Diesel Particulate Filter Performance Research Articles

Numerical simulation of diesel particulate filter flow characteristics optimization: From the perspective of pore structure parameters and inlet velocity

The diesel particulate filter (DPF) with porous media structure has become an essential component for diesel engines to satisfy increasingly strict emission standards. This study constructed a porous media structure model of DPF, and optimized its boundary to conduct a simulation on the flow characteristic with different influencing parameters using the lattice Boltzmann method (LBM). Results showed that the increase of the average flow velocity of the DPF model reduced the pressure drop, indicating that the flow probability of model improved. In addition, the porosity application range was expanded. The visualization and quantization of the velocity and pressure distribution with the DPF revealed that an increase of the wall thickness resulted in a higher pressure drop of the DPF, but a lower flow velocity. Further, the fractal dimension of the porous media exhibited no direct relationship with the DPF pressure and velocity performance; however, the outlet velocity and pressure drop of the model were optimized within the different porosity. Moreover, both the increase in the spectral dimension and model optimization improved the DPF permeability. The impact of increasing the inlet velocity on the pressure drop was particularly significant as it accelerated the rate of pressure drop, illustrating that a smoother porous media boundary was conducive to improve the flow performance of DPF, which facilitated a better scheme for the design of DPF porous media.

Characteristics of ash formed by different lubricant additives and its effect on DPF performance

Diesel Particulate Filter (DPF) is an important technology to reduce diesel exhaust particles. The ash formed by the combustion of lubricant oil will be deposited in the DPF, which will affect the filtration efficiency of DPF. In this paper, the ash generated in the burner by combustion of two lubricant additives mixed with diesel fuel were obtained by the burner test of ash rapid loading. The microscopic morphology of ash was studied by scanning electron microscopy and the fractal dimension was calculated based on fractal theory. Chemical composition analysis was performed using energy-dispersive X-ray spectroscopy. The filtration efficiency of DPF was tested with EEPS 3090 when loaded with different ash fractions. The results show that the average fractal dimension of Mg-based ash (1.5791) is higher than that of Ca ash (1.5420), indicating a more detailed surface structure at the microscopic level. This suggests that Mg-based ash is more likely to plug, sinter and even form bridging phenomenon in the DPF inlet channel. The filtration efficiency of DPF increases and then decreases with the loading of ash. The capture efficiency of large particles of 40–200 nm is increasing with the loading of Ca-based ash. However, due to the higher fractal dimension, the loading of Mg-based ash can significantly improve the capture efficiency of small particles of about 10 nm. This work is beneficial to explain the influence of ash on the efficiency of DPF in filtering particles of different sizes.

Physicochemical characteristics of ash-bridges in diesel particulate filter

The diesel particulate filter (DPF) is one of the most effective devices for reducing particulate emissions from diesel engines so as to satisfy emission regulations, and it has been widely utilized worldwide. After prolonged operation of the DPF, the accumulated non-combustible ash particulates can be sintered with filter walls and form ash-bridges, which will deteriorate DPF performance and increase emissions. Understanding physicochemical characteristics of ash-bridges is essential for elucidating the generation and evolution mechanisms of ash-bridges. Since lubricant additives are the main source of ash particulates, this study prepared four DPFs containing ash-bridges through accelerate ash loading experiments based on Zn-based, Ca-based, Mg-based, and composite lubricant additives. Subsequently, X-ray computed tomography (X-CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were employed to analyze the structural characteristics, micro-morphology, and chemical composition of ash-bridges inside each DPF. The results indicate that Zn-based and composite ashes formed numerous fine ash-bridges in the middle of the DPF, whereas Ca-based and Mg-based ashes resulted in fully shaped and highly blocked ash-bridges. These ash-bridges aggregated into compact ash plugs downstream in all DPFs. The micro-morphology of Zn-based ash-bridges appeared as ball-and-stick, Ca-based ash-bridges aggregated into large ash aggregates in DPF downstream, Mg-based ash-bridges exhibited characteristics of high porosity, and the micro-morphology of composite ash-bridges is spherical in DPF downstream. The primary components of ash-bridges in Zn-based, Ca-based, and Mg-based DPFs are Zn2P2O7, CaSO4, and MgO, respectively. The main components of ash-bridges in composite DPF include Ca7Mg2P6O24, Zn3(PO4)2(H2O)4, and CaSO4. These findings provide valuable insights into the understanding of ash-bridges, contributing to the enhancement of DPF performance and durability.

