The military-industrial scientific research system of the academic master

Chapter 1287 Liquid and solid, I want them all

After saying the half-joking words, Chang Haonan ignored the stunned Jiang Zonglin and put the report aside, then walked straight past Li Yabo and sat in front of the computer.

Although as the number of projects on hand and the size of the team increase day by day, he also has to understand a lot of work progress through regular reports that he once hated in his previous life.

But current research on the reaction mechanism of metal particles has far exceeded initial estimates.

For results like this that may have a disruptive impact on industries and even disciplines, Chang Haonan still prefers to see the results first-hand.

It's not that he doesn't trust Li Yabo, but that a lot of inspiration needs to be inspired by the process of analyzing the original data. Looking at the conclusion directly skips the most important thinking process, and it is easy to overlook certain points or make mistakes that are taken for granted.

The other three people then gathered behind Chang Haonan.

Driven by the Torch Group and TORC Multiphysics software for the entire numerical computing industry, in 2006, there were already many specialized software that could graphically render simulation calculation results to improve intuitiveness.

Even veterans like Chang Haonan or Li Yabo may not need the assistance of graphics technology during the calculation process, but in order to facilitate subsequent review, they will still set aside a certain amount of time and computing power for this purpose.

Even Xing Muchun, who had just been confused by what he heard, quickly saw some clues:

"It seems...that this part of the model ignores the rate at which chemical reactions occur, and assumes that convection and diffusion only occur in radial space?"

Of course, this question was not asked to Chang Haonan, but to Xiang Li Yabo.

So the latter immediately nodded:

"Objective computing power limitations... My calculations did not assume that particle combustion is a quasi-steady state process. Instead, I referred to the teacher's past methods of studying ultra-short laser processing of metals and added a large number of partial differential equations to the description of the combustion process. It is really There is no condition to consider the situation in a three-dimensional scene..."

“…”

Just when Xing Muchun wanted to ask something more, Chang Haonan, who had been staring at a certain page on the computer for a while, suddenly spoke:

"Yabo, if you modify your calculation results... wouldn't it be more appropriate to describe a solid-liquid mixed system?"

After a slight pause, he added:

"It can even be much simpler than the current unsteady dynamic-diffusion-evaporation control model. In addition, for solid-liquid systems, although the two-dimensional assumption still requires approximation in nature, at least the particle morphology band can be ignored. The accuracy is much higher than describing pure solid-state systems.”

Li Yabo's eyes flashed with lightning, and his eyes hurriedly turned to the part of the computer screen that Chang Haonan was pointing at.

However, there was no immediate response.

Instead, he lowered his head and thought for a moment.

"This is indeed true from a microscopic perspective on the particle surface... But considering the actual situation, the solid-liquid hybrid propellant should be very inconvenient to use, right?"

Chang Haonan waved his hand:

"The traditional solid-liquid mixing system is indeed not widely used... Mainly in the past, although this type of propellant was called solid-liquid mixing, its essence was to vaporize the liquid oxidant and spray it into a combustion chamber loaded with solid fuel, and then ignite it. The flame temperature causes the solid fuel to decompose and gasify to maintain combustion.”

"Under this working mechanism, because the oxidants are introduced from outside the combustion chamber, the decomposition products after gasification of the solid fuel can only form a diffusion flame with the oxidant. The burning surface is very close to the solid surface, and the intensity of thermal feedback cannot be very high. Therefore, the fuel transfer rate is not essentially different from that of traditional solid propellants, but it adds a lot of unnecessary trouble to the propellant filling and the overall structure design of the aircraft.”

At this point, he felt that the following content was a bit unintuitive just by dictating it, so he pulled a piece of paper from the side.

However, considering my abstract painting skills, I quickly changed my mind and opened the professional drawing software on my computer.

"But if the surface of the solid fuel can be melted to form a liquid film, then under the action of surface flow, the liquid will become unstable and atomize to form droplets and enter the gas phase, thereby greatly enhancing the mass transport of the fuel, that is, It is equivalent to increasing the retreat speed of fuel at the same time.”

"And in this way, the high retreat speed becomes a natural property of the fuel itself. There is no need to introduce additional additives, nor to adopt enhancement measures such as porous configurations or rotating nozzles, which significantly simplifies Propellant preparation process…”

“…”

When he was in charge of the space fishing ship project, Chang Haonan heard from Yin Liangxing that because the transfer rate of solid fuel is relatively low, in order to maintain a high enough combustion chamber pressure and generate enough thrust, a porous configuration is generally used. to increase the burning surface area.

