High Power Density Silicon Combustion Systems for Micro Gas Turbine Engines

As part of an effort to develop a microscale gas turbine engine for power generation and micropropulsion 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 micromachined from silicon using deep reactive ion etching (DRIE) and aligned fusion wafer bonding. Hydrogen-air and hydrocarbon-air combustion were stabilized in both devices, each with chamber volumes of $191mm3.$ Exit gas temperatures as high as 1800 K and power densities in excess of $1100MW/m3$ 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 microscale 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 microcombustors was found to be more severely limited by heat transfer and chemical kinetics constraints. Important design trades are identified and recommendations for microcombustor design are presented.