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A system or method for controlling the delivery of fuel into the transient flow of an exhaust system to control emissions. A mathematical model representative of the exhaust system can be used to determine, based on operating conditions of the exhaust system, a rate of fuel delivery suitable for ach

A system or method for controlling the delivery of fuel into the transient flow of an exhaust system to control emissions. A mathematical model representative of the exhaust system can be used to determine, based on operating conditions of the exhaust system, a rate of fuel delivery suitable for achieving a desired result. The desired result can be to increase the temperature of a diesel particulate filter to a temperature suitable for regeneration without exceeding a temperature that may damage the diesel particulate filter.

대표청구항 ▼

We claim: 1. A method for injecting fuel into a transient exhaust stream of an exhaust system, the exhaust system including a catalytic converter positioned upstream from a diesel particulate filter, the exhaust system also including a fuel dispenser positioned upstream from the catalytic converter

We claim: 1. A method for injecting fuel into a transient exhaust stream of an exhaust system, the exhaust system including a catalytic converter positioned upstream from a diesel particulate filter, the exhaust system also including a fuel dispenser positioned upstream from the catalytic converter, the method comprising: selecting a control volume within the exhaust system, the control volume including the fuel dispenser and the catalytic converter; and using a fuel dispensing formula derived from a transient energy balance equation for the control volume to determine a fuel dispensing rate at which fuel is dispensed into the exhaust stream by the fuel dispenser, the fuel dispensing rate being controlled such that combustion of the fuel at the catalytic converter provides a target exhaust gas temperature downstream of the catalytic converter, the target exhaust gas temperature being suitable to cause controlled regeneration of the diesel particulate filter; the transient energy balance equation including a number of factors, at least some of the factors including: a net energy carried by the exhaust stream entering and leaving the control volume; a heat release rate of the fuel to be dispensed into the control volume by the fuel dispenser taking into consideration a fuel vaporization efficiency and a fuel conversion efficiency at the catalytic converter; and a heat transfer rate between the catalytic converter and the exhaust stream. 2. A method for introducing a reactant into the exhaust stream of a an exhaust system for a diesel engine, the exhaust system including a substrate, a first temperature sensor positioned upstream from the substrate and a second temperature sensor positioned downstream from the substrate, the method comprising: determining a calculated mean temperature of the substrate, the calculated mean temperature of the substrate being calculated and updated on an on-going basis taking into consideration a heat transfer coefficient between the exhaust stream and the substrate, a mass of the substrate, a surface area of the substrate, a specific heat of the substrate and an average temperature of the exhaust stream based on readings taken by the first and second temperature sensors; and using the mean temperature of the substrate as a parameter for controlling the introduction of the reactant into the exhaust stream. 3. The method of claim 2, wherein the substrate is catalyzed to promote a reaction of the reactant at the substrate. 4. The method of claim 3, wherein the reactant includes a hydrocarbon fuel, and wherein the hydrocarbon fuel is injected into the exhaust stream at a location upstream from the substrate. 5. The method of claim 4, wherein the substrate comprises a diesel oxidation catalyst. 6. The method of claim 4, wherein the substrate comprises a lean NOx catalyst. 7. The method of claim 4, wherein the substrate comprises a NOx trap. 8. The method of claim 1, wherein the catalytic converter and the diesel particulate filter are positioned within an exhaust conduit wherein the fuel dispenser includes an injector having a housing positioned outside the exhaust conduit for housing the reactant injector, the housing defining an air line port and a reactant line port, the housing also defining a pre-mix region into which the reactant injector injects reactant; wherein the exhaust system includes a reactant line coupled to the reactant line port of the housing for providing reactant to the reactant injector, wherein the exhaust system includes an air line coupled to the air line port of the housing for providing compressed air to the pre-mix region, the reactant from the injector and the air from the air line being mixed at the pre-mix region to form a reactantlair mixture, wherein the exhaust system includes a nozzle for spraying the reactant/air mixture into the exhaust conduit, and wherein the exhaust system includes a mixed reactant/air conduit for conveying the reactant/air mixture from the pre-mix region of the housing to the nozzle. 