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HPC end wall (the

A

sensor is positioned flush with the left end wall of the

HPC). A short period of time after the diaphragm opening a fall in pressure

is observed which results from the rarefaction waves fan. Further jumps

indicate perturbation reflected from the LPC end wall and its subsequent

reflection from the HPC end wall.

The next two oscillograph patterns (Fig. 3

b, c

, sensors

B

,

C

in Fig. 1)

demonstrate changing pressure in the LPC (the middle and the end part

of the segment). It is visible that the pressure in the middle part of the

segment increases when the initial shockwave passes through sensor

B

.

After approximately 3.3 ms sensor

C

(lower graph) displays reaction to

this perturbation. The further readings of this sensor are similar to the

ones described above (Fig. 2). The next jump in the oscillograph pattern

of sensor

B

(Fig. 1) in the middle of the LPC corresponds to the reflected

shockwave.

The data in Fig. 3 display shockwave interaction caused by the multiple

re-reflection of rarefaction jumps within the shock tube volume. Due to

this behavior several time intervals which can be regarded as quasi steady

can be identified. Some of these intervals being several milliseconds long

can be used for measurements.

Results of the experiments on hypersonic flow in the receiver.

Shadow images of the driven gas flow around the models were recorded

by high-speed video cameras and Schlieren optical system. Fig. 4 presents

hypersonic flow near the 10

wedge and 5

semi-wedge. The initial

conditions were the following: driven gas in LPC was air at 1 mbar

pressure, the driver gas in HPC was air at 36 bar pressure, pressure in the

receiver segment was 4. . . 10 mbar. The 10

wedge was positioned so that

its central longitudinal axis and the nozzle symmetry axis coincided. The

distance between the models was 15 mm.

The air flow with the constant Mach number (Fig. 4

a

) lasts for about

15 ms. Then the flow parameters at the nozzle entrance change, with

Fig. 4. Hypersonic air flow (

a

) and its subsequent perturbation (

b

); images from the

shadow video sequence

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