VANELESS DIFFUSER MODELLING FOR REAL GAS SUPERCRITICAL CARBON DIOXIDE FLOWS- NEED FOR A DATA DRIVEN APPROACH

Seshadri, L and Kumar, P (2024) VANELESS DIFFUSER MODELLING FOR REAL GAS SUPERCRITICAL CARBON DIOXIDE FLOWS- NEED FOR A DATA DRIVEN APPROACH. In: 69th ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, GT 2024, 24 June 2024through 28 June 2024, London.

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Abstract

In this work, a real gas-based Vaneless diffuser (VLD) differential equation model is presented. The model requires the specification of the skin friction coefficient as input. However, the use of standard VLD friction coefficient estimation expressions require a re-examination for sCO2 flows. To establish the skin friction coefficient for real gas sCO2 flows, CFD data is generated using Latin Hypercube Sampling (LHS), with boundary conditions spanning the typical operating conditions of sCO2 centrifugal compressors in the kW to MW scale of power generation. The CFD computations are carried out using ANSYS® CFX software. The corresponding VLD friction coefficient for which the VLD stagnation pressure loss predicted by the 1D differential equation model matches with the 3D CFD result is back calculated for all the LHS designs. This is carried out using a root finding function in MATLAB® software. The existing empirical relation that characterizes the VLD skin friction coefficient using the inlet Reynolds number alone shows a poor correlation (R2=0.26), when compared to the CFD data. It is evident that a data driven approach is required to model the sCO2 VLD real gas flow for accurate results. Using the LHS data, the efficacy of an Artificial Neural Network (ANN)-based VLD model is demonstrated. A two hidden layer ANN is developed, which accurately predicts the skin friction coefficient for sCO2 real gas flows (R2=0.87). This proposed ANN based VLD model can be easily integrated into existing 1D codes for real gas sCO2 centrifugal compressor rating and sizing. Copyright © 2024 by ASME.

Item Type:	Conference Paper
Publication:	Proceedings of the ASME Turbo Expo
Publisher:	American Society of Mechanical Engineers (ASME)
Additional Information:	The copyright for this article belongs to publisher.
Keywords:	Aerodynamics; Centrifugal compressors; Computational fluid dynamics; Diffusers (fluid); Diffusers (optical); Flow of gases; Gas compressors; Hydraulic turbines; MATLAB; Reynolds equation; Reynolds number; Wind turbines, Data-driven approach; Differential equation model; Latin hypercube sampling; Loss model; Neural-networks; Real gas; Skin friction coefficient; Supercritical carbon dioxide (sCO2); Supercritical carbondioxides; Vaneless diffuser, Skin friction
Department/Centre:	Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research Division of Mechanical Sciences > Mechanical Engineering
Date Deposited:	17 Oct 2024 04:32
Last Modified:	17 Oct 2024 04:32
URI:	http://eprints.iisc.ac.in/id/eprint/86341

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