Virtual reductant quality sensor

Abstract

An exhaust treatment system is provided. The exhaust treatment system may include a selective catalyst reduction (SCR) unit for removing NO X from exhaust; a reducing agent dispensing unit for providing a reducing agent to the SCR unit; a first NO X sensor for indicating a NO X emission level of the exhaust prior to the SCR unit; a second NO X sensor for indicating a NO X emission level of the exhaust after the SCR unit, wherein at least one of the first NO X sensor and the second NO X sensor is a virtual NO X sensor; and a controller configured to electronically communicate with a virtual sensor network comprising a first virtual NO X sensor and a virtual reducing agent quality sensor indicating a quality index of the reducing agent according to the first NO X sensor and the second NO X sensor.

1 . An exhaust treatment system comprising:
 a selective catalyst reduction (SCR) unit for removing NO X  from exhaust produced by an engine;   a reducing agent dispensing unit for providing a reducing agent to the SCR unit;   a first NO X  sensor for indicating a NO X  emission level of the exhaust prior to the SCR unit;   a second NO X  sensor for indicating a NO X  emission level of the exhaust after the SCR unit, wherein at least one of the first NO X  sensor and the second NO X  sensor is a virtual NO X  sensor; and   a controller configured to electronically communicate with a virtual sensor network comprising a first virtual NO X  sensor and a virtual reducing agent quality sensor, the virtual reducing agent quality sensor for indicating a quality index of the reducing agent, and wherein the quality index of the reducing agent is determined according to the first NO X  sensor and the second NO X  sensor.   
     
     
         2 . The exhaust treatment system of  claim 1 , wherein the virtual sensor network further comprises an exhaust flow rate sensor for detecting a flow rate of the exhaust through the SCR unit, and a reductant flow rate sensor for detecting the flow rate of the reductant to the SCR unit. 
     
     
         3 . The exhaust treatment system of  claim 1 , wherein the reducing agent is urea. 
     
     
         4 . The exhaust treatment system of  claim 1 , further comprising an exhaust filter coupled between the engine and the SCR unit. 
     
     
         5 . The exhaust treatment system of  claim 4 , wherein the exhaust filter is a diesel particulate filter (DPF). 
     
     
         6 . The exhaust treatment system of  claim 5 , wherein the first NO X  sensor is for further indicating a NO X  emission level between the DPF and the SCR unit. 
     
     
         7 . The exhaust treatment system of  claim 1 , wherein the first NO X  sensor is the first virtual NO X  sensor. 
     
     
         8 . The exhaust treatment system of  claim 1 , wherein the second NO X  sensor is the first virtual NO X  sensor. 
     
     
         9 . The exhaust treatment system of  claim 1 , wherein the first NO X  sensor is the first virtual NO X  sensor and the second NO X  sensor is a second virtual NO X  sensor. 
     
     
         10 . The exhaust treatment system of  claim 1 , wherein the controller is further configured to generate a signal when the quality index of the reducing agent indicated by the virtual reducing agent quality sensor is not within a tolerance level. 
     
     
         11 . The exhaust treatment system of  claim 10 , wherein reducing agent dispensing unit is configured to increase or decrease a flow rate of the reductant according to the signal. 
     
     
         12 . A method for detecting a reducing agent quality comprising:
 configuring a virtual sensor network comprising at least a first virtual NO X  sensor for indicating a first NO X  emission level and a virtual reductant quality sensor for indicating a reductant quality index for a reductant received by a selective catalyst reduction (SCR) unit;   obtaining a first NO X  value according to a first NO X  sensor indicating a NO X  emission level for engine exhaust prior to treatment by the SCR unit;   obtaining a second NO X  value according to a second NO X  sensor indicating a NO X  emission level for engine exhaust after treatment by the SCR unit; and   computing the reductant quality index according to the first NO X  value and the second NO X  value,   wherein at least one of the first NO X  sensor and the second NO X  sensor is the first virtual NO X  sensor.   
     
     
         13 . The method of  claim 12 , wherein the reductant is urea. 
     
     
         14 . The method of  claim 12 , wherein the first NO X  sensor further indicates a NO X  emission level for the engine exhaust after treatment by an engine filter. 
     
     
         15 . The method of  claim 14 , wherein the engine filter is a diesel particulate filter (DPF). 
     
     
         16 . The method of  claim 12 , wherein the first NO X  sensor is the first virtual NO X  sensor. 
     
     
         17 . The method of  claim 12 , wherein the second NO X  sensor is the first virtual NO X  sensor. 
     
     
         18 . The method of  claim 12 , wherein the first NO X  sensor is the first virtual NO X  sensor and the second NO X  sensor is a second virtual NO X  sensor. 
     
     
         19 . The method of  claim 12 , further comprising generating a signal when the reductant quality index indicated by the virtual reductant quality sensor is not within a tolerance level. 
     
     
         20 . The method of  claim 19 , further comprising adjusting a flow rate of the reductant according to the signal.