In this type of turbine, all of the blading revolves (rather than only half the blades as in most turbines) - one half revolves in one direction and the other half in the other, so that the relative speeds of the two sets of blading is doubled and achieves a closer approximation to the correct relation of the speed of steam and blading than is possible in the conventional type. A necessary result of this arrangement is that a Ljungstrom turbine has two output shafts, one for each set of blades. In the case of turbine generators, this incurs the cost of two generators
Compared with conventional turbines, having blades located in stators, Ljungström turbines had considerable advantages in minising transient distortion and internal clearance changes during temperature changes. This meant that load could be applied much more quickly, ideal for peak lopping. On the downside, their construction was complex and demanded extensive precision machining, and assembly and dismantling were much more difficult than with conventional turbines. Also, the maximum blade allowable length was smaller than with conventional turbines, so where longer blades were needed they had to be accommodated in conventional axial flows.
The turbines were manufactured in Sweden by Svenska Turbinfabriks Aktiebolaget Ljungström, and later manufactured under licence overseas by companies including the Brush Electrical Engineering Co and Gio. Ansaldo and Co.
Sources of Information
- The Engineer 1918/05/07