No abstract

Evaporative cooling effects and turbulence flame interaction are analyzed in the large eddy simulation (LES) context for an ethanol turbulent spray flame. Investigations are conducted with the artificially thickened flame (ATF) approach coupled with an extension of the mixture adaptive thickening procedure to account for variations of enthalpy. Droplets are tracked in a Euler–Lagrangian framework, in which an evaporation model accounting for the inter-phase non-equilibrium is applied. The chemistry is tabulated following the flamelet generated manifold (FGM) method. Enthalpy variations are incorporated in the resulting FGM database in a universal fashion, which is not limited to the heat losses caused by evaporative cooling effects. The relevance of the evaporative cooling is evaluated with a typically applied setting for a flame surface wrinkling model. Using one of the resulting cases from the evaporative cooling analysis as a reference, the importance of the flame wrinkling modeling is studied. Besides its novelty, the completeness of the proposed modeling strategy allows a significant contribution to the understanding of the most relevant phenomena for the turbulent spray combustion modeling.

A highly linear dual ring resonator modulator (DRRM) design is demonstrated to provide high spur-free dynamic range (SFDR) in a wide operational bandwidth. Harmonic and intermodulation distortions are theoretically analyzed in a single ring resonator modulator (RRM) with Lorentzian-shape transfer function and a strategy is proposed to enhance modulator linearity for wide bandwidth applications by utilizing DRRM. Third order intermodulation distortion is suppressed in a frequency independent process with proper splitting ratio of optical and RF power and proper dc biasing of the ring resonators. Operational bandwidth limits of the DRRM are compared to the RRM showing the capability of the DRRM in providing higher SFDR in an unlimited operational bandwidth. DRRM bandwidth limitations are a result of the modulation index from each RRM and their resonance characteristics that limit the gain and noise figure of the microwave photonic link. The impact of the modulator on microwave photonic link figure of merits is analyzed and compared to RRM and Mach-Zehnder Interference (MZI) modulators. Considering ± 5 GHz operational bandwidth around the resonance frequency imposed by the modulation index requirement the DRRM is capable of a ~15 dB SFDR improvement (1 Hz instantaneous bandwidth) versus RRM and MZI.

No abstract

No abstract