Improvement of energy performance of the axial-flow pump by groove flow control technology based on the entropy theory

Abstract

Energy loss is a key factor affecting the performance of the axial-flow pump, especially under the low flow conditions when sharply decrease of energy performance happens and strong vibration of the units poses great threats to the system safety. To address this problem, the entropy theory was utilized to quantitatively analyze and accurately locate the energy loss of axial-flow pump under different working conditions, and to analyze the improvement of energy performance of the axial-flow pump by groove flow control technology. The energy loss characteristics before and after the addition of grooves were compared under different flow rates, and the mechanism of improving energy performance of the axial-flow pump by groove flow control technology was revealed. 1) The impeller and guide vane are the main regions of energy loss in the flow passage under different flow conditions, which is of vital importance to the energy performance. Under the low flow conditions, the energy loss of the inlet pipe region is also nonnegligible, averagely accounts for 30% of the total entropy production in the saddle area. 2) The high entropy generation area in the impeller region is concentrated near the blade tip on the cylinder surface besides the shroud and the high entropy generation area in the inlet pipe region is besides the wall near inlet of the impeller under the low flow conditions. 3) After adding grooves, the total entropy production of axial-flow pump decreases under low flow conditions, especially under the deep stall condition, 5.32% in the impeller region and 17.26% in the inlet pipe region, leading to an increase of head by 65.77%. 4) Under the deep stall condition, the elimination of main passage vortex and the weakening of clearance vortex in the impeller region will lead to a significant decrease of the local entropy generation in the impeller, which is the underlying causes of the improvement of the energy performance in the saddle area of the axial-flow pump. The groove flow control technology applied in this paper can effectively improve the energy performance of the axial-flow pump, which provides valuable references for the improvement of energy characteristics in similar hydraulic machinery.