PM emissions measurements and size distribution in a Turbojet engine test facility

Abstract

As the aviation sector continues to grow into the future, there is concern about atmospheric and Local Air Quality (LAQ) particle emissions and their impact on the environment and on human health (Waitz, 2004). Within this study, a series of particulate emissions experiments were carried out on different turbofan engines at INTA Turbojet Test Centre. A custom-designed single probe was installed in the stack of the testbed located 40 meters downstream of the exhaust nozzle exit plane. Volatile and non-volatile particles were sampled using this probe. The plume sample consists of emissions from the engine combustion exhaust, diluted by the bypass fan air flow and entrained air around the engine. The sample can be considered characteristic of short timescale plume transformation processes of engine emissions in the environment. The extractive emissions sampling system and the instrumentation used in the laboratory, located outside of the stack, included an ELPI+ (Dekati), a CPC (TSI 3775) and an SMPS (TSI 3934). Total PM emissions data was acquired across different engine power conditions during endurance testing. The methodology was utilised whilst running multiple engines at reproducible power conditions in cycle tests.

Full text

PM emissions measurements and size distribution in a Turbojet engine test facility
V. Archilla1, J. Rodriguez-Maroto2, M. Izquierdo1, E. Rojas2, D. Sanz2, M. Johnson3, M. Pujadas2, R. Díaz4
1 Turbojet Test Centre, INTA, Torrejón de Ardoz, 28850, Spain
2 Department of Environment, CIEMAT, Madrid, 28040, Spain
3 Test and Measurement Department, Rolls-Royce plc, Derby, UK
4 Higher Polytechnic School, University San Pablo CEU, Madrid, Spain
Keywords: aircraft, particle emissions, aerosol modelling, environmental impact, turbojet test facility
Presenting author email: archillapv@inta.es
As the aviation sector continues to grow into the future,
there is concern about atmospheric and Local Air Quality
(LAQ) particle emissions and their impact on the
environment and on human health (Waitz, 2004).
Within this study, a series of particulate emissions
experiments were carried out on different turbofan
engines at INTA Turbojet Test Centre. A custom-
designed single probe was installed in the stack of the
testbed located 40 meters downstream of the exhaust
nozzle exit plane. Volatile and non-volatile particles were
sampled using this probe. The plume sample consists of
emissions from the engine combustion exhaust, diluted by
the bypass fan air flow and entrained air around the
engine. The sample can be considered characteristic of
short time-scale plume transformation processes of engine
emissions in the environment.
The extractive emissions sampling system and the
instrumentation used in the laboratory, located outside of
the stack, included an ELPI+ (Dekati), a CPC (TSI 3775)
and an SMPS (TSI 3934). Total PM emissions data was
acquired across different engine power conditions during
endurance testing. The methodology was utilised whilst
running multiple engines at reproducible power
conditions in cycle tests. Multiple engine tests have
shown a same PM response pattern.
Figure 1 shows real-time particle size distribution
information and total particle number concentration of the
engine plume exhaust over the particle size spectrum from
6 to 1000 nm. Data was acquired at two stable engine
power conditions (low and high) and also covered
transient conditions (acceleration, deceleration) using the
ELPI+ fast response instrument (1Hz).
In Figure 2, it can be observed that the smallest (6
to 16nm) size fraction is the main contributor to the total
number concentration, with an increase observed at the
higher engine power level (1,3x105 particles/cc to 2,4x105
particles/cc). This size fraction can be mainly attributed to
volatile particles which have formed during the cooling
and dilution of the engine exhaust plume through the
testbed detuner.
The particle size distribution shape changes as a
function of engine power conditions. The geometric mean
diameter was found to increase with the increasing engine
power, as reported in other studies (Crayford 2012, Lobo,
2015).
At low engine power, the non-volatile (soot) PM
size mode is small enough to be merged with the volatile
PM size mode. However, at high engine power, the
particle size distribution appears bi-modal with the non-
volatile PM mode at an increased size. Large particles
(>200nm) are observed for a short time during transient
engine manoeuvres. These particles are likely ‘shedding’
of deposited particles from a surface (either from engine
or from detuner) due to sudden flow/pressure changes.
These results provide insight into real-world
aircraft emissions at airports. The data can be used to help
understand aircraft engine steady state and transient
emissions, which could impact emissions estimation at
airports and related environmental impacts.
Figure 1. Evolution of particle size distribution at
different engine operation phases (A: Acceleration, D:
Deceleration, H: High Power, L: Low Power).
Figure 2. PM Concentration per Impactor Stage at Low
and High power conditions.
Waitz, I.A., et al. (2004). Aviation and the Environment:
a National Vision Statement,Framework for Goals
and Recommended Actions, Report to the United
States Congress, on behalf of the U.S. DOT, FAA and
NASA.
Lobo, P., Hagen, D.E., (2015) PM Emissions
measurements of in-service commercial aircraft
engines during the Delta-Atlanta Hartsfield Study.
Atmospheric Environment 104, 237-245.
Crayford, A., Johnson, M.P., 2012. Studying, Sampling
and Measuring of Aircraft Particulate Emissions III e
Specific Contract 02: SAMPLE III - SC.02.