3S 6 INTERNAL-COMBUSTION ENGINES 



round the ports in the cylinder, which are uncovered by the piston barrels when furthest 

 apart. The cylinder and annular exhaust box are immersed in a water-tank. 



Messrs. Mather & Platt, Ltd., Manchester, have recently made " Duplex " gas 

 engines up to 500 B.H.P. on a modified Koerting-Clerk type 1 with no valve-gear, and 

 the type seems to be suitable for gas engines of very large power. The whole cylinder- 

 unit, consisting of a pair of equal side-by-side cylinders, presents extremely simple forms 

 of single-walled castings particularly suitable for use in gas engines. It is made up of 

 two U-tube castings placed end to end, the inlet and exhaust ports being at the joints, 

 while flanges on the cylinders some distance from the joint retain between them the inlet 

 and exhaust boxes. The cylinder-unit is placed in a water-tank. Each piston uncovers 

 the cylinder port at both ends of its stroke, as in the Koerting-Clerk type. The two 

 cranks are set nearly parallel, one having a slight angular lead so that the exhaust port 

 is uncovered before the inlet port. When both ports are uncovered the charge of air 

 and gas from the pump displaces the exhaust gases before it, the gases in the inlet 

 cylinder passing through the connecting passage to the exhaust cylinder and thence 

 through the exhaust port. 



The cheapest fuel for gas engines is the gas given off from iron blast furnaces and from 

 coke-ovens, formerly a waste product. In Germany and America blast furnaces and rolling 

 mills for the production of steel plates and rolled sections are usually associated in the same 

 or neighbouring works; hence the extensive use of large gas engines. In Great Britain 

 the same conditions do not hold to the same extent, but the continual endeavour to re- 

 duce costs of production will compel the rearrangement of iron and steel works, so that large 

 gas engines may profitably utilise the tremendous power now running to waste. 2 



Oil Engines. The most rapid progress is being made in the application of the Diesel 

 engine 3 for stationary and marine power-plants. Fishing-boats, barges, yachts, and large 

 ocean-going ships are now running successfully with Diesel oil engines. The large 

 marine oil engines have usually 4, 6, or 8 vertical cylinders, working either on the two- 

 stroke or four-stroke cycle. The pistons are usually air-cooled; starting and reversing 

 is effected by a supply of compressed air at a pressure of 250-400 Ibs. per sq. in. The 

 " Selandia," built by Burmeister & Wain, Copenhagen, and the " Jutlandia," built by 

 Barclay, Curie & Co., Ltd., Glasgow, are sister ships of 5,000 tonnage, 7,500 tons carry- 

 ing capacity, with a service speed of 12 knots. The propelling machinery consists of 

 twin screws, each shaft being driven by an eight-cylinder single-acting four-stroke cycle 

 engine. Each cylinder is 20.87 m - bore, 28.74 in. stroke. The indicated horse power 

 is 2,500 at a speed of 140 revolutions per min. The Werkspoor Works, Amsterdam; 

 the Augsburg-Niirnberg Works; Sulzer Bros., Winterthur, and many other firms in Ger- 

 many, Italy, and England are also building marine oil engines of large power. 



For marine propulsion, the Diesel oil engine offers considerable advantages as com- 

 pared with steam turbines and boilers. The boiler space is saved, and the oil fuel- tanks 

 can be arranged in positions that cannot be used for cargo, whereas coal-bunkers occupy 

 space that might otherwise be available for cargo. A separate set of steam turbines is 

 required for reversing, while for naval purposes in which the maximum power of the 

 machinery is only required for short periods, a third set of "cruising" turbines is 

 usually installed, on account of the low economy of steam turbines running at less than 

 full power. One set of Diesel engines can perform all three functions; the fuel-injection 

 valve-gear being arranged to admit the oil spray during a longer or shorter period of 

 the piston's stroke, giving full or low power as required, while the valve-gear for revers- 

 ing is an integral part of the engine, just as with piston steam engines. 



Fuel for Oil Engines. The growth in the demand for oil fuel, from the volatile petrol to 

 the heavy residue left after distillation of the purer grades from the crude petroleum, due 

 to the motor-car industry and the development of the Diesel engine, has been more rapid 

 than the increase of the supplies; the effect being that at present the prices of all grades ol 

 oil fuel are nearly double what they stood at three years ago. The future of the mternal- 

 combustion-engine industry in all its branches depends largely on an adequate supply of 

 cheap fuel. The high prices have stimulated the production of oil fuel from hitherto neg- 

 lected sources. Creosote oil, a by-product in the manufacture of coke, is being used in 



1 See E. B. xi, 499. 2 See E. B. xi, 497-8. 3 See E. B. xx, 43 



