Kathleen M. Tacina and Christopher M. Heath

Glenn Research Center, Cleveland, Ohio

Evolution of Combustion-Generated Particles at

Tropospheric Conditions

NASA/TM—2012-217257

January 2012

GT2010-23689
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Kathleen M. Tacina and Christopher M. Heath

Glenn Research Center, Cleveland, Ohio

Evolution of Combustion-Generated Particles at

Tropospheric Conditions

NASA/TM—2012-217257

January 2012

GT2010-23689

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

Turbo Expo 2010

sponsored by the American Society of Mechanical Engineers (ASME)

Glasgow, Scotland, United Kingdom, June 14–18, 2010
Acknowledgments

This research was funded by NASA’s Fundamental Aeronautics/

Subsonic Fixed Wing and Fundamental Aeronautics/Supersonics program.

Available from

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National Technical Information Service

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Available electronically at http://www.sti.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by technical management. 
ABSTRACT

This paper describes particle evolution measurements taken

in the Particulate Aerosol Laboratory (PAL). The PAL consists of

a burner capable of burning jet fuel that exhausts into an altitude

chamber that can simulate temperature and pressure conditions

up to 13,700 m. After presenting results from initial temperature distributions inside the chamber, particle count data measured in the altitude chamber are shown. Initial particle count

data show that the sampling system can have a significant effect

on the measured particle distribution: both the value of particle

number concentration and the shape of the radial distribution of

the particle number concentration depend on whether the measurement probe is heated or unheated.

Nomenclature

B Buoyancy flux

d0 Nozzle diameter

d

∗ Equivalent source diameter, d∗ = d0

q ρ0

ρ∞

g Gravitational constant

J Momentum flux

lc Coflow length scale

lM Morton length scale

m Mass flux

Q Volume flux

R Richardson number

r Radial coordinate

Re Reynolds number

T Temperature

u Velocity

x Axial distance from the jet exit plane

xE Axial distance from the virtual origin to the jet exit plane

ρ Density

θ Normalized temperature difference, T−T∞

T0−T∞

ζ Particle number concentration

Subscripts

0 Nozzle exit

CL Centerline

∞ Chamber

1

Evolution of Combustion-Generated Particles at 

Tropospheric Conditions 

Kathleen M. Tacina and Christopher M. Heath 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

NASA/TM—2012-217257
Transition Pipe

Main Air

Combustion

Chamber

Mixing

Chamber

Fuel

Atomization

Air

Combustion Chamber Casing

From cold

gas supply

To altitude exhaust

-5.08

0

10.16

20.32

30.48

40.64

50.8

60.96

71.12

81.28

91.44

101.6

111.76

121.92

132.08

139.7

Not to scale

(a) (b)

FIGURE 1: The Particulate Aerosol Laboratory: (a)sketch and (b)photograph. Note that in (b), the burner is covered by a pressure

housing. The gas (nitrogen or air) from the cold gas supply simulates the atmosphere, and the burner exhaust simulates aircraft engine

exhaust.

1 Introduction

Although particulate emissions from aircraft engines were

initially of concern because of the visible smoke [1, 2], recent

research has focused on the health and environmental effects of

ultrafine particulate emissions. Due to the negative health effects

of ultrafine particles, the regulations on particles smaller than 2.5

microns have become increasingly stringent [3]; most particulates emitted by aircraft are smaller than 2.5 microns [1, 4].

A major environmental effect of aircraft particulate emissions is their effect on the the formation and properties of cirrus

clouds in the troposphere; however, this effect is not well understood [5]. Several areas require further research, including the

microphysical and chemical processes governing the evolution

of aviation particulates. Previous work has sought to characterize aircraft engine emissions using combustion rigs, on-ground

engine tests [4, 6–8], and measurements taken in the aircraft engine plumes at altitude [6]. The work described in this paper

complements these efforts.

This paper describes measurements taken in the Particulate

Aerosol Laboratory (PAL) at NASA Glenn Research Center. In

this unique facility, a combustor capable of burning jet fuel exhausts into an altitude chamber capable of simulating temperature and pressure conditions up to 45,000 ft, allowing the particle evolution to be studied at altitude conditions. A scanning

mobility particle sizer (SMPS) measures the particulate profile

at the combustor exit and in the altitude chamber. The probe

used to sample the exhaust plume in the altitude chamber can be

placed at discrete axial positions that range from the exhaust nozzle exit to the top of the altitude chamber. This paper will present

initial measurements of the particle size distribution taken from

the combustor and measurements of the particle size distribution

taken in the altitude chamber.

