59228 - Preliminarily Design of Supercritical Carbon Dioxide Compression Test System 

The compressor is the core component of the supercritical CO₂ (SCO₂) power cycle. It is essential to carry out component-level experimental research on it and test the working characteristics of the compressor and its auxiliary equipment. Building an accurate closed-loop simulation model of closed SCO₂ compression loop is a necessary preparation for selecting loop key parameters and establishing system control strategy, which is also an important prerequisite for the stable operation of compressor under test parameters. In this paper, the thermodynamic model of compressor, cooler, throttle valve and other components in supercritical CO₂ compression test system is studied, and the simulation model of compression test system is established. The compressor is calculated based on the traditional one-dimensional loss model, and the cooler is analyzed by the counter flow ε-NTU method. The predicted results of the model are compared with the experimental data of Sandia National Laboratory. According to the comparison, the accuracy of the thermodynamic model is verified. Moreover, the traditional component design method is mainly based on the ideal gas model and adopts the assumption of fixed specific heat, so it can't be used in the component design of SCO₂ compression test system. Therefore, based on the system enthalpy method, the compressor, cooler and other components in the test loop are preliminarily designed by using the thermodynamic model of components and the physical property model of real gas. The compressor in this loop is designed to operate at 50,000 rpm with a pressure ratio of 2. 0, a power of 350kW, an efficiency of 0.7, and a mass flow rate of 12 kg/s. The inlet temperature of compressor is 308k and the inlet pressure is 7.8MPa. Since the operating conditions are in the vicinity of the critical point, when the operating conditions change, the physical properties of the working fluid will change significantly, which will have a greater impact on the operating performance of the system. So the operating performance and the parameter changes of key nodes in the test loop under different operating conditions are calculated, which will provide theoretical guidance for the construction of subsequent experimental loops.