Low temperature diesel aftertreatment regeneration strategy

An exhaust system for a vehicle having a diesel engine, comprising:

• a diesel oxidizing catalyst (DOC) located immediately downstream of the diesel engine;
• an upstream selective catalytic reduction (SCR) unit located downstream of the DOC;
• a first diesel exhaust fluid (DEF) injector positioned between the DOC and the upstream SCR and adapted to inject DEF into the exhaust gas;
• a diesel particulate filter (DPF) positioned downstream of the upstream SCR and adapted to collect particulate material from exhaust gas passing therethrough;
• and
• an exhaust system controller in communication with an engine controller, a plurality of sensors within the exhaust system and the first DEF injector;
• and
• wherein, the exhaust system controller is adapted to initiate a nitrogen dioxide (NO2) based aftertreatment regeneration of the DPF, wherein the exhaust system controller is adapted to:
• at least partially de-activate the first DEF injector and the upstream SCR, such that NO2 is allowed to pass through the upstream SCR;
• increase, via communication with the engine controller, levels of Nitric Oxide (NO) within exhaust gas from the engine;
• establish and maintaining an target exhaust gas temperature (EGT) at an inlet of the DPF (DPF inlet temperature) and an target EGT at an inlet of the DOC (DOC inlet temperature) by actively controlling, via communication with the engine controller, combustion characteristics of the engine;
• wherein, the DOC is adapted to convert NO within the exhaust gas entering the DOC to NO2, solid carbon-based particulate matter that has accumulated within the DPF is converted to gaseous carbon dioxide (CO2) and NO by using NO2 as an oxidant.

A method of aftertreatment regeneration in a diesel vehicle, comprising:

• routing exhaust gases from a diesel engine through an exhaust system within the vehicle, the exhaust system including:
• a diesel oxidizing catalyst (DOC) located immediately downstream of the diesel engine;
• an upstream selective catalytic reduction (SCR) unit located downstream of the DOC;
• a first diesel exhaust fluid (DEF) injector positioned between the DOC and the upstream SCR and adapted to inject DEF into the exhaust gas;
• a diesel particulate filter (DPF) positioned downstream of the upstream SCR and adapted to collect particulate material from exhaust gas passing therethrough;
• and
• an exhaust system controller in communication with an engine controller, a plurality of sensors within the exhaust system and the first DEF injector;
• and
• initiating a nitrogen dioxide (NO2) based aftertreatment regeneration of the DPF by:
• at least partially de-activating, with the exhaust system controller, the first DEF injector and allowing residual DEF within the upstream SCR to dissipate, such that NO2 is allowed to pass through the upstream SCR;
• selectively adjusting utilization, with the exhaust system controller, via communication with the engine controller, of an exhaust gas recirculation (EGR) unit, injection timing, injection quantity, and fresh air quantity within the engine and increasing levels of Nitric Oxide (NO) within exhaust gas from the engine;
• calculating, an target EGT of exhaust gas coming from the engine and an target EGT of exhaust gas coming from the DOC based on an target exhaust gas temperature (EGT) at an inlet of the DPF (DPF inlet temperature) and thermodynamic characteristics of the exhaust system;
• actively controlling, with the exhaust system controller, via communication with the engine controller, combustion characteristics of the engine by selectively utilizing late injections and post injections within the engine and establishing and maintaining the target EGT of exhaust gas coming from the engine and the target EGT at an inlet of the DOC (DOC inlet temperature) and establishing and maintaining the DPF inlet temperature between approximately three-hundred degrees Celsius and approximately four-hundred degrees Celsius;
• converting, with the DOC, using platinum as a catalyst, NO within the exhaust gas entering the DOC to NO2;
• and
• exposing carbon particulate matter within the DPF to at least one of a platinum catalyst and a palladium catalyst, wherein, the carbon particulate matter and the NO2 react to form gaseous carbon dioxide (CO2) and NO, and further wherein, the NO reacts with oxygen (O2) to form NO2, wherein the newly formed NO2 further reacts with carbon particulate matter;
• monitoring, with the exhaust system controller, via communication with a delta pressure sensor and input from temperature sensors, a level of carbon particulate matter within the DPF;
• and
• initiating a short-term O2 based aftertreatment regeneration of the DPF when one of:
• a level of particulate matter within the DPF increases during the NO2 based aftertreatment regeneration;
• or
• the level of particulate matter within the DPF is decreasing slower than a predetermined rate during the NO2 based aftertreatment regeneration;
• wherein the initiating a short term O2 based aftertreatment regeneration of the DPF further includes:
• managing the level of O2 within exhaust gas at the DPF inlet by controlling, with the exhaust system controller via communication with the engine controller, levels of O2 within exhaust gas from the engine by selectively adjusting utilization, with the exhaust system controller, via communication with the engine controller, of the EGR unit, injection timing, injection quantity, and fresh air quantity within the engine;
• establishing and maintaining a desired EGT of between approximately five-hundred degrees Celsius and six-hundred and fifty degrees Celsius at the inlet of the DPF by:
• calculating, an target EGT of exhaust gas coming from the engine and an target EGT of exhaust gas coming from the DOC based on the desired EGT at the DPF inlet and the thermodynamic characteristics of the exhaust system;
• and
• establishing and maintaining the target EGT of exhaust gas coming from the engine and the target EGT of exhaust gas coming from the DOC by actively controlling, with the exhaust system controller, via communication with the engine controller, combustion characteristics of the engine and selectively utilizing, with the exhaust system controller, via communication with the engine controller, late injections and post injections within the engine;
• and
• converting solid carbon-based particulate matter that has accumulated within the DPF to gaseous CO2 by using O2 as an oxidant;
• and
• selectively initiating a short-term SCR desulfation and desorbing sulfur oxides (SOx) within the upstream SCR, the short-term SCR desulfation including:
• establishing and maintaining an target desorbing EGT at an inlet of the upstream SCR by:
• calculating, an target EGT of exhaust gas coming from the engine and an target EGT of exhaust gas coming from the DOC based on the target desorbing EGT and the thermodynamic characteristics of the exhaust system;
• and
• establishing and maintaining the target EGT of exhaust gas coming from the engine and the target EGT of exhaust gas coming from the DOC by actively controlling, with the controller, via communication with the engine controller, combustion characteristics of the engine and selectively utilizing, with the exhaust system controller, via communication with the engine controller, late injections and post injections within the engine.