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US20080083271A1 - Diesel oxidation catalyst (DOC) temperature sensor rationality diagnostic - Google Patents

Diesel oxidation catalyst (DOC) temperature sensor rationality diagnostic Download PDF

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US20080083271A1
US20080083271A1US11/385,045US38504506AUS2008083271A1US 20080083271 A1US20080083271 A1US 20080083271A1US 38504506 AUS38504506 AUS 38504506AUS 2008083271 A1US2008083271 A1US 2008083271A1
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temperature
threshold
exhaust
inlet
temperature sensor
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US7546761B2 (en
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Chuan He
Richard B. Jess
Jay Tolsma
Guojun Shi
Jose L. DeLeon
Kouji Sakumoto
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GM Global Technology Operations LLC
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Chuan He
Jess Richard B
Jay Tolsma
Guojun Shi
Deleon Jose L
Kouji Sakumoto
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Links

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Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
    • F01N11/005—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus the temperature or pressure being estimated, e.g. by means of a theoretical model
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/0231—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Abstract

Description

  • This application claims the benefit of U.S. Provisional Application No. 60/670,526, filed on Apr. 12, 2005. The disclosure of the above application is incorporated herein by reference.

  • The present invention relates to engine exhaust treatment systems, and more particularly to a temperature sensor rationality diagnostic for an exhaust treatment system including a diesel oxidation catalyst (DOC).

  • Diesel engines are internal combustion engines that combust an air and fuel mixture reciprocally drive pistons slidably disposed within cylinders producing drive torque. Diesel engines typically have a higher efficiency than gasoline engines due to the increased compression ratio of the diesel combustion process and the higher energy density of diesel fuel. Consequently, diesel engines commonly achieve better gas mileage than equivalently sized gasoline engines. Vehicle manufacturers incorporate emission control devices into the exhaust treatment systems of diesel engines to reduce emissions.

  • An exemplary exhaust treatment device includes a diesel oxidation catalyst (DOC). A DOC is an exhaust flow through device that includes a honey-comb formed substrate having a large surface area coated with a catalyst layer. The catalyst layer includes precious metals including, but not limited to, platinum and palladium. As the exhaust flows over the catalyst layer, carbon monoxide, gaseous hydrocarbons and liquid hydrocarbon particles are oxidized to reduce emissions.

  • The DOC may be adversely affected when the temperature of the exhaust exceeds a threshold. Inlet and outlet temperature sensors are typically associated with the DOC to monitor exhaust temperatures. Proper functioning of the temperature sensors is required to enable the vehicle control system to monitor exhaust temperature. Because the temperature sensors work over a large operating range (e.g., −40° C. to 800° C.) it has traditionally been difficult to ensure accuracy over the entire range.

  • Accordingly, the present invention provides a temperature sensor rationality control system for an exhaust treatment system having an oxidation catalyst. The temperature sensor rationality control system includes an oxidation catalyst inlet temperature sensor that generates an inlet temperature signal and an oxidation catalyst outlet temperature sensor that generates an outlet temperature signal. A control module determines whether a difference based on the inlet temperature signal and the outlet temperature signal is below a difference threshold when an exhaust temperature is within a threshold range.

  • In other features, the exhaust temperature is greater than the first threshold temperature and is less than the second threshold temperature when a plurality of vehicle operating parameters are within respective threshold ranges. The vehicle operating parameters include engine running time, current fuel rate, exhaust mass flow, engine RPM, coolant temperature and no DPF regeneration occurring. The exhaust temperature is greater than the first threshold temperature and is less than the second threshold temperature when a plurality of vehicle operating parameters are within the respective threshold ranges for a threshold period of time.

  • In another feature, the exhaust temperature is calculated based on at least one of an engine RPM, a primary fuel rate, an injection timing, a turbo boost level, a post fuel rate and an exhaust gas recirculation (EGR) value.

  • In still other features, the difference is determined based on a delayed inlet temperature value. The delayed inlet temperature value is determined based on at least one of a calibration factor, a previous delayed inlet temperature value and the inlet temperature signal. The calibration factor is determined from a look-up table based on an exhaust flow rate and a fueling rate.

  • Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

  • The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

  • Referring now to , an exemplary vehicle 10 is illustrated including an engine 12 that drives a transmission 14 through a coupling device 16 (e.g., clutch, torque converter) and an exhaust treatment system 18. More specifically, air is drawn into an intake manifold 20 through a throttle 22. The intake manifold 20 distributes air into cylinders (not shown). The air is mixed with fuel and the air/fuel mixture is combusted within the cylinders to drive pistons (not shown), producing drive torque. Exhaust generated by the combustion process is exhausted from the engine 12 and into the exhaust treatment system 18 through an exhaust manifold 24.

  • The exhaust treatment system 18 includes a diesel oxidation catalyst (DOC) 26 and a diesel particulate filter (DPF) 28 that reduce emissions. More specifically, a catalyst layer of the DOC 26 induces reaction of the exhaust once the DOC 26 has achieved a threshold or light-off temperature (TLO). Carbon monoxide, gaseous hydrocarbons and liquid hydrocarbon particles are oxidized over the catalyst layer to reduce emissions. The DPF 28 traps soot particles therein preventing the soot from escaping to atmosphere. The DPF 28 periodically undergoes a regeneration process, whereby the soot trapped therein is burned off.

  • A control module 30 regulates operation of the engine and executes the temperature sensor rationality control of the present invention. More specifically, the control module 30 regulates engine fueling and the throttle 22 to achieve a desired engine torque output based on signals generated by various sensors, as described herein.

  • A manifold absolute pressure (MAP) sensor 32 disposed within the intake manifold is responsive to MAP and generates a MAP signal based therein. An engine speed sensor 34 generates an engine speed (RPM) signal and a coolant temperature 36 sensor generates a coolant temperature (TCOOL) signal. The exhaust treatment system 18 includes a DOC inlet temperature sensor 38 and a DOC outlet temperature sensor 40. The inlet temperature sensor 38 generates an inlet temperature (TIN) signal and the outlet temperature sensor 40 generates an outlet temperature (TOUT) signal.

  • The temperature sensor rationality control of the present invention determines temperature accuracy after the exhaust temperature (TEXH) has achieved a threshold temperature (TTHR) and is still below TLO. TEXH is determined based on engine operating conditions and/or a thermal model, as discussed in detail below. The thermal model compensates for the temperature difference (TDIFF) between TIN and TOUT caused by the thermal capacity of the DOC 26. More specifically, in order to compensate for the thermal capacity of the DOC 26, TOUT is compared to a delayed TIN (TINDEL). TINDEL is determined from the following relationship:


  • TINDEL(k)=TINDEL(k−1)×α+(1−α)×TIN

  • where k is the current time step, k−1 is the previous time step and α is a calibration factor determined from a look-up table based on an exhaust flow rate and a fueling rate.

  • The value of TEXH, relative to TTHR and TLO, can be determined using various methods. In one method, engine operating parameters are compared to respective thresholds. If the engine operating parameters are each within their respective thresholds, TEXH is considered to be greater than TTHR and less than TLO. If any of the engine operating parameters outside of their respective thresholds, TEXH is considered to be either less than TTHR or greater than TLO. Exemplary engine operating conditions include, but are not limited to, engine running time, current fuel rate, exhaust mass flow, engine RPM, TCOOL, no sensor faults indicated, no DPF regeneration occurring and whether each of these conditions are met for a threshold period of time. For example, if the engine running time (tRUN) exceeds a threshold running time (tRUNTHR), the current fueling rate (FRCURR) is within a threshold fueling rate range defined by lower and upper fueling rate thresholds (FRLOTHR,FRUPTHR), an exhaust mass flow (mEXH) is within a threshold mass flow range defined by lower and upper thresholds (mEXHLO,mEXHUP), the engine RPM is within a threshold range defined by lower and upper thresholds (RPMLOTHR,RPMUPTHR), TCOOL is within a threshold range defined by lower and upper thresholds (TCOOLLOTHR,TCOOLUPTHR), there are no sensor faults, there is no DPF regeneration occurring and the operating conditions are within their respective threshold for a threshold time, TEXH is considered to be within the range defined between TTHR and TLO.

