Why are aircraft engines so difficult? Can't the Chinese create advanced aircraft engines?

Let’s first understand that modern advanced aero engines, modern fighter jets, military transport aircraft, civil aviation trunk passenger aircraft, etc. all use turbofan engines.

Simply put, the turbofan engine has two concentric ducts, consisting of five parts: fan, compressor, combustion chamber, turbine, nozzle, etc.

Among them, compressors, combustion chambers and turbines are often collectively called the core engines of the engine. The difference between turbofan engines for fighters and transport aircraft and civil aviation passenger aircraft is mainly the fan. The engines of passenger aircraft generally use large-diameter fans to reduce fuel consumption; the diameter of the engine fans of fighters is generally small for supersonic flight.

Air flows in from the inlet of the turbofan engine, compresses by the compressor, and mixes and burns with kerosene in the combustion chamber. The high-temperature and high-pressure gas expands through the turbine and nozzle, and finally sprays out from the tail nozzle at a high speed.

Part of the thrust of the turbofan engine comes from the reaction force generated by the injection of gas; the other part is a turbo-driven fan, which rotates and drives air and is sprayed through the outer duct of the engine.

Why is turbofan engine so difficult? Imagine that the maximum afterburner thrust of the Al-31 turbofan engine of the Su27 is 12.5 tons, and two Al-31 units can push the Su27, which is more than 20 tons, to fly at more than twice the speed of sound. However, the fan diameter of the Al-31 is less than 900 mm and the turbine diameter is less than 300 mm.

According to basic physics principles, forces interact, that is to say, a fan of such a small size has to bear 12.5 tons of force at all times.

To put it more vividly, everyone should have seen the performance of a strong man pushing a car with a steel gun in his throat. The same is true for the turbofan engine. It is just that the strong man pushes the car and moves slowly. The turbofan engine needs to push the aircraft to fly at twice the speed of sound, and all components must withstand the test of extremely harsh high temperature and high pressure.

In addition, a turbofan engine used for a supersonic fighter is generally only about 1 meter in diameter and about 4 meters in length. Taking Al-31 as an example, such a small cylindrical object is to be stuffed into a 4th-level fan, a 9th-level compressor, and a 2nd-level turbine, which can converge-expanding nozzle, a combustion chamber, and afterburner. Cooling air channels must be arranged between them, and fuel control systems must be installed around them.

Therefore, designing and manufacturing a high-performance turbofan engine can be said to be extremely difficult to "make a dojo in a snail shell". In the world, only the UK, Luo Luo, the United States, Puhui and General Motors, are the second-rate companies, Russia and France, which are both second-rate, which is a real monopoly industry.

To describe it professionally, if the turbofan engine needs to achieve greater thrust and lower fuel consumption, the first thing to do is to increase the boost ratio and improve thermal efficiency. The temperature before the turbine is an important indicator for measuring thermal efficiency.

For example, the front temperature of the Al-31 engine of the third-generation Su27 is 1665k. The -119 engine of the fourth-generation -22 raises this indicator to 1977k; the front temperature of the Al-31 is still below the melting point of ordinary steel, but the -119 has exceeded about 200 degrees.

Tianfeng Technology's turboshaft D and turboshaft e engines have a pre-turbo temperature of below 2,000k, while the turbofan engine that is currently being developed has a pre-turbo design temperature of 2,100k.

To work normally at such a high temperature, the third generation of single crystal hollow blades must be used. What is a single crystal hollow blade is difficult to describe here. It can only be said that a blade with an area of ​​only a few square centimeters has a large number of free surfaces and a complex inner cavity (for air intake cooling). It is also necessary to control the continuous and consistent production of alloy crystals, which requires extremely advanced precision casting technology.

Li Tianfeng stayed in the helicopter manufacturing plant for two days. Considering that there are many things in his company, especially the turbofan engine being developed, it is now at a critical moment. Li Tianfeng returned to Tianfeng Technology Company two days later.

………

China Business-Using Aircraft Co., Ltd.

This is a professional civil passenger aircraft manufacturer. When it comes to Xiang-Feng regional passenger aircraft, everyone may be familiar with it. This civilian regional passenger aircraft is an excellent product of this company (do not link it with reality).

Xiang-Feng regional passenger aircraft is known as the "new generation of regional aircraft in the 21st century". It is a regional aircraft developed by China Shang-Yong Aircraft Co., Ltd. In addition to the aircraft engine provided by General Electric, Xiang-Feng is the first regional aircraft designed and manufactured by China.

The aircraft underwent its first test flight in 2008. After obtaining the airworthiness certificate in 2009, it will be delivered to customers for commercial operation. Xiang-Feng regional passenger plane has four models with different capacity, and the passenger model can be equipped with about 70 to 100 seats.

