Abstract:

Based on the thermodynamic principles, a mixed exhaust turbofan cycle is split into an inner "regenerative" subcycle and an outer simple subcycle （Fig. 2） with the borrowed work （Eq. 2） and the borrowed heat （Eq. 3） refunded to the inner subcycle. The performance of the engine is shown to be composed of subcycles'performances through respective fraction ratios a and (3 as in Eqs. 4-10. Fig. 3 gives a thorough view of the energy and efficiency relation in the subcycles as well as for the whole engine. The illustrated example in Table 1 indicates that, although combined with an efficient inner regenerative subcycle, a low compression and low heating outer subcycle gives a thermal efficiency inferior to the corresponding simple jet engine. The overall efficiency, thrust and specific fuel consumption are better only due to high propulsive efficiency. The respective functions of two subcycles in the engine are thus elucidated.