| The low-speed UAV engine nacelle comprises the main components of nacelle cover, radiator, air duct etc.. Nacelle cover wraps the whole engine parts and rectifies the fuselage rear airflow. The heat radiator will dissipate heat of about the half of engine output power and generates additional drag of about 10% of the whole UAV drag. The radiator duct is designed to guide cooling airflow to the radiator which is installed inside the nacelle.Low-speed UAV has both characteristics of high cooling requirement and high lift to drag ratio. Therefore, engine nacelle must provide poper cooling performance with smallest additional drag.The main contents of this paper is the design and test methods of UAV nacelle, including the wind tennel test method of the heat radiator, radiator duct design method and the nacelle configuration comparison.It is difficult to get the accurate flow resistance data of heat radiator with ordinary test method, which is necessary for the drag-reducing design. Therefore the author proposes a type of wind tunnel test method which can get the accurate flow resistance data of heat radiator, and verifies the test result with the radiator drag data from six component balance.The air flow mass and drag of the heat radiator will be influenced by the inlet and outlet flow conditions and the flow resistance of the duct. In this paper, several typical ducts are compared through the theoretical calculation method, and the expansion duct is most favorable for the lowest drag. In addition, the influence of the inlet and outlet pressure of the air duct on the radiator cooling performance is adiscussed in this paper.The CFD simulation and tested drag of sevaral nacelle configuations are discussed in this paper, and the final conclusion is reduction of flow separation will reduce the nacelle drag.Some UAV nacelle design and test methods are discussed in this paper which are valuable for engineering application and similar engine nacelle design reference. |
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