Tier 4 Interim Aftertreatment Overview. Dave Dixon October 13, 2008

Transcription

1 Tier 4 Interim Aftertreatment Overview Dave Dixon October 13, 2008

2 What is Aftertreatment? Tier 4 Interim Aftertreatment System that chemically alters engine exhaust before releasing to the environment Tier 4 interim aftertreatment consists of Catalyst (DOC) and Filter (DPF) Entire assembly is typically called a DPF within Cummins Official name is Cummins Particulate Filter) Filter collects PM DOC needed to create heat for regeneration of filter Why do we need it? Tier 4 EPA particulate limits are 90% less than Tier 3 standard. In-Cylinder technology not capable of meeting Tier 4 standard, aftertreatment is required What is Regeneration? Process of cleaning out soot in the filter Since the filter is collecting soot (PM) during normal operation, it must periodically be cleaned out. It can only hold so much soot. During Regen, soot is converted to CO2 (rather than particulate matter) How do we control it? ECM has algorithms to estimate soot model based estimate and dp estimate When active regeneration needed, ECM will dose hydrocarbon to heat the filter to clean it out Cummins Confidential - Secret 2

3 Tier 4 Interim System Architecture Diagram Engine In-Cylinder HC Dosing Turbo Outlet Diesel Oxidation Catalyst Catalyzed Soot Filter T3 Thermistor T1, T2 Thermistors Dual P Sensor Integrated Sensor Table Machine OEM Harness Engine ECM Software Cummins Confidential - Secret 3

4 Diesel Oxidation Catalyst flow through catalyst mature technology used on our engines for several years transit bus DCx ( 94 97, ) ISC/L ( 05 06) All 2007 automotive products (part of CPF system) Very high hydrocarbon reduction due to precious metal washcoat NO NO 2 conversion allows for soot reduction in filter (passive regeneration) Cummins Confidential - Secret 4

5 wall flow catalyst Catalyzed Soot Filter carbon trapped on wall of inlet cells 90+% dry particulate filtering efficiency precious metal oxidizes NO to NO 2 supporting soot regeneration, also oxidizes HC and CO two carbon regeneration mechanisms 250 o 450 o C reaction: NO 2 + C NO + CO o C reaction: C CO 2 concerns excessive soot loading if insufficient regeneration opportunities excess loading causes very rapid reaction rates, destroying filter Cummins Confidential - Secret 5

6 Tier 4 MR Horizontal EIEO CPF End Inlet/End Outlet T-Bolt Orientation: (-45 ) Sensor Location: 35 Lift Hooks Clocking: 0 inlet and outlet 35 Cummins Confidential - Secret 6

7 Tier 4 MR Horizontal SISO CPF Inlet Clocking A: 0, 270, 180, 90 A Outlet Clocking: 0 T-Bolt Orientation: (-45 ) Sensor Location: 35 Lift Hooks Clocking: 0 inlet and outlet 35 Cummins Confidential - Secret 7

8 Tier 4 MR Horizontal EISO CPF Outlet Clocking: 0 T-Bolt Orientation: (-45 ) Sensor Location: 35 Lift Hooks Clocking: 0 inlet and outlet 35 Cummins Confidential - Secret 8

9 Tier 4 MR Horizontal SIEO CPF Inlet Clocking A: 0, 270, 180, 90 T-Bolt Orientation: (-45 ) Sensor Location: 35 Lift Hooks Clocking: 0 inlet and outlet A 35 Cummins Confidential - Secret 9

10 Tier 4 MR Vertical EIEO CPF End Inlet/Vertical End Outlet T-Bolt Orientation: (-45 ) Lift Hooks Clocking: Located on outlet Cummins Confidential - Secret 10

11 Tier 4 MR Vertical SIEO CPF Inlet Clocking A: 0, 270, 180, 90 T-Bolt Orientation: (-45 ) Sensor Location: 35 Lift Hooks Clocking: Located on outlet A 35 Sensor tray detail Cummins Confidential - Secret 11

12 Passive Regeneration NO2 Based Oxidation Equation (aka Noxidation ) May 10, 2006 Greg Hertle Source: DeSoot Presentation from A. Suresh, A. Yezerets, N. Currier & B. Epling 12/02/04 Cummins Confidential - Secret 12

