13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
The paper aims to give an understanding on an effect, which stabilizes the inlet conditions of compressors for supercritical CO2 (sCO2) operating close to the critical point. The effect was observed during testing of the turbomachine within the sCO2-HeRo project and is caused by the sCO2 real gas properties close to the pseudocritical line. Under theoretical consideration strong gradients in the fluid properties around this line dependent on static temperature and pressure of sCO2 can result in strong variation of compressor performance and finally lead to unstable cycle behavior. However, the paper demonstrates reduced gradients in density at the compressor inlet when varying the cooling power and taking advantage of a stabilizing effect. The applicable range and the significance of this stabilizing effect depends on the cooler inlet temperature and pressure and is used to evaluate the relevance for individual cycles. Concluding, the control of the cooling power and the measurement of the inlet density allows to control the compressor inlet conditions equally good independent of the operating point, even close to the critical point.