Diesel Particulate Filter Regeneration Research Articles

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.

Impact of engine combustion on the reactivity of diesel soot from commercial vehicle engines

The regeneration behavior of diesel particulate filters is significantly influenced by the reactivity of the stored soot. However, there is still a lack of analyses which describe the effects that various engine operating parameters have on soot reactivity. A medium-duty OM936 single-cylinder engine with a common rail injection system was used to analyze the correlations between engine speed, swirl, combustion air–fuel ratio and soot reactivity. Diesel particulate samples were directly collected from the exhaust stream. The temperature programed oxidation was used to reveal the reactivity to oxygen of the soot samples. Diesel particulate filter regeneration experiments were additionally carried out on a medium-duty OM936 full engine test bench to analyze the influence of soot reactivity on the regeneration efficiency in particulate filters. The results give new insights into the relation between the diesel engine combustion process and soot reactivity and show how the active regeneration of diesel particulate filters is affected by soot reactivity.

Temperature effects on particulate emissions from DPF-equipped diesel trucks operating on conventional and biodiesel fuels

Emissions tests were conducted on two medium heavy-duty diesel trucks equipped with a particulate filter (DPF), with one vehicle using a NOx absorber and the other a selective catalytic reduction (SCR) system for control of nitrogen oxides (NOx). Both vehicles were tested with two different fuels (ultra-low-sulfur diesel [ULSD] and biodiesel [B20]) and ambient temperatures (70ºF and 20ºF), while the truck with the NOx absorber was also operated at two loads (a heavy weight and a light weight). The test procedure included three driving cycles, a cold start with low transients (CSLT), the federal heavy-duty urban dynamometer driving schedule (UDDS), and a warm start with low transients (WSLT). Particulate matter (PM) emissions were measured second-by-second using an Aethalometer for black carbon (BC) concentrations and an engine exhaust particle sizer (EEPS) for particle count measurements between 5.6 and 560 nm. The DPF/NOx absorber vehicle experienced increased BC and particle number concentrations during cold starts under cold ambient conditions, with concentrations two to three times higher than under warm starts at higher ambient temperatures. The average particle count for the UDDS showed an opposite trend, with an approximately 27% decrease when ambient temperatures decreased from 70ºF to 20ºF. This vehicle experienced decreased emissions when going from ULSD to B20. The DPF/SCR vehicle tested had much lower emissions, with many of the BC and particle number measurements below detectable limits. However, both vehicles did experience elevated emissions caused by DPF regeneration. All regeneration events occurred during the UDDS cycle. Slight increases in emissions were measured during the WSLT cycles after the regeneration. However, the day after a regeneration occurred, both vehicles showed significant increases in particle number and BC for the CSLT drive cycle, with increases from 93 to 1380% for PM number emissions compared with tests following a day with no regeneration.Implications: The use of diesel particulate filters (DPFs) on trucks is becoming more common throughout the world. Understanding how DPFs affect air pollution emissions under varying operating conditions will be critical in implementing effective air quality standards. This study evaluated particulate matter (PM) and black carbon (BC) emissions with two DPF-equipped heavy-duty diesel trucks operating on conventional fuel and a biodiesel fuel blend at varying ambient temperatures, loads, and drive cycles.

Effects of fuels, engine load and exhaust after-treatment on diesel engine SVOC emissions and development of SVOC profiles for receptor modeling

Diesel exhaust emissions contain numerous semivolatile organic compounds (SVOCs) for which emission information is limited, especially for idling conditions, new fuels and the new after-treatment systems. This study investigates exhaust emissions of particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and sterane and hopane petroleum biomarkers from a heavy-duty (6.4 L) diesel engine at various loads (idle, 600 and 900 kPa BMEP), with three types of fuel (ultra-low sulfur diesel or ULSD, Swedish low aromatic diesel, and neat soybean biodiesel), and with and without a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF). Swedish diesel and biodiesel reduced emissions of PM2.5, Σ15PAHs, Σ11NPAHs, Σ5Hopanes and Σ6Steranes, and biodiesel resulted in the larger reductions. However, idling emissions increased for benzo[k]fluoranthene (Swedish diesel), 5-nitroacenaphthene (biodiesel) and PM2.5 (biodiesel), a significant result given the attention to exposures from idling vehicles and the toxicity of high-molecular-weight PAHs and NPAHs. The DOC + DPF combination reduced PM2.5 and SVOC emissions during DPF loading (>99% reduction) and DPF regeneration (83–99%). The toxicity of diesel exhaust, in terms of the estimated carcinogenic risk, was greatly reduced using Swedish diesel, biodiesel fuels and the DOC + DPF. PAH profiles showed high abundances of three and four ring compounds as well as naphthalene; NPAH profiles were dominated by nitronaphthalenes, 1-nitropyrene and 9-nitroanthracene. Both the emission rate and the composition of diesel exhaust depended strongly on fuel type, engine load and after-treatment system. The emissions data and chemical profiles presented are relevant to the development of emission inventories and exposure and risk assessments.

