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

Submission Number: 173560

Thrust Vectoring of a Supersonic Micro Nozzle for Generating Enhanced Lift in Tactical Aircraft 

With the advances in micro machining techniques such as the electrohydrodynamic jet printing; bulk-silicon etching and silicon-glass electrostatic bonding; and laser precision machining technique, a micro nozzle can be fabricated with good precision. Micro nozzles are based on digital propulsion; and may find their application in micro aerial vehicles (MAVs), unmanned aerial vehicles (UAVs), tactical aircraft, and missiles. Supersonic micro nozzles are more suitable for the tactical aircraft and missiles operating in supersonic/hypersonic range. These nozzles, being light-weight, their potential can be realized in the cooling of control surfaces of missiles, and delaying the boundary layer separation over the aircraft wings by injecting gas at supersonic speeds, thereby enhancing the lift. In such a context, fluidic thrust vectoring (FTV) on a micro nozzle could be very effective, and could be used to eject the gas in the desired direction. Shock vector control (SVC) is a prominent FTV scheme in which a secondary fluid is injected into the diverging section of the nozzle. This leads to the generation of a shock wave across which the primary fluid deflection occurs, thereby leading to the vectoring of thrust. In the past few decades, SVC has been thoroughly investigated both experimentally and numerically. However, these analyses pertain to conventional sized nozzles where continuum is valid throughout. SVC is yet to be investigated on a micro nozzle.

The objective of the present study is to numerically investigate SVC on a micro nozzle using a bypass passage. Two different micro nozzles are used: (a) a single divergent nozzle (SDN), and (b) a double divergent nozzle (DDN). Both the nozzles have the same ϵ = 1.7 and throat height, H_t = 20 μm. For the DDN, equal lengths of the base and the extension nozzles are considered. N₂ is used as the working fluid. The bypass passage opening on the diverging section is located at 0.9 fractional nozzle length and is orientated at an angle of 90°. The bypass passage width, h is such that the ratio h/H_t equals 0.3. Given the small length scale of a micro nozzle, continuum fluid dynamic analyses fail to solve the flow field. In the present study, an in-house direct simulation Monte Carlo (DSMC) solver, which is a particle method, is used to solve the flow field in the micro nozzles. The no-time counter (NTC) scheme is used for the selection of collision pairs in each cell of the computational domain. The collisions are performed using the variable hard sphere (VHS) model, and the post-collision energies are determined using the Borgnakke-Larsen (BL) method. The pressure at the nozzle inlet is fixed at 1 atm, and the pressure at the far field boundaries are determined from the NPR values. The NPR is chosen in the range of 4–10. The boundary conditions used in the present study might not be realistic enough to simulate the operating conditions in the context of missiles and tactical aircraft for the specified objectives. However, the focus of the present study is mainly to understand the thrust vectoring process in a micro nozzle, irrespective of what the operating conditions might be. Therefore, an ambient pressure of 1 atm is specified at the inlet and is kept fixed. The flow field is analysed by investigating the pressure distribution, Mach and pressure contours. The shock structures are studied, and the performance parameters such as δ and the thrust loss, ω are evaluated and compared.

Presenting Author: Arnab Kumar Das Indian Institute of Technology Guwahati

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

Authors:

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