Diesel Particulate Filter Regeneration Research Articles

Study of the catalyst load for a microwave susceptible catalytic DPF

The development of a fast, safe and cost effective Diesel Particulate Filter (DPF) regeneration procedure is the major remaining technological challenge in the use of this device. In our previous works we showed that the simultaneous use of a MW applicator and a specifically catalyst loaded DPF, with 15%wt of CuFe2O4, allows to reduce the temperature, the energy and the time required for the DPF regeneration. Starting by these very promising results, in this work we continued to study in order to further improve the performances of the catalyzed DPF in terms of catalytic activity, to reduce the temperature and the MW energy required for the regeneration. The objectives of this work are to optimize the preparation procedure of the catalytic DPF, to study the effect of the active species load, and to verify the feasibility of the MW technology by assessing the energy balance of the regeneration phase, comparing it to the actually employed regeneration technologies. In the future we want to evaluate the activity toward the other pollutants present in the diesel exhausts (such as NOx).

Effects of B20 on the Operation of a Single-Cylinder Engine Equipped with a SiC Diesel Particulate Filter

This is an experimental and computational study of the effect of a low-percentage biodiesel blend on the operation, diesel filter loading, and fuel additive-assisted regeneration behavior on a conventional, direct injection (DI), single-cylinder diesel engine. The evolution of regeneration was studied by means of infrared thermography on the unit filter. The results of two sets of regeneration experiments, one for each fuel blend, with high-space velocity levels are discussed. The test fuels were conventional diesel (denoted as B0) and B20 biodiesel blend. The objective was to investigate the differences in catalytic soot ignition and regeneration propagation when the engine is fueled by biodiesel blend. The investigation is assisted by the application of an in-house diesel particulate filter (DPF) regeneration modeling tool. The results indicate a faster evolution of the regeneration with B20 fuel, with lower overall filter wall temperatures prevailing, more favorable on filter durability grounds.

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.

Complete regeneration characteristics of diesel particulate filter using ozone injection

The regeneration of diesel particulate filters (DPFs) is a subject that has attracted considerable interest. Although the ozone injection method is effective, it is unclear whether it can be used to achieve complete DPF regeneration. From the applicative and fundamental points of view, the uncertainty is about whether the diesel particulates, which include nanoparticles, can be completely oxidized by means of plasma. In our study, the possibility of complete DPF regeneration by evaluating the difference between the inlet and outlet pressures of the DPF is investigated. The experimental results show that complete regeneration can be achieved using an ozone injection rate of 34.8g/h for 2h, after 2h of PM collection. Furthermore, a theoretical analysis for the DPF regeneration based on the proposed chemical reactions is presented. Regeneration results agree well with the theoretical ones.

Simulated Fuel Economy and Emissions Performance during City and Interstate Driving for a Heavy-Duty Hybrid Truck

We compare simulated fuel economy and emissions for both conventional and hybrid class 8 heavy-duty diesel trucks operating over multiple urban and highway driving cycles. Both light and heavy freight loads were considered, and all simulations included full aftertreatment for NOx and particulate emissions controls. The aftertreatment components included a diesel oxidation catalyst (DOC), urea-selective catalytic NOx reduction (SCR), and a catalyzed diesel particulate filter (DPF). Our simulated hybrid powertrain was configured with a pre-transmission parallel drive, with a single electric motor between the clutch and gearbox. A conventional HD truck with equivalent diesel engine and aftertreatment was also simulated for comparison. Our results indicate that hybridization can significantly increase HD fuel economy and improve emissions control in city driving. However, there is less potential hybridization benefit for HD highway driving. A major factor behind the reduced hybridization benefit for highway driving is that there are fewer opportunities to utilize regenerative breaking. Our aftertreatment simulations indicate that opportunities for passive DPF regeneration are much greater for both hybrid and conventional trucks during highway driving due to higher sustained exhaust temperatures. When passive DPF regeneration is extensively utilized, the fuel penalty for particulate control is virtually eliminated, except for the 0.4%-0.9%more » fuel penalty associated with the slightly higher exhaust backpressure.« less

