| Category | Description |
|---|---|
| Responsible | Prof. a. D. Dr.-Ing. Rolf Radespiel |
| Mach 6 nozzle | Extended Mach 3 nozzle | |
| Max. Mach | 6 | 3 |
| Run time | 80-100 ms | 65 ms |
| Reynolds number | 3 - 20 million | 1.5 - 17.5 million |
| Total pressure p0 | 3 bar - 30 bar |
| Total temperature T0 | 500 K |
| Test section diameter | 0.5 m |
| Overall length | 26 m |
| Tube length x diameter | 17 m x 0.22 m |
| Vaccum tank volume | 6 m³ |
| Total el. power | 20 kW |
The Ludwieg tube HLB is a long pipe with a converging - diverging nozzle, from which the flow exits into the test section, diffuser and dump tank. A fast-acting valve is placed just before the nozzle. When the valve opens, an expansion wave travels upstream into the storage or driver tube. The expansion wave reflects at the tube end and runs back until it again reaches the nozzle. This limits the period of time during which one can observe quasi steady flow conditions in the nozzle and the hypersonic test section. Due to its simple flow scheme the Ludwieg tube generates high speed flows with high flow quality without the need to install a total pressure control device and a large settling chamber as with conventional blow-down facilities. The electrical power requirement of this wind tunnel is remarkably low and such are the total operating costs.
The diverging nozzle is carefully contoured, as an example the opening of half angle for Mach 6 nozzle varies from initially 7.5° to 3° at the nozzle end. That is, some flow expansion is maintained into the test section in order to keep the nozzle flow insensitive to deviations of the design point. Comparisons of flow computations and measurements in the test section confirm that the non- uniformity of the pitot pressure in the core flow is about than +/- 1.2% which corresponds to Mach number variations of +/- 0.6%. The test section itself is a tube with constant diameter. A cavity is attached to the bottom, which contains the two-component traversing mechanism. Optical access is achieved using windows of 0.26 m diameter on both sides and on the top of the test section.
A Mach 3 supersonic nozzle has been designed based on the infrastructure of the HLB. By replacing the Mach 6 nozzle with a Mach 3 nozzle, together with inserting an additional nozzle (1st nozzle length = 0.239 m, 2nd nozzle length = 1. 524 m) and a settling chamber ( length = 1.049 m , diameter = 0.354 m ), the new tunnel succeeds to produce a Mach 3 flow. The Mach 3 nozzle shares the storage tube, test section, diffuser and dump tank with the original HLB. The tunnel inherits the steady stagnation storage tube flow conditions and the high operation efficiency from the HLB. Compared to the preferred hot run of HLB, the Mach 3 tunnel has no problem with condensation at an ambient stagnation temperature, further improving the tunnel efficiency.
The jet simulation facility resembles an Ariane 5 launcher. With this facility, it is possible to investigate afterbody and propulsive jet flows. The working principle is similar to the HLB wind tunnel itself. Outside of the HLB test section is the 32m long heated storage tube. The rocket model is placed along the centerline of the HLB test section. A tandem nozzle consisting of the first nozzle, the settling chamber and the second nozzle, is integrated into the rocket model. After the start of the facility, the flow detaches in the first nozzle and a shock system is generated. Because of this shock system, the flow is decelerated to subsonic speed at the entry of the settling chamber. In the settling chamber, the flow uniformity is improved with perforated plates designed to reduce total pressure and to work as flow straighteners. In the second nozzle which is an axisymmetric Truncated Ideal Nozzle (TIC), the flow is accelerated to Mae = 2.5 at the nozzle exit.