Integrated Autothermal Reformer, Heat Exchanger and Solid Oxide Fuel Cell in Single-Stack for Aircraft Gas-Turbine Applications

To take advantage of carbon-neutral aviation fuels such as synthetic liquified natural gas, aircraft engines must increase their efficiency through novel approaches, such as hybrid electric gas-turbine/solid oxide fuel cells (GT/SOFCs). To date, most hydrocarbon-fueled SOFC stack designs utilize rigid architectures and independent pre-reformers that require complex manifolding and rigid sealing. To enable SOFCs to operate effectively and robustly within an aircraft GT engine flow path upstream of a combustor, our team is developing an innovative integrated SOFC stack with an inline autothermal reformer/heat exchanger (ATR/HX) to provide adequate operating conditions for high-power (W/cm 2 ) performance. The ATR/HX, integrated upstream of the stack, provides preheating of the cathode air through mildly exothermic reforming of the fuel with a bleed of combustor air and recycling of some anode exhaust. The exothermic ATR provides adequate heat to the cathode air to allow intermediate-temperature SOFCs, with either gadolinium-doped ceria (GDC) electrolytes or thin-film yttria-stabilized zirconia (YSZ) electrolytes, to operate on GT compressor outlet temperatures just above 400 °C. To enable rapid thermal response of the integrated ATR/HX/SOFC, the stack design eliminates rigid seals to mitigate the risks of SOFC failure due to thermomechanical stresses. This paper presents the design and preliminary testing of the integrated ATR/HX/SOFC under rapid heating conditions to suggest the potential for SOFCs for next generation hybrid-electric aircraft application. The ATR/HX/SOFC stack design is supported by 441 stainless steel plates with electrochemically etched, air-flow channels through the upstream HX and the SOFC cathode. The plates also include a pocket for the ATR, which consists of a woven metal-mesh with an Al 2 O 3 -washcoat supported Pt catalyst that can light off with CH 4 /bleed air/H 2 O inlet temperatures of 400 °C. The SOFC membrane electrode assembly (MEA), 10 cm*10 cm with 81 cm 2 active cathode area, rest within a frame that supports the MEA as well as a silver mesh cathode collector and a nickel mesh anode current collector. The cell is sealed by compressing a thermiculite seal that extends over the full area of the stack and compresses on the exposed electrolyte area bordering the cathode. Testing at operating temperatures indicated minimal leakage (