Multi-objective impact mechanism on the performance characteristic for a diesel particulate filter by RF-NSGA III-TOPSIS during soot loading

Diesel particulate filter (DPF) provides an effective control method for particulate matter (PM) emissions from diesel vehicles. In the PM trap process of DPF, pressure drop and filtration efficiency present conflicting relationships as the main indicators of the comprehensive trap performance. To fully optimize the comprehensive trap performance of DPF, this research develops a hybrid multi-objective optimization approach of FGRA-RF-NSGA III-TOPSIS. Specifically, critical structures are selected from DPF structural features by fuzzy grey correlation analysis (FGRA). Three machine learning (ML) models are trained on the computational fluid dynamics (CFD) model dataset to relate the critical structures to the initial filtration efficiency and pressure drop. Then, statistical indicators are introduced to evaluate three ML models, and the best-performing model – The random forest (RF) model is selected as the input of the optimization algorithm. Finally, a hybrid Critic-TOPSIS approach is used to select the most ideal solution from the Pareto frontier obtained by the NSGA III as the output of the optimization results. The optimized DPF reduces the pressure drop by 49.84 % and improves the initial filtration efficiency by 49.31 % compared to the original DPF under standard operating conditions. The optimization effect is more significant at high-speed and high-load conditions.

Experimental study on the pressure drop and thickness variation of carbon black particle layer during oxidation on DPF channels

Investigating the evolution of pressure drop and particle layer thickness during oxidation is crucial for comprehending the regeneration performance of diesel particulate filters (DPFs) and optimizing the regeneration process. In this study, a visualized single-channel test bench was employed to actively regenerate carbon black particle layers on DPF channels. Online measurements and dynamic analysis of pressure drop and particle layer thickness were conducted to examine their behaviors. The results demonstrated that the particle layer regeneration process can be categorized into three stages. In the first stage, the pressure drop gradually decreased while the thickness continued to increase. In the second stage, the pressure drop reduction rate significantly accelerated with increasing deposition thickness (particularly between 112 μm and 147 μm), while the particle layer continued to thicken due to thermal expansion, reaching a peak of 193 μm before declining. For layers thicker than 273 μm, continuous thickening was observed. In the third stage, the pressure drop reached its minimum value, and the rate of thickness decrease became relatively high. Notably, a time delay was observed between the rapid decline in thickness and the steep decrease in pressure drop, which increased with the thickness of the particle layer. At a deposition thickness of 404 μm, the particle layer became suspended on the filter wall during the heating process, creating a gap .

Influence of the engine drop-to-idle process on regeneration temperature, filtration and morphology characteristics of diesel particulate filters

As emission regulations become more stringent, the durability of diesel aftertreatment system is a concern in addition to its purification capacity. Under extreme circumstances, the engine may drop-to-idle (DTI) sharply, which can cause the diesel particulate filter (DPF) cracking and melting during active regeneration due to the excessive soot combustion heat. This study investigated the regeneration performance of cordierite DPFs during the DTI process, including temperature and emission characteristics. The temperature distribution is nonuniform, with the peak temperature occurring in the middle ring of the DPF monolith’s rear end. As the soot load reached 7 g/L, extensive DPF cracks were observed and the particle number (PN) emission exceeded the regulatory limit. The study also examined the evolution of the DPF's porous wall’s macro morphology and micro pore structure, finding that microcracks formed and the wall surface became rougher. The substrate’s bulk density, average pore diameter, and permeability decreased while the total pore volume, total pore area, tortuosity, and porosity increased. By analyzing temperature, filtration and morphology characteristics, this work provides a recommended soot mass limit (SML) for cordierite DPF, which is essential for developing a reliable regeneration strategy in diesel vehicle control systems. The findings also help with the optimization design of substrate and catalysts for manufacturers in terms of substrate material, filter geometry, cell density and catalyst coating.