13 Active Regeneration O2 Based Oxidation Equation Source: DeSoot Presentation from A. Suresh, A. Yezerets, N. Currier & B. Epling 12/02/04 Cummins Confidential - Secret 13

14 3 2.5 Combined Effects of Passive and Active regenerations 100% Total Oxidation Rate (g/min) 90% NO2 Oxidation g/min - passive regen 80% O2 Oxidation g/min - active regen soot oxidation rate, g/min NO to NO2 Conversion [ratio] 70% 60% 50% 40% 30% NO to NO2 Conversion % 10% Temp [C] 0% Cummins Confidential - Secret 14

15 Combined Effects of Passive and Active regenerations Larger view of oxidation reaction Total Oxidation Rate (g/min) NO2 Oxidation g/min - passive regen soot oxidation rate, g/min O2 Oxidation g/min - active regen Temp [C] Cummins Confidential - Secret 15

16 DPF Regeneration Strategy Passive Regen Occurs naturally above 300C DPF bed temperature Active Regen Change Duty-Cycle Available if Passive fails to maintain low soot loading in the DPF. Requires DOC inlet temps of 250C Non-mission (parked) Regen Remove & Clean DPF lamp is on. Operator initiated soot cleaning option. Machine should be out of mission. Changing to a more aggressive duty cycle (higher load factor) can also be attempted. Severe derate and Red Stop Engine lamp - vehicle needs to be taken to distributor or depot for DPF cleaning. Cummins Confidential - Secret 16

17 Soot Load Estimators DPSLE Delta Pressure Soot Load Estimate Pressure Differential Based Estimate Direct measurement of pressure drop due to soot in DPF Requires minimum exhaust flow rate for accuracy, inaccurate at low flows Susceptible to effects of ash on high hour parts 4500hr minimum ash cleaning interval MBSLR Mass Based Soot Load Rate Engine out emissions and chemistry/kinetic based model Total soot loading rate = Engine particulates (low temp Noxidation rate) (high temp oxidation rate) Combined Soot Load Estimate weighted combination of DPSLE & MBSLR Weighting (or trust ) is dependant on engine conditions Low exhaust flow = tend to trust MBSLR High exhaust flow = tend to trust DPSLE Cummins Confidential - Secret 17

18 DPF Lamp Logic ENGINE DERATE Light Severe STOP Engine Check Engine Off Off On On Off Existing Lamps HEST Lamp DPF Lamp Off Off In-mission: Configurable with dosing and/or temperature Non-mission: On with initiation command On-Solid Flashing Off Off New Lamps Passive Regeneration Stationary/Mobile Active Stationary Only Service Only Empty Auto Low Medium High Stop Increasing Soot Load Increasing Soot Load Cummins Confidential - Secret 18

19 What is In-cylinder Dosing? Purpose Add heat to the exhaust gas Provide HC for additional heat through oxidation by the DOC Methods HD Engines - External doser, injects fuel directly into the exhaust system MR Engines - In-Cylinder dosing, uses the common rail fuel system to inject fuel at different times in the cycle to generate heat and provide HC Main Event Early Pilot Pilot Post Late Post TDC BDC Cummins Confidential - Secret 19

20 2007 Mobile Regen example Temperature (C) Engine Speed (RPM) ECM run time DOC inlet temp DOC outlet temp DPF outlet temp Regeneration temperature target Engine_Speed Cummins Confidential - Secret 20

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23 Tier 3 Muffler Temperature Example A Tier 3 muffler (designed for feller buncher application with 215 hp QSC engine 1/8 thick insulation) **All Temperatures are in Degrees Celsius** Max Temp: C Cummins Confidential - Secret 23

24 Tier 3 Muffler Temperature Example 28061N Tier 3 muffler (designed for feller buncher application with 215 hp QSC engine ½ thick insulation **All Temperatures are in Degrees Celsius** 1 Test Point 2 (C ) 207 Ambient = 20 C Cummins Confidential - Secret 24

25 Tier 4 Insulation Example FLOW Outlet Filter SISO with Fabric encapsulated Insulation under body joint & outlets (~18 mm nominal thickness ) (inlet section not shown) See AEB for details Cummins Confidential - Secret 25