Mach 4 Blow-Down Facility (M4BDF)

Mach 4 Blow-Down Facility (M4BDF)

The Mach 4 Blowdown Facility (M4BDF) is used for the screening of hypersonic and supersonic inlets that would be further developed in other research facilities. Probe calibration tests and other research activities that require Mach 4 test conditions are also conducted. The facility nozzle is two-dimensional that opens into a 9" x 9" square test section. A one foot long plate, that spans the test section, can be installed near the front of the test section at one of several "y" positions and provide a simulated forebody boundary layer entering an inlet. A 2.00" wide by 2.75" high rectangular flowmeter is frequently used to provide backpressure and unstart inlet models during tests. The test medium is ambient (unheated) air. A muffler reduces noise external to the building, as the facility exhausts to the atmosphere.

Inlet models up to 3 feet in length that block up to 13% of the flow area have been tested in the facility. One wedge model successfully blocked over 21% of the flow and still permitted the tunnel to start. Models are usually made of aluminum although stainless steel is sometimes recommended for parts that must maintain sharp leading edges.

The current instrumentation system includes a PSI 780-B electronic scanning pressure measurement system capable of recording 96 channels twice a second. Five analog channels are merged into the data with an IBM compatible PC that is also capable of post processing and plotting the data. The presssure data is routinely sent to a second IBM compatible PC to provide real time distribution plots. A Schlieren system is available as well as VHS camera and recording capability. Various oil flow visualization techniques have also been used in the test section. Tunnel access locations are available upon request. Trexler, Carl A.

Location:             NASA Langley Research Center

Test section:         9" x 9", 2-D nozzle approximately 15" long.  Models can
                      be extended.  The max. length of a single piece (2"x4")
                      is 30",  A 12" long flat plate, ahead of the test
                      section, can be installed.

Max. blockage:        Approx. 13%, provided the model has supersonic inlet
                      characteristics (i.e. no blunt leading edges).
                      Note: Some models can have higher blockages.

Mach no.:             4.03.

Test medium:          Air.  Test air is dry but model can become wet
                      between tests.


Instrumentation:      Currently 96 ESP pressure channels, and 5 analog
                      channels including tunnel total pressure.  (Data is
                      nominally read either once or twice a second, but a new
                      data system can read all channels over 10 times a second.)

Flow view:            Schlieren system.
                      VHS camera, cassette recorder and PC screen capture.
                      Various oil flow techniques.

Data systems:         IBM PC compatible Pentium Pro-200, 2 Gbyte hard drive.
                      IBM PC compatible Pentium III, 450 mhz, 13 Gbyte hard drive.

Data analysis:        Quick basic programs permit plotting of quick-look data
                      immediately after each test.  Plots = f(time or distance).
                      Data stored on Hard disk in ASCII format.

Below is a schematic of a model in the test section of the M4BDF.

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Last updated: Thursday, August 14, 2008 14:48