In the lobby of the command and control center, Wang Yu, commander-in-chief of the 921 Rocket Launch, Liu Xuesong, chief designer of the 921 Rocket, Liu Yong, deputy director of the 11 Technical Director of the 11 Institute of the Sixth Institute of the Sixth Institute of the Aerospace, which is responsible for the 921 core stage and hydrogen and oxygen engines, Wu Chunmin, director of the 11 Institute of the Xi'an Institute of the Sixth Institute of the Aerospace, which is responsible for the engine ground interview and the provision of liquid hydrogen fuel, Gao Junlong, and other big bulls are discussing nervously.

Pang Xuelin and Tao Yongchang stood aside and listened.

Generally speaking, if the engine is pre-cooled and the arrow body is overtempered, this low-temperature rocket that uses liquid oxygen kerosene and liquid hydrogen and liquid oxygen engines as powered by low-temperature rockets are not allowed to perform launch missions at all.

The effective launch time after filling the low-temperature rocket fuel is only 24 hours. Considering the launch window, the time left for everyone to discuss is very limited.

Wang Yu, the chief commander of the launch, said: "The satellite just sent a message. The launch window is 17:30 to 19:00, and the latest can be postponed to 19:30. Now it is 16:40. Considering that one hour is reserved for launch related preparations, we still have about an hour to solve the problem. Lao Wu, the kerosene engine and the above circulation pre-cooling system are what you did. Tell you about the situation sent back from the front."

Wu Chunmin nodded and said, "The data sent back by the sensor in the front shows that after 2.5 hours of circulation pre-cooling, the total liquid consumption of circulating pre-cooling is 547.76 kg, but the pump casing temperature is 15k higher than we expected, which is very abnormal. The pump casing temperature is an important parameter to measure the pre-cooling effect. We usually use the pump casing temperature below a certain specified value as a sign of pre-cooling, and use this as the engine starting condition. This core-level engine uses the improved yf100k, which adopts a natural convection circulation pre-cooling mode. This mode mainly leads out a section of pipeline in front of the main valve of the engine and connects it to the storage box. We call this section of pipeline a return pipe. At the beginning of pre-cooling, the propellant flows from the storage box into the delivery pipe, passes through the front valve of the pump, the pump chamber, enters the return pipe, and then flows through the return pipe through the return valve and back to the storage box."

Wu Chunmin paused and continued: "In this system, we do not have an external drive device, and the flow is only driven by the density difference between the propellant in the return pipe and the conveying pipe, so this is called natural convection circulation pre-cooling. The reason for the density difference is that due to the low temperature characteristics of the propellant, the ambient air forms a relatively high-temperature heat source. After the propellant enters the pipeline, the propellant is heated and vaporizes, and the density becomes smaller, thereby generating reflux. In order to enhance the density difference between the propellant in the return pipe and the conveying pipe, the circulation proceeds smoothly, and ensure sufficient pre-cooling of the pump, a section of induced injection is usually added to the natural circulation pre-cooling. The induction pipe is connected to the reflux pipe, and helium is used as the induction gas source. At appropriate times, a short-term helium is induced to enhance the circulation."

"Old Wu, is there any solution?"

Liu Xuesong said.

Wu Chunmin said: "I suggest organizing the operator of the first-level helium gas distribution table to return to the operating position, turn on the d7 and blow off, perform helium injection for about half an hour to enhance the circulation, and see if the temperature of the pump casing can be lowered."

Wang Yu looked around: "Everyone has no objection, right?"

Everyone shook their heads.

Wang Yu said: "Okay, then follow Lao Wu's method first, and order the rescue personnel to take their seats. If the pre-cooling still fails, the position will start to prepare for the termination of the launch process."

"yes."

Wang Yu's order was issued soon.

On the large screen directly in front of the command center, start switching the screen to the scene inside the launch tower in front.

The entire command and control hall was quiet, and everyone was patiently waiting for the news ahead.

Wang Yu, Liu Xuesong, Liu Yong, Tao Yongchang and others whisper from time to time.

At this time, Pang Xuelin asked Wu Chunmin in a low voice: "Professor Wu, are you sure to lower the temperature of the pump casing in this way?"

Wu Chunmin looked at Pang Xuelin and shook his head and smiled bitterly: "Uncertainty, the circulating pre-cooling process is very complicated, and there are many physical phenomena involved: the pre-cooling starts, and the pipeline system at room temperature forms a high-temperature heat source relative to the low-temperature medium. After the medium enters the pipeline, it vaporizes sharply, and pure liquid, different proportions of vapor and liquid, and pure air flow will appear along the pipeline. At the same time, the inner wall of the pipeline is subject to the cooling effect of the low-temperature fluid, which will release heat and reduce the temperature of the pipe wall, and the air temperature will not change too much. In this way, there is a temperature gradient between the pipe wall and the outside air, and thus a heat flow transmitted from the outside to the inside. As the pre-cooling progresses, the temperature of the pipe wall gradually decreases, and the fluid state distribution in the pipe continues to occur.

Change, until a certain moment, the wall temperature no longer drops, the heat flow transmitted from the outside world no longer changes, the fluid state at each point on the pipeline will no longer change, and the pre-cooling will reach stability. Here, what we are most concerned about is the distribution of various parameters after the system is stable, especially the pump housing temperature. In the previous experiment, there was no problem with the circulating pre-cooling system. Unexpectedly, there was a situation before launch. The key is that the circulating pre-cooling liquid consumption is equivalent to our theoretical calculation, but the temperature is 15k higher. There must be problems here. If the method of enhancing the circulating circulation through helium emission is still not possible, then this launch task can only be cancelled, and we can only re-launch after we further improve the circulating pre-cooling system..."

Pang Xuelin thought for a while and said, "Do you have a design plan for the kerosene circulating pre-cooling system here? Can you show me how to show it?"

"Of course convenient!"

Wu Chunmin smiled and waved to a staff member, asking him to bring the yf100k design manual.

Wang Yu, Liu Xuesong and the others just glanced at each other and didn't care too much.

Although Pang Xuelin is very famous, most of his achievements are in the fields of mathematics and natural sciences. They do not expect Pang Xuelin to help with the fields of highly professional application engineering such as Rockets.

Pang Xuelin didn't care at all and directly found the theoretical calculation part of the cyclic pre-cooling system through the catalog page of the design manual.

The theoretical calculation of circulating pre-cooling systems is mainly divided into two aspects. The first is liquid consumption calculation, and the other is circulating calculation.

The manual uses a series of calculations to analyze the natural cycle pre-cooling in theory, and the calculation content includes the numerical calculation of the pre-cooling liquid consumption and the steady-state calculation. Judging from the numerical calculation results, the engine's oxygen system uses natural cycle pre-cooling with good effect, and basically no major design problems. Under normal circumstances, such big mistakes should not occur when the launch stage is approaching.

Pang Xuelin's brows couldn't help but frown.
Chapter completed!