Prediction of the Cross-Flow Turbine Efficiency with Experimental Verification

Abstract

Recent experimental studies suggest that the usual way of measuring and predicting the efficiency of the cross-flow turbine do not describe the flow physics adequately. This verification led to the present investigation of some of the more relevant aspects related to the efficiency of this type of turbine. After presenting a detailed description of the rig used in the tests, the most adequate way of measuring the efficiency is discussed, including the specification of the proper datum used for the measurement of the head. Typical curves for the measured efficiency are shown, demonstrating that a peak efficiency of 84.8% is attainable with the cross-flow turbine, using new geometric relations, markedly different from those proposed by the present know-how in this field. Analysis of the experimental data seems to suggest that one of the reasons for the detected discrepancies is the assumption for the direction of the flow leaving the rotor. The consequences of the new physical insight are explored in this paper, leading to new theoretical relations for the efficiency evolution. It is demonstrated that the new theory describes reality better than previous analysis by comparing some of its predictions with experimental data.