# Presentation: 477265

## EPA Clean Diesel Engine Implementation Workshop

- Shirish Shimpi
- Cummins Inc.
- August 6-7, 2003

**Heavy Duty On-Highway Diesel Engine Certification Test Procedure Issues at the 2007- 2010 Emissions Levels**

**Shirish A. Shimpi**
**Cummins Inc.**
**Chairman EMA Calibration Standards Task Force**

## EPA Heavy Duty On-Highway Engine Emissions Standards

- 		  		NOx	         PM         NMHC
- 				g/bhp-hr	g/bhp-hr	g/bhp-hr
- (Phase-in)
- 2007-2009       ~1.2		0.01	      ~ 0.10
- (Final)
- 2010-2012	 0.2		0.01		 0.14
- Includes blow-by emissions

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## EPA Heavy-Duty Engine Emission Standards

- PM

- EPA Heavy-Duty Engine Emission Standards

- Steady State
- Test

- NOx + HC

- Transient Test

- NOx
- (Unregulated)

- PM (Unregulated)

- NOx

- NOx + HC

- NOx

- PM

- Urban Bus PM

- NOx + HC

- NOx

- 3

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## Engine Certification Test Requirements

- Prior to the Consent Decree only the Transient cycle sequence was required for emissions certification
- Only one emissions certification hurdle
- More complex requirements now and in the future
- Transient cycle sequence
- 13 mode steady-state Supplemental Emissions Tests (SET) with mystery points
- Not To Exceed (NTE) zone
- Multiple emissions certification hurdles
- A challenge even at today’s levels, more challenging in the future

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## Emissions Certification Procedures

- Major measurement techniques have remained the same in spite of the significant reduction in emissions standards.
- Fundamentally they are very similar to the techniques developed when transient emissions regulations were introduced in the 1980’s
- All the engine exhaust is diluted using a Constant Volume Sampling (CVS) system
- Gaseous emissions are sampled from the dilution tunnel and the concentrations are measured by continuous gaseous analyzers
- Particulate emissions are sampled from the dilution tunnel and are diluted once again before being collected on a particulate filter.  The weight difference of this filter before and after the particulate collection is used in determining particulate emissions

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## EPA/EMA Collaborative Effort

- Much effort has been taken to introduce improvements to these techniques to enable emissions determination at the future emissions levels
- EPA and EMA have jointly worked to improve these techniques but much work still needs to be done
- No major breakthroughs have surfaced - incremental improvements have been achieved
- Largest gains have come from specifying tighter controls in the measurement procedure and in using more capable instruments
- Research activity on improving emissions measurement is continuing

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## Emissions Variability is a Key Issue

- It is not enough to reduce emissions levels from the engine and aftertreatment device.
- As emissions levels are reduced there is increased emissions measurement variability.
- Variability in the measurement of emissions components  based upon the prescribed procedure has to be low.
- Increased measurement variability adds cost and time to all aspects of engine design and testing.

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## EPA/EMA goal = 2.5% COV   2 tests required

**EPA/EMA goal = 2.5% COV   2 tests required**

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## PM - New Challenges

- At 2007 levels, PM will be nearly all semi-volatile aerosols with very little carbon.
- We now know that the formation of these aerosols is highly path dependent - i.e. how exhaust is cooled and diluted.
- This is expected to cause high variability, especially between different test sites.
- EPA’s research efforts at SwRI and the new CRC E-66 project on 2007 PM measurement research will help improve measurement issues and reduce variability.

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## NOx and HC - New Challenges

- Current technology NOx and HC analyzers cannot meet the new accuracy specification and the wide dynamic concentration range expected in the future.
- This will drive us to the “**Heated Bag**” option to average the sample concentration and use low range analyzers to read the bags.
- However, there are no suppliers of heated bag sampling systems.  These systems must be developed.

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## Summary

- The 2007-10 emissions standards represent a significant technological challenge:
**a ten fold reduction in NOx and PM****.**
- EMA and EPA have been working cooperatively in making a similar effort in reducing variability.
- Although improvements have been made, variability has not been reduced as much as it is needed.
- It does not look like we are close yet.
- The increased time for engine development is going to compound the difficulty in meeting the standards.

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## Background Informationon Changes in the 2007 Procedures

## General Changes

- Added a 3rd CVS type based on a subsonic venturi (SSV) for more flexibility in setting CVS flow
- Added allowance for averaging samples from multiple instruments - lowers the instrument component of total variability by 1/sqrt(n) at the cost of duplicating instruments.  Does not help variability due to other factors
- Added rules for considering alternate measurement techniques.

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## PM Related Changes

- Lowered balance precision - from 20 to 2.5 μg
- Added a preclassifier to reject large particles that are not part of engine exhaust
- Added lower limit on PM sample temperature - _from_ 125 °F (51.7 °C) max _to_ 47±5 °C (107.6 to 125.6 °F)
- Added specifications for primary and dilution air filtering
- Reduced size, number and specifications for filter media - _from_ 70 mm, double, fluorocarbon-coated glass fiber or membrane filters _to_ 47 mm single, Teflon coated borosilicate glass fiber high efficiency filter (TX40) or Teflon membrane filter (Teflo)
- Standardized filter holder (based on ambient PM samplers)

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## PM Related Changes

- Tighter tolerances on weigh room T & H - from 22±3 °C & 9.4±3 °C dew point & 45±8 % RH to 22±1 °C & 9.5±1 °C dew point
- Recommended Class 1000 clean room specifications
- Added buoyancy correction
- Reduced reference filter drift limit from ±40 to ±10 μg
- Added requirement for static neutralizers and grounded tweezers
- Added allowance to take multiple weights and use mean
- Lowered lower limit on primary and secondary dilution air temp from 20 °C (30 °C max) to 15 °C min (no upper limit)
- Lowered minimum conditioning time from 60 to 30 min
- Preconditioning of the entire sampling system

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## NOx Related Changes

- Tighter specification for continuous analyzers - _from_ ± 2% of point down to approximately 4% of Full Scale (FS) (or ±0.08% of FS) _to_ 2% of point down to 1/2 of the average concentration that would yield a BS emissions value equal to the standard.  On a ppm basis this is equivalent to going _from_ a current specification of ±0.28 ppm (based on a 350 ppm FS) _to_ ±0.015 ppm needed at the 2007 levels.  That’s 19 times more accurate!
- Added specifications and check for NOx analyzer interference from CO2 and H2O.
- Added allowance for bag sampling (must be heated to prevent condensation)

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