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

Chapter 248 Advanced Processing Technology? Northwestern Polytechnical University has it!

Variable Cycle Engine Project Office.

“Let’s start from the very beginning. Install an adjustable exhaust ring for the outer bypass duct behind the second stage fan… Our fan has three stages, why are you installing an exhaust ring behind the second stage?” Ted Englin was annoyed to see that Northwestern Polytechnical University had sent a group of students over, so he began to ask questions.

The original F101 engine had a two-stage large fan, but it was later replaced with a three-stage fan for use in fighter jets, with the diameter reduced to 970 mm and the pressure ratio increased to 3.2.
When they were considering the variable circulation technology, they also thought about venting the air from here, which is behind the three-stage fan. Since the East chose the area behind the two-stage fan, there must be a reason for it!

"After the third-stage fan comes the first-stage blade of the high-pressure compressor." Ding Jun secretly rejoiced, knowing that he had memorized all of this knowledge.

“During the conversion of the variable cycle, a mismatch between high and low pressure can occur. Setting up an outlet ring at this point can adjust the matching between the high and low pressure compressors. However, once you reach the third stage, you will directly face the high-pressure compressor, which may lead to obstructed airflow. We have repeatedly simulated this on the computer and believe that this approach is not feasible.”

"Could you simulate it for us again?"

"This... requires special software, and we don't know if it will be available for you to use, so... you'll have to wait while we report to our superiors."

A few minutes later.

"The school needs to submit a report to the capital, which may take a few days. If you can provide the parameters of the F101 engine and send them to our computer science department for verification, it will be much faster."

"No, let's wait."

In the computer science department, a group of teachers and students frantically typed on their keyboards and modified a software specifically for calculating the high and low pressure matching inside an engine in just one day. This is no ordinary task. Fortunately, Northwestern Polytechnical University has a wealth of talented people in the computer science department, and everyone is a programming expert!
"While you're working, listen to what Qin Liang means. If you can't write it in a day, don't worry. Just design a timer in the program to give the calculation results after a few hours. The three-stage fan will cause airflow disturbance, but the two-stage fan won't have a problem. However, the data recording and transfer program must be cleverly written! Once the data is stored in the computer, it must be transmitted out through the data link system that the Department of Electronic Engineering just developed!"

In this era, most computers didn't even have internet access and could only play offline games. Northwestern Polytechnical University used a local area network (LAN) because they needed to conduct research and work on the same projects. Simply put, all the data in the same computer room was stored in a single hard drive enclosure.

If nothing unexpected happens, the Americans will value that hard drive enclosure very much. Once the development is complete, they will probably take it with them and keep it under close surveillance.

If you want to copy technical data, you have to do it wirelessly!
In later generations, wireless local area networks used by computers only began in the 1990s, but now, Northwestern Polytechnical University is already developing the first generation of data links. This thing can easily connect to the network and transmit signals wirelessly!
Shenyang, Institute 606.

"Zhang, the design data for the first three-stage fan blades of the American F101 engine has been sent to us by Northwestern Polytechnical University!"

Engineer Zhang exclaimed excitedly, "Hmm, not bad! Plug it into the computer right away!"

The design at Institute 606 has already started using computers. For complex fluid dynamics products like engines, computers can only be used to assist in the design. After the design is completed, it is blown in a wind tunnel to obtain a large amount of data, and then the design is modified. This process is carried out little by little.

Currently, the research and development team at Institute 606 has only just completed the design of the first three stages of the fan. For this type of military high-thrust engine, the first three stages of the fan are essentially low-pressure compressors. The design team has benefited greatly from the development of each stage and has thoroughly mastered the design of the low-pressure compressor. Any modifications they make in the future will be a piece of cake!
Soon, the design drawings for the F101 engine's fan blades appeared on the computer. Engineer Zhang carefully studied the drawings, and then…

"Isn't this just an enlarged version of the F404 engine fan blades?" Engineer Yin Haiyang exclaimed, looking at the data. "These Americans, they can actually cut corners!"