Numerical simulation of diesel particulate filter performance optimization through pore structure analysis

Based on the theory of spherical filled bed, the internal porous media filter wall of the Diesel Particle Filter (DPF) is assumed to fill the filter wall of the unit cell. Since particle trapping by DPF is a dynamic process, the particle deposition characteristics inside DPF are simulated by numerical simulation in this paper. The influence of macroscopic incoming flow parameters and microstructural parameters on DPF filtration performance is investigated, and then the optimization window that can improve DPF filtration performance is explored. The results show that increasing the exhaust temperature and incoming particle concentration leads to an increase in the filtration efficiency and pressure drop of DPF, while the higher the filtration velocity, the lower the filtration efficiency of DPF. In addition, the larger the porosity, the higher the filtration efficiency and pressure drop of DPF, while the increase in the average pore size and pore size distribution range leads to a decrease of the filtration performance of DPF. On this basis, evaluation indexes that can evaluate the filtration performance of DPF are proposed to provide a theoretical basis for optimizing the substrate parameters of DPF.

A review of regeneration mechanism and methods for reducing soot emissions from diesel particulate filter in diesel engine.

With the global emphasis on environmental protection and the proposal of the climate goal of "carbon neutrality," countries around the world are calling for reductions in carbon dioxide, nitrogen oxide, and particulate matter pollution. These pollutants have severe impacts on human lives and should be effectively controlled. Engine exhaust is the most serious pollution source, and diesel engine is an important contributor to particulate matter. Diesel particulate filter (DPF) technology has proven to be an effective technology for soot control at the present and in the future. Firstly, the exacerbating effect of particulate matter on human infectious disease viruses is discussed. Then, the latest developments in the influence of key factors on DPF performance are reviewed at different observation scales (wall, channel, and entire filter). In addition, current soot catalytic oxidant schemes are presented in the review, and the significance of catalyst activity and soot oxidation kinetic models are highlighted. Finally, the areas that need further research are determined, which has important guiding significance for future research. Current catalytic technologies are focused on stable materials with high mobility of oxidizing substances and low cost. The challenge of DPF optimization design is to accurately calculate the balance between soot and ash load, DPF regeneration control strategy, and exhaust heat management strategy.

Effect of structural parameters on diesel particulate filter trapping performance of heavy-duty diesel engines based on grey correlation analysis

Pressure drop and filtration efficiency are important indicators of capture performance of diesel particulate filter (DPF). In this paper, the DPF three-dimensional computational fluid dynamics (CFD) model developed by the three-dimensional software AVL Fire is used to investigate the influence of key structural factors on the capture performance. The results show that the pressure drop in DPF can be reduced by properly increasing the filter diameter, filter length, CPSI or reducing the wall thickness. Increasing the filter diameter, filter length and wall thickness or reducing CPSI in an appropriate range is conducive to improving the DPF filtration efficiency. In addition, based on the results of grey correlation analysis (GRA), the wall thickness, as the most significant structural factor, should be given priority in the design of DPF. This work has important reference value for optimizing DPF capture performance and extending its working time.

Effect of regeneration method and ash deposition on diesel particulate filter performance: a review.

As countries around the world pay more attention to environmental protection, the corresponding emission regulations have become more stringent. Exhaust pollutants cause great harm to the environment and people, and diesel engines are one of the most important sources of pollution. Diesel particulate filter (DPF) technology has proven to be the most effective way to control and treat soot. In this paper, we review the latest research progress on DPF regeneration and ash. Passive regeneration, active regeneration, non-thermal plasma-assisted DPF regeneration and regeneration mechanism, DPF regeneration control assisted by engine management, and uncontrolled DPF regeneration and its control strategy are mainly introduced. In addition, the source, composition, and deposition of ash are described in detail, as well as the effect of ash on the DPF pressure drop and catalytic performance. Finally, the issues that need to be further addressed in DPF regeneration research are presented, along with challenges and future work in ash research. Over all, composite regeneration is still the mainstream regeneration method. The formation of ash is complex and there are still many unanswered questions that require further in-depth research.

