Measurement of the Particle Velocity in a HVOF Spray with PIV Under Industrial Conditions
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JTTEE5 21:882–886 DOI: 10.1007/s11666-012-9772-z 1059-9630/$19.00 Ó ASM International
Measurement of the Particle Velocity in a HVOF Spray with PIV Under Industrial Conditions Humberto Chaves, Stefan Herbst, and Christoph Skupsch (Submitted October 7, 2011; in revised form January 31, 2012) The particle velocity and the particle temperature are two of the most important parameters influencing the deposition process of high-velocity oxy-fuel (HVOF) spraying. This article addresses the application of particle image velocimetry to the measurement of the 2D particle velocity distribution in the flame of an industrial burner in a spraying booth under industrial conditions. Therefore, the measurement equipment has to be protected from overspray. Moreover, the low particle number density of HVOF sprays requires a technique called average correlation for image evaluation. The effect of the variation of process parameters, such as oxygen flow rate and mass loading of the flame, on the particle velocity is discussed.
Keywords
HVOF, optical diagnostics, particle image velocimetry (PIV), particle velocity
1. Introduction The quality of a coating produced by high-velocity oxyfuel (HVOF) sprays depends on many factors such as the in-flight properties of the particles (e.g., their velocity, temperature, size, shape) as well as the properties of the substrate (e.g., temperature, stress, coating thickness (see e.g., Ref 1). An on-going effort is being made to develop sensors that can deliver data which can be used to control the spraying process (Ref 1). The main reason for this is that both the process parameters and the geometry of the gun—resulting from abrasion by the particles—can change over time. However, particle velocity and temperature vary at different positions in the jet depending on the process parameters. Thus, monitoring of particle properties at one single location in the jet is not sufficient to describe the complete particle jet (Ref 2). Many pointmeasurement sensors have been developed, which not only deliver particle velocity but also size and shape (e.g., Particle Shape Imaging, Ref 3). These methods use a 3D translation stage to move the small measurement volume relative to the spray. Although the time needed to measure at one point is in the order of 20 ms, the time needed to measure a predefined measurement raster can last up to 15 min, (Ref 3). Only the system developed by Vattulainen et al. (Ref 4), now commercially available (Spray Watch), covers a volume (34 9 27 9 25 mm3) sufficient to Humberto Chaves, Stefan Herbst, and Christoph Skupsch, Institute of Mechanics and Fluid Dynamics, Technical University of Freiberg, Freiberg, Germany. Contact e-mail: Humberto. [email protected].
882—Volume 21(5) September 2012
measure the width of the spray. All others measure much smaller volumes. Consequently, a method that measures particle velocity simultaneously at many locations is preferable. The present article addresses the measurement of particle velocity using particle image velocimetry (PIV),
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