A gas sensor control apparatus (300) including a control section (61) which executes a first receiving process (STEP 1) for receiving a first detection result output from a mixed-potential-type ammonia detection section (42) for detecting ammonia contained in a gas under measurement and corresponding to the concentration of ammonia, a second receiving process (STEP 1) for receiving a second detection result output from an oxygen detection section (2) for detecting oxygen contained in the gas under measurement and corresponding to the concentration of oxygen, a first concentration calculation process (STEP 3) for calculating a first ammonia concentration of the gas under measurement based on the first detection result and the second detection result, and a pressure correction process (STEP 6) for correcting the first ammonia concentration based on pressure information obtained from an external device (220), thereby obtaining a second ammonia concentration of the gas under measurement.

A gas sensor system is equipped with a first gas detection unit, and a second gas detection unit. The first and second gas detection units include a gas introduction port for introducing a gas to be measured, a measurement chamber communicating with the gas introduction port, a conversion medium (NH.sub.3 oxidation catalyst) arranged between the gas introduction port and the measurement chamber, and which converts a portion of a first gas type into a second gas type, and a detection device that detects the second gas type. A ratio of diffusion resistances of the first gas detection unit and the second gas detection unit is greater than or equal to 0.71 and less than or equal to 1.4.

Methods are provided for emissions control of a vehicle. In one example, a method for an engine may include, responsive to a plurality of diagnostic entry conditions being met, indicating degradation of a hydrocarbon trap based on an NH.sub.3 amount in an exhaust gas. In some examples, the NH.sub.3 amount may be determined based on one or more NO.sub.x sensor outputs. In some examples, the plurality of diagnostic entry conditions may include the engine having been in operation over an initial duration immediately following an engine cold start. Conditions of the exhaust gas following the engine cold start may be opportunistically utilized in determining the NH.sub.3 amount from the one or more NO.sub.x sensor outputs. In some examples, the exhaust gas may be actively provided at a predetermined air-fuel ratio to meet at least one of the plurality of diagnostic entry conditions.

A method for controlling an SCR catalytic converter (20, 30), comprising detecting (200) concentration values (314, 324; 414, 424) in the exhaust gas downstream of the catalytic converter (20), wherein at least one concentration value for NH.sub.3 and one concentration value for NO.sub.x is detected; calculating (202) modeled concentration values (316, 322; 416, 422) for NH.sub.3 and NO.sub.x downstream of the catalytic converter on the basis of a catalytic converter model, wherein the model comprises an aging parameter (342, 442) which at least partially describes aging of the modeled catalytic converter; comparing (208) the detected concentration values with the modeled concentration values; and, in a manner dependent on the result of the comparison, changing the aging parameter (342, 442) of the model and/or changing a predefined dosing quantity for a reducing agent in the SCR catalytic converter.

A gas concentration detection device has a first element part, a first detection part, a second element part, a second detection part and a sensitivity correction part. The sensitivity correction part is configured to correct a second gas component concentration detected by the second detection part based on a time difference between a first response time of the first detection part and a second response time of the second detection part when the first detection part and the second detection part have a function of detecting a common gas component contained in a target gas to be detected, and a variation in concentration of the common gas component exceeds a reference variation amount.

Disclosed is a method for selective catalytic reduction operating by desorbing ammonia from at least one storage cartridge in an exhaust line at the output of a motor vehicle engine, the cartridge being arranged in at least one bypass branch of a main line of the exhaust line. The exhaust gas flow rate in the bypass branch is controlled according to an estimated or measured temperature in the bypass branch and a desired amount of ammonia to be injected by desorption estimated in the exhaust line to provide a catalytic reduction of the nitrogen oxides present in the exhaust gas, a temperature of the cartridge being estimated according to the gas flow rate at the temperature estimated or measured during a given time interval and corresponding to an amount of desorbed ammonia equal to the desired amount of ammonia.

Various embodiments include a method for operating an internal combustion engine with a three-way catalytic converter with lambda control, comprising: monitoring a NO.sub.x sensor for a lambda value downstream of the converter; setting a threshold value determining a lambda setpoint value upstream of the converter using the difference between the setpoint value of the electrical signal and the measured electrical signal if the signal is below the threshold; if above the threshold value, determining the lambda setpoint value upstream of the converter using the difference between a NH.sub.3 setpoint value of the NO.sub.x sensor and the measured NH.sub.3 signal of the NO.sub.x sensor; and if the measured NH.sub.3 concentration is higher than the NH.sub.3 setpoint value, increasing the lambda setpoint value upstream of the converter and, if the measured NH.sub.3 concentration is lower than the NH.sub.3 setpoint value, reducing the lambda setpoint value upstream of the converter.

A method for monitoring a concentration of a corrosive gas including at least observing at least one gas fuse, the gas fuse having at least one metal wire, which is configured for breaking due to corrosion if exposed to the corrosive gas in a way that a time-integrated concentration of the corrosive gas exceeds a critical value.

A diesel-electric locomotive includes a diesel emissions reduction unit, including an inlet configured to receive an exhaust stream of a high-speed diesel engine; means for trapping at least a portion of diesel particulate matter contained in the exhaust stream; an aqueous NH.sub.3 dosing system including a dosing controller in communication with an electronic locomotive controller and a nitrogen oxide (“NO.sub.x”) concentration sensor and an ammonia (“NH.sub.3”) concentration sensor, at least one oxidation catalyst panel arranged to isolate the NO.sub.x concentration sensor from NH.sub.3 in the exhaust stream; mixing elements located between the dosing system and the NO.sub.x and NH.sub.3 concentration sensors to mix metered aqueous NH.sub.3 in the exhaust stream; a selective catalyst reactor bed located between the mixing elements and the NO.sub.x and NH.sub.3 concentration sensors; and an exhaust heating system in communication with at least one of the dosing and electronic locomotive controllers.

A selective catalytic reduction system control system (10) and method of its use include an ammonia (“NH.sub.3”) slip sensor (13) located within an interior space (27) of an exhaust stack (15) of a selective catalytic reactor (31), toward an inlet end (25) of the stack (15); a housing (17) located within the interior space of the exhaust stack; the housing including face panels 19; a nitrogen oxides (“NOx”) sensor (11) contained within an interior space (29) defined by the face panels of the housing, at least two of the face panels (19.sub.I, 19.sub.O) containing an oxidation catalyst; and a dosing controller (59) in communication with the NH.sub.3 and NOx sensors, the dosing controller including a microprocessor with dosing logic embedded thereon. The housing with oxidation catalyst acts as a linear box, isolating the NOx sensor from NH.sub.3 slip, linearizing the NOx sensor signal.