플라즈마 버너를 활용한 노후건설기계의 백연(white smoke) 배출 저감 기술

White smoke emission from decrepit construction vehicles is one of the main causes of fine dust production. In particular, despite the fact that a large amount of white smoke is occurring in the vehicles such as decrepit construction machinery equipped with DPF (Diesel Particulate Filter), no technical solution has been found yet. This study aims to analyze the causes of white smoke emission that occurs in DPF system and propose technical solutions to resolve the issues. The performance and operational characteristics of the burner mounted to thermally manage the DPF performance are the main causes of the occurrence of white smoke. The fundamental ignition mechanism of the diesel burners was investigated depending on the types of ignition sources; the rotating gliding arc for plasma burner and glow plug for conventional diesel burner. It was verified that plasma burner can be applied to drastically reduce the occurrence of white smoke.

Experimental evaluation of DPF performance loaded over Pt and sulfur-resisting material for marine diesel engines.

Different from vehicle engines, Diesel Particulate Filter (DPF) inactivation is an unavoidable issue for low-speed marine diesel engines fueled with Heavy Fuel Oil (HFO). This paper introduced a sulfur resisting material in Silicon Carbide (SiC)-DPF to improve DPF performance. The results of bench-scale experiments showed that the Balance Point Temperature of the modified DPF module was 300°C and DPF modules had a good filtration performance, with Particulate Matters (PMs) residual being less than 0.6 g per cycle. In pilot-scale tests, PMs emissions of unit power decreased with engine load going up, filtration efficiency of nucleation mode PMs being only 36% under 100% load, while DPF still had a good performance in accumulation mode PMs control, being 94.2% under the same load. DPF modules showed excellent regeneration durability in the 205h endurance test, with a regeneration period of 1.5-2h under 380°C. There was no obvious degeneration in the DPF module structure, with no cracks or breakage. Besides, the DPF module could also control gaseous emissions, total emissions decreased by 10.53% for NO and 57.19% for CO, respectively. The results suggested that introducing sulfur-resisting material in DPF could greatly improve the DPF performance of low-speed marine diesel engines fueled with HFO.

Experimental investigation on the effects of DPF Cs-V-based non-precious metal catalysts and their coating forms on non-road diesel engine emission characteristics.

Non-precious metal catalysts with good soot catalytic properties and a low cost have great potential for application in diesel particulate filters (DPF). In this study, we compared the effects of DPF supported by Cs2V4O11 (Cs-V-based) non-precious metal catalysts and conventional Pt-Pd-based precious metal catalysts on the performance of a non-road diesel engine. Furthermore, the effects of on-wall coating and in-wall coating of Cs-V-based catalysts on DPF performance were also investigated. The results indicated that the particulate emissions from DPF with Cs-V-based catalysts were reduced slightly less than that with Pt-Pd-based catalysts; however, the particle number (PN) and particulate matter (PM) emissions were still reduced by 94.4% and 91.7%, respectively, meeting the non-road China IV limits under the non-road steady cycle (NRSC). In addition, CO, HC, and NO can also be slightly oxidized by the non-precious metal catalysts. On the other hand, the DPF with in-wall coating induced comparatively higher gaseous substances and particulate emissions and caused a higher exhaust back pressure (EBP), which was 9.6% higher than the on-wall coating under NRSC, negatively affecting engine performance. Additionally, the geometric mean diameter (GMD) for the DPF with in-wall coating was only 33.3nm because of the large emission proportion of nuclear mode particles.

Effect analysis on pressure sensitivity performance of diesel particulate filter for heavy-duty truck diesel engine by the nonlinear soot regeneration combustion pressure model

In this paper, the nonlinear soot regeneration combustion pressure model (NSRCMP model) is established and employed for Diesel Particulate Filter (DPF) simulation study. The NSRCMP model is reliable and accurate under simulation and experimental conditions of the process of clean filter, soot loading and soot regeneration combustion. The DPF soot loading response time and pressure drop are investigated under the parameter changes of cell density, wall thickness and permeability. It is a new attempt to measure the DPF pressure sensitivity by the trend of different design parameters. Cell density and permeability affect the soot loading time dramatically and the maximum and minimum soot loading time ratio is 3. Cell density and permeability make a significant pressure drop change through the pressure sensitivity comparisons. The corresponding ratio of maximum pressure sensitivity parameter is 2.4 when the cell density is 100 cpsi. The comparison results of pressure sensitivity under different permeabilities show a fixed ratio of 1.4. The results show that cell density is the key parameter to affect the overall system pressure. The influence of wall thickness on pressure sensitivity is not sensitive to the change of configurations of DPFs.