As a deputy general manager and one of the senior executives of COMAC, Shen Wensheng was frowning and smoking. Whenever something difficult or troublesome, Shen Wensheng would do this.

There were already many cigarette butts in the ashtray on the desk, and there was also a clear smell of smoke in the entire office.

"It's really bad to feel stuck in your neck!" Shen Wensheng thought to himself while smoking.

At present, Shang-Fei Company has a very good development momentum. Xiang-Fei regional passenger aircraft is selling well in the domestic market and has a very good reputation. Shandong Airlines, Shanghai Airlines, Xiamen Airlines and other companies have signed orders with Shang-Fei Company for hundreds of aircraft.

According to this momentum, in a few years, the Xiang-Feng regional passenger plane may be able to go abroad and enter the international market. Shen Wensheng, who is only in his forties, is honest and strong, full of energy, and is ready to do a big move.

At this critical moment, as the supplier of Xiang-Feng regional passenger aircraft engines, the American Ge Company has made it clear that starting next year, the supply of engines will be reduced, and the price of each engine will increase by 10%.

After smoking several cigarettes in a row, Shen Wensheng had no idea in his mind. He sighed and thought, "It would be great if the domestic aircraft engine was powerful. Alas, it seems that he could only be stuck in his neck by Ge Company."

"I'm really unwilling to give up!"

Shen Wensheng thought in his mind that the reduction in engine supply means that the production of Xiang-Feng regional passenger planes has not increased but decreased, and the hope of a big fight may be ruined.

After thinking for a long time, Shen Wensheng picked up the phone and called his Minister of Commerce over, "Mr. Li, you know about ge, and try to contact Puhui and Luoluo, to see if there is any hope."

Minister Li of the Ministry of Commerce nodded helplessly. Knowing that things have come to this point, he could only try to get involved with these aircraft engine giants, but there is definitely little hope.

Minister Li said: "Mr. Chen, I will try to work hard, but..."

Seeing that Minister Li was a little hesitant, Shen Wensheng didn't know what it meant, and waved his hand and said, "Let's try it first, there's no hope."

Seeing Minister Li lower his head and retreating, Shen Wensheng sighed again and thought to himself, it would be great if a domestic aviation engine company could have an excellent turbofan engine.

In his mind, Shen Wensheng passed the domestic national aviation companies one by one, but he really didn't have the aircraft engine he needed.

At present, even if domestic national aviation industry enterprises develop turbofan engines, they are still for military aircraft. Moreover, the engines of military fighter jets are not strong enough, so their own civilian regional passenger aircraft should not try to find excellent and suitable aircraft engines in China.

After thinking for a long time but failing, Shen Wensheng could only sigh again.

Tianfeng Technology Company's turboshaft d and turboshaft e have been entitled to produce, especially the turboshaft d engine, which has produced nearly a thousand units. Now, it is still producing at a rate of about seven or eighty units per month.

People in the domestic aviation industry basically know these two turboshaft engines and agree with them very much, knowing that these two excellent turboshaft engines are rarely known because this turbofan engine is far from being designed and projected.

Shen Wensheng didn't know that this excellent turbofan engine was normal. Even insiders in the aviation industry knew that it was not many people.

Friends like Zhang Haiping, Yang Xianfeng, etc., only know that Tianfeng Technology Company is developing the fourth-generation turbofan engine, and it is not very clear about some very specific things.

…………

Tianfeng Technology Company, casting workshop.

The casting of titanium alloy compressor receivers has begun. Before casting, Zeng Qinghai specially organized a process review to improve and improve the casting process regulations again. After confirming that there is no problem, the casting of the first batch of compressor receivers began.

Because it was the first batch of titanium alloy receivers, the casting batch was not large, and because it was the first batch of casting, considering the difficulty of the process, Li Tianfeng and Zeng Qinghai were both in the casting workshop.

"Mr. Li, Mr. Zeng, the casting preparations have been completed and you can do casting."

Li Tianfeng waved his hand and said, "Then start casting and see what will happen to our first batch of titanium alloy receivers?"

This is a titanium alloy receiver with a thin-walled complex structure. It is hard to say whether it can succeed at one time, and Li Tianfeng is not sure.

Precision casting, preliminary preparation work, takes the most effort, such as mold design and manufacturing, mold making before casting, melting of titanium alloys, etc.

Of course, the process parameters of casting will be strictly controlled and there must be no sloppy, otherwise, it may cause the scrapping of defective products or even castings. You must know that this is the casting of a highly difficult titanium alloy complex thin-walled receiver, representing the highest level of domestic casting.

From a distance, through the glass, watching the titanium alloy liquid injected into the mold, Li Tianfeng's face was very serious. The whole scene was quiet and no one spoke.

…………

Two updates will be continued today, and the second update will be given! (To be continued...)
Chapter completed!