2 Facilities and Instrumentation

2.1 Facility Description

The Particulate Aerosol Laboratory (PAL) consists of a

burner connected to an altitude chamber, as shown in Figure 1.

The burner is capable of burning conventional jet fuels and alternative fuels such as Fischer-Tropsch. A 1.6-m long transition

NASA/TM—2012-217257 2
pipe connects the burner exit to the altitude chamber; the transition pipe terminates in a 1.27-cm diameter nozzle that exhausts

the combustion products into the altitude chamber. The altitude

chamber can simulate standard day pressures and temperatures

up to altitudes of 13,700 m.

As shown in Figure 1a, the burner is composed of two parts:

a combustion chamber and a mixing chamber. The upstream

section of the combustion chamber is surrounded by the mixing

chamber. The main combustion air enters the burner in the annular area between the combustion chamber and the combustion

chamber casing. (A bulkhead prevents mixing between the main

air in this annular area and the combustion products in the mixing

chamber.) Flowing upstream, the main air enters the combustion

zone through a 3.81-cm diameter opening in the upstream end

of the combustion chamber. Fuel and a small quantity of atomization air enter the combustion chamber through an air assist

fuel injector. The combustion products enter the mixing chamber through a 0.635-cm annular slot in the downstream end of

the combustion chamber. The entire burner is surrounded by a

housing, as shown in 1b. The burner pressure is one to two atmospheres.

After exiting the burner, the combustion products flow

through a 2.43-cm inner diameter transition pipe into the altitude chamber. An orifice in the transition pipe drops the pressure

of the combustion products to near the pressure of the altitude

chamber. Ports in the transition pipe upstream of the orifice allow

combustion product samples to be drawn for gas and particulate

analysis.

A cold gas supply (nitrogen or air) provides the working

fluid for the altitude chamber. This working fluid simulates the

atmosphere and allows the effects of mixing between the hot

combustor exhaust and a cold atmosphere to be studied. Nitrogen

was the working fluid for all measurements reported here.

The chamber diameter is 0.597-m, and the height of its

cylindrical test section in 1.83-m. Four window ports, each 1.52-

m tall by 0.102-m wide, are located 90oapart from each other.

The window ports can be fitted with windows, instrumentation

plates, or blanks. When a window is installed, two panes of

glass are used, and the space in between the panes is kept at vacuum;this prevents condensation on the windows and also provides good insulation. (When a blank or instrumentation plate

is used, it is a single thickness of aluminum and does not provide good insulation.) For the measurements reported here, three

ports contained windows and one port contained an instrumentation plate; Figure 1a shows the instrumentation plate that was

used during these measurements.

2.2 Instrumentation

A TSI scanning mobility particle sizer (SMPS) system

model 3936NL76 — consisting of a TSI model 3776 condensation particle counter (CPC), a TSI model 3080 electrostatic clas30 20 10 0 10 20 30

Radial distance (cm)

210

220

230

240

250

260

270

Temperature (K)

0.10 m

0.30 m

0.61 m

0.91 m

1.40 m

6,100 m

9,140 m

12,190 m

FIGURE 2: Baseline chamber temperature distribution with the

burner off.

sifier, and a TSI model 3085 nano differential mobility analyzer

— was used to measure the particle size distribution. The CPC

was also used alone to measure the particle count.

A blunt-tipped sampling probe with a 0.32-cm inner diameter was inserted into the transition pipe facing normal to the

flow. This probe was used to sample the particle distribution at

the burner exit. To minimize agglomeration and condensation in

the sampling system, the combustion products were diluted with

dry nitrogen slightly downstream of the probe tip.

A blunt-tipped sampling probe was also used to measure the

particle count in the altitude chamber. The probe face was parallel to the primary flow direction except for the measurements at

0.18 m downstream of the nozzle exit at 12,190 m standard day

conditions; in this single case, the probe face was approximately

normal to the primary flow direction. This probe had a 0.4-cm

inner diameter and could be covered with heat tape to prevent

ice formation inside the probe. It was connected to a translation

stage that allowed it to be moved radially.

