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such manner that a very slight movement of the balls serves to produce the required change in the supply of steam. The ball levers swing on knife edges instead of pins. The governor works both ways, that is to say, when the levers are oscillating about their mid position a head of steam corresponding to full load is being admitted to the turbine, and a movement from this point, either up or down, tends to increase or to decrease the supply of steam.
Fig. 203. SECTION OF WESTINGHOUSE-Parsons TURBINE GOVERNOR.
Ques. 751.-What can be said of the efficiency of the Westinghouse-Parsons steam-turbine?
Ans.-Under test a 400 kilowatt Westinghouse-Parsons steam-turbine, using steam at 150 pounds initial pressure and superheated about 180 degrees, 'consumed 11.17 pounds of steam per brake horse-power hour at full load. The speed was 3,550 revolutions per minute and the vacuum was 28 inches. With dry saturated steam
the consumption was 13.5 pounds per brake horse-power hour at full load, and 15.5 pounds at one-half load. A 1,000 kilowatt machine, using steam of 150 pounds pressure and superheated 140 degrees, exhausting into a vacuum of 28 inches, showed the very remarkable economy of 12.66 pounds of steam per electrical horsepower per hour.
A 1,500 kilowatt Westinghouse-Parson turbine, using dry saturated steam of 150 pounds pressure with 27 inches vacuum, consumed 14.8 pounds steam per electrical horse-power hour at full load, and 17.2 pounds at one-half load.
Ques. 752.—What efficiency does the Curtis turbine show in the use of steam?
Ans.-A 600 kilowatt Curtis turbine operating at 1,500 revolutions per minute, with steam at 140 pounds gauge-pressure and 28.5 inches vacuum, showed a steamconsumption as follows, steam superheated 150 degrees: At full load, 12.5 pounds per electrical horse-power per hour; at half load, 13.25 pounds per electrical horse-power per hour; at one-sixth load, 16.2 pounds per electrical horse-power per hour, and at one-third overload, 12.4 pounds per electrical horse-power per hour. ! Ques. 753.-Describe in brief terms the HamiltonHolzwarth steam-turbine.
Ans.-The Hamilton-Holzwarth steam-turbine is based upon and has been developed from the designs of Prof. Rateau, and is being manufactured in this country by the Hooven-Owens-Rentschler Company, of Hamilton, Ohio. It is horizontal and placed upon a rigid bed-plate of the box pattern. All steam, oil and water-pipes are
within and beneath this bed-plate, as are also the steaminlet-valve and the regulating and by-pass valves. The smaller sizes of this turbine are built in a single casing or cylinder, but for units of 750 kilowatts and larger the revolving element is divided into two parts, high and low pressure. This turbine resembles the Westinghouse-Parsons turbine in some respects, prominent of which is that it is a full-stroke turbine, that is, that the steam flows through it in one continuous belt or veil in screw line, the general direction being parallel with the shaft. But, unlike the Parsons type, the steam in the Hamilton-Holzwarth turbine is made to do its work only by impulse, and not by impulse and reaction combined.
It might thus be termed an action turbine.
Ques. 754.-Describe the interior construction of this turbine.
Ans.-The interior of the cylinder is divided into a series of stages by stationary disks which are set in grooves in the cylinder and are bored in the center to allow the shaft, or rather, the hubs of the running wheels that are keyed to the shaft, to revolve in this bore. There are no balancing pistons in this machine, the axial thrust of the shaft being taken up by a thrust ball-bearing. Between each two stationary disks there is located a running wheel, and the clearance between the running vanes and the stationary vanes is made as slight as is consistent with safe practice.
Ques. 755.—Describe the construction of the running vanes and the action of the steam upon them.
Ans. The running vanes conform in section somewhat
to the Parsons type, but the action of the steam upon them and also within the stationary vanes is different. The expansion of the steam and consequent development of velocity takes place entirely within the stationary vanes, which also change the direction of flow of the steam and distribute it in the proper manner to the vanes of the running wheets, which, according to the claims of the makers, the steam enters and leaves at the same pressure, thus allowing the wheel to revolve in a uniform pressure.
Ques. 756.—What provision is made in the Hamilton-Holzwarth turbine for maintaining the velocity of the steam as it expands?
Ans. The first stationary disk of the low-pressure turbine has guide-vanes all around its circumference, so that the steam enters the turbine in a full cylindrical belt, interrupted only by the guide-vanes. To provide for the increasing volume as the steam expands in its course through the turbine, the
F10. 204. GENERAL VIEW OF A HAMILTON HOLZWARTH STEAM-TURDINA.
areas of the passages through the distributers and running vanes must be progressively enlarged. The gradual increase in the dimensions of the stationary vanes permits the steam to expand within them, thus tending to maintain its velocity, while at the same time the vanes guide the steam under such a small angle that the force with which it impinges against the vanes of the next running wheel is as effective as possible. The curvature of the vanes is such that the steam while passing through them will increase its velocity in a ratio corresponding to its operation.
Ques. 757.-Describe the method of regulating the speed of this turbine.
Ans.---The governor is of the spring and weight type, adapted to high speed, and is designed especially for turbine governing. It is directly driven by the turbineshaft, revolving with the same angular velocity. Its action is as follows: Two disks keyed to the shaft, drive, by means of rollers, two weights sliding along a cross-bar placed at right angles through the shaft and compressing two springs against two nuts on the cross-bar. Every movement of the weights, caused by increasing or decreasing the angular velocity of the turbine-shaft, is transmitted by means of levers to a sleeve which actuates the regulating mechanism. These levers are balanced so that no back pressure is exerted upon the weights. The whole governor is closed in by the disks, one on each side, and a steel ring secured by concentric recesses to the disks. In order to decrease the friction within the governor and regulating mechanism, thrust ball bearings and friction