Chapter 1474 When in doubt, quantum...chemistry?

at the same time.

In the opinion meeting room of Huairou Science City, on the outskirts of Beijing.

"let's start."

Chang Haonan's voice was so calm that no emotion could be heard.

After the DF-17 was publicly displayed, superiors were shocked by the huge positive impact it had. As a result, they greatly increased the research and development resources poured into the field of air-breathing hypersonic aircraft, and the authority of the entire project team also increased accordingly.

But along with it comes invisible pressure.

Now, the more advanced air-breathing hypersonic missile is stuck with the heat dissipation problem of the "Lingxiao-1" engine, which is indeed a situation that no one had expected before.

Xing Muchun pushed his glasses and turned on the projector. Five sets of complex flow channel structure diagrams and data curves were displayed on the screen: "According to the requirements of the last meeting, I led the team to try five different cooling channel optimization solutions."

The red laser pointer points to the chart. "Scheme 3.5 performs best. Under the premise of unchanged physical size, the fuel residence time is extended by %."

He didn't give any comment, but a slight sigh was heard in the conference room.

Due to the limitations of testing conditions, the consistency of ultra-high-speed aerodynamic data itself is relatively poor.

3.5% can only be said to have just exceeded the scope of "random error".

"This is far from enough." Chang Haonan put down his pen. "Under these conditions, the heat sink potential of JP7 fuel can only be exerted at about 65%. Extending the residence time by 3.5% will basically have a negligible effect on the improvement of cooling capacity."

Li Min, the general system engineer sitting next to Xing Muchun, quickly called up another set of data:

"Under the coordination of Director Li of the Industry and Construction Commission, we tested seven high heat sink value fuels through several research institutes in the chemical industry system." She pointed to a set of red curves, "but their performance is not fundamentally different from JP7 and JP8, and the cost is even higher."

After obtaining a large amount of additional resources, Jiang Zongli returned to his old job and took the lead in the research and development of the next-generation JF series wind tunnels. Li Min, who was originally responsible for coordinating wind tunnel testing and verification aircraft development, then "inherited" the position of second deputy chief engineer.

"And it will cause carbon deposit problems." Chang Haonan directly pointed out the key point, "The components of these fuels are too complex. During the mode conversion process, carbon deposits may directly cause engine failure."

The conference room fell into silence for a moment.

"Guys, we may be going in the wrong direction."

Chang Haonan stood up and walked to a whiteboard. He drew a smooth arc on the board with the tip of his pen.

"It is probably difficult to meet the cooling requirements above Mach 10 simply by optimizing the flow path or finding ready-made high heat sink fuels."

Writing and drawing on the small blackboard is a habit he brought over from the 90s, but he has changed it to a less dusty version to keep up with the times.

He drew a simple diagram of the molecular structure:

"From a chemical point of view, the cleavage reaction follows a free radical mechanism. The rate of the entire reaction is determined by the slowest step - in this case, the cleavage of the C-C bond to produce the alkyl radical."

Then, a more complex diagram:

"If we add a substance to a hydrocarbon fuel...here we use n-heptane as an example, whose activation energy is weaker than the carbon-carbon bond and can preferentially break at a lower temperature to produce free radicals..."

His hands were a little slow and he was only halfway through the painting, so he didn't start the next sentence immediately after he finished speaking.

But someone has already guessed what's next:

“Initiator…”

It’s Li Yabo.

The coffee cup in front of him was empty, but his eyes were surprisingly bright: "Nitroethane!"

There aren't many chemistry experts on site, but we do have some understanding of some of the properties we come into contact with every day.

Soon someone wondered:

"But I remember...the bond energy of the carbon-nitrogen bond should be stronger than the carbon-carbon bond?"

This time, Chang Haonan followed up with the answer directly:

"The carbon-nitrogen bond is indeed stronger, but the activation energy required for the free radical decomposition reaction is no more than 200 kJ/mod, so nitroethane does meet our requirements."

He quickly returned to the computer and pulled up the database on the screen:

"The only problem is that the results of scramjet engines have determined that changes in fuel composition may directly lead to changes in combustion characteristics, unlike conventional aircraft engines where you can just add additives... So, we have to arrange a test under relatively conservative conditions first."

……

Three days later, at 4:17 in the morning, the wind tunnel center was brightly lit.

