The Science Fiction World of Xueba

In the hall of the command and control center, Wang Yu, the chief commander of the 921 rocket launch, Liu Xuesong, the chief designer of the 921 rocket, Liu Yong, the deputy director of the 11th Institute of the Sixth Academy of Aerospace Engineering, who mainly focuses on the 921 core stage and the hydrogen-oxygen engine, and Liu Yong, the technical director of the 11th Institute of the Sixth Academy of Aerospace Engineering, who developed the liquid oxygen kerosene engine Wu Chunmin, director of Xi'an 11 Institute of the Sixth Academy of Aerospace Sciences, Li Yonghua of Aerospace 101 Institute who is responsible for engine ground testing and providing liquid hydrogen fuel, and Gao Junlong of the Aerospace Department of 54 Institute of China Electronics Technology who developed the ground safety remote control system are discussing nervously.

Pang Xuelin and Tao Yongchang stood aside and listened.

Under normal circumstances, if the engine pre-cooling fails and the rocket body is overheated, for such a low-temperature rocket powered by liquid oxygen kerosene and liquid hydrogen and liquid oxygen engines, it is not allowed to perform launch missions at all.

After the low-temperature rocket fuel is filled, the effective launch time is only 24 hours. Considering the factor of the launch window, the time left for everyone to discuss is very limited.

Wang Yu, the commander-in-chief of the launch, said: "The satellite has just sent a message that the launch window is from 17:30 to 19:00, and it can be postponed to 19:30 at the latest. It is now 16:40. Considering that one hour is reserved before the launch We still have about an hour to solve the problem for launch-related preparations. Lao Wu, you guys did the kerosene machine and the circulation pre-cooling system on it, please tell everyone about the situation sent back from the front.”

Wu Chunmin nodded and said: "The data sent back by the front sensor shows that after 2.5 hours of circulating precooling, the total fluid consumption of circulating precooling is 547.76kg, but the temperature of the pump casing is 15K higher than we expected, which is very strange. Normal. The temperature of the pump casing is an important parameter to measure the effect of pre-cooling. We usually take the temperature of the pump casing lower than a certain value as a sign of good pre-cooling, and use it as the starting condition of the engine. This time we use the core-level engine The improved version of YF100K adopts the natural convection cycle precooling mode. This mode is mainly to lead a section of pipeline before the main valve of the engine and connect it to the storage tank. We call this section of pipeline the return pipe. When the precooling starts, The propellant flows from the storage tank into the delivery pipeline, passes through the front valve of the pump, the pump cavity, enters the return pipe, and then flows through the return valve through the return pipe and returns to the storage tank.”

Wu Chunmin paused, and continued: "In this system, we don't have any external driving device, and the flow is only driven by the density difference between the return pipe and the propellant in the delivery pipe, so it is called natural convection cycle precooling. The reason 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, it is heated and vaporized, and the density becomes smaller, resulting in backflow. In order to enhance the density difference between the return pipe and the propellant in the delivery pipeline, To make the cycle run smoothly and ensure sufficient pre-cooling of the pump, a section of injection is usually added to the natural circulation pre-cooling. The injection tube is connected from the return line, and helium is used as the injection gas source. When appropriate, carry out Short-term helium ejection, enhanced circulation."

"Old Wu, is there any solution?"

Liu Xuesong said.

Wu Chunmin said: "I suggest organizing the operators of the first-level helium gas distribution platform to return to their operating posts.

Turn on D7 to blow off, carry out helium injection for about half an hour, strengthen the circulation, and see if the temperature of the pump casing can be lowered. "

Wang Yu looked around: "Does everyone have any opinions?"

Everyone shook their heads.

Wang Yu said: "Okay, then follow the old Wu's method first, and order the emergency personnel to be in place. If the pre-cooling still fails, the position will start preparations for terminating the launch process."

"yes."

Wang Yu's order was issued quickly.

On the large screen directly in front of the command center, the screen began to switch to the scene in the transmission tower ahead.

The entire command and control hall fell silent, and everyone patiently waited for the news ahead.

Wang Yu, Liu Xuesong, Liu Yong, and Tao Yongchang whispered to each other from time to time.

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

Wu Chunmin looked at Pang Xuelin, shook his head and smiled wryly: "Not sure, the cyclic precooling process is very complicated, involving many physical phenomena: when precooling starts, the pipeline system at room temperature forms a high temperature heat source relative to the low temperature medium, and the medium enters the tube. After the road is vaporized sharply, pure liquid, different proportions of vapor-liquid two-phase, and pure gas flow will appear along the pipeline. At the same time, the inner wall of the pipeline is cooled by the low-temperature fluid, which will release heat and reduce the temperature of the tube wall , and the air temperature will not change too much. In this way, there is a temperature gradient between the tube wall and the outside air, and thus a heat flow is generated from the outside to the inside. As the precooling progresses, the tube wall temperature gradually decreases, The distribution of the fluid state in the pipe is also constantly changing, until a certain moment, the wall temperature will no longer drop, the heat flow from the outside will no longer change, the fluid state at each point on the pipe will not change, and the pre-cooling will reach stability Here, we are most concerned about the distribution of various parameters after the system is stabilized, especially the temperature of the pump casing. During the previous experiments, there were no problems with the circulating pre-cooling system. Unexpectedly, something happened just before the launch. , the key point is that the liquid consumption of circulating precooling is equivalent to our theoretical calculation, but the temperature is 15K higher. Canceled, we can re-launch after we make further improvements to the circulating pre-cooling system..."

Pang Xuelin thought for a while and said, "Do you have a design plan for the kerosene engine circulation pre-cooling system, can you show it to me?"

"Of course it's 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 it and didn't pay too much attention to it.

Although Pang Xuelin has a great reputation, most of his achievements are in the fields of mathematics and natural sciences. They did not expect Pang Xuelin to be of any help in the field of highly specialized applied engineering such as rocketry.

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

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

The manual analyzes the natural circulation precooling theoretically through a series of calculations, including the numerical calculation of precooling liquid consumption and steady state. Judging from the results of numerical calculations, the natural circulation precooling effect of the engine's oxygen system is good, and basically there are no major design problems. Under normal circumstances, there should not be such a big flaw in the approaching launch stage.

Pang Xuelin frowned involuntarily.

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