Diesel Particulate Filter Regeneration Research Articles

Low Temperature Diesel Particulate Filter Regeneration by Atmospheric Air Non-thermal Plasma Injection System

An experimental study of the regeneration of diesel particulate filter (DPF) was conducted through the use of a self-designed Non-thermal plasma (NTP) injection system with an experimental temperature of 20–300 °C, with atmospheric air being used as the gas source. The results revealed that the PM could be broken down into CO and CO2 by NTP, through a discharge reaction of the NTP reactor. As the temperature increases, the mass of C1 (mass of C in CO) showed an overall declining trend. Interestingly, the mass of C2 (mass of C in CO2) and C12 (the sum of C1 and C2) both showed an initial increase, followed by a decrease. The peak mass of C12 appears at 150 °C, and both axial and radial temperature gradients are less than the limit of DPF temperature gradient at this temperature. In conclusion, DPF can be regenerated by the NTP technology at a lower temperature, which can aid in the avoidance of thermal damage of DPF. The technology boasts a great advantage in adopting atmospheric air as its gas source, which can not only reduce costs, but also is convenient.

Cylinder Pressure Information-Based Postinjection Timing Control for Aftertreatment System Regeneration in a Diesel Engine—Part I: Derivation of Control Parameter

The implementation of aftertreatment systems in passenger car diesel engines, such as a lean NOx trap (LNT) and a diesel particulate filter (DPF), requires an in-cylinder postinjection (POI) for a periodic regeneration of those aftertreatment systems to consistently reduce tail-pipe emissions. Although the combustion and emission characteristics are changed from the normal engine operating conditions due to the POI, POI is generally applied with a look-up table (LUT) based feedforward control because of its cost effectiveness and easy implementation into the engine management system (EMS). However, the LUT-based POI control necessities tremendous calibration work to find the optimal timing to supply high exhaust gas temperature or enough reductants such as carbon monoxide (CO) and hydrocarbon to regenerate the aftertreatment systems while maintaining low engine-out smoke emissions. To solve this problem, we propose a novel combustion analysis method based on the cylinder pressure information. This method investigates the relation between the POI timing with the exhaust emissions and compensates the combustion phase shift occurred by the engine operating condition changes, such as the engine speed and injection quantity. A burning rate of fuel after a location of the rate of heat release maximum (BRaLoROHRmax) was derived from the combustion analysis. A mass fraction burned X% after a location of the rate of heat release maximum (MFBXaLoROHRmax) was determined using the BRaLoROHRmax and main injection (MI) quantity. Nonlinear characteristics of the exhaust emissions according to POI timing variations and the combustion phase shift due to the engine operating condition changes can be easily analyzed and compensated in terms of the proposed MFBXaLoROHRmax domain. The proposed method successfully evaluated its utility through the engine experiments for the LNT and DPF regeneration.

Cylinder Pressure Information-Based Postinjection Timing Control for Aftertreatment System Regeneration in a Diesel Engine—Part II: Active Diesel Particulate Filter Regeneration

The successful utilization of a diesel particulate filter (DPF) to reduce particulate matter (PM) in a passenger car diesel engine necessitates a periodic regeneration of the DPF catalyst without deterioration of the drivability and emission control performance. For successful active DPF regeneration, the exhaust gas temperature should be over 500 °C to oxidize the soot loaded in the DPF. Previous research increased the exhaust gas temperature by applying early and late post fuel injection with a look-up table (LUT) based feedforward control implemented into the engine management system (EMS). However, this method requires enormous calibration work to find the optimal timing and quantity of the main, early, and late post fuel injection with less certainty of accurate torque control. To address this issue, we propose a cylinder pressure based multiple fuel injection (MFI) control method for active DPF regeneration. The feedback control of the indicated mean effective pressure (IMEP), lambda, and DPF upstream temperature was applied to precisely control the injection quantity of the main, early, and late post fuel injection. To determine their fuel injection timings, a mass fraction burned 60% after location of the rate of heat release maximum (MFB60aLoROHRmax) was proposed based on the cylinder pressure information. The proposed control method was implemented in an in-house EMS and validated at several engine operating conditions. During the regeneration period, the exhaust gas temperature tracked the desired temperature, and the engine torque fluctuation was minimized with minimal PM and NOx emissions.

