Document
An Investigation of Glaciated Cloud
Capabilities in the NASA Glenn Icing
Research Tunnel
Laura E. King - Steen – HX5 Sierra LLC
Cleveland, Ohio
th 10 Atmospheric and Space Environments Conference June 25, 2018 HX5 Sierra LLC National Aeronautics and Space Administration www.hxfive.com www.nasa.gov 1 www.sierralobo.com The Problem:
• In 2015 the FAA Added Appendix D to Part 33 engine
certification requirements that included Mixed Phase
and Ice Crystal Icing to aircraft engine certification
• The Icing Research Tunnel (IRT) at NASA Glenn
historically has operated almost solely with a super -
cooled liquid water cloud. However, NASA researchers
expressed interest in investigating the IRT’s capabilities
to create a fully glaciated cloud as a potentially less -
expensive alternative to creating ice crystals in an
engine icing facility
• The purpose of this test was ONLY to see if the IRT can
create a fully - glaciated cloud, not to explore mixed -
phase capabilities. Mixed - phase could be a future goal, but is beyond the scope of the present work.
Test Facility
• Test section size: 6 ft. x 9 ft. (1.8 m x 2.7 m) • Calibrated MVD range: 14 – 270 μm • All water content measurements are made in • Calibrated LWC range: 0.15 – 4.0 g/m the center of the test section (function of airspeed) • Calibrated test section airspeed range: 50 – 325 kts • This test only utilized the Mod1 nozzles o o (lower water flow rate) • Air temperature: - 40 C static to +10 C total
Developing a
Hypothesis
Include picture!
IRT spraybars as seen from the top of the contraction section, facing upstream
• IRT Spraybars are supplied with air and water. The pressures of
each are controlled to create the desired water content and drop -
size distribution.
o
• Air & Water are typically heated to 80 - 85 C in order to avoid
freezing the water drops
• So we asked ourselves, what happens if we don’t heat it?
• Air & Water are heated, but cannot be actively cooled, so the best we
can do is to run the air and water “unheated ”
• Pumps contribute to the water heat
o
• Operating temperature of spraybar air was around 30 C
o
• Operating temperature of spraybar water was around 43 C
The Multi - Element Sensor
From Science Engineering Associates, Inc.
Commonly known as “the Multi - Wire” Typical Multi - Wire shrouds contain 3 sensing elements of various sizes; Different element types are designed for better response to different conditions • 2mm forward - facing half - pipe: “ TWC” Heated • Total Water Content sensor, responds to liquid stem & water and ice crystals shroud • 2mm reverse - facing half - pipe “2mm ” • responds to liquid water, approx. 10% “false - response” to ice crystals* 1 in.
2.54 cm • 0.5mm wire, “0.5mm ” • responds to liquid water, and approx. 10% “false - response” to ice crystals* Sensing • There is also a compensation wire, located behind the central element elements • measures changes coming only from airspeed, air temperature, air pressure, and relative humidity: “dry” conditions Given the different responses, we can compare data from the different element to determine if the cloud is glaciated *Struk, P.M., Bencic, T., Tsao, J., Fuleki , D., Knezevici , D.C., “Preparation for Scaling Studies of Ice - Crystal Icing at the NRC th Research Altitude Test Facility,” 5 AIAA Atmospheric and Space Environments Conference, AIAA - 2013 - 2675, 2013.
Multi - Element Sensor
Theory of Operation
o • A voltage is applied across each of the elements to maintain them at a temperature of 140 C • Elements are cooled by convection and impinging water • Data system records the power required to maintain each element at constant temperature.