2.3 Test Conditions

Four burner conditions (see Table 1) and four altitude chamber conditions were studied. The altitude chamber conditions

corresponded to standard day temperatures and pressures at

6,100 m; 9,140 m; and 12,190 m [9] as well hot day temperature and pressure conditions at 9,140 m [10] (see Table 2). The

chamber Reynolds number indicates that the flow was turbulent

for all cases. As Figure 2 shows, the baseline temperature in

the altitude chamber (when no combustion products are added)

is nearly uniform except in the thermal boundary layer. (Note a

double-paned window is installed on the negative r side of the

altitude chamber, and an uninsulated instrumentation plate is inNASA/TM—2012-217257

3
TABLE 1: Burner conditions

Condition Fuel/Air Total Mass lM at xE at

Number Ratio Flow Rate 6,100 m 7,620 m 9,140 m 12,190 m 6,100 m 7,620 m 9,140 m 12,190 m

kg/min m m m m cm cm cm cm

1 0.045 0.166 2.16 2.82 3.02 4.55 3.0 3.1 2.9 2.8

2 0.032 0.230 2.98 3.88 4.18 6.28 3.0 3.1 2.9 2.8

3 0.017 0.342 4.50 5.88 6.28 9.43 3.1 3.2 3.0 2.9

4 0.007 0.336 4.99 6.65 6.75 9.95 3.5 3.6 3.4 3.3

FIGURE 3: Combustion product temperature as combustion

products exit the nozzle into the altitude chamber at x=0. For

all cases the temperature rapidly returned to the baseline temperature as the radial distance r increased, so only the region near

the nozzle exit is shown.

stalled at the positive r side of the instrumentation chamber; this

accounts for the asymmetry in the temperature distribution near

the chamber walls.)

Figure 3 shows the temperature distribution at the nozzle

exit. Note that this temperature distribution does not change significantly with altitude, indicating that the section of the transition pipe that enters the bottom of the altitude chamber is wellinsulated.

3 Facility Temperature Distribution

Because the particle evolution depends strongly on temperature, the temperature distribution in the altitude chamber was

characterized; the temperature distribution depends on the conditions at the nozzle exit, the conditions in the altitude chamber,

and the type of flow field that is established. From several nozzle diameters downstream of the nozzle exit to the axial location

where the effects of the altitude chamber walls become important, the flow field in the PAL should act as either a buoyant jet

or a momentum-dominated jet. The relative effects of jet exit

momentum and buoyancy are usually expressed in terms of the

Richardson number, R, or the ratio of the axial distance from the

nozzle exit, x, to the Morton length scale, lM [11, 12]. These are

defined in terms of the jet volume flux, Q, the jet momentum

flux, J, and the jet buoyancy flux, B, as:

R =

Q(B/ρ∞)

1

2

(J/ρ∞)

5

4

(1)

lM =

(J0/ρ∞)

3

4

(B0/ρ∞)

1

2

, (2)

where

Q =

Z∞

0

u(x,r)2πr dr, (3)

B =

Z∞

0

g∆ρ u(x,r)2πr dr, (4)

J =

Z∞

0

ρ u

2(x,r)2πr dr, (5)

u is the axial velocity, ρ is the density, and the subscripts 0 and

∞ refer to conditions at the jet exit and in the altitude chamber,

respectively. In the jet-like limit, R and x/lM are small; in the

plume-like limit, R approaches 1 and x/lM is large. Papanicolaou

and List [12] have shown that R ∝ x in the jet-like limit and R is

constant in the plume-like limit. They have also shown that flows

with x/lM < 1 exhibit jet-like scaling and flows with x/lM > 5

NASA/TM—2012-217257

4
TABLE 2: Chamber conditions

Altitude Altitude Day Type Temperature Pressure Density Chamber

Reynolds

Number

Nominal

Chamber

Coflow

Velocity

(m) (ft) (K) (kPa) (kg/m3) (m/s)

6,100 20,000 Standard 249 46.601 0.653 17,900 0.7

7,620 25,000 Hot 259 37.650 0.490 18,700 1.0

9,140 30,000 Standard 228 30.149 0.459 25,800 1.4

12,190 40,000 Standard 217 18.823 0.303 32,100 2.5

exhibit plume-like scaling.

