Heat release rate of the swirl flames is an important parameter for the gas turbine state. It plays an essential role in the study of combustion characteristics, combustion efficiency and chamber protection. Several swirling CH4/air diffusion flames were investigated in a gas turbine model combustor via the spatial flame mode transition. In the combustion mode transition, we utilized three-dimensional computed tomography of chemiluminescence (3D-CTC) technique due to the complexity of swirling combustion flow field. The 3D emissions of CH* were measured and taken as qualitative indicators of the heat release rate under three Reynolds number conditions. This 3D measurement method utilizes 8 multi-directional CH* images as inputs combined with tomographic algorithms to compute the 3D distribution of CH* intensities. In this study, the transitions of heat release area with Reynolds number were analyzed, and the results show that the heat release rate changing more obviously along the nozzle radial direction than the axis direction, and the largest heat release area moves forward significantly.
Instantaneous measurement of flame spatial structure has been long desired for complicated combustion condition (gas turbine, ramjet et.). Three dimensional computed tomography of chemiluminescence (3D-CTC) is a potential testing technology for its simplicity, low cost, high temporal and spatial resolution. In most former studies, multi-lens and multi-CCD are used to capture projects from different view angles. In order to improve adaptability, only one CCD was utilized to build 3D-CTC system combined with customized fiber-based endoscopes (FBEs). It makes this technique more economic and simple. Validate experiments were made using 10 small CH4 diffusion flame arranging in a ring structure. Based on one instantaneous image, computed tomography can be conducted using Algebraic Reconstruction Technique (ART) algorithm. The reconstructed results, including the flame number, ring shape of the flames, the inner and outer diameter of ring, all well match the physical structure. It indicates that 3D combustion chemiluminescence could be well reconstructed using single camera.