Effects of Swirl Cup Structure and Inlet Parameters on Combustion Characteristics

In order to optimize the head structure of swirl combustor and improve its performance, the experimental study on the performance of methane-fueled combustor under normal pressure was conducted based on the three combined structures of swirler venturi tube and fuel nozzle, as well as two swirlers with different flow areas. The experimental results show that the cold total pressure loss coefficient of each head structure is proportional to the square of inlet airflow velocity. The flow resistance becomes larger when the position of the fuel nozzle inserted into venture is either too deep or too shallow. In the case of the inflow velocity of 9.7m/s and intermediate insertion length, the total pressure loss coefficient decreases by approximately 6%. Under unconfined condition, the shallower the position of fuel nozzle is, the better the flame stability will be. However, this effect on flame stability would be reduced upon confinement, and the stable working range of the restricted flame is obviously wider than that of the open flame under the same inlet condition. Increasing the swirler flow area would be beneficial to reduce the total pressure loss coefficient, enhance the flame stability and relieve the vibration amplitude of the flame cylinder wall, but it is not conducive to promoting the mixing of fuel and air, resulting in higher emission concentrations of NO and CO. When the combustor operates near lean flameout, the vibration amplitude of the wall increases, which is enormously higher than that of stable flame with rich fuel. © 2020, Editorial Department of Journal of Propulsion Technology. All right reserved.