Synergy analysis of the internal flow resistance and application in axial-inflow turbine

Abstract

The internal flow field and loss distributions are quite complicated in the axial-inflow turbine. It is necessary to develop physical understandings of the flow and losses. The synergy relationship between the velocity and velocity gradient, which can be revealed by mathematical expressions in the cylindrical coordinates, is innovatively applied to the internal flow field of axial-inflow turbine. According to the mathematical expression, the smaller the synergy angle is, the higher flow resistance and loss should be. To assess the validity of the synergy principle, the relationship between the synergy angle and flow characteristics is analyzed in detail. It is found that the regions where the high energy loss and entropy generation locate correspond to the relatively low synergy angle, which agrees well with the mathematical analysis. The relatively low synergy angle in the axial direction could represent high-loss regions near the blade surface and wake on the θ−z stream surface. The relatively low synergy angle in the radial and circumferential direction could represent high-loss regions near the endwall and wake on the θ−r stream surface, respectively. An apparent negative correlation between the loss coefficient and synergy angle could be perceived under off-designed conditions. It is recommended the synergy angle should be kept in relatively low magnitudes to reduce losses for the design or optimization routines of axial-inflow turbines.