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Different compositions of graphene oxide (GO) and detonation nanodiamond (DND) nanoparticles with API CH-4 engine oil were tested on a reciprocating wear tester at high contact pressure. Significant reductions in friction and wear were observed. Wear surfaces were characterized by a 3D profiler, scanning electron microscopy and energy-dispersive X-ray spectroscopy to determine the surface topography, film build-up composition, mechanism of nanoadditive-assisted friction reduction and wear reduction characteristics. The wear tests indicated that the original engine liner segments containing surface texture with oil retention potential significantly lose their micropeaks and valleys during the test. Even though the surface texture got disturbed, the presence of nanoadditives in the lubricant led to a reduction in the coefficient of friction. Considerable reduction in the roughness level of the wear track associated with the use of a nanolubricant was also explored through the 3D profiler analysis. The surface roughness of the wear track produced while using a nanolubricant with 0.5 mg/l of detonation nanodiamond nanoparticles was 66% lower than the roughness of the wear track obtained with the base oil. The nanolubricant suspended with 1 mg/l detonation nanodiamond nanoparticles achieved a lower coefficient of friction earlier and a combination of detonation nanodiamond and GO at 0.5 mg/l concentration achieved the lowest coefficient of friction and wear at the end of the test duration.

This paper discusses the performance enhancement of supersonic air intake model through the implementation of blunted leading edge to the cowl lip section of the model. A supersonic air intake model with sharp cowl leading edge is initially considered to numerically investigate its performance. Mach 3, supersonic intake flow through the base model has been simulated using commercial CFD package Ansys Fluent-15. Comparison of numerical predictions and experimental measurements is presented to demonstrate the correctness and accuracy of numerical frame work followed in the present study. Higher order spatial accuracy of the solver along with suitably refined mesh helped in accurate capturing of the flow field. Modification to the cowl lip is proposed as an effective method to improve the performance of the supersonic air intake. Two different blunted cowl leading edge geometries were investigated to identify the possible enhancement in performance parameters. Improvement in mass capture and combustion stability attained through the use of forward shifted blunt cowl leading edge is presented. It is also revealed through the present study that the blunt cowl leading edge can reduce the intensity of shock wave boundary layer interaction occurring at the isolator entry section. Deviation in total pressure recovery and flow distortion observed with different supersonic air intake models are also discussed with reasons for the same. This study demonstrates the scope of overall improvement in scramjet engine performance through the use of suitably positioned blunt cowl leading edge.

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