This article was first published in 2010.
Charles Parsons, later the Hon. Sir C.A. Parsons, C.B., K.C.B., O.M., (1854 - 1931), ranks high amongst the many British engineers and inventors of the Victorian and Edwardian eras. His greatest achievement was developing the steam turbine, first exhibited to huge effect in the extraordinary Turbinia.
Developing the Turbine
Parsons’ first, and very comprehensive, patent for a compound reaction steam turbine was filed in 1884. This pioneer machine, which was of ‘parallel flow’ design, was a success and in the next few years important problems regarding lubrication, blade efficiency and control were solved, together with the application of the turbine to dynamos (turbo-generators) for generating electricity.
Production of turbogenerators was then commenced both for land and shipboard use and, from the evidence available, it seems likely that it was during this period that Parsons first seriously considered the direct application of this type of turbine to marine propulsion.
However, in 1889 he left the firm for which he had been working - Clarke, Chapman & Co - and in doing so lost the patent rights to the ‘parallel flow’ turbine. A complex legal battle for their recovery followed, but for five years he was denied the opportunity to develop any form of ‘parallel flow’ machine so that the efforts of his own new company had to be concentrated on ‘radial flow’ turbines.
After great development efforts these proved basically less efficient than the ‘parallel flow’ machines, but some of the results gained were later to prove of use in other fields. Despite the deficiencies of the ‘radial flow’ machines Parsons was, by late 1893, commencing design work for the purpose of actually applying turbine power to ship propulsion.
In January 1894 he took the principle part in forming the Marine Steam Turbine Co. (Heaton) which was given the exclusive licence rights for major patents dealing with turbine propulsion for ships. It was also at this time that he recovered for reasonable costs his original patents for the ‘parallel flow’ design.
The stage was thus set for the entry of the Turbinia, for Parsons had already effectively “solved a problem which for a hundred years and more has exercised and baffled the ingenuity of inventors. Many persons have endeavoured to employ the velocity of steam for the purpose of causing rotary motion without the intervention of any reciprocating apparatus. But no one before Mr. Parsons ever succeeded in producing a steam turbine of practical utility”.
Turbinia is born
In order to apply the turbine successfully to marine propulsion, two particular requirements needed to be met. Firstly, the production of speed of the turbine and, secondly, the use of a condensing system which would provide water re-circulation to the boilers and assist turbine efficiency.
The second matter was already partly dealt with since Parsons had prepared a condensing design as early as 1888 and a condensing ‘radial flow’ land turbine was successfully tested in 1892; but the first requirement, the matching of propellers to turbine speed, later proved a more serious problem than anticipated.
The aim of the Marine Steam Turbine Co. was to thoroughly test the application of Mr. Parson’s well-known steam turbine to the propulsion of vessels “and to demonstrate the advantages of the turbine for this purpose”.
The decision was thus taken to construct an experimental high speed craft of around 100 feet length to be powered by a 1,000 horsepower turbine. The resulting vessel became the Turbinia or, initially, simply the Experimental Launch.
However, before the vessel could be constructed, extensive model tests were required to determine the hull characteristics and power requirements.
The necessary experiments were commenced by Parsons himself on ponds at Ryton (then his home) and Heaton (the turbine works).
In accordance with contemporary high-speed practice, the hull was to be of high length/beam ratio (approx. 1:10) with wedge-shaped bows lacking flare and rounded body sections to decrease wetted area drag. The original design calculations of late 1893 in fact included an extreme hull of 100 ft x 8 ft x 5 ft 7½ ins. to a draught of 3 ft, but the beam later chosen was 9 ft, probably to gain greater displacement.
In the form eventually adopted, there was a pronounced flattened run to reduce the tendency of the aft end to squat at high speeds. The distinctive turbine works seems almost to have been produced on aesthetic grounds alone, Parsons later indicating that a ‘built down’ stern would have been as adequate in practice, if not better.
A 2 foot long model, driven by twisted rubber cords, produced the first significant results and this was followed by a similar one of 6 feet length with a geared drive producing 8,000 r.p.m.; the torque (power applied) was ascertained by use of a miniature air dynamometer and hull resistance was determined by towing tests.
Thus propeller efficiency, propeller slip and horsepower requirements were all calculated from apparently simple, but really very accurate, experimental methods which owed much to the pioneer work of W. Froude. Later Admiralty tests, and modern computer based simulations, have shown that Parsons model experiments gave extremely accurate results.
Although all design and drafting work was carried out by Parsons and his own staff, the company did not have the facilities for constructing the hull. This was contracted out nearby to the firm of Brown and Hood of Wallsend who, although not shipbuilders, were experienced sheet metalworkers, an appropriate skill since the deck and hull plating were only one sixteenth and three sixteenths of an inch thick, respectively.
By February 1894 the vessel was under construction and plans were in hand for fitting a compound ‘radial flow’ turbine, developing some 1,500 h.p. at 2,000 r.p.m., with direct drive to a single two-bladed propeller. Although the ‘parallel flow’ patents had by now been recovered, experience with high power units of this type was limited, so the ‘radial flow’ turbine was installed.