  • It is alternatively anticipated that TEXH can be calculated as a function of engine operating conditions. Exemplary engine operating conditions include, but are not limited to, engine RPM, primary fuel rate, injection timing, turbo boost, post fuel rate, exhaust gas recirculation (EGR). An exemplary relationship is defined as:


  • TEXH=[f(RPM, FRPRIM, tINJ, boost, FRPOST, EGR)+Offset]×kAMB×kVEH

  • where Offset is a temperature offset based on a learned function of the outlet temperature sensor, kAMB is an ambient condition factor based on an ambient temperature and kVEH is a vehicle condition factor based on vehicle speed and exhaust architecture. It is anticipated that the relationship can be modified to provide a maximum TEXH (TEXHMAX) and/or a minimum TEXH (TEXHMIN).

  • The temperature rationality diagnostic control determines the accuracy of the temperature sensors 38, 40 and can detect a failed sensor or unintended DOC reaction based on TDIFF. TIN and TOUT are compared to TEXH. If either TIN or TOUT are within a threshold range of TEXH, the sensors are operating normally. If either TIN or TOUT are outside of the threshold range of TEXH, the sensors are faulty. Alternatively, if TDIFF is below a threshold difference (TDIFFTHR), the sensors are operating correctly. If TDIFF is below TDIFFTHR, the sensors are faulty.

  • Referring now to , exemplary steps executed by the temperature sensor rationality control will be described in detail. In step 200, control sets a fault count (FC) equal to zero. In step 202, control determines whether test conditions are met. As described in detail above, the test conditions include TEXH being within a threshold range defined by TTHR and TLO and/or engine operating conditions being met that would indicate TEXH is within the threshold range. If the test conditions are met, control continues in step 204. If test conditions are not met, control loops back.

  • In step 204, control determines TIN based on the inlet temperature sensor signal. In step 206, control determines a based on exhaust flow rate and fueling rate. Control determines TINDEL based on TIN, a previous TINDEL and a in step 208. In step 210, control determines TDIFF as the absolute value of the difference of TINDEL and TOUT.

  • In step 212, control determines whether TDIFF exceeds TDIFFTHR. If TDIFF exceeds TDIFFTHR, control continues in step 214. If TDIFF does not exceed TDIFFTHR, control continues in step 216. In step 214, control increases FC. In step 218, control determines whether FC exceeds a threshold FC (FCTHR). If FC exceeds FCTHR, control sets a FAULT status in step 220 and control ends. If FC does not exceed FCTHR, control continues in step 222. Control determines whether a test time (tTEST) exceeds a test time threshold (tTHR) in step 222. If tTEST exceeds tTHR, control sets a PASS status in step 224 and control ends. If tTEST does not exceed tTHR, control loops back to step 202.

  • Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.

Claims (25)

1. A temperature sensor rationality control system for an exhaust treatment system of a vehicle having an oxidation catalyst, comprising:

an oxidation catalyst inlet temperature sensor that generates an inlet temperature signal;

an oxidation catalyst outlet temperature sensor that generates an outlet temperature signal; and

a control module that determines whether a difference based on said inlet temperature signal and said outlet temperature signal is below a difference threshold when an exhaust temperature is greater than a first threshold temperature and is less than a second threshold temperature.

2. The temperature sensor rationality diagnostic of wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when a plurality of vehicle operating parameters are within respective threshold ranges.

3. The temperature sensor rationality diagnostic of wherein said vehicle operating parameters include engine running time, current fuel rate, exhaust mass flow, engine RPM, coolant temperature and no DPF regeneration occurring.

4. The temperature sensor rationality diagnostic of wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when a plurality of vehicle operating parameters are within said respective threshold ranges for a threshold period of time.

5. The temperature sensor rationality diagnostic of wherein said exhaust temperature is calculated based on at least one of an engine RPM, a primary fuel rate, an injection timing, a turbo boost level, a post fuel rate and an exhaust gas recirculation (EGR) value.

6. The temperature sensor rationality diagnostic of wherein said difference is determined based on a delayed inlet temperature value.

7. The temperature sensor rationality diagnostic of wherein said delayed inlet temperature value is determined based on at least one of a calibration factor, a previous delayed inlet temperature value and said inlet temperature signal.

8. The temperature sensor rationality diagnostic of wherein said calibration factor is determined from a look-up table based on an exhaust flow rate and a fueling rate.

9. A method of determining a status of a temperature sensor of an exhaust treatment system of a vehicle having an oxidation catalyst, comprising:

generating an inlet temperature signal at an oxidation catalyst inlet using an inlet temperature sensor;

generating an outlet temperature signal at an oxidation catalyst outlet using an outlet temperature sensor;

calculating a difference based on said inlet temperature signal and said outlet temperature signal; and

determining a status of said inlet and outlet temperature sensors based on said difference when an exhaust temperature is greater than a first threshold temperature and is less than a second threshold temperature.

10. The method of further comprising indicating a fault status when said difference is below a difference threshold.

11. The method of further comprising determining whether a plurality of vehicle operating parameters are within respective threshold ranges, wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when said plurality of vehicle operating parameters are within said respective threshold ranges.

12. The method of wherein said vehicle operating parameters include engine running time, current fuel rate, exhaust mass flow, engine RPM, coolant temperature and no DPF regeneration occurring.

13. The method of wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when said plurality of vehicle operating parameters are within said respective threshold ranges for a threshold period of time.

14. The method of wherein said exhaust temperature is calculated based on at least one of an engine RPM, a primary fuel rate, an injection timing, a turbo boost level, a post fuel rate and an exhaust gas recirculation (EGR) value.

15. The method of wherein said difference is determined based on a delayed inlet temperature value.

16. The method of wherein said delayed inlet temperature value is determined based on at least one of a calibration factor, a previous delayed inlet temperature value and said inlet temperature signal.

17. The method of wherein said calibration factor is determined from a look-up table based on an exhaust flow rate and a fueling rate.

18. A method of diagnosing an operating condition of a temperature sensor of an exhaust treatment system of a vehicle having an oxidation catalyst, comprising:

generating an inlet temperature signal at an oxidation catalyst inlet using an inlet temperature sensor;

generating an outlet temperature signal at an oxidation catalyst outlet using an outlet temperature sensor;

determining a delayed inlet temperature signal based on said inlet signal and characteristics of said oxidization catalyst;

calculating a difference based on said delayed inlet temperature signal and said outlet temperature signal; and

determining a status of said inlet and outlet temperature sensors based on said difference when an exhaust temperature is greater than a first threshold temperature and is less than a second threshold temperature.

19. The method of further comprising indicating a fault status when said difference is below a difference threshold.

20. The method of further comprising determining whether a plurality of vehicle operating parameters are within respective threshold ranges, wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when said plurality of vehicle operating parameters are within said respective threshold ranges.

21. The method of wherein said vehicle operating parameters include engine running time, current fuel rate, exhaust mass flow, engine RPM, coolant temperature and no DPF regeneration occurring.

22. The method of wherein said exhaust temperature is greater than said first threshold temperature and is less than said second threshold temperature when said plurality of vehicle operating parameters are within said respective threshold ranges for a threshold period of time.

23. The method of wherein said exhaust temperature is calculated based on at least one of an engine RPM, a primary fuel rate, an injection timing, a turbo boost level, a post fuel rate and an exhaust gas recirculation (EGR) value.

24. The method of wherein said delayed inlet temperature value is determined based on at least one of a calibration factor, a previous delayed inlet temperature value and said inlet temperature signal.