Nonuniformity behavior during regeneration of the diesel particulate filter

ABSTRACTThe incomplete regeneration of diesel particulate filter may cause a local build‐up of the soot on the partially regenerated areas during next filtration cycle. This may be one of reasons causing the melting of the ceramic filter during regeneration. In this paper, we investigated several situations at which the particulate matter was partially regenerated. The simulations illustrated that at stationary feed conditions, the influence of nonuniformity of soot loading on the peak temperature rise was less important. When regeneration was conducted at transient feed conditions, the peak temperature attained under the condition of uneven soot distribution along the channel, especially more soot accumulated near the end of the diesel particulate filter, was much higher than that attained under the condition of even soot distribution inside the channel. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

In-Operation Monitoring of the Soot Load of Diesel Particulate Filters: Initial Tests

Diesel particulate filters (DPF) are indispensable parts of modern automotive exhaust gas aftertreatment systems due to the stringent emissions legislation. For a fuel-efficient control strategy, it would be beneficial to determine directly and in-operation their actual trapped soot mass. Two novel approaches—based on the electrical conductivity of trapped soot particles—emerged recently. By measuring the electrical resistance between different single walls inside the filter, the soot load is determined with local resolution. The microwave-based technique is a contactless approach that gives an integral value depending on the soot mass in the DPF. We present investigations on loading and regeneration of DPFs in a dynamometer test bench applying both methods. The results are compared with each other and correlated with the differential pressure and the soot mass. Especially the microwave-based technique has a potential for serial application.

Effect of Biofuels on Catalyzed Diesel Particulate Filter Regeneration

Under the terms of the Renewable Energy Directive, EU member states are required to use 10 % of transport energy sourced from renewable sources, mainly biofuels, by 2020. The purpose is to reduce greenhouse gas (GHG) emissions from the transport sector. However, biodiesel used as fuel has a significant impact on emissions, as related by most of the literature on the subject. In particular, nitric oxides (NOx) and particulate matter (PM) emissions from current diesel technologies are critical factors because they are already close to the limits permitted by regulations and both limits will be even more stringent in the near future. Soot particles are trapped on a diesel particulate filter (DPF). If the DPF is catalyzed like in this study, the soot is then burned by reaction with NO2 (CDPF continuous regeneration) which occurs at lower temperatures than reaction with O2 (active regeneration). Tests of ultra-low sulfur diesel blended with rapeseed-biodiesel at 30 % (B30) and Fischer–Tropsch diesel (FT30) were conducted. The Fischer–Tropsch diesel was chosen to represent a biomass-to-liquid fuel. This work investigated the impact of these two biofuels on engine polluting emissions and the resulting CDPF ability to regenerate. When compared with similar inlet conditions on a synthetic gas bench, an impact of fuel was observed on soot reactivity: the CDPF loaded with FT30 soot regenerated slightly faster. Engine bench tests were also performed to combine the effects of fuel on engine emissions and soot reactivity and to evaluate the CDPF. The increase in NOx and decrease in PM emissions observed for B30 appeared to significantly improve CDPF continuous regeneration by NO2.

Experimental Investigation on the Oxidation Characteristics of Diesel Particulates Relevant to DPF Regeneration

Diesel engines generally employ diesel particulate filter (DPF) systems to meet increasingly stringent emissions regulations. The development of optimum methodologies for DPF regeneration requires detailed information on the oxidation characteristics of diesel particulate matter (PM) that accumulates on the DPF under realistic engine conditions. An experimental investigation on the oxidation behavior of diesel PM collected from a DPF test system connected to the exhaust stream of a 1.9 L, 4-cylinder, light-duty diesel engine is reported. A thermogravimetric analyzer (TGA) was used to measure the instantaneous sample mass and the rate of mass loss during its oxidation for a wide range of conditions, which include initial sample mass, amount of volatile components of soluble organic fraction (SOF) in the sample, oxygen concentration, and various heat treatment schemes in both the inert and oxidizing environments. The global kinetic parameters, i.e., the reaction orders of soot and oxygen, activation energy, and pre-exponential factor, were determined for the diesel PM and surrogate soot samples. Significant differences are observed in the oxidation behavior of surrogate soot and diesel PM. The oxidation rate of surrogate soot decreases continuously as the soot is oxidized, while that of diesel soot is nearly constant until about 80% of the sample mass is oxidized, and then decreases as the sample is completely oxidized. In addition, the oxidation behavior of surrogate soot is found to be essentially independent of the heat treatment schemes used, while that of diesel soot is strongly influenced by them. These differences may be attributable to changes in soot morphology during heating/oxidation and the presence of surface functional groups and heavier SOF components in the diesel PM. The effects of SOF and thermal aging on diesel PM oxidation have also been characterized. Results indicate that the PM oxidation is only weakly influenced by the presence of volatile components of SOF, whereas it is noticeably affected by thermal aging.

