Research Of Aircraft Stealth Design Based On LHM

Researches about stealth design technology and improving survivability have become important topics of high performance aircraft frontier research by using advanced techniques and methods. Left-handed material(LHM) is a new kind of structural materials, which has the advantages of high absorption, small thickness, light weight and wide application range, and it has become the focus of attention in recent years. In this article, exploratory research in the application method of LHM stealth design is launched from the perspective of the stealth technology requirement, and for the first time the LHM is used in aircraft stealth design. The research is divided into theoretical research and application design, theoretical research includes LHM numerical simulation, parameter extraction, electromagnetic scale model measurement methods and electromagnetic properties study; application design includes LHM stealth design in the aircraft wing leading edge, antenna cabin, and vertical tail. In this paper, the main work includes the following aspects:1. A LHM transmission/ reflection method based on bi-directional coupling compensation is proposed, which solves the problem that the error is caused by the coupling of LHM units in the traditional transmission / reflection method. The methods of coupling compensation in two strong coupling directions are studied by using the equivalent of the LHM unit as a two port network. The simulation results show that the method improves the extraction accuracy of the LHM electromagnetic parameters, and this method provided a method for electromagnetic parameters extraction in subsequent LHM area equivalent.2. Two LHM radar cross section(RCS) estimate methods are put forward, which are the same frequency scale model estimation method and the MOM- PO hybrid estimation method based on the impedance boundary. The same frequency scale model method is based on RCS general formula, which estimates the actual model RCS by using scale model RCS. The MOM- PO hybrid estimation method estimates RCS by method of moment and physical optics method,when the LHM being equivalent to the the homogeneous medium with equivalent electromagnetic parameters. By making the real model and doing the microwave experiment, two kinds of estimation methods are verified to estimate RCS accurately, and which provide methods for the design of the LHM in the large size target.3. A sandwich low observable wing structures with LHM is presented, which can effectively solve the problem of strong scattering in the wing leading edge. In the wing structures, the wing leading edge is improved with the left hand absorbing material, wedge structure and gradient foam layer based on the left hand absorbing material electromagnetism characteristic, and then the structure parameters are optimized by multi-island genetic algorithm based on the surrogate model. Simulation results showed that the stealthy wing structure can significantly reduce the aircraft wing leading edge RCS, compared to metal wing section RCS reduction up to a maximum of 15 d Bsm. Compared with the metal web RCS reduction up to a maximum of 25 d Bsm.4. A design method of LHM stealth vertical tail is proposed for solving the bad shippingdirection stability of the flying wing aircraft. The stealth vertical tail is designed according to the requirements of shipping-direction stability of flying wing aircraft, and then is stealth designed by using the left hand absorbing materials. Physical models are made according to the design in this paper, model simulation results and the microwave experiment data verify that the RCS only has a small increase, but stability has a significant improvement after adding stealth tail on the flying wing aircraft.5. The stealth antenna cabin is designed with LHM, which solves the problem that the aircraft RCS increase significantly due to the antenna cabin. Firstly, doing the microwave experiment with LHM antenna cabin physical models, and then the accuracy of the LHM cabin structure calculation method is verified by the experiment data, then the LHM is try to used in antenna cabin stealth design, and the scattering characteristics of LHM antenna cabin with different structure parameters is studied. The calculation results show that there is no significant increase in the aircraft stealth performance because of the LHM antenna cabin.