A n-dot closed loop control algorithm was applied to the startup process for a civil turbofan engine. Therefore

an openned/closed loop sectional combination control scheme for turbofan engine's starup process was designed. The simulation result shows that the n-dot closed loop control algorithm could cause oscillation at the beginning of startup process of turbofan engine. To eliminate the parameters' oscillation at the beginning of startup process

the n-dot closed loop control algorithm was improved according to the rationale of surge recovery by using fuel air ratio unit as the control variable. The experiment results illustrate that the improved sectional combination control scheme could effectively restraine the parameters' oscillation

and furthermore the startup transition process had satisfying stability and repetitive. The numerical difference of high pressure rotor speed under different atmosphere conditions does not exceed 1.0% and the time delay does not exceed 0.9s; meanwhile the numerical difference of high pressure rotor speed under different flight conditions does not exceed 1.0% and the time delay does not exceed 1.2s.