On high efficiency operation of contra-rotating axial flow pump with rotational speed control toward effective energy saving

For high specific speed pump with high performance operation, a contra-rotating axial flow pump has been proposed and the effectiveness of rotational speed control of front and rear rotors has been demonstrated experimentally. In the present paper, a prediction method of pump characteristics under the condition of optimized rotational speed control is proposed, based on consideration of flow mechanism in both front and rear rotors. The accuracy of prediction is examined for two combinations of front and rear rotors. Then, the amount of energy saving by application of rotational speed control method for the contra-rotating axial flow pump is demonstrated and an advantage of usage of contra-rotating pump is discussed.