Authors: R. Laubscher, P. Rousseau, J. van der Spuy, C. du Sart, J. Pretorius
Year: 2024
Industry: SCO2
Keywords: Mention FSE, Validation, Comparison
ABSTRACT
A novel compressible real gas 1D finite volume thermofluid network modelling methodology is proposed that can be applied in the analysis of compressors for supercritical CO2 (sCO2) power cycles. It utilizes a unique formulation of the momentum balance equation introducing the concept of isentropic density and pseudo advection terms to account for the polytropic compression path shape within a single increment. It is applied to simulate centrifugal compressor performance via a mean line approach along with the associated loss models, component characteristics, and applicable compressible real gas equation of state. The methodology is demonstrated via application to well-documented cases of air and sCO2 centrifugal compressors. It is also compared with the conventional incompressible and compressible ideal gas thermofluid network approaches, as well as the traditional mechanical energy balance method. The new approach accurately captures the pressure changes with only a single increment per compressor component, while the traditional mechanical energy balance method requires discretization through the compression process to correctly capture the polytropic compression path shape. Without discretization the error in the pressure ratios predicted with the traditional approach are around 2 % at design conditions and as much as 6 % at higher rotational speeds, whereas the results of the new compressible real gas approach are within 1.0–1.2 % of the experimental data for both case study compressors over a wide range of mass flow rates and shaft rotational speeds.