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

Chapter 247 The Third Generation Great Push is in Hand!

The Americans have already used a variable cycle engine on the J-58, but that was a conversion between a turbojet and a ramjet engine. The variable cycle engine they're going to play with now is a conversion between a turbofan and a turbojet engine.

This cannot be achieved simply by installing some bypass pipes and vent valves. The key is that the engine's low-pressure turbine not only drives the low-pressure compressor but also the front fan blades. Unless it is a three-rotor engine with a dedicated turbine for the fan, it needs to be matched.

When a turbofan becomes a turbojet, the front fan no longer needs to blow air. As a result, the low-pressure turbine will drive the low-pressure compressor at full speed, resulting in excess power. This leads to a mismatch between high and low pressure, causing the engine to operate sluggishly or even experience sudden surge!
This is a major problem facing turbofans, turbojet engines, and variable-cycle turbojet engines.

The solution to this problem is to reduce the power of the low-pressure turbine after the turbofan is converted to a turbojet. As for how to reduce it, we can use a design scheme with variable pitch turbine blades.

This variable pitch technology originated in the era of propeller aircraft. Early aircraft propellers were fixed and had an optimal efficiency range. Later, in order to improve performance, the propeller blades were no longer fixed, and their torsion angle could rotate. Thus, variable pitch propellers came into being, matching different propeller angles for different speeds.

When a propeller rotates once, it travels a certain distance along the propeller shaft. This distance is called the pitch, which can be simply understood as the twist angle of the propeller blades.

After the jet age, propellers were no longer needed, but ships sailing at sea still need them. Advanced ships use variable-pitch propellers, which not only provide the most efficient propulsion, but also allow the propeller blades to rotate through the plane and continue to rotate when needed, so that the ship can reverse while the direction of the drive shaft remains unchanged.

Now, for turbofan engines to operate on variable cycle, the power of the low-pressure turbine needs to be adjusted, which requires variable pitch turbine blades!

Turbine blades operate in a high-temperature, high-pressure environment, and the twist angle of the blades can also change... This technology is extremely difficult, and I never expected that the East would be researching this technology!
Ben Rich took a deep breath: "Qin, we can coordinate with the relevant departments to send the engine over, but... this engine needs to be under our supervision! You can't touch the engine without our permission."

Qin Liang waved his hand: "Forget it, forget it. With so many conditions, what are we after? You don't need to make things difficult for us, and it will save us the trouble."

If you want to cooperate, then lower your stance and adopt a humble attitude. Don't be so high and mighty, as if we're begging you!
Qin Liang doesn't tolerate foreigners!

Ben Richie was taken aback.

After the meal, Qin Liang saw the group out of the cafeteria, and then someone else came over.

"Liangzi, you're here! I've finally found you! A telegram from AVIC says another business opportunity has come our way! A big client from the Middle East..."

Recently, just because of the prelude to a war, the East has sold a lot of airplanes, which is really enviable!

and many more!

A major client in the Middle East?

Who is it? Could it be Sha? These rich dogs are very wealthy, and they're having a falling out with the Americans because they bought too few F-15s. If Sha also bought the Super-7 or J-8... I'd say oh my god!
Wouldn't that mean the Easterners could get F-15 engines from Sha?

Ben Richie had mixed feelings.

The Fifth Department Building, computer room.

"Liangzi, how did it go after you tried to fool the Americans?"

"These guys aren't so easily fooled. We need to keep them in limbo for a while longer," Qin Liang said, as he quickly worked on a design on his computer.

After deceiving Boeing, the number of researchers working on the Super Cruiser project dwindled, and now only two or three students are pushing the project forward, making progress very slow. Fortunately, Dick Taylor's purpose in coming here was not this, otherwise he would have no way to explain himself.

I need to refine the design quickly, so that if Dick Taylor comes back, I'll have something to say. Boeing has invested a lot in research and development, and I can't let them think that their money went down the drain.