The vessel was apparently launched without publicity on 2nd August, 1894, less than a year after the preliminary designs were started, a remarkable achievement for a team headed by a man with no previous naval architecture experience.
Trials of the Turbinia began on the 14th November 1894 but results were disappointing, propeller slip was nearly 50% and speeds were low. A four-bladed propeller was substituted and eventually seven different arrangements were tried but all with similar results. A cleverly designed shaft dynamometer was built to ascertain that the turbine’s power was sufficient; this indicated 960 h.p.,- near enough the 1,000 h.p. theoretically required.
Another nine sets of propellers were then tested, but all showed relatively Iow efficiency. The best performance was obtained with triple screws of 20 inch, 22 inch and 22 inch diameter, at one pitch ratios, but slip was still 37.5%, at 1,750 r.p.m., giving a speed of only 19¾ knots.
Other men might have given up at this apparent failure to achieve high speeds, but Parsons persevered. By early 1895 he suspected that the problem lay with the formation of “vacuous cavities” behind the fast moving propeller blades, and the practical implications of this cavitation effect were revealed publicly by Thornycroft and Barnaby in March of that year.
As the turbine’s speed could not be reduced, the answer in the case of the Turbinia seemed to be in the use of multiple propellers with increased blade area. The decision was thus taken to replace the single shaft with three shafts and, since the patents were now recovered, to use the more efficient ‘parallel flow’ turbines with one compound stage (high, medium and low) to each shaft.
At the same time, extensive experiments were carried out on model propellers using the world’s first propeller testing tanks which were devised by Parsons himself. With this equipment it was possible to photograph cavitation taking place and make quantitative measurements of its effects.
By February 1896, the three ‘parallel flow’ turbines were installed, minor modifications to air pumps etc. were carried out and three propellers, 18 inches in diameter and of one pitch ratio, were fitted on each shaft (making nine in all). Several further sets of propellers were tried, the best results coming from a set of nine, each of 18 inch diameter and 24 inch pitch.
Overall the division of the turbines, which applied one-third of the total power to each shaft, gave greatly increased propeller efficiency and speed.
The results were outstanding, though not unexpected by Parsons, and by December an average speed of 29.6 knots had been reached over the measured mile whilst, with further improved propellers, 32.76 knots was achieved by April of the following year. Eventually, maximum speeds of over 34 knots were recorded.
The Turbinia was thus the fastest vessel in the world.
Scientifically and practically, the possibilities of the turbine for high-speed marine propulsion had now been conclusively demonstrated though, despite some early developments, progress was to slow down for a short time before its widespread adoption in naval and mercantile circles. But that is another story.
The Turbinia’s Subsequent Career
In April 1897 the Turbinia was put through a comprehensive series of independent trials by Professor J.A. Ewing F.R.S. of Cambridge and, in maritime and scientific circles, these did much to validate Parsons work and present it appropriately.
However, the greatest popular notice was caused by Turbinia’s appearance at Queen Victoria’s Diamond Jubilee Naval Review at Spithead in June of the same year. Here she appeared, a greyhound racing past the assorted reciprocating powered steam ships – all in a pageant designed to show how advanced the old navy vessels were! It was an exceptionally successful publicity exercise, much of the credit belonging to her Captain, Christopher J. Leyland, who was a director and leading campaigner for the Marine Steam Turbine Company.
Following the Spithead Review, further trials of the Turbinia, often including engineer representatives of the Admiralty, were carried out; but Parsons attention increasingly centred on the two torpedo boat destroyers (Viper and Cobra) which were to be fitted with turbines. Also, experiments were in hand with a small reduction geared turbine fitted in a 22 foot launch. Indeed, since the future at sea eventually proved to lie with the geared, rather than the direct-driven, turbine, this little launch can in retrospect be seen to rank in importance with Turbinia herself.
At this time a new company was formed, the Parsons Marine Steam Turbine Co. Limited, which was given sole licence for the building of marine steam turbines. A new factory was built at Wallsend and retained till its closure the title, “Turbinia Works”.
The Turbinia remained virtually unchanged, her purpose now largely being that of a high-speed demonstration vessel; a function which she performed for example on the Seine at the great Paris Exhibition of 1900. In fact the return passage from this particular exhibition proved to be one of the most hazardous parts of her career, since first she almost collided with a sailing ship and later was forced to run for shelter in heavy North Sea weather.
In 1902 the last change was made in her basic form, single propellers of 28 inch diameter and pitch replacing the triple screws on each shaft. In 1907 she was steamed for what proved to be the last time in order to accompany the liner R.M.S. Mauretania on her trial trip, but alas the air pump, always temperamental, broke down and the Turbinia could not proceed all the way. It seems a final irony that a piece of reciprocating steam machinery should rob the vessel, which had proved the efficiency of direct rotation by steam, of a final glory.