MARSFT: Efficient fitting of CARS spectra using a library‐based genetic algorithm

A loss‐less compressed library scheme is presented in this publication that allows for computationally efficient fitting of coherent anti‐Stokes Raman spectra with no restriction to the number of degrees of freedom for the spectral fit. The compression is achieved by convolving the squared modulus and the real part of the complex susceptibility with a Gaussian kernel narrower than the experimental apparatus function. This effectively reduces library size while allowing to convolve to the final experimental linewidth during the fit. For the optimization procedure, a gradient‐free mixed‐integer genetic algorithm was implemented due to its ability to extract library spectra without interpolation. We demonstrate the ability of the code by comparing it to CARSFT in terms of dependency on starting solution, computational cost and accuracy using simulated spectra with varying noise contribution

MARSFT: Efficient fitting of CARS spectra using a library-based genetic algorithm

Abstract A loss-less compressed library scheme is presented in this publication that allows for computationally efficient fitting of coherent anti-Stokes Raman spectra with no restriction to the number of degrees of freedom for the spectral fit. The compression is achieved by convolving the squared modulus and the real part of the complex susceptibility with a Gaussian kernel narrower than the experimental apparatus function. This effectively reduces library size while allowing to convolve to the final experimental linewidth during the fit. For the optimization procedure, a gradient-free mixed-integer genetic algorithm was implemented due to its ability to extract library spectra without interpolation. We demonstrate the ability of the code by comparing it to CARSFT in terms of dependency on starting solution, computational cost and accuracy using simulated spectra with varying noise contribution

Experimental Investigation of Global Combustion Characteristics in an Effusion Cooled Single Sector Model Gas Turbine Combustor

This paper presents experimental investigations in an effusion cooled single sector gas turbine combustor under close-to-reality boundary conditions, i.e. elevated pressure and combustor inlet temperature, under varying staging conditions. Flow field, flame structure and gas-phase temperature measurements are performed using particle image velocimetry (PIV), planar laser induced fluorescence of the hydroxyl radical (OH-PLIF) and coherent anti-Stokes Raman scattering (CARS), respectively. Additionally, isothermal mixing of the pilot and main stage is investigated using Acetone-PLIF. The influence of the pilot on the measured quantities can be identified up to 30 mm downstream of the burner head plate. These measurements are conducted within a novel test rig dedicated to the investigation of swirl-stabilized pressurized flames and effusion-cooling. The rig features full optical access for non-intrusive laser diagnostics from three sides and a modular effusion liner geometry. Important process parameters can be controlled independently in a wide range, providing a high versatility and reliability in terms of boundary conditions. Oxidizer and cooling air mass flows can be conditioned independently to 773 K and 973 K, respectively. Fuel staging can be gradually varied between 0% (fully premixed) and 100% (pilot only) at thermal loads up to 150 kW and a maximum pressure of 1,0 MPa. A movable block radial swirler allows for varying geometrical swirl numbers