Chapter 470 You are right, MIT made a mistake
“More imaginative?”
Liu Yongquan, 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 rapidly decays behind the air film holes, Due to the mixing of the front row cooling air with the mainstream, the ambient temperature of the rear row of air film holes is reduced, which gradually increases the effectiveness along the flow direction and achieves better wall cooling effect."
Chang Haonan stopped. action, 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. .
PTSD is a crime.
Obviously Chang Haonan is much younger than him, but this tone, this look, this question...
It is exactly the same as a tutor who looks down upon new graduate students.
"I...I've seen it."
Liu Yongquan wiped the non-existent sweat on Zhengliang's head, and his mind was thinking rapidly about whether he had missed any important points before.
But after thinking about it, I finally didn’t remember it, so I had to continue nervously:
“But I remember that the data in that article was actually very problematic. Although the author used clever writing methods, The pictures and processing methods cover up some of the problems, but it is obvious that the problem is obvious. In his study, a very small scaled version of the turbine blade was used, and the amplification effect was not considered. However, in fact, the data trend is very obvious. It can be clearly seen 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 not be so optimistic. Furthermore... Furthermore, if this research is really meaningful, I'm afraid Also...also..."
"Well..."
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. It happened that what he was going 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.
"Huh?"
Chang Haonan finally finished the work at hand. He wiped the sweat from his palms on his lab coat. Then he turned around and saw a slapped face. Liu Yongquan, who looked like a student:
“You want to say that if the research was 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 1970s, 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 developing the Turbojet 14, the Chinese aviation development researchers who had to use film cooling due to the excessively high temperature in front of the turbine could only scrape some scraps from some Russian phrases. In the end, although the turbojet 14 turbine was built, the cooling effect was still 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 to The turbine was also modified along the way.
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:
"The MIT article, although it is in There are indeed some breakthroughs in theory, but there is still a long way to go before practical application. Judging from some reports, the main direction of foreign research now should be the combination of impact cooling of slot jets and film cooling of formed hole jets. Maybe this is also the case. 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 was hanging again. "No, Liu Gong, your idea is fine."
Chang Haonan said and took out an English material from the bag next to him, which was obviously the one the two of them just talked about. paper.
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 of this article, but suddenly from fluid mechanics research to gas-heat coupling issues, he still has to find an excuse.
He handed the paper to Liu Yongquan:
"It's MIT and their ideas that are wrong."
"Huh?"
Liu Yongquan, who had just turned the paper to the second page, was immediately stunned.
Not to mention the late 1990s, even more than 20 years later, MIT is still a bit sacred in science and engineering disciplines.
Although Liu Yongquan thinks 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.
"Now foreign countries are pinning their hopes on the slot jet, which is nothing more than the weak three-dimensional flow characteristics of the slot jet. The assumptions between the front and rear jets basically meet the Sellers superposition model, so the prediction of the effectiveness of the adiabatic air film The accuracy is higher, and because the discrete air film hole has a three-dimensional vortex structure, and the cooling jet of the same exhaust film hole has discrete characteristics, multiple exhaust flows interfere with each other, and it is completely impossible to predict using the Sellers superposition model... ...Just being lazy.”
Although Chang Haonan had an empty hand, he had basically memorized the details of the article. When he said this, he immediately pointed to the paper in Liu Yongquan’s hand:
"Look at Table 3-4 to Table 3-7 of this article."
"Oh..."
Liu Yongquan turned to the third chapter of the paper in 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 The research methods include using pressure-sensitive paint to measure the effectiveness of the insulating film for composite angular film cooling of differential arrays, and using thermotropic liquid crystal polymers to visually measure temperature. These methods are indeed quite advanced."
One. After a comprehensive evaluation, Chang Haonan finally concluded:
“In general, they are actually very close to the right direction in this article, but they did not go in that direction at all when processing the data. Just thinking about it."
"So... MIT doesn't even know that it has a baby?"
Although Liu Yongquan still didn't fully understand Chang Haonan's technical ideas, this part I still understand 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. For people, it doesn’t take long to discover this.”
Chang Haonan walked back to the newly debugged equipment and patted it gently on the casing:
“ 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 is enough to be combined with traditional cooling technology. 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 the end wall of the turbine, the blade top, the trailing edge, and even the air film on the side wall of the annular combustion chamber. Considering the cooling effect as a whole, while the cooling effect is better, it can also reduce the consumption of cooling air flow, 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 they were preparing for a fifth-generation engine when the turbofan 10 was not even mentioned, Liu Yongquan would have thought that the other person was crazy.
But when Chang Haonan said these words, he just felt...
It didn't seem that exaggerated.
(End of this chapter)