Global sensitivity analysis of detailed chemical kinetic schemes for DME oxidation in premixed flames

Detailed chemical kinetic investigations on dimethylether oxidation in one-dimensional premixed flat flames were performed. Local and global sensitivities of the reaction rate constants within selected chemical kinetic schemes were studied using maximum flame temperature, and peak methane and formaldehyde concentrations as predictive target quantities. The global sensitivity analysis was based on the application of high dimensional model representations using quasi-random sampling. First- and second-order sensitivity indices of important reaction steps were determined for fuel rich (Φ = 1.49) and fuel lean (Φ = 0.67) conditions. Differences in the importance ranking for key reactions were found to exist between the selected schemes, highlighting the influence of differences in the key rate constants. Whilst the peak flame temperature was predicted with fairly low uncertainty by both schemes, significant uncertainties were identified in the prediction of the target minor species. Key reaction rates requiring better quantification in order to improve the prediction of methane and formaldehyde concentrations are identified

Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides

Fiber-chip edge couplers are extensively used in integrated optics for coupling of light between planar waveguide circuits and optical fibers. In this work, we report on a new fiber-chip edge coupler concept with large mode size for silicon photonic wire waveguides. The coupler allows direct coupling with conventional cleaved optical fibers with large mode size while circumventing the need for lensed fibers. The coupler is designed for 220 nm silicon-on-insulator (SOI) platform. It exhibits an overall coupling efficiency exceeding 90%, as independently confirmed by 3D Finite-Difference Time-Domain (FDTD) and fully vectorial 3D Eigenmode Expansion (EME) calc