Aerodynamic Characteristics of the F/A-18 at Large Roll Angles and High Incidence

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ciated with the wave rotor were active. The active variables considered were the rotational speed of the wave rotor and the heat added to the wave rotor. Important active constraints included the limits on maximum speeds of the compressors, a 15% surge margin for all compressors, and a maximum wave› rotor exit temperature. The engine thrust was selected as the merit function. The wave› rotor› engine design became a sequence of 47 optimization subproblems, one for each mission point. Only by using the cascade strategy could the problem be solved successfully for the entire e ight envelop. For the mission point dee ned by Mach number = 0.1 and altitude = 5000 ft, the convergence of the two-optimizer cascade strategy is shown in Fig. 3. The e rst optimizer produced an infeasible design at 67,060.87-lb thrust in about e ve design iterations. The second optimizer, starting from the e rst solution with a small perturbation, produced a feasible optimum design with an optimum thrust of 66,901.28 lb. The optimum solutions for the 47 mission points obtained by using the combined tool were normalized with respect to the NEPP results and are shown in Fig. 4. The combined tool produced a higher thrust than the NEPP for mission points 12, 26, and 32. Both NEPP and COMETBOARDS› NEPP produced identical optimum thrust values for a few mission points. The maximum difference in thrust exceeded 5% for several mission points. These differences could be signie cant if the design points with increased thrust were used to size the engine. The combined COMETBOARDS› NEPP tool successfully solved the subsonic wave› rotor› engine design optimization problem.