Turbulent mixing in an accelerated nozzle flow

To analyze the procedure of gasdynamically generating nanoparticles, the turbulent mixing of the heavy gas tetraethoxysilane (TEOS - Si(C2H50)4Si(C2H50)4) in a hot accelerated transonic air co-flow is numerically investigated. The precursor gas TEOS is premixed with nitrogen and then ejected through circular holes in the base of an injector into the subsonic region of a nozzle flow at a co-flow Mach number of Maco-flow≈0.66Maco-flow≈0.66 and a temperature of Tco-flow≈1200K. A multi-species large-eddy simulation (LES) capturing the most energetic turbulent scales is used to simulate the mixing process. Close behind the blunt trailing edge of the injector the results show the mixing to be dominated by pronounced free shear layers. Downstream of the injector the flow field is accelerated to supersonic speed and dominated by trailing vortices, which transport the partially mixed precursor gas but do not enhance further mixing. The analysis of the simulation results indicates that no further mixing occurs approximately 16 trailing edge thicknesses downstream of the trailing edge.