Studies on cross-flow water turbines. (Further report, application to low head)

Abstract

Cross-flow water turbines have recently been recognized for their small hydropower. Though such turbines are applied to the middle head usually, the height of the head for small hydropower is low. As the cross-flow turbine profile for the low head, however, has scarcely been investigated, this report intended to obtain its desirable profiles. The main results are as follows. (1) The inlet nozzle, arranged at the upper side of the runner, gives the best efficiency of various nozzle positions. (2) The water level in the runner chamber should be kept at 90% of the height of the runner diameter measured from the lower tip of the runner, for utilizing the draft head effectively. (3) Though the runner is submerged, in this case, the turbine shaft is almost free form the water flow because air stored in the upper part of the runner chamber is supplied naturally to the runner inside.