25. The method of wherein said calibration factor is determined from a look-up table based on an exhaust flow rate and a fueling rate.

US11/385,0452005-04-122006-03-17Diesel oxidation catalyst (DOC) temperature sensor rationality diagnostic Expired - Fee RelatedUS7546761B2 (en)

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US11/385,045US7546761B2 (en) 2005-04-122006-03-17Diesel oxidation catalyst (DOC) temperature sensor rationality diagnostic

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US11/385,045US7546761B2 (en) 2005-04-122006-03-17Diesel oxidation catalyst (DOC) temperature sensor rationality diagnostic
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Cited By (9)

Publication numberPriority datePublication dateAssigneeTitle
US20090107114A1 (en) *2007-10-312009-04-30Caterpillar Inc.Particulate trap temperature sensor swap detection
US20090118969A1 (en) *2007-11-072009-05-07Gm Global Technology Operations, Inc.Method and apparatus to control warm-up of an exhaust aftertreatment system for a hybrid powertrain
US20100050757A1 (en) *2008-08-282010-03-04Detroit Diesel CorporationMethod and system to determine the efficiency of a diesel oxidation catalyst
GB2472986A (en) *2009-08-242011-03-02Gm Global Tech Operations IncMonitoring the light-off temperature of a catalyst
US20110143449A1 (en) *2009-12-102011-06-16Cummins Ip, Inc.Apparatus, system, and method for catalyst presence detection
US20130067989A1 (en) *2011-09-212013-03-21Kia Motors Corp.System and method for detecting pollution by poisonous material for air exhauster of vehicle
WO2013134539A1 (en) *2012-03-072013-09-12Cummins Inc.Method and algorithm for performing an nh3 sensor rationality diagnostic
US9416715B2 (en) 2011-10-072016-08-16Mtu Friedrichshafen GmbhMethod for monitoring an exhaust system of an internal combustion engine
CN109578117A (en) *2018-12-032019-04-05潍柴动力股份有限公司A kind of restoration methods and device of diesel oxidation catalyst

Families Citing this family (6)

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EP2058204B1 (en) *2007-11-072013-05-22GM Global Technology Operations LLCMethod and apparatus to control temperature of an exhaust aftertreatment system for a hybrid powertrain
US8277363B2 (en) 2007-11-072012-10-02GM Global Technology Operations LLCMethod and apparatus to control temperature of an exhaust aftertreatment system for a hybrid powertrain
GB2504360B (en) *2012-07-272016-03-23Perkins Engines Co LtdExhaust fluid treatment apparatus funtionality check
US8935027B2 (en) 2012-08-062015-01-13GM Global Technology Operations LLCMethod and apparatus to effect catalyst light-off in a multi-mode powertrain system
US9879587B2 (en) 2015-10-232018-01-30GM Global Technology Operations LLCDiagnosing oxidation catalyst device with hydrocarbon storage
CN110295985B (en) *2019-06-302020-07-28潍柴动力股份有限公司Method and device for detecting removal of diesel oxidation catalyst

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US5747668A (en) *1995-08-171998-05-05Siemens AktiengesellschaftDiagnostic process for an exhaust gas sensor
US6085575A (en) *1997-10-102000-07-11Heraeus Electro-Nite International N.V.Process for the determination of the exhaust gas temperature and of the air/fuel ratio lambda and a sensor arrangement for execution of the process
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Cited By (18)

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US20090107114A1 (en) *2007-10-312009-04-30Caterpillar Inc.Particulate trap temperature sensor swap detection
US7891177B2 (en) *2007-10-312011-02-22Caterpillar Inc.Particulate trap temperature sensor swap detection
US20090118969A1 (en) *2007-11-072009-05-07Gm Global Technology Operations, Inc.Method and apparatus to control warm-up of an exhaust aftertreatment system for a hybrid powertrain
US8073610B2 (en) *2007-11-072011-12-06GM Global Technology Operations LLCMethod and apparatus to control warm-up of an exhaust aftertreatment system for a hybrid powertrain
US20100050757A1 (en) *2008-08-282010-03-04Detroit Diesel CorporationMethod and system to determine the efficiency of a diesel oxidation catalyst
GB2472986A (en) *2009-08-242011-03-02Gm Global Tech Operations IncMonitoring the light-off temperature of a catalyst
US20110120091A1 (en) *2009-08-242011-05-26Gm Global Technology Operations, Inc.Method and apparatus for monitoring the light-off temperature of a diesel oxidation catalyst
US9181841B2 (en) 2009-08-242015-11-10GM Global Technology Operations LLCMethod and apparatus for monitoring the light-off temperature of a diesel oxidation catalyst
GB2472986B (en) *2009-08-242016-09-07Gm Global Tech Operations LlcMethod and apparatus for monitoring the light-off temperature of a diesel oxidation catalyst
US9658177B2 (en) 2009-12-102017-05-23Cummins Filtration Ip, Inc.Apparatus, system, and method for catalyst presence detection
US9939399B2 (en) 2009-12-102018-04-10Cummins Filtration Ip, Inc.Apparatus, system, and method for catalyst presence detection
US20110143449A1 (en) *2009-12-102011-06-16Cummins Ip, Inc.Apparatus, system, and method for catalyst presence detection
US9303545B2 (en) *2009-12-102016-04-05Cummins Filtration Ip, Inc.Apparatus, system, and method for catalyst presence detection
US8820048B2 (en) *2011-09-212014-09-02Hyundai Motor CompanySystem and method for detecting pollution by poisonous material for air exhauster of vehicle
US20130067989A1 (en) *2011-09-212013-03-21Kia Motors Corp.System and method for detecting pollution by poisonous material for air exhauster of vehicle
US9416715B2 (en) 2011-10-072016-08-16Mtu Friedrichshafen GmbhMethod for monitoring an exhaust system of an internal combustion engine
WO2013134539A1 (en) *2012-03-072013-09-12Cummins Inc.Method and algorithm for performing an nh3 sensor rationality diagnostic
CN109578117A (en) *2018-12-032019-04-05潍柴动力股份有限公司A kind of restoration methods and device of diesel oxidation catalyst

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Differences between DOC, DPF, and SCR filters

It has been said that necessity is the mother of invention and modern compression ignition engines are such an example of remarkable engineering. In order to achieve their necessary power and performance every facet of each component is in finely tuned balance. Further development arose thanks to the necessity to comply with emissions standards, and several techniques to cater to this requirement emerged. But why do we have more than one filter in the exhaust system and what are their differences?

Differences between DOC, DPF and SCR Filters

The diesel exhaust aftertreatment system has arisen to solve one problem; the difficult task of removing harmful particulate matter from diesel engine emissions.

Untreated emissions from a diesel engine contains a cocktail of harmful chemicals and particulate matter, however today’s system can reduce this down to harmless substances, oxygen, and water.

The exhaust aftertreatment devices that are applied to vehicles are Diesel Oxidation Catalysts (DOC), Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) catalysts.

Using a combination of physical mechanisms and chemical reactions these systems can, under the right conditions, achieve near complete removal of particulates and harmful gases.

There are many variances between these systems but the biggest difference between DOC, DPF and SCR filters lies in their individual purposes.

 common exhaust aftertreatment system sequence

Regeneration

The DOC is the first device in the after treatment system. It is a flow through filter that contains precious metals to start the oxidation of hydrocarbons, carbon monoxide and unburned fuel and oil. Both the DOC and the DPF are honeycomb ceramic filters.

However, unlike the DOC, the DPF is a wall-flow filter that traps any remaining soot that the DOC couldn’t oxidize. The soot remains in the DPF until it is regenerated either passively or actively. Passive regeneration occurs when the vehicle’s normal operating temperatures and the DPF will oxidise the particulates anywhere between 275-360⁰ Celsius.

