EXTENSION OF THE MULTALL OPEN SOURCE THROUGHFLOW CODE FOR THE IMPROVED OFF – DESIGN CALCULATIONS

Date

2024-01-01

Author

Bilgiç, Mustafa
Baran, Özgür Uğraş
Aksel, Mehmet Halûk

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Throughflow calculations play an important role in the design stages of a turbomachinery. After the one-dimensional mean line calculations have been completed, the throughflow solver used in the design mode to perform the blade hub to shroud analysis can also be activated in the analysis mode to perform the off-design analysis. The original MULTALL code applies a uniform friction coefficient (Cf) to all wet surfaces in the turbomachinery passage and uses this Cf to calculate wall friction and hence loss. Although this approach is more physical than the source term approach, it does not capture certain physical phenomena in the turbomachinery passage. In the previous step of this study, the MULTALL code is modified to give a more realistic end wall loss distribution [18]. In this study, the code is further modified to perform off-design analysis and is given the capability to perform off-design analysis. Just as the constant Cf imposed in the design condition gives an unphysical loss distribution along the blade, it also gives inaccurate results for off-design. Since different angles of incidence and mass flows in off-design conditions will result in different loss distributions, the constant Cf must be adjusted according to the changing conditions. Considering a classical compressor or turbine performance curve, the angles of incidence change as the mass flow changes, and the losses increase according to the design condition. In addition, the shock losses also increase at high mass flow rates ("choked region" on the performance map). Therefore, to calculate an accurate loss prediction in off-design conditions, the Cf distribution used in the design condition should be modified due to diffusion effect, incidence and shock losses. In this paper we present parts of the MULTALL solver modified for off-design analysis and validate the results obtained with two compressor test cases. The results show the absolute improvement, especially towards the stall point.

Subject Keywords

Choke, Compressor, Incidence Loss, Loss, MULTALL, S1 Surface, S2 Surface, Stall, Throughflow

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https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85204678556&origin=inward
https://hdl.handle.net/11511/111746

Collections

Department of Mechanical Engineering, Conference / Seminar