Aerospace, Mechanical & Electronic Engineering ITChttps://research.thea.ie/handle/20.500.12065/22912024-03-28T15:42:33Z2024-03-28T15:42:33ZNumerical studies of ram-air Intake for near-earth satellitesRavuri, NishitaScully, StephenVashishtha, Ashishhttps://research.thea.ie/handle/20.500.12065/47622024-03-23T03:01:57Z2024-01-01T00:00:00ZNumerical studies of ram-air Intake for near-earth satellites
Ravuri, Nishita; Scully, Stephen; Vashishtha, Ashish
The operation of satellites in Earth orbits with altitudes lower than 450 km involves dealing
with rarefied atmosphere environment. To compensate for the aerodynamic drag present
in this low-density atmosphere, satellites employ traditional Electric Propulsion, EP (limited
operational life) or Air-Breathing Electric Propulsion Systems, ABEP (longer operational life).
Careful geometric design of intakes of ABEP systems is critical for its performance. The
main motivation of this research is 1) to understand the complex flow around basic intake
configurations of ABEP systems in high-speed rarefied environment- using Direct Monte
Carlo Simulation (DSMC) methods, and 2) to design compression-assisted air-breathing intake
geometry operating efficiently at various orbital speeds for VLEO/SLEO satellite applications.
Two-dimensional axisymmetric, time-dependent Direct Simulation Monte-carlo (DSMC) method
has been utilized based on open-source SPARTA DSMC Simulator for various intake geometries
at three relevant altitudes. Initial simulations of basic hollow cylinder (straight duct) geometry
were run, followed by an analysis of different convergent angles for converging duct intakes,
for both specular and diffuse gas-surface interactions. The results have been analysed for the
collection efficiencies, mass flow rates at the entry and exit planes, drag force and the number
density profiles. It was observed that with increase in altitude, there is a considerable decrease
in the collection efficiencies under diffuse reflection conditions, and a considerable increase of
drag coefficients under specular reflection conditions
2024-01-01T00:00:00ZStudying the influence of aluminium in ADN/HTPB-based solid propellantsKore, RushikeshNagendra, KumarVashishtha, Ashishhttps://research.thea.ie/handle/20.500.12065/47612024-03-22T03:01:56Z2024-01-01T00:00:00ZStudying the influence of aluminium in ADN/HTPB-based solid propellants
Kore, Rushikesh; Nagendra, Kumar; Vashishtha, Ashish
Ammonium Dinitramide (ADN) combustion has been the subject of great interest over the
past few years due to consideration as a green oxidizer in solid rocket propellants. This study
is focused on predicting the flame structure of an ADN/HTPB and ADN/HTPB/Al sandwich
propellant. Initially, one-dimensional reactor modelling was carried out to implement the
detailed chemical kinetics for AP and ADN monopropellant. Detailed understanding on the
different combustion zones of ADN monopropellant was studied with implementation of one dimensional reactor modelling.
The results of one-dimensional studies were found to have
good correlation with the previous literature. The sensitivity analysis was performed to
understand the major species and dominant reaction in different burning zones. Initially,
sandwich model was tested on AP/HTPB sandwich propellant and subsequently it was noticed
that the findings were identical. The burn rate results of the AP/HTPB sandwich model were
validated with the existing literature and were found to be in close match. Followed by this
ADN/HTPB sandwich propellant was simulated using a detailed combustion chemistry using
215 reactions and 51 species were used to predict the flame structure across a wide range of
pressure. The physiochemical reactions that occur during the combustion of ADN and HTPB
are thoroughly examined by employing a complete gas phase combustion model. The
computational framework is based on mass, species concentration, and energy conservation
equations. For a pressure range of 0.6-6Mpa, the flame structure of the sandwich propellant
in different combustion zones was studied. The simulations were also carried out with the
addition of aluminum in a homogenized manner in ADN/HTPB sandwich. The gas phase
temperature was found to increase with the addition of aluminum. The addition of nano
aluminum was observed to have an influence on the flame structure and enhance the
performance significantly.
2024-01-01T00:00:00ZNumerical investigation of the impact of injectors location on fuel mixing in the hifire 2 scramjet combustorPalateerdham, S.K.Phaneendra Peri, L.N.Ingenito, A.Vashishtha, A.https://research.thea.ie/handle/20.500.12065/47452024-02-24T03:02:09Z2023-01-01T00:00:00ZNumerical investigation of the impact of injectors location on fuel mixing in the hifire 2 scramjet combustor
Palateerdham, S.K.; Phaneendra Peri, L.N.; Ingenito, A.; Vashishtha, A.
In scramjets, the position and direction of the injectors plays a crucial role for fuel/air mixing
and combustion efficiency. Fuel injection is still a potential topic of research to be addressed, in
fact an effective fuel injection strategy is critical for increasing the streamwise vorticity that has
been found to be the main responsible for the fuel-air mixing in compressible flows. In fact, the
position and the direction of the fuel injectors, the presence of a cavity scramjet has a critical
influence on the density and pressure gradients, and consequently on the baroclinic term that
is a source of vorticity. In this regard, this research wants to investigate the nature of the mixing
in supersonic flows, investigating the contribution between the streamwise and stretching
component for the vorticity. Numerical modelling of supersonic combustion using Large Eddy
Simulations was carried out in HIFiRE 2 Scramjet to better understand the physics of the
combustion and mixing.
2023-01-01T00:00:00ZNumerical study of oblique detonation wave control for fuel blendsKore, RushikeshVashishtha, Ashishhttps://research.thea.ie/handle/20.500.12065/45382023-06-20T03:00:48Z2023-01-01T00:00:00ZNumerical study of oblique detonation wave control for fuel blends
Kore, Rushikesh; Vashishtha, Ashish
The current study is motivated to develop control strategies for oblique detonation wave formation on a finite length wedge in a premixed methane-air mixture. The effectiveness of hydrogen blends (0 - 100%) to methaneair premixed mixture (at 300 K) on Chapmann Jouguet (CJ) detonation and oblique detonation wave formation are analyzed for different pressures (20 kPa - 100 kPa) and incoming velocities (2.4 - 3.2 km/s) by using 1-D Zeldovich-von Neumann-Doering (ZND) calculations. It was found that induction length and induction time reduces with higher blends of hydrogen in CJ-ZND analysis as well as oblique detonation wave ZND analysis. Similar effects are observed by adding small amount of reaction promoters (H2O2 or O3) as additives up to 15000 PPM. The two-dimensional numerical simulations for the oblique shock wave (OSW) to oblique detonation wave (ODW) transition for different blends and additions in fuel-air mixtures are performed for wedge at angle θ = 26◦ for incoming flow velocity of 2800 m/s, pressure of 20 kPa and temperature of 300 K. The unsteady reactive Navier-Stokes RANS equations are solved with adaptive grid refinement and robust SAGE chemistry solver on CONVERGE platform using reduced version of GRI mechanism along with ozone sub-chemistry. Two dimensional simulations confirms smooth transition with initiation length 1 cm for stoichiometric hydrogen-air and no ODW formation for methane-air premixed mixtures for 10 cm wedge length. It is also found that 50% hydrogen blending and 10000 PPM of ozone addition to stoichiometric methane-air mixture can establish ODW with initiation lengths of 3.9 cm and 4.0 cm, respectively on a finite length wedge.
2023-01-01T00:00:00Z