Abstract: Methods for monitoring and detecting undesired exotherms which may occur in an exhaust aftertreatment system coupled to a lean burning combustion engine are described. In one particular approach, an undesired exotherm may be indicated based on an expected oxygen depletion along a length of an exhaust aftertreatment system in the direction of exhaust gas flow of exhaust gas. For example, during DPF regeneration, a certain amount of oxygen is expected to be utilized for removing soot. If less oxygen is actually found in the exhaust downstream of the exhaust system, then an undesired exotherm may be present, as unintended reductant may be present in the exhaust and reacting exothermically with oxygen. Various mitigation actions may then be initiated in response to the indication of an undesired exotherm.

Abstract: A diesel engine exhaust gas aftertreatment system is described. The system may comprise a heat transfer device comprising a first side and a second side; a heater downstream of the first side of the heat transfer device, a filter downstream of the heater; and, an exhaust path downstream of the filter leading to the second side of the heat transfer device, wherein the exhaust path is isolated from an external surface of the filter to inhibit heat transfer from the heated exhaust gas exiting the filter to the external surface of the filter.

Abstract: A three-state switch includes a first input terminal, a first output terminal, a second output terminal, a pole, a first throw, a second throw, and a third throw. The first input terminal is for receiving a first signal. The first output terminal is coupled to the first input terminal, and for outputting a second signal. The second output terminal is for outputting a third signal. The first throw is for contacting with the pole to have the three-state switch output the second signal, and not output the third signal. The second throw is for contacting with the pole to have the three-state switch not output the second signal and the third signal. The third throw is for contacting with the pole to have the three-state switch output the second signal and the third signal. When the pole is suspended, the first output terminal outputs the second signal.