Effect of Stefan flow on the drag force of single reactive particle surrounded by a sea of inert particles

Investigation of the Coupling Schemes between the Discrete and the Continuous Phase in the Numerical Simulation of a 60 kWth Swirling Pulverised Solid Fuel Flame under Oxyfuel Conditions

“…Due to an outflow from the particle through the release of volatile gases, a decrease in drag force on a reactive single particle was observed by Farazi et al [12] and Jayawickrama et al [14]. The same conclusion was drawn for the drag force applied to a single reactive particle surrounded by inert particles [17]. For a single burning particle (only char without volatile gases), Zhang et al [15] found that the drag force of a reactive char particle is higher than the one including volatile gases.…”

“…The devolatilisation of a reactive particle not only causes an outflow from the particle leading to smaller drag forces of the particle [14] but also suddenly accelerates the particle, which is referred to as "rocketing" [16]. Such effects can been analysed for single reactive particles using, e.g., particle-resolved direct-numerical simulation (DNS) [12][13][14][15]17] or advanced experimental methods [16], thereby identifying the coupling schemes between the phases, such as in [13]. In this study, however, the interactions between the phases are not considered in particle resolution, but a general overview of the necessary coupling schemes between the phases for the combustion of pulverised solid fuels is provided.…”

Direct Numerical Simulation of Fluid Flow and Heat Transfer of a Reactive Particle Layer with Stefan Flow in Supercritical Water

“…It can achieve superior efficiency and significantly reduce the pollutants generated in the traditional gasification and combustion process. , For the gas–solid reactive flows in the SCWG reactors, the surface material of coal or biomass particles is heated and gasified to form a mass flow that is perpendicular to the particle surface and reacts with the surrounding fluid. The mass exchange between particles and surrounding fluid is called Stefan flow, and the momentum, mass transfer, heat transfer, and chemical reactions between particles and fluid are coupled and affected by Stefan flow, making the particle–fluid–particle interactions more complicated. − The impact of Stefan flow on the gas–solid particle reacting flow is further reflected in hydrodynamic behavior and reaction efficiency. − In the reactor, the drag coefficient ( Cd ) and Nusselt number ( Nu ) are two crucial characteristics of particle force and heat transfer efficiency. , Pioneer scholars’ in-depth research and fitted valuable empirical formulas for inert particles in the cold environment can effectively guide industrial production. , However, the previous empirical formulas of the inert particles are no longer applicable for the reactive particles in the high-temperature and reactive environment, and a thorough analysis and complete understanding of the particle–SCW–particle interaction combined with the influence of the Stefan flow, such as heat transfer and flow characteristics, are urgently needed for the scale-up, design, and optimization of the reactor for industrial application.…”

The Effects of Stefan Flow on the Flow Surrounding Two Closely Spaced Particles

“…There are few studies dedicated to the effects of a Stefan flow on the boundary layer at closely spaced particles in a particle-fluid flow (Chen et al, 2021;Du et al, 2022;Wang et al, 2022). Chen et al (2021) studied the effect of a Stefan flow on the flow past a random array of spheres.…”

“…This happens due to suppression of the boundary layer thickening created by an outward Stefan flow compared to an isolated particle. Du et al (2022) have studied the effect of Stefan flow on the drag force of a single reactive particle surrounded by inert particles. In addition to the observations of Chen et al (2021), Du et al (2022) have observed that the reduction of the drag force decreases as Re increases and variation of Re has negligible effects on the reacting particle drag coefficient (𝐶 𝐷 ) at the solid volume fraction above 0.5.…”