Numerical Investigation on the Flow Characteristics in Axial-Inlet Cover-Plate Cavities

This paper investigates the complex flow characteristics and parameter prediction methods for axial-inlet cover-plate cavities in pre-swirl systems numerically. Using a full-annulus three-dimensional computational model, the flow mechanisms of cover-plate cavities are compared between axial and radial inlet configurations. The analysis reveals that the axial-inlet configuration exhibits intensified non-axisymmetric vortex pairs in the low-radius region due to axial inflow inertia. These vortex structures enhance radial angular momentum exchange, leading to a substantial inlet angular momentum deficit that consequently reduces swirl ratios and pressure coefficients relative to the radial-inlet configuration. Furthermore, parametric studies demonstrate that small gap ratio amplifies circumferential flow non-uniformity through strong impingement effects, while elevated inlet swirl ratio significantly extends the source region boundary by strengthening centrifugal forces. To address the prediction discrepancies in existing models, this work proposes a modified correlation for the effective inlet swirl ratio that account for the inlet momentum loss and develops a new predictive model for the edge of source region incorporating centrifugal effects. These physics-based corrections, validated against simulation data, significantly improve the prediction accuracy for axial-inlet cover-plate cavities compared to conventional models.