Spray and flame characteristics of an ultra-compact combustor for gas turbines

Ultra-compact combustors have received much attention in the development of gas turbines for transportation because of their advantages of compactness, low emissions, and cost. There is an urgent need for a more detailed investigation of the fuel arrangement, ignition process, and flame characteristics in the near-wall region. This study experimentally investigated the effects of the first nozzle position closest to the cavity/mainstream interface on the spray and flame characteristics in an ultra-compact combustor based on a radial flame stabilizer and a circumferential cavity. On this basis, four different nozzle positions were designed. Detailed experimental studies on the fuel injection position of the near-circumferential stabilizer concerning the fuel jet trajectory, droplet size distribution, lean light-off (LLO)/lean blow-out (LBO) limit, ignition process, and flame distribution characteristics were carried out via a CCD camera, a high-speed camera, and a laser particle sizer. Compared with the injection position farthest from the cavity, within the experimental range, the fuel injection position closest to the cavity increased the maximum jet penetration depth by 58 %, increased the average SMD by 127 %, and decreased the FAR of LLO by 76 %. On the basis of the obtained fuel droplet particle size distribution and flame kernel propagation path, a correlation analysis of the fuel droplet motion path, flow field characteristics, and flame kernel propagation path was carried out. The mechanism of the influence of different nozzle positions on the fuel distribution and ignition process was revealed. In addition, the closer the fuel nozzle was, the more uniformly the flame was distributed in the circumferential direction, which could effectively improve the combustor compactness, but simultaneously produce the problem of high wall temperature.