Experimental and numerical studies on an OWC axial-flow impulse turbine in reciprocating air flows

Abstract

In this study, an experimental facility and a transient numerical model are established to predict the complicated unsteady behaviors of oscillating water column air turbines under reciprocating air-flow conditions, which are closer to the actual sea states. There are a total of 256 cases in the experimental test. Three starting modes for the axial impulse turbine in symmetrical reciprocating air flows are identified, and over 93% of the cases are found to be self-starting cases. The peak cycle-averaged turbine efficiency is 0.53, which is larger than that observed in the steady-state tests. Compared to the efficiencies derived from the steady-state tests, the turbine has the possibility to achieve a better performance in the reciprocating air flows even under the same pneumatic power input. The numerical model is compared and validated by the experimental results. Effects of constant load on turbine performance are investigated numerically. An irregular air-flow profile based on the local sea-state is generated. The turbine self-starting processes under various moments of inertia are simulated numerically, and the angular velocities, torque outputs and the pneumatic powers are predicted and compared.