It consists of the variable stator vane of RFAN (VS[V.sub.RFAN]) and HPC (VS[V.sub.HPC]), the variable area nozzle of the HPT guide vane (VA[N.sub.HPT]) and LPT guide vane (VA[N.sub.LPT]), VABI and the variable area section of the main nozzle's throat ([A.sub.8]), and the bypass nozzle's exit ([A.sub.2]8).
Then, the gas from the LPT mixes with the air from the first bypass duct at the VABI and will be exhausted through the main nozzle.
Different from three-stream ACE, it has the third bypass duct, front VABI, and the core-driven fan stage (CDFS) .
The model also considers the mixing loss of the VABI, the effects of bleed air, the shaft power set aside for aircraft, and so on .
The matching constraints include flow compatibility of the HPT and LPT, power equilibrium of the high-pressure rotor (HPR) and low-pressure rotor (LPR), static pressure equilibrium of the VABI, and compatibility of [A.sub.8] and [A.sub.28].
When the ACE operates at the subsonic cruise or supersonic cruise condition, turning down the VABI decreases the thrust and airflow.
As for the VABI, it has almost no effect on ACE's thrust, airflow, and the operating point of component, compared with other variable geometries.