Evaluation of off-design scaling methods of supercritical CO2 compressor with experimental data

Abstract

A compressor off-design performance prediction is one of the issues related to load following operation of the S–CO2 cycle. Normally, a compressor performance map produced at the design conditions is used to predict off-design performance under specific inlet temperature and pressure conditions, and that has been the case for an air compressor. The variation of temperature and pressure from the design conditions can be corrected easily for the measured mass flow rate and rotational speed when using the compressor performance map produced at the design conditions for air. In contrast, the validity of the similitude model for an S–CO2 compressor is not confirmed experimentally previously. Since S–CO2 have been repeatedly reported to have strong real gas effect, the most appropriate similitude model is yet to be determined. Using the selected data from existing S–CO2 test facilities, various similitude models are compared and the validity is checked. The results show that most similitude models predict better with enthalpy rise rather than pressure ratio for the S–CO2 compressor's off-design performance predictions. Among the compared models, ideal gas model based compressibility modified (IGZ) model for predicting enthalpy rise of the compressor at different inlet conditions showed the best prediction within the tested data.