The F101 engine was originally designed for bombers, so its bypass ratio exceeded 2. To convert it into a fighter jet engine, the original two-stage fan was changed to a three-stage fan with a smaller diameter, reducing the bypass ratio to 0.87. At the same time, the low-pressure turbine was modified to increase its speed, and that was how it was modified.

At the time, GE had the F404 as a mature turbofan engine, so they simply enlarged the blades of the engine's third-stage fan and used it directly.

“Yes, the Americans can be lazy too, but the fact that they can achieve a perfect match after simply scaling it up is quite remarkable. It shows that they have thoroughly mastered the design of the engine core,” Engineer Zhang said. “Moreover, the design concept of these fan blades is also very inspiring for us.”

This is the first time Dongfang has come into contact with a foreign third-generation large thruster, and it even includes design principles, structural diagrams, and detailed data!
Engineer Zhang remarked with deep emotion, "They are using integral bladed disk technology, which requires advanced powder metallurgy technology. With our current level of expertise, we simply cannot produce it..."

The fan blades are inserted into the fan blade disk. The connection between them requires various mortise and tenon structures and various fixing methods, which not only increases the complexity but also reduces the reliability. If a pin comes loose, it will be a disaster.

The integral bladed disk technology integrates the blades directly with the bladed disk, making it a single component.

It's important to know that in order to reduce weight, this engine uses a lot of titanium alloy inside, and it's not easy to integrate the impeller and blades together.

Even if you obtain Western technical data or even samples, you still can't manufacture it. After all, it's related to a country's industrial base. Even if you have a complete bladed disk in front of you, if you don't know how it was manufactured, it's all for nothing.

"How about we ask Northwestern Polytechnical University?" Yin Haiyang suggested. "Their technology is very advanced; perhaps they have already overcome this technical hurdle."

"Yes, the engine fan blades that Factory 410 made for us are still separate. In our recent tests, there was even a serious accident where a blade flew off. If Northwestern Polytechnical University has similar technology, we'll order directly from them..."

Factory 410's processing technology is still at the level of the 1950s and 1960s. Although there are some highly skilled craftsmen there who can achieve higher processing precision than CNC machine tools with their bare hands, ... this kind of technical issue really cannot be solved.

"Does Northwestern Polytechnical University have it? Qin Liang doesn't recommend directly copying the F404, which means our domestic industrial base isn't sufficient..."

Zhang stood up: "Let's go take a look and we'll see!"

Northwestern Polytechnical University, Department of Materials Science and Engineering.

"Professor Zhang, these Americans have the confidence to make the world's best engines. Their manufacturing technology is truly advanced!"

"Yes, this technology is twenty years ahead of our Eastern aviation industry!"

Listening to the incessant chatter of the group from Shenyang, Professor Zhang frowned: "What advanced processing technology?"

"You were at Northwestern Polytechnical University, didn't you analyze the data on the American F101 engine right away?" Engineer Zhang asked, his face full of surprise. "Now, we've obtained all the data on the first three stages of the fan. The integrated bladed disk technology alone is enough for us..."

"I thought it was something special, but it's just a single-plate impeller!"

"Northwestern Polytechnical University has it?" Engineer Zhang was even more surprised.

"It must have been quite a journey for you to come all this way. Come on, let me take you to see the factory run by the Department of Aero Engines!"

Now, almost every engineering department has its own department-run factory. After the cruise missile project won the military order, the aero-engine department's department-run factory also developed rapidly.

A group of people from Shenyang, filled with doubts, drove through the campus, past a field of crops, and then stopped in front of a factory.

The factory buildings are old, probably converted from other factories. Once inside, you can see that various engine parts are being produced in the spacious and clean factory buildings.

"Come on, look, this is the machining of the integral bladed disk of our WS-11 engine. Our engine is very small, and it would be very complicated to use the traditional method, so we simply machined it as a whole!"

