Abstract
Transient thermal-hydraulic analysis of (very) high temperature gas-cooled reactors gas turbine systems (HTRGTSs) needs system transient analysis codes. However, compared with the mature system transient thermal-hydraulic codes of pressurized water reactors (PWRs), the system analysis codes of HTRGTSs are not so fully developed. In this paper, a new hybrid semi-implicit (HSI) method is proposed based on the semi-implicit method and nearly-implicit method. In the HIS method, a new calculation strategy is devised: the convective term in treated explicitly to solve pressure and velocity, while density and temperature are solved in an implicit manner to get a convergent, stable and accurate solution in multiple transient scenarios. The HSI method was further validated via the shock-tube benchmark problem and verified via FLUENT simulations. In FLUENT simulations, outlet pressure transient, inlet mass flow transient and inlet temperature transients were studied. It was found that the HSI method is capable of capturing both the fast and slow compressible flow transients with good convergence and stability. Furthermore, an adaptive time step scheme is proposed for faster calculation, considering the maximum relative density difference and CFL condition.
Highlights
High temperature gas-cooled reactors gas turbine system (HTRGTS) is inherently safe and highly efficient with a reactor outlet temperature of 700∼1,000◦C
Different from pressurized water reactors (PWRs), HTRGTS uses helium as its working fluid, whose density strongly couples with pressure and temperature
The hybrid semi-implicit (HSI) method was verified via the shock tube benchmark problem, and furtherly compared with FLUENT simulations
Summary
High temperature gas-cooled reactors gas turbine system (HTRGTS) is inherently safe and highly efficient with a reactor outlet temperature of 700∼1,000◦C. HTRGTS uses a Brayton cycle, which includes a reactor, one or two compressors, turbine, recuperator, precooler, and intercooler. The working medium is usually helium in the HTRGTS because of its chemical inertia. The helium in the Brayton cycle is compressed to very high pressure (e.g., 7 MPa) in compressors and furtherly heated through the reactor, and expands to very low pressure (e.g., 2.7 MPa) to generate kinetic energy in the turbine
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