Fortunately, all the programs are already in place, and the computer can run automatically as long as you input the requirements.

Professor Sha continued, "If they can really send us the F100 engine, then... do we still need to do forward development?"

As Qin Liang initially suggested, the development of third-generation military high-thrust engines should not be rushed. It should be done step by step, starting with the core engine and then matching it with different bypass ducts. Low-bypass ratio engines can be used in fighter jets, while high-bypass ratio engines can be used in passenger planes, transport planes, bombers, and the like.

Since it's done stage by stage, the efficiency is naturally very low. It's said that it's still stuck in the first two compressor stages.

"Of course, we still need to conduct forward development. This can't be rushed. Even if we actually get our hands on a third-generation high-thrust engine like the F100, it will only be used as a reference..."

Qin Liang continued operating the computer as he spoke.

Another busy day has passed!

At 11 p.m., the computer room was still packed with people. Qin Liang rubbed his eyes and prepared to leave. Sure enough, married men just can't keep up with their health!
Just then, someone rushed over: "Liangzi, Liangzi, the foreigner is back and wants to see you!"

"It's so late, let's talk tomorrow."

"They said they agree to your request."

What?
So fast?
Inside the meeting room, Qin Liang yawned, looking at the several people who were still full of energy.

“We’ve already telegraphed back home, and the Air Force has agreed. Congress is processing the paperwork, and it should be approved within a week. Then they’ll send you the two F100 engines,” Ben Ritchie said. “We hope they can provide us with a copy of the technical documentation here.”

"That's impossible. Let's wait until the engine arrives," Qin Liang shook his head.

Do you Americans have any credibility? You can't even keep a signed contract, let alone a verbal promise. I gave you the design, and you turned around and went back to study it yourselves. Wouldn't that be a complete loss?
Ben Richie said with a hint of helplessness, "Qin, this isn't the first time we've worked together, and we've never broken our promises. By the way, although Congress hasn't approved it yet, the first batch of R&D funding should arrive in twelve hours."

"Alright, then we'll give you a brief introduction to the technology once the R&D funding arrives."

"Ok."

They didn't want to wait even one night, but Qin Liang... he needed time to prepare.

My back was already aching, and I still had to work through the night to make the variable cycle engine plan as detailed as possible. I sent one copy to the engine department so they could prepare it immediately, and I gave the other copy to the Americans so they could see it and be amazed at how advanced our Eastern technology is!
The next day, in the morning.

Inside the meeting room, several people looked at Qin Liang wearing sunglasses with great curiosity.

"Qin, you?"

"Just arrived, the same style as the US Air Force sunglasses. They look really cool on! Oh, by the way, here's the information for you. Take a look first, and keep any questions for now. I'll answer them when I have time."

Qin Liang threw the documents on the table and swaggered out, taking off his sunglasses to reveal red eyes and dark circles. Damn it, I've been working too hard! I need to go back and catch up on some sleep!

The group watched Qin Liang's departing figure, each with some doubts. However, when they picked up the documents, their eyes widened immediately.

So smart!
This design is almost identical to the F100. The engine has a fan at the front, and behind the second-stage fan, there is an adjustable bypass duct exhaust ring. In the engine's high-pressure compressor, the first-stage working blades are deliberately elongated to form a new fan, which is labeled as the core engine drive fan. Behind it, there is an exhaust ring that flows into the bypass duct.

This gives the engine two bypass ducts.

During takeoff and low-altitude, low-speed flight, both outer bypass ducts are open, thus transforming it into a high-bypass turbofan engine. When flying at high altitude and high speed, the exhaust ring behind the second-stage fan is closed, and the engine becomes a low-bypass turbofan engine. This not only avoids increasing additional drag but also provides greater thrust than a turbojet engine!

This Easterner has ideas!

As for variable-pitch turbines...

