Master of Science in Mechanical Engineering (MSME)


Mechanical Engineering

Document Type



An array of four fuel injector nozzles, each with micrometer-scale swirlers and a microhole, is created on a single coupon. The nozzles are intended to atomize fuel to blend with swirling air before ejecting into a trapped-vortex combustion chamber. A first-generation metal prototype is fabricated in order to form the micro features, supply the fuel and gas to the nozzles, and guide the mixture to the combustion chamber. Microfabrication methods and precision machining are used to create a multiple plate laminate assembly. The central plate contains the four microholes, which atomize the fuel, and facilitate the swirler structures needed to induce vorticity in the fuel and air. Fabrication of the swirlers requires electrodeposited nickel microstructures on both sides of the plate in order to segregate the high-pressurize air and fuel flows. Two other plates seal the air and fuel channels resulting in separate reservoirs for supply to the microstructures. A fourth plate defines a low-pressure complementary air reservoir needed for stoichiometric conditions. Guided with alignment pins, the plates fasten together to seal the reservoirs and guide the injecting mixture along an axis with a total alignment error of less than 50 µm. Precision machining is needed to drill the holes required for alignment, fluid flow, and fasteners. Plunge EDM drilling through a thin plate creates the conically-shaped holes 75 µm -125 µm in diameter. The project resulted in fully reproducible microfabrication methods, which when used in coordination with precision machining techniques produces smooth, level microstructures on both sides of the drilled nickel plate. The components were assembled and tested for leakage. Since the prototype leaked below atmospheric pressure, the warped central plate could not be salvaged for patterned flow testing purposes. Recommendations for the next generation prototype are presented. Preliminary investigation of a ceramic prototype is conducted with particular interest in sealing solutions involving cofired test samples. Viable testing methods and specimen geometry are investigated. Future ceramic prototype development requires shear joint testing as the initial step in realizing a self-sealing ceramic fuel injector prototype.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Michael C. Murphy