Selective catalytic reduction catalyst pre-heating burner assembly and method of controlling burner emissions

An exhaust system for a vehicle, comprising:

• an exhaust pipe section defining a main exhaust passageway therein;
• a selective catalytic reduction (SCR) catalyst arranged in fluid communication with and positioned downstream of the exhaust pipe section;
• a burner assembly positioned in a side branch connected to the exhaust pipe section, the burner assembly including a burner with a combustion chamber disposed therein, an igniter for initiating fuel combustion in the combustion chamber, and a connecting tube extending between an outlet of the combustion chamber and the exhaust pipe section, the connecting tube including a connecting tube passageway having an inlet that is arranged in fluid communication with the combustion chamber of the burner and an outlet in fluid communication with the main exhaust passageway in the exhaust pipe section;
• and
• a filter element positioned in the connecting tube passageway that is made of a metallic mesh and has a porosity that permits burner generate exhaust to flow through the filter element while trapping particulate matter generated by the burner.

An exhaust system for a vehicle, comprising:

• an exhaust pipe section defining a main exhaust passageway therein;
• a selective catalytic reduction (SCR) catalyst arranged in fluid communication with and positioned downstream of the exhaust pipe section;
• a burner assembly positioned in a side branch connected to the exhaust pipe section, the burner assembly including a burner with a combustion chamber disposed therein, an igniter for initiating fuel combustion in the combustion chamber, and a connecting tube extending between an outlet of the combustion chamber and the exhaust pipe section, the connecting tube including a connecting tube passageway having an inlet that is arranged in fluid communication with the combustion chamber of the burner and an outlet in fluid communication with the main exhaust passageway in the exhaust pipe section;
• and
• a filter element positioned in the connecting tube passageway that is made of a metallic mesh and has a porosity that permits burner generate exhaust to flow through the filter element while trapping particulate matter generated by the burner,
• wherein a catalytic washcoat at least partially coats the metallic mesh of the filter element, the catalytic washcoat comprising a mixture of a support material and a catalyst material made of one or more platinum group metals (PGM) that chemically react with emissions generated by the burner.

A method for pre-heating an exhaust system of a vehicle, the method comprising the steps of:

• injecting fuel into a combustion chamber of a burner assembly positioned in the exhaust system upstream of a selective catalytic reduction (SCR) catalyst at a first fuel injection rate;
• supplying air to the combustion chamber of the burner assembly at a first flowrate that, together with the first fuel injection rate, defines a first air/fuel ratio within the combustion chamber;
• igniting an air/fuel mixture within the combustion chamber of the burner assembly resulting in the generation of heat and emissions within the combustion chamber;
• maintaining the first air/fuel ratio for a pre-determined start-up period;
• starting an engine of the vehicle a period of time after the ignition of the air/fuel mixture within the combustion chamber of the burner assembly;
• and
• routing the heat and emissions generated in the combustion chamber through a connecting tube that includes a catalytic washcoat and leads to an exhaust pipe section that is positioned upstream of the selective catalytic reduction (SCR) catalyst,
• wherein the catalytic washcoat in the connecting tube initiates a chemical reaction with the emissions passing through the connecting tube to reduce nitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbon (HC) concentrations in the emissions generated by the burner assembly during the pre-determined start-up period.