Dynamic response of the supercritical C0₂ Brayton recompression cycle to various system transients
Author(s)
Trinh, Tri Q. (Tri Quang)
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Other Contributors
Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering.
Advisor
Pavel Hejzlar and Michael Driscoll.
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The supercritical carbon dioxide (SC0₂) power conversion system has been suggested for use with many of the Generation IV nuclear reactors. The SC0₂ cycle is highly attractive because of its low operating temperatures and high efficiency associated with working near the critical point of CO2. Unfortunately, the appealing features of using C0₂ near its critical point create complications in control. The Transient SC0₂ Cycles Code (TSCYCO) has been developed as a transient simulation control design and cycle scoping code for the recompression SC0₂ Brayton cycle. It is based off of the SC0₂ Power Systems (SCPS) code, and incorporates many improvements and modifications. Written in FORTRAN 90, TSCYCO uses a lumped parameter model and a momentum integral model approach. The code uses a semi-implicit solution process and implements Gaussian elimination to solve the system of equations. Transient behavior of the printed circuit heat exchangers is determined via the previously developed code HXMOD. Turbomachinery performance is modeled using the Real Gas Radial Compressor (RGRC) code with a scaling scheme for off-design conditions. Currently, TSCYCO has the capability of modeling several transients, including: loss of external load (LOEL), power load change, and cycle low-temperature change. Simulations show that TSCYCO can be run at quasi-steady state for an indefinite period of time. In the case of a 10% LOEL, the axial turbine experiences choke as a result of shaft overspeed. Turbine choke can be avoided if one bypasses more flow during LOEL. (cont.) Moreover, one can incorporate more accurate axial turbine performance models to account for shaft speed variation. TSCYCO experiences instabilities when operated too closely to the critical point of C0₂. This could be remedied with a more robust Runge-Kutta solution method.
Description
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009. Page 208 blank. Cataloged from PDF version of thesis. Includes bibliographical references (p. 159-160).
Date issued
2009Department
Massachusetts Institute of Technology. Department of Nuclear Science and EngineeringPublisher
Massachusetts Institute of Technology
Keywords
Nuclear Science and Engineering.