Hypersonic wind tunnel
A hypersonic wind tunnel is a test facility in which flows can be generated at hypersonic speed - with pronounced boundary layer influences, zones with high losses and high overall temperatures. The achievable speeds are in the range between Mach 5 and 15. The required drive power of a wind tunnel increases with the cross-section, the density and the third power of the test speed. Therefore, closed, continuously operable wind tunnels require considerable investments.
Technological development
The first appropriately designed Mach 7-10 wind tunnel system with a 1x1 m test section and 57 MW hydraulic drive power was planned in Kochel am See during World War II . It was commissioned as 'Tunnel A' at the Arnold Engineering Development Complex (AEDC) in Tullahoma , Tennessee , USA in the late 1950s . As an alternative to these complex, large-scale systems, so-called blow-down wind tunnels are used for brief simulation of hypersonic flows.
The main components of hypersonic wind tunnels are flow heaters and coolers, an air drying system, a convergent / divergent nozzle in front of the actual test section with a subsequent second constriction and a subsequent diffuser . While the flow channel of an open, intermittently operated blow-down channel is closed by a large vacuum reservoir, the hallmark of closed hypersonic wind tunnels is instead an extensive high-performance compressor system. To 'start' the hypersonic wind tunnel system, high total pressure ratios are required until the compression shock configuration is pushed into the area after the second bottleneck. Hypersonic wind tunnels sometimes work with very high pressures, depending on the simulation altitude, and due to the sharp temperature drop in the flow during expansion in the nozzle, it is also necessary to preheat the gas in order to avoid liquefaction . Due to the high temperatures, the material stress is critical, so that cooling of the nozzle may be necessary.
A German manufacturer of such systems is HST (Hyperschall- & Strömungstechnik) GmbH in Duderstadt, founded in 1997 .
Technological problems
The following points are decisive when designing a hypersonic wind tunnel :
- Supply of gas of high temperature and pressure for the necessary test duration of a blow-down channel
- Accuracy of the initial conditions and thus reproducibility of the measurements
- Failure of the structure due to overheating
- Sufficiently fast measurement data acquisition and instrumentation
- power supply
Example: The generation of a flow that corresponds to 5.5 km / s at an altitude of 45 km would require temperatures of around 9000 K and a pressure of 3 MPa (30 bar).
Facilities
The currently most powerful wind tunnel is the LENX-X ; it is located in the USA (Buffallo, New Yourk) and reaches speeds of up to 10 km / s (30 times the speed of sound or Mach 30).
In China is the JF12 , which can simulate speeds between Mach 5 and Mach 9 at altitudes between 20 and 50 kilometers. A system is being built that will generate speeds of 12 km / s (Mach 35) after completion in 2020.
In India, the Vikram Sarabhai Space Center (VSSC) operates a hypersonic wind tunnel in Thiruvananthapuram as part of ISRO .
In France, the CNRS Institute ICARE in Orléans operates the hypersonic wind tunnel MARHy (Soufflerie à Mach Adaptable Raréfie Hypersonique).
The most powerful German hypersonic wind tunnel is the H2K of the supersonic and hypersonic technologies department at the Institute for Aerodynamics and Flow Technology (AS-HYP) at DLR with speeds of just over Mach 11. The following topics are dealt with here:
- Investigation of supersonic inlets: inflow to the engine inlet during flight maneuvers;
- thermal loading of components: design of radomes;
- Flight stability and controllability;
- Physical flow processes with lateral thrust control through external combustion.
See also
Web links
- Mach14 Free Piston Hypersonic Wind Tunnel Longshot at the Von Karman Institute of Fluid Mechanics
- Wind tunnel systems from the DLR wind tunnels department
Individual evidence
- ↑ [1] , Eckardt, Dietrich: "The 1x1 m hypersonic wind tunnel in Kochel / Tullahoma 1940-1960", German Aerospace Congress Augsburg 2014.
- ↑ https://www.hst-hft.de/hst-gmbh/windkanaele/hyperschall-windkanaele/ , accessed on February 14, 2019
- ↑ https://www.scmp.com/news/china/policies-politics/article/2120072/china-builds-worlds-fastest-wind-tunnel-test-weapons , accessed on February 12, 2019
- ↑ https://www.vssc.gov.in/VSSC/index.php/isro-centres?id=207 , accessed on February 14, 2019
- ↑ http://icare.cnrs.fr/mediatheque/marhy1/ , accessed on February 14, 2019
- ↑ https://www.dlr.de/as/desktopdefault.aspx/tabid-194/407_read-576/ , accessed on February 7, 2019
- ↑ https://www.dlr.de/as/desktopdefault.aspx/tabid-194/407_read-5437/ , accessed on February 14, 2019