What do you think are the most important scientific and technological achievements of modern China a

Discharge cooling is another type of convection cooling. Unlike regenerative cooling, the coolant used for exhaust cooling absorbs heat to the thrust chamber and is discharged out of the combustion chamber instead of entering the combustion chamber to participate in combustion. Direct drain coolant reduces the thrust chamber specific impulse, so the coolant flow for drain cooling needs to be minimized while only using drain cooling at the outlet section of the nozzle that is relatively less heated.

There is also radiative cooling, in which the heat flow is transferred from the combustion products to the thrust chamber, and then the heat is radiated by the thrust chamber wall to the surrounding space. Radiative cooling is characterized by simplicity and small structural mass. It is mainly used in the extension section of large nozzles and the thrust chamber of small thrust engines using high-temperature resistant materials.

When cooling in the thrust chamber of the tissue, a relatively low temperature liquid or gas protective layer is established on the surface of the thrust chamber wall to reduce the heat flow to the thrust chamber wall, reduce the wall temperature, and achieve cooling. Internal cooling is mainly divided into three methods: internal cooling (shield cooling), membrane cooling and diaphoretic cooling of head tissues. After the internal cooling measures are adopted in the thrust chamber, the mixing ratio near the wall of the combustion chamber is different from the optimal mixing ratio in the central area (in most cases, the near-wall layer rich in fuel is used) due to the need to reduce the temperature of the protective layer, resulting in the uneven distribution of the mixing ratio along the cross-section of the combustion chamber, so that the combustion efficiency is reduced to a certain extent.

Membrane cooling is similar to shield cooling in that it cools the thrust chamber wall by establishing a uniform and stable coolant film or air film protective layer near the inner wall surface, except that the coolant used to establish the protective layer is not injected by the injector, but is supplied through a special cooling belt. The cooling band is generally arranged in a cross-section of the combustion chamber or the convergence section of the nozzle. There can be several cooling bands along the length of the combustion chamber.

In order to improve the stability of the membrane, the coolant often flows through the gaps or small holes in the cooling belts, and when sweating is used, the thrust chamber wall or part of the inner wall is made of porous material with a pore diameter of tens of microns. Porous materials are usually sintered with metal powders or pressed with metal mesh. In this case, the number of pores per unit area is increased by making the micropores in the material as evenly distributed as possible.

The liquid coolant penetrates into the inner wall, creating a protective film that reduces the density of the heat transferred to the wall. When the flow rate of liquid coolant used for sweat cooling is above a certain threshold, a liquid film is formed near the wall of the thrust chamber. When the coolant flow rate is below the critical flow, the inner wall temperature will be higher than the coolant boiling point at the current pressure, and some or all of the coolant will evaporate, forming an air film.

In addition to the above thermal protection, there are other thermal protection methods such as: ablation cooling, thermal insulation cooling, hot melt cooling and composite protection of chamber walls. 3. Thermal protection scheme of high enthalpy gas generator Based on the above methods and the actual situation, the thermal protection method of high enthalpy gas generator is obtained.

The combustion chamber of a high-enthalpy gas generator differs from that of a liquid rocket engine, eliminating the front thrust chamber part, making its structure simpler and more effective. Then, the thermal protection involved is the thermal protection part of the combustion chamber wall. As the fuel enters the combustion chamber, it quickly decomposes and releases large quantities.

In the past decade, the important achievements of China's economic development include the optimization of the supply-side structure and the great improvement of efficiency; The demand-side structure has been upgraded, and people's livelihood has been greatly compensated; scientific and technological innovation catch-up; Emerging industries are making great efforts; the great rise of urban agglomerations, etc.

In terms of structure, the tertiary industry accounted for a significant increase in GDP, reflecting the optimization of the macro supply structure to the service industry. In terms of efficiency, labor productivity has increased significantly, energy consumption per unit of GDP has continued to decrease, and significant progress has been made in the modernization of the industrial chain. R&D spending has increased substantially; The number of international patent applications climbed to the first place in the world;

The number of top international journals**, highly cited** and hot spots** in the world has risen to the top in the world.

III. Second and Second; rapid expansion of high-tech enterprises and science and technology enterprises; Major breakthroughs have been made in basic research, cutting-edge science and technology, and engineering science and technology. The eight strategic emerging industries have grown rapidly, accounting for a significant increase in the proportion of industrial added value and GDP. The status of enterprises in strategic emerging industries has been continuously improved, and the proportion of listed companies, especially large listed companies, has increased significantly, and the number of seats in the world's top 500 has also increased significantly.

The scientific and technological achievements made by China in the past ten years.

Manned spaceflight: Exploring the vast universe, developing the aerospace industry, and building a space power are the aerospace dreams pursued by the Chinese nation unremittingly. The aerospace dream is an important part of the dream of a strong country, and it is the birthplace of China's aerospace industry.

1. The Jiuquan Satellite Launch Center, which has been responsible for launching the Shenzhou series of spacecraft for many times, undoubtedly occupies an important position in it.

"To the sky": Good news is frequently reported that while manned space flight continues to make history, China is also moving towards the moon, Mars, and the sun. "Chang'e" explores the moon, "Zhurong" explores fire, and "Xihe" is chasing the sun, and ancient Chinese mythology is gradually coming into reality.

On November 10, 2020, the "Struggler" all-sea deep-sea manned submersible successfully sat on the bottom of the Mariana Trench and dived to a depth of 10,909 meters, setting a new record for China's manned deep diving. Three days later, the "Struggler" once again achieved a 10,000-meter deep dive, and the joint operation with the "Canghai" achieved the first live broadcast of the 10,000-meter ocean bottom in human history.

1. Zhan Tianyou and the Beijing-Zhangjiakou Railway: The Beijing-Zhangjiakou Railway is the first railway trunk line designed and constructed by the Chinese themselves, and it was built when modern China's science and technology were very backward and foreigners sarcastically mocked that Chinese railway engineers had not yet been born.

2. Feng Ru developed an airplane: Feng Ru was China's first aircraft designer, manufacturer and aviator, and the flight altitude, speed and range of the aircraft developed by Feng Ru set a world record at that time.

3. Gong Zhenlin, a weapons manufacturer: After the outbreak of Gong Zhenlin's Opium War, he saw that the great mountains and rivers were trampled by the British invaders, so he worked hard to study science and technology, improve weapons, and consciously devoted himself to the anti-aggression war. He personally went to the battlefield in Yongdong to carefully observe the British steamers, and made "wheel ships" and "wheel warships" driven by manpower.

During Lin Zexu's "meritorious service" in Zhejiang, he was transferred to work in the artillery bureau and built a "cardinal's new gun mount", which enabled the cannon to rotate in all directions and shoot flexibly.

4. Li Shanlan and "Fang Yuan Explains the Quiet": Fang Yuan Explains the Quiet is a mathematical work of the Qing Dynasty. It is about the study of power series formulas.

Li Shanlan created a kind of "sharp pyramid technique" and used it for the power series of logarithmic functions; Solve a variety of math problems by finding the sum of the spikes. Although he had not yet been exposed to calculus when he created the "sharp cone", he had actually come up with formulas for definite integrals. The Englishman Wei Liali believes that in the book written by Li Shanlan, "the reason is very close to the differential".

Li Shanlan's achievement shows that even if there is no calculus introduced from the West, Chinese mathematics will use its own special way to achieve calculus in a unique way of thinking, and basically complete the transformation from elementary mathematics to advanced mathematics.