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Our two types of NOx storage-reduction (NSR) catalyst have been tested under various conditions of thermal endurance; the performance of these catalysts have been regressed to give the formulas that enable to estimate the performance after thermal endurance; and we have found the method to simplify (shorten the duration of) the thermal endurance tests and that the thermal deterioration of NSR catalysts is controlled by the worst condition of endurance (at least approximately). The regression formula for the amount of potassium that contributes to the catalyst performance (active K) after the endurance has also been obtained. These formulas predict that the amount of active K is the least for the worst condition of endurance and suggest a difference in deterioration mechanism that reflects the performance between low and high temperatures and the portion of worse deterioration (front or rear).

Two effects of rich-spike duration on NOx-storing have been analyzed. The first one, that NOx-storing speed decreases as rich-spike duration increases, is explained as the influence of NOx diffusion in wash-coat layer, which is quantified by a simple mathematical expression for NOx-storing rate. The second one, a peculiar behavior of NOx-storing in appearance of the outlet NOx concentration, is clarified: Heat produced directly or indirectly (via oxygen storage in ceria) by rich-spike warms up the downstream part, which releases excess NOx at the raised temperature. Contributions of the oxygen storage and the carbonate of NOx-storage material are also discussed.

This paper presents the numerical simulation method to predict the deactivation process of three-way catalytic converters. Three-way catalytic converter's deactivation typically results from thermal and chemical mechanisms. The major factor of thermal deactivation is the sintering of noble metal particles, which is known to depend on the ageing temperature and the oxygen concentration in the exhaust gas. The chemical deactivation is mainly caused by the poisoning, which has two effects on the catalyst deactivation. One effect is the loss of the catalyst activity, which is expressed by reduced frequency factors of reaction rates. Another effect is the suppression of the noble metal sintering. Poison deposits prevent the noble metal particles from moving in the washcoat, assisted by the reduced thermal loading of reaction heats, which is caused by the loss of the catalyst activity. Modeling these deactivation factors, we propose the rate expression of noble metal sintering.

Squish flow control is well known as a key technology for improving knock limit in spark ignition engines. However, to acquire a sufficient squish area in a four-valve engine is difficult. In order to achieve a maximum effect of knock suppression with a minimum squish area, we have developed, what we call, a Slant Squish Combustion Chamber for new engines. A slant squish compared with a conventional squish produces an effective reverse squish flow in the early expansion stroke, resulting in higher flow velocity and turbulence. Furthermore, flame propagation to squish area and end gas is accelerated. These improvements are considered to suppress the knock phenomenon. Consequently, with a slant squish, a high compression ratio, to achieve low fuel consumption and high engine performance is realized.

This paper deals with oxygen storage effect and NOx conversion reaction modeling. It was found that the oxygen stored in the catalyst increases with catalytic wall temperature and lean ( or rich ) depth from experiments using a well controlled flow reactor. Oxygen storage-release model (OSR model), incorporated with the NOx reduction reaction and THC or CO oxidation reaction, was established from the experimental results. Reaction rate parameters for three-way catalyst have been determined from the least data of flow reactor experiments using Evolutionary Algorithm. Transient temperatures and emissions are predicted using the developed OSR model and the determined reaction rate parameters for three-way catalyst, which are incorporated in the numerical algorithms used in the previous paper to predict flow and temperature field in a catalytic converter.

The laser-induced exciplex fluorescence (LIEF) technique, currently used to observe mixture formation in a diesel engine, has been applied to a spark ignition (SI) engine and a new equivalence ratio calibration technique has been developed in order that two-dimensional measurements of the equivalence ratio may be made in an operating engine. Spectrally separated fluorescent images of liquid and vapor phase fuel distributions were obtained by adding new exciplex-forming dopants to the gasoline fuel. Dual light sheets from an excimer laser were introduced into one of the cylinders of a 4-valve lean-burn engine, and 2-D images of the mixture formation were recorded at pre-set crank angles during the induction and compression strokes by an image-intensified camera equipped with the appropriate filter.

A new type of rapid compression and expansion machine (RCEM) has been developed, and typical knock scenes were clearly recorded with a high speed laser shadowgraph at a speed of 100,000 frames per second. The RCEM is intended to simulate combustion in an automotive engine. Its piston is driven by an electrohydraulic servo system and is allowed to execute continuous reciprocations up to five times. The combustion chamber is a simple pancake type with an ignition plug on its side and the whole inner view is observable through a glass window on the top. Knock observation was made under the following conditions; (1) the fuel was butane, (2) the charged gas was homogeneously pre-mixed and static, (3) the piston executed a single reciprocation. Other parameters were set for heavy knock to occur. The shadowgraph observation revealed that autoignition occurs at a point in the endgas far from a normal flame front and is reflected by the opposite wall.