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.

Influence of SiC particle size on the structure and tribological properties of Ni-Co composites

Abstract: Ni–Co composites incorporated with SiC particles of nano and micron size were produced by electrodeposition. The effect of cobalt content on the particle incorporation, microhardness, surface morphology and tribological behaviour has been studied. The Ni rich Ni–Co composite exhibited enhanced microhardness values. However, no appreciable increase in the microhardness was observed for Co rich Ni–Co–SiC composites. Scanning electron microscope, energy dispersive X-ray analysis and X-ray diffraction studies were used to characterize the coatings. A change in surface morphology, phase structure and SiC incorporation was observed with increase in cobalt content. Pin-on-disc tribo tester was employed to study the wear and friction behaviour of the Ni–Co–SiC coatings. The tribo studies indicated that the wear volume loss was less for micron SiC reinforced Ni–Co composites compared to nano SiC reinforced composites. However, no appreciable variation in the coefficient of friction was observed for both Ni rich and Co rich Ni–Co–SiC composites.

Mode detection with an optimised array in a model turbofan engine intake at varying shaft speeds

Abstract: Modal measurement techniques in engine intakes have been used previously to analyse the generated fan noise. A proven method is to use a wall-mounted array of Kulite transducers and operate the (model) turbofan under constant shaft speeds. A drawback of this method is the large number of (expensive) microphones and acquisition channels needed to obtain complete m-mode spectra at high engine orders. Furthermore, to get a full scan of the m-mode spectra as a function of shaft speed, many measurements are required. The issue of the large number of microphones was addressed by using a sparse array instead of an equidistant array. An array optimisation technique, similar to a technique used for the design of phased microphone arrays for sound source localisation, was used to define such a sparse intake array. This array consists of 100 Kulites and is able to determine without aliasing the modal spectrum from m = -79 to m = -1-79, which is appropriate to determine the modal content up to 3 BPF of a modem turbofan. This array was tested in a Rolls-Royce model fan rig at Ansty as a part of the RESOUND project. A new digital data-acquisition system made it possible to simultaneously and continuously record the Kulite pressure data as the engine speed was varied continuously from idle to maximum speed or vice versa, with each acceleration/deceleration lasting for a period of 9 minutes. Time histories of the Kulites were processed giving power spectra of the engine orders, which revealed the rotor locked tonal components. For each rotor revolution, a Discrete Fourier Transform was applied and, after averaging over a number of revolutions, the m-mode spectra were determined. In this way, a full modal scan with respect to shaft speed in a very limited testing time was obtained. Paper presented at the 7th AIAA/CEAS Aeroacoustics Conference, 28-30 May 2001, Maastricht, The Netherlands.