Through-flow modelling has been used for decades in axial turbomachines, either for blade design based on stage target performance, or for further analysis during the design process in case of design revaluation. Although its role in the past years has decreased in favour of more expensive but higher-fidelity CFD methods, it remains an essential tool for the design of turbomachines. Its ability to do fast computations is especially relevant for parametric studies during design improvement phases in which many parameters are involved. Another crucial feature is its ability to efficiently&nbsp;recompute from experimental data the aerodynamic flow field inside the entire machine.&nbsp;The computational efficiency of through-flow modelling stems from the pitch-wise average approach on which the model is based to predict the three-dimensional flow field by an averaged two-dimensional through-flow in the meridional plane. However, these axisymmetric calculations cannot capture some of the flow features (three-dimensional interaction of the blades with the annulus end-walls, …). Moreover, blades do not appear explicitly as solid surfaces inside the channel. All these effects must thus be integrated through the use of empirical models. Consequently, the accuracy of through-flow models heavily depends on the calibration of these empirical models. The drawback of this methodology is that a validated calibration on a given machine might not be adapted for another machine, especially if its design significantly differs from that for which the models have been calibrated. Additionally, the calibration of such a model based on modern engine design is often kept confidential. As a consequence, very little information dedicated to through-flow models applied to modern turbomachine design is found in the literature.&nbsp;In this context, we present a viscous through-flow model based on the Navier-Stokes equations and using a time-marching method. Its formulation follows the Adamczyk’s averaging cascade to derive in a rigorous and exhaustive manner the exact averaged equations and the mathematical expression of unclosed source terms.&nbsp;&nbsp;Using existing models from the literature, the through-flow model is applied to two different geometries using an analysis formulation: the classic axial compressor stage CME2 and a modern highly loaded multi-stage axial low-pressure compressor. The results are compared with higher-fidelity results including 3D RANS computations to assess their reliability for design and off-design conditions. Finally, suggestions to extend the models to a larger range of designs are discussed.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;

Application of a Viscous Through-Flow Model to a Modern Axial Low-Pressure Compressor

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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