For the measurements reported here, the axial locations of

interest range from several nozzle diameters to 71 cm downstream of the nozzle exit. In this region, R is small and x/lM  1

(see Table 1), so the effects of buoyancy should not be significant. A similar length scale analysis of the effects of the cold

nitrogen coflow [13] shows that the coflow effects should also

be small. Therefore, the flow field is momentum-dominated and

should follow nonbuoyant jet scaling laws.

For momentum-dominated jets, it can be shown [14,15] that

a conserved scalar, such as the normalized temperature difference, θ ≡

T−T∞

T0−T∞

, is inversely proportional to the normalized distance from the virtual origin, (x+xE)/d

∗

, where x is the distance

from the jet exit, xE is the distance from the virtual origin to the

jet exit, and d

∗ = d0

q ρ0

ρ∞

. Diez & Dahm [11] 1show that for

a momentum-dominated or buoyant jet the distance xE that the

virtual origin is upstream of the nozzle exit is given by:

xE = lM











I

2

1

I

5/2

2

cδ c

3

u, j





"

(J0/ρ∞)

5/2

(m0/ρ∞)

2

(B0/ρ∞)

#





−

1

2

, (6)

where (7)

I1 = 0.262, (8)

I2 = 0.131, (9)

cδ = 0.36, and (10)

cu, j = 7.2 (11)

In other words, θ = cθ



x+xE

d

∗

−1

, where cθ is approximately 5.4

1The formula given here does not match the one given by equations 42 and 47

in [11]. There seem to be several typographical errors in [11], with the missing

exponent of -1/2 in equation 47 being the most important. The missing exponent can be found by following the derivation described in the text of [11] and

substituting equation 46 into equation 44.

[16]. Furthermore, momentum-dominated jets are self-similar,

so a conserved scalar normalized by its centerline value is a

function of the radius normalized by the jet width, δ; that is,

θ/θCL = f (r/δ). For both momentum-dominated and buoyant

jets, δ is proportional to axial distance from the virtual origin;

therefore, θ/θCL = f

0



r

x+xE



. Figures 4a and 4b support this

scaling: Figure 4a is consistent with θ/θ0 = 5.4(

x+xE

d

∗ )

−1

scaling until the effect of the altitude chamber wall becomes important at x+xE

d

∗ ≈ 130. Figure 4b shows that θ/θCL is a function

of r/(x+xE) for r/(x+xE) values that are sufficiently far from

the chamber walls. (When interpreting Figure 4b, note that the

temperature increase due to the chamber walls is more important

on the poorly-insulated instrument plate side of the chamber (+r)

than on the relatively well-insulated window side (−r) and that as

the axial distance increases the r/(x+xE) value at which the wall

effects become important decreases.) Also shown in Figure 4b

are a curve fit to the data, the normalized concentration profile,

ζ /ζCL, used by Diez & Dahm [11], and the normalized velocity

profile, u/uCL, used by Hussein et al. [17]. The curve fit used

to model the current data and the profiles used by the Diez &

Dahm and Hussein et al are of the form ξ = e

−α(

r

x+xe )

2

, where ξ

is θ/θCL, ζ /ζCL, or u/uCL. The width parameter α of the θ/θCL

is between the α values for ζ /ζCL and u/uCL, further indicating

that the jet scaling is appropriate for the normalized temperature

difference θ.

4 Initial Particle Evolution Measurements

Particle measurements were taken both in the transition pipe

(see Figure 1) and in the altitude chamber for burner condition 1

from Table 1 and at all chamber conditions listed in Table 2. For

the particle measurements made in the transition pipe, the sample

was diluted with nitrogen with a dilution ration of 1.91 to prevent

condensation and agglomeration in the sampling line; the sample

NASA/TM—2012-217257

5
0 20 40 60 80 100 120

Normalized Axial Distance (x +xE )=d¤

0.00

0.05

0.10

0.15

0.20

0.25

Normalized Temperature Difference 

μCL

h = 6,100 m

h = 9,140 m

h = 12,190 m

x = 0.30 m

x = 0.61 m

x = 0.71 m

x = 0.91 m

f/a = 0.007

f/a = 0.017

f/a = 0.032

f/a = 0.045

5:4x=d¤

1.0 0.5 0.0 0.5 1.0

Normalized Radial Distance r=(x +xE )

