288 STEAM TURBINES
exerts the same pressure as that streaming in the opposite direction. The outflow sides of oach pair of working wheels are interconnected by means of circulating channels d, f, h. The object of this connection is the ensuring of an even steam pressure on the ring surfaces which are produced at the point of junction of two wheels of different diameters, and also to ensure those of the turbine shaft against an Fig. 536. end pressure in the one direction only. In the case of higher steam pressures the motive medium entors at the middle of the engine at the point a and streams through the turbine stages towards both ends. If the engine is to work with a pressure almost equal to that of the atmosphere and with the condenser, it would be possible to introduce the steam at each end, and allow it to discharge from the middle. The turbine wheels then increase from the ends towards the middle. However simple and self-evident a relieving method of this kind may be, in practice it is of only partial advantage, because, by the division of the steam over two small sets of wheels, the working economy suffers. 1 The arrangement of Schulz (1901) may be considered a very practical solution of the problem. In order to effect the total or partial neutralization of the axial Fig. 537. pressure, an axial turbine is combined with a radial ono, In Fig. 537 this arrangement is shown with a backwards- motion turbine on the left- hand side mounted on the same shaft with a larger forwards turbine (on the right). To take the forwards turbine first, it consists of the high-pressure turbine 2, and the low-pressure engine 1, through which the steam streams, one after the other, in contrary directions. The axial thrust is thus avoided. The Schulz speciality consists in the circumstance that the axial turbine body a and the radial turbine body b are so connected that both are 1 D. R. P. 135,937.
