DATE:                                    Thursday, 17 March 2022

TIME:                                     4:00pm

LOCATION:                          33-206 (and via Zoom)

SPEAKER:                            Dr. Dilip Prasad, Director of Propulsion, Environmental & Fuel Systems, Gulfstream

TOPIC:                                   Shock Dispersion in Turbofan Ducts

ABSTRACT:

The subject of this seminar is the forward-radiated tone noise generated by a high-bypass turbofan engine at takeoff power.  At this operating condition, the relative flow past the rotor tip is supersonic, resulting in the generation of a rotor-locked shock field that propagates upstream.  The shocks generated by the individual blades are non-uniform owing to manufacturing and assembly tolerances, and this results in the generation of “buzz-saw” noise.  Contemporary understanding of this noise mechanism is based on a purely two-dimensional perspective.  In the present study, it is shown that this perspective is flawed since it does not account for the effects of wave dispersion.  A theoretical framework is developed for this purpose, based on the asymptotic behavior of the wave dispersion relation for large azimuthal wavenumbers, coupled with weakly nonlinear dynamics.  The framework also permits the examination of the dispersive and dissipative effects on the shock field of the inlet acoustic liner, an aspect that has received limited attention in the past.  The implications of the present findings for shock noise abatement are discussed.

BIOGRAPHY:
Dr. Dilip Prasad is currently the Director of Propulsion, Environmental & Fuel Systems at Gulfstream, a position he has held since 2020.  Prior to this, he served in a variety of technical and managerial roles at multiple divisions of Raytheon Technologies, including the Research Center, Pratt & Whitney, Rocketdyne and Collins Aerospace.  Through his career, Dr. Prasad has applied analytical methods to solve problems related to diverse products, primarily in the aerospace industry, with occasional forays into other areas such as refrigeration and elevators.  In the aerospace industry, he has contributed to the development of gas turbines, environmental control systems, fuel systems and rocket engines.  Dr. Prasad’s educational background consists of an undergraduate degree in Mechanical Engineering from the Indian Institute of Technology at Madras and SM and PhD degrees from MIT in the same field.