Predictor–Corrector Method for Scramjet Inlet Air Mass Flow Rate Measurement

Abstract

The accurate and real-time measurement of the scramjet inlet air mass flow rate is critical to flight control. To measure the scramjet inlet air mass flow rate, air data parameters are estimated. The inertial-navigation-system-computed air data are real time but not accurate enough. The flush air data sensing system can provide sufficiently accurate estimations of air data parameters, but it is not employed during the flight. This paper proposes a predictor–corrector method. Accurate air data estimations are not required. The scramjet inlet air mass flow rate estimated by the inertial-navigation-system-computed air data is taken as the prediction value. Surface pressure measurements combined with the inertial navigation system provide the correction value. The algorithm is simple enough and can be implemented in real time. Comparing the results of the scramjet inlet air mass flow rate estimated by the inertial navigation system and predictor–corrector method, it is shown that the predictor–corrector method can greatly improve the accuracy of the scramjet inlet air mass flow rate measurement. The scramjet inlet air mass flow rate measurement sensitivity to the freestream static pressure, static temperature, and angle of attack is reduced significantly by the predictor–corrector method.