particulate emission measurements from aviation gas
TRANSCRIPT
Particulate Emission
Measurements from Aviation
Gas Turbine Engines 10th November, 2016 University of Birmingham, UK Mark Johnson Rolls-Royce Global Emissions Measurement Expert
Particle distribution from a combustion exhaust (typically <100nm diameter) consists of
• Non-volatile primary and agglomerate particles (solid carbon/smoke)
And
• Volatile (condensation) particles (hydrocarbons and sulfate)
Difference between non-volatiles and volatiles defined by temperature of 350degC.
Current belief - volatile combustion generated particles do not exist at the engine exit.
They form only in sampling lines and/or downstream of engine
TEM examples below (note Electro-mobility diameter shape difference)
Gas Turbine non volatile Particulate Matter (nvPM)
What are we trying to measure
Aerosol Society Meeting – Birmingham 10th November 2016
Cleaning Mechanisms
• Removal from alveolar region by
interaction with macrophages -inefficient
for particles < 80 nm.
Majority of gas
turbine
combustion
particles fall in
this size range
Aviation PM driver: LAQ – 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.
Aerosol Society Meeting – Birmingham 10th November 2016
Existing ICAO regulation - Smoke Number (visibility)
SAE Smoke Number method determined over 60 years ago
based on reflectance of smoke stained filters
Inaccurate at current technology smoke levels & no easy link to LAQ or
climate impact
ICAO/Regulators asked for nvPM mass and number
Aerosol Society Meeting – Birmingham 10th November 2016
Aviation GT nvPM Sampling & Measurement System
Development & experimental trials
2009- Official regulatory request to SAE E31 Accurate measurement of nvPM Mass & Number
2008-14 EASA SAMPLE Programme (€2.5m) Sampling system development - European reference system designed and
tested including several intercomparisons
2011- … APRIDE- SR Technics Zurich (€4m + €5m ) Swiss fixed reference system and sampling probe integrated to test cell –
numerous 2-way & 3-way inter-comparisons with other reference systems
2012- … PARTNER & ASCENT (€6m) North American reference system comparisons,
2013- … OEM Testing (€>10m) R-R, GE, HW, P&W & SNECMA, operability
2014-16 VARIAnT I&II (€1.3m) System Inter-comparisons & System Loss
2014-16 DG-MOVE (€1m) System Inter-comparisons
Aerosol Society Meeting – Birmingham 10th November 2016
6 6
Rolls-Royce data - In
Comparison of
2 x compliant
sampling
systems
System 1
System 2
Mass1
Mass2
Number 1
Size
Number 2
Example nvPM certification methodology test
at Zurich (2012)
ICAO / SAE regulation setup Annex 16 Vol II Appendix 7 / ARP6320 (2016)
10 systems now in operation worldwide (circa £500k to build/buy per system)
Aerosol Society Meeting – Birmingham 10th November 2016
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
Difficulties in Aero large engine sampling…
Aerosol Society Meeting – Birmingham 10th November 2016
Typical Aero gas turbine particle size distributions measured at end of sampling system, after particle loss
Aero gas turbine particle sizes range typically between 20 and
50nm and are significantly affected by size dependent particle
loss mechanisms
Aerosol Society Meeting – Birmingham 10th November 2016
Particle loss mechanisms
UTRC model (tool published in SAE AIR6241)
Aerosol Society Meeting – Birmingham 10th November 2016
Mass instrument
Number instrument
Volatile particle remover
Component loss defined by performance specifications
Diluter
Sample line loss defined by line geometry,
flowrate temperature & pressure
Component loss defined by calibration
measurements
Cyclone
Thermophoretic (assumed size independent) loss. Corrections for large
temperature gradient from sampling probe in hot exhaust (upto 600 °C
to Diluter at 160 °C
Size dependent particle line loss defined by line geometry, flowrate
(estimated), temperature & pressure
nvPM System loss locations
Aerosol Society Meeting – Birmingham 10th November 2016
Regulatory nvPM measurements - Sampling system standardised as far as possible
- Thermophoretic correction (not size dependent) are included in
regulatory EI measurements. Correction typically 0 (mixed flow probe) to
~30% (core flow probe)
LII300
But for Airport Inventories need reasonable estimates of ‘real’ engine exit nvPM emissions
to do so means correcting for all particle system loss
SAE AIR6504 To estimate the nvPM system loss correction factors, an estimation of nvPM
mass and number concentrations at the engine exhaust exit plane are
needed and a number of assumptions are required:
o Lognormality of nvPM size distribution at engine exit
o constant fixed effective density
o fixed geometric standard deviation (width of distribution)
o no coagulation in sampling system
Aerosol Society Meeting – Birmingham 10th November 2016
System Section 1 Sampling Probe
Practicality compromise to use existing Annex 16 compliant Gaseous probes
>12 spatial points, 80% pressure drop (tip dilution discounted as too complex)
Different engine manufacturers have vastly different compliant sampling probes
Theoretical penetration comparisons of 4 x engine manufacturer
probe (different designs) performed - Differences are within 5%
Aerosol Society Meeting – Birmingham 10th November 2016
nvPM system Sections 3 & 4 nvPM Transfer Line – long 25 m length plus cyclone & splitter
Ideally sampling chain as short as possible
(to minimise loss), practicality compromise
for large test cells (e.g. 14x14m)
Geometry/operation standardised to obtain
similar particle losses between
systems/testbeds/operators
Large (super micron) particles from random
shedding - affect mass measurement
10 μm particle has 125 millon times more mass
than 20 nm particle
Cyclone Sharp cut - 1μm
Aerosol Society Meeting – Birmingham 10th November 2016
Measurements vs theoretical size dependent penetration
of 25m line
LII300
SAMPLEIII.1 (2011) VARIAnT 2 (2016)
• Similar measurements also performed using lab soot on North American & Swiss reference nvPM systems
Aerosol Society Meeting – Birmingham 10th November 2016
Section 5
Measurement Section
Examples:
nvPM mass instrument (real-time):
AVL MSS 483 – photoacoustic technique
Artium LII-300 – laser induced incandescence technique
nvPM number instrument:
Dekati DEED+CS with CPC (Grimm 5.421, TSI 3775)
AVL APC advanced (TSI 3790E)
Aerosol Society Meeting – Birmingham 10th November 2016
Number Measurement Technique
CPC spec smaller than automotive, D90<15nm D50 <10nm
Need to remove volatiles...
