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P. Liu
overall stability of the airflow to prevent air liquefaction in the test section,
which belongs to the category of hypersonic wind tunnel. If the Mach
number ranges from 0.8 to 1.4, the wall of the test section should be
perforated or grooved (ventilation wall), which belongs to the category of
transonic wind tunnel. Supersonic wind tunnel generally has no heater,
and the test section is a solid wall (no holes, no grooves). Different from
low-speed wind tunnel, two basic conditions must be met to obtain supersonic flow: contraction–expansion nozzle and the area ratio between throat
section and nozzle outlet section must be changed to change the experimental Mach number; the ratio of pressure in the stable section to the
pressure at the outlet of the diffuser section should be large enough and
increase with the increase of the experimental Mach number. When the
air expands to supersonic velocity, the temperature drops sharply and the
moisture in the air condenses in the test section. In addition, a supersonic
diffuser is usually used in supersonic wind tunnels, especially when the
Mach number is high. These are all different from low-speed wind tunnels.
A supersonic wind tunnel with the same test section size requires much
more drive power than a low-speed wind tunnel. It is generally believed
that the test section size equal to or less than 0.6 m or so belongs to a small
supersonic wind tunnel, while the test section size of 1 m or so belongs
to a medium supersonic wind tunnel. This division is not very strict, just
a general reference. Supersonic wind tunnels first appeared in the 1920s.
Many of the world’s large supersonic wind tunnels were built in the 1950s.
For example, the world’s largest supersonic wind tunnel (the test section
of 4.88 m × 4.88 m, Ma = 1.5–4.75) was built in the United States
around 1956. The development trend of the supersonic wind tunnel is
to improve the performance of the existing wind tunnel and improve the
technical level of measurement and control. In order to study the drag
reduction technology in supersonic flight, a supersonic wind tunnel with
low turbulence and low noise needs to be built.
Supersonic wind tunnel is divided into continuous type and transient
impact type. The continuous supersonic wind tunnel, like the general lowspeed wind tunnel, works continuously, the experimental conditions are
easy to control, the experiment is not limited by time, but the power
equipment should be quite large. According to the different ways of generating pressure ratio, the transient supersonic wind tunnel can be divided
into blowing type, inhaling type, ejecting type, blowing-suction type, and
blowing-leading type. The working process of the transient supersonic
wind tunnel is as follows: prior to the operation of the wind tunnel, the
air is pumped into the gas cylinder. When the air pressure in the cylinder
P. Liu
overall stability of the airflow to prevent air liquefaction in the test section,
which belongs to the category of hypersonic wind tunnel. If the Mach
number ranges from 0.8 to 1.4, the wall of the test section should be
perforated or grooved (ventilation wall), which belongs to the category of
transonic wind tunnel. Supersonic wind tunnel generally has no heater,
and the test section is a solid wall (no holes, no grooves). Different from
low-speed wind tunnel, two basic conditions must be met to obtain supersonic flow: contraction–expansion nozzle and the area ratio between throat
section and nozzle outlet section must be changed to change the experimental Mach number; the ratio of pressure in the stable section to the
pressure at the outlet of the diffuser section should be large enough and
increase with the increase of the experimental Mach number. When the
air expands to supersonic velocity, the temperature drops sharply and the
moisture in the air condenses in the test section. In addition, a supersonic
diffuser is usually used in supersonic wind tunnels, especially when the
Mach number is high. These are all different from low-speed wind tunnels.
A supersonic wind tunnel with the same test section size requires much
more drive power than a low-speed wind tunnel. It is generally believed
that the test section size equal to or less than 0.6 m or so belongs to a small
supersonic wind tunnel, while the test section size of 1 m or so belongs
to a medium supersonic wind tunnel. This division is not very strict, just
a general reference. Supersonic wind tunnels first appeared in the 1920s.
Many of the world’s large supersonic wind tunnels were built in the 1950s.
For example, the world’s largest supersonic wind tunnel (the test section
of 4.88 m × 4.88 m, Ma = 1.5–4.75) was built in the United States
around 1956. The development trend of the supersonic wind tunnel is
to improve the performance of the existing wind tunnel and improve the
technical level of measurement and control. In order to study the drag
reduction technology in supersonic flight, a supersonic wind tunnel with
low turbulence and low noise needs to be built.
Supersonic wind tunnel is divided into continuous type and transient
impact type. The continuous supersonic wind tunnel, like the general lowspeed wind tunnel, works continuously, the experimental conditions are
easy to control, the experiment is not limited by time, but the power
equipment should be quite large. According to the different ways of generating pressure ratio, the transient supersonic wind tunnel can be divided
into blowing type, inhaling type, ejecting type, blowing-suction type, and
blowing-leading type. The working process of the transient supersonic
wind tunnel is as follows: prior to the operation of the wind tunnel, the
air is pumped into the gas cylinder. When the air pressure in the cylinder