A 2,250-H. P. TURBINE DESIGNED FOR MARINE AND OTHER SERVICE. the vanes by both impulse and reaction. Steam enters at the smaller end of the turbine, expanding parallel to the shaft, its volume gradually increasing and its pressures and temperature decreasing, until, finally, condenser conditions are reached. To accommodate the increase in volume, vanes of increasing length are used; and, when a mechanical limit is reached, the diameter of the spindle is abruptly increased. No similarity, therefore, exists between the three drums of the turbine and the three expansion stages of a triple-expansion engine, as is frequently believed. A much higher degree of expansion of steam is possible in a turbine, and, therefore, a greater economy. The design is very simple, there being no distribution valves, pistons, or connecting rods. To compensate for the small amount of thrust along the axis of the turbine, due to the pressure of the steam against the blades, three revolving balancing pistons are provided at the opposite end of the rotor. These rotate without friction in their casings, and automatically maintain a perfectly balanced condition along the shaft under all conditions of load and pressure. The bearings of the turbine and generator are oil-cushioned in order that they may be sufficiently flexible to absorb any slight vibrations occurring when the rotor is passing its critical speed-changing from its geometric to its gravity axis. These bearings consist of a set of loosely fitting bronze sleeves surrounding the shaft and supported by oiled films. They are constantly flushed with oil from a reservoir supplied by a small plunger pump which is operated from the governor shaft. The steam is controlled by a sensitive centrifugal governor, geared from the turbine shaft and adjustable while running, thus enabling alternating-current generators to be successfully operated in multiple. Steam is admitted in short puffs, the governor varying the period of admission. The automatic adaptability of the turbine to heavy overloads is effected with the aid of a by-pass in the cylinder, through which high-pressure steam may be admitted directly to the second, or middle, drum of bladesthe internal pressure at this point, and therefore the capacity of the engine, be solutely uniform, and no reciprocating forces are encountered, the unit is simply set upon the floor without faster.ings. A complete condensing outfit is installed in the pit, consisting of a surface condenser having 1,500 square feet of cooling surface, a rotating dry vacuum pump 6 by 10 by 10 inches, providing a constant vacuum of 251⁄2 inches. The condensed steam from the turbine flows into a hot well at the bottom of the condenser, from which it is pumped to the boiler. The Turbo-Generator When it forms a portion of an electrical generating unit, the turbine is usually direct-connected to the generator, as is frequently the case where other forms of steam or hydraulic power are brought into service. The turbine shown in the accompanying illustration was connected with a generator having a rated capacity of 400 kilowatts, and was capable of delivering a three-phase alternating current of 440 volts, the number of alternations. being 7,200. As an indication of the service provided by this type of turbine, it may be said that it actually revolved VIEW OF TURBINE AND GENERATOR. Taken while in operation. 130 pounds. It has actually pumped 250 gallons per minute, representing a total lift of no less than 700 feet. The turbine pump, however, has been manufactured in sizes as large as 300 horse-power, with a capacity of 2,000 gallons per minute and 500 feet head. These turbines are operated both at low pressure and at high pressure, the low-pressure turbine. being of the centrifugal pattern, having turbine and pump mounted on the same base. The high-pressure pattern works on the same principle as the low-pressure pump, and is being placed in service for fire protection, for operating hydraulic elevators, and in municipal waterworks. The Machine Shop Turbine As already stated, the turbine is now taking its place in the shop for driving power tools of various kinds. In most instances, power is communicated by THREE-QUARTERS VIEW OF THE SAME MECHANISM AND ITS CONNECTIONS. with other forms of steam power, has caused it frequently to be preferred by steam users where floor space is limited; but it can be employed in vertical as well as horizontal designs. The Vertical Turbine The accompanying illustration gives an idea of the compactness of the vertical sign a moderate rotative speed is permitted, as the turbine is divided into stages each of which contains one, two, or more revolving buckets supplied with steam from a set of expansion nozzles. Consequently the nozzle velocity in each stage is reduced. Under this arrangement, the energy of the moving steam |