Thermogravimetric analysis of soot combustion in the presence of ash and soluble organic fraction

Effect of temperature control conditions on DPF regeneration by nonthermal plasma

A regeneration test of a diesel particulate filter (DPF) was conducted under different temperature conditions with air as the gas source and a nonthermal plasma (NTP) injection system. We investigated the influence of the ambient temperature on the DPF regeneration performance and the oxidative decomposition amount of particulate matter (PM) and analyzed the changes in the PM oxidation characteristics by thermogravimetric analysis (TGA). The higher the temperature, the lower the decomposition amount of PM was under constant temperature conditions. The decomposition amount of PM was the highest at 80 °C (3.74 g), and the PM at interface P2 was not completely removed. The volume concentrations of the DPF regeneration products (CO and CO₂) were higher under variable than constant temperature conditions. In addition, the peak temperature of interface P1 occurred 10-30 min earlier, complete regeneration occurred at interface P2, and DPF regeneration occurred faster than under temperature conditions. The initial temperature of the control device was 110 °C, and the maximum mass of PM oxidation decomposition was 4.26 g after regeneration for 15 min cooling to 80 °C. The main form of elemental carbon (EC) transformed into the low ignition point component and the oxidation activity was improved after NTP injection.

Physical, chemical, and cell toxicity properties of mature/aged particulate matter (PM) trapped in a diesel particulate filter (DPF) along with the results from freshly produced PM of a diesel engine

The lifetime and efficiency of diesel particulate filters (DPFs) strongly depend on the proper and periodic cleaning and servicing. Unfortunately, in some cases, inappropriate methods are applied to clean the DPFs, e.g., using air compressors without proper disposal procedures which can have negative impacts on human health, the environment, and DPF's efficiency. However, there is no information available about the properties of this kind of PM. This research is therefore presented to explore the physicochemical and toxicity properties of aged PM trapped in a DPF (using compressed air for PM sampling) employing STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer for investigating the physicochemical properties, and assays of cell viability, cellular reactive oxygen species (ROS), interleukin-6, and tumor necrosis factor-alpha (TNF-α) for investigating the toxicity properties. Also, analyses from fresh PM samples from the diesel vehicle at two engine speeds are presented. It is found that at a certain/fixed PM number/mass for all three samples tested, the PM from DPF compared with the fresh PM can have both positive (particularly having the lowest water-soluble total carbon ratio) and negative impacts on human health (particularly having the highest cell death rate of 13.4%, ROS, and TNF-α) and the environment.

Physicochemical and cell toxicity properties of particulate matter (PM) from a diesel vehicle fueled with diesel, spent coffee ground biodiesel, and ethanol

The literature shows that information about the physical, chemical, and cell toxicity properties of particulate matter (PM) from diesel vehicles is not rich as the existence of a remarkable number of studies about the combustion, performance, and emissions of diesel vehicles using renewable liquid fuels, particularly biodiesels and alcohols. Also, the PM analyses from combustion of spent coffee ground biodiesel have not been comprehensively explored. Therefore, this research is presented. Pure diesel, 90% diesel + 10% biodiesel, and 90% diesel + 9% ethanol + 1% biodiesel, volume bases, were tested under a fast idle condition. STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer were employed for investigating the PM physical and chemical properties, and assays of cell viability, cellular reactive oxygen species, interleukin-6, and tumor necrosis factor-alpha were examined for investigating the PM cell toxicity properties. It is found that the application of both biodiesel and ethanol has the potential to change the PM properties, while the impact of ethanol is more than biodiesel on the changes. Regarding the important aspects, biodiesel can be effective for better human health (due to a decrease in cell death (-60.8%)) as well as good diesel particulate filter efficiency (due to lower activation energy (-7.6%) and frequency factor (-83.2%)). However, despite a higher impact of ethanol on the reductions in activation energy (-24.8%) and frequency factor (-99.0%), this fuel causes an increase in cell death (84.1%). Therefore, biodiesel can be an appropriate fuel to have a positive impact on human health, the environment, and emissions catalysts performance, simultaneously.

