Page:EB1922 - Volume 31.djvu/553

Rh

4-stroke cycle engine instead of twice as much as would be realized in an ideal case.

A second type of 2-stroke Diesel engine, specially developed by Sulzer Bros, of Winterthur, is valveless excepting for the fuel in- jection valve and air starting valve. In this type fresh air, at slight pressure, enters through ports on one side of the lower part of the

FIG. 9.

cylinder at the same time that the burnt gases are escaping through ports on the other side, substantially as in the small two-stroke Day-type petrol engine, but without crank-chamber compression, as described later (see fig. 13). The fuel consumption of the 4- stroke cycle Diesel is roundly 0-4 Ib. per B.H.P. hour, and of the 2-stroke of either type about 0-45 Ib. per B.H.P. hour.

Land Installation of Diesel Engines. Steady progress was made between 1910 and 1921, and at the end of 1920 upwards of 100 plants existed in the United Kingdom of capacity ranging from 50 to 6,000 B.H.P., and aggregating more than 50,000 B.H.P. Outside England more than twenty important installations had by 1921 been erected, or extended, aggregating fully 25,000 B.H.P.; these are spread over the world, being found in Egypt, India, Ceylon, Burma, Malay States, Hong-Kong, S. Africa, Australia and N. and S. America. The principal makers in Great Britain are Mirrlees, Bickerton, & Day; Willans & Rob- inson; Hick, Hargreaves & Co.; The Brit. Westinghouse Co.; Swan, Hunter & Wigham Richardson; and Thornycroft.

Noteworthy installations are (i) that of the Charing Cross & City Electricity Supply Co., Ltd., London, which includes ten Sulzer Diesel engines aggregating 6,000 B.H.P. Of these, four

are of 500 B.H.P. and four of 600 B.H.P. 3-cylinder engines, all running at 150 revs, per minute: the remaining two are 4-cylinder 800 B.H.P. engines running at 150 revs, per minute; this installa- tion was completed in 1912. (2) At the Southend-on-Sea Elec- tricity Works there is a total of 3,900 B.H.P. supplied by two high-speed 6-cylinder Koerting Diesel engines of 450 B.H.P. each, running at 450 revs, per minute, and four 750 B.H.P. 6-cylinder " M.A.N." Diesels running at the same speed; these engines commenced running in 1920. (3) At Letchworth, Herts, the Electricity Supply Station contains six Diesel engines aggregating 1,900 B.H.P.; the first of these commenced work in 1910 and the sixth in 1916. (4) The great majority of Diesel engines are of the inverted vertical type; an interesting exception is that of the plant at Kingston-on-Thames Electric Power Station where are installed one 400 B.H.P. 4-cylinder 4-stroke M.A.N. horizontal Diesel engine running at 190 revs, per minute, and one 500 B.H.P. 2-cylinder, 2-stroke M.A.N. horizontal Diesel running at 165 revs, per minute; these engines commenced work in 1913. Of large installations outside England may be mentioned that of the Hong-Kong Electric Co. with an aggregate of 3,060 B.H.P. supplied by seven Sulzer Diesel engines; the first of these, two 3-cylinder engines each of 300 B.H.P., started work in 1908, and the last two of 4-cylinder 540 B.H.P. each in 1914. An external view of a 500 B.H.P. 4-cylinder, 4-stroke standard Diesel engine is shown in fig. 10.

FIG. 10.

Marine Diesel Engines. Marine Diesel engines differ in no essential respect from the land type. The majority of Diesel- engined vessels existing at the end of 1920 were fitted with 4- stroke cycle crosshead type engines largely on account of the known reliability of the 4-stroke engine in land installations. Two-stroke Diesel engines were at first made with cast-steel cylinder covers which not infrequently failed by cracking; this difficulty has been entirely overcome by making the cylinder covers of a suitable grade of cast iron, and the single-acting 2- stroke engine will probably become the preferred type.

For the very large engines required by war-ships the double- acting 2-stroke design is most suitable, and several had already been built in 1921 though there was not yet an instance of one fitted in a vessel; the cooling problem had not yet been quite satisfactorily solved. The 2-stroke engine possesses the advan- tages of reduced weight, reduced space occupied, greater sim- plicity in reversing gear, and lower first cost as compared with the 4-stroke type. Up to the end of 1920 a maximum of 1,800 H.P. had been attained in a single-acting, and 2,750 H.P. in a double-acting 2-stroke Diesel cylinder.

The first ocean-going passenger ship propelled by Diesel engines was the East Asiatic Co.'s i2-knot boat " Selandia," carrying a dead- weight cargo of about 7,400 tons, Copenhagen to Bangkok. There were twin screws each driven at 140 revs.