Hensekel-Jonval Turbine.—Figure r5 (p1. 67) gives an illustration of the extended casing or tube of the Henschel-Jonval system. Two high-pressure turbines (twin turbines) stand beside each other and act conjointly 'upon the central transmitting shaft at the top by means of spur wheels on the tipper ends of the turbine-shafts which project through stuff ing-boxes in the covers of the wheel-cases. The influx pipes are indicated by the two black circles, and immediately below these in the casing are the guides and turbine-wheels, whose casings extend to the lower channel, forming an air-tube extending to and under the surface of the tail-water. Jonval, in taking out a patent for such a turbine in 1841, four years later than Henschel, and at a time when one of Henschel's twin turbines was actually driving a stone-polishing establishment at Minden in the duchy of Brunswick, called his construction a "double-effect" turbine. This designation may be said to be correct, inasmuch as such turbines act by suction as well as by pressure, since the effect is produced by the water in the tube beneath the wheel as well as by that standing above it.
three Geyelin-Jonval turbines at the Philadelphia waterworks, shown in Figure 6 (pl. 69), are each feet in diameter, with sixty blades in the movable wheels, and are the largest of their kind in America. They are of the Jonval system—that is, they receive the water on the top, where it is directed by guides and dis charged downward into draught tubes. At the bottom end of each tube there is a controlling gate in the form of a cylinder, which is made to rise or lower as the power is needed for driving the pumps. The movable wheels are placed on vertical shafts, which were originally supported on lignum yam steps, but these have in part been replaced by glass suspension-boxes (figs. 3, 4), which were found better to answer the purpose of supporting the weight of the water and the machinery (which is calculated to amount to 30,00o pounds) than the lig-num-vite steps. The suspension-boxes are secured to the top of the inlet-casing. These turbines were constructed to force to a height of 125 feet 8,000,000 gallons of water every twenty four hours, with a fall of 8 feet. This work they regularly perform even with a reduced fall. The fall varies with the tides from 5 feet to 13 feet; when at its maximum the turbines are to a great extent closed, so as to check their power. With the view of maintaining a fair percentage of effectiveness of the water in all conditions of the fall, one of the turbines is arranged with a division in both the movable and the guide wheel: by means of this division one-third of the water can be shut off. Each of the three turbines is connected, by means of a pair of bevel and a pair of spur-mortise gears, to two horizontal double-acting piston-pumps of 22 inches diameter and 6 feet stroke.
Figurer represents an American improved Jonval turbine with double hood-gates placed immediately over the guide-wheel, which arrangement has several advantages over other forms of gates. Figure 2 exhibits au
American duplex turbine of the Jonval sytem. This turbine is divided into two unequal compartments, each having its own gate and independ cut gate-motion. This form of turbine has the advantage of being com pact and of using economically while in motion—that is, without stopping the machinery operated—one-third, one-half, or two-thirds the water the turbine is capable of absorbing.
The Lefel Double Turbine (pl. 66, figs. 9, to) has a combination of two independent sets and kinds of buckets, one a vertical, the other a cen tral discharge, each set being entirely unlike the other in its principle of action upon the water, yet each wheel or series of buckets receiving its water from the same set of guides at the same time; but the water is acted upon only once, since half the water admitted by the guides passes to one wheel and the other half of the water to the other wheel, the water being nicely separated and divided by the partition or diaphragm between the two wheels, and leaving both wheels or sets of buckets at the same time and as quickly as possible. These two sets of buckets are so combined as to make really but one wheel—that is, both are cast in one piece and placed upon the same shaft. Figure to exhibits the general appearance of the wheel ready for attachment of the shaft above it.
Girard's examples of novel arrangement in the con struction of turbines, we give Girard's "siphon" turbine and "hydro pneumatic " turbine, represented in Figures t and 2 (pl. 68). The inter nal structure of the former, except its hydro-pncumatization, corresponds with that of the latter. The object of the siphon-shaped supply-pipe is to permit the water to pass into the wheel free from the rapid circular motion which occurs notwithstanding there may be a very small height of fall. Hydro-pnenmatization consists in pumping air by means of a pump suspended in the wheel into a receiver (fig. 2), which is formed by the hermetically-closed casing of the turbine-wheel, the object being to force the level of the water below the wheel, which otherwise would be submerged in the tail-water and its motion impeded by reason of the frictional resistance therein. What is still more essential is to over come a phenomenon (f/. 66, jars. 5, 6) which has the tendency to decrease the effect. It will be seen that in case the single sluice or flume of the previously-described constructions is partially lowered, the water passes through the spaces of the paddle-wheel in a turbulent state accompanied by rapid circular motion and consequent loss of effect. These rapid rota tions can be controlled by passing compressed air from the pneumatized casing into the spaces of the paddle-wheel by means of apertures in the latter, as seen in Figure 6. Moreover, by pneumatization, those losses of effect which originate by the tail-water penetrating the empty paddle spaces are suppressed in their incipiency.