• The compensation wire is shielded to stay dry; changes during a spray are reflected in the calculated water content • The recorded powers are used to calculate water content — the below equation has been adapted to assume the cloud is made of ice crystals rather than being purely liquid Subtract off cooling from dry air, correlated to comp wire P = P – ( offset + slope * P ) elem,wet elem,tot comp,dry Conversion factor 𝟓 𝑷 ( 𝒘𝒂𝒕𝒕𝒔 ) ∗ 𝟐 . 𝟑𝟖𝟗 × 𝟏𝟎 𝒆𝒍𝒆𝒎 , 𝒘𝒆𝒕 𝑰𝑾𝑪 = 𝒎 𝑪 𝑻 − 𝑻 + 𝑳 + 𝑪 𝑻 − 𝑻 + 𝑳 ∗ 𝑻𝑨𝑺 ∗ 𝒍 𝒎𝒎 ∗ 𝒘 𝒎𝒎 𝒑 , 𝑰𝑾𝑪 𝒎 𝒆 𝒍𝒕 𝑰𝑾𝑪 𝒇𝒖𝒔 𝒑 , 𝑳𝑾𝑪 𝒆𝒗𝒂𝒑 𝒎𝒆𝒍𝒕 𝒗𝒂𝒑 𝒆𝒍𝒆𝒎 𝒆𝒍𝒆𝒎 𝒔 Sample volume of Amount of energy required to raise the ice particle to sensing element (m /s) its evaporative temperature and then evaporate it ( cal /g) For this presentation, all data from the 3 vertical sensors (TWC, 2mm, 0.5mm) were calculated using this equation, 6 regardless of how the cloud was ultimately classified Source: the SEA User’s Manual
Test Procedures
• The air and water supply in the spraybars were left unheated
o • Air temps were around 30 C o • Water temps were around 43 C
• Spray time = 4 minutes
• Initial facility setpoint : highest total temperature and lowest airspeed, with nozzle settings to create our smallest possible drops (MVD approx.
12.7 μ m): o • Ttot = - 7 C • Airspeed = 100 knots • Pair = 60 psig • DelP = 10 psid
• Once it was confirmed this created a glaciated cloud, tunnel parameters
were varied to explore how cloud glaciation was affected by the
following: • Increasing drop size from 12.7 up to 30 μ m MVD • Decreasing nozzle air pressure 60, 40, 30 psig • Increasing airspeed 100, 150, 250 knots o • Decreasing tunnel total temperature - 7, - 15, - 25 C
Example “Good” Data Traces
TWC ice 3 3 3 TWC (IWC) 0.21 g/m TWC (IWC) 0.18 g/m TWC (IWC) 0.78 g/m raw raw raw 2mm / TWC 0.92 2mm / TWC 0.56 2mm / TWC 0.06 0.5mm / TWC 0.97 0.5mm / TWC 0.07 0.5mm / TWC 0.57
Fully Glaciated Fully Liquid
Mixed Phase
10 sprays in this test were stable for the • The ratio values of each of the side
duration of the spray, out of 27 fully cylinder elements to the center TWC
glaciated sprays measured element are used to determine if the
cloud is liquid, glaciated, or mixed
phase
Data Processing Notes:
• Ice water content from the TWC
• Data are averaged for each element,
element was also corrected for
starting 20 sec after spray begins, until
collection efficiency and compared to
2 sec before spray ends 8
the expected (IRT calibrated) LWC
Other Example Traces
Continuous Ramp - up,
Step - Increase, then Stable Ramp - up, then Stable
Never Stabilized
Cause: Recirculating crystals, Cause: Recirculating crystals, Cause: Recirculating Crystals,
non - compounding compounding &
continually compounding
4 sprays eventually “stabilizing”
3 sprays
9 sprays
Only observed at 100 knots, for which the loop transit time is approximately 25 seconds.
Presumably, then, the step - increase is due to
• For all such cases, if the readings were stable
cloud recirculation that for some reason only
for more than 1 minute, the data were
lasts for one loop around the tunnel averaged across the stable segment.
• If there was no stable segment, the condition
was not included in the subsequent plots
o
Warm temperatures: T = - 7 C
tot
o There was only one condition observed to be fully glaciated at Ttot = - 7 C , but there was still information to be found in the observed trends.
