Patent ID: 7788899

Claim:
A thrust augmentation system for a turbofan engine having mixed exhaust, the thrust augmentation system comprising: an augmentation duct configured to receive a fixed ratio of primary and secondary air of the turbofan engine during operation of the turbofan engine, the augmentation duct positioned co-axially with and downstream of an exhaust case of the turbofan engine and having a cross-sectional area sized to accommodate unrestricted flow of the primary and secondary air, the primary and secondary air producing non-augmented thrust; a combustion system positioned aft of the exhaust duct within the augmentation duct for increasing thrust produced by the mixed exhaust of the turbofan, the combustion system producing augmented thrust; and a non-variable area exhaust nozzle for continuously increasing velocity of the mixed exhaust and having a throat area t f smaller than a minimum cross-sectional area of the augmentation duct and smaller than a throat area t A required for accommodating flow of the primary and secondary air during generation of a maximum theoretical augmented thrust, the throat area t f being about 20% to about 30% larger than a throat area t 0 required for accommodating flow of the primary and secondary air during generation of a maximum theoretical non-augmented thrust.