Steam turbine

“ They can be operated with steam at atmospheric or low pressure, thus taking the exhaust from other engines. The greatest economy of operation for the turbine alone will be obtained by operating with high pressure, superheated steam and with a vacuum of 28 inches. In large units the economy of operation of steam turbines is equal to that of the best type of reciprocating engines. In order to develop the highest economy turbines are operated at speeds from about 3,600 to 10,000 r.p.m. ”

“ The economy of space and of fuel offered by the steam turbine is of great value in the power plants of ships, and this form of prime mover has been installed on modern high-speed passenger liners and also on high-speed war vessels. While in certain respects the turbine is ideal for such service, there are two handicaps which must be overcome. In the first place, the most efficient speed for the turbine is considerably higher than the efficient speed of the propeller and some means must be provided for stepping down the speed. ”

“ While most engineers still regarded the steam turbine as a task of the future, it had become a present-day problem that attracted the attention of the entire world of technics by its success. It remained for electrotechnics, with its rapidly running machinery to create a large field for the practical application of this new power engine. The by far greatest number of all steam-turbines in use to-day serves to drive dynamos.” [223] The turbine has especially proved its superiority over the piston in navigation. ”

“ The Curtis 1500-kilowatt steam turbine will be taken first and treated "from the ground up."
On entering a turbine plant on the ground floor, the attention is at once attracted by a multiplicity of pumps, accumulators and piping. These are called "auxiliaries" and will be passed for the present to be taken up later, for though of standard types their use is comparatively new in power-plant practice, and the engineer will find that more interruptions of service will come from the auxiliaries than from the turbine itself. ”

“ The application of the compound steam turbine to the propulsion of vessels is a subject of considerable general interest, in view of the possible and probable general adoption of this class of engine in fast vessels.
In the turbine is found an engine of extremely light weight, with a perfectly uniform turning moment, and very economical in steam in proportion to the power developed, and, further, it can be perfectly balanced so that no perceptible vibration is imparted to the ship. ”

“ It has been solely by organized ability, unfaltering faith in ultimate success, and massed capital, that the steam turbine has become the rival of the steam engine of Watt. A vast sum, expended during nine years, was required to perfect its delicate and exacting mechanism. One day a young engineer saw it whirling away at high speed; with the efficiency of the gas engine in mind, [415] he asked, “Why not drive a turbine by gas instead of by steam?” ”

“ For the rather low standards of horsepower on which dirigibles are driven, heavy steam engines of the ordinary type, although much more reliable, would be less economical than internal combustion engines, owing to the latter's better thermal efficiency. Engineers are attempting to evolve a light type of steam turbine that will overcome this drawback. ”

“ It is very noticeable that the best treatises on the steam turbine to-day are German, and begin with a large amount of theory on the properties of rotating discs, then of the thermodynamics of vapors, and finally of the flow of steam through jets, before the technical matters are touched. We are now hoping for the development of the gas-turbine, which shall combine the two advantages of the gas-engine and the turbine, and which will demand for its success all the knowledge of thermodynamics which we possess. ”

“ As there are no reciprocating parts in a steam turbine, and as a perfect balance of its rotating parts is absolutely essential to its successful operation, vibration is reduced to such a small element that the simplest foundations will suffice, and it is safe to locate steam turbines on upper floors of a factory if this be desirable or necessary. ”

“ If that obstruction be from any cause difficult to stir, the steam must pass round it until its pressure overcomes the inertia. Consequently the turbine differs from the cylinder engine in this respect, that steam can pass through and be wasted without doing any work at all, whereas, unless the gear of a cylinder moves, and power is exerted, all steam ways are closed, and there is no waste. In practice, therefore, it is found that a turbine is most effective when running at high speed. ”

“ The turbine is capable of running at higher speeds than the reciprocating engine, and at the greatest speeds it runs with a great deal less noise, and with practically no vibration at all. More than this, turbines take up much less room, and require less oil and attendance. The turbines are coupled directly to the dynamos, so that the two machines appear almost as one. In the power station shown on Plate V. a number of alternating current dynamos coupled to steam turbines are seen. ”

“ The combination of gas engines and steam turbines in a single plant promises improved efficiency whilst removing the objection to the gas engine, namely, its inability to carry heavy overloads. A steam turbine can easily be designed to take care of 100 per cent. ”

“ The idea is of course perfectly feasible, being indeed virtually that which is employed in the modern steam turbine; but to put the idea into practise requires special detailed arrangements of steam jet and vanes, which it is not strange the early inventor failed to discover. His experiments appear not to have been followed up by any immediate successor, and nothing practical came of them, nor was the principle which he had attempted to utilize made available until long after a form of steam engine utilizing another principle for the transmission of power had been perfected. ”

“ Although hardly beyond the stage of its first advent in the motive-power field, the steam turbine has met with much favor, and there is promise of its wide use for the purposes to which it is particularly adapted. ”

“ The Turbinia is 100 ft. in length, 9 ft. beam, 3 ft. draught amidships, and 441⁄2 tons displacement. She has three screw shafts, each directly driven by a compound steam turbine of the parallel flow type. The three turbines are in series, and the steam is expanded—at full power—from a pressure of 170 pound absolute, at which it reaches the motor, to a pressure of one pound absolute, at which it is condensed. ”

“ The economy of steam in the main engines is greater than usual.
At full speed the steam pressure in the boiler is two hundred and ten pounds; at the engines, one hundred and seventy-five; and the vacuum in the condenser twenty-seven inches, representing an expansion ratio in the turbines of about one hundred and ten after allowance has been made for wire-drawing in the exhaust pipe.
The first vessels of larger size than the Turbinia to be fitted with steam turbine machinery are the torpedo-boat destroyer Viper for the British Government, and a similar vessel for Messrs. ”

