Mechanisms of Loss Surge and Evolution in a Highly Loaded Transonic Turbine Nozzle Guide Vane: A Novel Loss Decomposition Method via Micro-Streamtube Energy Analysis

Abstract

Highly loaded turbines can effectively reduce the number of turbine stages and enhance the engine thrust-to-weight ratio by increasing the aerodynamic loading per stage. However, the associated loss mechanisms are highly complex and involve multiple interacting sources. Further performance improvements will be severely constrained if the dominant loss components cannot be accurately identified and controlled. Therefore, the present study proposes a novel turbine flow field loss decomposition method based on micro-streamtube energy analysis. In this approach, numerous independent streamtubes are first introduced along the actual flow field, with each discretized into a series of micro-streamtube elements in the streamwise direction. A local loss evaluation model for each micro-streamtube is then established using the energy conservation principle, enabling direct quantification of flow energy dissipation. Finally, by integrating shock-wave detection and vortex identification criteria, total loss is decomposed and quantitatively apportioned according to the physical mechanisms of each loss source. Results from a highly loaded transonic turbine nozzle guide vane show that the dominant loss mechanism shifts from frictional and secondary flow losses to shock losses as Mach number increases. When Mach number exceeds the design condition, total loss rises sharply by approximately 30%, with the contribution of shock losses increasing by 21.2% and remaining dominant thereafter. The micro-streamtube-based loss decomposition method developed herein provides a new framework for quantitative evaluation of turbine flow field losses and offers theoretical support for targeted aerodynamic loss control and optimal design of highly loaded turbines.