Use Volatile Particle Remover (VPR)
upstream of CPC, consisting of
Evaporation tube & Catalytic Stripper
AND additional dilution to ensure
CPC in single count mode
Condensation Particle Counter
Aerosol Society Meeting – Birmingham 10th November 2016
VPR penetration curve fit
LII300
• As part of calibration VPR must meet minimum penetration specifications at 4 particle sizes
• As part of calibration CPC
must meet minimum efficiency specifications at 10 and 15 nm, of 0.9 & 0.5 respectively
Aerosol Society Meeting – Birmingham 10th November 2016
CPC lower size cut-off
efficiencies curve fit
15nm 30nm 50nm 100nm
≥0.3 ≥0.55 ≥0.65 ≥0.70
Example of Individual and Combined System loss
LII300
FORUM-AE Workshop – Amsterdam 15th April 2016
Iterative procedure for estimation of nvPM mass and
number concentrations corrected for nvPM sampling and
measurement nvPM loss:
estimate particle size distribution at engine exit
LII300
Some examples of nvPM system correction factors
LII300
APRIDE4
APRIDE5
Honeywell
P&W
SAMPLE III.5
VARIANT I & II
kSL_num Range: Average
2.0 to 3.6
2.3 to 6.0 4.15
3.6
4.6
2.1 to 5.5
3.8 to 9.0 5.5
kSL_mass Range : Average
1.2 to 1.4
1.1 to 1.2 1.1
1.5
1.3 1.4 to 1.6
1.3 to 1.9
1.5
fuels Jet A Jet A Jet A Jet A Jet A JetA,
camelina, and blends
nvPM number correction factors 2 to 9 nvPM mass correction factors 1.1 to 1.9
Aerosol Society Meeting – Birmingham 10th November 2016
Use of system loss corrections for Airport Inventories or
Possible future regulation
LII300
There is certainty that significant particle system losses occur for
aviation nvPM measurement
For airport inventories, knowledge of ‘real’ engine exit emissions is
needed – Using this correction methodology, these can be estimated.
But the uncertainty on these estimations could be larger than ± 25%
(still to be determined)
For regulatory standard setting, the sampling particle losses have
been standardised (as far as practical) so that repeatable/
comparable measurements are taken. Large differences in engine
technology particle size distributions could impact the comparability
for the future.
Possible use in a future standard
System loss correction methodology could be used
in other applications where particle size is not available
Aerosol Society Meeting – Birmingham 10th November 2016
Summary
Aircraft Gas Turbine nvPM mass & number
measurements passed into international regulation (Feb 2016)
• Multiple emissions certification quality tests been conducted
by reference systems & engine manufacturers
• nvPM mass and number reproducibility typically within ±25%
• Mass LOQ at ~5 μg/m3 equivalent to ~50 μg/m3 at engine exit
o nvPM mass emissions below this level observed…
• Improvements in mass calibration ongoing – source important
• System Loss correction method defined
• Work ongoing to improve measurement and system loss
uncertainties
• System optimised for nvPM not suitable for Total PM
Aerosol Society Meeting – Birmingham 10th November 2016
Thank you for listening
Many thanks to the large number of people globally
involved in this work
Any further questions, feel free to contact me:
Aerosol Society Meeting – Birmingham 10th November 2016
Additional back-up slides
Operating mode Power setting Time in mode
1. Taxi / Idle 7% take-off thrust 26.0 minutes
2. Take-off 100% Std. day take-off thrust 0.7 minutes
3. Climb 85% take-off thrust 2.2 minutes
4. Approach 30% take-off thrust 4.0 minutes
Landing
Aviation regulatory LTO (Landing Take-off cycle)
Aerosol Society Meeting – Birmingham 10th November 2016
ICAO Regulatory nvPM standard – maximum mass
concentration equivalent to Smoke standard (only for GT’s with thrust >26.7 kN
includes probe thermophoretic loss
= ~15 to 30% correction for unmixed (core only) sampling
Aerosol Society Meeting – Birmingham 10th November 2016
The constant 22.4 is the volume of one mole of air in litres at STP conditions rounded to one decimal place
ICAO Regulatory nvPM standard (only for GT’s with thrust >26.7 kN
report nvPM Emission Indices at each LTO point
includes probe thermophoretic loss
System Loss correction factors reported for airport
inventories
kSL_mass and kSL_num at each of the 4 LTO points
Aerosol Society Meeting – Birmingham 10th November 2016