Upon seeing the design drawings, Ben Ritchie couldn't help but exclaim, "Brilliant, brilliant! Changing turbine blades is too technically difficult. Adding variable-pitch guide vanes between the high- and low-pressure turbines makes things much easier!"
The blades rotate, and the internal pitch-changing mechanism is incredibly complex, enough to drive engineers crazy. However, simply placing a fixed guide vane in front simplifies things considerably!
Clever, truly clever! This design is simply a crystallization of Eastern wisdom!

“Hmm, these Easterners do have some skills. Now that we have the technical route, what’s next? Just take the plan back and hand it over to General Electric for development, right?” Chiracer suggested a bad idea: “Anyway, General Electric has already allocated a million dollars, so let’s just consider it as payment for buying these technologies.”

Ben Rich's expression was complicated: "These technologies are indeed worth a million dollars, but do you think that's all the Easterners are thinking? Could they be hiding something, or have other plans they haven't included?"

Chiracl paused, then said, "So we really have to hand over the F101 engine to them? What if..."

“There’s no ‘what if’,” Ben Rich said. “With your General Electric’s push, the engine supply to the East was cut off, and then they went to the Russians for engines. You tell me, they’ve been in contact with the RB199 for over two years and the F404 for almost a year. Why don’t they copy it?”

“Hmph, they still have to be able to copy it! Eastern technology is too backward!” Hillakel said, “Their technological level is only at the level of Spey.”

"That's right. If that's the case, they'll be even less likely to be able to copy the F101. What are we worried about?"

The F100, the mainstay third-generation high-thrust engine of the U.S. Air Force, was developed by Pratt & Whitney in the late 7s. The JTF22 demonstrator began operation in July 1969, and this demonstrator was developed based on the JTF16j.

The first production model was officially delivered to the Air Force in November 1974, which means it took ten years of hard work to complete.

However... after being put into service, the F100 engine quickly developed serious quality problems, such as compressor blade stall, turbine burnout, and parts not reaching their design lifespan, which even forced the F-15 to be grounded multiple times.

Pratt & Whitney remained calm about these shortcomings. They figured that if there were problems, they would fix them gradually, and the Air Force would just allocate the funds first.
The Air Force endured it time and time again, but finally could not bear it any longer and turned to General Electric.

General Electric lost the initial bid, but after seeing the problems that occurred with the F100 engine, General Electric became active again. In 1976, it raised funds to build the F101X demonstrator, which had similar thermal parameters to the F100. When the Air Force learned about this, it immediately invested $80 million to develop three prototypes, designated F101DE.

The F101DE is now undergoing flight testing on the F-16. It's important to know that for a single-engine aircraft, an engine failure can cause a first-class or even a major accident.

However, the test results satisfied the Air Force, so the later F-16s began to use a mix of the two engines, and the F101DE was also given the designation F110. Of course, this was several years later.

When Pratt & Whitney discovered that General Electric had caught up, they became anxious and quickly addressed the problems with the F100. The improved F100-PW-200 engine essentially solved the previous reliability issues.

As it turns out, putting all your eggs in one basket is a bad idea; capitalists don't care about the military's actual interests, they only care about money.

This also illustrates that aero engines, especially third-generation high-thrust engines, are not easy to develop. Even the United States, with its superior aerospace technology, spent nearly twenty years developing third-generation high-thrust engines.

Meanwhile, the aero-engine engineers in the East would spend a year on the test bench, three years on an aircraft, and five years launching a satellite... That was a serious departure from the laws of engine development. The Taihang engine in later generations also took decades to develop!
From preliminary research in 1978 to finalization in 2005, it took 27 years, and it wasn't until after 2016 that it was truly mass-produced and equipped by the armed forces...

There are no shortcuts in the development of aero engines; we must be down-to-earth and take it one step at a time! If we're going to copy... it's easier to just copy the Russian engines!
Back in the family dormitory, I had just lain down on my bed when the phone rang.

