Advance Science. Applied Technology

Ultra-Low NOx Diesel Program Update

Thomas ReinhartSeptember 13, 2018

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Outline Current status of US on-highway engines

CARB’s future regulatory plans

CARB project goals:– Demonstrate feasibility of a 0.02 g/hp-hr NOx standard– Determine engine calibration changes and aftertreatment hardware /

controls changes required to achieve ultra-low NOx– Create a low load / low exhaust temperature test cycle to cover

operation in congested urban environments– Demonstrate ability to maintain NOx control under low temp conditions– Explore potential metrics for a low temperature test cycle

Progress update on Stage 1, 2, and 3 CARB projects2

Current US On Highway HD Regulations GHG Phase 2 Regulations

– For Line Haul engines, additional 5 % GHG reduction from 2017 levels by 2027 (phased in over10-year period)

– More emphasis on vehicle efficiency / CO2 reductions– N2O cap still at 0.1 g/hp-hr (no change from previous)

OBD current thresholds– NOx = 0.4 g/hp-hr for NOx catalyst, 2016+– PM = 0.03 g/hp-hr (requires PM sensor), 2016+– No plan for further threshold reductions yet...– Natural Gas engines in 2018+

Urea Quality sensors effectively required 2017+

Typical US 2013+ On-Highway Heavy-Duty Diesel Architecture

Typical Engine‐out EmissionsNOx ~ 3 g/hp‐hr FTP and SETPM   < 0.08 g/hp‐hr FTP (hot)

< 0.04 g/hp‐hr SET

Lower NOx Standard? (i.e., 0.02 g/hp-hr) CARB has re-stated desire for 0.02 g/hp-hr by 2031 to

meet air quality targets– May be phased-in with 0.05 g/hp-hr as interim earlier (2024 ?)– Nothing finalized yet (still open)

ARB Low NOx Demonstration Program under way at SwRI (since October 2013)– Stage 1 completed early 2017 (reported)– Stage 2 (2018 results) and Stage 3 (2019 results) work underway

CARB Rulemaking will start in 2019– OBD thresholds may not move initially

Stage 1 CARB Project (Complete) Demonstrate 0.02 g/hp-hr NOx on current production engines

– Cummins ISX-12G natural gas engine– Volvo D13 turbocompound diesel

Determine aftertreatment hardware and controls required

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Stage 1: 0.2g/hp-hr vs. 0.02 g/hp-hr

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Cold‐FTP Hot‐FTPAftertreatment NOX Conversion Efficiency, %

Test ConfigFTP Transient

RMC‐SET WHTCCold Hot Composite

Baseline 75% 98.5% 95% 97% 97%Devel Aged 98% 99.7% 99.5% 99.3% 99.4%Final Aged 96% 99.3% 98.8% 98.2% 98.8%

SAE 2017‐01‐0958

Stage 1 Diesel Calibration Approach – Cold-Start

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Increased  Exhaust Temperatures

Decreased Engine‐Out NOX

• Modified calibration for cold start – lower engine‐out NOx and higher exhaust temp.

• EGR changes, multiple injections, intake throttling, increased idle speed.

• ~Standard cal after 600 secondsGHG Impact – +2.5% cold‐start, minimal on hot‐start, +0.4% overall

Stage 1 - Final ARB Low NOX Configuration

• All catalysts are coated on 13” diameter substrates• SCRF is 13” X 12” on high porosity filter substrate• Remaining catalysts are 13” X 6” on “thin wall, low thermal mass substrates”• All sensors shown are production-type

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NOX Levels with Development Aged Parts, g/hp‐hr

Cold‐FTP Hot‐FTP Composite RMC‐SET

Engine‐Out 2.8 3.0 3.0 2.1

Tailpipe 0.06 0.008 0.016 0.015

Stage 2 Program Scope Stage 2 Program focus is Low-temperature and Low Load (urban)

Vocational duty cycles– Stage 1 test article

Key Topics:– Development of Low-Load duty cycle profiles

• Development of a Heavy-Duty Low Load Cycle (LLC)– Re-calibration of Stage 1 ARB Diesel Demonstration Engine to

achieve low NOx on Low Load profiles• What is the impact on GHG for this kind of control ?

