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Fig. 1. Schematic view of the testing setup

at the end of the HPC in order to trigger the recording equipment, measure

the shockwave velocity, detect the pressure change and shockwave pattern

history. All sensors are connected to a personal computer via the analog-

digital transducer.

Optical investigation of the flow around the models is conducted

via flat illuminators 260 mm in diameter. Shadow column instruments

(Tepler devices ИАБ-451 were used in this case) provide photo and video

data on the shockwave and boundary layers behavior in the area under

investigation. These data were recorded by means of digital high-speed

video cameras with several thousand shots per second speed. The cameras

were activated by pressure sensors.

The desired rarefaction level in the testing setup segments is achieved

by means of two turbomolecular oil-free vacuum pumps. The high pressure

and low pressure chambers are separated by a copper diaphragm. A system

of blades was used for the uniform and rapid opening of the diaphragm. The

low pressure chamber and the receiver are separated by a thin aluminium

membrane positioned at the nozzle unit entrance.

The shock tube produces Mach 7.0 hypersonic flows in the receiver

segment. A number of experiments were conducted to simulate the flow in

the ramjet air intake. The scaled models have wedge-shaped elements, some

of them blunted. Special cavities on the surface simulate flame holders in

real ramjet ducts [11].

Shock tube experiment results.

Typical readings for pressure sensors

during the experiment are presented in Fig. 2, 3. In this case, the driver

gas is air at 20 bar pressure; the driven gas is air at 100 mbar pressure.

The oscillograph patterns log the pressure changes at 10 cm distance to the

nozzle entrance (sensor

C

, Fig. 1). The first jump (

1

, Fig. 2) indicates the

6 ISSN 0236-3941. HERALD of the BMSTU. Series “Mechanical Engineering”. 2015. No. 1