Influence Of Particle Loading Research Articles

Experimental Investigation on Atomization of JP-10 Slurry Jets Containing Boron Nanoparticles

The present work aims to experimentally investigate the atomization of JP-10 based slurry jets containing boron nanoparticles. A coaxial airblast injector is used to atomize the slurry fuel. Different injector operating conditions are realized by varying the air and the fuel flow rates through the atomizer. For each case, different particle-to-fuel mass loading ratios ϕ (equal to 0, 5, 10, and 20%) are investigated. Time-resolved imaging is performed near the nozzle exit and 30Dl downstream of the injector exit to visualize the primary liquid jet breakup process and the resulting spray droplets, respectively. The instantaneous jet breakup length, droplet size, and velocity are obtained by processing the raw images. The influence of particle loading on the mean and fluctuations of jet breakup length, droplet size, and droplet size/velocity correlation is investigated in detail. The results highlight degradation in atomization quality for higher particle loading ratio in the base fuel. A monotonic increase in the mean jet breakup length with particle loading ratio is identified. The Sauter mean diameter increases by about 100% when ϕ is increased from 0 to 20%. It is found that ϕ must be accounted for, in addition to conventional nondimensional numbers, in the experimental correlations for jet breakup length and droplet size for nanofuel slurry.

Evolution of pressure drop across electrospun nanofiber filters clogged by solid particles and its influence on indoor particulate air pollution control

Because of the relatively low pressure drop and high particle removal efficiency, nanofiber filter media can be potentially used for indoor particulate air pollution control. However, the influence of particle loading on the long-term performance of nanofiber filters in indoor particle control has not been well studied. This study first experimentally investigated the relationship between the pressure drop and solid particle loading mass for 42 nanofiber filter samples under various face velocities. The results show that the air resistance coefficient increased with the solid particle loading mass for the nanofiber filter media. Furthermore, the air resistance coefficient was positively associated with the face velocity, as a higher air velocity tended to make the particle cake tighter with higher resistance. Based on the experimental data, a semi-empirical equation was developed for predicting the pressure drop under different particle loading masses and face velocities. The developed semi-empirical model was then used to assess the long-term performance of an air cleaner equipped with nanofiber filter media in indoor PM2.5 control. The case study demonstrated that an air cleaner equipped with nanofiber filter media could effectively control indoor PM2.5, but the lifetime of the nanofiber filter was shorter than that of traditional HEPA filters.

Development of PM0.1 Personal Sampler for Evaluation of Personal Exposure to Aerosol Nanoparticles

A PM0.1 sampler for the evaluation of the personal exposure to nanoparticles was designed based on a novel approach to a layered mesh inertial filter. Applications to practical environments would include roadsides and highly contaminated workplaces. The separation performances of PM0.1 sampler consisting of a layered mesh inertial filter and pre-separators for the removal of coarse particles were evaluated. The influence of particle loading on the pressure drop and separation performance, which is important from a practical standpoint, was also discussed. The novel personal sampler recorded a cutoff size of 100 nm with a small pressure drop of ~5 kPa. Through the combination of a layered mesh inertial filter for the PM0.1 and pre-cut impactors for the removal of huge or coagulated particles (PM1.4-TSP) along with a pre-cut inertial filter using webbed SUS fibers for the removal of fine particles (PM0.5-PM1.4), the present PM0.1 inlet for the personal sampler was practical for the chemical analysis of collected particles. This sampler was proven effective even under the limitations of a small-capacity portable battery pump, which was rated at less than the minimum change for separation performance. The novel PM0.1 personal sampler is compact and lightweight (under 1 kg including a portable battery pump), which is important for the practical application of a personal sampler.

Development of a high-volume air sampler for nanoparticles.

As a tool to evaluate the characteristics of aerosol nano-particles, a high-volume air sampler for the collection of nano-particles was developed based on the inertial filter technology. Instead of the webbed fiber geometry of the existing inertial filter, wire mesh screens alternately layered using spacing sheets with circular holes aligned to provide multi-circular nozzles were newly devised and the separation performance of the filter was investigated experimentally. The separation performance was evaluated for a single-nozzle inertial filter at different filtration velocities. A webbed stainless steel fiber mat attached on the inlet surface of the developed inertial filter was discussed as a pre-separator suppressing the bouncing of particles on meshes. The separation performance of a triple-nozzle inertial filter was also discussed to investigate the influence of scale-up on the separation performance of a multi-nozzle inertial filter. The influence of particle loading on the pressure drop and separation performance was discussed. A supplemental inlet for the nano-particle collection applied to an existing portable high-volume air sampler was devised and the consistency with other types of existing samplers was discussed based on the sampling of ambient particles. The layered-mesh inertial filter with a webbed stainless steel fiber mat as a pre-separator showed good performance in the separation of particles with a d p50 ranging from 150 to 190 nm keeping the influence of loaded particles small. The developed layered-mesh inertial filter was successfully applied to the collection of particles at a d p50∼ 190 nm that was consistent with the results from existing samplers.

