Computational simulation of liquid-fuelled HVOF thermal spraying

Abstract

a b s t r a c t a r t i c l e i n f oLiquid-fuelled high-velocity oxygen-fuel (HVOF) thermal spraying systems are gaining more attentions due to their advantage of producing denser coatings in comparison to their gas-fuelled counterparts. The flow through a HVOF gun is characterized by a complex array of thermodynamic phenomena involving combustion, turbulence and compressible flow. Advanced computational models have been developed to gain insight to the thermochemical processes of thermal spraying, however little work has been reported for the liquid-fuelled systems. This investigation employs a commercial finite volume CFD code to simulate the flow field through the most widely used liquid-fuel HVOF gun, JP5000 (Praxair, US). By combining numerical combustion and discrete phase models the turbulent spray flame is captured and the development of supersonic gas flow is revealed. The flow field is thoroughly examined by adjusting the nozzle throat diameter and combustion chamber size. The influence of fuel droplet size on the flame shame shape and combusting gas flow is also examined.

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

“…During the past 15 years, the eddy dissipation model has been usually used to simulate gaseous and liquid fuels combustion in the HVOF process and has been providing acceptable results (see [60][61][62][63][64][65][66][67][68][69]). In an interesting article, Kamnis and Gu [66] used different types of combustion models to simulate the HVOF system operated on liquid propane.…”

“…It should be noted that for some liquid fuels such as kerosene, droplets should be injected into the combustion chamber and their evaporation and combustion should be modeled. In the works of Kamnis and Gu [67] and Tabbara and Gu [68], the kerosene droplet combustion was simulated using the eddy dissipation model (the droplet breakup was not considered in these works [67,68]). Authors showed that the kerosene evaporation/combustion was dependent on the initial fuel droplet size.…”

Effects of angular injection, and effervescent atomization on high-velocity suspension flame spray process

“…The flow physics inside the HVOF torch is difficult to be studied experimentally, and hence, Computational Fluid Dynamics (CFD) techniques are widely used to understand this. Various models are implemented to understand the complex flow physics, combustion chemistry, flames, and jets formation, and propagation involved in the thermal spraying processes [22][23][24][25][26][27]. Li and Christofides [22,[28][29][30][31] highlighted the multi-scale behaviour of the overall process inside a HVOF thermal spray torch (Diamond Jet hybrid gun).…”

A study of liquid droplet disintegration for the development of nanostructured coatings

“…21 The liquid feedstock HVOF method has also been applied to experimentally manufacture Ceria-based electrolytes for solid-oxide fuel cells, where the flame limits the evaporation and decomposition of the feedstock compared to plasma spray alternatives, producing a low-porosity, smooth and defect free coating. 28,29 The reader may also refer to literature 30,31 for detailed simulation-based investigations concerning micron sized powder particles and process gas interactions in cold gas spraying and HVOF, respectively. Detailed images of the initial disintegration of liquid feedstock injection are provided in Ref.…”

“…A good overview of the combustion characteristics and supersonic flow field within the JP5000 have been previously documented. 28,29 The reader may also refer to literature 30,31 for detailed simulation-based investigations concerning micron sized powder particles and process gas interactions in cold gas spraying and HVOF, respectively. The work presented within the latter example applies multiscale modeling by combining steady-state combustion, particulate phase dynamics and heating, and rule-based stochastic methods, leading to the prediction and control of detailed and accurate coating microstructures.…”