Chapter 1190 Unstable Combustion?

It was the afternoon when Chang Haonan and his team verified the double-cone warhead near Lianhai.

Ho Kyung.

Aerospace Science and Technology Group, Sixth Research Institute.

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

Inside, more than two dozen technicians dressed similarly to him were standing or sitting around a computer. Next to it was a whiteboard filled with formulas and schematic diagrams.

It looked like they were in a meeting.

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

It was researcher Chen Zhiwei who had previously attended the hypersonic weapons development conference on behalf of the Sixth Academy.

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

Stop immediately:

"Director Li?"

Everyone around him also turned around following this voice.

"Old Chen, comrades, good news!"

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

"I just received a notification from my superiors. This morning, Academician Chang and comrades from the First Academy of Sciences jointly conducted a double-cone warhead test in the Bohai Sea area with the Second Artillery Missile Force, and achieved a complete success!"

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

Even the estimated share of the entire Sixth Academy is relatively limited.

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

It just so happens that several of their ongoing projects can be used for actual technical verification.

Therefore, the hospital has also increased its attention to it by more than one level.

Of course, because the Sixth Institute itself has several key projects, the specific research and development work on Gao Gao is still led by Chen Zhiwei.

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

Only then did Li Bin be assigned as the person in charge of the research and development of the entire verification elastic power system in order to coordinate the resources of the entire hospital.

Now that the test 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 to be as happy as he expected.

"The warhead has reached the predetermined speed?"

After a few seconds, Chen Zhiwei asked.

But the tone seemed a little weird.

Li Bin suppressed his curiosity, nodded and replied:

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

After about another second, a burst of applause broke out in the test workshop.

On the surface it sounded quite enthusiastic, but it was obviously the kind of routine applause at a meeting.

At this moment, Li Bin couldn't care less about talking about warheads, and instead focused on the whiteboard and computer screen in the distance.

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

This made Li Bin's heart suddenly move:

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

Chen Zhiwei glanced back, then scratched the top of his head where there was not much hair left:

"yes……"

He turned around and sat in front of the computer, and read up a data graph:

"During the work test, we found that the engine had a large-amplitude pressure oscillation about five seconds after ignition. Although there have been no serious consequences due to this problem, we disassembled the engine after 30 seconds of operation. After inspection, the surface of many parts has shown obvious structural damage... It is difficult to fully maintain the expected working time. "

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

Li Bin suddenly 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.

While he was thinking this, he threw aside the two papers in his hand and quickly came forward to the side of the whiteboard. Then he took off his reading glasses, squinted his eyes and came closer.

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

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

However, obvious wrinkles have appeared on the side facing the inside, which is obviously due to some high-frequency strong impact.

This scene is quite familiar to him:

"It's indeed a bit serious, and..."

Li Bin put on his glasses again:

"A similar situation happened to a model I was developing here."

When Chen Zhiwei heard this sentence, he first looked happy——

This means that I can get support from other project teams in the hospital.

But then I felt that this reaction seemed inappropriate, so I quickly stiffened my expression:

"You mean... a high-thrust hydrogen and oxygen machine?"

As China has rapidly improved its orbital carrying capacity in recent years, the original rocket sequence consisting of Long March 2/3/4 has gradually been unable to meet demand.

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

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

Li Bin answered in a calm tone, and then immediately asked:

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

"Is it the supply system coupling type or the combustion chamber coupling type?"

In fact, this is also the biggest problem when it comes to problems at the entrance to the combustion chamber.

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

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

When something goes wrong, sometimes it's difficult to determine which system is causing it.

Fortunately, Chen Zhiwei is also an old engineer after all, with considerable experience and skills.

He nodded:

"Although it is not 100% certain, the oscillation frequency of the pressure signal is large, the oscillation period is long, and it is quite unstable. It is also found that there is a standing wave field corresponding to the inherent acoustic mode, which basically conforms to the characteristics of the coupling type instability of the combustion chamber. …”

After finishing speaking, he hesitated a little, but finally continued to give his judgment:

"And it's tangential combustion instability."

When Li Bin heard this, his eyes widened slightly, and then he showed a smile:

"Then it's exactly the same... The rocket engines in our institute all use cylindrical combustion chambers, inject fuel from the head, and organize combustion in an isobaric mode. There is a combustible mixture layer between the flame front and the injection panel. The temperature of the combustible mixture near the front is relatively high. Affected by the inherent instability mechanism of the flow field, it is easy to generate hot spots in the combustible layer, thereby inducing the formation of rotating detonation waves..."

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

Having said this, he glanced at Chen Zhiwei next to him:

"Although we are currently unable to theoretically determine the process mechanism and control rules of combustion instability, at the engineering level, we can still determine the specific location where the detonation wave is formed in the combustion chamber through simulation and experiments, and then determine whether to improve the injection process. Injection atomization process, jet mixing process or evaporation combustion process..."

"Under 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 unstable combustion."

As a disposable product, rocket engines have this advantage.

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 high-thrust cryogenic machines themselves are not used to carry people, and the requirements for system reliability are not as stringent as those of the Long 2F.

"Thank you very much."

Chen Zhiwei breathed a long sigh of relief.

However, before he and the technicians next to 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 number of trials, the cycle is quite long... My timetable is pretty good, I'm not too anxious, but you still have to consider whether you can keep up with the regular Academician’s progress requirements..."

really.

When these words came out, Chen Zhiwei's brows that had just relaxed wrinkled again.

After a long time, he sighed softly:

"There's nothing you can do about it... just work overtime!"