舶用４ストロークディーゼル機関用DPFの誘導加熱システムの研究

An induction heating system on a diesel particulate filter (DPF) applied to a 4 -stroke marine diesel engine is studied. The material and structure of the unit filter which comprises the DPF unit are introduced on the basis of the principle of induction heating. Experiments were conducted on a DPF developed for a marine 4 -stroke diesel engine. The PM (Particulate Matter) trapping characteristics were estimated in connection with PM reduction ratio. The DPF regeneration method is mentioned from the point of view of an equivalent electrical circuit of the induction heating load. The effectiveness of the DPF system is verified by experiments.

Strategies for active diesel particulate filter regeneration based on late injection and exhaust recirculation with different fuels

Wall flow–type particulate filters are used in diesel vehicle engines to reduce particulate emissions below the limits established in regulations Euro 5 and Euro 6. The soot accumulated in the trap is eliminated during regeneration processes, often combining passive strategies with active ones. Active regeneration is conducted by modifications of the engine control parameters with respect to those set for normal vehicle operation. In this work, three of these parameters were modified to look for an optimized regeneration strategy, considering fuel consumption, gaseous emissions and rate of regeneration. The selected parameters were injection timing (affecting all injection events), exhaust gas recirculation and amount of postinjected fuel. The fuel tested was considered as an additional variable, and therefore, tests were performed with three different fuels: an ultra-low sulfur diesel fuel, a biodiesel fuel produced from animal fat and a gas-to-liquid fuel from low-temperature Fischer–Tropsch process. It...

Control Strategies for Safe Diesel Particulate Filter Uncontrolled Regeneration during Idle

For diesel particulate filter (DPF) drop-to-idle uncontrolled regeneration, a regular regeneration is initiated following a vehicle stop while the engine switches to idle. The increase in oxygen concentration and the decrease in exhaust flow rate can result in a sharp exotherm in the filter and high temperature to damage the substrate. In this paper, control solutions for the idle thermal protection of the filter was proposed and validated experimentally. At high idle speed of 2200rpm, increasing exhaust gas recirculation (EGR) combined with intake throttling was a practical way to reduce available oxygen content to control the exothermal reaction rate. A much lower peak temperature was obtained for safe DPF regeneration during idle. The research would provide based information for optimizing the regeneration management strategy in order to avoid DPF failure in real world operation.

Modeling of the Regeneration Processes in Diesel Particulate Filters

New simulation algorithm of soot oxidation in diesel particulate filter (DPF) is proposed. Two-dimensional finite differences scheme is used for calculation of the heat transfer in DPF (macro-scale). One dimensional model for treatment of the soot oxidation process in a separate filter channel (micro-scale) is based on a new expression for the oxidation reaction rate that is a modification of the known Bissett's equation. This expression allows consideration of the non-linear dependence of oxidation reaction rate on a reagent concentration. For cases of catalytic coating a modification of the known two-layer model is suggested. A fraction of soot that has been oxidized with the help of the catalyst is not invariable in the first layer, but it exponentially depends on the distance from a channel wall of the particle trap. Soot oxidation by O2 and/or NO2 in diesel particulate filters is investigated for various cases of non-catalytic and catalytic oxidation. The filter clogging propagation from its periphery to the center at critical temperature is described theoretically at first. A comparison between various types of DPF regeneration methods is performed by using the proposed simple simulation algorithm and appropriate computer code.

