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New Particulate Matter Sensor for On Board Diagnosis

2012-02-16
The presentation describes technology developments and the integration of these technologies into new emission control systems. As in other years, the reader will find a wide range of topics from various parts of the world. This is reflective of the worldwide scope and effort to reduce diesel exhaust emissions. Topics include the integration of various diesel particulate matter (PM) and Nitrogen Oxide (NOx) technologies as well as sensors and other emissions related developments. Presenter Atsuo Kondo, NGK Insulators, Ltd.
Technical Paper

Development of the NOx Adsorber Catalyst for Use with High-Temperature Condition

2001-03-05
2001-01-1298
NOx adsorber has already been used for the after-treatment system of series production vehicle installed with a lean burn or direct injection engine [1,2,3]. In order to improve NOx adsorbability at high temperatures, many researchers have recently been trying an addition of potassium (K) as well as other conventional NOx adsorbents. Potassium, however, reacts easily with the cordierite honeycomb substrate at high temperatures, and not only causes a loss in NOx adsorbability but also damages the substrate. Three new technologies have been proposed in consideration of the above circumstances. First, a new concept of K-capture is applied in washcoat design, mixed with zeolite, to improve thermal stability of K and to keep high NOx conversion efficiency, under high temperatures, of NOx adsorber catalyst. Second, another new technology, pre-coating silica over the boundary of a substrate and washcoat, is proposed to prevent the reaction between potassium and cordierite.
Technical Paper

Performance of Thick Film NOx Sensor on Diesel and Gasoline Engines

1997-02-24
970858
This paper describes a thick film ZrO2 NOx sensor feasible for diesel and gasoline engine applications, and introduces modification items from the previous concept design.(1) The modification items comprise simplifying the sensing element design to reduce output terminals for package design and applying temperature control to the sensing element in order to minimize sensor performance dependency on gas temperature. The NOx sensor indicates a stable linear signal in proportion to NOx concentration in a wide range of temperature, A/F and NOx concentration as a practical condition on both gasoline and diesel engines. The NOx sensor shows a good response in hundred msec. and a sharp signal following NOx generation in a transient state as well. Besides, another type of a NOx sensor is proposed for low NOx measurement in a practical use, by an electromotive force(EMF) voltage instead of a pumping current.
Technical Paper

Design Development of High Temperature Manifold Converter Using Thin Wall Ceramic Substrate

1997-02-24
971030
This paper proposes a high temperature manifold converter with a thin wall ceramic substrate, such as; 4mil/400cpsi and 4mil/600cpsi. Double-wall cone insulation design was proposed for close-coupled converters to protect the conventional intumescent mat from high temperature. However, the double wall cone insulation is not applicable when the converter is directly mounted to the exhaust manifold without an inlet cone. The prototype manifold converter was tested under hot vibration test with a non-intumescent ceramic fiber mat and retainer rings as a supplemental support. The converter demonstrated durability for 10 hours under 80G acceleration and 100 hours under 60G acceleration with 1,050 °C catalyst bed temperature. The skin temperature of the heat shield was kept below 400 °C.
Technical Paper

Advanced Ceramic Substrate: Catalytic Performance Improvement by High Geometric Surface Area and Low Heat Capacity

1997-02-24
971029
Catalytic performance can be improved by increasing geometric surface area (GSA) and reducing bulk density (BD), namely heat capacity, using high cell-density / thinwall advanced ceramic substrates. The advanced substrates, such as 3 mil/600 cpsi and 2 mil/900 cpsi have improved the catalytic performance over the conventional substrates, and are expected to help in complying with future emission regulations, as well as catalyst downsizing. This paper describes the effects of GSA and BD using Pd-based catalysts. The reduction of hydrocarbons emissions was demonstrated significantly at close-coupled location, and dual bed design was proven effective. The effectiveness at under-floor location was not as significant as the close-coupled location.
Technical Paper

A Structurally Durable EHC for the Exhaust Manifold

1994-03-01
940466
It is well known that an EHC (Electrically Heated Catalyst) is very effective in reducing cold start HC emissions. However, the large electric power consumption of the EHC is a major technical issue. When installed in the exhaust manifold, the EHC can take advantage of exhaust heat to warm up faster, resulting in a reduced electric power demand. Therefore, a structurally durable EHC which can withstand the severe manifold conditions is desirable. Through the use of a extruded monolithic metal substrate, with a flexible hexagonal cell structure and a special canning method, we have succeeded in developing a structurally durable EHC. This new EHC installed in the exhaust manifold with a light-off catalyst directly behind it demonstrated a drastic reduction in FTP (Federal Test Procedure) Total HC emissions.
Technical Paper

