote as fuel will find some helpful information on this subject in a report from the Home Fuels' Sub-committee of the Diesel Engine Users Association on "The Possibilities of Providing and Utilizing Home-produced Fuels for Diesel Engines." The address of the Association is 56, Victoria Street, London, S.W.1, and w,e understand that a limited number of copies of the report is available at 1Qs. 6d. each.
Investigations Were made with a Leyland lorry having an 8.598-litre oil engine, with a Lister 9 b.h.p. unit running' at 1,000 r.p.m., and with certain other machines. The fueli with which trials were carried out included high and low-temperature " creosote 'diesel fuels " used alone, doped. and blended, and these led to the formation of many important conclusions, some of which may be regarded as definitely encouraging.
Early in the report it is explained that the spontaneousignition temperature of coal oils is higher than that of petroleum-base fuels, with the' result that creosote fuels are harder to ignite and to burn in the cylinder than petroleum-base oil fuels. This ignition quality is expressed by the cetene number, and the higher this number the more suitable is the fuel. The average commercial oil fuel hats a cetene number of about 60.
Nature of Chemical Dopes Employed in Tests Ignition can be accelerated in certain cases by adding to creosote small quantities of dopes. Five such chemicals are named in the report—ethyl nitrate, amyl nitrate, amyl nitrite and two special preparations of the Gas Light and Coke and Low Temperatnre Carbonization concerns, respectively.
With regard to blending, the report states that any goodquality petroleum-base oil fuel w1th a cetene number above 57 is suitable.
Much importance attaches to the de-sludging of creosote partly because blending promotes sludge formation, and this characteristic has proved a serious obstacle to com mercial development. In addition to settling-tank and centrifuging methods, a process has been developed by the Low Temperature Carbonization company which represents an important advance.
For purposes of reference, particularly in the determination of cetene values, the committee used a reference blend comprising alpha-methyl naphthalene, of which the cetene number is zero, and Kogasin II, a Fischer-Trelpsch synthetic product, with a cetene number hetWeen 99 and 102.
One of the mot interesting and informative items in the report is a graph named "correlation curves of coal-tar oil diesel fuels " On it are plotted curves relating to a blend. of (a) high-temperature creosote with petroleum diesel fuel, (b) methyl naphthalene with Kogasin II, and (c) low-temperature creosote diesel oil with petroleum diesel fuel.
This graph indicates the relationship between the percentage of the blend and, on the one hand, the compression temperature required to produce ignition, and, on the other, the required engine compression ratio, the latter being qualified by engine temperatures ranging from 15 degrees C. to 45 degrees C. • • From this graph can be readily ascertained (1) the proportion of creosote which can be blended with oil fuel for' an engine of given compression ratib and temperature limits, and (2) the minimum compression ratio for a known blend.
Curve a shows that with 20 per cent, of creosote this blend requires a compression temperature of about 420 degrees C. and a compression ratio of 14 to 1 at '15 degrees C. A 50-50 mixture according to curve c will ignite at' 440 degrees C. given a compression ratio of 14.25 to 1 at 15 degrees C.
Engine temperatures, incidentally, are measured oy taking the mean between the water-jacket and air-intake readings. . • Corresponding figures for curve h are, 20 per cent. of lowgrade fuel, 355 degrees C. and 10.5 to 1 at 15 degrees C.; 50 per cent.. 415 degrees C. and 13.5 to I.
Raising engine temperature to 25 degrees C. instead of 1,5 degrees lowers the necessary compression ratios given above, thus : 14 to 1 becomes. 12.75 to 1; 14.25 to 1, 13 to 1; 10,5 to 1, 9.75 to 1; and 18.5 to 1, 12.25 to 1.
Regarding sped& road tests made with the Leyland, referred to earlier, the Committee summarizes the results of trials with 20 per cent, tet creosote and 80 per cent. Shell Dieseline as follows :—From cold, no start could be obtained ; after starting on pure oil fuel, the engine continued to run satisfactorily while and after a gradual changeover to the blend was made; after 20-minute stops, restarts were successfully made" on the -blend; satisfaction. was obtained in general running provided that the filter was cleaned " very frequently —due to " excessive sliniging."
Other road tests showed that with is._ 20 per cent, mixture of high-temperature creosote and SO per cent. petroleum " gas oil " (cetene number 70). with final de-sludging treatment of blend, the engine started up well from cold,' acceleration and pulling were " very good," no smoke was emitted, consumption appeared favourable and filter remained clean.
Under the heading "Availability of Creosote Diesel Fuel," the report states that members should communicate with the Mines Department for information concerning supplies.
• Conclusions Regarding High and Low-temperature Creosotes
The conclusions drawn by the committee, the report of which is signed by Mr. J. S. Tritton, M.Inst.C.E., M.I.Mech.E., Mem A.S.M.E., chairman, may be summarized thus : Existing road-transport engines do not readily utilize straight h.t. creosote fuel ; the addition of 4 per cent, of a certain dope is generally equivalent to adding 40 per cent, of petroleum oil fuel ; bench tests poiut to the possibility of using 50-50 ,mixtures containing lit: creosote, but qualifying restrictions would hardly permit the universal marketing, of such a blend ; road 'tests show that a 20 per cent, blend is satisfaCtory for running but not for starting from cold, also that a 20 per cent, blend with petroleum gas oil instead of petroleum diesel oil, treated after mixing, was satisfactory in most respects.
Straight Lt. fuel can be used for running on, but presents starting difficultieS; doped 1.t. fuel experiments showed that 3 per cent, gives improved results, but blending is 'quicker and cheaper ; starting difficulties occur with 50-50 blends with' petroleum diesel fuel, but are eliminated if petroleum gas oil, be used. According to the report 1.t. fuel treated by the Low Temperature Carbonization dc-sledging process is now being supplied regularly to the Petroleum Poolafor blending with commercial grades of petroleum diesel oil. ,Blends supplied to the public contaip 20-30 per cent.
Further conclusions state that the consequences of fudging can-be serious, but can be avoided by the abovenamed process ; that the quantity of h.t, tar oil available for making diesel fuel is about 5,000,000 gallons a year :• that practically an the raw material is now required, for hydrogenation, and that about 1,000,000 gallons `a. year of 1.t. crude is immediately available.
Xs appendices to the report are tables of road-transport oil-engine data, and of certain features of two creosote fuels.