9. The method of claim 8, wherein a fuel pressure supplied to the injector is 40 to 100 pounds per square inch. 10. The method of claim 8 wherein an air pressure supplied to the pre-mix region is 10 to 50 pounds per square inch. 11. The method of claim 8, wherein a pressure of the fuel supplied to the injector is 30 to 50 pounds per square inch greater than a pressure of the air supplied to the pre-mix region. 12. The method of claim 8, wherein an air pressure regulator in fluid communication with the air line regulates the pressure of the air within the air line. 13. The method of claim 8, wherein a solenoid valve in fluid communication with the air line controls the flow of air within the air line. 14. The method of claim 8, wherein the housing includes a first block and a second block between which the injector is mounted. 15. The method of claim 1, wherein the exhaust system includes a first temperature sensor positioned upstream from the catalytic converter and a second temperature sensor positioned between the catalytic converter and the diesel particulate filter, wherein the fuel dispensing formula includes a calculated mean temperature of the catalytic converter, the calculated mean temperature of the catalytic converter being calculated and updated on an on-going basis taking into consideration a heat transfer coefficient between the exhaust stream and the catalytic converter, a mass of the catalytic converter, a surface area of the catalytic converter, a specific heat of the catalytic converter and an average temperature of the exhaust stream based on readings taken by the first and second temperature sensors. 16. The method of claim 15, wherein the calculated mean temperature of the catalytic converter is calculated by the formula: where TDOCn is the calculated mean temperature of the catalytic converter, h is the heat transfer coefficient between the exhaust stream and the catalytic converter, ADOC is the surface area of the catalytic converter, mDOC is the mass of the catalytic converter, CpDOC is the specific heat of the catalytic converter, Tgas is the average temperature of the exhaust stream within the catalytic converter, and TDOCn-1 is a previously calculated mean temperature of the catalytic converter. 17. The method of claim 16, wherein the fuel dispensing formula comprises: where {dot over (m)}f is a calculated fuel mass flow rate for reaching the target exhaust gas temperature, Pev is a pressure at the control volume, Vcv is a volume of the control volume, Cp is a specific heat of the exhaust stream, R is an ideal gas constant for the exhaust stream, {dot over (m)}1 is a mass flow rate of the exhaust stream upstream from the catalytic converter, T2des is the target exhaust stream temperature downstream of the catalytic converter, {dot over (m)}2 is a mass flow rate of the exhaust stream downstream from the catalytic converter, T1 is an exhaust stream temperature upstream from the catalytic converter,ηvap is the fuel vaporization efficiency, ηc is the fuel conversion efficiency at the catalytic converter, and h1 is a fuel lower heat value. 18. The method of claim 1, further comprising calculating exhaust mass flow for the exhaust system using pressure data provided by a first pressure sensor positioned upstream from a venturi and a second pressure sensor positioned at a restriction of the venturi, and using the mass flow in concert with the fuel dispensing formula to determine the fuel dispensing rate. 19. The method of claim 18, wherein exhaust gas mass flow is determined by a mass flow sensor. 20. The method of claim 18, wherein exhaust gas mass flow is determined by accessing data from an engine controller. 21. The method of claim 1, wherein the desired exhaust gas temperature for causing controlled regeneration at the diesel particulate filter is in the range of 500 to 700 degree Celsius. 22. The method of claim 3, wherein the calculated mean temperature of the substrate is calculated by the formula: where Tn is the calculated mean temperature of the substrate, h is the heat transfer coefficient between the exhaust stream and the substrate, A is the surface area of the substrate, m is the mass of the substrate, cp is the specific heat of the substrate, Tgas is the average temperature of the exhaust stream within the substrate, and Tn-1 is a previously calculated mean temperature of the substrate.