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Laser Surface Micro/nano Patterning for Improving Aerodynamic Performance

Otanocha, Omonigho Benedict

[Thesis]. Manchester, UK: The University of Manchester; 2016.

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Abstract

The use of ultrafast lasers in material surface engineering has gained pre-eminence in recent years. This is due to optimal utility arising from their versatility, better process control, repeatability and high precision fabrication, without need for post processing. Reported in this thesis are experimental results on the use of picosecond laser to produce micro-patterns on cyclone components and their effects on flow characteristics. Results show that micro- dimples achieved reduction in dust accumulation within a multi-cyclone system considered, up to 78%. These micro-dimples when applied on the cyclone roof effected a 3% reduction in inlet velocity and 5% reduction on the dynamic pressure across the cyclone, without dust introduction. Results support the possibility for energy savings, without compromise on cyclone overall separation efficiency. Findings further demonstrated the effects of micro-riblets on cyclonic airflow at the wall boundary. Research outcomes supported the view that surface roughness of the cyclone roof could contribute on its dust separation capacity. Injection moulding was used to produce bumps on ABS plastic materials utilising picosecond laser machined micro-dimples on H13 tool steel. A statistical model detailing the interactions between the critical factors involved with picosecond laser interaction with H13 for micro-patterning was proposed. Critical factors identified were laser fluence, scanning speed and number of laser scans. In addition, results demonstrated the suitability of predicting depth of 40 – 100 µm for H13 tool steel, with 96% accuracy. The findings in this research could be explored to develop embedded micro/nano-wires within riblets through injection moulding, to effect electrically biased charging within the internal walls of a cyclone to aid dust separation processes.

Keyword(s)

Laser surface modification cyclone dust adhesion aerodynamics H13 steel Holographic diagnostics Laser processing Surface engineering Injection moulding