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Fujii S.,NGK Automotive Ceramics United States Inc. | Asako T.,NGK Ceramics United States Inc.
SAE Technical Papers | Year: 2010

Ash accumulation is a considerable factor for long-term Diesel Particulate Filter (DPF) performance. Ash accumulation reduces the open frontal area (OFA) and plugs the surface pores. As a result, DPF back pressures with no soot (hereinafter "initial DPF back pressure") rise. At the same time, DPF back pressures with soot (hereinafter "sooted DPF back pressure") fall [ 1, 2, 3, 4 ]. Then sooted DPF back pressures rise after the reductions of the certain ranges [ 1, 3, 4 ]. It is known that DPF back pressure behaviors change variously by ash loading like this. The understanding of DPF back pressure behaviors with ash accumulation is indispensable for proper after-treatment system management. Ash accumulation progresses slowly and gradually in DPF while using of vehicles. Because of the slowness, the field surveys require a few years at least. To evaluate the effects within shorter terms, various accelerated test methods (ex. burning of lubricant oil [ 3, 4 ], mixing of lubricant oil in fuel [ 5, 6 ], and introduction of lubricant oil mist in intake air [ 7, 8 ]) have been reported as alternative test methods. The test periods require a couple of months because the accelerations of those test methods were restricted by consumption rate of lubricant oil. An artificial ash accelerated accumulation (AAAA) test was attempted for drastic shortening of the test periods. This paper describes the procedures and results obtained by the attempt. The results are compared with literature and the validity of proposed test method is discussed. Copyright © 2010 SAE International.

Fujii S.,NGK Automotive Ceramics United States Inc. | Asako T.,NGK Ceramics United States Inc. | Yuuki K.,Ngk Insulators
SAE Technical Papers | Year: 2010

To evaluate various Diesel Particulate Filter (DPF) efficiently, accelerated tests are one of effective methods. In this study, a simulator composed by diesel fuel burners is proposed for fundamental DPF evaluations. Firstly particle size distribution measurement, chemical composition and thermal analysis were carried out for the particulate matter (PM) generated by the simulator with several combustion conditions. The PMs generated by specific conditions showed similar characteristics to PMs of a diesel engine. Through these investigations, mechanism of PM particle growth was discussed. Secondly diversified DPFs were subjected to accelerated pressure drop and filtration efficiency tests. Features of DPFs could be clarified by the accelerated tests. In addition, the correlation between DPF pressure drop performance and PM characteristics was discussed. Thirdly regeneration performance of the simulator's PM was investigated. The PM oxidation occurred intensively at lower temperature than that of an engine. The pressure drop of the simulator's PM was higher than that of an engine. These differences between the simulator and engine might be almost explained by PM characteristics investigated in this study. © 2010 SAE International.

Dimou I.,Massachusetts Institute of Technology | Sappok A.,Massachusetts Institute of Technology | Wong V.,Massachusetts Institute of Technology | Fujii S.,NGK Automotive Ceramics United States Inc. | And 4 more authors.
SAE Technical Papers | Year: 2012

Diesel particulate filters (DPF) are a common component in emission-control systems of modern clean diesel vehicles. Several DPF materials have been used in various applications. Silicone Carbide (SiC) is common for passenger vehicles because of its thermal robustness derived from its high specific gravity and heat conductivity. However, a segmented structure is required to relieve thermal stress due to SiC's higher coefficient of thermal expansion (CTE). Cordierite (Cd) is a popular material for heavy-duty vehicles. Cordierite which has less mass per given volume, exhibits superior light-off performance, and is also adequate for use in larger monolith structures, due to its lower CTE. SiC and cordierite are recognized as the most prevalent DPF materials since the 2000's. The DPF traps not only combustible particles (soot) but also incombustible ash. Ash accumulates in the DPF and remains in the filter until being physically removed. Several studies have confirmed that a small amount of ash accumulation in the DPF (until a certain level) improves DPF performance, both in terms of filtration efficiency and sooted back pressure [1, 2, 3, 4]. On the other hand, it has also been confirmed that too much ash accumulation increases exhaust back pressure, leading to a reduction in engine efficiency, as the ash occupies space and plugs the DPF. In some cases, periodic ash cleaning, which requires removal of the DPF from the vehicle, is needed to ensure appropriate DPF performance, especially for heavy-duty diesel vehicles which accumulate high mileage. Thus, accumulation of ash in the DPF is a common and considerable issue for long-term vehicle operation, regardless of the filter material. Improved understanding of the phenomena of ash accumulation in the DPF is valuable for further improvement of the emission-control system. In this study, four different non-catalyzed DPF materials (three different porosities and two different pore sizes) of rectangular configuration 38mm × 38mm × 152mm, made of SiC were subjected to accelerated ash loading. In addition, a non-catalyzed cordierite DPF was also evaluated to determine the influence of the DPF material. Ash loading at five different levels from 0 to 20 g/L was conducted. Twenty five ashed DPF samples in total were prepared for this investigation. The DPF back pressure response to soot loading was verified by a soot generator for all samples. The phenomenon of ash accumulation and its effects on the sooted DPF back pressure response was investigated, resulting in the formulation of DPF design criteria to reduce ash-related impact on lifetime DPF performance. Copyright © 2012 SAE International.

