Session: 01-08 Inlets, Nozzles, Mixers and Nacelles II

Paper Number: 128990

128990 - Fluidic Thrust Vectoring on an Altitude-Adaptive Double-Divergent Nozzle Using a Bypass Passage 

Fluidic thrust vectoring of aerospace vehicles such as aircraft, rockets and missiles has been an emerging technology, where the nozzle exhaust flow is deflected to change the attitude and trajectory of the vehicle. Shock Vector Control (SVC) method is one of the earliest methods that is classified under fluid thrust vectoring and has been studied extensively in the past. This method works by injecting secondary fluid stream into the diverging section of the nozzle, which acts as an obstacle to the primary nozzle flow. As a result, the primary nozzle fluid moves around the secondary flow through a separation shock. This results in a pressure difference between the walls of the nozzle, and is the motive force for thrust vectoring. Although large thrust vector angles are generated using the secondary injection, but the thrust losses associated are high. To mitigate the thrust losses, researchers proposed the bypass SVC method. Till date, this method has been limited to single-divergent nozzles only.

The present study proposes a fluidic thrust vectoring scheme that incorporates a bypass passage from the nozzle upstream section to the divergent section. This is to minimise the thrust losses encountered with the secondary injector. The bypass passage is used on a novel type of double-divergent nozzle with rectangular cross-section. This double-divergent nozzle is characterized by its altitude adaptive capability. Such a nozzle consists of two diverging sections: a base nozzle and an extension nozzle, separated by an inflection point. The main objective of this study is to examine if an altitude adaptive nozzle is advantageous over the traditional single-divergent nozzle with respect to fluidic thrust vectoring using a bypass passage. The exit Mach number of the double-divergent nozzle is 2.07. The length of the base nozzle is varied keeping the Mach number at the inflection point fixed at 1.5. Three different lengths of the base nozzle are taken: L/2, L/3 and 2L/3, where L represents the total length of the diverging section of the nozzle. Two dimensional steady-state Reynolds Averaged Navier-Stokes equations are computationally solved to demonstrate the flow-field inside the nozzles. The SST k-ω turbulence model is selected for turbulence closure. The system of equations is solved using commercially available software ANSYS Fluent. The flow-field inside the nozzles, including the pressure profile along the walls, the shock structure and the flow separation location are discussed in detail. The performance parameters such as the thrust vector angle, thrust vectoring efficiency, coefficient of discharge, and thrust losses are also presented. The results obtained from the double-divergent nozzles are compared with those of a single-divergent nozzle simulated under identical conditions.

Presenting Author: Arnab Kumar Das Indian Institute of Technolgy Guwahati

Presenting Author Biography: Arnab K. Das is currently pursuing his PhD at the Indian Institute of Technology (IIT) Guwahati, India. He did his Master of Technology in Mechanical Engineering from the same institute. His areas of interest include Rocket Propulsion, Aerodynamics, Molecular Gas Dynamics, and Computational Fluid Dynamics. He has published technical papers in ASME Journal of Fluids Engineering and AIAA Journal of Spacecraft and Rockets.

Authors:

Arnab Kumar Das Indian Institute of Technolgy Guwahati
Tapan K. Mankodi Indian Institute of Technology Guwahati
Ujjwal K. Saha Indian Institute of Technology Guwahati