The military-industrial scientific research system of the academic master.

Chapter 1190 Unstable combustion?

On the afternoon of the same day, Chang Haonan and his team were verifying the double-cone warhead near Lianhai.

Ho Kyung.

China Aerospace Science and Technology Corporation, Sixth Research Institute.

Li Bin, director of the Cryogenic Liquid Propellant Engine Research Center, put on a light blue lab coat and hurried into an independent testing workshop.

Inside, more than twenty technicians dressed similarly to him were standing or sitting around a computer, with a whiteboard filled with formulas and schematics next to them.

It looks like they are in a meeting.

A middle-aged man with a slightly bald head stood in the middle, holding an antenna as a pointer and pointing at the whiteboard.

It was researcher Chen Zhiwei who had previously represented the Sixth Academy at the hypersonic weapons development conference.

The latter happened to turn around at this moment and saw Li Bin walking quickly from the door.

Stop the action immediately:

"Director Li?"

The people around also turned around following this shout.

"Lao Chen, comrades, good news!"

Li Bin kept walking, waving the two pieces of paper in his hand, his tone full of excitement:

"I just received a notice from my superiors. This morning, Academician Chang and his colleagues from the First Academy, together with the Second Artillery missile unit, conducted a double-cone warhead test in the Bohai Sea area, and it was a complete success!"

In fact, he was not originally a direct participant in the hypersonic power project.

Even the entire Sixth Hospital's expected share is relatively limited.

But Chang Haonan suddenly planned a verification bomb, which still used liquid fuel as power.

This is a good opportunity for them to conduct actual technical verification for several ongoing projects.

Therefore, the hospital has raised the level of attention to this issue by more than one level.

Of course, since the Sixth Academy itself has several key projects, the specific research and development work in the field of high-precision technology is still led by Chen Zhiwei.

However, things from the same unit will always have some similarities in technology.

Only then was Li Bin assigned to be the person in charge of the research and development of the entire verification missile propulsion system in order to coordinate the resources of the entire institute.

Now that the testing has made significant progress, Li Bin is naturally very encouraged.

However, he soon noticed that the twenty or so technicians in front of him did not seem as happy as he had expected.

"Has the warhead reached the predetermined speed?"

After a few seconds, Chen Zhiwei asked a question.

But the tone seemed a little strange.

Li Bin suppressed his curiosity and nodded and replied:

"Yes, and the terminal seeker was successfully powered on... although the seeker itself is also a temporary replacement."

About a second later, applause broke out in the testing workshop.

On the surface it sounded quite enthusiastic, but it was obviously the kind of routine applause that occurs in meetings.

At this point, Li Bin had no time to talk about the warhead anymore, and instead focused his attention on the whiteboard and computer screen in the distance.

As a professional technician, he quickly realized that the above were the control equations and corresponding decoupling methods of the rocket combustion chamber-nozzle model.

This made Li Bin suddenly moved:

"Is this... a combustion stability problem?"

Chen Zhiwei looked back, then scratched his head, which had very little hair left:

"Yes……"

He turned around and sat in front of the computer, and pulled up a data chart again:

"During the working test, we found that the engine had a large pressure oscillation about five seconds after ignition. Although there have been no serious consequences so far, we disassembled the engine for inspection after 30 seconds of operation and found that many parts had obvious structural damage on the surface... It is difficult to maintain the expected working time."

As he spoke, he stretched out the telescopic antenna in his hand and pointed it at a photo that was pressed on the whiteboard by a magnet.

Li Bin immediately understood the reason for the scene just now——

I had just encountered difficulties in my work, but when I turned around, I heard that my teammates had made significant progress.

It's really hard to be happy about this.

As he thought this, he threw the two pieces of paper in his hand aside and walked quickly to the side of the whiteboard. Then he took off his reading glasses and squinted his eyes as he moved closer.

It was a metal blind plate about 15 cm in diameter.

It should be used on a fuel delivery valve at the entrance of the combustion chamber.