Thick Film ZrO2 NOx Sensor

1996-02-01
960334
This paper describes the design concept and evaluation test results of a multi-layered, thick film zirconia NOx sensor which can be used for lean-burn engine management. The oxygen concentration in the measuring gas is lowered to a predetermined level with an oxygen pumping cell, in the first stage. In the second stage, another pumping cell further lowers the oxygen concentration which results in simultaneous NOx decomposition. The second stage pumping current is proportional to the NOx concentration in the measuring gas.
Technical Paper

Exhaust Gas Temperature Sensor for OBD-II Catalyst Monitoring

1996-02-01
960333
This paper describes a newly-developed, high-performance RTD,(Resistive Temperature detector), which meets OBD-II monitoring requirements. The OBD-II catalyst monitoring requirements are high temperature durability, high accuracy, and narrow piece-to-piece variation. Catalyst monitoring methods have been reviewed and studied by checking the catalyst exotherm(1)(2). The preliminary test results of catalyst monitoring are also described herein.
Technical Paper

The Development of an Automotive Catalyst using a Thin Wall (4 mil/400cpsi) Substrate

1996-02-01
960557
Since the monolithic ceramic substrate was introduced for automotive catalytic converters, the reduction of the substrate wall thickness has been a continuing requirement to reduce pressure drop and improve catalytic performance. The thin wall substrate of 0.10 mm (4 mil) thick wall/400 cpsi cell density has been introduced to production by achieving mechanical strength equivalent to a conventional 0.15 mm (6 mil)/400 cpsi substrate. Although a round cross-section substrate can have a reduced catalyst volume compared to an oval cross-section substrate because of uniform gas flow distribution, the smaller cross-section of the round substrate increases pressure drop. The thin wall technology was applied to the round substrate to offset the pressure drop increase and to further improve catalytic performance.
Technical Paper

Thermal Reliability and Performance Improvement of Close-Coupled Catalytic Converter

1996-02-01
960565
This paper proposes a high temperature catalytic converter design using a ceramic substrate and intumescent matting. It also describes the improvement of converter performance using an advanced thin wall ceramic substrate. Due to future tightening of emission regulations and improvement of fuel economy, higher exhaust gas temperatures are suggested. Therefore, reduction of thermal reliability of an intumescent mat will be a concern because the catalytic converter will be exposed to high temperatures. For this reason, a new design converter has been developed using a dual cone structure for both the inlet and outlet cones. This minimizes heat conduction through the cone and decreases the temperature affecting the mat area. This design converter, without the use of a heat-shield, reduces the converter surface temperature to 441°C despite a catalyst bed temperature of 1050°C. The long term durability of the converter is demonstrated by the hot vibration test.
Technical Paper

In-line Hydrocarbon (HC) Adsorber System for Cold Start Emissions

1997-02-24
970266
In order to meet the strict automobile emission regulations in the U.S.A. and Europe, new aftertreatment technologies such as the EHC and HC Adsorber have been developed to reduce the cold start emissions. The EHC is obviously effective in reducing emissions, but has the demerits of a large electric power demand and a complicated power control system to support it (13). A by-pass type HC adsorber system has the concerns of unreliable by-pass valves and complicated plumbing (10). A major technical challenge of the in-line type HC adsorber was the difference between the HC desorption temperature and the light-off temperature of the burn-off catalyst. This paper describes the evaluation results of a completely passive “In-line HC Adsorber System” which can reduce the cold start emissions without the application of any type of mechanical or pneumatic control valve in the exhaust system.
Technical Paper

Development of Wall-Flow Type Diesel Particulate Filter System with Reverse Pulse Air Regeneration

1994-03-01
940237
The effects of the factors of reverse pulse air regeneration; pulse air pressure, pulse air time and pulse air interval, were evaluated. Pulse air pressure significantly affects a DPF's pressure drop increase. Pulse air time and pulse air interval do not greatly affect a DPF's pressure drop. Current DPFs and samples with modified materials were tested. The pressure drop increse varied with the material properties, such as mean pore size and porosity. Current DPFs are applicable to a DPF system with reverse pulse air regeneration. There is the possibility to get an optimum DPF for the reverse pulse air regeneration system by changing the mean pore size, porosity and/or other properties.
Technical Paper

Study of Ceramic Catalyst Optimization for Emission Purification Efficiency

1994-03-01
940784
In this study, to satisfy increasingly strict emission regulations, the conversion efficiency of a 0.11 mm (4 mil) thin-wall catalyst is discussed. The effects of catalyst bulk density on reducing heat mass to improve catalyst emission conversion in the early cold transient mode (Bag 1 in the FTP-75 mode) is quantitatively discussed. To analyze the effects of low heat mass, catalyst's bed temperatures were measured. Effects of the geometric surface area (GSA) and volume of the catalyst were also analyzed. An early feedback control system with an HEGO oxygen sensor and a secondary air injection control system with an original oxygen sensor were compared with an original control system on THC, CO, and NOx emission amounts.
Technical Paper

Optimization of Catalytic Converter Location Achieved with a Curve Catalytic Honeycomb Substrate