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Normalized Temperature Difference μ=μCL

h = 6,100 m

h = 9,140 m

h = 12,190 m

x = 0.30 m

x = 0.61 m

x = 0.71 m

x = 0.91 m

f/a = 0.007

f/a = 0.017

f/a = 0.032

f/a = 0.045

Curve fit

Diez & Dahm

Hussein et al

FIGURE 4: (a)Normalized jet centerline temperature θCL as a function of normalized axial distance (x+xE)/d

∗

and (b) the normalized

temperature distributions as a function of the normalized radial distance. The symbol color indicates the altitude conditions, the ’outer’

symbol indicates the axial position, and the ’inner’ symbol indicates the fuel-air ratio. Note that the effects of the chamber wall are

important when (x+xE)/d

∗ > 130.

was not diluted for measurements made in the altitude chamber.

4.1 Burner Measurements

A representative particle number distribution in the transition pipe is shown in Figure 5. Integrating the particle number

distribution gives a total number concentration of 1.2×107 particles per standard cubic centimeter, where standard pressure and

temperature are defined as 101.325 kPa and 298.15 K, respectively.

Note, however, that the particle measurements taken in the

chamber suggest that the combustor particle output is not steady

(see the next section). The variation of combustor particle output

with time is being measured, and for future tests, two particle

measurement systems will be used so that the particle distributions in the transition pipe and in the altitude chamber can be

measured simultaneously.

FIGURE 5: Particle number distribution in the transition pipe for

burner condition 1 (f/a = 0.045)

NASA/TM—2012-217257

6
4.2 Initial Measurements in the Altitude Chamber

Initially, attempts were made to take particle evolution measurements in the altitude chamber with standard day pressure

and temperature conditions corresponding to 9,140 m. Unfortunately, at these conditions, the water vapor in the jet condenses,

and in some cases freezes, in the sampling probe. Therefore, heat

tape was wrapped around the sampling probe and the altitude

chamber conditions were changed to the considerably warmer

hot day conditions at 7,620 m. For these chamber conditions and

burner condition 1, Figure 6 shows the particle number concentration as a function of radial distance at axial distance 0.30 and

0.51 m downstream of the jet exit. (Note that in Figure 6 and

in all other figures showing the particle number concentration,

the number concentration is given in particles per actual cubic

centimeter at the particle counter, not in particles per standard

cubic centimeter. At the particle counter, the temperature is approximately standard temperature but the pressure is the altitude

chamber pressure.)

After successfully measuring the particle number concentration with a heat tape-wrapped probe at hot day conditions corresponding to 7,620 m, initial particle number concentrations were

measured at standard day conditions corresponding to 6,100 m,

9,140 m, and 12,190 m, as shown in Figures 7 and 8. In all

cases, it was possible to measure the particle number concentration with the heat tape turned on. However, when the heat tape

was turned off, it was not possible to measure the number concentration near the jet centerline at 6,100 m and 9,140 m because

the number concentration was above the maximum concentration

that the CPC could measure.

(Note that in several of the plots, there appear to be two separate particle curves. This is most apparent in the measurements

taken with the heat tape on at 6,100 m conditions in Figure 7a. In

all cases, the measurements were taken at different times, and the

difference between the measurements appear to be a real change

in the particle concentration, not a lack of precision in the CPC.

For example, the ”upper” curve in 7a was taken earlier in the

day than the ”lower” curve. The change in particle concentration

could be caused by either a change in the chamber conditions or

a change in the particle output from the combustor. Because the

chamber conditions were constantly monitored to ensure the temperature and pressure remained as constant as possible, it seems

to be more likely that a change in particle output from the combustor was responsible for the change in the chamber particle

concentration. In the future, the combustor particle size distribution will be monitored continuously; for the measurements reported here, the same CPC was used for the combustor and the

chamber particle measurements and these measurements could

not be taken simultaneously.)

In addition, icing continued to be a problem. It was possible to prevent ice from forming in the sampling probe and at the

sampling probe tip by avoiding sudden changes in the radial location of the probe and by briefly turning on the heat tape to melt

the ice if it began to form. However, it is unclear how many of

the particles measured when the heat tape was turned off were

present in the plume and how many were formed in the probe.