Everyone stared wide-eyed at the CNC machine tool in front of them, where a blank with a diameter of 30 centimeters was fixed on the worktable. The worktable could move, and the cutting tool on it could also move. This was... a multi-axis linkage CNC milling machine?
No, this isn't just panel milling! As the cutter moved along the Z-axis, everyone's eyes widened—it also included plunge milling!

"Where did this CNC machine tool come from?"

"Our Northwestern Polytechnical University's Department of Mechanical Engineering developed the WS-11 turbofan engine. It may be small, but it has all the essential parts. The machining process was quite challenging. So, the Department of Mechanical Engineering specially developed a disc milling-sinking composite milling center. This thing can't do anything else but machine integral bladed disks, specifically the cold end ones."

Disc milling is used to machine disc surfaces, but it is difficult to machine complex curved surfaces. Therefore, it is necessary to combine it with plunge milling, which is one of the most effective machining methods for high material removal rate metal cutting and can also be used for curved surface machining.

For machining complex curved surfaces, combining these two methods is the most efficient approach.

Northwestern Polytechnical University can actually build such a composite milling center? This is... simply unimaginable.

Watching the cutting tool perform complex movements and precision machining, the engineer Yin Haiyang couldn't help but ask, "The machining program for this tool must be very complicated to write, right?" "Yes, it would definitely be very difficult to machine it directly by hand, but... our computer science department has developed a dedicated software system for multi-axis NC programming of impeller-type parts. This system integrates data preprocessing, surface modeling, surface hidden surface removal, tool position calculation, tool position verification, and post-processing. We just need to input the product data to be machined, and the program will calculate how to machine it itself."

This...this isn't just advanced, this is super advanced!

At this moment, the CNC machine tool slowly stopped rotating, and inside, the shiny, integral bladed disk was completed.

"Can we take a look?" Zhang Gong couldn't help but ask curiously.

"of course can."

So, Engineer Zhang put on brand-new white gloves and took the finished integral bladed disk. The moment he held it in his hand, he was immediately surprised: "What material is this?"

"Stainless steel!"

I go!

The engine experts from Shenyang present were all stunned.

For aircraft, reducing their own weight is very important. To achieve this goal, advanced materials must be used. Titanium alloys are lightweight and high-strength, making them the most suitable material for aircraft. Not to mention engines, even the structural frames of fighter jets are using more and more titanium alloys.

Northwestern Polytechnical University, which boasts the best technology in China, is using stainless steel.
"Stainless steel is strong and can withstand impacts from external objects very well. Our engine is used in aircraft that typically fly at extremely low altitudes, so we chose this material. Of course, most importantly, it's cheap!"

This isn't a repeatedly used aircraft engine with a lifespan of several thousand hours. For a cruise missile engine, a lifespan of twenty hours is more than enough. At the same time, the price of the engine is the most important factor; the cheaper the better. Titanium alloy would be a waste!
Needless to say, the domestically produced ones are also made of steel, as is the F107 used in the American Tomahawk engine, including the fan and high-pressure compressor. Only the low-pressure compressor uses titanium alloy. The products copied here are naturally made in the same way.

"Then... can this machine tool process titanium alloys?"

Just now, watching the blades flip and the fine filaments flying as they were cut, I felt a bit strange. After all, titanium alloy is very difficult to process. It's extremely hard and has poor heat dissipation. During processing, friction generates heat, which accumulates and doesn't dissipate. If the temperature gets too high, the parts will be ruined.

"Of course! Come on, let's adjust the program and move on to machining titanium alloy compressor blades!"

"Okay." The worker next to him immediately pressed the button next to the CNC machine tool, switched the processing program, and then put a titanium alloy blank into it.

The machine started up again, but this time the processing was very slow. It also used a special cutting fluid to continuously carry away the heat generated during processing, which amazed the group of people from Shenyang.