– What are appropriate load metrics for in-use testing at Low Load?• accuracy of potential low load metrics

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Low Load Operation –Three Basic Emission Control Challenges High Load-to-Low Load Transition

– Drive to work-site then lower load work or idle period– How long can system maintain performance and manage heat during prolonged cool-off?

Sustained Low Load– Repeating short light load operation separated by idle (delivery, refuse, transit bus, drayage)– Can system maintain heat levels long-term?

Low Load-to-High Load Transition– Long downhill grade, followed by uphill (Tractor)– Transition to highway work after a long time at idle– Can the system handle a sudden increase of load after cooling off?

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A good Low Load Cycle will test all three of these challenges

Stage 2: Low Load Cycle – Draft Example

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0 500 1000 1500 2000 2500 3000 3500 4000 4500

Norm

alize

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Speed‐norm Torque‐norm

High-Low - Sustained Low - Low-High Assume preconditioning like 1 hot-FTP for warmup Shorter than current RMC-SET test with preconditioning... Enough transition time from High-Low to Sustained Low?

Stage 2 Next Steps Complete translation of Low Load profiles to normalized Engine Cycles

– GEM model used as base tool for this - COMPLETED

Re-calibrate Stage 1 engine & aftertreatment system to achieve high conversion on Low Load profiles– NOX potential and GHG impact

Complete Low Load Cycle (LLC) development

Demonstrate final re-calibrated system on Regulatory and Load Low cycles– Using Stage 1b aged aftertreatment parts

Complete generation and analysis of Low Load metric data

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Stage 3 Scope for 2019 Examine Low NOX on a platform

that is more representative of broader market in 2017+– Production 2017 Cummins X15– Is a less complicated system feasible for

the broader industry?– Is a lower GHG impact apparent without

turbocompound?

Integrate both Regulatory and Low Load Cycles at the start– Program targets are 0.02 g/hp-hr on

regulatory cycles and NOx control on Low Load cycles

– Look at both engine and aftertreatment

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Production Aftertreatment (will be replaced)

Production Engine

Stage 3 2017 Cummins X15 Baseline Data

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NOX Conversion: Cold = 86%, Hot = 94%, RMC-SET = 95% N2O ~ 0.06 g/hp-hr

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Cold Hot Composite RMC‐SET

Tailp

ipe BSN

OX, g

/hp‐hr

Engine‐Out Tailpipe Engine‐Out TailpipeHC 0.113 0.003 0.045 0.002CO 0.543 0.022 0.197 0.008NOx 2.317 0.159 2.931 0.138PM 0.088 0.002 0.032 0.001CO2

FTP, g/hp‐hr RMC, g/hp‐hr

504 445

Pollutant

SwRI’s measured CO2 values are slightly better than Cummins’ official cert values

Other Potential Aftertreatment Concepts for 0.02 g/hp-hr

Heated DEF ? PNA durability ? (upstream DOC layer for protection ?) DOC exotherm to help downstream SCR light-off ?

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PN

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SC

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AS

CSCRF

DO

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= NOX Sensor = DEF Dosing = NH3 Sensor

SC

R

AS

CDPF (SCRF?)LO

-S

CR

DO

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Heated DEF upstream and/or downstream ? Can downstream SCR reach light-off fast enough or is SCRF needed ? DOC exotherm to help downstream SCR light-off ? LO-SCR desulfation ?

Conclusions1. Stage 1 results show that 0.02 g/hp-hr NOx can be achieved

on the current test cyclesa) Modest GHG penaltyb) Complex and expensive aftertreatment

2. Stage 2 is focused on developing a low temperature test cyclea) Essential to cover a large portion of urban operationb) GHG impact, complexity, and metrics are TBD

3. Stage 3 will focus on reduced system complexity & CO2impact to achieve low NOx on both current cycles and low temperature cycles

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