Unfortunately, it is also unclear that measurements taken

when the heat tape was turned on accurately reflect the number

of particles in the jet plume. For the heated-probe measurements

taken at 12,190 m conditions, the peak particle concentration occurs off the centerline, which is an unexpected result. However,

for the heated-probe measurements taken at all other chamber

conditions, the peak particle concentration occurs on the centerline, as expected. Research groups measuring the particulate

emissions of jet engines on the ground have also noticed unexpected and as yet unexplained effects when using heated probes2

,

so it appears that using a heated probe is not an ideal solution.

Figure 9 shows the normalized particle number concentration profiles, ζ /ζmax vs. r/(x+xE). The profiles at chamber conditions corresponding to altitudes of 6,100 m and 9,140 m measured with a heated probe were consistent with the normalized

temperature profiles, θ/θCL. Both profiles at a chamber condition corresponding to 7,620 m, also taken with a heated probe,

collapsed onto each other but the profiles were narrower than the

normalized temperature profile. The profiles taken with an unheated probe at a chamber condition corresponding to 12,190 m

are wider than the normalized temperature profile, and the profiles taken with a heated probe at the same chamber conditions

have a maximum value off the centerline. Both of the heatedand unheated-probe 12,190 m profiles are very different in shape

than the normalized temperature profiles.

Figure 10 shows the maximum concentration at each axial

location and chamber condition as a function of the normalized

downstream distance, x/d

∗

. If the particle number concentration

is a conserved scalar, the maximum concentration will decrease

with axial distance from the nozzle exit. However, as the temperature in the jet cools, volatile particles will form; if a large

enough number of volatile particles is formed, the particle number concentration will increase with axial distance. In addition,

the heated probe may revaporize some or all of the volatile particles formed in the jet. (Because all particle measurements are

done at room temperature, some particles may also revaporize in

the sampling line between the altitude chamber and the condensation particle counter for both the heated and unheated probe

cases.)

The results from Figure 10 are inconclusive. At the warmest

chamber temperature — which occurs at the 7,620 m hot day

conditions — the maximum particle concentration decreases with

axial distance when the probe is heated. At the coldest chamber temperature, — which occurs at the 12,190 m standard day

conditions — the particle concentration increases with axial distance when the probe is heated. So far, because more volatile

particles will form at the cold 12,190 m standard day conditions

NASA/TM—2012-217257

7
0.10 0.05 0.00 0.05 0.10

Normalized Radial Distance, r=(x +xE )

0

100000

200000

300000

400000

500000

600000

700000

800000

Heated Probe Number Concentration (#/cm

3 )

(a)

0.2 0.1 0.0 0.1 0.2

Normalized Radial Distance, r=(x +xE )

0

50000

100000

150000

200000

250000

Heated Probe Number Concentration (#/cm

3 )

(b)

FIGURE 6: Particle count at 7,620 m hot day conditions and at (a)x=0.30 m and (b)x=0.51 m downstream of the nozzle exit. Heat tape

is wrapped around the particle probe for both cases.

0.4 0.2 0.0 0.2 0.4

Normalized Radial Distance, r=(x +xE )

0

5000

10000

15000

20000

25000

30000

Heated Probe Number Concentration (#/cm

3 )

0.4 0.2 0.0 0.2 0.4

Normalized Radial Distance, r=(x +xE )

0

20000

40000

60000

80000

100000

Heated Probe Number Concentration (#/cm

3 )

FIGURE 7: Particle number as a function of radial location at (a) 6,100 m conditions and x=0.30 m and (b) 9,140 m conditions and

x=0.71 m. Red symbols indicate that the heat tape wrapped around the particle probe was turned on, and blue symbols indicate that it

was turned off.

than at the much warmer 7,620 m hot day conditions, this could

be consistent with volatile particles forming in the jet and then

revaporizing in the heated probe. However, unheated probe measurements at the 12,190 m standard day conditions show particle

number concentration decreasing with increasing axial distance;

although this could be consistent with particles revaporizing in

the sampling line, it is inconsistent with the heated probe measurements.

