EFFECTS OF IGNITION POSITION AND INLET PRESSURE ON IGNITION PERFORMANCES OF A CENTRALLY STAGED COMBUSTOR

For a centrally staged swirl combustion chamber, ignition performance is a critical issue. Because of the significant influence of the main stage airflow located in the outer layer of the dome, fuel droplets are not easily transported to the tip of the igniter. Also, the outer air layer exerts a strong convective effect on the flame core. In this paper, we mainly explore the ignition performance of the centrally staged combustor under ambient temperature and low-pressure conditions. The effects of different spark axial positions on the ignition characteristics were experimentally investigated in the range of 30.8-70.3 kPa inlet pressure of the combustion chamber. The results of ignition fuel air ratio under different combustion chamber air pressure drop conditions were obtained. The results show that the trend of ignition fuel air ratio with pressure drop is different under different inlet pressure conditions. When the inlet pressure was 35.7KPa and 30.8KPa, the ignition fuel air ratio increased with the pressure drop, while the trend became opposite when the inlet pressure increased to 70.1Kpa near atmospheric pressure. For the ignition position, when the igniter is located at different positions in the recirculation zone of the combustion chamber, it will directly affect the ignition fuel air ratio and even determine whether the ignition can be successful. The results showed that the best ignition performance was achieved when the igniter was located at 57.6 mm from the combustion chamber sleeve. In addition, CFD analysis was performed. The differences in ignition boundaries were further explained by analyzing the flow field and the propagation path of the ignition kernal. From the analysis results of numerical simulation, it can be concluded that when the ignition position is located in the middle of the edge of the recirculation zone, the flame propagation time to the dome of the combustion chamber can be shortened and thus a better ignition boundary can be obtained.