It has now been over 25 years since the introduction of the catalytic converter to reduce emissions from the internal combustion engine. It is considered one of the greatest environmental successes of the 20th century, however, new emission control technologies are still being developed to meet ever more stringent mobile source (gasoline and diesel) emissions. This short review will discuss the basis for improvements and highlight technology area, which will require further improvements in emissions and fuel economy. Some of the issues related to fuel cells which some believe may replace the internal combustion engines for automobile applications is also be briefly discussed.

Automobile exhaust catalysts

A converter containing a NOx absorbing and reducing catalyst is disposed in the exhaust passage of an internal combustion engine. The upstream half portion (portion of the inlet side) of the substrate of the NOx absorbing and reducing catalyst in the converter carries the oxygen storage component that absorbs oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas is lean and releases the absorbed oxygen when the air-fuel ratio of the exhaust gas flowing in is rich in addition to carrying the NOx absorbing and reducing catalyst. After NOx is absorbed by the NOx absorbing and reducing catalyst as a result of operating the engine at a lean air-fuel ratio, the engine is operated at a rich air-fuel ratio, so that NOx is released from the NOx absorbing and reducing catalyst and is purified by reduction. Here, oxygen is released from the oxygen storage component carried by the upstream half portion of the substrate and is reacted with the H 2 and CO components in the exhaust gas, so that the temperature of the NOx absorbing and reducing catalyst is raised within short periods of time due to the heat of reaction. Therefore, the catalyst exhibits increased activity and the NOx absorbing and reducing catalyst exhibits improved NOx purification capability.

Exhaust gas purification device for an internal combustion engine

An air-fuel ratio control system for an internal combustion engine includes a LAF sensor and an O2 sensor arranged in an exhaust pipe at respective locations upstream and downstream of a catalytic converter. A desired air-fuel ratio coefficient used in calculating an amount of fuel supplied to the engine is calculated based on operating conditions of the engine, and corrected based on output from the O2 sensor. The air-fuel ratio of a mixture supplied to the engine is feedback-controlled to a stoichiometric air-fuel ratio based on the corrected desired air-fuel ratio coefficient. When the output from the O2 sensor falls within a predetermined range, the desired air-fuel ratio coefficient is not corrected, but held at an immediately preceding value thereof.

Air-fuel ratio control system for internal combustion engines

An internal combustion engine wherein an HC treatment catalyst (12) having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst (14), an urea aqueous solution fed from the reducing agent feed valve (15) is arranged upstream of the HC treatment catalyst (12), urea, and NOx contained in the exhaust gas, and HC adsorbed on the HC treatment catalyst 12 are reacted with each other to form intermediate products having cyano groups, oximes, and amino groups, and these intermediate products are sent to the NOx selective reducing catalyst (14).

Exhaust purification device of internal combustion engine

An experimental study on premixed-charge compression ignition gasoline engine

A lean NOx reduction catalyst capable of reducing NOx through reaction of H 2 with NOx at low temperatures below 350° C. is installed in a downstream portion of an exhaust pipe of an internal combustion engine in or near a muffler. Such an NOx reduction catalyst comprises, for example, Pt/zeolite catalyst. An H 2 generator is installed so as to supply the H 2 to an inlet side of the NOx reduction catalyst. The H 2 generator may include a reforming catalyst for reforming methanol, LPG, or natural gas to generate H 2 . The generated H 2 flows to the NOx reduction catalyst where it reacts with NOx to purify the exhaust gas.

NOx decreasing apparatus for an internal combustion engine

NOx absorbent (18) is disposed in the exhaust gas path in the internal combustion engine and exhaust gas is adapted to flow constantly through said absorbent (18) during the operation of said engine. NOx absorbent (18) absorbs NOx when an air-fuel ratio of exhaust gas flowing into said absorbent (18) is lean and, when an air-fuel ratio of exhaust gas becomes equal to the theoretical air-fuel ratio or rich, it discharges NOx having been absorbed therein. Over almost the entire range of operation of the engine, lean mixed gas is burnt in the combustion chamber (3) and NOx generated at this time is absorbed by said absorbent (18). An air-fuel ratio of exhaust gas flowing into the NOx absorbent (18) is periodically made equal to the theoretical one or rich and NOx having been absorbed by the absorbent (18) is discharged and reduced at the same time.

Device for purifying exhaust of internal combustion engine

An engine having an intake port which comprises a straight port and a helical-shaped port which are separated by a separating wall. A control valve is arranged in the inlet portion of the straight port and opens when the engine is operating under a heavy load. A projection is formed on the side wall of the separating wall, which defines the straight port and is located downstream of the control valve. A bypass passage connected to the helix terminating portion of the helical portion of the helical-shaped port is formed in the separating wall. The projection has an arc-shaped cross-sectional tip face which is directed towards the upstream of the intake port. The inlet opening of the bypass passage is formed on the tip face of the projection.

An intake device of an internal combustion engine

An exhaust gas cleaning device for an internal combustion engine comprising an NOx absorbing agent (18) disposed in the exhaust passage of the internal combustion engine for absorbing NOx when the air-fuel ratio of exhaust gas flowing thereinto is lean, while it discharges NOx so absorbed when the air-fuel ratio of exhaust gas flowing thereinto becomes a theoretical air-fuel ratio or rich, and an air-fuel ratio sensor (22) disposed downstream of the NOx absorbing agent (18) in the exhaust passage for judging that discharging of NOx from the absorbing agent (18) is completed when the air-fuel ratio detected by the air-fuel ratio sensor (22) has been switched from lean to rich after the air-fuel ratio of exhaust gas flowing into the absorbing agent (18) was switched from lean to rich.

Exhaust gas cleaning device for an internal combustion engine.

A fuel injection valve includes an injector body having a fuel injection hole and an adapter having a fuel collision surface, two air injection holes and two injected fuel paths. The fuel injected from the fuel injection hole flows in a slug-like pattern and collides with the fuel collision surface where the fuel is atomized a first time. Then, the fuel flows in a direction away from an axis of the adapter in a membrane-like pattern getting thinner in thickness to be finally broken to pieces, that is, to be atomized a second time. The air injected from the air injection holes collides with the membrane-like pattern of fuel to be atomized a third time before the fuel goes out of the injected fuel paths.

Kiyoshi Nakanishi

Papers

NOx decreasing apparatus for an internal combustion engine

Device for purifying exhaust of internal combustion engine

An intake device of an internal combustion engine

Exhaust gas cleaning device for an internal combustion engine.

Fuel injection valve with an air assist adapter for an internal combustion engine