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

Sobhan Emami,Hamed Jafari,Yasser Mahmoudi

doi:10.1007/s11666-019-00826-8

Abstract

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.

Highlights

The application of high-velocity oxygen-fuel (HVOF) thermal spray technique has been growing in the last two decades in many industries such as aerospace, automotive, oil and petrochemical, power generation, electronic, and medical science due to its excellent coating performance
Since there is no published experimental or numerical data in the literature for the hydrogen-fueled warm spray gun, for validation purpose we model a propylene-fueled warm spray system introduced by Khan and Shamim (Ref 26) using eddy dissipation model (EDM) combustion model and k–e RNG turbulence model
As it can be seen, a very good agreement between the two results is achieved. As it is mentioned by Tabbara et al (Ref 25), using an advanced turbulence model such as Reynolds-stress turbulence model (RSM) is preferred in numerical simulations of the warm spray

Summary

Introduction

The application of high-velocity oxygen-fuel (HVOF) thermal spray technique has been growing in the last two decades in many industries such as aerospace, automotive, oil and petrochemical, power generation, electronic, and medical science due to its excellent coating performance. The system powered by gaseous fuel (like hydrogen, propylene, propane, acetylene and natural gas) or liquid fuel (like kerosene) In this system, the injected particles are accelerated and heated through a subsonic and supersonic combusting gas flow and hit the substrate, which is placed at around [200-400] mm from nozzle exit (Ref 1). In HVOF system, desirable change in temperature can cause an undesirable change in other characteristics (e.g., velocity of particle and oxygen content of flow) (Ref 3). These shortcomings have more adverse impact on the phase-sensitive and temperature-sensitive materials like titanium and copper

Methods

Results

Conclusion