Wavelet analysis for cyclic combustion dynamics of a multi-cylinder CRDI diesel engine fuelled with a blending of argemone biodiesel-diesel oil

Higher cyclic variability in combustion adversely influences emissions, efficiency, and driveability of internal combustion engines. In this paper, we used wavelet transform techniques to investigate the dynamical characteristics of a combustion process in numerous combustion parameters of a 4-cylinder turbocharged common rail direct injection (CRDI) diesel engine fuelled with Argemone mexicana biodiesel (AGB)/diesel blended fuel. In addition, statistical analysis is described to validate the results of the wavelet spectrum methods for cyclic variation in the diesel engine. The results show that the cyclic variations in IMEP and Pmax are sensitive to the engine load and fuel properties. The coefficient of variation of both combustion parameters decreases as engine load increases for all tested fuels. Moreover, adding Argemone mexicana biodiesel (AGB) into diesel fuel up to 20% (AB20) reduces cyclic variations in combustion parameters at all tested engine loads. Furthermore, the global wavelet spectrum and wavelet power spectrum are utilized to identify the dominant oscillatory combustion modes. The cycle-to-cycle fluctuations in combustion parameters (i.e., IMEP and Pmax) exhibit multi-scale dynamics for all experimental conditions. Compared to long and intermediate oscillations in diesel fuel, AB10 and AB20 fuel showed short and intermittent period fluctuations. The findings of this experimental work will be helpful to optimize engine control strategies for AGB/diesel blended fueled multi-cylinder CRDI diesel engines.

Experimental Investigation on the DPF High-Temperature Filtration Performance under Different Particle Loadings and Particle Deposition Distributions

Based on DPF filtration and regeneration bench, the solid particle emission and high-temperature filtration characteristics of different carbon black particle loadings and particle deposition distributions are studied. The aerosol generator (PAlAS RGB 1000) is used to introduce carbon black particles into the inlet of a DPF, and the NanoMet3 particle meter is used to measure the solid particle concentration at the inlet and outlet of a DPF to obtain the filtration characteristics. Previous studies found that without inlet carbon black particles, there was an obvious solid particle emission peak at the outlet of the deposited DPF during the heating, and the concentration increased by 1–2 orders of magnitude. In this paper, the high-temperature filtration characteristics under steady-state temperature conditions are studied. It is found that a DPF can reduce the range of inlet fluctuating particles, and with the increase of temperature, the proportion of large solid particles in the outlet particles increases, and the size distribution range decreases. Particle loading has positive and negative effects on the DPF filtration, and the DPF has the optimal particle loading, which makes the comprehensive filtration efficiency improve the highest. The deposition transition section can make the deposition particles in the DPF uniform, but the filtration efficiency is reduced.

Effect of Operating Parameters on Oxidation Characteristics of Soot under the Synergistic Action of Soluble Organic Fractions and Ash

Diesel particulate filter is used to reduce particulate matter (PM) emission due to the stringent emission standards. The accumulated PM has been oxidized by the periodical regeneration method to avoid pressure buildup. The innovation of this study is to explore the oxidation performance of Printex-U (PU), which is mixed with ash and soluble organic fractions, under different operating conditions. Different aspects of operating parameters, such as the oxygen ratio in an O2/N2 atmosphere, total flow rate, initial PU mass, and heating rate, on PU oxidation properties have been critically discussed using a thermogravimetric analyzer. The oxygen ratio in the O2/N2 atmosphere is positively correlated with the oxidation characteristics of PU. The comprehensive oxidation index (S ) of PU under the 20% O2/80% N2 atmosphere increases by 184% compared with the 10% O2/90% N2 atmosphere. When the initial PU mass is 3 mg, the combustion stability coefficient (R w) and S reach the best values, which are 55.53 × 105 and 2.03 × 107 %2min-2 ° C-3, respectively. With the increase in the heating rate, the oxidation properties of PU become sensible and deflagration occurs easily, so that 10 °C/min heating rate is the best option. This study provides a theoretical basis for the optimization design of diesel particulates during the regeneration process.

Effect of Different Aging Conditions on the Soot Oxidation by Thermogravimetric Analysis

Diesel particulate filter is an effective device to reduce diesel particulate emission. The particles in diesel particulate filter are usually affected by the aging of high-temperature exhaust gas before the regeneration process. In order to investigate the effect of aging conditions on the soot oxidation process, the effect of aging temperature and aging time on the oxidation process of carbon black (Printex-U, PU) and the PU/catalyst/ash mixture are studied by thermogravimetric analysis. The aging PU particles have lower starting temperature, peaking temperature, ending temperature, and activation energy. Compared with the particles without aging, the PU particles with a 400 °C aging temperature and 20 h aging time are able to reduce the activation energy from 191.2 to 158 kJ/mol. Low aging temperatures (200-300 °C) and the catalyst have a certain synergistic effect on the improvement of PU oxidation activity. The PU/CeO2 mixture with a 300 °C aging temperature and 20 h aging time decreases the activation energy from 178.4 to the lowest 113.6 kJ/mol. The addition of CaSO4 in PU particles cannot stop the improvement of its oxidation activity by aging, but it reduces the effect of aging. This work is helpful to reveal the mechanism of aging on PU and the PU/catalyst/ash mixture in air environment.