Compressor off-design performance prediction method with similitude analysis for supercritical $CO_2$(S-$CO_2$) cooled nuclear reactor

Abstract

Most of nuclear power plants have been utilized to serve as a baseload power source and had large capacity. On the other hand, nowadays the demand for distributed power source is increasing. As a response to this market trend, the concept of small modular reactor was proposed. Conventionally, large scale nuclear power plants have adopted a steam Rankine cycle. However, due to its nature, the size of component is large, and so is the system size. A new small modular reactor has been proposed namely KAIST-MMR. KAIST-MMR utilizes a supercritical $CO_2$ (S-$CO_2$) Brayton cycle as a power conversion system. This cycle has compact turbomachinery derived from gas turbine technology while compression work is minimized to give good efficiency. However, the noble characteristics of S-$CO_2$ make it difficult to design and analyze compressors operating near the critical point. One of the particular issues is an off-design performance prediction of a compressor. To predict the performance of a compressor operating under off-design conditions, the models based on the similitude have been widely exploited, but most of them were developed for air condition and not thoroughly evaluated for S-$CO_2$. This gives the motivation to study and evaluate the off-design performance prediction model based on the similitude theory. In this thesis, the applicability of existing similitude models to an S-$CO_2$ compressor is first evaluated, and the modification of the existing model is performed and presented.