Non-volatile Particulate Matter Measurement Methodology for Aero-Engines 10th January 2014, MMU, Manchester Mark Johnson Rolls-Royce Emissions Measurement Expert SAE AIR6241 document sponsor & Sampling Team lead

FORUM-AE

Aircraft Emission Measurement Certification

Methodology Process

SAE-E31 committee members include: engine manufacturers, scientists –

academic/research institutes, regulators

Aerospace Information Report (AIR)

Information report written in the style of an ARP by a small number of

committee members

Review and ballot before published

Aerospace Recommended Practice (ARP)

Comprehensive report written as an industry standard with input from all

members

Review and ballot before published

CAEP (Committee on Aviation Environmental Protection) Relevant Country members

with additional observers including: regulators, NGO’s, engine manufacturers

Steering Group (specifically WG3) adopts SAE-E31 methodology for

aircraft engine certification

ICAO (International Civil Aircraft Organisation) Government members

ICAO adopts CAEP recommendations and published in Annex 16

Existing Aircraft Particulate Emissions Measurement

Standard Method - Smoke

Visibility – Smoke Number

SAE Smoke Number method determined over 50 years ago based on reflectance of smoke stained filters

Cleaning Mechanisms

• Dissolution / leaching of soluble matter in

the humid environment of the respiratory

system.

• Physical translocation of non-volatile,

insoluble particulate matter.

• Removal from alveolar region by

interaction with macrophages -inefficient

for particles < 80 nm.

Majority of current

technology gas turbine

(combustion exit)

particles fall in this

range)

PM driver: Local Air Quality – Human health impact • The smaller the particle the deeper it

enters the human body

• Ultrafine particles have a strong

impact on human health

• Ultrafine particles are under-

represented in mass-based metrics

• Key property is the particle surface

area.

• Interaction mechanisms are not yet

understood.

SAE-E31 committee originally tasked with: Define and develop a robust repeatable mass measurement methodology for volatile mass*, non-volatile particle mass and number for use at the exit plane of jet turbine exhaust engines. The method will include sample acquisition, transport/conduction, analysis and computations required to provide the desired parameters.

*Note: It is current belief that volatile combustion generated particles do not

exist at the engine exit. They form only in sampling lines and/or downstream of

engine Particle distribution from a combustion source consists of

• Non-volatile primary and agglomerate particles

(solid carbon/smoke)

And

• Volatile (condensation) particles

(hydrocarbons and sulfate)

The fraction of volatiles present, depends upon

temperature, dilution and residence time of the plume

Distinction between nonvolatile and volatile particle types is a

critical task in the measurement of particles in aircraft engine

exhaust

Temperature threshold separating volatile organics from nonvolatile matter is set

(by SAE E31) at 350 °C

Elemental Carbon (EC) - All carbon products >350 °C and therefore considered to be

equivalent to ‘Non-volatile matter’.

Organic Carbon (OC) – All carbon-based particle products produced by condensation

and chemical reaction downstream of the exit of an aircraft gas turbine engine.

However, it should be noted that the exact definition of organic carbon depends on

the applied measurement technique… Part of the volatile fraction

Volatile fraction – Material that is vapor phase at release conditions (In gaseous form

known as volatile precursors), but which condenses and/or reacts upon cooling and

dilution in the ambient air to form solid or liquid particulate matter after discharge.

The distribution between organic carbon (OC) and EC depends on the operating

conditions of the engine. The respective fractions may vary between 10% EC and

90% OC at idle conditions to approximately 100% EC at take-off thrust conditions.

E31 PM ARP Milestones & Campaigns (i)

AIR6037 (Aircraft nvPM

method development)

published

SAMPLE I

APEX 2

AAFEX

Interim

JSF

Task E31 for an ARP for total mass by 2010

Joint regulator letter to E31 May 2008

AIR5892 (nvPM

measurement techniques)

published

EASA Letter to E31 Aug 2007

Suggestion of nonvolatile mass ARP by 2010

SAMPLE II

APEX 3

Between regulators and SAE E31

Face-to-face meeting Oct 2008

Regulators become E31 members

EPA

testing

Task E31 for Non-volatile PM ARP by end of 2011

Joint regulator presentation Nov 2009

MS&T

lab

testing

OEM

testing

E31 PM ARP Milestones & Campaigns (ii)

nvPM AIR6241 ballotted CAEP 9 meeting

Feb 2013 Draft PM ARP methodology

delivered to CAEP

nvPM ARP ballotted

CAEP 10 meeting

Feb 2016 WG3 Deliver

PM standard to CAEP

SAMPLE

III.1

AAFEX

2 FOCA

Zurich

EPA

testing

SAMPLE

III.2

MS&T

Zurich

Mermose

APRIDE

4

EPA

testing

APRIDE

5

SAMPLE

III.5 MS&T

vs OEM

AIR6241 published in November 2013

Plus 12 Appendices:

Excel calculators – PM EI, Sampling system Transport Performance (simple &

complex)

