Modeling and Optimization of Combustion Assisted Thermal Spray Systems

  • Mohammed Nazeer ul Hasan Khan

Student thesis: Master's Thesis

Abstract

The high velocity oxygen fuel (HVOF) thermal spray coatings are used to protect the surfaces from deterioration. The base material surface properties can be modified to achieve the longevity of the product. Besides spraying material, the coating quality depends greatly on the gas and particle dynamics, particularly for a temperature sensitive material such as titanium and copper. Titanium and its alloys are widely used in aircraft manufacturing because of its high strength to weight ratio and excellent corrosion resistance and are known to be the excellent candidates for aerospace applications. As the temperature of the gas phase is high, the material gets melted and oxidized before it reaches the substrate. To avoid this problem, a dualstage thermal spray system has been developed for coating temperature sensitive materials. This process involves making coatings by high velocity impact of powder particles heated to temperatures below their melting point. The present study investigates the effect of various geometric parameters of a dualstage thermal spray gun such as the dimensions of combustion chamber, converging nozzle, mixing chamber and the converging-diverging nozzle, by developing a comprehensive mathematical model. The objective is to develop a predictive understanding of various design parameters. In addition to the geometrical parameters, the present study also investigates the influence of various operating parameters such as the reactant and coolant mass flow rates, fuel/oxygen ratio, preheating of reactants and the particle size on a dual-stage thermal spray gun iii performance. The results demonstrate the advantage of two stage system over single stage system especially for the deposition of temperature sensitive materials. The operating parameters also affect the coating properties. Hence, an optimization study has also been performed on a single stage system by using the data available in the literature. The study allowed analysis of the individual and the combined effects of the operating parameters on the coating properties. These studies have shown the advantage of using statistical methods for obtaining the correlations between the parameters and the coating properties.
Date of Award2013
Original languageAmerican English
SupervisorTariq Shamim (Supervisor)

Keywords

  • Internal Combustion Engines; Computer Simulation; Mathematical Optimization.

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