MODERN MARINE ENGINES

Evening Post, Volume CVII, Issue 109, 9 May 1924, Page 11

MODERN MARINE ENGINES

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the; new jr^cnsannEnQ-snEZER TYEE. . LOSSUOH:, 20th; MaiclK Birring- tire p«Kfc week^. the Fan-field1 Sluptraildiog and Engineering Company, Govan, Glasgpw,. have, been running-shop trials of. the first of. tbxs four IfairfieidSulzer engines wHdt tha firm are constructing iqr the Union. Steam. Ship Company's liner Aarangi, ..now on the stocks la their yard. The vessel^ which will be launched, in Jane and completed about the end o£ this year, is a quad-ruple-screw ship, and,as'the fonr sixcylinder engines will develop a total of about 16,000 Lli-p., giving- a speed of 18 knots on service between sTew Zealand and Vancouver, the installation, of propelling machinery win be- the most powerful yet manufactured for one vessel., and will mark a, distinct forward step in the development of marine engineering. ; , The trials on the tost bed consisted of a continuous run for 72. Lours, at designed service power, fallowed immediately thereafter with a run of 12 hours at 10 per' cent, overload.^ Throughout the whole of this time the engine ran perfectly and without any adjustment, and at the termination the bearings were cool and in perfect condition. A trial of about three hours was subsequently run at 150 revolutions (equivalent io 975 feet per minute piston speed), and developing 3800 b.h.p., or approximately 20 per cent, overload and overspeed, and. at this speed the engine ran quite as well as. at the designed- revolutions. While the consumption at the 20 per cent, overload is shown-to be higher than at the designed power this is not .a true criterion of the performance, as the consumption would havo been reduced by adjustment of the cams and fuel pumps to, suit - the . higher revolutions. These being set for the designed .conditions itwas deemed inadvisable to alter them for this short trial. ■' " ,

Shipowners and other friends of. the company-who witnessed tho trial running of the engine included Sir A. M. Kennedy (chairroajixof the Fairfield Company), Koar-Admiral Sir D. E. R. Brownrigg, Bt., C.B. (director), Mr. R. Traill (director and engineering-manager), and-Mr. A. J. Hendin (director and shipbuilding manager), Mr. A. C. X Henderson and Mr.- A. J. P. HendersoD (both of the Anchor Line), Miv G. J. Innes (of Messrs. P. Henderson and Co.), Mr. J. Austin (of . the Cunard Steamship Company), Mr. H. A. Wilson (of the Anglo-American ' Oil Company), Oommander F. J. Cleary (of the United States Navy), and Mt.'W. Isherwood. THE ENGINE DESCRIBED'; Each engine; has six cylinders 27$ in. in diameter, and with a stroke of 29in. They are of the two-stroke eyde : Sriteer type, modified in some respects to suit the requirements of a fast passenger liner. Considerations of propeller 'efficiency rendered necessary a relatively | high, rate of revolution, and on service, developing 16,000: i.h.p., the speed of the shafts will be 127 r.p.m. There has been incorporated in^the design' specially stiffened framing, particularly., in the columns and bedplates. The bearing surfaces have been increased so as to reduce the pressures on these parts, and, while these increases have added to the weight of the completed engine, tho wis-' doni of doing so has been fully demonstrated hi the shop trials, as the freedom from ,vibration, even. when.running at extreme overload conditions, has been most marked. Great importance has also been attached to securing a rigid attachment to the ship's structure, and in consequence the soleplate is arranged with a flat base for direct attachment to the tank top instead of being secured to gir-. ders built on the tank top, as is usual in Continental designs—which hitherto have been more or less followed by en-gine-builders in this country. The double bottom of the ship in way of the main propelling machinery has been made spe r cially deep, and particular attention has been paid to the design of the girder work in the double bottom tank so as to distribute the load and the stresses' arising from the-, propelling machinery. For supplying injection air each engine has two compressors driven by an extension of the main > crank-shaft' and with cranks arranged at 180 degrees to each other. For scavenging the cylinders with low-pressure air three motordriven turbo-blowers will be fitted, each being capable of supplying the scavenging air necessary for two engines. One of these blowers was arranged to work in conjunction. with the engine on the test bed, and special arrangements were made when testing the engine to test at the^same time'the blower, delivering.so per cent, of its output to the engine and 50 per cent, to the atmosphere: The well-known type of rotary valves for controlling the air passing through the upper row of scavenging ports has been superseded by groups of multiple disc valves fitted in the scavenging trunk, and these admit ah" through the control port as soon as the exhaust pressure in the cylinder falls below the pressure in the scavenging trunk. In the same . way these air valves ai'6 closed: as soon as tho compression pressure in the cylinders exceeds the scavenging air pressure, this pressure . in. the cylinders exceeds' the scavenging air pressure, this latter pres-. sure being.about 1.751b per square inch. This modified design of scavenger valves is a distinct improvement on the ro; tary valve, and it eliminates one more of the relatively few working parts associated .with the mechanism (so far as the Diesel aspect is concerned) of the Sulzer-type Diesel engine. Oil fuel is delivered to the cylinders by means of a six-plunger pump'situated at the after end- of the engine arid at the starting platform level. ,