Diesel Particulate Filter Pressure Drop Research Articles

Pressure drop model of DPF considering ash factor at different capture stages

In this paper, a pressure drop model of diesel particulate filter (DPF) is established on diesel bench loading tests and simulation studies. A proposed DPF soot loading prediction model takes into account the different factors and calculation methods of pressure drop formation in different capture stages, including deep bed capture stage, transitional capture stage and soot cake capture stage. Further, a pressure drop model of DPF is improved, and the model for different filter wall permeability in different capture stages is discussed. The calculated results of the model are verified with the experimental results. Finally, the influence of ash factor on the modification of DPF pressure drop model was investigated.The results show that, when the ash layer is 0.05 mm–0.15 mm in the deep bed capture stage, the modified values of filtration wall permeability are 8.2%–43.8% of the original values. In the transitional capture stage, the ash layer with thickness of 0.01 mm–0.05 mm needs to modify 0.75 g/L∼1.5 g/L soot loading. The DPF pressure drop and the particle soot cake layer thickness increase linearly with time in the soot cake capture stage. When the ash layer changes in the range of 0.05 mm–0.15 mm, the soot loading is modified to 13.4%–36.8% of the original value. When the axial scale of the ash plug is 1/5,1/4 and 1/3 of the DPF length, the soot loading is corrected to 33.3%, 37.3% and 45.1%.

Particulate Matter Load Estimation and Distribution Characteristics of Diesel Particulate Filter

This paper focuses on the offline electric heating regeneration technology of DPF (Diesel Particulate Filter). Based on the actual operating conditions of the airport passenger elevator, the pressure drop changes before and after the offline regeneration of DPF, the passive regeneration process during the vehicle operation, and the capture efficiency of PM and PN after the offline regeneration of DPF are studied. The DPF pressure drop increases with the operation time because of the extremely low efficiency of passive regeneration before offline regeneration, and the initial pressure drop after regeneration is slightly higher than that of the fresh carrier due to the existence of ash. When the exhaust temperature reaches 420°C, the DPF passive regeneration rate is higher than the capture rate, and the DPF pressure drop drops rapidly when the passenger elevator continues to run. The mass fraction of fine particulate matter is more than 0.02μm in the cold start stage, while the mass fraction of fine particulate matter is more than 0.02μm in the hot start stage.

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.

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.

Experimental study of lubricant-derived ash effects on diesel particulate filter performance

Diesel particulate filters are indispensable for diesel engines to meet the increasingly stringent emission regulations. A large amount of ash would accumulate in the diesel particulate filter over time, which would significantly affect the diesel particulate filter performance. In this work, the lubricant-derived ash effects on diesel particulate filter pressure drop, diesel particulate filter filtration performance, diesel particulate filter temperature field during active regeneration, and diesel particulate filter downstream emissions during active regeneration were studied on an engine test bench. The test results show that the ash accumulated in the diesel particulate filter would decrease the diesel particulate filter pressure drop due to the “membrane effect” when the diesel particulate filter ash loading is lower than about 10 g/L, beyond which the diesel particulate filter pressure drop would be increased due to the reduction of diesel particulate filter effective volume. The ash loaded in the diesel particulate filter could significantly improve the diesel particulate filter filtration efficiency because it would fill the pores of diesel particulate filter wall. The diesel particulate filter peak temperature during active regeneration is consistent with the diesel particulate filter initial actual soot loading density prior to regeneration at various diesel particulate filter ash loading levels, while the diesel particulate filter maximum temperature gradient would increase with the diesel particulate filter ash loading increase, whether the diesel particulate filter is regenerated at the same soot loading level or the same diesel particulate filter pressure drop level. The ash accumulation in the diesel particulate filter shows little effects on diesel particulate filter downstream CO, total hydrocarbons, N2O emissions, and NO2/NO x ratio during active regeneration. However, a small amount of SO2 emissions was observed when the diesel particulate filter ash loading is higher than 10 g/L. The ash accumulated in the diesel particulate filter would increase the diesel particulate filter downstream sub-23 nm particle emissions but decrease larger particle emissions during active regeneration.

DPF Soot Loading Estimation Strategy Based on Pressure Difference

The China V emission standard for light duty vehicles, starting to be effective from January 1, 2018, is the first time to set particulate number (PN) emission limits. This necessitates diesel particulate filters (DPFs) to be equipped for diesel powered pick-up trucks. A DPF soot load estimation model based on the DPF pressure drop is established to support the regeneration time selection and DPF applications and management. The accuracy of the model is validated through the engine dynamometer testing and on-vehicle road tests.

Pre-DPF water injection technique for pressure drop control in loaded wall-flow diesel particulate filters

Wall-flow type diesel particulate filter (DPF) is a required aftertreatment system for particle emission abatement and standards fulfilment in Diesel engines. However, the DPF use involves an important flow restriction, especially as the substrate gets soot and ash loaded. It gives as a result the increase of the exhaust back-pressure and hence a fuel consumption penalty. The increasing damage of fuel consumption with DPF soot loading leads to the need of the regeneration process. Usually based on active strategies, this process involves an additional fuel penalty but prevents from excessive DPF pressure drop and ensures secure soot burnt out.Under this context, new solutions are required to improve the state of the art DPF soot loading to pressure drop ratio. This paper presents a novel technique based on pre-DPF water injection to reduce the DPF pressure drop under soot loading conditions by disrupting its dependence on soot/ash loading. It provides benefits to engine fuel economy and also higher flexibility for DPF regeneration and maintenance. The work covers a test campaign performed in a passenger car turbocharged Diesel engine equipped with a wall-flow DPF. The main objective is to describe the technique, to provide a figure of its potential for pressure drop control and fuel consumption reduction. The results of the experiments also confirm soot and ash loading capacity increase and demonstrate the lack of negative effects on filtration efficiency and active and passive regeneration.

Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions

The soot loading process in wall-flow DPFs (diesel particulate filters) affects the substrate structure depending on the filtration regime and produces the increase of pressure drop. Deep bed filtration regime produces the decrease of the porous wall permeability because of the soot particulates deposition inside it. Additionally, a layer of soot particulates grows on the porous wall surface when it becomes saturated. As soot loading increases, the pressure drop across the DPF depends on the porous wall and particulate layer permeabilities, which are in turn function of the substrate and soot properties. The need to consider the DPF pressure drop influence on engine performance analysis or DPF regeneration processes requires the use of low-computational effort models describing the structure of the soot deposition and its effect on permeability. This paper presents a model to describe the micro-scale of the porous wall and the particulate layer structure assuming them as packed beds of spherical particles. To assess the model's capability, it is applied to predict the DPF pressure drop under different experimental conditions in soot loading, mass flow and gas temperature.

Soot and Ash Deposition Characteristics at the Catalyst-Substrate Interface and Intra-Layer Interactions in Aged Diesel Particulate Filters Illustrated using Focused Ion Beam (FIB) Milling

The accumulation of soot and lubrication-derived ash particles in a diesel particulate filter (DPF) increases exhaust flow restriction and negatively impacts engine efficiency. Previous studies have described the macroscopic phenomenon and general effects of soot and ash accumulation on filter pressure drop. In order to enhance the fundamental understanding, this study utilized a novel apparatus, that of a dual beam scanning electron microscope (SEM) and focused ion beam (FIB), to investigate microscopic details of soot and ash accumulation in the DPF. Specifically, FIB provides a minimally invasive technique to analyze the interactions between the soot, ash, catalyst/washcoat, and DPF substrate with a high degree of measurement resolution. The FIB utilizes a gallium liquid metal ion source which produces Ga+ ions of sufficient momentum to directionally mill away material from the soot, ash, and substrate layers on a nm-μm scale. As the FIB cuts into the sample, uncovering intra-layer details, the coupled high resolution SEM imaging and energy dispersive x-ray (EDX) analysis provide both morphological and chemical data. This tool was applied to investigate soot and ash accumulation in the DPF, with a specific focus on characterizing interactions between the soot/ash/DPF interfaces, such as soot penetration into the ash layer, as well as soot and ash accumulation in the DPF surface pores. In particular, ash and soot particle size, layer pore structure, and the extent of penetration or intra-layer mixing, are all parameters directly impacting DPF pressure drop, which may be quantified using this technique. The work in this study leveraged existing databases of aged DPFs containing various levels of soot and ash, originating from field trials and controlled laboratory testing. Results obtained with this technique provide a fresh and complementary perspective, as well as additional details useful to understand the macroscopic observations of the combined ash and soot effects on diesel particulate filter pressure drop.

Modeling of Pressure Drop in a 3-D Network Ceramic Diesel Particulate Filter

Diesel Particulate Filters (DPFs) provide probably the most effective means of trapping the exhaust emitted particulates from diesel engines. Three-dimension network ceramic filters become a promising alternative to the conventional wall flow filters, since they are effective in filtering small sized particles and provide a large specific surface area for catalytic coating. A mathematical model of pressure drop for a three-dimension network ceramic DPFs is developed. The model calculates the pressure drop of a filter as a function of the geometric filtering properties, operating conditions and structure of trapping. The calculated pressure drops of a filter agree well with the experimental results. The pressure drop of DPFs increases linearly with increasing trap length, and there is a nonlinear relationship between the exhaust gas mass flow rate and pressure drop. For optimized traps, the pressure drops are much lower than those of the filters with a unitary trap structure.

Ash Effects on Diesel Particulate Filter Pressure Drop Sensitivity to Soot and Implications for Regeneration Frequency and DPF Control

Ash Effects on Diesel Particulate Filter Pressure Drop Sensitivity to Soot and Implications for Regeneration Frequency and DPF Control

Diesel particulate filter pressure drop Part 2: On-board calculation of soot loading

In the first part of this study, an improved model for the calculation of pressure drop in particulate filters was presented with special emphasis on the soot permeability properties and its dependence on temperature and pressure. With the assumption of uniform wall flow distribution throughout the channel length, it was also possible to derive an analytical expression that was validated against experimental data on an engine bench. Using the results of pressure drop modelling, it is possible to carry out ‘inverse’ calculations of the soot mass in the filter based on the measurements of flowrate, temperature and backpressure, which forms the main subject of the present work. This approach is tested successfully against experimental data in filters of different geometry and material, yielding promising results. Such computations may be very helpful for the interpretation of experimental results in engine testing. In this paper, typical applications in the field of reaction rate assessment are presented. Moreover, model-based soot loading calculations are expected to assist the implementation of regeneration and on-board diagnostics strategies for particulate filters.

Diesel particulate filter pressure drop Part 1: Modelling and experimental validation

Pressure drop modelling is a subject of special interest for the design and control of diesel particulate filters. Based on previous experience, an improved pressure drop model is presented. Special emphasis is given on the soot permeability properties and its dependence on temperature and pressure. With the assumption of uniform wall flow distribution throughout the channel length, it is possible to derive an analytic expression for pressure drop calculation. The main difference with previously proposed analytic expressions lies in the inclusion of gas density dependence on local pressure, which necessitates an iterative calculation procedure. The importance of this improvement is illustrated parametrically. The new model is validated against experimental data on an engine bench, using a double filter configuration to ensure constant filter soot loading throughout the test.