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.

LOX/LH2 Subscale Swirl Coaxial Injector Testing

Abstract: To obtain design technology necessary for the realization of large swirl coaxial injectors with high performance, multi-element combustors composed of 9-shear-coaxiaI or 9-swirl-coaxial injection elements were tested at a nominal thrust of 10 kN, a chamber pressure of 3.5 MPa, a mixture ratio of 4.5 to 7.5, and a hydrogen injection temperature of 40 to 50 K. Combustion performance, chamber pressure distribution, chamber heat load, and stability data for each injector were obtained and compared with each other with reference to the authors' single element results. Measured data showed a reasonable correspondence and the difference of combustion characteristics between the shear coaxial injector and swirl coaxial injectors was apparent

Acid Resistance of Glass Fibre Composites with Different Layup Sequencing Part II: Degradation Studies:

Abstract: The effects of sulphuric acid,concentration nd the sequential layup of glass fiber reinforcement on the diffusion behavior of glass epoxy composite laminates were studied. In all, composites of six d t f f h n t resin systems viz., general purpose polyester, bis phenol-A polyester, vinyl ester, LY 556 epoxy, and MY 750 epoxy resins, reinforced with differen1 layup sequencing consisting of chopped strand mar (CSM) and woven roving mat (WR) were exposed to ,sulphuric acid environments of different concentrations. The results of the study indicated that isophrhalic polyester resin exhibited maximum resistance to sulphuric acid while general purpose polyester resin performed relatively inferior. The diffusion phenomenon became anamalous as the concentration of the sulphuric acid increased. Among the layup sequences considered, composite specimens with CSM as the skin layers exhibited higher weight gain than those with WR as the skin layer;.

What was Learned from Numerical Simulations of F-16XL (CAWAPI) at Flight Conditions

Abstract: Nine groups participating in the CAWAPI project have contributed steady and unsteady viscous simulations of a full-scale, semi-span model of the F-16XL aircraft. Three different categories of flight Reynolds/Mach number combinations were computed and compared with flight-test measurements for the purpose of code validation and improved understanding of the flight physics. Steady-state simulations are done with several turbulence models of different complexity with no topology information required and which overcome Boussinesq-assumption problems in vortical flows. Detached-eddy simulation (DES) and its successor delayed detached-eddy simulation (DDES) have been used to compute the time accurate flow development. Common structured and unstructured grids as well as individually-adapted unstructured grids were used. Although discrepancies are observed in the comparisons, overall reasonable agreement is demonstrated for surface pressure distribution, local skin friction and boundary velocity profiles at subsonic speeds. The physical modeling, be it steady or unsteady flow, and the grid resolution both contribute to the discrepancies observed in the comparisons with flight data, but at this time it cannot be determined how much each part contributes to the whole. Overall it can be said that the technology readiness of CFD-simulation technology for the study of vehicle performance has matured since 2001 such that it can be used today with a reasonable level of confidence for complex configurations.

Decomposition behaviour of Kevlar 49 fibres: Part I. AtT≈T d

Abstract: The structural changes which accompany decomposition of Kevlar 49 fibres at T= 500xB0;C: and 550xB0;C, respectively, have been elucidated. At both these temperatures, cumulative thermal exposures of specific durations, tcum{T}, are required to result in decomposition. The conspicuous features which characterize isothermal decomposition of the fibres are: (i) progressive reduction and an eventual total loss in fibre crystallinity, (ii) progressive loss in weight, (iii) introduction of surface damages, (iv) introduction of hollowness, and (v) deterioration in tensile properties.