The Use of a Partial Flow Filter to Assist the Diesel Particulate Filter and Reduce Active Regeneration Events

The Use of a Partial Flow Filter to Assist the Diesel Particulate Filter and Reduce Active Regeneration Events

Impact of selective catalytic reduction on exhaust particle formation over excess ammonia events.

The introduction of selective catalytic reduction (SCR) aftertreatment to meet stringent diesel NOx emission standards around the world increases exhaust ammonia. Further to the direct air quality and health implications of ammonia, this may also lead to particle formation in the exhaust. In this study, an ammonia SCR system was examined with respect to its impact on both solid and total exhaust particle number and size distribution, downstream of a diesel particulate filter (DPF). Fuel post-injection was conducted in some tests to investigate the effect of ammonia during active DPF regeneration. On average, the post-DPF solid >23 nm and total <23 nm particle number emissions were increased by 129% (range 80-193%) and by 67% (range 26-136%), respectively, when 100 ppm ammonia level was induced downstream of the SCR catalyst. This is a typical level during ammonia overdosing, often practiced for efficient NOx control. Ammonia did not have a significant additional effect on the high particle concentrations measured during DPF regeneration. Based on species availability and formation conditions, sulfate, nitrate, and chloride salts with ammonium are possible sources of the new particles formed. Ammonia-induced particle formation corresponds to an environmental problem which is not adequately addressed by current regulations.

Secondary organic aerosol production from diesel vehicle exhaust: impact of aftertreatment, fuel chemistry and driving cycle

Abstract. Environmental chamber ("smog chamber") experiments were conducted to investigate secondary organic aerosol (SOA) production from dilute emissions from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel vehicles (HDDVs) under urban-like conditions. Some of the vehicles were equipped with emission control aftertreatment devices, including diesel particulate filters (DPFs), selective catalytic reduction (SCR) and diesel oxidation catalysts (DOCs). Experiments were also performed with different fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur diesel) and driving cycles (Unified Cycle,~Urban Dynamometer Driving Schedule, and creep + idle). During normal operation, vehicles with a catalyzed DPF emitted very little primary particulate matter (PM). Furthermore, photooxidation of dilute emissions from these vehicles produced essentially no SOA (below detection limit). However, significant primary PM emissions and SOA production were measured during active DPF regeneration experiments. Nevertheless, under reasonable assumptions about DPF regeneration frequency, the contribution of regeneration emissions to the total vehicle emissions is negligible, reducing PM trapping efficiency by less than 2%. Therefore, catalyzed DPFs appear to be very effective in reducing both primary PM emissions and SOA production from diesel vehicles. For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the smog chamber – with the emissions from some vehicles generating twice as much SOA as primary organic aerosol after 3 h of oxidation at typical urban VOC / NOx ratios (3 : 1). Comprehensive organic gas speciation was performed on these emissions, but less than half of the measured SOA could be explained by traditional (speciated) SOA precursors. The remainder presumably originates from the large fraction (~30%) of the nonmethane organic gas emissions that could not be speciated using traditional one-dimensional gas chromatography. The unspeciated organics – likely comprising less volatile species such as intermediate volatility organic compounds – appear to be important SOA precursors; we estimate that the effective SOA yield (defined as the ratio of SOA mass to reacted precursor mass) was 9 ± 6% if both speciated SOA precursors and unspeciated organics are included in the analysis. SOA production from creep + idle operation was 3–4 times larger than SOA production from the same vehicle operated over the Urban Dynamometer Driving Schedule (UDDS). Fuel properties had little or no effect on primary PM emissions or SOA formation.

Effect of Rotary Partition DPF Structure on its Regeneration Characteristics with Microwave

The energy that traditional diesel particulate filter (DPF) regeneration with microwave requires in regeneration process often exceeds the capacity of the vehicle's battery, a rotary partition regenerative DPF with microwave is proposed recently, which was a annular column consisting of the fan-shaped filter units. A filtration unit microwave heating regeneration model was established aiming at this DPF, to study the regenerative properties of the filtration unit and to get influence that its shape structure plays on reproduction characteristics. The results show that: the central angle, length to diameter ratio, the ratio of inner and outer diameter of the DPF all have larger impact on the regeneration. The results can provide theoretical basis and reference for practical development of the new DPF.

