From jet fuel to electric power using a mesoscale, efficient Stirling cycle

An approach to mesoscale electric power production is presented which relies on a clean and efficient combustor coupled with a free-piston Stirling engine. The design and development of a catalytic combustor is discussed, whose main components are: a multiplexed electrospray to disperse jet propulsion fuel (JP-8), a stack of catalytically coated grids through which fuel conversion and heat release is achieved cleanly and efficiently, and a recuperator to improve the system thermodynamic efficiency. The combustor/recuperator unit has a volume of 400 cm and operates at a JP-8 flow rate on the order of tens of g/h, and equivalence ratios varying in the 0.35–0.70 range. The combustor is interfaced with a free-piston Stirling engine to achieve 42.5 We of power generation with a gross fuel–electric efficiency of 22%. With design optimization and the use of off-the-shelf auxiliary components (pump, blower, igniter, start-up battery, etc.), 21% efficiency net of parasitic losses is achievable in a unit with a volume of 2.61 and a mass of 1.7 kg (excluding fuel tank) and with a gravimetric energy density on the order of 1000–2000 W h/kg (3.6–7.2 MJ/kg), depending on fuel autonomy, that is, one order of magnitude larger than conventional batteries. 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.