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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)