2mm/TWC & 0.5mm/TWC: Ttot = - 7 C IWC/LWCcalc: Ttot = - 7 C 0.70 1.80 0.5mm, V=100, Pair=60 IWC, V=100, Pair=60 1.60 0.60 2mm, V=100, Pair=60 IWC, V=150, Pair=60 0.5mm, V=150, Pair=60 1.40 IWC, V=250, Pair=60 0.50 2mm, V=150, Pair=60 1.20 IWC, V=100, Pair=40 0.5mm, V=250, Pair=60 1:1 0.40 1.00 2mm, V=250, Pair=60 IWC, V=150, Pair=40 LWCcal 0.5mm, V=100, Pair=40 0.80 0.30 2mm, V=100, Pair=40 IWC / 0.60 0.5mm, V=150, Pair=40 0.20 Water Content ratio to TWC 2mm, V=150, Pair=40 0.40 0.10 0.20 “fully glaciated” 0.00 0.00 10.0 12.0 14.0 16.0 18.0 20.0 10.0 12.0 14.0 16.0 18.0 20.0 MVD ( μ m) MVD ( μ m) Observations from 2mm and 0.5mm element ratios : • Glaciation is more likely at lower air speeds • Glaciation is more likely for a higher air pressure than for a smaller drop size • Suggests that drop residence time is more important than static temperature • Suggests that the cooling effect of the spray nozzle air pressure plays a substantial role • For a given air pressure, glaciation is more in cloud glaciation.
likely for low MVD ( deltaP ) values
o
Colder temperature: T = - 15 C
tot
IWC/LWCcalc: Ttot = - 15 C 2mm/TWC & 0.5mm/TWC: Ttot = - 15 C 1.80 0.30 =TWC climbed 0.5mm, V=100, Pair=60 and then 1.60 2mm, V=100, Pair=60 stabilized 0.25 0.5mm, V=150, Pair=60 1.40 around this 2mm, V=150, Pair=60 value.
1.20 0.20 0.5mm, V=250, Pair=60 2mm, V=250, Pair=60 1:1 1.00 0.5mm, V=100, Pair=40 0.15 2mm, V=100, Pair=40 0.80 0.5mm, V=150, Pair=40 WC / LWCcal IWC, V=100, Pair=60 0.10 0.60 2mm, V=150, Pair=40 “fully IWC, V=150, Pair=60 Water Content ratio to TWC 0.40 glaciated” IWC, V=250, Pair=60 0.05 IWC, V=100, Pair=40 0.20 IWC, V=150, Pair=40 0.00 0.00 10.0 12.0 14.0 16.0 18.0 20.0 10.0 12.0 14.0 16.0 18.0 20.0 MVD ( μ m) MVD ( μ m) • As expected, glaciation is more likely at a • The 250 kt (black) data breaks trend, in that colder temperature: more data points are glaciation appears to be more likely for showing full glaciation larger MVD values. However, this may be driven by uncharacteristic TWC values o • Similar observations as seen at - 7 C : • Glaciation more likely at lower air speeds • For a given air pressure, glaciation is more likely for low MVD ( deltaP ) values • Glaciation is more likely for a higher air pressure than for a smaller drop size
o
Cold temperature: T = - 25 C
tot
IWC/LWCcalc: Ttot = - 25 C 2mm/TWC & 0.5mm/TWC: Ttot = - 25 C 1.80 0.18 0.5mm, V=100, Pair=60 1.60 =TWC climbed 2mm, V=100, Pair=60 0.16 and then 0.5mm, V=150, Pair=60 1.40 0.14 stabilized 2mm, V=150, Pair=60 around this 1.20 0.12 0.5mm, V=100, Pair=40 value.