Design and Experimental Research on Evaporation-Type DPF Regenerative Burner

Diesel engine for automobile mainly adopts diesel particulate filter (DPF) method to deal with the exhaust particulate. In order to eliminate the particulate in the filter and complete DPF regeneration, the burner needs to be set at the entrance of DPF. This paper designs the evaporation-type DPF regenerative burner, and makes the bench and the real vehicle test. The test shows that the burner can complete DPF regeneration well within the working scope of the larger engine.

A study on the cell structure and the performances of wall-flow diesel particulate filter

As for the recent PM regulations, a diesel particulate filter (DPF) has been one of the important aftertreatment technologies. Although the square cell structure of DPF is a generally worldwide standard, several cell designs have been proposed to reduce the pressure loss due to the soot loading as well as the ash deposition in DPF. In this study, we focused on the cell geometry using a hexagonal cell DPF and a conventional square cell DPF. In the engine test bench under nearly real conditions, these DPF performances were evaluated. Results show that, in comparison with square cell DPF, the particle number concentration of the hexagonal cell DPF decreases more rapidly, and the filtration efficiency is higher. In addition, in DPF regeneration test, independent of the inlet temperature, the regeneration rate of the hexagonal cell DPF is higher. Between two DPFs, the aperture ratio of inlet/outlet cells is different. Thus, the superior DPF performance of the hexagonal cell DPF could be explained by the difference of exhaust gas flow and soot deposition region.

Simulating the impact of premixed charge compression ignition on light-duty diesel fuel economy and emissions of particulates and NOx

We report results from urban drive cycle simulations of a light-duty conventional vehicle and a similar hybrid electric vehicle, both of which are equipped with diesel engines capable of operating in either conventional diesel combustion mode or in premixed charge compression ignition mode. Both simulated vehicles include lean exhaust after-treatment trains for controlling hydrocarbon, carbon monoxide, nitrogen oxide, and particulate matter emissions. Our results indicate that, in the simulated conventional vehicle, premixed charge compression ignition can significantly reduce fuel consumption and emissions by reducing the need for lean nitrogen oxide traps and diesel particulate filter regeneration. However, the opportunity for utilizing premixed charge compression ignition in the simulated hybrid electric vehicle is limited because the engine typically experiences higher loads and multiple stop–start transients that are outside the allowable premixed charge compression ignition operating range. This suggests that developing ways of extending the premixed charge compression ignition operating range combined with improved control strategies for engine and emissions control management will be especially important for realizing the potential benefits of premixed charge compression ignition in hybrid electric vehicles.

Pilot-Scale Experiments of Continuous Regeneration of Ceramic Diesel Particulate Filter in Marine Diesel Engine Using Nonthermal Plasma-Induced Radicals

As the regulations governing diesel engine emissions have become more stringent, it has become difficult to fulfill these new requirements by only using techniques that improve combustion. Therefore, more effective aftertreatment technology is needed, particularly for particulate matter. Although ceramic diesel particulate filter (DPF) is a leading technology in automobiles, their implementation in marine diesel engines operated with marine diesel oil (A-heavy fuel oil) containing sulfur presents a problem, in terms of soot removal or regeneration. In this study, a pilot-scale experiment is performed to establish a method implementing nonthermal-plasma-induced radicals for DPF regeneration of marine diesel engines. The pressure difference decreases only when plasma is turned on, and DPF regeneration is realized at 320 °C. The amount of ozone required for regeneration is determined under various engine operating conditions, and the basic characteristics of regeneration are elucidated. The plasma energy required for emission control of the entire gas is approximately 5% of the generated power of the marine engine.

Inlet Cone Effect on Diesel Particulate Filter Regeneration upon a Rapid Shift to Idle

The particulate matter (PM) emitted by a diesel engine is collected and then burned in a diesel particulate filter (DPF). A major technological challenge in the operation of the ceramic, often cordierite, filter is that a rapid shift to idle may create a local hot region with a temperature much higher than under stationary feed conditions. This excessive transient temperature rise may cause local melting or cracking of the ceramic filter. Almost all previous studies of temperature excursions during the DPF regeneration (combustion of the deposited PM) were of cases in which equal exhaust flow rate was fed to all the parallel inlet channels. The diesel engine exhaust pipe is sometimes connected to the DPF by a wide-angled cone (diffuser). This leads to a mal-distribution of the flow rate to the inlet channels and of the deposited PM. Simulations revealed that following a rapid shift to idle the highest regeneration temperature in a DPF fed by a cone exceeded that in one not fed by a cone and it may exceed the cordierite DPF melting temperature (1200 °C). Moreover, it may generate transient radial and axial temperature gradients several times higher than under stationary regeneration that may crack the cordierite DPF. The increase in the temperature gradient is especially large in the axial direction. One of the surprising findings is that the highest temperature attained following a step change to idle is not a monotonic function of the initial PM loading.

Assessment of the legislated particle number measurement procedure for a Euro 5 and a Euro 6 compliant diesel passenger cars under regulated and unregulated conditions

We investigated the possibility of extending the legislated particle number (PN) measurement procedure to (a) control diesel exhaust emissions under unregulated driving conditions, including tests at −7°C and during regeneration of the particulate filter, and (b) reduce the lowest detectable size below 23nm, through dedicated tests of a Euro 5b and a Euro 6 diesel vehicles. The PN emissions of the two vehicles were at or below the limit of 6×1011#/km under all non-regenerative conditions examined. Active regeneration of the Diesel Particulate Filters (DPFs) occurred more frequently (220–510km) than previously reported, and resulted in elevated PM (up to 11mg/km) and PN (1–4×1012#/km) emissions. Condensation Particle Counters (CPCs) having a nominal 50% detection efficiency (10nm and 4.5nm) below the legislated 23nm, detected 50–60% more non-volatile particles over the certification test cycle (New European Driving Cycle). Even higher excess fractions of nano-sized non-volatile particles (160–500%) were observed under urban driving of the Euro 5b vehicle at −7°C, with the absolute levels still remaining below 6×1011#/km however. DPF regeneration and motorway driving favoured the homogeneous nucleation of volatile particles in the Constant Volume Sampler (CVS), which also contributed to the signals of low cut-off size CPCs sampling downstream of the Volatile Particle Remover (VPR). No evidence of such volatile interference could be observed in the legislated PN procedure. A potential shift of the lowest detectable size towards smaller sizes, will require further developments in the measurement procedure.

Experimental study of particle emission characteristics of a heavy-duty diesel engine and effects of after-treatment systems: Selective catalytic reduction, diesel particulate filter, and diesel particulate and NOx reduction

This investigation focused on the particle emission characteristics of a heavy-duty diesel engine and the effects of after-treatment systems such as diesel particulate filter and selective catalytic reduction. The test engine was operated on the worldwide harmonized transient cycle mode, which is a new transient cycle for Euro 6, and the conventional European transient cycle mode. Four combinations of after-treatment systems, engine-out, selective catalytic reduction, diesel particulate filter, and diesel particulate and nitrogen oxide reduction, were evaluated for the transient cycles, respectively. The whole test procedure, as part of the Korea particulate measurement programme and the inter laboratory correlation exercise for domestic heavy-duty diesel engines, complied with the recommended method of particulate measurement programme. The particles that were extracted through the golden particle measurement system the constant volume sampler tunnel consisted of solid particles like carbonaceous fraction, metal ash, etc. The particles emitted from the tail-pipe, as analyzed by the differential mobility spectrometer, included volatile or soluble particles like sulphate fraction, nitrate fraction, and organic fraction. The test results showed that the particle number and size distribution depended on the catalytic activity or filtration efficiency of the after-treatment system. Compared to the accumulation mode, the nucleation mode was easily caught or oxidized by the after-treatment system. Additionally, the nucleation mode was sharply increased by excessive ammonia injection because nitrogen dioxide-assisted diesel particulate filter regeneration resulted in reduced conversion efficiency of the selective catalytic reduction.