Modeling of 3-D Losses and Deviations in a Throughflow Analysis Tool

The throughflow level of approximation still remains an important tool for designing turbomachines [2] even though 3-D calculations are used more and more early in the design process. The throughflow models heavily rely on empirical inputs such as 2-D correlations or end-wall loss models. This feature has shown to be efficient but lack of generality. Two-dimensional empirical correlations are available in the literature but they have generally been designed for classical families of blade profiles such as C4 or NACA-65 and are not directly applicable to the custom-based profiles nowadays used in the industry. However, it is possible to adapt existing loss correlations to modern blade profiles [5] or to derive correlations for an arbitrary profiles with the help of blade-to-blade codes [6]. Concerning the 3-D losses, very few results are available in the open literature. The main contribution on the compressor side is from Roberts et al. [7, 8]. They proposed correlations based on collected empirical data to build up 3-D distributions of loss coefficient and deviation in the end-wall regions. A throughflow analysis tool based on an inviscid model, supplemented with these 3-D correlations for the end-wall losses is the first approach studied here. The second approach presented in this contribution is directly based on the Navier-Stokes equations with blade force modifications close to the end-walls to capture the end-wall flows. By including more physics in the model, less empiricism is needed and a more general method can therefore be devised. The objective of the present work is to test both approaches for the modeling of the end-wall flows within a throughflow model. The results are compared to a series of 3-D Navier-Stokes calculations performed on axial compressor rotors.