Cooling system for diesel exhaust fluid doser

Abstract

A cooling system for a diesel engine. A surge tank defines a first coolant reservoir. A pump is operable when energized to drive a circulating flow of coolant through the diesel engine for cooling the diesel engine. A coolant channel is situated around a diesel exhaust fluid doser in an exhaust system extending from the diesel engine. A second coolant reservoir is positioned to maintain a dedicated gravity-fed coolant supply to the coolant channel situated around the diesel exhaust fluid doser when the pump is not energized. A vent line extends from the second coolant reservoir to the surge tank to allow venting from the coolant channel into the surge tank through the second coolant reservoir without evacuating liquid coolant from the coolant channel.

What is claimed is: 
     
         1 . A cooling system for a diesel engine, the cooling system comprising:
 a surge tank defining a first coolant reservoir;   a pump operable when energized to drive a circulating flow of coolant through the diesel engine for cooling the diesel engine;   a coolant channel situated around a diesel exhaust fluid doser in an exhaust system extending from the diesel engine;   a second coolant reservoir positioned to maintain a dedicated gravity-fed coolant supply to the coolant channel situated around the diesel exhaust fluid doser when the pump is not energized; and   a vent line extending from the second coolant reservoir to the surge tank to allow venting from the coolant channel into the surge tank through the second coolant reservoir without evacuating liquid coolant from the coolant channel.   
     
     
         2 . The cooling system of  claim 1 , further comprising a supply line extending to the coolant channel to supply pumped coolant thereto, and a return line extending from the second coolant reservoir to the pump, wherein the vent line is the path of least resistance among the supply line, the return line, and the vent line for vapor at the coolant channel to reach the surge tank when the pump is off. 
     
     
         3 . The cooling system of  claim 1 , further comprising a first line extending from the coolant channel to the second coolant reservoir to supply pumped coolant thereto, and a second line extending from the second coolant reservoir to the pump, wherein the vent line has an internal diameter smaller than an internal diameter of the first line and smaller than an internal diameter of the second line. 
     
     
         4 . The cooling system of  claim 1 , wherein the diesel exhaust fluid doser is coupled to an inline aftertreatment device including a diesel particulate filter, a diesel oxidation catalyst, and a selective catalytic reduction system, and wherein the diesel exhaust fluid doser is positioned to discharge diesel exhaust fluid within the inline aftertreatment device upstream of the selective catalytic reduction system. 
     
     
         5 . The cooling system of  claim 4 , wherein the diesel particulate filter, the diesel oxidation catalyst, and the selective catalytic reduction system are all integrated into a single common housing. 
     
     
         6 . The cooling system of  claim 1 , wherein the second coolant reservoir is positioned at an elevation above a level of coolant within the surge tank, and wherein a supply line to the coolant channel from the pump, a return line from the second coolant reservoir to the pump, and the vent line all rise to an elevation above a level of coolant within the coolant reservoir. 
     
     
         7 . The cooling system of  claim 1 , wherein the second coolant reservoir is positioned at an elevation above a level of coolant within the surge tank, and wherein a supply line to the coolant channel from the pump includes a check valve that prevents backflow of coolant from the coolant channel into the supply line. 
     
     
         8 . The cooling system of  claim 1 , wherein the second coolant reservoir is positioned at an elevation below a level of coolant within the surge tank. 
     
     
         9 . The cooling system of  claim 1 , further comprising a reservoir line extending directly between a bottom of the second coolant reservoir and the coolant channel. 
     
     
         10 . The cooling system of  claim 1 , wherein the vent line extends directly from the second coolant reservoir to the surge tank. 
     
     
         11 . The cooling system of  claim 1 , wherein the surge tank includes a pressure relief valve. 
     
     
         12 . A method of operating a cooling system connected to a diesel engine and an exhaust system of the diesel engine, the method comprising:
 energizing a pump in a first mode of operation to circulate coolant through the diesel engine and through a coolant channel situated around a diesel exhaust fluid doser;   discharging coolant from the coolant channel upwardly into a coolant reservoir in the first mode of operation;   transitioning to a second mode of operation in which the pump is not energized;   directing vaporized coolant from the coolant channel through the coolant reservoir and then through a vent line to a coolant surge tank in the second mode of operation; and   continuously back-filling the coolant channel with a gravity-fed supply of liquid coolant from the coolant reservoir as coolant is vaporized in the second mode of operation.   
     
     
         13 . The method of  claim 12 , wherein the pump is driven by the diesel engine, and transitioning to the second mode of operation includes shutting off the diesel engine. 
     
     
         14 . The method of  claim 12 , further comprising cooling the diesel exhaust fluid doser in the first mode of operation as the diesel exhaust fluid doser injects diesel exhaust fluid into an inline aftertreatment device of the exhaust system including a diesel particulate filter, a diesel oxidation catalyst, and a selective catalytic reduction system. 
     
     
         15 . The method of  claim 14 , wherein the diesel exhaust fluid doser injects diesel exhaust fluid into a single common housing containing the diesel particulate filter, the diesel oxidation catalyst, and the selective catalytic reduction system. 
     
     
         16 . The method of  claim 12 , wherein the vaporized coolant is directed with an upward elevation from the coolant reservoir to the coolant surge tank through the vent line in the second mode of operation. 
     
     
         17 . The method of  claim 12 , wherein the vaporized coolant is directed with a downward elevation from the coolant reservoir to the coolant surge tank through the vent line in the second mode of operation, the method further comprising closing a valve in the second mode of operation to block backflow of coolant from the coolant channel into a supply line provided to direct coolant into the coolant channel from the pump. 
     
     
         18 . The method of  claim 12 , wherein the vaporized coolant is directed with a downward elevation from the coolant reservoir to the coolant surge tank through the vent line in the second mode of operation, the method further comprising blocking the outflow of coolant from the coolant reservoir by directing each of the following to an elevation above a coolant level in the coolant reservoir: a supply line provided to direct coolant into the coolant channel from the pump, a return line from the second coolant reservoir to the pump, and the vent line. 
     
     
         19 . The method of  claim 12 , further comprising opening a relief valve in the surge tank in response to pressure exceeding a threshold value.