Abstract:In order to further understand the characteristics of civil turbofan which has a high Bypass-Ratio in off-design situations and the reasons for changes in performance parameters, a component-level simulation model of civil turbofan engine with a high Bypass-Ratio was established in this paper, then, the throttling characteristic, the temperature characteristic, the speed characteristic and the height characteristic were calculated under given control schemes. The results show that specific fuel consumption reduces at low rotational speed mainly due to the increase of specific thrust, it ascends at high rotational speed primarily because of the increase of fuel-air-ratio and the decrease of Bypass-Ratio, the thrust rises all the time while the rotational speed of low-pressure compressor goes up. Meanwhile, the gas in nozzle can be expanded completely at the height of 0 m, thrust descends mainly due to the reduction of air flow entering the engine when the atmospheric temperature increases. When flight speed becomes faster, specific thrust is the dominating reason for the increase of specific fuel consumption, while the flight Mach number is less than 0.8 , thrust reduces mainly because of the decrease of specific thrust, when flight Mach number is greater than 0.8, the great rise of air flow causes the increase of thrust. Low Reynolds number correction was adopted in the last research, when the height surpasses 11 000 m, the decreasing efficiency of compressors caused by low Reynolds number is the primary reason why specific thrust descends, the efficiency decline of high-pressure compressor is greater than that of low-pressure compressor.