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http://research.thea.ie:80
The Research@THEA digital repository system captures, stores, indexes, preserves, and distributes digital research material.2024-03-29T11:51:58ZTest
https://research.thea.ie/handle/20.500.12065/4772
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2024-01-01T00:00:00ZTargeting bacterial nanocellullose properties through tailored downstream techniques
https://research.thea.ie/handle/20.500.12065/4771
Targeting bacterial nanocellullose properties through tailored downstream techniques
Da Silva Pereira, Everton Henrique; Mojicevic, Marija; Tas, Cunety Erdinc; Lanzagorta Garcia, Eduardo; Fournet, Margaret Brennan
Bacterial nanocellulose (BNC) is a biodegradable polysaccharide with unique properties that make it an attractive material for various industrial applications. This study focuses on the strain Komagataeibacter medellinensis ID13488, a strain with the ability to produce high yields of BNC under acidic growth conditions and a promising candidate to use for industrial production of BNC. We conducted a comprehensive investigation into the effects of downstream treatments on the structural and mechanical characteristics of BNC. When compared to alkaline-treated BNC, autoclave-treated BNC exhibited around 78% superior flexibility in average, while it displayed nearly 40% lower stiffness on average. An SEM analysis revealed distinct surface characteristics, indicating differences in cellulose chain compaction. FTIR spectra demonstrated increased hydrogen bonding with prolonged interaction time with alkaline solutions. A thermal analysis showed enhanced thermal stability in alkaline-treated BNC, withstanding temperatures of nearly 300 °C before commencing degradation, compared to autoclaved BNC which starts degradation around 200 °C. These findings provide valuable insights for tailoring BNC properties for specific applications, particularly in industries requiring high purity and specific mechanical characteristics.
2024-03-02T00:00:00ZNumerical studies of ram-air Intake for near-earth satellites
https://research.thea.ie/handle/20.500.12065/4762
Numerical 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 propellants
https://research.thea.ie/handle/20.500.12065/4761
Studying 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.
2024-01-01T00:00:00Z