High Power Density Silicon Combustion Systems for Micro Gas Turbine Engines

As part of an effort to develop a micro-scale gas turbine engine for power generation and micro-propulsion applications, this paper presents the design, fabrication, experimental testing, and modeling of the combustion system. Two radial inflow combustor designs were examined; a single-zone arrangement and a primary and dilution-zone configuration. Both combustors were micro-machined from silicon using Deep Reactive Ion Etching (DRIE) and aligned fusion wafer bonding. Hydrogen-air and hydrocarbon-air combustion was stabilized in both devices, each with chamber volumes of 191 mm3. Exit gas temperatures as high as 1800 K and power densities in excess of 1100 MW/m3 were achieved. For the same equivalence ratio and overall efficiency, the dual-zone combustor reached power densities nearly double that of the single-zone design. Because diagnostics in micro-scale devices are often highly intrusive, numerical simulations were used to gain insight into the fluid and combustion physics. Unlike large-scale combustors, the performance of the micro-combustors was found to be more severely limited by heat transfer and chemical kinetics constraints. Important design trades are identified and recommendations for micro-combustor design are presented.