Effect of structure parameters of catalyst substrate on the performance of diesel particulate filter

The filtration efficiencies of the particulate matter and the particulate number in DPF, the no-load pressure drop of DPF, and the load pressure drop of DPF were selected as key performance parameters of DPF. The influence of the cell density and the wall thickness of the DPF on these key performance parameters of DPF was studied in detail. Firstly, a calculation model of DPF was established, and the compensation mathematical model was added. Secondly, the key performance parameters of DPF were defined. Finally, based on the model, the key performance parameters are numerically investigated under different cell density and wall thickness of the DPF. Consequently, with the increase of cell density of DPF, the filtration efficiency of DPF increases, the load pressure drop of DPF decreases, but the no-load pressure drop of DPF increases. With the decrease of the wall thickness of the DPF, the no-load pressure drop of the DPF decreases, the load pressure drop of the DPF decreases, but the filtration efficiency of the DPF decreases. The most suitable combination scheme is a cell density of 200-300 CPSI and a wall thickness of 11-16 mil.

Sensitivity analysis of diesel particulate filters to geometric parameters during soot loading and its multi-objective optimization

In order to improve the overall performance of diesel particulate filter (DPF) in the soot capture process, a multi-objective optimization model is developed based on the objective functions of maximum pressure drop and initial filtration efficiency. Firstly, the sensitivity analysis of the structural parameters of DPF are performed. Then the response surface model based on Box-Behnken is constructed, and diagnostic analysis and analysis of variance (ANOVA) are carried out for each response. Finally, the non-dominated sorting genetic algorithm-II (NSGA-II) is used to obtain the Pareto optimal solution. The research results show that the sensitivity of filter diameter to maximum pressure drop and initial filtration efficiency is higher than other parameters. The multi-objective optimization results are verified by GT-SUITE software, and the maximum relative errors of maximum pressure drop and initial filtration efficiency between the simulation and optimization results are 1.41% and 3.28%, respectively. Compared with the original performance, the initial filtration efficiency of DPF is improved by 16.42%. The optimized DPF pressure drop decreased by 15% and 36.33% at the beginning and end of the filtration period, respectively.

Evaluation of heavy-duty vehicle emission controls with a decade of California real-world observations

ABSTRACT Over the past decade, efforts to reduce emissions of particulate matter (PM) and oxides of nitrogen (NO + NO2, or NO x ) from heavy-duty diesel vehicles (HDDVs) have led to the widespread adoption of both Diesel Particulate Filters (DPFs) to control PM and Selective Catalytic Reduction (SCR) to control NO x . We evaluated the performance of DPFs and SCR with 13,327 real-world fuel-based Black Carbon (BC) and NO x emission factors from 9,167 unique heavy-duty vehicles (primarily HDDVs) measured at four sites in California (two ports, two highways) from 2011 to 2018. BC emission factors have decreased by 90% during the past decade. At the same time, BC distributions have become increasingly skewed toward “high-emitters” – e.g., the portion of the HDDV fleet responsible for half of all BC emissions has decreased from ~16% to ~3%. NO x emission factors have also decreased over the past decade, but by only 31%. They remain roughly five times greater than in-use thresholds.We examined changes in BC and NO x emissions with engine age. BC emissions from DPF-only trucks decreased slightly but insignificantly, by 6 ± 15 mg/kg fuel per year, while for DPF+SCR trucks they increased by 5 ± 3. These changes are less than 5% of in-use thresholds. The annual increase in NO x emissions with age was much greater: 1.44 ± 0.28 g/kg for older SCR trucks without on-board diagnostic (OBD) capabilities and 0.48 ± 0.35 for newer trucks with OBD, roughly 20– 50% of in-use thresholds. Paired t-tests on the over 600 vehicles that were observed in multiple campaigns were consistent with these results. Observed changes in BC emissions with age were best fit with a “gross emitter” model assuming an annual DPF failure rate of 0.83 ± 0.01% for DPF-only trucks and 0.56 ± 0.01% for DPF+SCR trucks.Implications: These observations of real-world HDV emission factors have several major implications for regulatory efforts to reduce them. The increasing importance of a relatively small number of high BC emitters suggests that widespread sampling of the on-road fleet will be necessary to identify these vehicles. On the other hand, the much more ubiquitous deterioration in NO x control measures may be better addressed by incorporating on-board diagnostic systems, with telematic data transfer when possible, into inspection and maintenance programs. These NO x observations also highlight the need for strengthening heavy-duty SCR durability demonstration requirements.

