RELIEVING ARRANGEMENTS 287
the steam gains admission to the shaft. Teulon, on the other hand, diverts the
axes of the steam outlet nozzles from the plane of rotation and sets them at such
an angle to the latter that, in working, in addition to the back pressure tending to
produce rotation, an axial pressure remains over, which, it is true, is here intended.
to counteract the thrust of the propeller.
A convenient expedient also consists in the dividing of the turbine into parts in
such a manner that the steam has to stream through the one set of wheels in the one
axial direction, and the other set in the opposite one. This method has been chosen
by Parsons (1884) (Fig. 535) in one of his older arrangements. On the turbine
body a, which is in one piece with the shaft s, are shipped the rings b, divided
2 72 & g 0
Fig. 535.
equally, as regards numbers, at the two sides of the ring projection s¹. Round the latter extends an annular chamber, which is fed by fresh steam through the steam- inlet 9. The vanos b¹, b² on the rings have only about half the breadth of the latter, so that the guide vanes f, ff find room between them, which is worked out of the rings fixed in the case. From the above-mentioned annular chamber fed from g the steam streams through the turbine in both the axial directions to the chambers h. From these latter, channels lead to the exhaust h¹. The increase of volume of the steam is allowed for by an increase in the radial vane breadths given in the direction of flow of the steam. The last working-wheel rings a², which serve as end pieces, are pressed by means of nuts s against the body a and its rings b². The shaft s is packed in the end walls of the case by means of brass rings y and brass coupling- boxes y'. Outside of these packings there are also the chambers o, from which any steam that may get through is drawn by an injector.
Parsons (1887) has triod to improve the alteration given in Fig. 536. The turbine is mounted on a single shaft and its diameters are increased by steps in the direction of flow of the steam. The arrangement is so made that as the pressure decreases a greater peripheral velocity can be attained. There are several (e.g. three) pairs of working wheels c, e, g, so that the steam streaming in the one axial direction E, P. 706 of the year 1874. ² D. R. P. 33,066; Proc. of the Instit. of Mech. Eng., 1888. 3 D. R. P. 41,479.
