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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.

Among the durability items of the DPF (Diesel Particulate Filter), high accumulated soot mass limit is important for the low fuel consumption and also for the robustness. In case of catalyzed DPF, it depends on the following two properties during soot regeneration. One is the lower maximum-temperature inside of the DPF during usual regeneration in order to preserve the catalyst performance. The other is the higher thermal resistance against the unusual regeneration of excess amount of soot. This paper presents the improvement in the soot mass limit of Si bonded SiC DPF. Maximum-temperature inside of the DPF was lowered by the improvement of thermal conductivity of the material, resulted from the controlling of the microstructure. Additionally the thermal resistance was improved by the surface treatment of the Si and SiC.

Reducing the fuel consumption of powertrains in internal combustion engines is still a major objective from an environmental viewpoint. Internal combustion engines waste a huge part of the fuel energy as heat in the exhaust line. Currently, exhaust heat recovery (EHR) systems are attracting attention as an effective means of reducing fuel consumption by collecting heat from waste exhaust gas and using it for rapid warming up of the engine and cabin heating [1, 2, 3, 4]. The benefits of the EHR system are affected by a trade-off between the efficacy of the recovered useful thermal energy and the adverse effect of the additional weight (heat mass) of the system [5]. Conventional EHR systems have a complex heat exchanger structure and a structure in which a bypass pipe and heat exchanger are connected in parallel, giving them a large size and heavy weight. We have developed a new-concept silicon carbide (SiC) heat exchanger with a dense SiC honeycomb.

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.

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.

Partially stabilized zirconia is an insulating ceramic which offers high strength, high thermal expansion, and wear resistance. Low thermal conductivity provides the required insulation, high strength improves reliability, and high thermal expansion provides a simple means of attachment for ceramic engine components. Pistons, cylinder liners, and cylinder heads have been insulated with PSZ and engine tested in an adiabatic diesel engine.