Chapter 1214 Is the total temperature of the wind tunnel not enough?
For the entire hypersonic weapons project, the double-cone air-launched ballistic missile planned by Chang Haonan is only a verification project after all.
Although many unexpected problems were solved during the development process, in terms of the ultimate goal of "weaponized application", we certainly cannot pin our hopes on a model that uses cryogenic liquid propellant.
In the long run, the future of hypersonic weapons will still be a standard waverider or waverider-like shape, powered by a scramjet engine.
Therefore, the High Temperature Gas Dynamics Laboratory, which is responsible for the research and development of the JF14 ultra-high-speed wind tunnel, is also carrying out intensive work...
Several JF series wind tunnels are behemoths with a total length of hundreds of meters and an exit diameter of several meters. They cannot be installed directly in a room in the Institute of Mechanics like the previous JF-X scaled-down wind tunnel.
Therefore, for the sake of safety and confidentiality, about half a century ago, the ultra-high-speed wind tunnel R&D team led by Mr. Guo Yonghuai established a wind tunnel base in Huairou, a suburb in the northern suburbs of Beijing, with the support of Nie Shuai.
In the following decades, it gradually developed into the National Key Laboratory of High Temperature Aerodynamics for Aerospace Flight.
All the ultra-high-speed wind tunnels that have been built are within this science city.
Of course, it also includes JF14 which is under construction-
After successfully verifying the correctness of the analytical solution to the two-dimensional Chapman-Jouguet combustion equation about half a year ago, Jiang Zonglin quickly completed the design of a series of wind tunnel auxiliary systems and initially determined the shock wave reflection cavity and auxiliary detonation section. related parameters.
However, the C-J equation can only solve the design problem of the detonation drive section, and it is impossible to directly present the entire wind tunnel on paper.
Designing it is one thing, being able to work safely is another.
The final design airflow temperature of JF14 exceeds 8000K, and the possibility of upgrading to more than 10000K is reserved in the future.
Even though mechanics has been at the forefront of the world in the field of ultra-high-speed wind tunnels, there is still little understanding of wind tunnel conditions in this temperature range.
Coupled with the millisecond-long test duration, the entire project has entered an almost completely unknown territory...
…
Beijing, Huairou.
Jiang Zonglin''s design and R&D team is gathering around a huge wind tunnel console, and as usual starts the whole day''s work with a morning meeting.
However, the one sitting in the middle today is Academician Yu Hongru.
Jiang Zonglin himself stood beside the wall with a curtain, introducing the specific progress of the wind tunnel research and development work:
"The working principle of the JF14 wind tunnel is to generate a high-temperature and high-pressure gas source for the nozzle flow through the reflection of the incident shock wave at the end of the driven section. The end reflection of the incident shock wave does increase the pressure and temperature of the experimental gas, but it also brings The large entropy increase brings additional uncertainty to the experimental results.”
"In addition, the two-stage reflection of the shock wave reflection cavity and the auxiliary detonation section also significantly increases the ultimate load of the wind tunnel. In fact, only from the perspective of the detonation drive section, for experiments with the same pressure and speed in the shock tube The unsteady expansion of gas through shock waves can transfer part of the energy of the rear gas to the front gas, thereby further increasing the kinetic energy of the front gas. "
"But under the condition of ensuring the safety of the wind tunnel structure, the maximum speed of the experimental air flow that can currently be tolerated is about 6km/s, and the total temperature is 8500K..."
“…”
Academician Yu, who was sitting in his seat, pondered for a long time before slowly nodding his head:
"Currently, it is possible to achieve a total temperature of 8000K and a flow velocity of 6km/s, which is sufficient for Academician Chang''s application needs. As for the enthalpy increase of shock wave expansion that you mentioned later, the theoretical and engineering research is still there. It’s not quite sufficient. The most important thing at the moment is to verify and test each individual system and the main structure of the wind tunnel.”
"I see that you have already tested the gas source, heating, vacuum, decompression and other systems, but before today''s full load test of the detonation drive section, there are still a few details that need to be finalized..."
Under the command of the retired academician, the entire project team worked in an orderly manner.
Wind tunnels, especially ultra-high-speed wind tunnels, are an out-and-out "it''s cool to start up and prepare for the crematorium".
It is impossible to wait and turn on the machine like JF-X in a large wind tunnel.
Take the air source system as an example.
A test that lasts only milliseconds or even microseconds requires the air compressor to work continuously for at least 250-300 minutes.
And after each test, inflation needs to be repeated.
And if you want to conduct multiple tests in a row, you need to let the air compressor equipment cool down for a period of time in between.
Counting all the steps, even if the staff works day and night, they can only conduct less than three rounds of testing on average every day.
Therefore, you must be cautious every time you start. It was not until noon that day that the technicians completed various inspections and returned to the well-protected wind tunnel control room—
Even a small wind tunnel the size of JF-X does not allow anyone to be on site during startup.
Not to mention these behemoths with a total temperature of several thousand K.
Soon, Shen Shenghui, the operator at the first station, reported:
"The air source system reports that the air compressor has been running for 288 minutes and the air source pressure is 47.93Mpa, which has reached the set range..."
"Heating system report, preheating time 210 minutes..."
"Vacuum system..."
"Ignition system..."
“…”
As a series of reports sounded, the three rows of indicator lights on the screen in front of me changed from red to green one by one, which meant that the starting conditions had been met.
Academician Yu Hongru stood behind his favorite protégé, stretched out a hand and gently pressed on the former''s shoulder, and took a slow and deep breath:
"ignition!"
The ignition device of JF14 is a key.
After hearing Academician Yu''s voice, Jiang Zonglin, who was already ready, suddenly turned the key handle and made a "click" sound.
Immediately afterwards…
Calm, of course.
The working process of the wind tunnel is ignition, detonation, and blowing in an instant. What''s more, the control room is far away from the detonation drive section, and of course it cannot be affected by the wind tunnel under normal working conditions.
Only the numerous parameters on the display quickly began to jump.
It wasn''t until the entire operating state was over and several pressure-time curves returned to zero that people with sharper ears could hear a faint "pop" sound.
The three rows of indicator lights are still green, indicating that there are no abnormalities in all systems involved in this test.
This made Jiang Zonglin, who had always been a little worried about the structural strength of the cave, finally breathe a sigh of relief:
"Attention to all systems, prepare for cooling and decompression..."
While issuing follow-up instructions, he skillfully selected the working data of the wind tunnel and prepared to organize and export it.
And just when everyone thought everything was fine, Jiang Zonglin suddenly felt that the hand on his shoulder trembled suddenly, and then squeezed hard...
Before he could make a sound from the pain, he heard Academician Yu''s slightly urgent voice behind him:
"etc!"
Everyone immediately stopped what they were doing and turned to look in the direction of the general podium.
"The total temperature data at the drive section outlet is wrong!"
Almost at the same time as Yu Hongru finished speaking, Jiang Zonglin had already seen the total temperature calculation results on the screen.
“7565K…”
Although from the perspective of word play, this number can barely be called "8000K level".
But everyone knows that the total temperature value determined by this test should be around 8300K.
The difference is nearly 10%, which is obviously difficult to be treated as a simple test error.
For a moment, the atmosphere in the entire control room became tense because of this value...
(End of chapter)