Concentration and Temperature Tomography at Elevated Pressures

Computer simulations are used to introduce a new approach to measure temperature fields of a gas using laser attenuation measurements, which exhibits good theoretical accuracy despite very high static pressures. Near-infrared laser light is used to target specific molecular absorption lines of water vapor, whose strength depends (nonlinearly) on the gas temperature. This temperature can be inferred when multiple laser paths coincide nearby by tomographic reconstruction of the attenuation coefficient and then spectral fitting to local temperature, species concentration, and gas pressure. Temperature phantoms (invented distributions for the purpose of numerical testing) are used to simulate experimental results, which are then contaminated with Gaussian noise and used to reconstruct the temperature field. The root-mean-square reconstruction temperature error varied from similar to 0.4%, in no Gaussian noise and at 1 bar, to 2.2%, in 5% noise and at 50 bar.