1:1 2mm, V=100, Pair=40 1.00 0.10 0.5mm, V=150, Pair=40 “fully glaciated” 0.80 0.08 2mm, V=150, Pair=40 WC / LWCcal IWC, V=100, Pair=60 0.5mm, V=250, Pair=40 0.60 0.06 WC ratio to TWC IWC, V=150, Pair=60 2mm, V=250, Pair=40 0.40 IWC, V=100, Pair=40 0.04 IWC, V=150, Pair=40 0.20 0.02 IWC, V=250, Pair=40 0.00 0.00 10.0 15.0 20.0 25.0 30.0 10.0 15.0 20.0 25.0 30.0 MVD ( μ m) MVD ( μ m) MVD ( deltaP ) values • As expected, glaciation is more likely at a colder temperature: more data points show full glaciation • Glaciation is more likely for a higher air pressure than for a smaller drop size o • Conditions were less stable at - 25 C.
• The 40 - psia data at 150 and 250 kts (blue & green • The data points for V=250 kts , Pair=60 were removed triangles) break trend, in that glaciation appears to from these plots — IWC was steadily increasing and did be more likely for larger MVD values. However, this not stabilize.
may be driven by uncharacteristic TWC values o o • This does not seem to have the same impact on the • Similar observations as seen at - 7 C and - 15 C : 150 kt , Pair=60 (orange) data • Glaciation more likely at lower air speeds • For a given air pressure, glaciation is more likely for low
What happened when we increased
airspeed to 250 knots at - 25 C: • Later in the day, after we had measured a o several glaciated conditions at - 25 C and 150 knots • Plot at right shows water contents measured by the 3 elements , in between sprays as we increased speed from 150 to 250 knots • We saw lots of ice crystal recirculation.
Most likely we “kicked up” a lot of the ice particles that had been settling around the tunnel loop over the course of the day.
• The ice crystals appeared to “settle out” within about 10 minutes of holding airspeed , which is about as much time as it would take the IRT to get onto condition for the next point. Hence, we do not expect the creation of new ice crystals to be a problem for test points later in the day.
Summary of Results
We measured a total of 27 conditions for which the 2mm/TWC and/or
0.5mm/TWC ratios were less than 11%, indicating a glaciated cloud
• 10 of these showed stable readings from the TWC, 2mm, and 0.5mm
elements, indicating a stable glaciated cloud
• 4 of these showed a step increase about 25 seconds into the spray,
followed by stable reading. Presumably, the step - increase is due to
cloud recirculation that for some reason does not continually
compound.
• 9 of these showed TWC increasing for the first 1 - 2 min while the 2mm
and 0.5 mm remained flat (an effect of ice crystal recirculation), then
the TWC leveled off, suggesting perhaps the cloud reached a sort of
“equilibrium” at the test section
• 3 of these (only at coldest temp and highest airspeed) never leveled
off, but continued increasing over the spray’s duration (not included in
the previous plots)
• 1 spray was started too early after increasing tunnel velocity, and
showed TWC decrease (by about 0.03 g/m , or 5%) for 1 min and then
stabilize
Conclusions
• Still many things that are unknown, but we did learn a few things:
• The IRT can create a fully glaciated cloud by running unheated spraybar
air and water
o This has to happen from the start of a test day, as the air and water cannot be actively cooled.
• Full glaciation was observed for select conditions at : o o Total air temperatures of - 7, - 15, and - 25 C o Airspeeds of 100, 150, and 250 knots o Nozzle air pressures of 40 and 60 psig o MVD values between 13 and 28 μ m • In the IRT, cloud glaciation is more likely at: o Colder total temperatures o Lower airspeeds (suggests that residence time is more important than static temperature) o Higher nozzle air pressures o Smaller drop sizes • Nozzle air pressure was also shown to be a greater driver for glaciation than drop size Remaining Work:
• Check repeatability of these conditions
• Characteristics of the spray (is it still stable?)
• Element readings for the spray (is the water content
consistent?)
• Further characterization of the cloud: