Diesel eission fluid quality detection system and method

Abstract

An exhaust treatment system is provided including: a selective catalyst reduction (SCR) unit; a reducing agent dispensing unit configured to introduce a reducing agent into the exhaust; a first NO X sensor upstream of the SCR unit; a second NO X sensor at a location downstream of the SCR unit; a first temperature sensor at a location upstream of where the reducing agent is introduced into the exhaust; a second temperature sensor at a location downstream of where the reducing agent is introduced into the exhaust and upstream of the SCR unit; and a controller configured to determine a reductant quality indicator according to a NO X differential between the first NO X sensor and the second NO X sensor relative to a predicted NO X differential and a temperature differential between the first temperature sensor and the second temperature sensor relative to a predicted temperature differential.

What is claimed is: 
     
         1 . An exhaust treatment system for treating a flow of exhaust produced by an engine comprising:
 a selective catalyst reduction (SCR) unit;   a reducing agent dispensing unit configured to introduce a reducing agent into the exhaust;   a first NO X  sensor configured to indicate a NO X  emission level of the exhaust at a location upstream of the SCR unit;   a second NO X  sensor configured to indicate a NO X  emission level of the exhaust at a location downstream of the SCR unit;   a first temperature sensor configured to indicate a temperature of the exhaust at a location upstream of where the reducing agent is introduced into the exhaust;   a second temperature sensor configured to indicate a temperature of the exhaust at a location downstream of where the reducing agent is introduced into the exhaust and upstream of the SCR unit; and   a controller configured to electronically communicate with the first NO X  sensor, the second NO X  sensor, the first temperature sensor, and the second temperature sensor, and to determine a reductant quality indicator according to a NO X  differential between the first NO X  sensor and the second NO X  sensor relative to a predicted NO X  differential and a temperature differential between the first temperature sensor and the second temperature sensor relative to a predicted temperature differential.   
     
     
         2 . The exhaust treatment system of  claim 1 , further comprising a filter, and wherein the first NO X  sensor is configured to indicate a NO X  level of the exhaust downstream of the filter. 
     
     
         3 . The exhaust treatment system of  claim 2 , wherein the filter is a diesel particulate filter (DPF). 
     
     
         4 . The exhaust treatment system of  claim 2 , further comprising generating a signal when the reductant quality indicator is not within a tolerance level. 
     
     
         5 . The exhaust treatment system of  claim 2 , wherein the reducing agent is urea. 
     
     
         6 . The exhaust treatment system of  claim 5 , wherein the controller is configured to generate a first signal indicating that the reducing agent has a low urea concentration when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is approximately equal to the predicted temperature differential. 
     
     
         7 . The exhaust treatment system of  claim 5 , wherein the controller is configured to generate a second signal indicating a likelihood of a clogged injector when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is lower than the predicted temperature differential. 
     
     
         8 . The exhaust treatment system of  claim 5 , wherein the controller is configured to generate a third signal indicating a likelihood of an injection failure when the NO X  differential is approximately zero and the temperature differential is approximately zero. 
     
     
         9 . The exhaust treatment system of  claim 5 , wherein the controller is configured to generate a fourth signal indicating that the reducing agent is likely diesel when the NO X  differential is moderately lower than the predicted NO X  differential and the temperature differential is higher than the predicted temperature differential. 
     
     
         10 . The exhaust treatment system of  claim 5 , wherein the controller is configured to:
 generate a first signal indicating that the reducing agent has a low urea concentration when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is approximately equal to the predicted temperature differential;   generate a second signal indicating likely clogged injector when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is lower than the predicted temperature differential;   generate a third signal indicating likely injection failure when the NO X  differential is approximately zero and the temperature differential is approximately zero; and   generate a fourth signal indicating that the reducing agent is likely diesel when the NO X  differential is moderately lower than the predicted NO X  differential and the temperature differential is higher than the predicted temperature differential.   
     
     
         11 . A method for detecting a reducing agent quality comprising:
 obtaining a first NO X  value indicating a NO X  level for an engine exhaust upstream of a selective catalyst reduction (SCR) unit;   obtaining a second NO X  value indicating a NO X  emission level for the engine exhaust downstream of the SCR unit;   obtaining a first temperature value indicating a temperature for the engine exhaust upstream of an introduction of a reducing agent;   obtaining a second temperature value indicating a temperature for the engine exhaust downstream of the introduction of the reducing agent and upstream of the SCR unit; and   computing a reductant quality indicator according to a NO X  differential between the first NO X  value and the second NO X  value relative to a predicted NO X  differential and a temperature differential between the first temperature value and the second temperature value relative to a predicted temperature differential.   
     
     
         12 . The method of  claim 11 , wherein the first NO X  value further indicates a NO X  level for the engine exhaust after treatment by a filter. 
     
     
         13 . The method of  claim 11 , further comprising generating a signal when the reductant quality indicator indicated is not within a tolerance level. 
     
     
         14 . The method of  claim 11 , further comprising adjusting a rate at which the reducing agent is injected into the exhaust according to the reductant quality indicator. 
     
     
         15 . The method of  claim 11 , wherein the reducing agent is urea. 
     
     
         16 . The method of  claim 15 , further comprising generating a first signal indicating that the reducing agent has a low urea concentration when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is approximately equal to the predicted temperature differential. 
     
     
         17 . The method of  claim 15 , further comprising generating a second signal indicating likely clogged injector when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is lower than the predicted temperature differential. 
     
     
         18 . The method of  claim 15 , further comprising generating a third signal indicating likely injection failure when the NO X  differential is approximately zero and the temperature differential is approximately zero. 
     
     
         19 . The method of  claim 15 , further comprising generating a fourth signal indicating that the reducing agent is likely diesel when the NO X  differential is moderately lower than the predicted NO X  differential and the temperature differential is higher than the predicted temperature differential. 
     
     
         20 . The method of  claim 15 , further comprising:
 generating a first signal indicating that the reducing agent has a low urea concentration when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is approximately equal to the predicted temperature differential;   generating a second signal indicating likely clogged injector when the NO X  differential is lower than the predicted NO X  differential and the temperature differential is lower than the predicted temperature differential;   generating a third signal indicating likely injection failure when the NO X  differential is approximately zero and the temperature differential is approximately zero; and   generating a fourth signal indicating that the reducing agent is likely diesel when the NO X  differential is moderately lower than the predicted NO X  differential and the temperature differential is higher than the predicted temperature differential.