There's no part that Northwestern Polytechnical University can't process!

"What is the largest diameter fan this machine can process?"

"Within one meter."

The group from Shenyang became excited: "Great! This perfectly meets our needs. Please help us manufacture three integral bladed disks..."

"That's no problem, but we'll have to wait a while. We'll order a batch of unfinished units from Shanghai."

"Magic City?"

"That's right. This small bladed disk can be machined directly. A large bladed disk would be too wasteful. We would have to precision forge a blank, which would greatly reduce the amount of cutting work."

"You actually have precision forging capabilities?" Engineer Zhang was completely taken aback.

The manufacturing technology of this integrated bladed disk is complex and is entirely controlled by the three giants of Britain, the United States, and Russia. They have developed different technologies based on their own specific circumstances.

Some are precision welded and CNC machined, usually electron beam welding, which welds the titanium alloy blades and titanium alloy disk together, and then CNC cutting. Others are precision forged and precision machined, using a die forging press with tens of thousands of tons to forge a blank first. The basic shape of the disk and blades is already on this blank, leaving very little machining allowance. This saves materials, but the precision must be guaranteed, otherwise there will not be enough material to process, and the part will be scrapped.

In later generations, there will be high-temperature alloy precision casting technology, which will directly produce the blades without even needing CNC machining. They will only need to use hot isostatic pressing to increase their strength.

Originally, Dongfang had no technology at all, but now, looking at the engine factory of Northwestern Polytechnical University, the group of people from Shenyang were all amazed.

“We don’t have it, but the Shanghai Aircraft Factory does.”

The die forging press over there has been built, which will give us the confidence to build large aircraft in the future. At the same time, we also have a foundation for the various parts of the aircraft!
Forged on that surface, the resulting products are of even higher quality than those made by the Americans!

"The Shanghai Aircraft Factory was also established with the support of your Northwestern Polytechnical University." Engineer Zhang said with emotion, "With the support of your Northwestern Polytechnical University, the aviation industry technology in the East is advancing by leaps and bounds. In just a few years, we will be able to catch up with the advanced level of the West!"

“Catching up is nothing, we have to surpass!” Professor Zhang said. “We need to set higher goals for ourselves! By the way, where are your materials? Just bring them over and copy them to the computer here.”

Soon, the design diagram of the fan blades appeared on the computer screen.

"Our WS-10 turbofan engine adopts a three-stage fan blade design, with the first two stages using a shoulder design to increase strength..."

"Well... although I'm not from the engine department, I feel that a wide-chord design would be better for the first-stage fan blades?"

"Even American fighter jet engines aren't designed like this."

"That's because they're lagging behind. We've been working on wide-chord blades for a long time. They have a larger flow rate and a higher pressure ratio. Moreover, because the blades are wide enough, they are also very strong and have a strong ability to resist impacts from foreign objects. Since you're going to develop a completely new engine, why not use new technologies?"

Engineer Zhang took a deep breath: "We... won't."

It's truly...shameful that the most professional engine design institute in China can't master world-class technology!

"Oh, forget it then."

"No, we can't let it go like this. Let's go back to Northwestern Polytechnical University, to the Department of Engine Engineering, and ask them for help!"

"Does this mean that the three-stage fan you just developed will have to be scrapped and started all over again?"

"It's okay, we can start over. If we're going to do it, we have to do it at the world's advanced level!" Professor Zhang said.

They have to aim for higher standards, otherwise... if Northwestern Polytechnical University manages to replicate the F101 engine, their WS-10 project will probably be scrapped again! That Qin Liang keeps saying that China's industrial base is not high enough to directly replicate Western products, that's too modest.

Other institutions can't replicate it, but Northwestern Polytechnical University might actually be able to.

Excessive humility is arrogance!
Achoo! Qin Liang sneezed.

　PS: Machining tools, methods, and the wide-chord blades of later improved versions of the F110.

　　
　
(End of this chapter)