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2127 |
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Tuesday, May 04, 2010, Moor Room 4:40 PM HVOF 2 |
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Development of a low temperature, air fuel (LTAF) thermal spray gun |
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Rajeev Dhiman / Centre for Advanced Coating Technologies, University of Toronto, Canada Farhad Farhadi / Simulent, Inc, Canada Larry Pershin/ Dept. of Mechanical & Industrial Engg, University of Toronto, Ontario Sanjeev Chandra/ Dept. of Mechanical & Industrial Engg, University of Toronto, Ontario Javad Mostaghimi*/ Dept. of Mechanical & Industrial Engg, University of Toronto, Ontario |
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This paper presents the development of a new thermal spray gun for the so-called warm spraying process in which powder particles are not melted but heated to temperatures much higher than those typically found in a cold spray process. The increased heating leads to a reduction in the particle impact velocity required to deposit the coating and hence reduces operating cost. The new gun utilizes methane-air combustion for particle heating and features a swirl-type combustion chamber to create a turbulent mixture of the fuel and oxidizer for efficient combustion. Powder is fed axially into the combustion chamber in order to achieve high particle velocities. To control particle temperature independently, combustion gases can be diluted by adding additional nitrogen gas through two radial ports provided in the gun. A converging-diverging nozzle with a downstream cylindrical barrel accelerates the burnt gases to supersonic velocities. The design of the nozzle and barrel was optimized using numerical simulations. Mass flow rates of methane, air, and nitrogen were calculated using energy balance, stoichiometric combustion, and nozzle flow rate equations. The gun measures about 3? in diameter and 10? in length. The gun is designed to operate up to 200 kW and is water-cooled. Experiments have been conducted to test the performance of the new gun. Measured gas and particle temperatures are compared with numerical simulations. |