“ It will be noted that engine, generator, etc., work out at about 7 lb. per H.P. Considerable advance has been made in the construction of light and powerful model steam engines since Langley's time, chiefly in connexion with model hydroplanes, and a pressure of from 500 to 600 lb. per sq. in. has been employed; the steam turbine has been brought to a high state of perfection, and it is now possible to make a model De Laval turbine of considerable power weighing almost next to nothing, [21] the real trouble, in fact the only one, being the steam generator. ”

“ Turbine Alternator Winding.—For the reason that steam turbines run at so much higher speed than steam engines, the construction of armatures and windings for alternators intended to be direct connected to turbines must be quite different from those driven by steam engines. ”

“ They are more economical at high speeds. It must be remembered that a turbine is essentially meant for high speeds. If run slowly, the steam will escape through the many passages without doing much work.
Owing to its construction, a turbine cannot be reversed like a cylinder engine. It therefore becomes necessary to fit special astern turbines to one or more of the screw shafts, for use when the ship has to be stopped or moved astern. ”

“ Now that [70] steam turbines are scoring a success both on land and sea the contouring of their vanes with extreme nicety is an important problem of the engineer. A perfected form means the highest economy.
Curves of turbines.
Niagara Power Co.
It is interesting to note how the screw propeller, the fan, and the turbine wheel have each led to a converse invention. Mr. Edwin Reynolds, of Milwaukee, has devised a pump in screw form of capital efficiency under low heads. ”

“ When the steam consumption of a steam turbine is so much higher than the guaranteed quantity, it usually takes little less than a reconstruction to put things right. The minor qualifications of a machine, however, which can be examined into and tested with greater ease, and usually at considerably less expense, upon the site, and consequently under specified conditions, may be advantageously left over until that site is reached, where it is obvious that any shortcomings and general deficiency in performance will be more quickly detected and diagnosed. ”

“ The success of this little experimental vessel of 100 tons, which with its horse-power of 2100 made a record in speed for a ship of any size, was soon followed by the application of the turbine to various war-ships and other steamers. In war-ships the use of steam turbines has a special advantage in enabling the machinery to be kept at a low level, beneath the protective deck, in addition to the general advantages of reduced bulk, reduced vibration, reduced liability to break-down, and reduced consumption of coal and of oil which are common to vessels of all classes. ”

“ The Great Eastern was an experiment, but there is nothing of the experiment about the Mauretania and her sister, the Clyde-built ship Lusitania. The valuable data obtained from the running of the 20,000-ton turbine Cunarder Carmania has afforded a valuable object-lesson in adapting the turbine method of propulsion to liners of the leviathan class, demonstrating the suitability of the steam turbine to the largest type of vessel. ”

“ It is one of the remarkable things in the history and development of mechanism, that in this day of perfected steam engines, the inventors of our time should go back and utilize the principles employed in the first recorded steam engine, namely, the turbine. Instead of pressure exerting a force against a piston, as in the reciprocating engine, the steam acted by impacting against a moving surface, and by obtaining more or less reaction from air-resistance against a freely discharging steam jet or jets. ”

“ Attempts to design a steam turbine were made by numerous inventors, but fell short of practical success mainly because of the difficulty of arranging for a sufficiently high velocity in the working parts to utilize a reasonably large fraction of the kinetic energy of the steam, the principle involved being that for good efficiency the velocity of the blades should approximate to half the velocity of the jets which strike them. ”

“ Thus, while the screw outside of the hull is applying the force continuously, the steam in the inside is driving the shafting with equal evenness and regularity.
The steam turbine does not appear to have by any means reached finality in its form, such questions as the angle of impact which the jet should make with the surface of the vane, and [Pg 126] the size of the orifice through which the steam should be ejected, being still debatable points. ”

“ Gland Steam Turbine Supply
In order to further increase economy a radical change was made in the method of supplying the turbines with gland steam. As installed, all turbine glands required the use of live steam, which with turbines of such large dimensions, was quite an item. By a simple change in pipe leads and valves, the leak off from the H. P. ahead glands, which formerly led to the condenser, was piped to supply the glands of all astern turbines and the I. P. and L. P. ahead turbines, thus utilizing a three-inch line of steam which was formerly wasted in the condenser. ”

“ Its greater simplicity, compactness and freedom from vibration are merits which have already gone far to secure for it a preference, notwithstanding the short time that has passed since it became known as a practicable engine. The largest demands for power occur in fast passenger vessels, in war-ships and in stations from which electric energy is distributed for traction or other uses; in all these cases the steam turbine is now taking the leading place. ”

“ There is an obvious advantage in economy of space as compared with the reciprocating engine. The largest steam turbine constructed in the United States is one of 3,000 horse-power, which is installed in the power house of the Hartford Electric Light Company, Hartford, Conn. The total weight of this motor is 28,000 pounds, its length over all is 19 feet 8 inches, and its greatest diameter six feet. With the generator to which it is directly connected, it occupies a floor space of 33 feet 3 inches long by 8 feet 9 inches wide. ”

“ It will enable a designer to carry out all the ordinary calculations necessary for the construction of steam turbines, hence it fills a want which is hardly met by larger and more theoretical works. Numerous tables, curves and diagrams will be found, which explain with remarkable lucidity the reason why turbine blades are designed as they are, the course which steam takes through turbines of various types, the thermodynamics of steam turbine calculation, the influence of vacuum on steam consumption of steam turbines, etc. ”