Again, owing to the small latent heat of evaporation of naphtha, which is only -4- that of water, the loss of heat to the cooling water will he very much less when condensing naphtha than with steam ; but then less heat is given to the liquid naphtha to convert it into vapor to begin with ; so that in the case of naphtha smaller quantities of heat are being dealt with, and larger portions converted into work by greater pressure during expansion. Hence, for a given power. machinery of much less weight is required with naphtha than with steam. With due precautions to avoid explosions of inflammable vapor, naphtha is found in practice to afford greater convenience of working, owing to the rapidity with which it evaporates, as well as to its oily nature, enabling it to act as lubricant to the engine-cylinder.
The Altmann-Kiippermann Petroleum-Mahn—Fig. 11 shows the petroleum-engine of Messrs. Altmann & Kfippermann. of Berlin. The cylinder is vertical and single-acting, con taining a long piston, packed with five rings, to prevent the leakage of the products of com bustion, and surrounded with a water-jacket. At its upper part it has two horns, which carry the bearings of the crank shaft. at one end of which are a fiy-wheel and driving-pulley, and at the other end a bevel wheel, which drives the governor and the valve gear. The valves are all of the mushroom type.
There is a vapor inlet valve, an air inlet-valve, and an exhaust - valve, each worked by a sepa rate cam on a small hor izon tal shaft driven from the lower end of the gov ernor-spindle.
The store of oil for the day's working is kept in the vessel shown on the left. A pipe leads from the vessel to small pump, which makes one stroke for every two revolutions of the engine. The length
of stroke can be varied.
The general control of the engine is effected, however, by the govern or, which entirely cuts off the supply of oil when the speed is too high.
To this end a small valve, placed in front of the pump, and kept down by a strong spring, is lifted by a cam to allow the oil to pass to the pump during normal working, But if the speed is too high, the governor shifts the Cain sidewise, so that its raised position no longer comes under the roller at the end of the lever which controls the valve, and consequently the latter can not open. The oil which passes the pump enters a small copper retort, kept red-hot by means of a lamp, and is there con verted into vapor, which is drawn into the cylinder when the vapor-valve is lifted by the cam.
This is the same can that operates the oil-control valve. The ignition of the charge is effected in the usual way by means of an incandescent tube, heated in the first instance by the same lamp as the retort. This lamp has no chimney, and burns ordinary paraffin-oil with a blue flame. like a Bunsen gas-jet. The oil is forced through the nozzle by air-pressure erected by a small pump. and is vaporized by coming into contact with a hot metal spreader. The ex haust-valve is not visible in the engraving, as it is at the back of the cylinder. It is worked by a cam. and can be readily removed for cleaning. The consumption of oil per horse-power per hour is said to be from -1S5 to -23S gallon in the smaller sizes of one or two horse power, and -132 to •159 gallon in the larger sizes.