Session: 01-05: Inlets, Nozzles, Mixers and Nacelles I

Submission Number: 172626

Fluidic Thrust Vectoring of a Dual Bell Nozzle for Supersonic Aircraft Using the Shock Vector Control Approach 

Fluidic thrust vectoring (FTV) has become a pivotal technique in modern aerospace systems to obtain improved agility, stability, and control without relying entirely on mechanical actuators, which often introduce additional weight and system complexity. The advanced maneuverability in such systems depends on the operation of its propulsion nozzle. The idea is to inject a secondary fluid in the nozzle to deflect the direction of the primary fluid and thereby vector the direction of the thrust. Shock vector control (SVC) is a prominent type of FTV scheme for aerospace systems operating in the supersonic/hypersonic regimes such as supersonic aircraft and missiles. In SVC, a secondary fluid is injected in the diverging section of the nozzle, and the primary fluid gets deflected due to the generation of a shock wave. SVC has been extensively investigated in the past few decades and is well documented in the literature. Recent investigations in SVC aim to enhance the thrust vectoring angle, δ by incorporating dual divergent contours. In fact, researchers have observed that the δ increases significantly upon the use of dual divergent contours. However, thrust vectoring is required intermittently, and the contours used in the dual divergent nozzles have predominantly been linear. Therefore, it would lead to a significant loss of thrust when operating in the non-vectored state. Parabolic contours, in lieu of linear contours, lead to reduction of thrust loss in the non-vectored state because of their smaller exit angles. It then also becomes essential to investigate SVC on a dual bell nozzle (DBN) having two parabolic contours for the two diverging sections. A DBN with its two diverging sections being separated by an inflection point, provides altitude adaptation too by functioning in two distinct modes: (a) sea-level mode, and (b) altitude mode depending on the ambient pressure and nozzle pressure ratio (NPR).

The present study aims at numerically investigating the SVC on a two-dimensional (2D) DBN integrated with a secondary fluid injector for supersonic aircraft to understand the flow field behavior, shock structures, and thrust vectoring performance characteristics, such as δ and thrust loss, ω. In particular, two DBNs of varying nozzle area expansion ratio, ϵ = 1.79 and 2.0 are considered. In each DBN, the lengths of the base and the extension nozzles are kept equal. The Mach number at the inflection section is fixed at 1.5. The secondary injector is positioned in the extension nozzle of the DBN at 0.9 fractional nozzle length, and is oriented at 90° with the wall. The NPR is selected in the range of 4–10, keeping the secondary pressure ratio (SPR), defined as the ratio of the stagnation pressures of the secondary to the primary fluids, fixed at 0.7. By focusing on the area ratio as the primary variable, this study seeks to shed more light on how it affects the shock structures, nozzle efficiency, and flow separation. To analyze the compressible flow field, 2D steady-state Reynolds-averaged Navier-Stokes equations are computationally solved using the density-based solver in ANSYS Fluent (version 2022 R2). The Advection Upstream Splitting Method (AUSM) is employed for the computation of the convective fluxes. To calculate the gradients in the viscous fluxes, the least-squares method is used. The shear stress transport k-ω turbulence model is used for turbulence closure due to its capability of accurately capturing separation regions and shock-boundary layer interactions. Preliminary results indicate that at NPR = 6, the ω of the DBN with ϵ = 1.79 is lower by approximately 30% than that of the DBN with ϵ = 2.0. However, the δ of the DBN with ϵ = 2.0 is higher by approximately 43% than that of the DBN with ϵ = 1.79. Further, when compared with a dual divergent nozzle with linear contours and similar ϵ, it is observed that the ω of the DBN with ϵ = 1.79 is approximately 46% lower.

Presenting Author: Arnab Kumar Das Indian Institute of Technology Guwahati

Presenting Author Biography: Hailing from Assam, India, Mr. Arnab Kumar Das is pursuing his PhD in the department of Mechanical Engineering at the Indian Institute of Technology Guwahati. His doctoral thesis is focused on the fluidic thrust vectoring of aerospace systems. He is working on both conventional sized nozzles, and nozzles at micro scales by using Navier-Stokes equations and direct simulation Monte Carlo, as well as their hybrid form. He has published technical papers and review articles in various prestigious ASME and AIAA journals.

Authors:

Raju Kumar Indian Institute of Technology Guwahati
Arnab Kumar Das Indian Institute of Technology Guwahati
Ujjwal K. Saha Indian Institute of Technology Guwahati