Effects of PZT particle-enhanced ply interfaces on the vibration damping behavior of CFRP composites

In this study, vibration damping behavior of carbon fiber reinforced polymer composites was investigated when ply interfaces were enhanced by lead zirconate titanate (PZT) particles. The influence of particle loading and carbon black coating of particles was analyzed using the dynamic mechanical analysis. When plain PZT particles were distributed in the ply interfaces, the loss factor increased but suddenly dropped with increased particle loading, producing a threshold effect. As the loss factor represents the joule heat of electric current between PZT particles and carbon fibers, the sudden drop implies that there exists incomplete connectivity. To demonstrate the effect of incomplete connectivity, plain PZT particles were coated with carbon black of various weight fraction and the experiments were repeated. The results show there exists an optimal coating ratio of carbon black where the loss factor reaches its maximum value. When the optimal coating was applied to plain PZT particles, the loss factors of composites continuously increased, eliminating the threshold effect.

Development of a Personal Sampler for Evaluating Exposure to Ultrafine Particles

Evaluation of the exposure of humans to ultrafine, airborne particles is an important aspect of health in the workplace, especially in cases where nano-particles are present. However, portable sampling devices for efficiently collecting ultrafine particles in a worker's breathing zone are not readily available. The present study describes the design and development of a portable sampler for collecting particulates in the breathing zone, as a possible tool for this purpose. The design is based on the use of an ”Inertial Filter” to separate various-sized nano-order particles. Inertial filters consisting of SUS fiber felt (fiber diameter 5.6-13.5 μm) placed in circular nozzles (3-6 mm diameter with 4.5 mm length) were used. To achieve the smallest dp50 under the allowable pressure drop of a portable pump, the influence of fiber loading on separation performance and pressure drop were investigated. The influence of particle loading was also examined in relation to pressure drop and separation performance. The smallest dp50 under the allowable pressure drop (5.7 kPa at 6 L/min) for the battery pump employed was ~140 and 200 nm respectively for SUS fibers of 5.6 and 9.8 μm diameter (particle volume fraction ~0.013). The change in separation performance due to particle loading was confirmed to be acceptable for use under the present conditions. Under these conditions, a sufficient amount of particles can be collected for chemical analyses, e.g., particle-bound PAHs after 6-8 hours of sampling. Hence, the developed sampler has the potential for use in evaluating exposure to ultrafine particles in the breathing zone in the workplace.

The mechanism of high temperature erosion of coated superalloys

Diffusion and overlay coatings are now widely used for modern gas turbine parts such as nozzle guide vanes and turbine rotor blades. Problems are still encountered, however, when such components operate in environments where significant levels of particulates are present in the hot gas stream. The nature of these particulates depends on the service environment and may include sand-silicates, fly ash, sea salt and pyrolytic carbon. This paper highlights the significant parameters that control the mode of degradation and, in particular, the influence of particle loading, impact energy, temperature, scale morphology and composition on the deformation characteristics of both the surface oxide scale and coating. The erosion degradation mechanisms have been identified and a Monte Carlo model of the erosion-corrosion process developed, which is applicable to typical gas turbine service environments.

Numerical Calculations of the Breakup of Highly Loaded Slurry Jets

A complete numerical calculation procedure for predicting the effects of mass loading and particle diameter on laminar slurry jet breakup in a low velocity, coaxial gas stream has been developed. The method is based on the Volume of Fluid technique for the Navier-Stokes equations. The severe restrictions involved in earlier treatments have been relaxed. The influence of particle loading on liquid phase density and the influence of particle spacing on drag are included. The particular case considered is a slurry with a methanol liquid phase with aluminum oxide beads in order to compare with some related experimental results. The methanol liquid in the slurry is vaporized due to mass transfer in the gas stream. The variation of the instantaneous jet shape of the methanol slurry jet at low loadings is generally similar to that of an all-liquid methanol jet, but the final shapes at breakup are different. In the region of low mass loading (up to 20 percent), the effects of mass loading are to stabilize the interface and increase the breakup time of the slurry jet with increasing mass loading. Above that region of mass loading (more than 20 percent), the effects of mass loading are to destabilize the interface and decrease the breakup time of the slurry jet with increased mass loading. At the same mass loading condition, a slurry jet with large diameter particles has a more stabilizing effect than one with small diameter particles. Therefore, a slurry jet with higher mass loading and smaller diameter particles breaks up faster.