Numerical Simulation of Diesel Particulate Filter Regeneration Considering Ash Deposit

Non-combustible ash can be deposited on channel walls through the full length of a diesel particulate filter (DPF). This type of ash can affect the exhaust condition and heat transfer process during the periodical soot regeneration of DPF. A model of soot regeneration is established in this paper to describe the effects of ash deposits on exhaust condition and heat transfer. Mass, momentum, and energy balances are considered for the multiphase system of gas, soot, and wall. The good agreement with experimental data confirms that the model is able to describe the processes. The axial patterns of wall temperature and soot regeneration rate during DPF regeneration are investigated by numerical simulation. Results indicate that the deposited ash layer reduces the exhaust flow rate and increases the heat conduction resistance during DPF regeneration, thus leading to high wall temperature and soot oxidation rate. When 5 g/L of ash is deposited, the complete oxidation of soot can be achieved 90 s faster with a 60 ∘C increase in wall temperature. The gain on soot oxidation rate increases with increasing amounts of deposited ash and reaches a plateau when the deposited ash approaches 15 g/L. Owing to the sintering and melting of ash when the temperature reaches 900 ∘C and the consequent uncontrolled regeneration, the soot carrying capacity should be identified based on the amount of deposited ash within DPF.

303 相変化を伴う非定常壁面衝突噴霧に関する研究(OS2 エンジン技術の高度化に向けた先端研究,研究討論セッション)

Diesel particulate filter (DPF) is a very effective aftertreatment device to limit particulate emissions from diesel engines. When the DPF regeneration is performed, it is necessary the DOC works durably if the injected fuel is completely vaporized before entering the DOC, and uniform mixed with the exhaust gases. However, ensuring complete evaporation and an optimum mixture distribution in the exhaust line are challenging. Therefore, it is important that the fuel spray features are grasped to perform DPF regeneration effectively. This report focuses on impingement spray, to understand physical phenomenon.

Composite Control of DOC-out Temperature for DPF regeneration

Control of Diesel Oxidation Catalyst (DOC) outlet temperature is critical for the downstream Diesel Particulate Filter (DPF) regeneration. However, the disturbances, delay time variation and model uncertainties make it difficult to control DOC outlet temperature. A Composite Controller (CC) based on modified Active Disturbance Rejection Control (mADRC) with delay-time adaptation was proposed for DOC-out temperature control in this paper. The proposed controller includes a model-based Feedforward controller(FF) and a mADRC. The model based FF was designed based on the model between the reference temperature, inlet temperature, mass flow rate and the fuel injection. The mADRC was modified from regular Active Disturbance Rejection Contoller (rADRC) with an adaptation of input delay time. The input delay time is adapted according to the mass flow rate of exhaust gas. Simulation and test results through high-fidelity GT-Power model show that the proposed design can effectively control the DOC-out temperature.

M509 DPF再生のための排気管燃料噴射における噴霧挙動の数値解析(GS7 ディーゼル噴霧・燃焼(2),修士研究発表セッション)

M509 DPF再生のための排気管燃料噴射における噴霧挙動の数値解析(GS7 ディーゼル噴霧・燃焼(2),修士研究発表セッション)

Comparison of Parallel and Series Hybrid Power Trains for Transit Bus Applications

