ESTIMATION OF THE AERODYNAMIC CHARACTERISTICS OF A STEPPED NACELLE FOR THE AIRCRAFT POWERPLANT

The purpose of this work is to estimate the aerodynamic characteristics of the stepped nacelle of a gas turbine engine with a turbofan unit. The research was based on the method of model physical experiment. The wind tunnel applied for the study was provided with the necessary equipment, which includes various nozzles of static and dynamic pressure with coordinate devices, etc. For the experimental study, we built the models of nacelles for an aviation power plant with front location of the fan module and with the rear arrangement of a turbofan unit. We have experimentally investigated the aerodynamic characteristics of the stepped nacelle for a gas turbine engine with a turbofan unit. The results of this study demonstrated a possibility to decrease the aerodynamic drag of the stepped nacelle for an engine with a turbofan unit compared to the nacelle of a turbojet double-pass engine with the front arrangement of the fan. In the range of angles of attack α=0...20° the value of aerodynamic drag of the stepped nacelle for a gas turbine engine with a turbofan unit decreases by 49...55 %. The obtained results showed that the coefficient of lifting power of the stepped nacelle for a gas turbine engine with a turbofan unit increases by 24...64 %. The coefficient of aerodynamic drag is lower by 18...28 % compared with the aerodynamic drag coefficient of a cylindrical nacelle for a double-pass turbojet engine in the range of angles of attack α=2...20°. Our findings indicate the prospects of using engines with a turbofan unit. The structural feature of the stepped nacelle would reduce the loss of efficient engine thrust by decreasing aerodynamic drag almost by two times and could increase fuel efficiency of the engin