Modeling the Effects of Concentration of Solid Nanoparticles in Liquid Feedstock Injection on High-Velocity Suspension Flame Spray Process

Abstract

This paper presents the effects of the concentration of solid nanoparticles in the liquid feedstock injection on the high-velocity suspension flame spray (HVSFS) process. Four different concentrations of solid nanoparticles in suspension droplets with various droplet diameters are used to study gas dynamics, vaporization rate, and secondary breakup. Two types of injections, viz. surface and group, are used. The group-type injection increases the efficiency of droplet disintegration and the evaporation process and reduces the gas cooling. The initiation of the fragmentation process is difficult for small droplets carrying a high concentration of nanoparticles. Also, smaller droplets undergo rapid vaporization, leaving clogs of nanoparticles in the middle of the barrel. For larger droplets, severe fragmentation occurs inside the combustion chamber. For a higher concentration of nanoparticles, droplets exit the gun without complete evaporation. The results suggest that, in coating applications involving a higher concentration of nanoparticles, smaller droplet sizes are preferred.

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

“…The premixed oxygen/fuel (O/F) is injected into the DJ2700 gun; the resulting hot combustion gases are accelerated inside the convergent-divergent (C-D) nozzle and flow through the barrel section towards the exit of the gun. The droplets' injection mass flow rate and injection velocity are selected on the basis of previous work [50][51][52][53] ( Table 1). …”

“…The first stage is the aerodynamic breakup of droplets, as the slow moving droplets are entrained into the jet and accelerate in the high-velocity gas stream. Based on size and thermophysical properties of the liquid and their interaction with the surrounding gas, droplets undergo severe deformation and then breakup into smaller droplets [50][51][52][53]. Here, different injection types are studied, namely surface-type injection (STI), group-type injection (GTI) and effervescent-type injection (ETI).…”

“…The EDM is also used to model nonpremixed combustion of ethanol vapours with remnant oxygen left from premixed (oxygen/propane) combustion [57][58][59]. The heat and mass transfer of the droplets with the continuous phase is modelled using three laws, as described in the previous work [50][51][52][53]60]. Detailed descriptions of the gas phase, discrete phase, breakup and combustion models are reported elsewhere [25,27,30,51,54,59,[61][62][63].…”

“…Detailed descriptions of the gas phase, discrete phase, breakup and combustion models are reported elsewhere [25,27,30,51,54,59,[61][62][63]. The employed mathematical models have been strongly tested against experimental and numerical data [50,[52][53][54]60,64,65], the test results are not repeated here for brevity. Only the detailed modelling equations for the ETI are presented here for a clear understanding in Section 2.1 [33,49].…”

“…Moreover, the temperature dependent pure liquid properties are incorporated, and curve-fitting procedures are applied in the required temperature range as in previous work [52,53,69] and not repeated here for conciseness. For each type of droplet injection (axial, angular and effervescent), different rates of evaporation and fragmentation have been detected.…”