The fuel economy and emissions of conventional and hybrid buses equipped with emissions aftertreatment were evaluated via computational simulation for six representative city bus drive cycles. Both series and parallel configurations for the hybrid case were studied. The simulation results indicated that series hybrid buses have the greatest overall advantage in fuel economy. The series and parallel hybrid buses were predicted to produce similar carbon monoxide and hydrocarbon tailpipe emissions but were also predicted to have reduced tailpipe emissions of nitrogen oxides compared with the conventional bus in higher speed cycles. For the New York bus cycle, which has the lowest average speed among the cycles evaluated, the series bus tailpipe emissions were somewhat higher than they were for the conventional bus; the parallel hybrid bus had significantly lower tailpipe emissions. All three bus power trains were found to require periodic active diesel particulate filter regeneration to maintain control of particulate matter. Plug-in operation of series hybrid buses appears to offer significant fuel economy benefits and is easily employed because of the relatively large battery capacity that is typical of the series hybrid configuration.

Pyrolysis Characteristic Analysis of Particulate Matter from Diesel Engine Run on Diesel/Polyoxymethylene Dimethyl Ethers Blends Based on Nanostructure and Thermogravimetry

ABSTRACTThis paper focuses on the nanostructural and pyrolysis characteristics of particulate matter (PM) emitted from a diesel engine fueled by three diesel/polyoxymethylene dimethyl ethers (PODEn) blends. PM was collected using a metal filter from the exhaust manifold. The collected PM samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). SEM and TEM analysis showed that PM generated by the 20%-PODEn blend was looser and had a smaller average diameter than that emitted when a lower proportion of PODEn was used. Additionally, fringe length was reduced, and separation distance and tortuosity were increased, when the 20%-PODEn blend was used instead of the other blends. These changes improved the oxidation reactivity of the PM. TGA demonstrated that the PM pyrolysis process was divided into low temperature (characterized by moisture and volatile components) and high temperature (the combustion of solid carbon) stages. When the blending ratio was increased, the moisture and volatile components of the PM showed no obvious change, but the ignition temperature and activation energy were reduced. Additionally, the pyrolysis performance was enhanced; the maximum weight loss rate was higher; the combustion and burnout characteristic indices were higher; and the combustion efficiency of the PM was improved. These results show that the use of diesel blended with oxygenated fuel (PODEn) affects the nanostructure and pyrolysis of PM, and this PM is easier to oxidize and advantageous for diesel particulate filter regeneration.

Influence analysis of monolith structure on regeneration temperature in the process of microwave regeneration in the diesel particulate filter

AbstractBased on models A, B, and C of three kinds of diesel particulate filter (DPF) with microwave regeneration, a DPF microwave regeneration model is established according to the laws of conservation of mass, momentum, and energy. The trends of internal temperature under different velocities of exhaust gas in channels are simulated and analyzed. The results show that: (1) Regeneration temperature in the process of microwave regeneration will begin to increase from the front to the rear end of along the axial direction, and the maximum temperature value will appear in the rear end of the monolith. (2) The internal flow velocity in the DPF of model C is the most uniform and the temperature gradient is the smallest among the three models. Therefore, it is the most useful for DPF regeneration. (3) The minimal thermal stress is exerted on the DPF of model C. Therefore, this model is most useful for prolonging the service life of a DPF.

Characteristics of particle number and mass emissions during heavy-duty diesel truck parked active DPF regeneration in an ambient air dilution tunnel

Abstract Diesel particle number and mass emissions were measured during parked active regeneration of diesel particulate filters (DPF) in two heavy-duty diesel trucks: one equipped with a DPF and one equipped with a DPF + SCR (selective catalytic reduction), and compliant with the 2007 and 2010 emission standards, respectively. The emission measurements were conducted using an ambient air dilution tunnel. During parked active regeneration, particulate matter (PM) mass emissions measured from a 2007 technology truck were significantly higher than the emissions from a 2010 technology truck. Particle number emissions from both trucks were dominated by nucleation mode particles having a diameter less than 50 nm; nucleation mode particles were orders of magnitude higher than accumulation mode particles having a diameter greater than 50 nm. Accumulation mode particles contributed 77.8 %–95.8 % of the 2007 truck PM mass, but only 7.3 %–28.2 % of the 2010 truck PM mass.

