ON THE TEST BED at the works of the builders is a set of turbines under construction for a cross-
THE principle of the steam turbines that drive the 80,000-
Reciprocating engines, however, have their limitations. Efforts have been made from time to time to dispense with the backward and forward movement of heavy masses of metal and so permit of greater speed. Rotary steam engines of various types have been invented, but in most of them the action is partly reciprocating, and none of them has survived in a practical form.
The first rotary steam engine was invented by Hero of Alexandria about the year A.D. 50. The machine worked on the principle of “reaction” which was to be re-
In Giovanni Branca’s engine (1629) a jet of steam impinged on vanes attached to the rim of a horizontal wheel that was “blown” round in much the same manner as a windmill. Branca’s engine may be regarded as the first impulse turbine. For practical purposes, however, the first turbines were worked by water. This type, similar to the familiar water-
It is to the genius of the Hon. Sir Charles A. Parsons that we owe the development of the modern steam turbine. In 1884 Sir Charles Parsons patented a reaction turbine consisting of a drum or rotor fitted with a series of rows of blades, inclined at angles of about 45 degrees. Between each row of blades are others inclined in the opposite direction and attached to the inside of the casing surrounding the rotor. The first fixed row of blades serves as a series of nozzles from which the steam issues and impinges on the first row of moving blades, driving them forward and so turning the drum.
ORIGINATOR OF THE MODERN TURBINE, the Hon. Sir Charles A. Parsons was born on June 13, 1854. In 1884 he patented a reaction turbine consisting of a bladed rotor revolving in a casing fitted with fixed blades. He lived to see steam turbines propelling most great modern ships all over the world and died on February 11, 1931.
In the Parsons turbine, however, this impulse action is not the main driving force. The rotor blades are so shaped that they discharge the steam with considerable velocity, so that the rotor is driven round mainly by reaction. It is on this impulse-
Two rows of blades, fixed and moving, would have been insufficient to use fully the energy of the steam. For this reason the Parsons turbine employs a number of blade rows in series, allowing for the reasonable expansive working of the steam. The original Parsons turbine of 1884 is now exhibited in the Science Museum at South Kensington. It was not used for marine purposes but, running at 18,000 revolutions a minute, it was used for driving a dynamo -
Two features of this turbine are important. The steam entered the casing at the centre and passed outwards through the fixed and moving blades. The object was to avoid end-
First Used on Land
In most modern turbines the difficulty is overcome by using “dummy pistons”, or large circular disks on which the steam presses to counteract the side pressure of steam on the moving blades. The second important point is that the 1884 machine is of the parallel-
The mechanical advantages of the steam turbine for ship propulsion were realized from the outset. Turbines are lighter, perfectly balanced, yield greater speeds and occupy less space, power for power, than reciprocating engines. For naval use they conform to the early ideal of having the engine below the water-
The first turbines were employed for generating electric light on land, and they exhausted direct into the atmosphere without the use of a condenser. By 1892 turbines had begun to be used with condensers and proved, in certain conditions, to be more economical in coal consumption than reciprocating engines.
Among the early troubles that were experienced by the first turbine engineers was that relative to propellers. Once again models of ships and screws were employed to solve the problems of propulsion, just as they assisted Smith and Ericsson in their propeller experiments described in the chapter “The Development of the Screw Propeller”.
Propeller efficiency and hull resistance were determined by testing a series of models, from 2 to 6 feet long. These were towed in a tank by falling weights or were self-
THE ORIGINAL TURBINE ENGINE of the steamship Turbinia, built in 1894 at Wallsend-
From these experiments sprang the famous Turbinia. Her engines and the after part of her hull are now preserved in the Science Museum, South Kensington. The Marine Steam Turbine Company, Ltd, was formed for the purpose of building this experimental vessel, and she was built in 1894 in a small yard at Wallsend-
The turbine drove one propeller shaft and was of the radial-
This turbine also is preserved in the Science Museum and comprises a series of fixed and rotating disks, each fitted with rings of blades. Steam, flowing outwards from the axis of the rotor, passed alternately between the fixed and moving blades. Then, flowing inwards behind a moving disk, it again passed outwards between the next pair of disks, with their alternate rings of fixed and moving blades. Steam was supplied to the inner portions of the disks through holes near the rotor shaft. For reversing purposes the rim of the last disk was provided with blades driven by jets of steam.