Active regeneration is instigated when sensors detect an excessive build-up of particulates within the DPF. Raw fuel is injected into the exhaust stream to trigger temperatures over 600⁰ Celsius is required oxidise the build-up of soot.

Back pressure usually returns to normal after the soot is gone, however, don’t forget about the ash! Ash builds up inside the DPF and does not burn or oxidize like soot and will remain until removed.

Ash is made of minerals, metals and other trace elements from the breakdown of lubricants, additives and engine wear.

Ash builds up at a much slower rate than soot but if ignored will eventually cause increased back pressure, fuel consumption and sometimes DPF failure. As ash builds inside the DPF the number of active regenerations increase causing poor fuel economy, extreme high temperatures, and more constant back pressure that can be detrimental to the turbo charger.

The longer the ash is left inside the DPF the greater the chance of it hardening into a plug which closes off a portion of the filter.

A vehicle operator will be the first to notice the shorter intervals between regenerations which is the first clue to ash build up and the need to remove the DPF for cleaning. This can also be observed by datalogging the regen cycles in the workshop with diagnostic equipment. When the DPF is removed for cleaning it is always a good practice to also remove the DOC and clean it as well if necessary.

The last component in the after treatment system is a flow through SCR catalyst which introduces Diesel Emissions Fluid (DEF) to the process. This fluid contributes to the further break down of nitrogen oxides that pass through to the SCR filter. Typically the SCR filter doesn’t need maintenance except in rare events where a component related to the DEF fluid fails.

 Click here to download the DPF300 Master Series

Core Contents

At the heart of these components is an ultra-fine filter in which to capture microscopic particulates. A DOC can contain more precious metals than a DPF and metals such as platinum bonds with the oxygen molecules in hydrocarbons.

A DPF’s core can be made of a few different materials but the most common are cordierite composites. An SCR catalyst has valuable filter contents in the form of ceramic materials and precious metals.

All these filters contain a specific recipe of metals selected for their role in the chemical reactions necessary to effectively clean the emissions. In addition, they are manufactured with materials to resist the higher temperatures of an active regeneration cycle.

Unfortunately the core materials of these filters have made them the target of thefts, especially on vehicles with high ground clearance like people carriers, vans, and trucks.

Maintenance

Although these filters differ in their location on the vehicle they all share the need for maintenance and servicing because the filters can still get congested in their own ways.

If blockage builds up it can cause irreparable damage to the exhaust system resulting in massive repair costs, unscheduled vehicle down time, and particulate matter entering the environment.

The DPF and DOC filters are suitable for pneumatic and thermal cleaning; conversely, because the SCR is a closed unit it is not suitable for the pneumatic cleaning. It can still get blocked by hardened DEF and if this happens it is not usually serviceable, although specialists at FSX Equipment, Inc are making headway with a custom program for their equipment which is seeing early success in thermally treating the SCR.

A balancing act

These filters and catalysts are just as sensitive as the rest of the engine and in equally delicate balance with each other. They are in harmony with the engine’s operation but also respond to how the car is driven. If the vehicle only ever does unsuitable journeys for producing the high temperatures required for the different types of regeneration, then irreversible damage to the DPF is more likely.

Similarly, a vehicle such as a truck or bus which is on the road the majority of the time would find better passive regeneration and longer service life before maintenance is necessary.

A necessary balancing act is also to be made between vehicle driving and appropriate maintenance for a healthy exhaust treatment system.dots.png

Sours: http://www.hartridge.com/blog/3-differences-between-doc-dpf-and-scr-filters
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Dissolved/Total Organic Carbon (DOC/TOC)

Background

Table 1 - Typical DOC levels found in natural waters and sewage/effluent

Dissolved Organic Carbon (DOC) is operationally defined as the amount of organic carbon based compounds that can pass through a 0.45 �m filter. Measurement is usually conducted in the laboratory using expensive benchtop analysers that oxidize organic carbon in the water sample to form carbon dioxide. There are two different methods for the oxidation of organic carbon to CO2: (1)combustion in an oxidizing gas; and (2) UV or heat driven chemical oxidation with a persulfate solution. A conductivity detector or an infrared detector then detects the released CO. Unfortunately these techniques require expensive and power hungry laboratory equipment with high reagent costs.

Why is it important

In natural river systems, the quantity of DOC is of interest to river basin managers as shifts in concentration can alter nutrient levels, pH, light absorbance and photochemistry of the river system. In addition, high DOC concentration poses many problems for drinking water treatment. In Particular, it can influence coagulant demand, filter backwash runtime,disinfectant dose and the formation rate of disinfectant by-products(Trihalomethanes � THMs). THMs have long-term negative implications for health and formation potential is a critical consideration when chlorinating drinking water high in DOC. Furthermore, high DOC can lead to water discolouration. However, to date real-time DOC measurement hasrequired expensive monitoring cabinets with high maintenance requirements and reagents costs. Hence, many industrial and environmental monitoring regimes have been comprised of sporadic grab samples with analysis subsequently undertaken in a laboratory.

Challenges associated with DOC monitoring

Despite the test being entrenched in legislation there are numerous problems and challenges associated with use of the test:

  • There is a lag until results are available (transportation to lab + analytical test time 1h),hence damage can occur before the data is available;
  • The test require expensive laboratory equipment;
  • The test involves dangerous chemicals that need careful disposal and are potentially harmful to operators;

It is clear that a move from traditional laboratory testing to in-situ (real-time) monitoring would help to alleviate some of the problems outlined above. It would immediately address points I - III and would help to improve spatial temporal resolution of monitoring that would be directly beneficial to basin managers, water companies and legislators alike.

Proteus the real-time solution for DOC monitoring

Figure 1. Image of the Proteus for DOC monitoring with bluetooth module and tablet display.

The Proteus is a new product launched by Proteus instruments providing users with a robust,repeatable, low maintenance sensor platform for measuring DOC in real-time. The Proteus is underpinned by comprehensive research exploring the use of in-situ fluorescence as a technique for real-time DOC measurement. The Proteus for DOC monitoring (See Fig. 1) is a multi-parameter instrument that incorporates a CDOM fluorometer, turbidity sensor and thermistor to provide real time measurement of the bulk dissolved organic load, negating the need for couriers and laboratory analysis. Using a robust correction algorithm the CDOM signal is corrected, in real time, for temperature interference. The result is a repeatable measurement that can provide instantaneous DOC measurement with a simple site specific calibration for turbidity and CDOM relationship with DOC (Fig. 3).


Fluorescence spectroscopy is a selective and sensitive optical technique enabling in-situ,real-time measurement of dissolved organic matter. Molecules absorb light of a specific wavelength and orbiting electrons are excited to a higher energy state .The electrons then emit light of a specific wavelength to return to the base state.


The dissolved organic matter pool can be mapped in optical spaced based on its fluorescent properties (see Fig. 2). A subset of the coloured dissolved organic matter (CDOM) pool is fluorescent and has a distinct fluorescence peak (Fig.2). This peak is primarily associated with humic and fluvic acids, the by-products of microbial degradation of vascular plant material. The intensity of the CDOM fluorescence signal, often reported in quinine sulphate (QSE) units, is strongly correlated to DOC concentration and TOC. Numerous published studies from a wide range of geographical locations have correlated CDOM fluorescence with DOC and our site-specific calibrations can provide users with accurate and highly repeatable measurements (see Fig. 3).

Graphs showing optical configuration of the Proteus for DOC monitoring with a schematic of the measurement set up (left) and the CDOM measurement region highlighted in optical space (right)Figure 3. Graph showing an example of a site specific CDOM-DOC calibration for an urban river system

Applications

  • Catchment monitoring (upland / peatland)
  • Assessing organic load through water treatment works
  • Process control - Filter management and coagulation control
  • Monitoring disinfection by-product formation potential
  • Monitoring raw water intake
Sours: https://www.proteus-instruments.com/parameters/dissolved-organic-carbon-doc-sensors/
BAD DOC (diesel oxidation catalyst)/ fault code 1691 Cummins regen issues

DISSOLVED ORGANIC CARBON (DOC)

Dissolved Organic Carbon or DOC is a measurement of the amount of organic matter in water that can be passed through a filter, commonly 0.45 µm.