The evaluation of fuel borne catalyst (FBC’s) for DPF regeneration

Even though diesel particulate filters (DPFs) have been in commercial production for many years, there is still much optimisation activity, especially in the field of the regeneration strategy of these filters.A method for obtaining organosoluble substances with an iron content of 10–15wt% and composition containing iron additives and other selected substances has been developed. These organosoluble substances form the basis for the development of various additives of the fuel borne catalyst (FBC) type for passive regeneration of DPF’s.To test and evaluate the effectiveness of the regeneration process supported by the developed FBC additives, a novel multistage procedure consisting of three separate engine tests, which allow a comprehensive examination of additives, has been implemented. Each additive had been rated in this engine procedure at different dosage levels in a specified order. This rating allowed reliable assessment of the operational properties of the additives under the conditions of dynamometer engine testing.As a result, from a wide range of FBC-type additives developed and then rated in the engine bench test procedure, the best two additives were selected. These additives achieved a much better operational performance than the commercial additives from two of the reputed manufacturers.The studies that we have performed present evidence of the high operational performance potential of FBC additives in the effective passive regeneration supporting of DPF’s.

Impact of Cylinder Deactivation on Active Diesel Particulate Filter Regeneration at Highway Cruise Conditions

Abstract—Heavy-duty over-the-road trucks require periodic active diesel particulate filter regeneration to clean the filter of stored particulate matter. These events require sustained temperatures between 500 and 600□C to complete the regeneration process. Engine operation during typical 65 mile/hour highway cruise conditions (1200 rpm/7.6 bar) results in temperatures of approximately 350□C, and can reach approximately 420□C with late fuel injection. This necessitates hydrocarbon fueling of a diesel oxidation catalyst or burner located upstream of the diesel particulate filter to reach the required regeneration temperatures. These strategies require increased fuel consumption, and the presence of a fuel-dosed oxidation catalyst (or burner) between the engine and particulate filter. This paper experimentally demonstrates that, at the highway cruise condition, deactivation of valve motions and fuel injection for two or three (of six) cylinders can instead be used to reach engine outlet temperatures of 520-570□C, a 170-220□C increase compared to normal operation. This is primarily a result of a reduction in the air-to-fuel ratio realized by reducing the displaced cylinder volume through cylinder deactivation.

The effect of iron loading and hydrothermal aging on one-pot synthesized Fe/SAPO-34 for ammonia SCR

The current commercially-available technique for NOx reduction for diesel engines is the selective catalytic reduction (SCR) of NOx with NH3 over Cu zeolites. One of the problems of this technique is their limited ability to convert NOx at diesel particulate filter (DPF) regeneration temperatures. In addition, during regeneration of the DPF there is a risk of thermally deactivating the SCR catalyst. Thus, the aim of the current work was the development of a catalytic system that can reduce NOx both at low as well as high temperature and in addition is stable at high temperature. In order to reach this goal, a Fe/SAPO-34 with chabazite (CHA) structure was combined in a system with a commercial Cu/CHA catalyst. Earlier studies have shown that it is difficult to ion-exchange Fe into CHA structures due to steric hindrance, and we have therefore used a novel synthesis procedure which incorporated iron directly into the zeolite structure. Fe/SAPO-34 with three different Fe-loadings (0.27; 0.47 and 1.03wt.% Fe) were synthesized and the catalysts were characterized using inductively coupled plasma atomic spectroscopy (ICP-AES), N2 adsorption–desorption isotherms, BET area measurements and X-ray diffraction (XRD). The chemical composition, porous and crystalline structure of the parent SAPO-34 sample were found to be only slightly affected by addition of small amounts of Fe in the framework zeolite structure. However, more visible changes in the crystallinity were observed in the Fe/SAPO-34 catalysts with higher Fe content, which were attributed to the unit cell size expansion provoked by integration of higher amounts of Fe into the zeolite SAPO-34 framework. The Fe/SAPO-34 with the lowest Fe-loading (0.27wt.%) was found to be the best catalyst when considering activity as well as high temperature stability. The synthesized Fe/SAPO-34 catalyst demonstrated a significantly improved NOx reduction performance at high temperatures (600–750°C) when compared to a commercial Cu/CHA SCR system, and the combined system (Fe/SAPO-34+Cu/CHA) exhibited a very good performance in a large temperature interval (200–800°C) that encompasses most diesel exhaust gas conditions.

Effect of Exhaust Gas Temperature on Oxidation of Marine Diesel Emission Particulates with Nonthermal-Plasma-Induced Ozone

Because the regulations governing diesel engine emissions are becoming more stringent, effective aftertreatment is needed for particulate matter. Although diesel particulate filters (DPFs) are a leading technology used in automobiles, there remains a problem with DPF regeneration for marine diesel engines that use heavy oil fuel. In the present study, pilot-scale experiments were conducted to develop a particulate oxidation technology for marine diesel engine emissions using DPF regeneration by nonthermal-plasma-induced ozone injection. It has been shown that particulate oxidation depends on the exhaust gas temperature, and regeneration can be performed most effectively at a temperature of approximately 300 °C.

Catalytic regeneration of Diesel Particulate Filters: Comparison of Pt and CePr active phases

Diesel Particulate Filters (DPFs) have been loaded with the same amount (0.6wt.%) of either Pt or an optimized CePr active phase, and an experimental set-up has been designated and used to investigate the catalytic combustion of soot under realistic reaction conditions. Both active phases were stable under reaction conditions, with no evidences of deactivation in consecutive combustion experiments. The presence of H2O and CO2 together with NOx and O2 in the gas mixture slightly delays soot combustion to higher temperatures, but the effect is equal for the Pt and CePr active phases. The mass of soot loaded into the filters had no effect in the catalytic regeneration of the DPFs for soot:catalyst weigh ratios below 0.4, while it was hindered above this ratio. The Pt and CePr active phases behave equal until 0.6 soot:catalyst weigh ratio and Pt performance was slightly better for higher soot loading. This difference is explaining according to the main soot combustion mechanisms occurring during Pt–DPF (NO2-assited) and CePr–DPF regeneration (active oxygen). The CO2 selectivity is near 100% for both catalysts in all the experimental reaction conditions evaluated. According to this study, the CePr active phase seems to be a promising candidate to replace Pt in real applications.

Impact on vehicle fuel economy of the soot loading on diesel particulate filters made of different substrate materials

Wall flow DPFs (Diesel Particulate Filters) are nowadays universally adopted for all European passenger cars.Since the properties of the filter substrate material play a fundamental role in determining the optimal soot loading level to be reached before DPF regeneration, three different filter material substrates (Silicon Carbide, Aluminum Titanate and Cordierite) were investigated in this work, considering different driving conditions, after treatment layouts and regeneration strategies.In the first step of the research, an experimental investigation on the three different substrates over the NEDC (New European Driving Cycle) was performed. The data obtained from experiments were then used for the calibration and the validation of a one dimensional fluid-dynamic engine and after treatment simulation model. Afterward, the model was used to predict the vehicle fuel consumption increments as a function of the exhaust back pressure due to the soot loading for different driving cycles. The results showed that appreciable fuel consumption increments could be noticed only in particular driving conditions, and, as a consequence, in most of the cases the optimal filter regeneration strategy corresponds to reach the highest soot loading that still ensures the component safety even in case of uncontrolled regeneration events.

Extending the environmental benefits of ethanol–diesel blends through DGE incorporation

The research focuses on the potential use of DGE (diethylene glycol diethyl ether), as a high-cetane number oxygenated additive to diesel-like fuels. Apart from evaluating its individual effects an investigation of how DGE can facilitate the use of bio-ethanol in diesel engines was conducted; which faces many technical difficulties, but can provide environmental advantages over biodiesel and conventional diesel fuel. Four partly renewable fuel blends with varying contents of DGE and ethanol were designed with overall diesel-replacement rate of 20%. DGE was found to reduce gaseous emissions, achieving a simultaneous reduction in both soot and NOx which highlighted the beneficial effects of its high cetane number and oxygen content. In ethanol–diesel blends small additions of DGE significantly enhanced blend stability and blend auto-ignition properties. Improvements in the NOx/soot trade-off characteristics were obtained for all blends. All tested blends produced lower particulate matter number concentrations and soot with characteristics that reduced their oxidation temperatures, hence providing benefits for diesel particulate filter (DPF) regeneration. Overall it was found that DGE fuel provides considerable energy and environmental benefits if used both as a single oxygenate with diesel or in multicomponent blends with ethanol and diesel.

Progression of Soot Cake Layer Properties During the Systematic Regeneration of Diesel Particulate Filters Measured with Neutron Tomography

Although particulate filters (PFs) have been a key component of the emission control system for modern diesel engines, there remain significant questions about the basic regeneration behavior of the filters and how it changes with accumulation of increasing soot layers. This effort describes a systematic deposition and regeneration of particulate matter in 25-mm diameter × 76-mm long wall-flow PFs composed of silicon carbide (SiC) material. The initial soot distributions were analyzed for soot cake thickness using a nondestructive neutron imaging technique. With the PFs intact, it was then possible to sequentially regenerate the samples and reanalyze them, which was performed after nominal 20, 50, and 70 % regenerations. The loaded samples show a relatively uniform distribution of particulate with an increasing soot cake thickness and nearly identical initial density of 70 mg/cm3. During regeneration, the soot cake thickness initially decreases significantly while the density increases to 80–90 mg/cm3. After ∼50 % regeneration, the soot cake thickness stays relatively constant, but instead, the density decreases as pores open up in the layer (∼35 mg/cm3 at 70 % regeneration). Complete regeneration initially occurs at the rear of the PF channels. With this information, a conceptual model of the regeneration is proposed.

Emissions from Light-Duty Diesel and Gasoline in-use Vehicles Measured on Chassis Dynamometer Test Cycles

The reduction in vehicle exhaust emissions achieved in the last two decades is offset by the growth in traffic, as well as by changes in the composition of emitted pollutants. The present investigation illustrates the emissions of eight in-use gasoline and diesel passenger cars using the official European driving cycle and the ARTEMIS real-world driving cycles. Measurements comprised gaseous regulated pollutants (CO, CO2, NOx and hydrocarbons), particulate matter and its carbonaceous content (organic and elemental carbon, OC and EC), as well as about 20 different volatile organic compounds (VOCs) in the C6–C11 range. It was observed that some of the vehicles do not comply with the corresponding regulations. Significant differences in emissions were registered between driving cycles. Not all regulated pollutants showed a tendency to decrease from Euro 3 to Euro 5. The particulate carbon emission factors were significantly lower under the ARTEMIS Road compared with the ARTEMIS Urban driving cycle with cold start. In general, cold start-up driving conditions produced the highest emission factors. A tendency to the decline of carbonaceous emissions from Euro 3 to Euro 5 diesel vehicles was observed, whilst this trend was not registered for petrol-powered cars. The fraction of total carbon composed of EC was much lower in particles emitted by petrol vehicles (< 10%) than by diesel engines (50–95%). However, the EC content in emissions from more modern vehicles equipped with diesel particulate filter (DPF) is almost negligible. Among VOCs, benzene, toluene and xylenes were generally the dominant species. A significant decrease in emissions from Euro 4 to Euro 5 petrol-powered vehicles was observed. The trend in VOC emissions is unclear when diesel engines are considered. During DPF regeneration cycles, pollutant emissions are several times larger than those during normal engine operation.