Turbine

“ The turbine is only in its infancy, yet since its infantile influence has caused already so great a revolution, one hesitates to reckon what it will do before it is as old as the old-fashioned reciprocating engine, whose history we have outlined. Its modern practical invention is due to two men, one an Englishman, the other a Swede, who during the early ’eighties made their systems public. ”

“ A series of turbine wheels on one shaft were thus constituted, and each one complete in itself is like a parallel-flow water turbine, the steam, after performing its work in each turbine, passing on to the next, and preserving its longitudinal velocity without shock, gradually falling in pressure as it passes through each row of blades, and gradually expanding. ”

“ A turbine is a machine in which a rotary motion is obtained by transference of the momentum of a fluid or gas. In general the fluid is guided by fixed blades, attached to a casing, and, impinging on other blades mounted on a drum or shaft, causing the latter to revolve.
Turbines are classed in various ways as: 1, radial flow, when the steam enters near the center and escapes toward the circumference; and 2, parallel flow, when the steam travels axially or parallel to the length of the turning body. ”

“ The present form of turbine, with an efficiency of about 62 per cent., was a great advance, but even in this form of machine scarcely more than 1 per cent. or 2 per cent. is used in actually generating power at a given moment. The only part of the great wheel that is used in actually making power is the outside edge where the steam pushes on the buckets.
"The new turbine offers a striking contrast using as it does practically the entire material of the power-giving portion of the engine. The result is an economy that gives an efficiency of 80 per cent. ”

“ Any engineer who is capable of running and intelligently taking care of a reciprocating engine can run and take care of a turbine, but if he is to be anything more than a starter and stopper, it is necessary that he should know what is inside of the casing, what must be done and avoided to prevent derangement, and to keep the machine in continued and efficient operation. ”

“ In the Worthington turbine pump the efficient conversion of energy is assured by an original system of diffusion vanes disposed in the throat opening between the periphery of the impeller and the annular casing, in much the same manner that guide vanes are placed in a reaction turbine water-wheel. ”

“ Five thousand cubic feet of water a minute would give approximately 14 actual horsepower under such a head. A sluggish creek that flows in large volume could thus be utilized for power with the reaction turbine, whereas it would be useless with an impulse wheel. Falls of from five to fifteen feet are to be found on thousands of farm streams, and the reaction turbine is admirably adapted to them.
Reaction turbines consist of an iron "runner" which is in effect a rotary fan, the pressure and momentum of the column of water pressing on the slanted blades giving it motion and power. ”

“ He proposes to use the turbine in coast mills, the tide being the motive-power; and, strange as it sounds, the experiments seem to decide in favour of this plan.
"The turbine was invented by M. Fourneyron. Coals being abundant, the steam engine is invented in England; coals being scarce, the water-pressure engine and the turbine are invented in France. It is thus the physical condition of each country directs its mechanical genius. ”

“ 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. ”

“ 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. ”

“ There has been much published, both descriptive and theoretical, about the turbine, but so far as the writer knows, there is nothing in print that tells the man on the job about the details of the turbine in plain language, and how to handle these details when they need handling. The operating engineer does not care why the moving buckets are made of a certain curvature, but he does care about the distance between the moving bucket and the stationary one, and he wants to know how to measure that distance, how to alter the clearance, if necessary, to prevent rubbing. ”

“ The casing which contains each of the two low pressure turbines contains also a turbine for running astern, so that either or both of the two wing shafts may be reversed. Steam is admitted to the reversing turbine direct from the boiler, the centre shaft being then idle. Each astern-driven turbine consists of a comparatively short series of rings of blades, set for running in the reversed direction, developing enough power for this purpose but making no pretensions to high efficiency. ”

“ Steam enters the gland chamber at a slight pressure, and, when a vacuum exists inside the turbine casing, tends to flow inward. The pressure, however, inside the gland is increased until it exceeds that of the atmosphere outside, and by maintaining it at this pressure it is obvious that no air can possibly enter the turbine through the glands, to destroy the vacuum. The above principle must be borne in mind during a test upon a turbine having steam-fed glands. ”

“ The snake is the penstock—a great black steel pipe, twisting and turning to avoid the huge boulders in its path as it conducts that water from the summit into the turbines in the house.
The turbine is an enclosed water-wheel in which every particle of force in the rushing water is used to turn a great steel shaft. On the other end of that shaft is geared the generator—the wonderful machine with wire-wound arms which makes the electric current. At this particular power-house the little torrent which reaches the summit in a flume thirty inches wide and two feet deep turns out 800 horse-power. ”