Standard Operating Procedures – mass instrumentation/calibration

Volatile Removal Efficiency methodology

Mass Measurement Techniques (not sensitive to volatiles)

Laser Induced Incandescence (Artium) Photoacoustic (AVL)

Filter absorption (Thermo)

Secondary traceable transfer calibration via

filter burn-off NIOSH 5040 using diffusion

flame (>80% EC)

Mass Instrument Specifications (note mass measurement obtained after a minimum 8x dilution factor)

Performance specification Value

Range 1 mg/m3

Resolution 1 µg/m3

Repeatability 10 µg/m3

Zero drift 10 µg/m3/hr

Linearity 15 µg /m3

Limit of detection (LOD) 3 µg/m3

Rise time 2 sec

Sample rate 1 Hz

Accuracy -

Agreement with EC determined by NIOSH

5040 (at 15 ± 5 µg/cm2 EC loading)

0.90 ≤ slope ≤ 1.10

Number Measurement Technique

Need to remove volatiles... Condensation Particle Counter

Volatile Particle Removal:

• Achieve >99.9% removal of 15 nm and 30 nm tetracontane

(CH3(CH2)38CH3) particles with an inlet concentration of ≥10,000

particles/cm3 and ≥50,000 particles/cm3 respectively.

Condensation Particle Counter:

• Adhere to ISO27891 recommendations

• Use reagent grade n-butanol as working fluid

• Operate under full flow operating conditions (flow splitting inside the CPC

is not allowed)

• single count mode only with upto 10% coincidence correction

• Linearity 0.90 ≤ slope ≤ 1.10

• Have counting efficiency of ≥50% at 10 nm and ≥90% at 15 nm

electrical mobility diameter respectively, using an emery oil aerosol or

equivalent

Note that number measurements are NOT corrected for particle loss in the

VPR (different to PMP). However, particle penetration measurement

through VPR is required for sampling system transport performance, with

minimum specifications of 30%, 55%, 65% & 70% at 15, 30, 50 & 100nm

respectively.

Number Measurement Specifications

Difficulties in Aircraft large engine sampling.....

Aircraft engine sampling

systems are much longer than

automotive due to:

- Harsh (vibration and

temperature) environment

close to large engines

- Complex probes for exhaust

representativeness

Results in sampling line lengths

>25m and therefore significant

particle loss

nvPM Measurement

system

Thick Te

stbe

d W

all

AIR6241 Sampling Methodology

Sampling System Particle loss mechanisms

Sampling System Particle Transport

Penetration calculation at 15, 30, 50 & 100nm

Multiple Systems

Sampling System Particle Transport performance

example

nvPM Number measurement – CPC lower size cut-off

Single component efficiencies:

Sampling + detection system efficiency

nvPM Measurement Uncertainties

nvPM Number – similar methodology to PMP thus similar uncertainties (~17 to

20%), plus sampling uncertainties below

nvPM Mass – theoretically (GUM) similar to number plus sampling

uncertainties. Need more confidence due to lack of long term/multiple

instrument/multi lab data (only one campaign so far)

Sampling – Particle losses

– system standardised as far as possible to reduce differences in particle loss

between systems

- Ongoing measurements of long term drift on sample loss

Experiment comparisons ongoing/planned to understand reproducibility

(number/mass plus sampling) between reference and OEM systems

SAE E31 are developing an assumption-based theoretical methodology for

correcting particle loss (no measurement of size distribution). It is currently

unknown what the impact of uncertainty due to this methodology is similar to

the measurement uncertainty above.

nvPM ARP roadmap (if funding available)

AIR6241

ballotted

Reference systems

comparison

Permanent vs mobile

2012 DWD compliant

validation/

robustness testing

SAMPLE

III.2 MS&T

2013 2014

MS&T

12 months

Intercomparison (Mobile Reference vs engine

manufacturers)

Round-robin testing

SAMPLE

III.3

MST

Ballot

ARP

A-PRIDE 3 A-PRIDE 4

A-PRIDE 5

Single / multi system testing – Dilution factor sensitivity, Dilutor1

low inlet pressure, line loss drift

Possible delay

if: 1) technical

problems arise

2) OEM engine

availability

Engine Manufacturers perform robust system testing in

multiple locations/engine types

Mass

Initial Performance validation, calibration, QC checks

System repeatability / Uncertainty

SAMPLE

III.5

A-PRIDE 6

Particle loss correction methodology, uncertainty analysis

MERMOSE

Conclusions

• Huge milestone reached with publication of AIR6241, would not

have been possible without international collaboration involvement

• Further work is needed to prove the robustness and operability of

AIR6241 methodology (at engine manufacturers) to publish ARP

• Further work on the nvPM methodology uncertainty is required

(including comparison engine testing to assess reproducibility)

• Current E31 roadmap timeline is only possible if funding and engine

resource are available to test.

• Further development (and uncertainty) of sampling system particle

loss correction methodology required (but can be applied

retrospectively to nvPM AIR/ARP obtained data)