Taking a typical HTPB as an example, a small charge requires 4 holes, while a large charge even reaches 32 holes.

On the one hand, this increases the size of the engine with the same propellant capacity and increases the difficulty of processing. On the other hand, it also causes the structural strength of the charge to decrease, which can easily cause internal fractures and cause accidents such as the pill to fall out.

Especially in high-acceleration flights such as hypersonic aircraft, hidden dangers will be more obvious.

Although liquid fuel does not have this concern, its flexibility of use and storage safety are not satisfactory. It may not have much impact on the launch vehicle, but it can be seen from the complicated preparation process before the test launch of the previous verification projectile. , does not quite meet the requirements of missiles, especially tactical missiles.

In contrast, this new solid-liquid mixed system exists in solid or semi-solid form during storage, and its combustion characteristics after entering the working state are close to that of liquid fuel, which is equivalent to having the advantages of both.

Of course, the cost of such a good thing cannot be reduced. But for a nationally important weapon like hypersonic weapons, efficacy is definitely more important than price.

Moreover, the application scope of this type of mixed propellant is not limited to the project at hand by Chang Haonan.

In the long run, most missile types that are not particularly size-sensitive can be switched from traditional solid propellants to the new system.

From an industrial perspective, production costs will be reduced accordingly after widespread application.

Li Yabo, who was standing behind Chang Haonan, had obviously thought of this at this moment, and his eyes gradually changed from the initial doubts to understanding.

Then he frowned again and fell into thinking:

"If this is the case, then not any liquid film will form atomized droplets under the action of flow, but also depends on the tension and viscosity of the liquid under working conditions...So the HTPB fuel we are currently studying will definitely not meet the requirements. A completely new type of propellant must be developed.”

Although Chang Haonan studies computational materials science, it is not a database after all, and he has not been exposed to many kinds of solid propellants in the past.

Therefore, professional matters must still be left to professionals:

"Old Xing, please contact Comrade Lin Chenggang immediately and ask him to come here..."

…

After receiving the news, Lin Chenggang thought it was a breakthrough in research on the AP/HTPB/AI system. After putting down the phone, he rushed to Huairou Science City without even having time to eat lunch.

However, after seeing Li Yabo's calculation results and hearing the new idea proposed by Chang Haonan, his first reaction was -

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The sky is falling.

Originally, he just wanted to make some improvements based on existing research.

But now…

Bad news: There was air leakage in the dilapidated house, and the painter who hired it didn’t understand it well.

Good news: The decorator is actually a construction guy, and he built a new one for you right next to it, just waiting for you to move in.

The only problem is that the experience of the past ten years or so may have to be updated...

Lin Chenggang spent a lot of effort to suppress his curiosity, and did not ask the other party how the two of them pulled off such a ruthless job within a month, and then focused on the report in front of him as quickly as possible. above.

I have to say that although this new idea is essentially drawing a cake, it is indeed very fragrant.

And just now when they were waiting for him to come over, Chang Haonan and Li Yabo had even roughly calculated a physical property range that met the requirements.

Lin Chenggang only needs to come up with one, or a type of feasible propellant as a matrix.

"Surface tension 6.5-8.0mN/m, viscosity 0.59-0.73mPa·s, melting point not less than 323K, boiling point not higher than 720K, heat of fusion less than 185kJ/kg..."

There are hundreds or even thousands of types of solid propellants, but after filtering through these dozen or so conditions, there are really not many left.

"It shouldn't be impossible, right?"

Looking at Lin Chenggang with an erratic expression, Li Yabo felt a little uneasy.

Fortunately, as soon as he finished his question, he heard the former uttering an answer:

"paraffin…"

"paraffin?"

This somewhat ordinary result surprised Li Yabo.

"Of course it is not ordinary paraffin, it needs to be modified and blended... But as a base fuel, alkanes with an average carbon number of about 30, which is what we often call paraffin, do meet all the requirements on this table... "

Chang Haonan didn't show much surprise, he just nodded calmly:

"Then I will make a copy of these results for you. When you go back, you can quickly verify whether paraffin-based fuel can meet the performance needs of the air-breathing super rocket booster stage!"

(End of chapter)