Research On The Integration Method About Aerodynamic And Stealth Characteristics Of Helicopter Fuselage

The integration design method about aerodynamic and stealth characteristics of armed helicopters is a challenging subject in the field of helicopter aerodynamic and integrated design. In this thesis, for the complicated characteristics of their aerodynamics and electromagnetic scattering, a Radar Cross Section (RCS) calculation method was established based on high-frequency characteristics and a CFD numerical simulation method was developed by the momentum source model. By this method, the effects of the Z-9 helicopter rotor /fuselage with different parameters on its aerodynamic and RCS characteristics have been simulated respectively. Then, based on optimization methodology, an integration method about aerodynamic and stealth characteristics of helicopter fuselage has been investigated. The major research work in the thesis is as follows:As the background of the current work, the development of radar stealth technology was introduced briefly, and the domestic and oveseas research results on the stealth aircraft have been presented. It is pointed out that the integration method about aerodynamic and stealth characteristics of helicopter fuselage is necessary and important.In Chapter 2, according to the characteristics about geometry, radar cross section and interaction flowfield of combined helicopter rotor and fuselage, a helicopter geometry model has been developed. Then an integration method of mesh generation for predicting radar cross section and flowfield of the combined helicopter rotor and fuselage was given.In Chapter 3, considering the characteristics about high frequency electromagnetic scattering, a panel edge method by combining the physical optics and the method of equivalent currents has been developed. By taking the combination model of sphere with plate and a complicated structure of missile as numerical examples, it was demonstrated that the present method is effective to analyze the RCS of any complex target. Then some shape design approaches for aiming at reducing helicopter RCS have been obtained by anaylyzing the RCS characteristics of Z-9 helicopter and a certain armed helicopter. Further the analysis about the time domain and frequency domain of RCS characteristics about the rotor have been conducted by a quasi-static method, and the results reflected the Doppler effect of electromagnetic waves.In Chapter 4, based upon Jameson finite volume method and the momentum source model which was used to consider the effects of helicopter rotor on its flowfield, a numerical method and code suitable for solving the flowfield and aerodynamics characteristics of helicopter has been developed. The calculated results were compared with the available experimental data to demonstrate that the validation of the method. Then, the effects of Z-9 combined helicopter rotor and fuselage with different structures (vertical and horizontal ratio of the fuselage, sweep of the horizontal tail) on its flowfield and aerodynamic characteristics have been investigated respectively in hover and forward flight. Based on the above investigations, some conclusions about the effect of different fuselage design parameters on the aerodynamic characteristics of helicopter have been obtained.In Chapter 5, based on the optimization agent methodology, an integration method about aerodynamic and stealth characteristics of armed helicopter fuselage has been established. Firstly, the integration analysis about aerodynamic and stealth characteristics of Z-9 helicopter fuselage has been performed. Then, by choosing two different design goals, the integration design about aerodynamic and stealth of Z-9 have been conducted, and the structure parameter combinations about fuselage that can improve aerodynamic performance and reduce RCS were given at last.