HOW WE MEASURE DOC IN REAL TIME

Real Tech’s innovative reagent free DOC sensors utilizes patent-pending and proprietary technologies to provide superior measurement performance across multiple wavelengths of light using UV LEDs. Many compounds absorb light in the UV-VIS spectrum including organic compounds. The sensors measure organics in a multi-dimensional way that results in improved correlations to aggregate organics water quality parameters, such DOC and TOC. This also allows the sensors to be able to detect changes in the composition of organics independently of their concentration. Real Tech’s affordable, plug & play real-time TOC/DOC solutions are advancing wastewater management.

Learn more about our real-time TOC/DOC monitoring solutions>

IMPORTANCE OF DOC FOR DRINKING WATER

For drinking water, Dissolved Organic Carbon is an important water quality parameter measured for several purposes. Elevated levels of DOC may interfere with the effectiveness of disinfection processes such as UV, ozone and chlorination thus should be monitored for removal prior to disinfection. In plants that disinfect with chlorine, DOC concentrations are a primary concern due to the harmful by-products that form when chlorine reacts with organic matter. DOC in finished water can lead to aesthetic problems and increase the potential for bacterial regrowth in the distribution system. Regulations for DOC are specific to each country, with aesthetic objective in drinking water being approximately 5 mg/L. Additionally, DOC is used in the calculation of SUVA which determines the aromatic portion of DOC, a major precursor for THM formation.

DELAYED LAB RESULTS LIMIT ACTION

Relying on grab samples leads to significant delays. When results come back from the lab, the information is usually of little value for process control and improving plant performance. The DOC procedure requires that the sample be passed through a 0.45 um filter prior to analysis. The test involves converting all organic carbon in a water sample to carbon dioxide (CO2) by utilizing heat and oxygen, chemical oxidants or UV radiation. The resultant CO2 concentration is measured with an infrared analyzer and reported as organic carbon (mg/L). The test takes 5-10 minutes to yield results in the lab, with continuous reagent-based on-line analyzers also available.

Plants need a practical reagent less solution that delivers continuous information to operations personnel. Real Tech has the solutions to help our clients get the information they need, when they need it. Discover our real-time TOC/DOC monitoring solutions here.

Sours: https://realtechwater.com/parameters/dissolved-organic-carbon/

Sensor doc

DOC (Dissolved Organic Carbon)

Dissolved organic carbon (DOC) is operationally defined as the total quantity of organic carbon compounds that pass through a 0.45µm filter, and represents the vast majority of organic material in most water samples. In aqueous systems DOC influences a range of geochemical processes by directly controlling pH levels. Furthermore, it influences water colour, the transport and degradation of pollutants, the depth of the photic zone and can cause the formation of disinfection by-products. 

Organic carbon occurs as the result of decomposition of plant or animal material. Organic carbon present in soil or water bodies may then dissolve when contacted by water. This dissolved organic carbon moves with both surface water and groundwater. DOC is an extremely important part of the carbon cycle and serves as the primary food source for most aquatic wildlife. However, it can also contribute to the acidity of a water body and can increase light attenuation thus detrimentally affecting phototrophic organisms in an aquatic environment. Therefore, as with most things, moderation is key regarding DOC concentration. 

Sours: https://www.rshydro.co.uk/water-quality-monitoring-equipment/water-quality-monitoring-parameters/doc-dissolved-organic-carbon-water/
NISSAN TITAN DIESEL DOC DPF SCR DEF SYSTEM EXPLAINED

Journal Archive

Introduction

To comply with the US Interim Tier 4 or EU Stage III B emission standards, implementation of either a particulate matter (PM) or a nitrogen oxides (NOx) aftertreatment is recommended. Deployment of aftertreatment enables the engine to extend its power range, altitude capabilities and transient performance characteristics. Both exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) technologies are available for the Interim Tier 4 market. The choice between EGR and SCR for NOx reduction depends on the original equipment manufacturer's (OEM's) production history, technology experience, customer requirements and long term product strategy. Engines with EGR consume only diesel fuel but typically require the fitment of a DPF. DPF active regenerations mean that the maximum skin temperatures of the aftertreatment devices and tailpipe exhaust gases must be limited by the exhaust system design.

US Interim Tier 4 or EU Stage III B standards, shown in Table I, have been in effect since 1st January 2011. Besides significant tightening of criteria pollutant limits, a new Non Road Transient Cycle (NRTC) was introduced. Emission compliance on the NRTC is required on top of the existing eight mode steady state test. Speed and torque definitions of NRTC and eight mode tests are displayed in Figure 1. Emissions from cold and hot NRTC tests are weighted in a similar way to those for on-highway regulations. Not-to-exceed (NTE) rules equivalent to those for on-highway applications also apply to non-road engines.

Table I

Interim Tier 4 Criteria Pollutant Limits

Pollutant, g kWh−1Engine rated power, kW

<5656–129130–560
NOx3.42
PM0.030.020.02
NMHC [NOx + NMHC][4.7]0.190.19
CO553.5
Fig. 1.

Non-Road Transient Cycle (NRTC) and eight mode test cycles. Circle points are eight mode; % represents emission weighing factor per point

Non-Road Transient Cycle (NRTC) and eight mode test cycles. Circle points are eight mode; % represents emission weighing factor per point

NOx and PM criteria pollutant limits for engines above 130 kW are higher than those for 2007 on-highway trucks. However, the NRTC has a higher average load factor and is significantly more transient than the Federal Test Protocol (FTP) heavy-duty cycle. The NOx limit for engines below 130 kW is 3.4 g kW−1. Engines with a power output below 56 kW must comply with a combined NOx + non-methane hydrocarbons (NMHCs) limit of 4.7 g kWh−1. The required emission useful life is 8000 h for all diesel engines above 37 kW. This requirement differs signficantly from those for on-highway engines (1).

Different factors must be taken into account when designing exhaust aftertreatment systems. Non-road applications are very diversified with a wide range of engine configurations, power bands and machine forms. Some examples are shown in Figure 2. Agricultural applications, particularly row-crop tractors (Figure 2(a)) and harvesters (Figure 2(b)), have high load factors with signficant portions of operating time at full loads and rated speeds. Construction machines (Figures 2(c) and 2(d)) demand highly transient engine performance, altitude capabilities and longevity. Utility tractors (Figure 2(e)) and small construction machines (Figure 2(f)) can operate persistently at light loads with extended idle time. Their usage profiles are sporadic. This market segment is very sensitive to cost, especially the initial machine purchase price.

Fig. 2.

Examples of non-road machines produced by John Deere, including: (a) row-crop tractor; (b) harvester; (c) and (d) construction machines; (e) utility tractor; (f) a small construction machine (Images © copyright John Deere)

Examples of non-road machines produced by John Deere, including: (a) row-crop tractor; (b) harvester; (c) and (d) construction machines; (e) utility tractor; (f) a small construction machine (Images © copyright John Deere)

Most non-road machines are used for commercial purposes, therefore reliability and uptime are premium for the equipment owners and operators. Modern large scale agriculture and construction operations require a fleet of machines to work together. If one piece of equipment goes down, the whole operation may be jeopardised. Further, production volumes for the equipment vary drastically. High volume equipment is manufactured in tens of thousands of units annually, while specialty machines may be made at a rate of a handful a year. And non-road machines often have to perform at extreme ambient temperatures, high altitudes and off-level positions. Some machines operate in remote areas, in harsh terrains and under unique environmental conditions.

