Reintroduction of Air in Delivery System Accumulator

Abstract

According to one embodiment, an apparatus for reintroducing air includes a bypass valve that reduces pressure in an accumulator that stores reductant to less than an air supply pressure of an air supply. The apparatus also includes a metering valve that fills the accumulator with air from the air supply at the air supply pressure, and a pump that pumps reductant into the accumulator.

1 . An apparatus for reintroducing air, comprising:
 a bypass valve downstream of an accumulator for reducing pressure in the accumulator storing reductant to less than an air supply pressure of an air supply;   a metering valve filling the accumulator with air from the air supply at the air supply pressure; and   a pump pumping reductant into the accumulator.   
     
     
         2 . The apparatus of  claim 1 , wherein the bypass valve reduces pressure in the accumulator to less than the air supply pressure of the air supply in response to a timer exceeding a predetermined threshold. 
     
     
         3 . The apparatus of  claim 2 , wherein the predetermined threshold comprises an upper pressure threshold and a lower pressure threshold, and the timer increments when the pressure in the accumulator is more than the upper pressure threshold or the pressure in the accumulator is less than the lower pressure threshold. 
     
     
         4 . The apparatus of  claim 3 , wherein the upper pressure threshold is associated with a first predetermined percentage of a target pressure greater than the target pressure, and the lower pressure threshold is associated with a second predetermined percentage of a target pressure lower than the target pressure. 
     
     
         5 . The apparatus of  claim 4 , wherein the first and second predetermined percentages are between about 10% and about 30%. 
     
     
         6 . The apparatus of  claim 1 , wherein the bypass valve reduces pressure in the accumulator to less than the air supply pressure of the air supply in response to an expiration of a priming time interval. 
     
     
         7 . The apparatus of  claim 6 , wherein the priming time interval is between about 4 hours and about 16 hours. 
     
     
         8 . The apparatus of  claim 1 , wherein the bypass valve reduces pressure in the accumulator by opening to allow reductant in the accumulator to drain from the accumulator. 
     
     
         9 . The apparatus of  claim 8 , wherein the metering valve closes to prevent filling the accumulator with air from the air supply while the bypass valve is opened. 
     
     
         10 . The apparatus of  claim 9 , wherein the pump stops pumping reductant into the accumulator while the bypass valve is open and when the metering valve is filling the accumulator with air. 
     
     
         11 . An internal combustion engine system, comprising:
 an internal combustion engine;   an exhaust after-treatment system treating exhaust gas from the internal combustion engine;   a reductant delivery system providing reductant to the exhaust after-treatment system and comprising:
 a reductant source; 
 an accumulator storing reductant; 
 a bypass valve downstream of the accumulator and upstream of the reductant source, the bypass valve operable to reduce pressure in the accumulator to less than an air supply pressure of an air supply downstream of the bypass valve; 
 a metering valve downstream of the accumulator and the bypass valve and upstream of the air supply, the metering valve being operable to fill the accumulator with air from the air supply at the air supply pressure; and 
 a pump downstream of the reductant source and upstream of the accumulator, the pump being operable to pump reductant from the reductant source into the accumulator. 
   
     
     
         12 . The internal combustion engine system of  claim 11 , further comprising a controller monitoring a pressure within the accumulator, and stopping the pump, closing the metering valve, and opening the bypass valve when a magnitude of pressure oscillations within the accumulator meets a threshold. 
     
     
         13 . The internal combustion engine system of  claim 12 , wherein a timer increments when the pressure in the accumulator is more than an upper pressure threshold or the pressure in the accumulator is less than a lower pressure threshold, and the magnitude of pressure oscillations is determined using the timer. 
     
     
         14 . The internal combustion engine system of  claim 12 , further comprising a reductant nozzle injecting reductant into the exhaust gas from the internal combustion engine. 
     
     
         15 . The internal combustion engine system of  claim 12 , wherein the controller closes the bypass valve and opens the metering valve after reductant has drained from the accumulator through the bypass valve. 
     
     
         16 . The internal combustion engine system of  claim 15 , wherein the controller closes the metering valve and starts the pump when the pressure within the accumulator is equal to or less than the air supply pressure. 
     
     
         17 . A method for reintroducing air, comprising:
 reducing pressure in an accumulator storing reductant to less than an air supply pressure of an air supply via a bypass valve downstream of the accumulator;   filling the accumulator with air at the air supply pressure through a metering valve connecting the accumulator to the air supply; and   pumping reductant into the accumulator from a pump.   
     
     
         18 . The method of  claim 17 , further comprising:
 detecting an air volume in the accumulator;   stopping the pump in response to the detected air volume indicating a low air volume;   closing the metering valve in response to the detected air volume indicating a low air volume; and   opening the bypass valve to drain reductant from the accumulator in response to stopping the pump and closing the metering valve.   
     
     
         19 . The method of  claim 18 , further comprising closing the bypass valve after reductant has been drained from the accumulator. 
     
     
         20 . The method of  claim 19 , further comprising:
 opening the metering valve after reductant has been drained from the accumulator;   supplying air at the air supply pressure to the accumulator through the metering valve after reductant has been drained from the accumulator until the air pressure within accumulator reaches the air supply pressure;   closing the metering valve after the air pressure within the accumulator reaches the air supply pressure; and   pumping reductant into the accumulator from the pump after the accumulator reaches the air supply pressure and the metering valve is closed.