Back in 1978, I was admitted to Northwestern Polytechnical University.

Chapter 47 You don't quite understand? You understand very well, okay!

Is it really possible to increase the turbine inlet temperature by simply adding small holes to the sidewalls of a single-channel internal cooling system? The further out you go, the lower the air pressure becomes, and the worse the cooling effect will be!

The teacher who had just given Qin Liang pointers widened his eyes: "Yes, that's true, but... there's nothing we can do about it! We just need to make it according to the temperature that the blade tip can withstand!"

Qin Liang smiled and said, "I don't really understand either. You guys think that if we open multiple channels inside, that is, set up many baffles inside, so that the airflow inside the blades is divided into multiple streams, we don't need too many, just five channels would be enough. Wouldn't that ensure that the overall air cooling capacity of the blades is the same?"

If air cooling is to be used, then it must be five-channel, multi-path internal air cooling, which is the most suitable air film cooling technology. The thing in front of us is completely hollow inside, so it has no future at all!
"Sigh, Qin Liang, it's fine to think like that, but it's just wishful thinking. It's simply impossible to manufacture. How can you even manufacture the internal baffle? You probably don't understand the technical aspects of this at all."

"Ahem, I really don't understand, but... I do have an idea."

At this moment, Professor Ning said with great enthusiasm, "Qin Liang, continue!"

"These complex-shaped blades can only be made using casting. During the casting process, we use meticulously crafted molds to ensure that the blades, once formed, are exactly the same shape as required, eliminating the need for any subsequent machining processes. This is known as zero-margin precision casting..."

Ordinary casting produces a blank, which then requires various machining processes to obtain the required parts. This technology is obviously not suitable for manufacturing blades, because blades are inconvenient to process, not to mention the internal channels!

"Qin Liang, this only exists in an ideal situation. Needless to say, the thermal expansion and contraction of metal will result in a certain amount of allowance. You want to cast without any allowance, that's simply impossible!"

"That's right, there are many factors that affect casting, such as mold shrinkage, mold deformation, linear changes in the shell during heating and cooling, and thermal expansion and contraction of the alloy... However, we can calculate these deformations in advance and compensate for them during casting. Wouldn't that solve the problem? Especially the mold cavity anti-deformation compensation... I don't really understand it, and I don't know if this method will work..."

Everyone's eyes widened, and the teacher who had just questioned him fell silent.

Why didn't we think of these principles? We keep denying things, but never think of solutions?
"Qin Liang, you're amazing! You're not ignorant; you're an expert in this kind of precision casting without any margin!" Professor Ning exclaimed. "This has truly opened a new door for us!"

In the 1970s, new engines generally adopted zero-margin precision casting technology to manufacture turbine blades. However, this technology was strictly censored by the West and did not appear in any newspapers or magazines. The experts in materials science and aviation professors in the East simply did not understand it!
"Qin Liang, I have another question: how do we remove the internal mold?"

"Well, I don't really know either. Would using a wax model solve the problem?"

Qin Liang was extremely knowledgeable about this technology! However, based on his recent experience with computers, he knew that mastering the technology was only half the battle; he also needed to integrate it with the production tools of the time! This was something he lacked, but it was the expertise of these old scholars. Therefore, he simply provided the suggestions, leaving the specific implementation to them!

The zero-margin precision casting uses a wax mold, the biggest advantage of which is its smoothness, allowing the cast blades to achieve a very high degree of gloss!
"As for drilling, wouldn't it be better to use a laser for drilling?"

Everyone's eyes widened.

The key to air cooling is drilling holes in the blades! Back when we were working on this, figuring out how to drill the holes became a major obstacle. Later, Professor Shi found glass wire and used it to make a mold, which allowed him to directly leave the appropriate hole positions.

However, glass fibers were still too thick, so in later generations, lasers were used to drill holes in blades!

"Huaqing University excels at lasers; we can contact them later!" Professor Ning felt as if a new door had opened before him. "Qin Liang, do you have any other ideas? Tell us about them."

"Well, I don't know much about that either. I think that during the casting of the blades, could a strong electromagnet be used to generate a directional magnetic field outside? This way, the unsolidified alloy material would slowly solidify under the direction of the magnetic field, eventually having the same molecular arrangement. This would eliminate the transverse grain boundaries perpendicular to the stress axis, improving the alloy's plasticity and thermal fatigue performance..."

The zero-reserve casting technology is combined with directional solidification single crystal technology! This method produces the strongest single crystal blades!

Also in the 1970s, the West used related technologies in turbine blades, but unfortunately, the East remained completely unaware of these technologies.

Boom!
Another new door has been opened!
At this moment, Professor Ning looked at the leaf he had taken out. He used to treasure it, but now he really didn't care for it!
"Qin Liang, do you have any other thoughts?"

"Finally, there are the alloying elements. Current turbine blade materials are mainly nickel-based alloys, containing carbon, boron, and zirconium. The advantage of these materials is that they preferentially segregate grain boundaries and provide high-temperature grain boundary strength and creep resistance... cough cough, these are all just guesses, I don't really understand, but in casting, the addition of these materials will prolong the solidification time, producing primary carbides, which will damage the high and low fatigue characteristics of the blades. So..."

Qin Liang knew that what he said might be inexplicable, but... he already had enough mysteries surrounding him, so he didn't care about adding one more. After all, China Eastern Airlines' weakest point was its engines, and the toughest part of engines was the turbine blades!
"I'm wondering if there's a new formula that removes these elements and uses other elements, such as cobalt, tantalum, aluminum, and tungsten. The content of these doesn't need to be too high, around 10% to 6%. If we add about 3% rhenium... it might be even better. These are just my guesses, I don't really know much about it..."

I don't really remember the exact percentage; I'll just have the relevant personnel test it. But about three percent rhenium is necessary; it's key to increasing turbine temperature!
Qin Liang went on and on, from shape to casting, from casting to single crystals, and from single crystals to new materials! Don't you understand? You're practically a materials expert!
(End of this chapter)