A two‐dimensional numerical model is developed to simulate nonisothermal performance of molten carbonate fuel cells. The model takes account of gas stream utilization due to electrochemical reaction, conductive heat transfer between cell hardware and gas streams, energy transfer accompanying mass addition to the bulk streams, convective heat transfer by the bulk streams, and inplane heat conduction through the cell hardware. Individual porous electrode models are used to predict the local dependence of current density on cell temperature and gas composition. Calculated results are compared with experimental data for 94 cm2 isothermal cells with crossflow geometry for various fuel and oxidant compositions, total gas pressures, and cell temperatures. Excellent agreement is obtained. Calculated distributions of current density and cell temperature are also presented for 1 m2 nonisothermal cells for cross‐, co‐, and counterflow geometries. Current density and cell temperature distributions are found to be highly coupled. Calculated temperature differences on the order of 200 K are observed across the face of a cell operating at maximum load.
Recuperators increase system efficiencies in gas turbine engines by recovering exhaust heat to the compressor discharge stream. In this study, the performance and economics of recuperation are evaluated and presented for a practical range of effectiveness with typical pressure-loss-fractions. The strong correlation between recuperator cost and engine specific-power is shown, using a recuperator designed and manufactured at a highly automated facility by Ingersoll-Rand. This commercially available recuperator is also described, with specific emphasis on features contributing to its exceptional durability.
The Inter-Cooled-Recuperated (ICR) cycle is recognized for its high efficiency potential in gas-turbine applications. This paper reports on a proposed implementation of the ICR cycle in a microturbine setting, using a three-spool configuration incorporating a variable-geometry nozzle on the low-pressure ‘free’ power turbine. Hardware specified for the high-pressure turbine is an existing ceramic rotor fabricated and spin-tested in connection with a prior DOE-sponsored program. Rated engine design-point power and efficiency are projected at 378kWe and 39.5% (net LHV), under realistic prescriptions for component efficiencies and parasitic losses, and with TIT = 1366K (2000°F) specified for the ceramic rotor. Detailed off-design performance projections are carried out, demonstrating exceptional range and part-load efficiency. A key attraction of the ICR compared to a non-intercooled recuperated cycle is its compatibility with high cycle pressure ratio, making for dramatic size and cost reductions for high-pressure components, most importantly the recuperator. A related advantage is reduced ceramic-turbine rotor diameter for a given power level, extending the applicability of ceramic components under conservative manufacturability limits. Engine layout and preliminary mechanical designs for the major subassemblies are developed for application to a forty-foot transport bus with hybrid-electric drive. Further applications under evaluation for the proposed microturbine are stationary power generation, and in a hybrid powerplant setting using a solid-oxide fuel cell.
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