An exhaust purification system comprising an exhaust purification catalyst, a downstream side air-fuel ratio sensor, and a control device performing air-fuel ratio control for controlling an air-fuel ratio of exhaust gas and abnormality diagnosis control for diagnosing the downstream side air-fuel ratio sensor. In the air-fuel ratio control, the control device alternately and repeatedly switches the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst between a rich air-fuel ratio and a lean air-fuel ratio. In the abnormality diagnosis control, the control device judges that the downstream side air-fuel ratio sensor has become abnormal when the air-fuel ratio of the exhaust gas is made the rich air-fuel ratio by the air-fuel control and the output air-fuel ratio of the downstream side air-fuel ratio sensor changes from an air-fuel ratio richer than a predetermined lean judged air-fuel ratio to an lean air-fuel ratio.

When a catalyst temperature of a catalyst device is at or below a lower limit air-fuel ratio richness control is prohibited. When a first timing, where an estimated value of a NOx storage amount has reached an enrichment start threshold value, and a second timing, based on a set interval time in an enrichment interval time map, are both satisfied, the control is started. The second timing is corrected by multiplying the set interval time by an enrichment interval correction coefficient preset based on the catalyst temperature and a storage ratio of the estimated value of the NOx storage amount to an enrichment start threshold value of the NOx storage amount. The frequency of the air-fuel ratio richness control of a catalyst device configured to recover a purification capacity of a catalyst is reduced, and the catalyst temperature is raised while preventing white smoke development and hydrocarbon slip, to thereby achieve improvement in exhaust gas composition and improvement in fuel efficiency.

A method of maintaining a temperature of an aftertreatment system of a vehicle, the method including: operating, by a controller, a retarder reducing driving force of a propeller shaft of the vehicle in response to a retarder operation request signal; operating, by the controller, a jake brake device which discharges a fuel-air mixture compressed in an explosion stroke of the engine to an exhaust pipe and decreases revolutions per minute (RPM) of the engine or an exhaust brake device which blocks a discharge of the exhaust gas of the engine to a rear end of the exhaust pipe and decreases the RPM of the engine, in order to remove the output error value; and controlling, by the controller, the engine so that an amount of exhaust gas introduced into the aftertreatment system is decreased.

A fault diagnosis device for an exhaust pipe fuel injector that diagnoses a normality or an abnormality of the exhaust pipe fuel injector which injects a fuel according to an instructed fuel injection amount, includes: a storage unit which stores a regeneration duration and an instructed fuel injection amount in the regeneration duration; a calculation unit which calculates an instructed fuel injection amount per unit time in the regeneration duration; and a fault diagnosis unit which diagnoses that the exhaust pipe fuel injector is abnormal when the instructed fuel injection amount per unit time in the regeneration duration exceeds a fault threshold, and diagnoses that the exhaust pipe fuel injector is normal when the instructed fuel injection amount per unit time in the regeneration duration does not exceed the fault threshold.

A fluid atomizer is provided, and the fluid atomizer is used to atomize the fluid into a spray of droplets, and transform the fluid into spray dispersion in the form of intertwined inner conical film and outer conical film layer by atomizing the fluid. The fluid atomizer includes a plurality of inlet channels, at least one swirl chamber, at least one contracting channel, at least one flow passage channel, at least one internal outlet channel, at least one external outlet channel, and at least one channel holder.

An exhaust gas aftertreatment system for an internal combustion engine, which comprises an exhaust system which can be connected to the outlet of an internal combustion engine. A catalytic converter close to the engine and a second catalytic converter arranged downstream of the catalytic converter in an underbody of a motor vehicle are provided in the flow direction of an exhaust gas from the internal combustion engine flowing through an exhaust gas duct of the exhaust system. An inlet point for secondary air, an exhaust gas burner, and a fuel injector for introducing fuel into the exhaust gas duct are arranged downstream of the catalytic converter close to the engine and upstream of the second catalytic converter. According to the invention, the exhaust gas burner is activated immediately after the internal combustion engine is started in order to heat the second catalytic converter to its light-off temperature. Once the second catalytic converter has reached its light-off temperature, secondary air and fuel are additionally introduced into the exhaust gas duct and are exothermically reacted on the second catalytic converter in order to support the heating of the second catalytic converter.

Methods and systems for improving operation of an engine at higher speeds and loads are disclosed. In one example, fuel may be injected to an exhaust system of the engine so that temperatures of exhaust system components may be reduced when the engine is operated at higher speeds and loads.

The present subject matter relates to a method and a treatment system monitor for monitoring an engine exhaust after-treatment system containing more than one Lean NO.sub.x Traps (LNT). The method includes receiving an exhaust gas of a desired air-fuel ratio upstream of a respective LNT. The LNT is further regenerated using a richer than stoichiometric exhaust air-fuel ratio and subsequently an air-fuel ratio received downstream of the LNT is evaluated. Further, a working state of a respective LNT is determined based on the monitoring of the air-fuel ratio and oxygen level upstream and downstream of the LNT.

The present invention provide a method for purifying exhaust gas in which nitrogen oxides (NOx) gas is removed from a combustion exhaust gas. The method for purifying exhaust gas according to the invention is characterized in that water vapor is further added to raw exhaust gas to be processed to increase the water vapor concentration in the exhaust gas and the resulting moisture-adjusted exhaust gas is introduced into a denitration catalyst layer. The water vapor concentration in the moisture-adjusted exhaust gas is preferably 22.0% by volume or less in the total of the water vapor originally contained in the raw exhaust gas and the added water vapor.

When the NSR temperature Tnsr is in a warming-up temperature range equal to or higher than the activation start temperature of the NSR catalyst and lower than the activation completion temperature of the NSR catalyst, a control apparatus according to the present invention controls the quantity of fuel supplied to the NSR catalyst by a fuel supply device such that the air-fuel ratio of the exhaust gas flowing into the NSR catalyst while the rich spike process is performed is lower when the NSR temperature Tnsr is lower than a specific temperature Tthr than when the NSR temperature Tnsr is equal to or higher than the specific temperature Tthr.