Chapter 470 You are right, MIT is wrong

"More imaginative?"

Liu Yongquan, who was holding the operating document in his hand, was stunned.

"Ah, I have read an MIT paper before and found that after adjusting the arrangement of cooling holes into a multi-layer array, although the effectiveness of each row of jets quickly decays behind the air film holes, due to the difference between the front row of cooling air and With the mixing of the mainstream, the ambient temperature of the air film holes in the rear row is reduced, thereby gradually increasing the effectiveness along the flow direction and achieving better wall cooling effect."

Chang Haonan stopped what he was doing and turned back to look at Liu Yongquan:

"You should have seen it too, right?"

At this moment, the latter suddenly felt a chill on the back of his neck, and he felt like he was back to the time when he was just a graduate student ten years ago and was called over for a group meeting.

I'm going to suffer from PTSD.

Chang Haonan is obviously much younger than him, but this tone, this look, this question...

It's almost like a mentor who looks down upon new graduate students.

"I...I've seen it."

Liu Yongquan wiped the non-existent sweat on Zheng Liang's head, and his mind was rapidly thinking about whether he had missed any important points before.

But after much deliberation, I finally didn't think of it, so I could only continue nervously:

"But I remember that the data in that article was actually very problematic. Although the author used clever drawing and processing methods to cover up some of it, the problem was clearly visible. He used a very small size in his study. The scaled-down version of the turbine blades does not take into account the amplification effect, but it is obvious from the data trend that if the blades are enlarged to the level of a normal aircraft turbofan engine, then the cooling effect at the rear end of the blades should be less I'm optimistic, and besides...and if this research is really meaningful, I'm afraid...also..."

"Um……"

Chang Haonan actually heard Liu Yongquan's thoughts completely, but because he was still preoccupied with debugging the equipment, he couldn't organize a complete sentence in his mind for the time being. It happened that what he wanted to say later was more complicated, so he had to hum first. Show that you heard it.

However, this reaction made Liu Yongquan break into a cold sweat, and the sense of déjà vu became even stronger when he returned to graduate school.

"Ok?"

Chang Haonan finally finished the work at hand and wiped the sweat from his palms on his lab coat. Then he turned around and saw Liu Yongquan, who looked like a student being disciplined:

"You want to say that if that research is really meaningful, it wouldn't be so easy to publish, right?"

Countries are actually pretty much the same when it comes to keeping the most critical core technical details confidential.

Take the matter of air film hole cooling as an example. Since the related concept was proposed in the late 70s, for nearly 20 years, the entire industry has been unable to find a single valuable research article.

Not to mention the review.

This led to the fact that when the Turbojet 14 was developed that year, the Chinese aviation development researchers, who had to use film cooling due to the excessively high turbine front temperature, could only collect some scraps from some Russian phrases. In the end, although the Turbojet was A 14-inch turbine was built, but the cooling effect was always somewhat unsatisfactory.

Fortunately, the second-generation domestic nickel-based high-temperature alloy was later used, which ensured the most basic reliability and service life at a certain cost. Otherwise, Chang Haonan would have had to modify the turbine in addition to the compressor. .

That cannot be completed in a few months.

"Yes."

Hearing that Chang Haonan's rhetorical question was similar to his own, Liu Yongquan finally relaxed a little:

"Although the MIT article did make some breakthroughs in theory, it is still far away from practical application. Judging from some reports, the main direction of foreign research now should still be the impact cooling of slot jets and formed hole jets. The combination of air film cooling may be the reason why this article was finally released.”

"wrong."

Chang Haonan waved his hand directly, then walked to the side and took off his lab coat.

"This...this...Mr. Chang, is there anything wrong with my idea...?"

Liu Yongquan's heart skipped a beat again.

"No, Liu Gong, your idea is fine."

Chang Haonan said as he took out an English material from the bag next to him, which was obviously the paper the two of them just talked about.

The number of papers studying blade cooling these days is extremely rare, so any paper will be studied carefully in China.

Since online databases are not yet popular, various research institutions even have dedicated data clerks responsible for collecting these actually public contents.

The paper in his hand was brought over by the data clerk of the Taihang project team a few days ago.

In fact, Chang Haonan certainly does not need the inspiration from this article, but suddenly from fluid mechanics research to gas-heat coupling issues, he still has to find an explanation.

He handed the paper to Liu Yongquan:

"It's MIT who have the wrong idea."

"what?"

Liu Yongquan, who had just turned the paper to the second page, was immediately stunned.

Not to mention the late 90s, even more than years later, MIT is still a bit sacred in science and engineering disciplines.

Although Liu Yongquan believes that he is no longer superstitious about foreign authorities, he just said that the research in this paper is biased towards the gas-heat coupling theory and has little practical significance for engineering applications.

“Foreign countries are now pinning their hopes on slot jets. This is because the three-dimensional flow characteristics of slot jets are weak. The assumptions between the front and rear jets basically meet the assumptions of the Sellers superposition model, so the effectiveness of the adiabatic air film is unknown. The prediction accuracy is higher, and the discrete air film hole has a three-dimensional vortex structure, and the cooling jet of the same exhaust film hole has discrete characteristics, so the multiple exhaust flows interfere with each other, and it is completely impossible to use the Sellers superposition model. Prediction... just lazy."

Although Chang Haonan's hands were empty, he had basically memorized the details of the article in his mind. When he said this, he immediately pointed to the paper in Liu Yongquan's hand:

"Look at Tables 3-4 to 3-7 in this article."

"Oh……"

Liu Yongquan turned to the paper in a bit of a hurry

"If you extract the strength of the vortex structure from several tables and calculate the Reynolds number, you will find that the turbulent boundary layer can enhance energy transport compared to the laminar boundary layer, thereby effectively reducing the strength of the vortex structure. In addition, their Research methods include using pressure-sensitive paint to measure the effectiveness of the adiabatic film cooling of composite angular film cooling of differential arrays, and using thermotropic liquid crystal polymers to visually measure temperature. These methods are indeed quite advanced."

After a comprehensive evaluation, Chang Haonan finally concluded:

"In general, they are actually very close to the right direction in this article, but they just didn't think in that direction at all when processing the data."

"So... MIT doesn't even know it has a baby?"

Although Liu Yongquan still didn't fully understand Chang Haonan's technical ideas, he still understood this part of the content.

"Yes, but they will not go on this wrong route for too long. The problem of slot jet is too big, and the higher the performance requirements of aviation engines, the more obvious the defects will be. For the United States, which is already installing and testing the fourth-generation engine. It doesn’t take long for humans to discover this.”

Chang Haonan walked back to the newly debugged equipment and patted the casing gently:

"Theoretically speaking, third-generation engines such as the Turbofan 10 cannot actually use such high-end cooling technology. The third-generation nickel-based blade material and combined with traditional cooling technology are enough. F110 and AL31F are both That’s how it works.”

"But I still plan to apply multiple rows of superimposed full-coverage film cooling on it. Taking the film cooling effect of the turbine end wall, blade top, trailing edge, and even the side wall of the annular combustion chamber into consideration as a whole, the cooling effect will be better. At the same time, it can also reduce the consumption of cooling airflow, which can also be regarded as laying a technical foundation for future fourth-generation and even fifth-generation engines."

"The...fifth generation engine?"

If another person had said that he was preparing for a fifth-generation engine when he didn't know anything about Turbofan 10, Liu Yongquan would have thought that the other person was crazy.

But after Chang Haonan said these words, he just felt...

It doesn't seem that exaggerated.