The ignition reliability of combustor is related to the safety of the whole machine, especially the high-altitude ignition and combustion stability, which are the common requirements of the combustor. In this paper, the simulated altitude test facility was introduced. And the ignition performances of a linear combustor with five burners were carried out under the simulated altitude of 0–8 km, including the ignition boundary and flame propagation between burners. The process of flame propagation was recorded by a high-speed camera. The results indicate that the fuel-air ratio increases with the increase of altitude at the same pressure drop, and it decreases with the increase of pressure drop. For the period of ignition delay, the evaporation of droplets and the chemical delay process are mainly affected with the increase of altitude. At the altitude of 6 km to 8 km, flame propagates from burner to burner in an axial pattern, and the influence of altitude on flame propagation is mainly manifested in ignition delay and initial flame propagation. The key to improve the reliability of high-altitude ignition is to improve the fuel atomization and evaporation characteristics. The contribution of this article is to explore the mechanism of altitude on ignition characteristics and propose two methods to improve the high-altitude ignition characteristics.

Prefilming air-blast atomizers are widely used in modern gas turbine combustors. Due to insufficient awareness of the coupling mechanism of multi-stage swirling flow in gas turbines, there is a lack of effective methods for flow field optimization in combustor. In this study, the effect of some critical parameters on the flow field of a prefilming air-blast atomizer was analyzed with CFD. The parameters include the angle and number of the first swirler blades, the angle of the second swirler blades and the angle of sleeve. Furthermore, the coupling mechanism of two-stage swirling airflows of prefilming air-blast atomizer was discussed. Moreover, the influence of the interaction between two-stage counter swirling airflows on the characteristics of flow field was explained. The results show that with the increase in SNi, the axial length of the primary recirculation zone decreased, while the radial width increased. The starting position of primary recirculation zone (PRZ) moves forward with the increase in SNo. Reducing the sleeve angle β helps to form the primary recirculation zone. The results indicate that it is the transition of tangential velocity of airflow to radial velocity that promotes the formation of the PRZ. These results provide theoretical support for optimization of the flow field in swirl combustor.