System Design for Interim Tier 4

Three types of system designs are available for Interim Tier 4 compliant machines. For engines with power output above 130 kW, both cooled EGR (cEGR) and SCR are offered by different manufacturers. For engines under 130 kW, cEGR with a DPF is currently the most popular system, although some cEGR engine applications with a narrow power range below 130 kW will not use particulate filters. Engines have been designed and calibrated to meet the PM standards with or without a DOC (2). This product strategy becomes technically feasible when permitted NOx output levels are 3.4 g kWh−1. Several OEMs offer both cEGR and SCR technologies depending on machine applications (3).

At John Deere, externally cooled EGR technologies had been successfully implemented on Tier 3 engines, offering fuel economy advantages over the alternative approach of internal EGR and fuel injection timing retards. John Deere's global product strategy for Interim Tier 4 is cEGR technology with a DPF. Due to the variability of the applications, only a high efficiency wall flow DPF was considered, although it would be technically feasible to meet the PM standards with a partial flow filter or a DOC. To be fully robust towards all applications and operating conditions, active DPF regenerations were enabled for each engine.

Implementation of any aftertreatment technology must overcome its respective challenges for non-road applications. The following discussions will focus on design and performance development of EGR with DOC-DPF solutions for John Deere Interim Tier 4 products. How engine and aftertreatment systems were integrated and optimised to ensure quality, reliability, performance and emission compliance will be reviewed, and perspectives on design trade-offs will be provided.

Engine and DOC-DPF Designs

Five engine families are offered from John Deere for the Tier 4 market. The engine line up is summarised in Table II.

Table II

Tier 4 Engines Made by John Deere

CriteriaDisplacement, l

2.94.56.8913.5
Number of cylinders34666
Max power rating, kW56129224317460
Fuel systemCommon railCommon railCommon railCommon railElectronic unit injector
TurbosSingleSingleDualDualDual
Cooled EGRNoYesYesYesYes

Interim Tier 4 engines were based on Tier 3 engines using cEGR technology, re-optimised to meet the new NOx standards and to facilitate active DPF regenerations. Precise control of EGR rates and combustion events under transient operations was achieved by a redesigned engine control unit (ECU) with a new software package. A single ECU manages both engine operations and aftertreatment performance.

Engine out PM and NOx predictive models were used to calculate DPF soot loadings. New engine combustion modes enabled the engine to raise exhaust gas temperatures when DPF active regenerations were required. This was accomplished by increasing engine fuelling and reducing exhaust flow through an air intake throttle or an exhaust brake. Exhaust temperature management is critical to ensure the completion of an active DPF regeneration event when the exhaust temperature can fall below the pgm catalyst light-off temperature in a normal combustion mode. Capable engine hardware and calibration strategies eliminated the need for an exhaust diesel burner.

The DOC and DPF were sized according to exhaust flow rates, which correlated well with engine power outputs if EGR rates and air to fuel ratios were similar. A total of seven DOC-DPF sizes were designed and released for the five engine families ranging from 37 kW to 460 kW. The DPF dimensions are summarised in Table III. Each design also features ash serviceability, inlet/outlet rotatability, three temperature sensors and one delta pressure sensor. Round filters with a larger diameter and shorter length were preferred for vehicle installations as they provide lower DPF pressure drop, higher volumetric soot loading and active regeneration robustness. Filters made of 200 cells per squre inch (cpsi) cordierite and 300 cpsi silicon carbide (SiC) materials were applied to engines above 130 kW and under 130 kW, respectively. DOC substrates were sized to have the same diameters and approximately half the volume of the filters.

Table III

DPF Sizes Available for Different Engines

Size 2Size 3Size 4Size 5Size 6Size 7Size 8
DPF diameter, inches7.599.59.510.51213
DPF length, inches6689111112.5

DPF designs must consider the worst case pressure drop when loaded with ash and soot. The ash cleaning service requirement is 4500 h for engines above 130 kW and 3000 h for engines under 130 kW. A 200 cpsi cell structure is more tolerant towards ash accumulations, and is therefore preferred for applications above 130 kW. For engines under 130 kW, a higher volumetric soot limit and smaller volume filters favour 300 cpsi cell structures. A 300 cpsi filter offers lower pressure drop in a soot loaded state due to its higher geometric surface area and a thinner soot layer. In addition, smaller SiC filters fit better into compact vehicles.

A DOC was designed to convert nitrogen monoxide (NO) to nitrogen dioxide (NO2) for passive regenerations and to provide high hydrocarbon (HC) oxidation activity for active DPF regenerations. PGM loading was selected to provide adequate residual conversion efficiencies of NO to NO2 as well as sufficient HC light-off performance beyond 8000 h. A catalysed DPF with a low pgm loading was highly effective to prevent HC emissions during active DPF regenerations. The catalyst on the DPF was highly active for HC oxidations during active regeneration because of high reaction temperatures and an abundance of oxygen. NO2 generated by the DPF catalyst also promoted more passive regenerations. Design and function relationships are summarised in Table IV.

Table IV

DOC-DPF Design-Function Matrix

Design criteriaFunction criteria

DOC DPF
VolumeHC slip, NO to NO2 conversion, ΔPaSoot and ash loading, ΔP
Platinum group metal loadingsNO to NO2 conversion, HC quench temperatureHC slip clean up, secondary NO2
Cell structureΔPAsh loading, ΔP
Length/diameter ratioDOC retention, vehicle packageSoot limit, DPF retention, ΔP
MaterialReliability, costSoot loading

The DOC, DPF and exhaust gas sensors were packaged and integrated into a converter assembly, shown in Figure 3. An integrated DOC-DPF design was preferred over separated DOC and DPF converters as it required less space and had higher efficiency. This system design eliminated the need for two additional end cones and reduced heat loss and pressure drop. To accommodate diversified vehicle installations, the inlet and outlet cones were made fully rotatable. Two serviceable flanges, one on each side of the DPF, allowed the DPF to be removed for ash cleaning. Cylindrical converters with two service flanges provided flexibility in the installation of aftertreatment sensors and the positioning of wire routings. Each DOC-DPF converter contained three temperature sensors and one delta pressure sensor across the DPF. The DOC inlet temperature sensor (T1) was used to initiate HC dosing for active regenerations; the DOC outlet sensor (T2) was used primarily for temperature control; and the DPF outlet sensor (T3) was used for temperature diagnostics.

Fig. 3.

Integrated DOC-DPF converter schematic. T1, T2, T3 = temperature sensors; ΔP = delta pressure

Integrated DOC-DPF converter schematic. T1, T2, T3 = temperature sensors; ΔP = delta pressure

The DOC-DPF converters were heavily insulated, including areas around the sensor ports, to keep converter skin temperatures below the required limits even during active DPF regenerations. The design assumed no air flow around the converters. Under normal engine operating conditions, which accounted for over 97% of the total time, the DOC-DPF converter skin temperature was lower than that typically found for a traditional muffler. Since the DOC-DPF converters were internally insulated with a stainless steel sheet metal surface, any external air flow would effectively reduce skin temperatures further.

For engines above 130 kW, HC was delivered to the DOC through an airless exhaust fuel doser, as shown in Figure 4. A tip coking resistant design was selected. No air purging or tip cleaning service was necessary. Late post injections were used for engines under 130 kW.

Fig. 4.

An exhaust fuel hydrocarbon dosing system schematic

An exhaust fuel hydrocarbon dosing system schematic

The exhaust fuel doser was mounted next to the engine turbocharger to maximise fuel evaporation and mixing. For engines with two-stage turbochargers, a fuel doser was placed between the two turbines. The second stage turbine served as an active mixer. Uniform HC distributions maximised DOC catalytic efficiencies and exhaust temperature homogeneities for DPF regenerations. Perfect HC mixing avoided hot spots on the DOC and reduced its degradation rate.

