| Summary: | In the last few years a new method for surface preparation has evolved, namely thermo-abrasive
blasting. This technique utilises a high enthalpy thermal jet to propel abrasive particles.
The thermo-abrasive blasting gun, also called a thermal gun, is based on the principles of High
Velocity Air Fuel (HVAF) processes. Nozzles used for thermo-abrasive blasting are subjected to
thermal loading, wear and mechanical stresses. Therefore, the nozzle geometry and materials are
critical for reliable performance of a thermo-abrasive system. In this investigation, the thermal
stresses developed in the nozzle materials for thermo-abrasive blasting were analysed.
The analytical and the computational models of the thermo-abrasive gun and the nozzle were
developed. The computational fluid dynamics, thermal and structural finite element analyses
have been employed in this study. The nozzle materials investigated were tungsten carbide, hot
pressed silicon carbide, nitride-bonded cast silicon carbide and SIALON.
The simulation and experimental results show that the highest thermal stresses occur during the
first two minutes from the start of the thermal gun. However, thermal stresses are also high after
the system is shut off. The nozzle geometry was optimised, which provided high cleaning rates
with evidence of improved thermal loading, based on the experimental results.
A new design of the thermal gun and the ignition method associated with a HVAF system were
developed in this study.
It is also concluded that the computation fluid dynamic and the finite element technique can be
used to optimise the design of thermo-abrasive blasting nozzles. === Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.
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