This paper is a continuous study of a previously investigated novel winglet-shroud (WS) tip configuration. Two additional sealing fins are fixed on the WS tip to further reduce tip leakage. This configuration is referred to WS with seals (WSS) tip. Secondary flow structures and total pressure loss coefficients on a transverse plane downstream of the blade trailing edge are measured. Flow in a blade cascade is also numerically simulated to obtain more information of flow fields. Compared with the WS tip, both experimental and numerical results show that the WSS tip can further improve the aerodynamic performance as expected. Relative to the plain tip, the WSS and WS tips can reduce total pressure loss on one plane downstream of the blade trailing edge by 50% and 28%, respectively. This is mainly due to reduced intensity of tip leakage vortex (TLV). For the tip leakage mass flow rate, the WS tip decreases it by 33.6%, while the implement of two additional sealing fins contributes to an extremely high reduction of 88.7%. This demonstrates that the use of sealing fins is effective to control the tip leakage flow and improve flow fields. In addition, a deeper analysis by applying a normalized helicity scheme to identify the evolution of different vortices and by tracing trajectories of the fluid near the tip offers credible supports for results.

A comparative experimental and numerical analysis is carried out to assess the aerodynamic performance of a novel partial shroud in a straight turbine cascade. This partial shroud is designed as a combination of winglet and shroud. A plain tip is employed as a baseline case. A pure winglet tip is also studied for comparison. Both experiments and predictions demonstrate that this novel partial shroud configuration has aerodynamic advantages over the pure winglet arrangement. Predicted results show that, relative to the baseline blade with a plain tip, using the partial shroud can lead to a reduction of 20.89% in the mass-averaged total pressure coefficient on the upper half-span of a plane downstream of the cascade trailing edge and 16.53% in the tip leakage mass flow rate, whereas the pure winglet only decreases these two performance parameters by 11.36% and 1.32%, respectively. The flow physics is explored in detail to explain these results via topological analyses. The use of this new partial shroud significantly affects the topological structures and total pressure loss coefficients on various axial cross sections, particularly at the rear part of the blade passage. The partial shroud not only weakens the tip leakage vortex (TLV) but also reduces the strength of passage vortex near the casing (PVC) endwall. Furthermore, three partial shrouds with width-to-pitch ratios of 3%, 5%, and 7% are considered. With an increase in the width of the winglet part, improvements in aerodynamics and the tip leakage mass flow rate are limited.

An improved inverse method for turbomachinery design is developed in this paper. A strict ‘no-slip’ boundary condition is imposed during the flow time marching process, and a virtual movement velocity is computed based on characteristics boundary conditions according to the difference of specified and calculated pressure loading, then the camber line of the blade is moved accordingly. A new ‘inverse’ time step calculation method is proposed to make the value of the ‘inverse’ time step case-independent, and a coupled non-uniform rational B-spline (NURBS) smoothing technique is used to improve the robustness of the solver, also guarantee the manufacturability of the obtained blade. Two-dimensional test cases, including compressor and turbine cascades, are adopted to validate the method. Then, the method is extended to three dimensions, and a high-loaded rotor of a fan stage is redesigned by the method in a stage environment. The final results indicate a fairly large performance gain, which demonstrates the effectiveness of the improved method.