NUMERICAL SIMULATION OF NON-STATIONARY PROCESSES IN THE GAS TURBINE CIRCUIT OF THE SSTAR LEAD-COOLED REACTOR

The problem of mathematical and numerical modeling of non-stationary processes in a closed gas turbine installation as part of an energy conversion unit of a lead-cooled reactor is considered. The problem is solved in a fairly General formulation, in which the gas circuit can include an arbitrary number of turbines with gas preheating, an arbitrary number of compressors with gas pre-cooling, as well as a heat exchanger for regenerative gas heating. Variants of both single-shaft and two-shaft gas turbine installations are considered. Point idealization is used when modeling the flow part of the turbine and compressor. Heat and mass transfer in the circuits of lead and gas coolants is described in a one-dimensional approximation. The possibility of mutual phase transformations of a melt-solid phase in the lead coolant is taken into account. Calculation of heat and mass transfer in the circuits is carried out within the single approach, in which the circulation circuit is represented as a set of interconnected heat-hydraulic elements (channels). Integration of the system of heat and mass transfer equations in the contour is performed using a fast scalar sweeping algorithm. The calculation algorithm provides the ability to take into account the sources of impulse and mass at arbitrary nodal points of the contour. This makes it possible to “end-to-end” computation when integrating the system of equations of gas dynamics along a closed loop, taking into account changes in adiabatic pressure drops at the points of turbines and compressors at each time step. The possibility of using the integral form of the momentum equation for modeling heat and mass transfer in a gas circuit is considered. For the SSTAR-type reactor with a lead coolant and a gas-turbine energy conversion cycle, the calculation of an emergency process with a rupture of a hot gas pipeline was performed. It was found that, in contrast to a reactor with a steam-turbine cycle of energy conversion of the BREST type, lead solidification in gas heaters does not occur in this accident. The study results can be used in elaborating the designs of lead cooled reactors and high-temperature gas reactors.

Experimental studies into the dependences of the axial lead coolant circulation pump performance on the pump straightening device parameters

The paper presents the results of experimental studies into the dependences of the axial pump performance (delivery rate, head, efficiency) in lead coolant on the parameters of the straightening device (SD) installed downstream of the impeller (the SD inlet flow angle and the number of the SD blades with a variable impeller speed change). The studies were performed as applied to the operating conditions of small and medium plants with lead cooled fast neutron reactors with horizontal steam generators (BRS GPG). The designs of such plants are being matured at Nizhny Novgorod State Technical University (NNSTU). The experiments were conducted on the FT-4 NGTU test bench at the lead coolant temperatures in a range of 440 to 500 °C. The number of the test blades was five and eight, and the SD inlet flow angle was 22, 24, 28, and 32°. The tests were also performed without an SD (with the SD dismantled). The shaft speed of the NSO-01 NGTU pump, with changeable SDs installed into its rotating assembly, was varied in a range of 600 to 1100 rev/min with a step of 100 rev/min. The SD sleeve diameter was 82 mm, the SD blade diameter and height were 213 mm and 80 mm respectively, and the maximum lead coolant flow rate during the studies was up to ~ 1650 t/h. The NSO-01 NGTU pump performance was determined with four changeable straightening devices and with no SD, the pump shaft speed being 600 to 1100 rev/min, as the circulation circuit hydraulic resistance changed owing to the movement of the wedge in the valve installed in it. The tests were performed with the impeller designed and supplied by NNSTU (D = 213 mm, dsl = 82 mm, the blade number is four, and the blade angle is 28°). The obtained results are recommended for use to design axial heavy liquid metal coolant pumps.