Investigation of a dual-stage high velocity oxygen fuel thermal spray system

Khan, Mohammed N.; Shamim, Tariq

doi:10.1016/j.apenergy.2014.03.075

Cited by 28 publications

(27 citation statements)

References 18 publications

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“…Thus, the particle temperature (dashed red line) from EDM comes close to that of EDC (dashed blue line). It can be concluded that the EDC theory better represents the nature of problem in the HVOF system since previously utilized turbulence limiting combustion models suffered lack of accuracy by under predicting the particle temperature (Ref 8,19,26). Figure 5(b) shows that for both stoichiometric and rich mixtures, EDC model predict the gas velocity around 100 m/s higher than those of EDM in the barrel.…”

Section: Edc Model Versus Edmmentioning

confidence: 95%

Effects of Combustion Model and Chemical Kinetics in Numerical Modeling of Hydrogen-Fueled Dual-Stage HVOF System

2019

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The present work examines the effect of utilizing different combustion models and chemical kinetics in predicting the properties of gas and particle phases in a hydrogen-fueled, dual-stage high-velocity oxy-fuel (HVOF) thermal spray system. For this purpose, effects of two combustion models, eddy dissipation concept (EDC) and eddy dissipation model (EDM), on the temperature and velocity fields in the system are studied. The computations using EDC model are performed for detailed and reduced chemical kinetics and for a range of mixture from lean to rich. It is found that EDC with multi-step reaction mechanism predicts higher temperatures for the flow and particle in the warm spray system. In contrast to EDC, the EDM with one-step global reaction shows extra heat release outside the HVOF barrel for rich mixtures which leads to unphysical higher prediction of particle temperature. The simulations using EDC model with detailed and reduced chemical kinetics show some exothermic reactions in converging-divergent nozzle of the system. The heat release from these reactions has profound impacts on the flow and particle temperatures and affects the gas dynamic behavior of flow considerably. Finally, it is discussed that moving toward rich mixtures is more reliable way to control the particles temperature.

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Section: Edc Model Versus Edmmentioning

confidence: 95%

Effects of Combustion Model and Chemical Kinetics in Numerical Modeling of Hydrogen-Fueled Dual-Stage HVOF System

2019

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“…This equation has also been used to investigate turbulent reactive flow in the single HVOF and dual stage HVOF (e.g. [16,22,26,28,30,31,43]). For single HVOF, turbulent…”

Section: Gas Phase Dynamicsmentioning

confidence: 99%

“…Khan and Shamim [30] also investigated the influence of some geometrical parameters in a dual-stage HVOF system and reported that an increase in the combustion chamber diameter or length leads to a decrease in temperature and velocity of particles. They [30] also reported that increasing the length of mixing chamber leads to an increase in the gas phase residence time in the mixing chamber and results in better mixing between the hot gases and nitrogen. It causes a significant decrease in the particle temperature.…”

Section: Introductionmentioning

confidence: 98%

“…Hence, numerical techniques are effective tools and can provide an insight into the underlying momentum and heat transfer mechanisms [24,25]. This further helps to improve the efficiency of HVOF and warm spray coatings by optimizing all of the effective design parameters such as C-D nozzle geometry, fuel/oxygen ratio, particle size and so on [16,[23][24][25][26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

“…It causes a significant decrease in the particle temperature. Increase in the diameter of C-D nozzle exit, however, reduces the particle velocity and increases its temperature [30].…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation of dual-stage high velocity oxy-fuel (HVOF) thermal spray process: A study on nozzle geometrical parameters

Jafari

Emami

Mahmoudi

2017

Applied Thermal Engineering

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The present study takes the advantage of computational fluid dynamics (CFD) methods to model steady-state, two-dimensional, axisymmetric, turbulent, compressible and combusting flow in a dual-stage high velocity oxy-fuel (HVOF) thermal spray system. The Eulerian method is used to solve the continuum gas phase and the Lagrangian method is utilized for tracking the particles. The effects of particle loads on the continuous gas phase are included in the simulation. Thus, compared to the previous studies, we investigate the influence of coupling between the particle and gas phases in modeling of the dual-stage HVOF process. It is found that decouple modeling of the particle and the continuous phase causes a significant error in velocity of particle at the impact moment, even for low powder particle loading. We further investigate the effects of four geometrical parameters on the behavior of gas phase and consequently the particle phase. Results also show that the turbulent intensity of flow at different sections of the warm spray process is the most important factor determining the radial distribution of nitrogen and temperature in the barrel. It also determines the radial distribution of oxygen in the free jet outside of the barrel. It is further found that reduction of the first nozzle diameter and increasing the length of the divergent section (for a fixed divergent angle) of the convergent-divergent nozzle reduce the particle temperature while these changes do not affect the particle velocity. In other words, changing these geometrical parameters has a desirable effect on the particle temperature without causing an undesirable change on the particle velocity.

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