Chang Haonan stood in front of the explosion-proof glass of the control room, watching the technicians install the "Lingxiao-1" engine model into the test section. The fiber optic data cable as thin as a hair extended from the surface of the wind tunnel like a spider web and connected to the data acquisition system.

"The fuel is ready." Xing Muchun's voice came from the intercom with a slight electronic noise, "The mixed fuel has passed the flash point test and viscosity test."

Chang Haonan pressed the call button: "Start injecting 0.5% fuel." He turned and looked at the data screen, which began to display various parameters of the fuel system.

In the simulation, pale yellow fuel slowly flows into the cooling channel of the engine model.

“The temperature gradient is ready,” Li Min reported. The screen in front of her displayed a three-dimensional thermal map of the entire model. “The main heater has reached the preset temperature and is ready to start.”

Chang Haonan nodded, his eyes sweeping across the twenty-odd screens in the control room. A technician sat in front of each screen, with different colored labels on the keyboards in front of them, indicating the system they were responsible for. "Start the low-speed precooling system." He ordered, his voice was particularly clear in the tense atmosphere.

With a low hum, the wind tunnel's compressor began to operate.

The floor of the control room vibrated slightly, and fine ripples appeared on the surface of the water in the teacup.

On the main screen, the air flow curve begins to climb.

"Ignite!" The timekeeper's voice suddenly increased.

Everyone held their breath involuntarily.

In an instant, the infrared screen was flooded with dazzling white light. Even through the screen, the people in the control room seemed to be able to feel the vigorous energy inside the wind tunnel.

The moment the countdown ended, a blue plasma flame spurted out from the tail of the engine model, and dozens of curves on the monitoring screen began to fluctuate violently at the same time.

Chang Haonan's eyes were fixed on two key parameters: the pressure and temperature of the inner wall of the combustion chamber.

“The combustion was stable and the wall temperature under simulated conditions was lower than in the previous test…”

There was suppressed excitement in Li Min's voice.

But this excitement lasted less than 5 seconds.

On another screen, red patches representing hot areas were moving erratically within the combustion chamber, like a wildfire blown by the wind - evidence that changes in fuel properties were indeed affecting combustion stability.

"Stop testing and start the cooling procedure." Chang Haonan gave the order, while making a note of this key phenomenon in his mind.

The entire control room immediately became busy, with various commands coming one after another.

When the engine model was taken out, its surface had turned dark red, and the protective covers at several temperature measuring points even showed signs of melting.

The technicians quickly began to collect various data, and Chang Haonan had already returned to the conference room with the core team.

A few hours later, the atmosphere in the same conference room became noticeably more lively.

Xing Muchun pointed to the data chart on the screen excitedly: "The effect of adding 0.5% nitroethane is already very obvious! The heat sink value is 7% higher than that of pure JP7.7, and the engine wall temperature is reduced by about 85K!"

"But problems have also arisen." Li Min called up another set of curves with dramatic fluctuations. "The location of the thermal congestion in the supersonic combustion chamber has experienced huge fluctuations. At a 0.5% addition, the fluctuation range has reached 170% of the design upper limit."

Chang Haonan stared at the jagged curves:

"This shows that the whole system is more sensitive than we thought. Small changes in the properties of the fuel will be amplified layer by layer through the combustion wave, pressure field and shock wave system. Moreover, this is only the state of Mach 7.5, and the test model has already shown obvious signs of melting. If it is increased to Mach number above 10, it may cause work to stop or even thermal runaway."

After a pause, he continued:

"This Lingxiao-1 prototype can no longer be used. In other words, even if our current research resources are quite abundant, it is unlikely to conduct actual tests on every additive ratio... The cost control department will go crazy."

Li Yabo hesitated for a moment:

"I can try to simulate it using reaction molecular dynamics. Although JP7 has a complex composition, we can first analyze the two main components, n-heptane and methylcyclohexane..."

"It's not accurate enough." Chang Haonan shook his head. "The molecular dynamics model cannot accurately describe the interaction of this multi-component system under extreme conditions. The errors will accumulate and amplify."

He walked to the window and looked at the outline of the JF14 wind tunnel in the distance:

"Also, your structural calculations on negative refractive index materials are still in progress, so don't distract yourself too much for now."

"I have also been involved in some computational chemistry research before. If Professor Li doesn't have time..."

Just as Li Min was about to show off, Chang Haonan raised his hand to stop her:

"I have to come in person this time."

"Quantum chemical calculations may be able to solve the problem."