| Under the conditions of high altitude,it is easy to cause the flaring event for the airflow instability induced by rain absorption,hail absorption,and intake air distortion.At these high altitudes,the air temperature and pressure are lower,and the atomization and evaporation of fuel is poor,which makes the ignition difficulty.At present,there are few studies on the high-altitude relight,and the mechanism of low-temperature and low-pressure on the combustor reignition is still unclear.Aiming at the above problems and research status,the influence of low temperature and pressure on the flow field,atomization field,ignition process and light-round process were investigated in the single-head burner and linear-arranged combustor with five burners,and the mechanism of low temperature and low pressure on them were revealed.It provides theoretical guidance for broadening the ignition boundary of combustor in high altitude.In this dissertation,firstly,the cold flow and the process of flame propagation of bluff-body burner were simulated and compared with the experimental results to verify the accuracy of the numerical simulation method.Then,the single-head burner and the linear-arranged combustor with five burners were taken as the research objects.And the influence of air velocity,low pressure and temperature on the ignition boundary,flame propagation and light-round process were investigated.Meanwhile,the flow field and the fuel distribution were used for analysis.In addition,the numerical simulation method is used to study the interaction between the flow field and flame propagation,and the flame propagation at various ignition positions.The main research contents and conclusions of this dissertation include:(1)The bluff-body burner was used to verify the accuracy of numerical simulation method.The result shows that the cold flow simulated by LES can capture smaller vortex structures in the flow process and can better fit to the experimental results.The RANS method has a certain practical value in simulating cold flow.The flame shape and the propagation path simulated by the DTF model are in good agreement with the experimental results.(2)The effects of air velocity,air pressure and temperature on the flow field was investigated in a single-head combustor,and the interaction of flow field between adjacent burners were investigated in a linear-arranged combustor with five burners.The results of single-burner show that the size and intensity of recirculation zone,and the turbulence intensity increase with the increase of air velocity.The decrease of air pressure and air temperature makes the width of the recirculation zone slightly decreases.The results of the flow field between adjacent burners show that the size of the recirculation zone in the middle burner becomes smaller with the increase of the airflow velocity.And the size of the recirculation zone in the middle burner increases with the decrease of air pressure.(3)The effects of air velocity,air pressure and temperature on the fuel distribution was investigated in a single-head combustor,and the interaction of fuel distribution between adjacent burners were investigated in a linear-arranged combustor with five burners.The results of single-burner show that the atomization quality of fuel can be improved for the increase of air velocity.Under the condition of low temperature and low pressure,the fuel concentration increases in the combustion chamber.Under the condition of low temperature,the penetration depth of fuel decreases for higher air density,so the fuel concentration in the combustion chamber increases.The results of the fuel distribution between adjacent burners show that the fuel atomization distribution width at the middle head decreases with the increase of air velocity,and it increases with the decrease of air pressure.(4)The effects of air velocity,inlet pressure,inlet temperature and fuel temperature on ignition performance and flame propagation were investigated in a single-head combustor.The results show that the ignition equivalent ratio decreases with the increasing of air velocity when the air pressure drop is lower than 3%.The flame propagation path of A is controlled by airflow velocity and fuel concentration,while the path of C is controlled by heat release and heat consumed by convection.The ignition equivalent ratio increases with the decrease of air pressure,and temperature of air and fuel.When the fuel atomization quality is good,the main limiting factor of the ignition equivalence ratio is the air pressure,and the main limiting factor of the ignition equivalence ratio is the fuel atomization quality when the fuel atomization quality is poor.Under the conditions with low temperature and low pressure,the flame tend to spread along the downstream area with higher fuel firstly,and then spreads to the upstream of combustor.In the process of flame propagation,the flame is mainly influenced by the flow field.The optimal ignition position is located at the middle of recirculation zone.(5)The effects of air velocity,air pressure and temperature on the ignition performance and light-round were investigated in a linear-arranged combustor with five burners.The results show that the minimum ignition equivalent ratio decreases with the increase of air velocity when the pressure drop is lower than 3%.And it increases with the decrease of air pressure and temperature.The effect of air pressure on ignition boundary is higher than that of air temperature.The ignition delay time increases with the increasing of airflow velocity and the decreasing of air temperature and pressure.The physical delay process is affected by the flow velocity,and the chemical delay process is more affected by the air temperature.Due to the difference of flow field and fuel distribution,there are two kinds of light-round paths,including radial propagation and axial propagation.The radial propagation is the more stable propagation mode. 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