Chapter 1215 Where did the energy go?
In fact, according to general engineering experience, if a parameter of a large-scale equipment is found to be 10% lower during the first test, this is a normal situation in the design process.
There should be excess margin left.
Especially for data like total temperature, it is actually better to be lower than higher.
At least it's safe.
Including several JF series wind tunnels that have been built in the past, they all went through multiple rounds of design adjustments before gradually approaching the original design values.
However, JF14 adopted a rigorous analytical solution of the second-order CJ equation during its design, rather than relying on a combination of numerical calculations and experience as in the past.
Therefore, at least in the two core units of detonation drive and shock wave reflection, the final error should be relatively small.
After looking at each other in bewilderment, everyone in the control room focused their attention on Jiang Zonglin and Yu Hongru behind the command desk.
After all, they are the only ones who can make the final decision.
"Take a look at the airflow expansion data."
Yu Hongru did not make a decision immediately.
As for the wind tunnel test, no matter how urgent it is, it won’t take just a few minutes.
Soon, Jiang Zonglin brought up a pressure signal-time curve on the computer screen, with the fluctuation amplitude first weak and then strong.
"The center of the wave is 740.3mV, the corresponding airflow speed is 6175m/s, and the duration is about 125ms..."
As he reported several key data on the graph, his brows relaxed slightly:
"The airflow data is normal... The duration of this steady state is even slightly better than we expected, and the pressure fluctuation is also very small."
Yu Hongru, who was standing behind him, also looked much better and nodded repeatedly:
"Well...it is indeed far ahead of similar expansion wind tunnels in other countries."
Although this is a completely factual judgment, if it comes from Jiang Zongli's mouth, it may sound like bragging.
As the other party's teacher, he had no such concerns at all.
The almost frozen air in the control room relaxed a little as a result.
However, Jiang Zonglin's expression soon became a little confused:
"If that's the case, then it means that the calculation method given by Academician Chang and the design steps we have determined should be fine, but the only problem is the total temperature..."
"..."
He sighed softly as he spoke, flipping through the notebook lying next to him, but his movements seemed somewhat aimless.
He had never seen such a situation in his nearly thirty years of research career.
I really don't know where to look for a solution.
Yu Hongru, who was more experienced, put his hands behind his back, lowered his head and paced back and forth without saying a word.
Obviously thinking too.
A few minutes later, he stepped out with a thud, then stopped:
"Well... first check the sensors related to the total temperature to make sure it's not a problem with the measurement process itself."
Having said that, in order to ensure data reliability, the wind tunnel uses a dual backup system for core sensors such as pressure and temperature.
If the results of the three measurement systems differ too much, the system will directly report an error instead of mechanically giving a meaningless average.
Therefore, Yu Hongru did not expect to solve the problem by this trick, but continued:
"If the sensor is fine, after the cooling and pressure relief process is over, have the technicians go to the site to check the structure of the cave. If it is determined that there are no safety hazards, then increase the parameters by 3% in the next test to see what changes will occur in the total temperature..."
Sometimes it is really hard to explain things related to engineering.
But the problem always needs to be solved.
Under the premise of ensuring safety, work must always continue to proceed as planned.
Moreover, all data except the total temperature are normal, which is indeed beyond past experience.
Of course, to be on the safe side, he did not raise it by 10% in one go.
Instead, I decided to give it a try first.
……
Following the order from Academician Yu, the entire project team started moving again.
As a forward detonation driven wind tunnel, although the additional shock wave reflection chamber and auxiliary detonation section of JF16 added a lot of difficulty to the design process, they were originally part of the detonation driven section, so the subsequent maintenance and inspection are slightly easier than some of its predecessors.
Therefore, everyone quickly and easily completed all the requirements.
Wind tunnel structure, all safe!
This conclusion made Jiang Zonglin feel relieved. He raised his wrist and looked at his watch:
"Let the comrades take a break. The second round of testing will be carried out on time at 3 pm!"
The operation of the wind tunnel is completely automated and does not require any physical work, but it is still not easy to concentrate for a long time.
However, after giving the order, Jiang Zongli did not go to rest himself.
Instead, he closed the notebook that he had almost turned to the last page of, and then opened it again.
Don't start from the first page.
Instead, he directly found a position in the middle...
His thoughts were in a mess just now, and reading his notes was just a habitual action to relieve stress.
Now that I have calmed down, I suddenly realize that I might be able to find some ideas from the solution to the two-digit CJ equation that I wrote down earlier...
It's a shame, though.
Although his understanding of the contents of the notes had deepened a lot, he still couldn't see any clues until the second test was ready that evening.
Academician Yu, who was nearly 80 years old, could no longer hold on and was helped down to rest a few hours ago.
Therefore, this time the command can only be given by Jiang Zongli himself.
It’s fun to test again.
Several hours of preparation, just for less than a second of work.
"ignition!"
While Jiang Zonglin was shouting the command, another operator turned the key and started the JF16 wind tunnel for the second time.
Aside from a few setup parameters, everything is the same as last time.
It even seems a bit monotonous.
Select data, export, process and analyze...
No additional instructions are required and the subsequent work can be completed in a few minutes.
But the result...
"The pressure signal at the outlet of the drive section is 745.3mV, the corresponding air flow velocity is 6356m/s, and the duration is about 122ms..."
The operator just now quickly reported a string of data.
Jiang Zonglin calculated the result in his mind almost at the same time, and the air flow speed was indeed increased by about 3% compared to the last time.
A moment later, the other party continued to give the number that everyone was most concerned about:
"Total temperature...7657K."
The total airflow temperature is not measured directly, but calculated through many other data.
Therefore, for those who are not experienced enough, the results will be a little slower.
"..."
Jiang Zonglin's heart suddenly skipped a beat.
Then he picked up the calculator from the side and pressed the numbers quickly.
His mental arithmetic was correct:
"The total temperature has increased by about 1% compared to before..."
Although other people couldn't see the numbers on the small LCD screen, Jiang Zonglin still turned the calculator 180° to show the results to everyone.
"The input parameters have been increased by 3% in accordance with Academician Yu's request just now. This is absolutely correct."
Operator No. 2, who was sitting at the other end of the room, spoke with conviction.
He is responsible for the final check of the set parameters before ignition.
"The calculation accuracy of the total temperature in the wind tunnel can be controlled within plus or minus 25K, which means that as long as the parameters are increased, the total temperature in the wind tunnel and the airflow velocity will increase accordingly, and there is no problem in the qualitative trend."
Jiang Zonglin stood behind the screen showing the results and analyzed slowly:
"But the total temperature increase is only about one-third of the calculated range..."
"That is to say, in this process, some of the energy...disappeared?"
