TRANSACTIONS OF SECTION G. 761 



the conditions for ordinary work. In fact for any particular oil experience must 

 decide the degree of compression that gives best results as regards power and 

 efficiency consistent with economy and durability of engine. 



The author briefly noticed his investigation of the relation between the pressure 

 and temperature of the vapours from diiierent burning oils, intermediate oils, and 

 some heavier lubricating oils, in order to throw some light on the action in the 

 cylinder of the common oil-engine. At the same time he has tried to find out which 

 oils are best adapted for this use. His experiments prove that, notwithstanding the 

 complex and varied cliaracter of the diiierent oils examined, the law according to 

 which the pressure of petroleum vapour varies tvith its temperature is represented by 

 a perfectly regular curve for each oil. He compared these results with the figures 

 obtained from the different oils when used in the same engine during special tests 

 for the purpose. 



By far the simplest type of oil-engine is that in which the oil is injected 

 directly into compressed and heated air in a cartridge which at once acts as vaporiser 

 and combustion-chamber. Such an oil-engine is the invention of Mr. H. Akroyd 

 Stuart, of Bletchley, and is now being made by Messrs. Hornsby & Sons, 

 Grantham. A novel feature of this engine is that the ordinary gear for firing the 

 charge by heated tube, flame, or electric spark is dispensed with altogether, and 

 heavy intermediate oil is ignited and completely biu-ned when injected into the 

 compressed and heated air in the red-hot vaporiser or cartridge. This chamber is 

 heated up at start with a special oil-lamp supplied with air-blast by a small fan, as 

 shown in drawings. It was seen by the wall-diagrams that this engine is of the 

 simplest design. The working parts are i&'sfi and simple, and some details are 

 being improved by Messrs. Hornsby & Sons. The oil-cistern is fitted in the base 

 of the casting, exposed to ordinary atmospheric pressure, and the oil supply can 

 easily be replenished at any time during a run by sliding open the top cover and 

 pouring in the oil. 



Every charge of oil is forced, by means of a positive action oil-pump, through a 

 thin pipe and simple nozzle into the vaporiser at the proper moment for ignition, 

 just after the hot air has been compressed and the piston is on the return stroke. 

 The oil supply is regulated by a governor, whilst by using a large fly-wheel and 

 high speed, about 210 revolutions per minute, this engine runs very steadily. The 

 author tried a 6 horse-power engine during a run of about three hours, using oil 

 of specific gravity '854, and flashing point 220°r., and the consumption was less 

 than a pint per brake horse-power per hour. Even heavier oils might be tried, 

 the hot water from tlie water-jacket going to warm up the heavy oil and keep it 

 in a fluid state fit for use in winter. 



The action in the engine-cylinder is here very different from that in the Priest- 

 man, inasmuch as there is an excess of air in the cylinder, and this is compressed 

 before the oil is injected. Consequently, the combustion is rapid and will be com- 

 plete even when heavy oils of great heating power are used. However, since the 

 air is dry, and there is no condensation of oil, the cylinder requires independent 

 lubrication, as in the case of the gas-engine. 



A feeling of safety to tlie public naturally tends to the use of heavy oil, from 

 which the lighter constituents have been distilled. The author has found the loss 

 in weight of some heaA'y oils by prolonged heating at low temperatures, keeping 

 the oils exposed to the air and allowing free evaporation. Known weights of 

 oil were taken in shallow dishes, about three inches across top, and gently heated 

 on a sand-bath by a very small steady flame for three hours, the temperature of 

 the oil being kept constant. The proportions of volatile constituents present in the 

 samples are indicated. 



The terribly explosive character of the hydro-carbons driven off" at the ordinary 

 temperature renders the safe storage of petroleum imperative. Instead of the 

 present tank system, Mr. B. H. Thwaite has devised the safety oil-tank. It is 

 very much like a gas-tank, the cover-plate being kept in contact with the oil and 

 counterbalanced by weiglits to give only a slight pressure of one or two inches of 

 water on the surface of the oil. Tlie frame moves into an annular water seal 

 stand-pipe, to draw off any gas that collects. There is no necessity for the 



