Preliminary Study On Integrated Aerodynamic Characteristics Of The Fighter/Engine

Aircraft/engine integration is the inevitable development trend for the modern and future fighters.The integration is the study of the interaction between the aircraft and engine, in order to reduce theadverse effects and get a better aircraft/engine matching performance. The piggyback layout andinstallation of the engine on the aircraft is the main trend for the future fighter and unmanned aircraft.Under the engine working, the mutual interference and influence of the aerodynamic characteristics ofaircraft and the propulsion systems of the engine becomes more complex on this condition, so thehigher integration is required. Based on one dimension flow, CFD numerical simulation andoptimization techniques, the article has a preliminary study on the integrated aircraft/engineaerodynamic performance of a class of the future concept fighter.First, the article establishes a primary three-dimensional geometric model of the aircraft,reference to the design character of the advanced concept fighter and unmanned aircraft, and writes amixed exhaust turbofan engine steady-state performance computing program with the thrustrequirement of the engine for the aircraft, and determines characteristic cross-sectional performanceparameters of the engine and the basic dimensions of the propulsion systems flow path; the articlealso designs the supersonic inlet with the “C” imported shape, writes a relevant geometric designprocess, and the inlet has been modified for the startup characteristics of the inlet; using a geometricapproximation method for writing a design programs for the nozzle, the article gets a relatively betteraerodynamic performance nozzle.Second, the article has a preliminary research on the aerodynamic performance of the originalaircraft model, and analysis the life and drag characteristics of the original aircraft model with theCFD numerical simulation. The article also writes a geometric model modification program for thedrag larger parts of the original aircraft, and optimizes the drag characteristics of it, through the use ofgradient algorithm with the ISIGHT software. The drag of the aircraft model can be reducedeffectively with the reducing of the bottom area of the aircraft and the more gentle transition to theback of the fuselage of the upper and lower surface of the fuselage.Then the article has a research on the aerodynamic performance of the engine and theaircraft/propulsion system of the modified aircraft with the integrated installation, and also has acomparative flow field analysis without the engine installation. The results show that there is a largeeddy on the bottom of the fuselage, the larger flow loss, lower static pressure at the bottom of the fuselage, the pressure drag is bigger at the bottom of the fuselage without the installation of the engine;after the installation of the engine, the total lift and drag are increased of the fighter, the flowcoefficient of the inlet is decreased, and the total pressure recovery coefficient of the nozzle isreduced.Last, the article analysis the aerodynamic performance of the fighter and the propulsion systemsof the engine and studies the mutual interference flow mechanism of the fighter/engine integrationflow field under the installation position changes of the engine. The results show that when the spacebetween the engines is from small to large, the flow coefficient of the inlet is decreased firstly andthen increased; the total pressure recovery coefficient of the nozzle is increased firstly and thendecreased; the total lift and drag of the fighter are gradually reduced, but the reduced magnitude isdifferent; the lift-drag ratio of the aircraft is gradually decreased, and the thrust-drag ratio of theaircraft is gradually increased at last.