Multi-objective optimization of a diesel particulate filter: an acoustic approach

In order to decrease the soot particles’ harmful emission, it is necessary to use a diesel particulate filter (DPF) on cars. Recent years, many countries standardize using DPF on cars. In this paper, a multi-objective design optimization study is performed by using the nondominated sorting genetic algorithm (NSGA-II) to obtain an optimum DPF geometry. In the present study, two objective functions were determined to obtain an optimum DPF. The first was to maximize sound transmission loss (TL) values to increase the acoustical properties of the DPF, while the second was to minimize the back pressure to cause the diesel engine to work efficiently and consume less energy. The optimization problem has been constructed in the form of maximizing the sum of the values of TL at all frequencies, as optimizing the problem for each frequency separately means a new DPF at each frequency, which has a different geometry. In the literature, optimization of the DPF has been carried out for a few parameters by just changing one parameter value and keeping others stable. However, in this paper, optimization of the acoustic performance of DPFs was performed for more than one parameter in the range of their specific values simultaneously.

Anhydrous Gypsum as Diesel Ash Surrogate and Sensitivity to Ash Particle Size in Accelerated Ash Loading Studies

<div class="section abstract"><div class="htmlview paragraph">Accelerated ash loading studies provide a cost-effective means of investigating the long-term impacts of ash accumulation in diesel particulate filters (DPFs). Despite a variety of methods adopted in previous studies for accelerated ash loading, evaluation of their impact on DPF behavior has been limited primarily to pressure drop response (with & without soot), and characterization of properties of the resulting ash deposits for comparison with samples from field testing. In the current study, the potential to use ash recovered from field DPFs to perform accelerated ash loading studies is explored. Additionally, anhydrous gypsum as a surrogate for diesel ash was investigated. Benefits of using gypsum include low cost and easy access, safety during handling and testing, and consistency from test to test. Narrow control of particle sizing and composition can help compare performance over a wide range of filter sizes and applications. The ash surrogate was mixed with Printex-U soot to minimize re-agglomeration and introduced into a temperature and flow-controlled exhaust stream upstream of a DPF, using an in-house auger setup. The ability to control ash accumulation pattern in the DPF using parameters such as particle size and gypsum loading rate (g/h) was explored. Additionally, the impact of ash particle size on ash layer and plug characteristics and therefore pressure drop and filtration performance was also studied. The results were compared with field DPFs to evaluate the effectiveness of the accelerated ash protocol to mimic DPF performance on the field.</div></div>

Soot Oxidation in Diesel Exhaust on Silver Catalyst Supported by Alumina, Titanium and Zirconium

Diesel Particulate Filter (DPF) is used to limit the emission of particulate matter (PM). The operation of DPF has two consecutive functions which are filtration of PM and regeneration. Performance of DPF is reduced by clogging of the filter. This problem is improved by soot oxidation in the regeneration process. The soot is completely oxidized by oxygen when temperature is higher than 600 °C. However, the exhaust gas temperature in normal operating of the diesel engine is lower than the temperature of soot complete oxidation. The problem of low temperature in soot oxidation is improved by oxidation catalyst because the oxidation catalyst is used to reduce light of temperature in soot oxidation. The study’s purpose is to compare the oxidation activity of silver catalyst supported on alumina (Al2O3), Titanium oxide (TiO2), and Zirconium oxide (ZrO2). The compression of soot oxidation on silver catalyst loaded on several support which showed silver base on alumina was the best of soot oxidation compared with titanium oxide and zirconium oxide. The behaviour of soot oxidation in silver base on titanium oxide and zirconium oxide were similar activity.