Diesel Oxidation Catalyst-Diesel Particulate Filter Performance

Wall flow DPFs were selected due to their high PM trapping efficiencies and their robustness towards diversified applications and engine operating conditions. Measured PM trapping efficiencies on a 9 l engine are summarised in Table V. The results demonstrated a filtration efficency of over 95% with a brand new DPF. The PM trapping efficiency well exceeded 99% when the ramped modal tests were repeated and a soot layer had been established on the DPF. Similar performance data for a DPF after 5000 h field usage showed efficiencies greater than 99% both before and after an ash cleaning service.

Table V

Measured DPF PM Trapping Efficiencies

Ramped modal cycleTrapping efficiency, %
DPF first test (brand new DPF)96.6
DPF second test99.9
DPF third test100

The full benefits of passive regenerations were achieved with a DOC and a catalysed DPF (4). The DOC oxidised NO to NO2 under normal engine operating conditions. A production design DOC, after accelerated ageing to simulate 8000 h field usage, was capable of providing NO to NO2 conversion efficiencies of over 50%, as shown in Figure 5. Each data point in Figure 5 represents an engine operating condition. The bubble size signifies the actual engine out NOx ppm level. To fully benefit from passive soot oxidations, the DPF soot predictive models must account for the soot and NO2 reaction rates, and adjust for catalyst degradation over time.

Fig. 5.

NO2:NOx ratio at a DOC outlet

NO2:NOx ratio at a DOC outlet

Due to a higher NOx limit of 3.4 g kWh−1, engines for applications under 130 kW produce less PM. Table VI compares the NOx:PM ratios of an engine running at 2 g kWh−1vs. 3.4 g kWh−1 permitted NOx output levels. A higher NOx:PM ratio provided a greater opportunity for passive regenerations. In principle, active regeneration is only required when an engine operates persistently at low loads with low exhaust temperatures. Under low load conditions, the engines produced little soot and the DPF soot loading rates were low. Infrequent active regenerations for engines under 130 kW enabled HC to be delivered by late post injections without oil dilutions or compromises in engine durability.

Table VI

Comparison of NOx:PM Ratios for Engines Above and Below 130 kW

PollutantEngine rated power, kW

<130>130
NOx, g kWh−13.42
PM, g kWh−10.050.08
NOx:PM ratio6825

At 2 g kWh−1 NOx for engines above 130 kW, active regenerations were more frequent. But significant passive regenerations were also observed. Engines for applications above 130 kW tended to operate at higher average loads with temperatures over 250°C, which are more favourable for passive regenerations. High speed and low load engine operations tended to produce more PM and lower exhaust temperatures, and therefore required more frequent active regenerations than other operating conditions.

Passive Regenerations

To assess the passive regenerations, a 4.5 l Interim Tier 4 engine was programmed to repeat a tractor cycle on an engine dynamometer. Engine out soot was measured by an AVL List GmbH smoke meter. The DPF was periodically weighed to determine the soot loading levels. The results are shown in Figure 6. DPF soot levels reached a balanced point below the soot limit of the DPF material, and an increasing percentage of soot was oxidised passively over time. Approximately 80% of engine out soot was oxidised passively in 50 h, 85% in 100 h and 90% in 150 h. In theory, no active regenerations were required for this drive cycle, but in practice active DPF regenerations were necessary as they allowed the soot predictive models to reset and system performances to recover from slow sulfur poisoning. Furthermore, an active regeneration can effectively allow the system to recover from mis-fueling with high sulfur fuels.

Fig. 6.

Passive regeneration test on DPF for a 129 kW rated 4.5 l engine

Passive regeneration test on DPF for a 129 kW rated 4.5 l engine

Figure 7 displays the passive regenerations of a DOC-DPF system on a John Deere 744K wheel loader powered by a 220 kW 9 l Interim Tier 4 engine. The 744K loader was operated to perform real world truck loading routines. Soot on the DPF was determined by weighing the DPF module periodically. Over a span of 50 h, soot on the DPF reached a balance point far below the soot mass limit of the DPF material. The truck loading cycle is one of the most transient operations for non-road applications.

Fig. 7.

Passive regeneration test for a DOC-DPF system on a John Deere 744K wheel loader with a 9 l engine

Passive regeneration test for a DOC-DPF system on a John Deere 744K wheel loader with a 9 l engine

An alternative to the passive regeneration DOC-DPF system is to use a burner-DPF combination to enable active regenerations. However this has the disadvantage of greater mechanical complexity. In practice a DOC is recommended even if a full capacity burner is used to benefit from passive regenerations.

Active Regenerations

During an active regeneration, the engine switches to an exhaust temperature management mode to ensure the exhaust gas temperature stays above 275°C at the DOC inlet. HC from an exhaust doser or from late post injections enters the downstream DOC. Released fuel energy from oxidation reactions heats the exhaust gas before it reaches the DPF. An energy balance model calculates the required fuel quantity based on temperature rise demands and exhaust flow rates. The T2 sensor, at the DOC outlet, provides feedbacks for closed loop controls. A fast response control system ensures the DOC outlet temperature stays on target while engine operations vary considerably. To verify the tight DPF inlet temperature control, an active regeneration was enabled during a NRTC test. The results are shown in Figure 8. Despite large fluctuations of engine speeds and torques, the DOC outlet temperature was maintained around 600°C and the active regeneration was sustained for the whole NRTC.

Fig. 8.

DOC outlet temperature during a NRTC with active regeneration

DOC outlet temperature during a NRTC with active regeneration

A DOC offers a cost effective means to actively regenerate a DPF while providing the full benefit of passive regenerations. A DOC oxidises nearly all the injected HC under most conditions, except near peak exhaust flows. The small amount of slipped HC is oxidised over the downstream platinum-palladium (Pt-Pd) catalysed DPF, as shown in Figure 9. The black bar represents the HC concentration before the DOC and is above 2000 ppm (off the scale of measurement). The blue bar represents the measured HC level at the DOC outlet, or HC slip. Only low ppm levels of HC were detectable at the DPF outlet, represented by the green bar. Despite a light pgm loading, the catalysed DPF was very efficient for HC oxidations during active regenerations due to its large volume and high reaction temperatures. At lower flow conditions, DOC HC oxidation efficiency was nearly 100%.

Fig. 9.

HC emission during an active regeneration of a DPF

HC emission during an active regeneration of a DPF

The DOC ensured a good energy balance for temperature controls with little waste. Even after full useful life of 8000 h, the HC oxidation efficiency of the DOC for active regenerations was hardly changed.

The DOC was also effective at oxidising HC under normal operating conditions. Figure 10 shows the performance of a DOC for reducing engine out HC during a NRTC test. The cumulative engine out total HC is shown as the black line which, in this case, already meets the emission standard of 0.19 g kWh−1 (shown as the green line). The DOC reduced an additional 95% of the engine out HC, as shown by the blue line. The red curve represents the tailpipe HC when an active regeneration was enabled with DOC.

Fig. 10.

NRTC HC emission with and without DPF active regenerations

NRTC HC emission with and without DPF active regenerations

Although a DOC is not required for HC emission compliance, removing HC is beneficial for extending DPF active regeneration intervals. The DOC oxidises the soluble organic fraction of PM and extends the soot loading limit by eliminating the excess exotherm associated with HC oxidation during an active regeneration. Active regeneration is an efficient way to oxidise soot. During an active regeneration, the fuel consumption is increased, but this is necessary for DPF applications.

Assisted Passive Regenerations

An alternative approach is to raise the exhaust temperature to 300°C to promote passive soot oxidation by NO2. This is sometimes refered to as assisted passive regeneration.

A simple energy model was used to compare the fuel consumptions of an active regeneration vs. an assisted passive regeneration. Assumptions used for the calculations are summarised in Table VII. The base exhaust temperature was kept at 150°C. An active regeneration raised the exhaust temperature by 450°C with a total regeneration time of 30 minutes. An assisted passive regeneration had a lower temperature increase and was assumed to take 2 h to oxidise the same amount of soot.