However, obvious wrinkles appeared on the inner side, which was obviously caused by some high-frequency and strong impact.

This scene was quite familiar to him:

"It's really serious, and..."

Li Bin put on his glasses again:

"A similar situation happened to occur with a model I'm developing."

Chen Zhiwei was delighted when he heard this.

This means that I can get support from other project groups in the institute.

But he immediately felt that this reaction was inappropriate, so he quickly tightened his expression:

"You mean... a high-thrust hydrogen-oxygen engine?"

With China's rapid improvement in orbital carrying capacity in recent years, the original rocket series consisting of Long March 2/3/4 has gradually been unable to meet the demand.

The task of developing a new generation of larger thrust rocket engines naturally falls on the Sixth Academy.

"Yes, but we are also looking for a solution, which may require many rounds of iterative experiments..."

Li Bin answered calmly, and then immediately asked:

"Can you now analyze the cause of this instability?"

“Is it supply system coupled or combustion chamber coupled?”

In fact, this is also the biggest problem at the entrance of the combustion chamber.

The high-frequency combustion instability problem is essentially a coupling resonance phenomenon between a series of combustion sub-processes such as propellant delivery, atomization, evaporation, mixing, chemical reaction, etc. and the disturbance field inside the combustion chamber.

The entrance to the combustion chamber is right at the junction of the two major systems of the rocket engine.

When something goes wrong, it is sometimes difficult to determine which system is causing the problem.

Fortunately, Chen Zhiwei is an experienced engineer after all, with rich experience and skills.

He nodded:

"Although we cannot be 100% sure, the oscillation frequency of the pressure signal is large, the oscillation period is long and it is quite unstable. In addition, we have found a standing wave field corresponding to the inherent acoustic mode, which basically meets the characteristics of the combustion chamber coupled instability..."

After saying this, he hesitated for a moment, but finally continued to make his judgment:

"And it's tangential combustion instability."

Li Bin's eyes widened slightly when he heard this, and then he smiled:

"That's exactly the same... The rocket engines in our institute all use cylindrical combustion chambers. Fuel is injected from the head and combustion is organized in an isobaric mode. There is a combustible mixture layer between the flame front and the injection panel. The combustible mixture close to the front has a higher temperature. Affected by the inherent instability mechanism of the flow field, it is very easy to generate hot spots in this combustible layer, thereby inducing the formation of a rotating detonation wave..."

"Of course, rotating detonation itself is a new technical route, but the premise is that the detonation phenomenon can be effectively predicted and controlled... If an uncontrolled detonation phenomenon occurs in our traditional rocket engine, it is likely to induce tangential combustion instability."

At this point, he glanced at Chen Zhiwei next to him:

"Although we cannot theoretically determine the process mechanism and control law of combustion instability, we can still determine the specific location of the detonation wave in the combustion chamber through simulation and experiment at the engineering level, and then determine whether to improve the injection atomization process, jet mixing process or evaporative combustion process..."

"In the most ideal situation, it may only be necessary to fine-tune the specific cross-sectional shape of the combustion chamber to greatly alleviate the oscillation amplitude and frequency of combustion instability."

Rocket engines are disposable, which is a good thing.

Even if many problems cannot be completely solved, we can still settle for the next best thing.

Just make sure there are no problems during its short working life of a few minutes.

These large-thrust cryogenic engines are not used to carry passengers, and the requirements for system reliability are not as stringent as those for the Chang-2F.

"Thank you very much."

Chen Zhiwei let out a long sigh.

However, before he and the technicians beside him could completely relax, Li Bin changed the subject:

"But don't be too happy too soon..."

"This method sounds simple, but because it requires a lot of experiments, the cycle is quite long... My schedule is fine, so it's not too urgent, but you still have to consider whether you can keep up with the progress requirements of Academician Chang..."

really.

After saying this, Chen Zhiwei's brows, which had just relaxed, frowned again.

After a long time, he sighed softly:

"That can't be helped... Let's work overtime!"