The Icing Research Tunnel (IRT) is the world's largest refrigerated icing
tunnel, capable of duplicating the icing conditions encountered by aircraft by
controlling liquid water content (LWC), droplet size, and air temperature within
the tunnel. The IRT is a closed-loop atmospheric-type tunnel for tests of
low-speed models. The test section is 6 ft high, 9 ft wide, and 20 ft long.
Airspeed in the empty test section can be varied from 43.5 knots to 260.7 knots
(50 to 300 mph). The IRT is scheduled for continuous testing throughout the
year. NASA Lewis is located in Cleveland, Ohio, adjacent to Cleveland Hopkins
International Airport. NASA Lewis is capable of providing complete security for
proprietary or Government classified test programs.
IRT facilities have been used in a number of ice protection roles.
Aircraft ground deicing/ anti-icing fluids were tested on a model of a Boeing
Performance and Capability
The maximum airspeed for an empty IRT test section is 260 knots (300 mph).
Large model blockage (greater than 20 percent) significantly reduces test
section maximum airspeed; for details, contact the IRT Facility Manager. The
tunnel is operated at atmospheric pressure, and the air temperature range is
controlled from ambient temperature to -20 degrees F +
1 degree F. Tunnel
temperature is determined by averaging several thermocouple measurements just
downstream of the cooler.
The IRT uses a centralized exhaust system to simulate airflow for inlet
models. The flow rate can be varied from 3 to 80 lbm/sec (pound mass per
A 25-ft diameter, 12-bladed, fixed-pitch fan of laminated Sitka spruce
provides the airflow. The fan is directly coupled to an electric motor in a
faired nacelle. The 5,000 hp electric motor controls the fan speed to an
accuracy of ~ 0.5 rpm over the fan's range of 50 to 460 rpm. Fan acceleration
rates of between 1 and 10 rpm/(sec squared) are available to simulate aircraft
flight profiles. The acceleration is not the normal mode of operation and such
use must be prearranged and approved.
Test Section Details
The test section is 6 ft high, 9 ft wide, and 20 ft long. The center of the
8.6-ft diameter test section turntable is 11.5 ft from the inlet of the test
section. The turntable rotates +20 degrees horizontally. Model mounting details
and bolt patterns are available upon request. Lift and drag can be measured
using a balance. Just drag can be measured using a traversing wake survey probe.
The test section ceiling hatch, used for model installation, is 4 ft wide by
12 ft long. The hatch contains several remov able panels, which can be used to
mount equipment, or the panels can be replaced with Lucite windows for lighting
or photographic work.
There are four viewing windows between the control room and the test section.
The three electrically heated windows are 2.5 ft wide by 3.75 ft high. The
unheated window is 2 ft wide by 1 ft high.
A large enclosure (the balance chamber) surrounds the test section and
control room and shares the same static pressure as the test section so that
instrumentation leads and service lines can enter the tunnel test section
ceiling or floor without a pressure bulkhead or hermetically sealed connections.
Eight sprays bars containing air-blast nozzles are used to develop a uniform
test section icing cloud environ ment approximately 3 ft high by 4 ft wide. The
LWC varies by no more than +10 percent within the test region. The nozzles
produce water droplets of mean volumetric diameters (MVD's) between 15 and 40
microns with LWC from 0.5 to 2.5 gm/m3. Two nozzle sizes are available: standard
and mod-1. In general, the mod-1 nozzles provide lower LWC. Specific cloud
calibrations are available upon request.
The IRT building is connected to the tunnel's balance chamber by an air-lock
chamber and a 10- x 10-ft model access door. Space for model buildup is avail
able in the shop area.
The balance chamber is a three-story structure. A retractable access door is
located at the side of the balance chamber and has an opening 9 ft wide by 8 ft
high between the shop area and the balance chamber. The second floor of the
balance chamber includes the tunnel test section, the tunnel personnel access
doorway, and the facility control room. The test section model access hatch and
the test section altitude exhaust duct are located on the third floor.
The control room is on the second floor of the balance chamber. Approximately
half of the control room is occupied by facility controls and the Lewis
in-facility data acquisition system (ESCORT). The remainder of the control room
is available for user-supplied equipment.
The IRT is operated by an interactive computer control system. For example,
the system controls fan speed (airspeed), air temperature, spray bar air and
water pressures, spray duration, turntable position, tunnel lighting, and
Instrumentation and Data Recorders
Data can be monitored and recorded by both an in facility computer and a
data-linked remote mainframe. The ESCORT steady-state data system can be
expanded to record more than 500 data channels and all of the data can be
permanently recorded on a data collector for further off-line processing. As
presently configured, the ESCORT system can record 192 analog inputs (i.e.,
temperature, pressure, position). Of these inputs, 92 are reserved for facility
systems monitoring and 100 are available for user designated parameters. In
addition, as part of ESCORT, an electrically scanned pressure measuring system
(ESP) provides an additional 128 channels for user-defined pressure
measurements. Two ESP pressure ranges are available, 5 or 15 psid, and have an
accuracy of +0.1 percent of full scale.
Video and still photographic equipment may be used for recording visual data
and documentation. Side view photos may be taken from the control room, or top
views through the model access hatch windows. Camera system components available
include video cameras with zoom lenses, monitors, and VHS tape recorders. A
high-speed video system capable of 1,000-frame/sec exposure is also available.
In most instances users should provide still camera equipment, film, and
Model Electrical Power
Several power systems are available to the tunnel user. These systems are as
|440 V |
|208 V |
|(This system can be used as single-phase |
208V or as a single-phase 110V.)
|(440 V, 60 Hz converted to 115 V, 400 |
|400 Hz |
|30 A |
|400 Hz |
|15 A |
|28 Vdc |
|(440 V, 60 Hz to 28 Vdc invertor)|
De-icing and Anti-lcing of Models
A 3/4 ton-diameter line provides steam at 40 psig for model and/or
A gas burner outside the IRT provides heated air to the model from 100 to 700
degrees F. In addition, an electric heater can be used to increase the air
temperature to 900 degrees F. The maximum flow rate of the heated air is 1 lbm/sec
at 120 psi. Service or shop air nominally at 125 psig is available for the model
Model Stress Analysis and Testing
Tunnel users must perform a detailed stress analysis on their model and
support systems and provide it to the IRT Facility Manager. A series of
aerodynamic tests must be performed in the IRT on the model prior to icing
tests. These tests will be conducted by IRT personnel who will approve the model
for icing tests if it performs satisfactorily.
Charge for Tunnel Use
The tunnel time charged to users includes the total time that the facility is
available to the tunnel user. This time includes model and instrumentation
installation and removal (including crating for shipment), experiment time, and
the time required to return the tunnel and associated area to its pretest
condition. Crating and shipping both to and from the IRT is the responsibility
of the user.
The occupancy charge to use the facility is set by LeRC and is reviewed on a
case-by-case basis and varies depending on services, equipment, and supplies
necessary to perform the test. There are four basic types of working agreements
NASA Test Program
NASA/lndustry Cooperative Program (Nonreimburs able Space Act Agreement)
Other U.S. Government Agency Program (Reimburs able or Nonreimbursable
Industry Proprietary or Noncooperative Program (Re imbursable Space Act
In most instances, tunnel users should be prepared to provide necessary
technicians, mechanics, tools, spare parts, special equipment, and supplies to
perform model installation in the tunnel. In some circumstances these NASA LeRC
resources may be used at a charge to the customer.
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