Diesel Aftertreatment Systems Research Articles

N2O Formation and Mitigation in Diesel Aftertreatment Systems

N₂O Formation and Mitigation in Diesel Aftertreatment Systems

Fuel Injector Optimization for Diesel Aftertreatment Systems Coupled with Exhaust Aftertreatment System Performance on a Heavy-Duty Diesel Engine Powered Vehicle

Fuel Injector Optimization for Diesel Aftertreatment Systems Coupled with Exhaust Aftertreatment System Performance on a Heavy-Duty Diesel Engine Powered Vehicle

Computational study on the effects of volume ratio of DOC/DPF and catalyst loading on the PM and NOx emission control for heavy-duty diesel engines

The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance. One of the favorable PM regeneration technologies is the NO2-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion efficiency of NO2 from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft3 of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m2/gpt was enough to maximize the conversion efficiency and oxidation rate of PM.

A Novel Accelerated Aging System to Study Lubricant Additive Effects on Diesel Aftertreatment System Degradation

A Novel Accelerated Aging System to Study Lubricant Additive Effects on Diesel Aftertreatment System Degradation

Investigation of Active Flow Control on Diesel Engine Aftertreatment

Theoretical studies are performed with one-dimensional transient modeling techniques to analyze the thermal behavior of the diesel aftertreatment systems when active flow control schemes are applied. The combined use of activegas flowandactivefueling-controlschemesareidentifiedtobecapableofshiftingtheexhaustgastemperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. Several external fuel-supplying techniques are applied and analyzed with various heat distribution patterns and exhaust flow control parameters. The analysis indicates that the active flow control schemes have fundamental advantages in optimizing the converter thermal management that includes supplemental heating, thermal retention, thermal recuperation, and overheating protection. Modeling validation analyses with selected experiments are also reported.

OS-B1: Development of Advanced NO_x Storage-Reduction Catalyst System for Cleaner Diesel Aftertreatment(OS-B Advanced Technology of After-treatment System(Achievement of Ultra Low Emission),Organized Session Papers)

Diesel particulate and NO_x Reduction system (DPNR) is an effective device for clean diesel aftertreatment system. The NO_x reduction is using NO_x Storage and Reduction (NSR) mechanism. However, NSR catalyst has some issues about deterioration. Therefore, further improvement is hoped for cleaner air in the future. This paper reviews the results of our study to improve the NO_x reduction performance of NSR system. NSR catalyst performance decreases because of thermal stress and sulfur poisoning. In order to improve the thermal resistance of the catalyst, we have studied the suppression of precious metal sintering using Pt-O-Ce bond. As a result, higher catalytic activity after aging especially under lower temperature condition was obtained. On the other hand, improvement for the sulfur tolerance is one of the key technologies to keep the high NO_x conversion efficiency. The temperature uniformity of NSR catalyst on desulfurization control and the catalyst improvement are effective for higher sulfur tolerance. In addition to these suppressions of the deterioration, NO_x reduction method is also important factor. The NO_x reduction method by in-cylinder rich is effective at lower temperature, and by on-catalyst rich using exhaust diesel fuel injection is also effective at higher temperature. Therefore, this combination is a beneficial solution. As a result of these improvements, it is shown that the NSR catalyst has higher NO_x conversion efficiency of over 70% on New European Driving Cycle (NEDC) mode. Moreover, sulfur trap concept has more potential with lower Platinum Group Metal (PGM) loading thanks to improvement of thermal and sulfur tolerance.

Three-dimensional modelling of NOx and particulate traps using CFD: A porous medium approach

Lean burn after-treatment systems are the current focus for reducing emissions from diesel exhaust. The trend is for commercial CFD packages to use a single channel modelling approach. Due to computational demands, this necessitates specification of representative channels for modelling, implying prior knowledge of the flow field. This paper investigates a methodology for applying the porous medium approach to lean burn after-treatment systems. This approach has proved successful for three-way catalysis modelling and has the advantage that the flow field is predicted. Chemical kinetic rates for NO x trapping and regeneration in the model are based on information available in the open literature. Similarly, filtration information based on mass accumulation and soot combustion kinetics are also readily available. Modification of the source terms in a commercial CFD package enables prediction of trapping and release of NO x . This is an effective way to model a NO x trap after-treatment system and provides simultaneous 3D modelling of the flow field. With diesel, particulate filtration is required. In the case of particulate traps, however, because of channel geometry, some assumptions are necessary for use of the porous medium approach and these are discussed in this paper. Both models produce qualitatively correct output and have parameters that can be tuned to conform to experimental data. Data to validate the NO x trap model is to be measured. The particulate trap model, on the other hand, is a feasibility study for modelling the complete diesel after-treatment system using the porous medium approach.

The attainment of premixed compression ignition low-temperature combustion in a compression ignition direct injection engine

This study theoretically proposes and experimentally demonstrates the simultaneous reductions of exhaust nitric oxide (NO) and soot via the attainment of premixed compression ignition (PCI) combustion in a modern compression ignition direct injection (CIDI) engine. The key features leading to PCI combustion are a well-mixed fuel–air mixture, following a long ignition delay period, which burns at relatively low temperature. It is shown that simultaneous reductions in exhaust NO and soot concentrations are possible with the implementation of PCI combustion. At very low combustion temperatures, soot formation mechanisms decrease substantially so that both NO and soot formation have very little dependence on local equivalence ratios. As a result, it becomes possible to increase the global equivalence ratio above stoichiometric, and produce rich products of combustion for regeneration of certain diesel aftertreatment systems.