A fault detection method for a selective catalytic reduction (SCR) system comprising an SCR reactor, includes receiving a plurality of operating parameters (702) of the SCR reactor from a plurality of sensors. The method also includes estimating a state of an adaptive reactor model (704) representative of the SCR reactor based on the plurality of operating parameters. The method also includes generating a feature parameter (706) based on the plurality of operating parameters and the estimated state of the adaptive reactor model. The method includes determining a fault in the SCR system (708) based on the feature parameter.

A method of emission control includes receiving a slip set-point and a residual set-point corresponding to a reductant from a selective catalyst reduction (SCR) reactor. The method further includes receiving a plurality of inlet parameters of the SCR reactor and a slip value corresponding to the reductant from outlet of the SCR reactor. The method also includes generating a feedback signal value and a feedforward signal using a gain scheduling approach. The feedback signal is determined based on the slip set-point and the slip value. The feedforward signal value is determined based on a residual value of the reductant and the plurality of inlet parameters using a time-varying kinetic model. The method further includes determining a flow set-point corresponding to the reductant based on the feedback signal value and the feedforward signal value and regulating injection of the reductant into the SCR reactor based on the flow set-point.

A method for calculating exhaust gas temperature indirectly at points in or around an engine exhaust after treatment system for use in determining an amount of unburned hydrocarbons resident therein at a given point in time.

An exhaust gas purifying apparatus for an internal combustion engine, in which a NOx absorbing catalyst and a NOx concentration sensor for detecting a NOx concentration in exhaust gases of the engine, are provided in an exhaust passage of the engine. A rich spike for temporarily enriching the air-fuel ratio is performed, and an execution timing of the rich spike is determined based on a detected output from the NOx concentration sensor. Performing the rich spike is determined to be unnecessary during a reducing state period from the time the rich spike ends to the time a preset time period has elapsed, and is also determined to be unnecessary when a change tendency of the detected output is determined to be an output decreasing state where the detected output is decreasing. The execution timing of the rich spike is determined using the detected output when the change tendency is determined to be an output staying/increasing state where the detected output is staying at a constant value or increasing after the end timing of the reducing state period.

A system includes a filtering module that filters a first signal that indicates an amount of nitrogen oxides (NOx) in exhaust gas upstream from a catalyst, and that filters a second signal that indicates amounts of NOx and ammonia (NH3) in exhaust gas downstream from the catalyst. A slip determination module determines whether NH3 is present in exhaust gas downstream from the catalyst based on a frequency response of the first and second signals.

The present disclosure concerns a method for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined. In order to improve the monitoring of such a catalytic converter regardless of the respective type of catalytic converter used, it is proposed with the present disclosure that an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to the presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow.

A method for evaluating a sensor signal of an exhaust NOx sensor, which is disposed downstream of a three-way catalytic converter in an exhaust system of a spark ignition internal combustion engine. An ammonia factor is modeled downstream of the three-way catalytic converter using an ammonia formation model. A NOx emission is modeled in the exhaust system downstream of the three-way catalytic converter using a NOx model. The modeled ammonia emissions and the modeled NOx emission are separated by a separation algorithm using the sensor signal of the exhaust NOx sensor. The separation algorithm provides quantitative information about the tailpipe ammonia emissions and the tailpipe NOx emissions of the spark ignition internal combustion engine. An engine control unit and an internal combustion engine for carrying out such a method are also provided.

A method to control combustion inside the combustion chamber of a burner of an exhaust gas after-treatment system is described. The method provides for placing a first pressure sensor along a first duct of the exhaust gas after-treatment system; acquiring the signal detected by said first pressure sensor, processing the signal detected by the first pressure sensor determining the energy content thereof; calculating a combustion index; and recognising a failed combustion event inside the combustion chamber in case the combustion index is smaller than a threshold value.

Embodiments described herein methods can be used in particulate filter regeneration, such as particulate filters used for filtering the exhaust of an engine, e.g., a diesel engine. Systems herein can be configured to dispense combustion gas(es) into housing were a particulate filter is contained and to ignite the combustion gases. Methods for conducting a safety verification process of such systems are disclosed, as well as methods for regenerating the filters. Still other embodiments are described.