When particulate emissions measurements are taken on the

ground or in a test cell, the particulate sample is diluted at the

probe tip to prevent condensation and to freeze the particulate

chemistry. In this study, the altitude chamber particulate measurements were not diluted because the mixing in the jet dilutes

the combustion products by a factor of between five and ten to

one, depending on axial location. However, because the ambient temperature in the altitude chamber is much colder than the

temperature in the jet — especially on the jet centerline and at

the lower axial locations — more dilution may be necessary. For

NASA/TM—2012-217257

8
0

200000

400000

600000

800000

1000000

Unheated Probe Number Concentration (#/cm

3 )

0

5000

10000

15000

20000

Heated Probe Number Concentration (#/cm

3 )

0.4 0.2 0.0 0.2 0.4

Normalized Radial Distance, r=(x +xE )

Heat tape on

Heat tape off

0

100000

200000

300000

400000

500000

600000

700000

800000

Unheated Probe Number Concentration (#/cm

3 )

0

10000

20000

30000

40000

50000

60000

70000

Heated Probe Number Concentration (#/cm

3 )

0.4 0.2 0.0 0.2 0.4

Normalized Radial Distance, r=(x +xE )

Heat tape on

Heat tape off

FIGURE 8: Particle concentration with and without heat tape at 12,190 m standard day conditions at (a) 0.18 m and (b) 0.71 m downstream of the nozzle exit. Red symbols indicate that the heat tape wrapped around the probe was turned on, and blue symbols indicate

that it was turned off.

future measurements, diluting the particulate sample so that the

vapor pressure of water in the sample is below the saturation vapor pressure at the ambient chamber conditions could prevent

condensation in the probe.

Before further particle measurements are made in the altitude chamber, it would be best to do a modeling study of the

particle sampling system. This study could help determine the

degree of condensation in the unheated particle probe and the effects of heating the particle probe. It could also provide guidance

for choosing a sampling flow rate and help determine if a larger

diameter sampling probe or tip dilution could reduce the particle

probe effects.

0.4 0.2 0.0 0.2 0.4

Normalized Radial Distance r=(x +xE )

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Normalized Concentration 3=3CL

h = 6,100 m

h = 7,620 m

h = 9,140 m

h = 12,190 m

x = 0.18 m

x = 0.30 m

x = 0.51 m

x = 0.71 m

μ curve fit

Diez & Dahm

Hussein et al

FIGURE 9: Normalized particle number distribution plotted with

the curve fit for θ/θCL. Unfilled symbols are used for measurements taken when the heat tape was turned on, and filled symbols

are used for measurements taken when the heat tape was turned

off.

NASA/TM—2012-217257

9
0 50 100 150 200

Normalized Axial Distance (x +xE )=d¤

0

200000

400000

600000

800000

Maximum Concentration 

3max

h = 6,100 m

h = 7,620 m

h = 9,140 m

h = 12,190 m

0 50 100 150 200

Normalized Axial Distance (x +xE )=d¤

0

50000

100000

150000

200000

250000

Maximum Concentration 

3max

h = 6,100 m

h = 7,620 m

h = 9,140 m

h = 12,190 m

FIGURE 10: Maximum concentration as a function of the normalized axial distance. Unfilled symbols are used for measurements taken

when the heat tape was turned on, and filled symbols are used for measurements taken when the heat tape was turned off.

5 Conclusions

Initial temperature and particle number concentration profiles were measured in the Particulate Aerosol Laboratory. This

unique facility simulates engine exhaust at altitude by exhausting

hot combustor exhaust into an altitude chamber. The small nitrogen coflow in the altitude chamber is kept at pressure and temperature conditions corresponding to aircraft cruising altitudes. Results from the normalized temperature distribution, θ, show that

the combustor exhaust flow field follows momentum-dominated

jet scaling. Initial particle number concentration measurements

were taken with a heated probe at four altitude chamber conditions and with an unheated probe at one altitude condition. Results show that whether the probe is heated or unheated affects

the particulate measurements. Particle number concentrations

measured with an unheated probe can be more than five times

as great as those measured with a heated probe. In addition, the

shape of the radial particle number concentration profile can be

different when using an unheated probe than when using a heated

probe. A modeling study of the particle sampling system should

be done before further testing to determine the effects of probe

heating and of condensation in the particle probe.

REFERENCES

[1] Blevins, L. G., 2003. Particulate matter emitted from aircraft engines. AIAA 2003-2764.

[2] SAE E-31 Technical Committee, 1997. Aircraft gas turbine

smoke measurement. SAE ARP 1179.

[3] U.S. EPA, 2004. Air quality criteria for particulate matter

(october 2004). EPA 600/P-99/002aF-bF, October.

