Capabilities and limitations of 3D flame measurements based on computed tomography of chemiluminescence

This work investigated the fundamental capabilities and limitations of three-dimensional (3D) combustion measurements based on computed tomography of chemiluminescence (CTC). Experimental, computational, and analytical studies were conducted to map out the fundamental relationship of several parameters important to 3D measurements, including the achievable spatial resolution, the dimension of the measurement volume, and the signal level. The spatial resolution was analyzed both from the Fourier Slice Theorem (FST) and from linear algebraic (LA) considerations, and two limits (the FST and LA limits) were obtained to predict the achievable spatial resolution in tomographic measurements. The achievable signal level and measurement volume were also analyzed under different conditions. These results suggest that it is advantageous to implement tomographic diagnostic such that the projection image fills the camera chip completely. Under such an implementation, the average signal level increases linearly with respect to the size of the measurement volume, and the spatial resolution under the LA limits degrades linearly with respect to the measurement volume if the chemiluminescence emission intensity remains constant. We expect these results to be valuable not only for CTC, but also for tomography diagnostics based on other types of signals because the mathematical formulation in this work is not specific to chemiluminescence signals.