York, and while retaining the advantage of the expanding nozzle of De Laval, it at the same time utilizes the energy acquired by velocity, by causing the steam to FIGURE 139. GOVERNOR FOR 5,000 K. W. TURBINE. impinge the moving buckets of two or more wheels in succession. A portion of this velocity force is given. up in the first stage, and another portion in the second stage, and this process is repeated, the steam in each case being first caused to expand in divergent nozzles and thus acquire new velocity before it is allowed to impinge the moving blades of the next lower stage. The pressure in each succeeding stage of expansion becomes lower and lower, until finally vacuum is reached. As previously stated, two of the main sources of economy that the steam turbine possesses in a much higher degree than does the reciprocating engine are: variations in load to the same degree as is the efficiency of the reciprocating engine. A 600 K. W. Curtis turbine operating at 1,500 R P. M., with steam at 140 lbs. gauge pressure and 28.5 in. vacuum, showed a steam consumption as fo' ows, steam superheated 150°: At full load, 12.5 lbs. per E. H. P. per hour. At one-sixth load, 16.2 lbs. per E. H. P. per hour. hour. This would seem to indicate that the efficiency of the steam turbine increases with overload, at least up to a certain point. In another test of a Curtis turbine, using dry saturated steam of 145 lbs. gauge pressure, the steam consumption at full load was 14.76 lbs. per E. H. P. hour, and at half load the rate was 15.95 lbs. per E. H. P. hour. The same machine using steam superheated 150° showed a steam consumption of 13.27 lbs. per E. H. P.hour, at full load. A Curtis turbine carrying a commercial load on a 15hour run showed an average coal consumption as follows; the turbine was operated with one boiler independently of the other boilers in the battery, and the steam was not superheated: Coal consumed per E. H. P. hour, 1.86 lbs. The highest type of modern reciprocating engine, triple expansion, condensing, having steam jacketed cylinders, shows a coal consumption of 1.5 to 2 lbs. per H: P. per hour, assuming the evaporation to be 8 lbs. water per pound of coal. THE HAMILTON-HOLZWARTH STEAM TURBINE The Hamilton-Holzwarth steam turbine-Points of difference between it and the Westinghouse-Parsons-Small clearances necessary-Stationary discs and guide vanes-Running wheels-Expansion of the steam and where it occurs-Action of the steam within the machine-Various stages in high and low pressure casings-Curvature of vanes-Purpose of stationary discs-Thrust ball bearings-Description of the gov ernor and regulating mechanism-Close regulation-Method of changing speed while running. 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. 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 Co. 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 steam inlet 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. There are no balancing pistons in this machine, the axial thrust of the shaft being taken up by a thrust ball-bearing. The interior of the cylinder is divided. into a series of stages by stationary discs 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. The clearance allowed is as small as practical, as it is in this clearance between the revolving hub and the circumference of the bore of the stationary disc that the leakage losses occur. It should be noted that between each two stationary discs there is located a running wheel, and that the clearance between the running vanes and the stationary vanes is made as slight as is consistent with safe practice; otherwise leakage. would occur here also, and besides this there would be a distortion of the steam jet and entrainment of the surrounding atmosphere, resulting in a rapid decline in economy if the clearance between the stationary and moving elements was not reduced to as small a fraction as possible. As before stated, the stationary discs are firmly secured to the interior walls of the casing. At intervals on the outside periphery of these discs are located the stationary or guide vanes. These are made of drop forged steel. They are set in a groove on the outside edge of the disc and fastened with rivets. Both disc and vanes are then ground, giving the vanes the profile that they should have for the most efficient expansion of the steam. After this is done a steel ring is shrunk on the outside periphery of the vanes and the steam |