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Method for determining the true amount of an active product entering a catalytic device of an exhaust line of a vehicle

  • US 10,449,494 B2
  • Filed: 04/14/2014
  • Issued: 10/22/2019
  • Est. Priority Date: 04/12/2013
  • Status: Active Grant
First Claim
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1. A method for determining a true flow rate of a reducing agent in the form of gaseous ammonia or a product which is a source of gaseous ammonia entering an exhaust stream of an exhaust line in a catalytic device (1) of an internal combustion engine of a vehicle, in response to an introduction into the exhaust lineof an ordered additional test flow rate (tNH3theotest) of said reducing agent ordered by and controlled by an engine control unit (3) for controlling the catalytic device (1), the catalytic device comprising:

  • at least one inlet (4) for a mixture comprising exhaust gases and said reducing agent, andat least one outlet (5) for the exhaust gases, said reducing agent capable of reacting inside the catalytic device (1) with the exhaust gases with the effect of reducing or eliminating the content of nitrogen oxide in the exhaust gasses and originating from combustion in the internal combustion engine, at the outlet (5) of the catalytic device (1), the content of said nitrogen oxide being measured in the exhaust gases by means of a measurement probe (8) sensitive to said nitrogen oxide and to said reducing agent and positioned at the outlet of the catalytic device (1), wherein measurement by the probe when both the nitrogen oxide and the reducing agent are present results in a measurement of mixed up content of both the nitrogen oxide and the reducing agent in a manner that does not distinguish the relative amounts of the nitrogen oxide and the reducing agent said method being characterized in that it comprises at least the following steps employed by software implemented by the engine control unit;

    (100) introducing, into the exhaust gas stream upstream of the catalytic device (1), an active flow rate (fNH3base) of said active reducing agent, and measuring the content of said nitrogen oxide and said reducing agent using the measurement probe (8), wherein the introduction of the active flow rate (fNIbbase) of said reducing agent is at a rate such that said nitrogen oxide and said reducing agent are absent at said measurement probe (8) at the outlet of the catalytic device (1),(200) increasing said active flow rate (fNH3base) of the reducing agent, and measuring the content of said reducing agent using the measurement probe (8), wherein the increasing proceeds until said probe (8) measures a given escape content (CNH3escape) of said reducing agent at the outlet of the catalytic device (1), said given escape content of said reducing agent corresponding to an escape flow rate (fNH3escape) of the reducing agent,(300) measuring continuously using the measurement probe (8) and stabilizing said escape content (CNH3escape) of the reducing agent, via the measurement provided by said probe (8) to be stable over a given period of time, at said stable given escape content (CNH3escape stab),(400a) subsequently ordering the introduction of an ordered additional test flow rate (fNH3theotest) of said reducing agent into the exhaust gas stream upstream of the catalytic device (1),(400b) continuously measuring using the measurement probe (8) until a total content of the reducing agent measured at said probe (8) has stabilized,(500) measuring said stabilized total content (CNH3tot stab) of said reducing agent at the outlet of the catalytic device (1) by means of said measurement probe (8),(600) determining a stabilized true additional test flow rate (fNH3truetest) of said reducing agent entering the catalytic device (1) by subtracting said given stabilized escape content (CNH3escape stab) of reducing agent from said stabilized total content (CNH3tot stab) of the reducing agent and by applying a model for conversion of the content obtained from said subtraction into the true flow rate of the reducing agent;

    wherein the model is implemented in the engine control unit.

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