"Hey."

"Liangzi, the Americans are chatting. They're not planning to send over the F100 engine; they want us to improve the F101 engine!"

A somewhat dissatisfied voice came from the other end of the phone.

Hearing what was being said inside, Qin Liang smiled and said, "F101 is fine too! We'll take whatever they give us. They're providing R&D funding and samples, and we can also use this opportunity to get a lot of technical data. Why not!"

Is the F101 outdated? Not at all. After all, the F101 not only transformed into the F110 and was installed on fighter jets, but its core engine was also equipped with the CFM-56 engine, becoming the main power source for commercial airliners!
The Taihang Mountains in later generations are said to be closely related to the CFM-56. Cough cough, I despise these guys who always try to find foreign fathers for Eastern technology!

The Americans acted swiftly; a few days later, the F101 engine was delivered, along with a large group of General Electric engineers. The team leader was an old acquaintance, Holmes Moses, and the technical lead was also an old acquaintance, Ted Inglenn.

Thinking about it carefully, Northwestern Polytechnical University doesn't seem to have had much contact with Pratt & Whitney, but it's already a familiar face to General Electric.

"Qin, we meet again!"

"Qin, I'm so happy that we can work together on the future engine project!"

"Yes, I am also very honored. Northwestern Polytechnical University has specially coordinated an independent laboratory for you. All future research and improvements will be carried out in this laboratory."

Qin Liang led the group to a bungalow, where the Americans looked at each other in bewilderment.

After the incident of the squid stealing technology, Northwestern Polytechnical University strengthened its management. It is allowed to cooperate with foreign companies, but they must be separated from the university's own research and development teams and physically isolated!

A large sign hangs at the entrance: Variable Cycle Engine Project Office.

The interior is quite spacious, with two rows of computers being the most prominent feature. In the center is a workbench where one of the two engines will be disassembled and modified first. In the corner are CNC machine tools and other processing equipment. To be fair, this kind of working environment is already quite good.

"Qin, we have reviewed your technological improvements. The modifications to the compressor blades and turbine guide vanes require a large amount of calculation... Can we use all of these computers ourselves?"

These Americans still don't want the East to have access to their engines!

"Of course, you can do the research yourselves if you want. Just come to us when you need our help. But the funding for the collaborative research and development must be paid to us according to the contract." Qin Liang has always been very generous to his friends.

"Okay, there's also... We always feel that with these technologies alone, we might still not be able to reach the true theoretical performance of the variable cycle engine."

"Well, besides those, there are other designs. For example, in front of the afterburner, we are designing a variable area duct ejector to direct the bypass airflow into the afterburner to achieve the combustion effect of a ramjet engine. We call this partial ramjet. It can also cool the combustion chamber and adjust the pressure matching of the core engine..."

Sure enough, there were quite a few hidden!
"Then can we have this technology?"

"Not yet. We've only just started our research, and there are still many technical challenges we haven't overcome."

"In that case...could we study it together?"

"Well, you guys can't go to our research lab."

"Please invite these people to work for us!"

"Okay, I'll go ask."

Engine system.

"Ding Jun, how's the research going, you guys?" Director Wang asked.

Ding Jun raised his head, revealing bloodshot eyes: "After these past few days of studying, we've almost mastered the basic principles, and we've memorized the structure of the F101 engine. The only remaining question is how to specifically match it with the engine..."

"For the specific matching, work with the Americans. Just memorize all this knowledge. Next, interact with the Americans more and learn from their experience. If you don't understand something, just act like you're confident. Well, this involves classified information, so we need to consult with them before deciding whether to tell you. Just use that as an excuse, understand?"

"Okay, I understand!"

　PS: The two above are structural diagrams of the YF-120 and schematic diagrams of different modes. The one below is a physical picture of the J58 engine. The large pipe is the conduit for switching between the two modes.

　　
　
(End of this chapter)