The vitiated Mach 4.7 enthalpy tunnel complements the new hypersonic facility (described separately). It has been used for supersonic combustion of hydrogen and/or liquid and gaseous hydrocarbon fuels at isolator Mach numbers ranging from 1.3 to 3.6. The 1 x 1 in. (2.5x2.5 cm) cross section test-section is instrumented with pressure ports and thermocouples and has ample optical access via quartz windows for visualization and laser-based diagnostics. Different injection schemes have been used for studies of flameholding or injection/mixing analyses. For liquid fuels, a separate heater is available to raise the fuel temperature up to 550K. Compressors output continuously up to 3.5 lb/s (1.6 kg/s) with stagnation pressures up to 200 psia (1.4 MPa).
This 1” x1” (2.5x2.5 cm) cross section test chamber has been used for studies of conjugate species concentration/wall heat transfer for mixtures of hydrogen-oxygen and hydrogen-air combustion at elevated pressures up to 900 psi (6 MPa). A coaxial injector of 75% the size of the main shuttle engine has been used to date. A study of OH PLIF measurements uncertainty evaluated 18 parameter concluding that the largest sources of error derive from uncertain local temperature (up to 15%) and laser shot-to-shot (up to 11%).
This facility is used for studies of subcritical-to-supercritical jet disintegration and mixing. It is 9 inch (230 mm) long and has a 1.8” x 1.8” (46x46 mm) inner cross-section. Optical access is provided through four symmetrically located, 3.3” x 0.9” (84x22 mm) fused silica windows. The chamber can be pressurized up to 1030 psi (7 MPa) at 620K. The injected liquid is pre-heated independently up to 675 K. Using a fluoroketone, current studies focus on subcritical to supercritical jet disintegration in single and dual species compounds, with chamber environment from subcritical to supercritical. These conditions appear in a broad range of applications ranging from rocket to diesel to scramjet engines.
This facility consists of two concentric tubes where the outer surface of the inner tube is covered with a catalyst. The inner tube contains a cooling air flow while the annular region contains a fuel-air mixture that reacts on the catalytic surface. The inner and outer air flows can be independently controlled by a number of massflow controllers from Alicat, allowing equivalence ratios and fuel composition to be varied over a wide range. The incoming air streams can also be preheated through passing through two independently controlled electric heaters, allowing the conditions in a RQL low-NOx gas turbine pre-combustor to be modeled. Measurements are carried out using mass spectrometry of gas samples drawn from above the catalyst surface and through laser-based diagnostics through the fused-silica windows of the test section.
The cavitation tunnel is filled with a volatile fluoroketone for studying cavitation under near-critical conditions. This fluoroketone, like cryogenics, belongs to a class of fluids with thermosensitive properties; hence, the fluoroketone – unlike water which is more commonly used - simulates cavitation modes of cryogenic fluids. The tunnel is capable of reaching a speed of 33 fps (10 m/s) in its 4” x4” (0.1x0.1 m) cross section test section, enabling high-Re tests under different angles of attack. Currently a NACA 0015 hydrofoil is the test object. The tunnel is driven by a variable-speed 25 hp pump and is fitted with large windows facilitating the application of optical diagnostics, primarily PLIF. With a dedicated pulsed Nd:YAG laser and a rotating-mirror image acquisition system, frame rates of 100- 10,000 Hz are possible. The tunnel is constructed of aluminum and may be vacuumed or pressurized up to 75 psia (5 bar). It is equipped with a 7.5kW heater and a chilled water system facilitating the investigation of both pressure and temperature effects. Furthermore, by lowering the fluoroketone temperature cavitation modes met in water – the material used in most studies elsewhere – can be modeled.
The MAE department Mach 1.5-4 wind tunnel has a 6” x 6” inch (15 x15 cm) test section equipped with a sting with variable angle-of-attack as well as a Schlieren setup, a PSI9010 pressure scanner and additional pressure transducers. The wind tunnel has access ports for secondary air injection or bleed. Using the air storage tanks and high-pressure single-stage screw compressors, 30 s runs can be carried out approximately every 5 minutes at Mach 3.8. This facility was used most recently used for tests of fuel injection in supersonic inlets and inlet instabilities for pulse detonation engines.
The 4 inch (10 cm) diameter, double-diaphragm, shock tube generates shocks of up to Mach 5 strength. Two test sections are available at the end of the 6 m driven section. The combustion test section, separated by a thin mylar diaphragm from the driven section, is used to measure ignition delay times of premixed gases in the range of 800-2400 K using the reflected shock. CH and OH emissions can be detected by a Hamamatsu R374 photomultiplier using the appropriate narrowband filters. The second test section has a square cross section with optical access and is used for studying shock-droplet interactions and ignition using high-speed cameras.
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