Experimental investigation of diesel and biodiesel post injections during active diesel particulate filter regenerations

The purpose of this study is to investigate the common-rail diesel engine and aftertreatment system behaviors during active diesel particulate filter (DPF) regenerations with pure biodiesel and conventional diesel fuels. The experiments were conducted on a medium-duty diesel engine equipped with a high pressure common-rail fuel injection system. The comparative effects of post start of injection (SOI) timing, post fuel injection rate, and the number of post injections, on the engine behaviors including exhaust emissions (total hydrocarbon (THC), carbon monoxide (CO), and oxides of nitrogen (NOx)), exhaust gas temperatures, torque output, and the THC and CO conversion efficiencies inside a diesel oxidation catalyst (DOC), are presented and discussed. Experimental results show that, for both fuels, the engine-out THC emissions at late post injection timings are significantly higher than that at early post injection timings, while the engine-out CO emissions reach the peak values in mid phase of power strokes and the engine-out NOx emissions can be reduced with a late-cycle post injection. Engine torque output and cylinder-out gas temperatures can be promoted obviously with an early post injection. Post injection rate is the dominant factor influencing the exhaust emissions at fixed post SOI timings. Regarding the main differences between the two fuels, substantially lower engine-out THC and CO emissions can be observed from late post injection with biodiesel than those with diesel. The addition of an early post injection to a late post injection has little effect on the engine-out THC emissions, but can lead to higher engine-out CO emissions and higher cylinder-out gas temperatures. Furthermore, substituting diesel with biodiesel in the engine can lower the cylinder-out gas temperature, the engine torque disturbance, and the THC and CO conversion efficiencies inside the DOC.

Impact of FAME Content on the Regeneration Frequency of Diesel Particulate Filters (DPFs)

Modern diesel vehicles utilize two technologies that have been motivated by recent European legislation: diesel fuel blends containing Fatty Acid Methyl Esters (FAME) and Diesel Particulate Filters (DPF). Oxygenates, like FAME, are known to reduce PM formation in the combustion chamber and reduce the amount of soot that must be filtered from the engine exhaust by the DPF. This effect is also expected to lengthen the time between DPF regenerations and reduce the fuel consumption penalty that is associated with soot loading and regeneration. This study investigated the effect of FAME content, up to 50% v/v (B50), in diesel fuel on the DPF regeneration frequency by repeatably running a Euro 5 multi-cylinder bench engine over the NEDC until a specified soot loading limit had been reached. The results verify the expected reduction of engine-out PM emissions with increasing FAME content and the reduction in fuel consumption penalty associated with reducing the frequency of DPF regenerations.

Measuring particulate matter emissions during parked active diesel particulate filter regeneration of heavy-duty diesel trucks

Heavy-duty diesel trucks (HDDTs, >33,000 pounds gross vehicle weight rating) are commonly equipped with diesel particulate filters (DPFs) to meet the California model year (MY) 2007 PM emissions standard. Particulate matter (PM) emissions were measured from nine parked active DPF regenerations of two HDDTs, a 2007 and 2010 MY, using a novel ambient-dilution wind tunnel. This work specifically evaluated PM mass emissions during regeneration by measurements from the following instruments: TSI DustTrak DRX 8533, TSI Engine Exhaust Particle Sizer 3090 (EEPS) and TSI Scanning Mobility Particle Sizer 3936L88 (SMPS), filters by gravimetric analysis, and for one test a Dekati Mass Monitor 230-A (DMM). Active regeneration by fuel injection upstream of the DPF began with the Soot Combustion Regime, where PM emissions had a count median diameter (CMD) of >30nm and some faint gray smoke was observed flowing from the tunnel. During brief moments of the Soot Combustion Regime, the DustTrak DRX reported more than half of the mass was >1µm. As active regeneration continued, aftertreatment inlet temperature increased to >500°C, beginning the Fuel Combustion Regime, defined conversely where the CMD of the emissions was <30nm. Under both regimes, discrepancies were observed between EEPS and SMPS size distributions and improved agreement was attained after performing a post-hoc EEPS correction procedure. The accuracy of the DMM was equivocal; the average DMM emissions rate was within five percent of the gravimetric filter, but the mass distribution was substantially shifted relative to SMPS and EEPS distributions. Uninterrupted parked active regeneration resulted in 13gPM emissions from the 2007 MY and 1.8gPM from the 2010 MY based on filter measurements. The PM mass emissions rates, based on measurements from real-time instruments, show that the contribution of Soot Combustion Regime to total regeneration emissions decreased from 75% to 5% between the 2007 and 2010 MY.

Air-fraction modeling for simultaneous Diesel engine NOx and PM emissions control during active DPF regenerations

This study develops a control-oriented air-fraction model which can accurately predict the air-fraction dynamics for a Diesel engine and the coupled aftertreatment system (mainly Diesel oxidation catalyst (DOC)) during active DPF regenerations. NOx and particulate matter (PM) emissions are the two main concerns for modern Diesel engine development. Diesel particulate filters (DPFs) have become a standard device for reducing the PM emissions from Diesel engine powertrains. To maintain high filtration efficiencies and avoid high back pressures, active DPF regenerations have to be implemented periodically by significantly elevating the exhaust gas temperatures. However, during active DPF regenerations, the selective catalytic reduction (SCR) deNOx performance may be significantly decreased, while the high temperature durability and total hydrocarbon (THC) poisoning of SCRs may be potential issues. To simultaneously meet the NOx emission standard, high-pressure loop EGR needs to be applied. Since in-cylinder NOx reduction relies heavily on the in-cylinder oxygen content, an accurate air-fraction model is necessary, and the effects of recycled THC and CO emissions should be considered. The developed air-fraction model has been experimentally validated to show its capability of capturing the actual air fraction dynamics accurately. Such a model can be instrumental in simultaneous NOx and PM emission control during active DPF regenerations and in advanced combustion mode control.

Application of quartz tuning forks and extensional microresonators for viscosity and density measurements in oil/fuel mixtures

Real time monitoring of the physical properties of liquids is of great concern in the automotive industry. For example, tracking the viscosity of lubricating oils is of great importance because they are exposed to dilution with diesel fuel as result of late-injection processes, which are essential for regenerating diesel particulate filters. Here we describe two in-plane movement based resonators and their capability to assess oil dilution with diesel and biodiesel fuels. One of the resonators is a state-of-the-art micron-sized AlN-based rectangular plate, actuated in the first extensional mode in the MHz range. The second resonator is a commercially available millimeter-sized quartz tuning fork, working at 32.7 kHz. Electrical impedance measurements were performed to characterize the performance of both resonators in various liquid media over a wide range of viscosities. These measurements were compared with the results obtained with low-cost electronic circuits also developed in this work. In order to track density and viscosity of different fluids we have measured two parameters by various techniques: the resonance frequency and the quality factor.

An Efficient CAE Method for the Prediction of the Thermomechanical Stresses during Diesel Particulate Filters Regeneration

An Efficient CAE Method for the Prediction of the Thermomechanical Stresses during Diesel Particulate Filters Regeneration

A universal model of opposed flow combustion of solid fuel over an inert porous medium

In this study, a universal model is developed to examine the behavior of combustion wave observed in porous solid matters (e.g., smoldering, self-propagating high-temperature synthesis (SHS), diesel particulate filter (DPF) regeneration process). Analytical expressions of the combustion characters of solid combustible (e.g., diesel particulate matters trapped in a DPF) deposited over an inert porous medium are obtained employing large activation energy asymptotic taking into account the sensible transport processes; namely, heat transfer between the porous medium and gas phases, radiation heat transfer from the porous medium, heat loss from the porous medium to the environment, mass transfer of oxygen from the gas stream to the surface of solid fuel and the effective diffusion in modeling the species diffusion. Then it has been validated that the present model is applicable and adaptable for predicting the characteristics of smoldering combustion and thus SHS process. As a result, the features of combustion wave of the present phenomena would be useful to other processes. From practical point of view and for deep understanding of the behavior of combustion wave of these processes, we investigate the effects of various physical parameters over a wide range of conditions. We observe that the moving speed of the reaction front increases with the increase of porosity of the porous medium, mass transfer coefficient and initial fuel mass fraction; while it decreases owing to the increase of heat transfer rate from the porous medium to the gas, heat loss to the environment and radiative heat transfer. Furthermore, the results reveal that extinction tends to occur due to lower porosity of the porous medium, higher radiative heat transfer from the porous medium, higher heat transfer rate from the porous medium to the gas and higher heat losses from the porous medium to the environment. Even the observed near-extinction behavior in reaction front speed versus heat loss diagram is found to be similar what we got in gaseous premixed flame propagating through the porous medium. An extinction limit diagram has been presented as a function of radiation-conduction parameter and the gas flow velocity. In addition to, the impact of radiation and the combined effect of the inclusion of Knudsen diffusion and tortuosity are demonstrated in terms of the spatial temperature and species profiles to examine how these two parameters modify the reaction front structure. Furthermore, the governing equations have been solved numerically and it is observed that asymptotic analysis gives a good agreement with the numerical solution.

Observer-Based Estimation of Air-Fractions for a Diesel Engine Coupled With Aftertreatment Systems

This paper presents a control-oriented air-fraction dynamic model for a complete diesel engine and aftertreatment system, as well as an observer to estimate the air-fractions in the integrated diesel engine and aftertreatment system. To reduce engine-out emissions and further improve engine efficiency, advanced combustion modes including low temperature combustion, premixed charge compression ignition, and homogenous charge compression ignition, are under intensive investigations. With the popular configuration of dual-loop exhaust gas recirculation (EGR) systems including a high-pressure loop exhaust gas recirculation and a low-pressure loop EGR (LP-EGR), alternative combustion modes can be potentially accomplished. In addition, aftertreatment systems including diesel oxidation catalysts (DOCs), diesel particulate filters (DPFs), and selective catalytic reduction (SCR) systems, are becoming necessary to satisfy stringent emission standards. With the increasing complexity of modern diesel engines and aftertreatment systems, air-path loop control for the diesel engine systems becomes further challenging partially because LP-EGR couples the aftertreatment systems with the diesel engine air-path system. Most of the current air-fraction dynamic models and observers only consider the air-fractions through the diesel engines and air-fraction dynamics through aftertreatment systems are ignored, which, however, will introduce significant modeling errors in the situations when active DPF regenerations and post-fuel injections are implemented. The purpose of this paper is to develop a control-oriented air-fraction dynamic model for a complete diesel engine and aftertreatment system. Based on the developed model, a Luenberger-like observer is proposed and analyzed using a Lyapunov method as well as the physical meaning of system parameters. Experimental results show that the developed air-fraction model is highly accurate and the designed observer is able to make the estimated air fractions converge to the corresponding true values quickly in both steady-state and transient operations.

Continuously regenerating Diesel Particulate Filters based on ionically conducting ceramics

This study reports a mechanistic study of the soot oxidation on Yttria-Stabilized Zirconia (YSZ), a non-reducible oxide with intrinsic bulk oxygen mobility. Temperature-Programmed Oxidation (TPO) and isotope exchange experiments demonstrate the key role of bulk oxygen species in the oxidation process. When “intimate” soot/YSZ contact is achieved after in situ carbon deposition via propylene cracking, lattice oxygen ions are the predominant species involved in the oxidation reaction. Based on isotopic TPO experiments performed with different oxygen partial pressures in “tight” contact mode and oxygen exchange measurements, it is proposed that the ignition of the soot oxidation on YSZ can be described as a fuel-cell-type electrochemical mechanism at the nanometric scale. The efficiency of this electrochemical process seems to depend both on the YSZ/soot contact and on the oxygen partial pressure. In addition, YSZ porous membranes were fabricated in order to simulate porous walls of YSZ-based DPFs. These membranes are effective for soot filtering and soot oxidation with oxygen starts at temperatures over 430°C, in real soot/catalyst contact.

Decision-Making and Control System of Diesel Particulate Filter Regeneration

The decision-making and control system of a burner-type diesel particulate filter (DPF) regeneration was designed. Through the online simulation and the application research, it showed that the regeneration system had good response performances on prediction, decision-making, support and control. The DPF regeneration could be rapidly completed in 5-10 minutes and the regeneration efficiency be more than 87%, and the peak temperature and its maximum average grads were in the safe range. The system can realize the efficient, reliable and safe regeneration.

A Ceramic Filter Counter Blowing Regeneration Control System

This paper developed a high efficiency, simple to use and reliable, strong practicability of model 6120 diesel particulate filter regeneration control pulse inverse blow system. The pulse counter blowing regeneration test, and post-processing of particles back down to do the further research. The experimental results show that this device can wall honeycomb ceramic filter for filtering and counter blowing regeneration test and research.

Pulse Clean and Regeneration Control Device in Ceramic Filter

This article developed a 6120-type diesel particulate filter pulse clean and regeneration control system with a high efficiency, simple reliable use. And it has determined the spray nozzle diameter, the injection distance, the injection pressure, the pulse width, the injection time of five factor optimal fit experiment parameter. This control system can flow the type honeycomb ceramics filter to the wall to carry on the test and the research of the filtration and the regeneration; It can realize the filter filtration and the regeneration change work. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.3232