Table VII

Assumptions Used for Fuel Consumption Calculations of Regenerations

ParameterAssisted passive regenerationActive regeneration
Temperature increase, °C150450
Time, min12030

The fuel consumption was time averaged between normal and regeneration events. The results are shown in Figure 11. This conservative simulation revealed a 1.5% fuel consumption increase with an active regeneration interval of 10 h. As the regeneration interval increased, the average fuel consumption decreased. With a 50 h regeneration interval, the average fuel consumption increase was less than 0.5%. These estimates are consistent with previously published results (5). It may be concluded that an active regeneration is more fuel efficient than an assisted passive regeneration.

Fig. 11.

Time averaged fuel consumptions of active vs. assisted passive regenerations of a DPF

Time averaged fuel consumptions of active vs. assisted passive regenerations of a DPF

Steady State Tests

Steady state eight mode emission results of a fully aged engine aftertreatment system for a 9 l engine are shown in Figure 12. The blue bars represent the US Interim Tier 4 or EU Stage III B standards for CO, HC, NOx and PM. The engine out NOx emission is under the limit with a reasonable engineering margin. HC, CO and PM criteria pollutants are far below the regulatory limits.

Fig. 12.

Eight mode emission results for a 9 l non-road engine at 8000 h

Eight mode emission results for a 9 l non-road engine at 8000 h

Ash Residues

A DPF traps not only engine out soot particles, but also metal containing particles in the form of ash residues. Ash accumulation on a DPF is primarily due to engine oil consumption. Engine oils with a maximum of 1% sulfated ash are required for Interim Tier 4 engines. Ash accumulation on a DPF can be estimated by the oil consumption and an empirically measured ash trapping efficiency (6).

The impact of ash loading on the DPF pressure drop was calculated using an in-house model based on the method published by Konstandopoulos (7). The model was first calibrated using production DPF hardware. The results, shown in Figure 13, assume the use of CJ-4 oil with an ash content of 1% and an empirical ash retaining efficiency for the DPF of 60%. The ash loading on the DPF increased over time, leading to a higher pressure drop. The solid blue line represents the DPF pressure drop at a soot loading of 3 g l−1 at rated power with the maximum exhaust flow rate and the highest normal operating temperature. The dotted blue line represents a soot loading of 0 g l−1 at rated power. The green lines represent the DPF pressure drops at an average exhaust flow rate and an average exhaust temperature calculated from a NRTC test.

Fig. 13.

Calculated DPF pressure drop over time with and without soot

Calculated DPF pressure drop over time with and without soot

These results illustrate low average DPF pressure drops although the instantaneous DPF pressure drop could spike to high values when engine exhaust flow rates suddenly increased. This high pressure drop condition disappeared over time if the engine was operated near peak power. The DPF pressure drop returned to the dotted blue line over time due to passive regenerations.

Field data have shown the real world ‘apparent’ ash trapping efficiency of the DPF is approximately half of the intial 60% assumption. A number of hypotheses could explain this observation: (a) engine oil sulfated ash content may be less than the specification limit of 1%; (b) not all consumed oil may be converted into sulfated ash and transported to the DPF; and (c) sulfated ash may decompose to metal oxides of lower mass during active regenerations. In practice, the ash cleaning interval is expected to be much longer than the initial assessment.

Conclusion

Cooled EGR, DOC and DPF are proven technologies for meeting the US Interim Tier 4 and EU Stage III B emission control standards for non-road diesel applications. High trapping efficiency wall flow filters enable flexibility in engine design, broad engine applications and wide operating windows. The platinum-palladium based DOC is cost effective and robust and provides the benefit of passive regenerations through NO2 and soot reactions. The DOC oxidises HC and the soluble organic fraction of PM and heats the exhaust gas for active DPF regenerations under a wide range of exhaust flow, O2 level and inlet temperature conditions. The robust HC performance and thermal inertia of a DOC are beneficial for precise control of the DPF inlet temperature for active regenerations.

For non-road applications, passive soot regeneration occurred extensively in the DOC-DPF system. The aftertreament control alogrithm within the engine management system was designed to take advantage of this. The DOC-DPF system is less complex than the burner-DPF alternative. A key enabler was a new engine exhaust temperature management mode to ensure exhaust gas temperatures are above the DOC light-off temperature. Active regenerations are recommended for wall flow DPF applications to provide a reliable and robust system for diversified non-road applications. Uniform HC distributions and precise DPF inlet temperature controls are critical for reliable active DPF regenerations. Additional vehicle level integrations are required to effectively manage the DOC-DPF converter skin and exit gas temperatures. Overall, the EGR and DOC-DPF solution offers the best in class engine and emission performance as well as being cost effective.

Acknowledgements

The author wants to thank Dr A. Triana, A. Flores, R. Iverson, E. R. Snyder, Dr A. Kozlov, Dr P. Ayyappan, Dr T. Harris, W. Gavin, D. Anderson and Dr X. Gui from Deere and Company for their contributions to this paper.

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References

  1.  X. Gui, D. Dou and R. Winsor, ‘Non-Road Diesel Emissions and Technology Options for Meeting Them’, 2010 Agricultural Equipment Technology Conference, Orlando, Florida, USA, 10th–13th January, 2010, American Society of Agricultural and Biological Engineers, St. Joseph, Michigan, USA, 2010, pp. 1–24
  2.  F. Conicella, ‘Low Particulate Combustion Development of a Medium Duty Engine for Off-Highway Applications’, Heavy Duty-, On-/Off-Highway Engines, MTZ-Konferenz, Friedrichshafen, Germany, 17th–18th November, 2009
  3.  H. Bülte, H.-J. Schiffgens, P. Broll and S. Schraml, ‘Exhaust Aftertreatment Concepts for Engines in Mobile Machinery According the Legislation of US Tier 4 and EU Step IV. Technologies and Applications’, 18th Aachen Colloquium “Automobile and Engine Technology”, Aachen, Germany, 5th–7th October, 2009
  4.  R. Allansson, P. G. Blakeman, B. J. Cooper, H. Hess, P. J. Silcock and A. P. Walker, ‘Optimising the Low Temperature Performance and Regeneration Efficiency of the Continuously Regenerating Diesel Particulate Filter (CR-DPF) System’, SAE Paper 2002-01-0428, SAE World Congress and Exhibition, Detroit, MI, USA, 2002 LINK http://dx.doi.org/10.4271/2002-01-0428
  5.  N. Khadiya, ‘Exhaust Thermal Management Using Fuel Burners’, 3rd International Conference, Vehicle Emission Reduction Technologies – Criteria Pollutants and CO2, Car Training Institute (CTI), Detroit, USA, 16th–20th May, 2011
  6.  W. A. Givens, W. H. Buck, A. Jackson, A. Kaldor, A. Hertzberg, W. Moehrmann, S. Mueller-Lunz, N. Pelz and G. Wenninger, ‘Lube Formulation Effects on Transfer of Elements to Exhaust After-Treatment System Components’, SAE Paper 2003-01-3109, SAE Powertrain & Fluid Systems Conference & Exhibition, Pittsburgh, PA, USA, October, 2003 LINK http://dx.doi.org/10.4271/2003-01-3109
  7.  A. G. Konstandopoulos, E. Skaperdas and M. Masoudi, ‘Microstructural Properties of Soot Deposits in Diesel Particulate Traps’, SAE Paper 2002-01-1015, SAE World Congress and Exhibition, Detroit, MI, USA, March, 2002 LINK http://dx.doi.org/10.4271/2002-01-1015

The Author

Danan Dou received his PhD in Chemistry in 1992. He worked at Delphi Catalysts, USA, for eleven years before joining John Deere Power Systems in 2006. Currently, he is the manager for advanced power systems engineering, responsible for powertrain innovation, advanced engineering, engine fluids and aftertreatment innovation.

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