National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Spray Characteristics of Swirl Coaxial Injector and Its Modeling

Abstract: The spray characteristics of a swirl coaxial injector was investigated experimentally, and the spray formation model was made using the theoretical analysis of a liquid film flow on the inner wall of a center post of the injector and the breakup model of a liquid film. The liquid film thickness at the injector exit was measured using a contact needle probe. The liquid film flow on the inner wall of the injector was analyzed theoretically. The empirical equations of the sheet breakup length and the sheet cone angle were deduced, and they were compared with the measurements. The liquid sheet breakup model was made using analyzed film thickness and sheet cone angle. The spray characteristics of a liquid sheet injected from a swirl coaxial injector were measured using the phase Doppler particle analyzer, and were compared with the numerical simulations. Nomenclature a* constant in eq.(l9) bconstant in eq.(l9) Cconstant in eq.(2l) dc diameter of gas core at liquid inlet as shown in Fig.2 de exit diameter of center post as shown in Fig.2 D" constant in eq.(22) Ds2 Sauter mean diameter Econstant in eq.(23) hliquid film thickness as shown in Fig.2 * Professor, Faculty of Science and Technology, Member AIAA § Graduate Student, Faculty of Science and Technology H Head, Kakuda Research Center, Senior Member AIAA # Researcher, Kakuda Research Center Copyright © 2001 The American Institute of Aeronautics and Astronautics Inc. All rights reserved. 1 h average liquid film thickness ho liquid film thickness at center post exit as shown in Fig.2 hiliquid film thickness at liquid inlet as shown in Fig.2 k^ cavity factor (=dc/de) Katomizer constant Llength of center post as shown in Fig.l Lbu breakup length of injected liquid sheet Mmass flow rate Pinjection pressure Qliquid volume flow rate per unit width Re" Reynolds number defined by eq.(lO) u" liquid velocity in x-direction Uliquid surface velocity in axial direction Uo liquid injection velocity at center post exit Ud droplet velocity Uiconstant liquid axial velocity at x=0 as shown in Fig.2 Ur relative velocity between air and liquid vliquid velocity in y direction xcoordinate along liquid stream line as shown in Fig.2 xo x at point where laminar boundary layer reaches film surface as shown in Fig.2 xt x at point where transition of boundary layer from laminar to turbulent occurs as shown in Fig.2 y coordinate perpendicular to x axis as shown in Fig.2 zcoordinate in axial direction (origin is at x=0) Zdistance from injector exit Greek Symbol asheet cone angle at z^O OCRsheet cone angle at z=L v" kinetic viscosity 0: azimuthal angle as shown in Fig.l pdensity a" surface tension t,'wave amplitude at liquid film breakup £o initial wave amplitude Subscript g gas 1" liquid American Institute of Aeronautics and Astronautics (c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. Nitrogen l 34> 0.81

Fibre Fraction Effects on Thermal Degradation Behaviour of GFRP, CFRP and Hybrid Composites

Abstract: The effects of fibre fraction on thermal degradation of composites containing glass, carbon and glass/carbon hybrid reinforcements in a bifunctional epoxy resin system were studied. Thermogravimetric technique was used to monitor the weight loss with the temperature. The degradation patterns so obtained were correlated with the fibre fraction of the composites.

Structural and mechanical properties of reactively sputtered TiAlC nanostructured hard coatings

Abstract: TiAlC nanostructured hard coatings have been deposited on Si(100) substrates by four-cathode reactive pulsed direct current unbalanced magnetron sputtering at various process conditions. The effects of Al and C on the compositional, mechanical and micro-structural properties of TiAlC coatings have been investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, atomic force microscopy and nanoindentation hardness tester. Furthermore, the effect of substrate bias on the surface morphology, micro-structure and mechanical properties of TiAlC coatings is examined in detail. Formation of Ti3AlC(111) phase along with inclusion of TiC and amorphous carbon phases has been confirmed by XRD and micro-Raman spectroscopy studies. The optimized TiAlC coating exhibited a maximum hardness of ~ 30 GPa and elastic modulus of 288 GPa. Analysis of the nanoindentation data indicated that the resistance to plastic deformation (H3/E*2) and elastic strain to failure (H/E*) decrease with C and Al contents in the TiAlC coatings, whereas, these properties increase with an increase in the substrate bias due to grain size refinement. Lastly, fracture toughness of TiAlC coating has also been calculated using a cube corner indenter and the optimized coating exhibited a maximum toughness of ~ 1.38 MPa m1/2 at a load of 50 mN.

Sub-wavelength waveguide properties of 1D and surface-functionalized SnO2 nanostructures of various morphologies.

Abstract: One-dimensional (1D) SnO2 sub-wavelength waveguides are a critical contribution to advanced optoelectronics. Further understanding of the surface defects and role of morphology in 1D SnO2 nanowires can help to better utilize these nanostructures more efficiently. For this purpose, three different nanowires (NWs), namely belts, cylindrical- and square-shaped structures were grown using SnO2 quantum dots as a precursor material. The growth process of these NWs is discussed. The nanobelts were observed to grow up to 3 mm in length. Morphological and structural studies of the nanostructures were also carried out. All NWs showed waveguide behavior with visible photoluminescence (PL) upon excitation with a 325 nm laser. This behavior was also demonstrated in tapered and surface-functionalized SnO2 NWs. While the tapered waveguide can allow for easy focusing of light, the simple surface chemistry offers selective light propagation by tuning the luminescence. Defect-related PL in NWs is studied using temperature-dependent measurements and a band diagram is proposed.