Despite careful experiments, however, the Turbinia’s first efforts were disappointing. She was designed to break all speed records then existing, but her greatest speed, even with a number of propellers on her single shaft, was only 19¾ knots. Investigations were then made to determine the cause of the failure.
Nine Propellers on Three Shafts
In the shafting between the turbine and the propeller there was introduced a specially made torsion-
The fault therefore lay with the propellers. The screw shaft ran at between 1,600 and 2,000 revolutions a minute, and it was observed that at this speed the propeller formed cavities in the water and so absorbed a large amount of the engine’s power uselessly. With wide-
of that required. In 1896 the original turbine was removed and replaced by three parallel-
These turbines were of approximately equal power. The high-
Steam was generated at a pressure of 210 lb by a Yarrow type water-
Each turbine comprises a light steel rotor or drum fitted with blades resembling closely-
Steam enters the high-
The engines of the Turbinia developed about 2,000 shaft horse-
In June 1897 the Royal Navy celebrated the Diamond Jubilee of Queen Victoria by the holding of a review at Spithead. Before the eyes of Britain’s fleets, the Turbinia made an unofficial and spectacular display -
The sensational performance of the Turbinia drew the attention of the Admiralty to the possibilities of the steam turbine for naval use, especially for high-
Four propeller shafts were used in either vessel and there were separate sets of engines, on either side of the vessel, each comprising a high-
HMS Viper, with a displacement of 370 tons, was the first of the two vessels to undergo trials, and her mean speed on a one-
The application of turbines to the propulsion of merchant vessels was not long in following. In 1901 a Clyde passenger steamer of 650 tons, the King Edward, was built by W. Denny and Brothers, of Dumbarton, and engined by Parsons.
The King Edward had three propeller shafts. The centre shaft was driven by a high-
Early Turbine Successes
A fine model representing a three-
During trials held in June 1901 the King Edward attained an average speed of 20½ knots. The estimated indicated horse-
The vessel gave a better performance than could have been expected had she been fitted with triple-
The success of these turbine steamers led to the building of others for the cross-
THE FIRST GEARED STEAM TURBINE for marine use was made in 1897 by Parsons Marine Steam Turbine Co, Ltd, and installed in a twin-
With the two earlier destroyers it had been found that turbines were more efficient than reciprocating engines at high speeds; but at low speeds the position was reversed. This was before the days of reduction gearing for turbines. To enable HMS Velox to adopt a comparatively low cruising speed economically, she was fitted with two sets of 150 horse-
For cruising at speeds of about 13 knots or less, the main steam supply passed to the reciprocating engines and was then exhausted into the turbines. For higher speeds the steam was taken direct to the turbines and the triple-
In 1903 another turbine-
In 1906 was built the famous battleship HMS Dreadnought. She was designed for a greater speed than any other battleship. For the first time a great battleship was equipped with Parsons steam turbines and those in HMS Dreadnought, driving four screws without the use of gearing, gave her a speed of over 21 knots. This ship, with her ten 12-
In the Mercantile Marine also the use of turbines progressed from small river steamers and cross-
Combination of Two Systems
Even in these large ships the turbines were coupled direct to the propeller shafts; no gearing was used. The problem set by the Turbinia still persisted -
The Otaki, built by W. Denny and Brothers for the New Zealand Shipping Co. in 1908, was the first ship in which this system was used. This ship had three propellers; the two wing shafts were driven by reciprocating engines, both exhausting into the turbine driving the centre shaft. For manoeuvring and going astern, the reciprocating engines only were employed. A special automatic steam valve was used to cut out the turbine and permit the wing engines to exhaust directly into the condensers. This system was subsequently adopted in many large Atlantic vessels, including the White Star liners Olympic and Titanic of 1911.
The second method of transmitting turbine power to the propeller shaft is that now generally adopted -
Merchant steamers, including passenger ships, were later fitted with geared turbines and reduction gearing was used for the first time in the British Navy in the twin-
The modern geared turbine is a wonderfully efficient and compact power unit. It often comprises high-
A 20,000 horse-
AFTER PORTION of the machinery installed in the Turbinia. The radial-
You can read more on “Steam Turbine Construction” in Wonders of World Engineering