SUPERCRITICAL CO_(2) TEST LOOP OPERATION AND FIRST TEST RESULTS

摘要

The DOE Office of Nuclear Energy is investigating advanced Brayton cycles for use with next generation nuclear power plants. The focus of this work is on the supercritical CO_(2) Brayton cycle which has the potential for high efficiency, and for reduced capital costs due to very compact turbomachinery. Sandia has fabricated and is operating a supercritical CO_(2) (SCO_(2)) test loop to investigate the key technology issues associated with this cycle. This loop is part of a multi-year phased development program to develop a megawatt (MW) class closed SCO_(2) Brayton cycle to demonstrate the applicability of this cycle for DOE Gen-IV program. The current loop has been configured as both a compression loop and as simple heated but un-recuperated Brayton cycle. A second split-flow or re-compression Brayton cycle is currently under development that will use approximately 1 MW of heat to run the Brayton cycle. Early configurations of this split-flow Brayton cycle will be operational later this fiscal year The key issues for this cycle include the fundamental issues of compressor fluid performance and system control near the critical point, but also the supporting technology issues of bearings, sealing technologies, and rotor windage losses which are also essential to achieving efficiency and cost objectives. These tests are providing the first measurements and information on these key supercritical CO_(2) power conversion systems questions. Important data for all these issues has been obtained. This report presents the major results of the testing by showing and comparing the measured compressor performance map with the predicted performance. The compression loop uses a approx50 kWe motor driven compressor to spin a 37 mm OD compressor at design speeds up to 75,000 rpm with a pressure ratio of 1.8 and a flow rate of 3.53 kg/s for a compressor inlet condition of 305.3 K and 7690 kPa. The most recent configuration of this loop has added a small turbine and 260 kW of heater power is the first operations of this S-CO_(2) Brayton cycle to be operated. The turbo-alternator-compressor has reached speeds of 65,000 rpm, a pressure ratio of 1.65 and mass flow rates of 4.0 kg/s with fluid densities that vary from 0.14 kg/s to 0.7 kg/l. At the current operating speeds and pressures, the observed performance map data agrees extremely well with the model predictions. These results have positive implications for the ultimate success of the S-CO_(2) cycle. The main compressor shows no adverse behavior while operating over a wide range of conditions. It operates reliably and with performance values that are very near the predicted results. Future efforts will focus on operating the Brayton cycle loop with the goal of producing power near the end of this year.