At the same time, Yao Mengna was sitting on a chair in the corner of the control room, almost out of everyone's attention.

On the surface, she seemed to be staring at Chang Haonan's side face in a daze.

Well, it actually does.

But the reason for being in a daze is not that he is attracted by the latter's appearance and becomes a nymphomaniac.

Instead, after witnessing the high-altitude test process just now, an inspiration flashed through her mind.

But I didn't have time to catch it.

I just vaguely felt that the inspiration just now was related to my junior brother.

Yao Mengna believes that visual stimuli can stimulate the subconscious, which can remind oneself of something useful.

Well, it's all for scientific research.

Anyway, when she really recaptured the inspiration a few minutes later, she even felt a little stunned.

Damn, I can't find any other excuse to deceive myself......

"Forget it, it's important to get down to business."

Yao Mengna shook her head slightly, put aside the chaotic thoughts in her head for a while, then stood up and silently walked along the edge of the room to the computer that recorded the test data.

In fact, on the way off the plane, she was thinking about the unstable working condition of the turbojet 14 that Chang Haonan said before.

And now she has a less mature, but logically self-consistent guess.

It's just that some data is needed to corroborate it.

Soon, she found that inconspicuous project from the vast sea of records-

Combustion chamber outlet temperature/pre-turbine temperature.

"Good."

Yao Mengna, whose eyes were glued to the screen, raised the corners of her mouth slightly and muttered softly.

However, the excitement lasted only a moment.

After clicking in and checking it out, she found that the data was incomplete.

This indicator is very important in the design and manufacture of combustion chambers and turbine blades, but it is generally not important in high-altitude testing.

The main thing is that it is really not easy to measure.

The accuracy of non-contact measurement is not high, and the technology is not mature enough, and even the engine needs to be modified for testing.

The contact temperature measurement needs to insert armored thermocouples, one or two is fine, but if you want to obtain a complete temperature field, then there will be many points that need to be measured, and a large number of thermocouples themselves will interfere with the internal flow field of the engine and affect the working state.

Therefore, as long as the core indicators such as the intake air flow and thrust of the engine are normal, and there is no problem with the turbine operation, the pre-vortex temperature will not be measured frequently.

At most, the data of 1-2 sampling points is given as in front of us to ensure that there will be no accidents due to overheating.

But she needed more comprehensive data.

After a few seconds of hesitation, Yao Mengna finally decided to talk to Chang Haonan about it first.

With the lessons learned from the last blade opening design, she won't allow the project to be delayed again.

"Senior brother." Yao Mengna bypassed the crowd that had just finished celebrating and came to Chang Haonan:

"I would like to do a holistic measurement of the pre-turbine temperature field in the middle of the later air performance tests."

"Pre-turbine temperature?"

Chang Haonan looked up at Yao Mengna in front of him, then quickly flipped through the report in his hand, and quickly found the page with the corresponding data.

"The maximum temperature before the turbine is 1575K, which does not seem to exceed the design tolerances, and in terms of the overall operation of the engine, it is also ......"

Halfway through his words, Chang Haonan suddenly paused.

"Do you think there will be a problem with the temperature distribution before the turbine?"

"That's right." Yao Mengna nodded firmly:

"The data we get now is just the result of sampling at the center and edge of the turbine."

"If you want to do this for a generally radially symmetrical temperature field, this is of course not a problem, but the turbine blades themselves have the function of active cooling."

"If the air film formed on the surface of the turbine blades is not uniform enough, then the cooling effect will fluctuate, and around 1600K, even a temperature change of just 20-30 degrees will significantly change the physical properties of the blades and affect the stability of the overall engine condition."

“……”

Chang Haonan listened to Yao Mengna's thoughts while flipping the test report in his hand to the back.

Sure enough, from the data again, unstable conditions similar to those on prototypes 01 and 03 were discovered.

Fortunately, this time he had reserved enough surge margin, so even in the process of thrust transients, there were no failures.

However, the sensor still faithfully records the moment the state of the throttle lever changes, and the violent fluctuations in the mass flow rate and boost ratio of the compressor.

"I think it's a possibility......"

Looking at the report in his hand, Chang Haonan realized that he had fallen into a misunderstanding before.

Because the position where the fluctuations in operating conditions are recorded at the beginning is the compressor.

Later, he presided over the revision of the part that was also a compressor.

So he's always felt that this part of the problem was there.

But the aero engine is a thing that affects the whole body.

The principle of air film cooling is to introduce secondary air flow from the hole on the wall surface of the high-temperature environment to the main stream, so that this cold air flow bends downstream under the pressure and friction of the main stream, attaches to a certain area of the wall, forms a cold air film with a lower temperature to isolate the wall from the high-temperature gas, and takes away part of the radiant heat of the high-temperature gas on the wall of the parts, so as to play a cooling and protective role on the wall.

This process requires the extraction of cryogenic air from the compressor as a cooling fluid, which has a direct impact on the air flow inside the compressor.

Of course, Chang Haonan knew the principle, but after all, it was not his old profession before, so he didn't think of this for a while.

"Thanks to your reminder, Senior Sister."

Chang Haonan hurriedly packed up the report on the table and prepared to go outside to find Yan Zhongzhong.

In the entire bench test, he is only responsible for the air intake distortion test related to the improvement of the compressor, and the person in charge of the other test subjects is still Yan Zhongzhong himself, so if you want to temporarily add test items, you have to sign the latter.

"It's okay, if you can help."

Yao Mengna wanted to hug the other party, but after thinking about it, it seemed that it was not the right time, so she had to put down her arm that had been raised halfway.

"It would be nice if I had come over when the test results came out......"

Fortunately, at this time, Yan Zhongzhong, who had just left the control room, pushed the door back in, without letting Chang Haonan notice her embarrassed expression.

"Mr. Yan, regarding the air performance test conducted later, Senior Sister put forward an idea......

……

With Chang Haonan's ability to show now, this kind of proposal was naturally adopted very smoothly.

In 1996, there was no very reliable non-contact in-line measurement method, so the staff of the 624 Institute installed a batch of armored thermocouples on the high-pressure turbine guide overnight.

After the three-hour test, the raw data was quickly given to Chang Haonan.

The results of the subsequent analysis proved that Yao Mengna's previous guess was completely correct.

Under the maximum afterburner thrust, the inlet temperature field of the engine turbine is parabolic along the blade height, that is, the temperature at the tip and root of the blade is low, and the temperature at the middle position is high, which is consistent with the design law.

However, as the engine speed gradually decreases, the unevenness of the temperature field in front of the turbine begins to increase.

The unevenness is highest when the throttle lever is near the "minimum afterburner" position.

This is exactly the same as what was recorded during the tests of the two prototypes – the most dramatic fluctuations occurred during acceleration or deceleration at transonic speeds.

That's right!

(End of chapter)