Abstract
Research on concentrated solar power (CSP) plants has been increasing in recent years. Supercritical carbon dioxide (S-CO2) has been applied to solar power plants due to its promising physical properties. S-CO2 has a relatively low critical temperature of 31.1 °C and owns high density in the supercritical region. Hence, it is a vital working fluid in the application of low temperature heat source and miniature power equipment. Due to the fact that solar power system has a constantly changing heat source according to season and weather, a satisfactory off-design performance is necessary for the turbine in a solar power system. In this work, a S-CO2 radial-inflow turbine based on CSP is designed. A thorough numerical analysis of the turbine is then performed. To investigate the off-design performance of this turbine, three types of nozzle profiles with different leading edge diameters are adopted. Mach number, temperature and pressure distribution are covered to present the off-design effect with different nozzle profiles. Moreover, the relation of output power, mass flow rate and efficiency with different leading edge diameter (LED) are analyzed. Results show that different LED has a vital influence on the aerodynamic characteristics and off-design performance of the S-CO2 turbine based on CSP. In addition, the designed turbine with LED = 4 mm can obtain the highest mass flow rate and output power. While the turbine with LED = 10 mm provides slightly better off-design efficiency for CSP plants.
Highlights
Supercritical carbon dioxide (S-CO2 ) has a low critical temperature
Its critical condition is easy to reach due to the low critical temperature and it is in favor of the environment
Three types of nozzle profiles with different leading edge diameter (LED) are adopted in a turbine used in concentrated solar power (CSP)
Summary
Supercritical carbon dioxide (S-CO2 ) has a low critical temperature. its critical temperature is 304.2 K while its critical pressure is 7.38 MPa [1]. As a working fluid in radial-inflow turbine, S-CO2 has many advantages. The most useful merits of S-CO2 lie in its high density and low viscosity, which result in high efficiency and compact mechanical structure in the radial-inflow turbine [3,4]. In the last 5 years, the investigations on S-CO2 Brayton cycle and S-CO2 solar Rankine cycle have been covered [5,6,7] Due to all these advantages, the S-CO2 power cycle has been considered as the most popular and attractive competitor in concentrated solar power (CSP), coal power system, and bottoming cycle of fuel cells [8,9,10]. Radial turbines and centrifugal compressors with compact mechanical structure and complex geometries have been designed [11]
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