Computer Vision in Analyzing the Propagation of a Gas–Gunpowder Jet

A method of mathematically processing the digital images of targets is developed. The theoretical and mathematical justification and the experimental validation of the possibility of estimating the amount of gunshot residue (GSR) and determining the GSR distribution over the target on the basis of its digital image is provided. The analysis of the optical density in selected concentric rings in the images reveals the radial dependence of soot distribution in the cross section of a gas–gunpowder jet. The analysis of the optical density in selected sectors of the circle reveals the angular dependence of the soot distribution in the gas–gunpowder jet cross section. It is shown that the integral optical density averaged over a selected area in the target image characterizes the mass of GSP deposited on it. It is possible to quantify the differences in the radial and angular distributions of the thickness of the GSR layer on various targets obtained both with the help of weapons of different types at the same distances and with the help of weapons of the same type at different distances, by calculating the distribution of optical density on their digital images.

Soot Distribution and Thermal Regeneration of Marine Diesel Particulate Filter

Particles from marine diesel engine exhaust gas have caused serious air pollution and human health. Diesel particulate filter (DPF) can effectively reduce particle emissions from marine diesel engines. The distribution and regeneration of soot in DPF are two important issues. In this paper, a mathematical model of a marine DPF was built up and the particle trap process and the regeneration dynamics were simulated. The results show that the cake soot mass concentrations during trap process increase linearly with the increase of the exhaust gas flows while the depth soot mass concentrations firstly increase linearly and then keep constant. Soot is mainly concentrated in the front and rear portion of the filter and less soot is in the middle. The soot distribution in the cake and depth layer shows the unevenness during the trap and regeneration process. The initial soot loadings have great effects on pressure drops and soot mass concentrations before regeneration, but little effect after regeneration. The exhaust gas temperature heated to 850 K can achieve 94% efficiency for the DPF regeneration. There is no obvious difference in pressure drops and soot mass concentrations between fast heating and slow heating. The heating duration of exhaust gas has an important impact on DPF regeneration.

The state-of-the-art of soot load estimation in diesel particulate filters: A review

Diesel particulate filter (DPF), as part of aftertreatment system of internal combustion engine, is considered to be the only feasible way to prominently lessen particle emissions under the requirement of today’s strict regulations such as Euro Ⅵ, US Tier 3 and China Ⅵ. This paper gives a brief introduction of the mechanism and regeneration approaches of DPF, with emphasis on soot load estimation inside the filters, which plays a vital role in formulating regeneration control strategy and ensuring exhaust systemic dependability. Various methods are covered according to different principles, including differential-pressure based methods, which are mostly used nowadays, novel model-based methods and also several newfangled soot sensors, which are progressively developed to meet the increasingly stringent on-board diagnosis (OBD) requirements. The focus of future soot detection and quantitative prediction is to improve accuracy, reliability and robustness, which may necessitate consideration of soot distribution, ash effect, failure identification and fault tolerance handling.

The Issue of Soot-Catalyst Contact in Regeneration of Catalytic Diesel Particulate Filters: A Critical Review

Soot-catalyst contact represents the main critical issue for an effective regeneration of catalytic (i.e., catalyst-coated) diesel particulate filters (DPFs). Most of the literature reviews on this topic have mainly been focused on studies dealing with powdered soot-catalyst mixtures. Although the results obtained on powders surely provide significant indications, especially in terms of intrinsic activity of materials towards soot oxidation, they cannot be directly extended to DPFs due to completely different soot-catalyst contact conditions generated during filtration and subsequent regeneration. In this work, attention is devoted to catalytic DPFs and, more specifically, studies on both catalyst dispersion and soot distribution inside the filter are critically reviewed from the perspective of soot-catalyst contact optimization. The main conclusion drawn from the literature analysis is that, in order to fully exploit the potential of catalytic DPFs in soot abatement, both a widespread and homogeneous presence of catalyst in the macro-pores of the filter walls and a suitably low soot load are needed. Under optimal soot-catalyst contact conditions, the consequent decrease in the temperature required for soot oxidation to values within the temperature range of diesel exhausts suggests the passage to a continuous functioning mode for catalytic filters with simultaneous filtration and regeneration, thus overcoming the drawbacks of periodic regeneration performed in current applications.

Effect of hybrid breakup modelling on flame lift-off length and soot predictions

An improved droplet breakup model coupled with the effect of turbulence flow within the nozzle was implemented into the general transport equation analysis code to describe the flame lift-off length and predict the soot distribution. This model was first validated by the non-evaporating and evaporating spray experimental data. The computational results demonstrate that the breakup model is capable of predicted spray penetration and liquid length with reasonable accuracy. The inclusion of turbulence enhanced the breakup model, increased the droplet breakup rate, decreased spray penetration for about 6–12% compared to the results of Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) breakup model. Then, the model was applied to investigate the influence of ambient density, temperature, oxygen concentration and injection pressure on the flame lift-off length under typical diesel combustion conditions. The predictions showed good agreement with the experimental data. The result also indicated that the turbulence inside the nozzle strengthen the rate of breakup, resulting in more smaller droplets, leading to high evaporation rate and smaller vapour penetration lengths, thus decreases the lift-off length about 8%. Finally, the model was used to explore the soot distribution. The overall trend of soot with the variations in injection pressure was well reproduced by the breakup model. It was found that the droplet with faster velocity under high injection pressure, this could lead to larger lift-off length, which will play a significant role for the fuel–air mixing process and thus cause a decrease in soot in the fuel jet. Results further indicated that the turbulence term can decrease the soot mass about 5–9% by improved the droplet breakup process.