[4] Anderson, B., Branham, H.-S., Hudgins, C., Plant, J., Ballenthin, J., Miller, T., Viggiano, A., Blake, D., Boudries, H.,

Canagaratna, M., Miake-Lye, R., Onasch, T., Wormhoudt,

J., Worsnop, D., Brunke, K., Culler, S., Penko, P., Sanders,

T., Han, H.-S., Lee, P., Pui, D., Thornhill, K., and Winstead, E., 2005. Experiment to characterize aircraft volatile

aerosol and trace species emissions. NASA/TM-2005-

213783.

[5] Wuebbles, D.(workshop chair), 2006. Workshop on the impacts of aviation on climate change: A report of findings

and recommendations. Report PARTNER-COE-2006-004-

SUMMARY, June.

[6] Schumann, U., Arnold, F., Busen, R., Curtius, J., Karcher,  ̈

B., Kiendler, A., Petzold, A., Schlager, H., Schroder, F.,  ̈

and Wohlfrom, K.-H., 2002. “Influence of fuel sulfur on

the composition of aircraft exhaust plumes: The experiments SULFUR 1-7”. Journal of Geophysical Research,

107(D15).

[7] Bhargava, A., Beyersdorf, A.J.and Winstead, E., Thornhill, K., Liscinsky, D., Souza, J., Wey, C., Tacina, K.,

Timko, M., Yu, Z., Onasch, T., Miake-Lye, R., Corporan,

E., Howard, R., DeWitt, J., and Klingshirn, C., 2008. The

impact of alternative fuels on aircraft emissions. Presentation at 2008 aaar annual conference.

NASA/TM—2012-217257

10
[8] Wey, C., Anderson, B., Hudgins, C., Wey, C., Li-Jones,

X., Winstead, E., Thornhill, L., Lobo, P., Hagen, D., and

Whitefield, P. e. a., 2006. Aircraft particle emissions experiment. NASA/TM-2006-214382.

[9] , 1976. U.s. standard atmosphere, 1976. NOAA–S/T 76-

1562.

[10] , 2007. Definition of commonly used day types (atmospheric ambient temperature characteristics versus pressure

altitude). SAE/ARP210 2007-02.

[11] Diez, F. J., and Dahm, W. J., 2007. “Effects of heat release on turbulent shear flows. part 3. buoyancy effects due

to heat release in jets and plumes.”. Journal of Fluid Mechanics, 575, pp. 221–255.

[12] Papanicolaou, P. N., and List, E. J., 1988. “Investigations

of round vertical turbulent buoyant jets”. Journal of Fluid

Mechanics, 195, pp. 341–391.

[13] Lee, J. H., and Chu, V. H., 2003. Turbulent Jets and

Plumes: A Langrangian Approach, 1 ed. Kluwer Academic

Publishers, Norwell, Massachusetts.

[14] Thring, M., and Newby, M., 1953. “Combustion length

of enclosed turbulent jet flames”. Proceedings of the 4th

International Symposium on Combustion, pp. 789–796.

[15] Wygnanski, I., and Fiedler, H., 1969. “Some measurements

in the self-preserving jet”. Journal of Fluid Mechanics, 38,

pp. 577–612.

[16] Dahm, W. J., and Dimotakis, P. E., 1990. “Mixing at large

schmidt number in the self-similar field of turbulent jets”.

Journal of Fluid Mechanics, 217, pp. 299–300.

[17] Hussein, J. H., Capp, S. P., and George, W. K.,

1994. “Velocity measurements in a high-reynolds number,

momentum-conserving, axisymmetric turbulent jet”. Journal of Fluid Mechanics, 258, pp. 31–75.

NASA/TM—2012-217257

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Evolution of Combustion-Generated Particles at Tropospheric Conditions 

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14. ABSTRACT

This paper describes particle evolution measurements taken in the Particulate Aerosol Laboratory (PAL). The PAL consists of a burner 

capable of burning jet fuel that exhausts into an altitude chamber that can simulate temperature and pressure conditions up to 13,700 m. 

After presenting results from initial temperature distributions inside the chamber, particle count data measured in the altitude chamber are 

shown. Initial particle count data show that the sampling system can have a significant effect on the measured particle distribution: both the 

value of particle number concentration and the shape of the radial distribution of the particle number concentration depend on whether the 

measurement probe is heated or unheated. 

15. SUBJECT TERMS

Combustion; Particulates; Emissions; Particles; Aerosol 

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