Hirose S.,Ngk Insulators | Miyairi Y.,Ngk Insulators | Katsube F.,Ngk Insulators | Yuuki K.,Ngk Insulators | And 3 more authors.
SAE Technical Papers | Year: 2012

Ammonia Selective Catalytic Reduction (SCR) and Lean NOx Trap (LNT) systems are key technologies to reduce NOx emission for diesel on-highway vehicles to meet worldwide tighter emission regulations. In addition DeNOx catalysts have already been applied to several commercial off-road applications. Adding the DeNOx catalyst to existing Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) emission control system requires additional space and will result in an increase of emission system back pressure. Therefore it is necessary to address optimizing the DeNOx catalyst in regards to back pressure and downsizing. Recently, extruded zeolite for DeNOx application has been considered. This technology improves NOx conversion at low temperature due to the high catalyst amount. However, this technology has concerned about strength and robustness, because the honeycomb body is composed of catalyst. A zeolite catalyst supported by a ceramic honeycomb structure resolves the strength and robustness issues. Also the honeycomb structure offers higher geometric surface area (GSA), a key characteristic for higher NOx conversion. Cordierite substrates with a honeycomb structure are a historically proven technology used for a variety of applications (gasoline, diesel, LDV, HDV, Non-Road) over the past 30 years. Cordierite substrates have been used widely for three-way catalyst (TWC) and DOC as well as ammonia SCR and LNT for several decades. However, today's DeNOx catalyst technologies require higher catalyst loading to ensure very high conversion efficiencies at lower temperature. Conventional cordierite substrate has not been optimized for high catalyst loadings for DeNOx catalysts applications. By modifying cordierite substrate material properties for high catalyst loadings, lower pressure drop and retention of high NOx conversion efficiency can be offered. In this investigation, the performances of newly developed cordierite substrates with material properties adjusted to address high catalyst loadings and in various geometrical configurations were compared to conventional substrate technology. The performance evaluation includes NOx conversion, pressure drop performance, as well as durability and material strength evaluation. The paper will discuss the opportunities this newly developed material provides in regards to compactness and low pressure drop while maintaining high NOx conversion efficiency. Copyright © 2012 SAE International.

Kawakami A.,Ngk Insulators | Fukumi Y.,Ngk Insulators | Ito M.,Ngk Insulators | Sokawa S.,Ngk Insulators | And 5 more authors.
SAE Technical Papers | Year: 2016

Honeycomb substrates are widely used to reduce harmful emissions from gasoline engines and are exposed to numerous thermal shocks during their lifetime making thermal shock resistance one of the key factors in designing honeycomb substrates. More stringent emission regulations will require the honeycomb substrates to be lighter in weight to improve light-off performance and to have better thermal shock resistance than conventional honeycomb substrates to handle higher expected temperature gradients. Thermal shock resistance is generally evaluated on a substrate by evaluating the thermal strain caused by temperature gradients inside the substrate during durability testing [1,2]. During the test, a heated substrate is cooled at a surface face to generate temperature gradients while the temperature inside the honeycomb substrate is monitored by multiple thermocouples. Next generation lighter weight substrates have equal or lower thermal capacity than the installed thermocouples causing the measurement to show a slower temperature change than the actual substrate and would, therefore, misrepresent the thermal shock resistance. This paper describes a new evaluation method for thermal shock resistance of honeycomb substrates. It uses a newly developed analysis method which can eliminate the delay in measurement response by thermocouples. The method consists of experimenting with a thermal imaging camera and thermocouples and data analysis, taking into account the heat capacity and thermal conduction of honeycomb substrates and thermocouples. This method enables the calculation of the rapid thermal behavior of lighter weight substrates. © 2016 SAE International.

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