BIG TURBINE ENGINE.

Dominion, Volume 2, Issue 579, 6 August 1909, Page 6

BIG TURBINE ENGINE.

TECHNICAL DETAILS. DEVELOPMENT FROM HERO'S DAYS. - At the present juncture, when the largo Parson's steam turbine—the biggest in New Zealand—is being installed in the city's electric lighting station, it may surprise many people who are accustomed to regard tbe turbine as an invention of recent times to loam that the origin of the turbine dates Lack to tho days .of Hero, of Alexandria, about 200 B.C. From ttio original invention of Hero, however, a long blank can be looked back on, no development occurring until- 1629,-, when Giovanne ■ Branca,-. ■an Italian architect, suggested the employment of a wheel with a number of pockets surrounding its periphery, into which a.'jet of steam-'was'directed-.' Nothing of value was done, however, until de Laval invented his first,turbine.in 188-2. This turbine was originally constructed for the direct driving of milk separators, and was much on the same principle as Hero's. The driving wheel was a.pipe, bent in the shape of the capital S, to which the steam was adniitted through a stuffing box in the centre, where the shaft was also fixed. The steam issued from the open ends, thus imparting to it a rotary motion. Advent of Parsons. In tho year 1884, electric lighting was rapidly coming to the front, and the demand a.roso for a good fast-running engine, which could bo coupled direct to a dynamo, to take the place'of the cumbrous system -of rope or belttdriving then generally in use: Many inventors • took -up tho 'development of■ tho high-speed ; engino, but: tho Hon. Charles A. Parsons was attracted' by the principle of Hero's"early machine, and, in considering tho problem, saw' the-possibility of the steam', turbine meeting the conditions created-by-the advent of the dynamo; In April, of 1884, Parsons filed his first application for steam turbines, and since then his- work has become monumental, and lie has - acquired a • world-wide reputation; His first machine had , a capacity of about 10 •horse-power, and was constructed for coup- , ling direct to. :a' dynamo specially designed to run at tho high speed of 18,000 revolutions per minute. Tho turbine t was made double-ended, and tho steam entered at.the centre, and passed towards both ends of the shaft'through rings of vanes secured alternately _. tp 'the. shaft and outer casing'. This machine was used for many years at Gateshead-on-Tyne, and can still' be seen standing close to the famous old reciprocate-' ing engines constructed by Watt, Stephenson,-, and others.' : The. first machines constructed by Parsons had many, defects, but these were, gradually overcome, and, in 1890, I turbines, were being made with a-capa-city of 120 horse-power. In 1894, further developments in the design of,his turbine were brought out by Parsons, -both in the direction of increasing the" running economy and decreasing-the- cost of manufacture. Between. 1894, and the. present Parsons has grappled with the problems of large turbines, Both for.marine and electrical work, and two large units of close-on a capacity of 7000 h.p.'each-have been recently constructed at Parsons'/Works at.Heaton,,near New.castle-OH-Tyne, f or. i!he Ultimo power-station of the Sydney tramways. Some idea of the size , of these . units ■ may be , "•obtained "■ when it isstated that tho steam oshaust pipe of each ■ machine is six :feet in diameter. •' '

Machine at Lighting Station. The machine at present being installed in the local, lighting-- , station/' oonsiste' of 'a cylindrical' case' with.'rings-of inwardly-pro-jecting vanes, within which revolves a concentric shaft carrying rings of outwardlyprojecting vanes. The: rings , of vanes on the case almost; touch the shaft, while the rings of vanes on r the revolving shaft lie between those on the case, and nearly touch- the same. Instead of the steam, entering at the centre of the machine, as in the early type of turbine constructed by Parsons, it enters at one endand passes through tne, blading in one direction only. The eteam on entering the turbine first passes' through a ring of fixed guide vanes, and is projected, in a rotational direction upon the succeeding ring of moving-vanes, imparting,to them-a rotational force. The steam is'then thrown back upon the succeeding fixed ring of guide vanes, and the reaction upon :the' next ring of moving varies increases • the rotational force. Thcsamo process takes place at each of the successive rings of fixed and moving vanes, whicli increase in diameter and.size towards the exhaust end of the machine! To balance the end thrust imparted to the shaft by the steam operating from one end, grooved pistons or ■ dummy.- blades are used, which rotate within corresponding. .Beatings.- The supply of stoam to the turbine is controlled by a sensitive governor so as to maintain a constant, speed of-1600'revolutions per minute at all loads, and an independent emergency governor is also provided. The. alternator, which lias a capacity of 1500 kilowatts, is coupled direct to the turbine, and the armature of the exciter f or supplying current to the fields of .the alternator is secured to of the 'rotor'shaft. As the turbine and the alternator connected to:it are' dosigned to run absolutely free from vibration, no holding-down bolts.are required to secure the bed-plate, to the.massive concrete foun'datioh." "■ ■••'■■■■• : - ■ ■ . ■

'■ High economy in the running of a steam turbine is contingent on a, good vacuum being obtainable, and with the view of securing the' latter, Messrs..Parsons' supply,- ..besides the ordinary surface condenser, an. arrangemeut 'known as a'vacuum augmentor, which is also an invention of the Hon. C. A. Parsons. The air .pump is of the vertical single-acting type, and is driven by a highspeed engine manufactured by Messrs. Belhs and Marconi. The pump for supplying the circulating water for the condenser, is or, the centrifugal type,, having suction and discharge branches 12 inches in diameter, and is capable of delivering "2000 gallons of water per minute, against a.total head of. 48 feet.-The auxiliary, plant at installed in the lighting station at Mercer Street includes a Clarke Chapman '-'Wooder. ■son" patent feed pump, capable of delivering 6000 gallons of water per hour, against, a pressure of 1601b. per square inch. Erection well Under Way. > ....;.-■. ; For some time past the foundations for the new-machine, at the. lighting station have been ready, and a large amount of machinery has come to hand. A good deal 'of the heavier preliminary' been done under the direction of Mr. P. M'Coll.: Yea--' terday morning.Mr.. J. P.; Yorston, one of the Parsons Company's turbine experts who arrived from England via Australia on 'Wednesday to superintend the erection of the turbine, took charge of the "works, and will stand by until the maohin'e is in. full running, order, Certain pipes have still to .come tonahd, but in , the meantime there is ample machinery in the lighting station to keep .the .expert..and the engineers busily . employed. It' is probable that the end of two months "will 6ee" the new; machine'' in full working order. . . ■ . . Turbine construction is now being undertaken by practically all the leading engine manufacturing firms of Great Britain, including the Westinghouse Company' and Messrs. Willine and Robinson. So' far, the Parsons' Company has installed..,something, like 30 big* machines in various parts of ' AustraUa. The New Zealand Shipping Company's eteamerOtaki, which is at present on .the New Zealand coast, is' fitted with turbines, which receive the exhaust steam from the ordinary reciprocating engines. This exhaust .steam tiirbino, it is stated, is being largely installed ,in the collieries in England. The Parsons Company is also, manufacturing large blowers'for mining purposes after; tJie principle adopted in the steam turbine;