“ But by restricting the turbine to the lower part of the pressure range and using a piston and cylinder engine for the upper part a higher economy is possible than could be reached by the use of either form of engine alone, the turbine being specially well adapted to make the most of the final stages of expansion, whereas the ordinary reciprocating engine in such vessels makes little or no use of pressure below about 7 ℔ per sq. ”

“ 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. ”

“ 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. ”

“ There are certain specified qualifications which a machine must hold when running under its commercial conditions, among these being lack of vibration of both turbine and machinery driven, be it generator or fan, the satisfactory running of auxiliary turbine parts directly driven from the turbine spindle, minimum friction between the driving mediums, such as worm-wheels, pumps, fans, etc., slight irregularities of construction, often resulting in heated parts and excessive friction and wear, and must therefore be detected and righted before the final test. ”

“ The water is supplied to the turbine by a vertical pipe, over which is a wooden pentrough, containing a strainer, which prevents sticks and other solid bodies getting into the turbine. The turbine rests on three foundation stones, and, the pivot for the vertical shaft being under water, there is a screw and lever arrangement for adjusting it as it wears. The vertical shaft gives motion to the machinery driven by a pair of bevel wheels. On the right are the worm and wheel for working the guide-blade gear. ”

“ It is always advisable to make a strict practice of getting all the auxiliary plant under way before starting up the turbine. In handling a turbine plant the several operations might be carried through in the following order:
(1) Circulating oil through all bearings and oil chambers. [5] (2) Starting of condenser circulating-water pumps, and continuous circulation of circulating water through the tubes of condenser. (3) Starting of pump delivering condensed steam from the condenser hot-well to weighing tanks. (4) Starting of air pump, vacuum being raised as high as possible within condenser. ”

“ In this turbine the energy of the fuel is liberated intermittently by successive explosions, instead of by continuous combustion, and in much the same way that the explosions occur in a reciprocating engine. Tests made on the new machine have shown that it is in no way inferior in efficiency to the ordinary type of motor, and that at full load, the weight per horse-power is only about one-quarter of that of the reciprocating engine. ”

“ 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. ”

“ Enormous turbines are used, fifteen feet in diameter, and when the installation is complete there will be thirty units, [82] each yielding 10,000 horsepower, or a total of 300,000 horsepower. A turbine, it may be explained, differs from the ordinary water wheel in the fact that the water runs through the wheel instead of around it (Figure 32) . The water may enter at the center and then flow out at the periphery, or it may enter at the periphery and then be discharged from the center of the wheel, or it may run axially through the wheel. ”

“ Turbine wheels are of several types, one operating in a closed tube to which air has no access, and another in an open space in the presence of air. The water may also be made to enter the turbine at the side or from below, thus serving to support the weight of the mechanism—a consideration of great importance in the case of such gigantic turbines as those that are employed at Niagara Falls, which we shall have occasion to examine in detail in a later chapter. ”

“ There is thus a fuller utilization of the kinetic energy of the gas, through carrying it from high to low pressure, than is possible with the old type of cylinder-and-piston engine. On the other hand, there is a constant loss due to the fact that the blades of the turbine can not fit with absolute tightness against the cylinder walls. The net result is that the compound turbine, as at present developed, appears to have about the same efficiency as the best engine of the old type. ”

“ Classification of Turbines.—In some turbines the whole available energy of the water is converted into kinetic energy before the water acts on the moving part of the turbine. Such turbines are termed Impulse or Action Turbines, and they are distinguished by this that the wheel passages are never entirely filled by the water. To ensure this condition they must be placed a little above the tail water and discharge into free air. Turbines in which part only of the available energy is converted into kinetic energy before the water enters the wheel are termed Pressure or Reaction Turbines. ”

“ For horizontal, direct-connected turbine wheels and generators the nearly uniform practice is to locate the generators in a single row from one end of a station to the other, and this brings the turbines into a parallel row. On this plan the shaft of each connected generator and its group of turbines sets at right angles to the longer sides of a station and approximately parallel with the direction in which water flows to the wheels. ”

“ Allied to the oil system of a turbine plant is the water service, of comparatively little importance in connection with single self-contained units of small capacity, where the entire service simply consists of a few coils and pipes, but of the first consideration in large installations having numerous separate units supplied by oil and water from an exterior source. The largest turbine units are often supplied with water for cooling the bearings and other parts liable to attain high temperature. ”

“ The advantage of a turbine engine is its simplicity—few working parts and a saving in weight and space; its disadvantage is that a separate turbine has to be employed to obtain sternway. Recently, geared turbines have been introduced which are lighter, slightly more economical in fuel, and are sweeter running machines.
It is noteworthy that whereas gears were necessary in olden times with engines working at a low pressure to speed up the propeller shaft, with turbines gears are used to reduce the revolutions.
SS. “Scotia,” 1860
Meantime, greater boiler efficiency was being obtained. ”