A study of the influence on performances, specially on fuel consumption, of the effect of varying exhaust nozzles areas and specific work of the fan in two-spools turbofan engines is carried out. The study is conducted by means of an approximated method, essentially based on substituting the performances maps of compressors, fan and turbines by means of approximated analytical expressions. The approximation given by the method is verified by comparing results with those theor£ tically obtained without simplifications and with actual data obtained from air data computer measurements carried out in flight resulting in both cases excellent approximations. Final results show that modest but significant reduction in fuel consumption may be obtained by varying the exhaust areas and specific work of the fan, which couples with important reductions in turbine inlet temperature. All this might be of special interest for large turbofan engines specially designed for short range aircraft.
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