Design and analysis of noise suppression exhaust nozzle systems
Abstract
The exhaust nozzle is an integral part of a jet engine and critical to its overall system performance. Challenges associated with the design and manufacturing of an exhaust nozzle become greater as the cruise speed of the aircraft increases. The exhaust nozzle of a supersonic cruise aircraft requires additional capabilities such as variable throat and exit area, noise suppression, and reverse thrust. The present work is an effort to study the design and analysis of jet engine exhaust nozzle systems such as the axisymmetric plug nozzle, the chevron nozzle and the ejector nozzle with clamshells. High-bypass-ratio jet engines with two or more flow streams have superior noise suppressing and thrust characteristics. Much research has been done in the past to study and understand the flow physics of these engines. In the present work a computational fluid dynamics-based approach was used to study the jet engine exhaust nozzle systems. First, a computer-aided-design model of a three-stream separate-flow axisymmetric plug nozzle was created and axisymmetric flow simulations were performed to study the flow field. The mean flow and turbulent kinetic energy fields were compared with the particle image velocimetry results available in the literature. Next, computational fluid dynamics was used to study the performance of passive chevron mixers in enhancing the turbulent mixing. Three-dimensional calculations were carried out to study the effect of enhanced mixing on the mean velocity and turbulent kinetic energy flow fields. Different turbulence models were used to study their performance in predicting chevron-based jet flows. Gas turbine engine manufacturer Rolls-Royce, and business class aircraft manufacturer Gulfstream Aerospace Corporation, are collaborating on the development of technologies for a supersonic jet. As part of this collaborative research and development program, an ejector nozzle with clamshell doors, similar to that on an Olympus-593 engine, which powered the Concorde aircraft, was designed and tested. The ejector nozzle offers additional advantages such as thrust augmentation and noise suppression. Numerical simulations of this ejector nozzle with clamshell doors at 11.5° clamshell angle and without clamshell doors were performed as part of the validation task. Mean flow fields were predicted for low subsonic experimental conditions and compared with the experimental data. Flow separation and recirculation zones were encountered near the inner surface of clamshell doors. Simulations at higher nozzle pressure ratios were also performed to simulate actual flight conditions. Flow separation prevailed at this condition as well. The existing new supersonic noise suppression exhaust nozzle design was improved by the addition of chevrons and its flow field was analyzed using computational fluid dynamics. The jet engine exhaust nozzle consisted of three-dimensional ejectors in the form of clamshell doors and chevrons as passive mixers. Chevrons were placed in the ejector slot to introduce streamwise vorticity and enhance mixing. It was observed that the flow separation zone was almost removed and an improvement in the ejector performance was obtained. Computational simulations corresponded to take-off conditions with a nozzle pressure ratio of 1:7 and freestream Mach number of 0.3.
Degree
M.S.A.A.
Advisors
Blaisdell, Purdue University.
Subject Area
Aerospace engineering|Mechanical engineering
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