1994-03-01
940743
A new type of catalytic converter has been developed for the coming TLEV (Transitional Low Emission Vehicle) standards. It is a “Front Curve Catalytic Converter (FCCC)” using a curved cordierite ceramic honeycomb substrate. During this development, an optimum location and volume of the front curve catalytic converter were determined from the view points of thermal deterioration of the catalyst and hydrocarbon conversion performance. Based on CAE (Computer Aided Engineering) analysis, the best curvature radius of the substrate was selected to minimize a pressure drop of the front curve catalytic converter. The emission conversion and light-off performances of the front curve catalytic converter were compared with a conventional straight design. A series of durability tests; hot vibration, engine dynamometer and vehicle fleet tests were also conducted to confirm the reliability of the new front curve catalytic converter.
Technical Paper

In-line Hydrocarbon Adsorber for Cold Start Emissions - Part II

1998-02-23
980423
The in-line hydrocarbon (HC) adsorber is a passive after-treatment technology to address cold-start hydrocarbons in automotive engine exhaust gas. A major technical challenge of the in-line HC adsorber is the difference between the HC release temperature of the adsorber and the light-off temperature of the burn-off (BO) Catalyst. We call this phenomenon the “reversed-temperature difference”. To reduce the reversed temperature difference, NGK has proposed a new “In-line HC Adsorber System” which consists of light-off (LO) Catalyst + Barrel Zeolite Adsorber (BZA), with a hole through the center, BO Catalyst and secondary air injection management (SAE 970266). This, our latest paper, describes the evaluation of various adsorbents and the effect of the center hole on the Adsorber BZA. The adsorber system, which had the Adsorber BZA with a 25mm ϕ center hole and adsorbent coated, confirmed 30% lower FTP NMHC emission versus a system with no center hole or adsorbent coating.
Technical Paper

Thick Film ZrO2 NOx Sensor for the Measurement of Low NOx Concentration

1998-02-01
980170
A practical ZrO2 NOx sensor using dual oxygen pumping cells has been introduced for the control of NOx emitted from a lean-burn gasoline engine and diesel engine.(1),(2). However, the measuring accuracy was not high enough to be useful for controlling or monitoring a low level of NOx concentration such as several tens ppm behind a three way catalyst or lean NOx catalyst which is NOx adsorption or De-NOx catalyst. This paper describes improvement of the interference effect of oxygen in the exhaust gas from the lean-burn gasoline engine and diesel engine. The cause of oxygen dependency is analyzed/revealed and a method of improvement is introduced. The improved NOx sensor has an approximately · · 2% measuring error in the wide range of oxygen concentration on a model gas system, compared to the · ·10% of the previous one.
Technical Paper

Reduction of Wall Thickness of Ceramic Substrates for Automotive Catalysts

1990-02-01
900614
Ceramic honeycombs have been used as automotive catalyst supports in US, Japan, Europe and other highly urbanized countries. Now, engine output is a great concern for automanufacturers, and reduction of the wall thickness of honeycomb substrates became indespensable for maintenance of gas flow restriction to a certain low level. To reduce wall thickness, material should be strong to maintain canning strength of substrates. Mechanical strength was improved with high density cordierite. However, isostatic strength of whole substrates was still insufficient with reduced thin walls for canning in spite of the material's high mecanical strength. Discussion is carried out on further possibility of improving canning performance of thin wall substrates as well as flow restriction, and warm up characteristics.
Technical Paper

Warm-Up Characteristics of Thin Wall Honeycomb Catalysts

1991-02-01
910611
HC emission standards will be tightened during the 1990's in the US. A key issue in reducing HC emission is improving the warm-up characteristics of catalysts during the cold start of engines. For this purpose, studies are under way on reduction of heat mass of ceramic substrates. Reduction of cell walls in substrates to thickness smaller than the current thickness of 12mil or 6mil has resulted in reduced heat mass, and also reduced flow restriction of substrates. The warm-up characteristics of low bulk density catalysts are better than those of high bulk density, i.e., the warm-up characteristics of thinner wall or lower cell density catalysts are better than those of thicker wall or higher cell density catalysts. A relationship between geometric surface area and warm-up characteristics is observed.
Technical Paper

Electric Heating Regeneration of Large Wall-Flow Type DPF

1991-02-01
910136
Ceramic wall-flow type diesel particulate filters (DPF) are being investigated for the aftertreatment systems of heavy duty engines. To use ceramic DPF more reliably and easily, electric heating regenerations are studied varying combustion air flow rates and amounts of accumulated soot. Despite electric heater capacity limitations, it is possible to regenerate DPF at a certain combustion air flow rate without thermal shock failure. The maximum withstood temperature against thermal shock failure of electric heating regeneration is similar to that of diesel burner regeneration on DPF with a nine inch diameter and a twelve inch length.
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