10 paragraphs describing the summer can be three or four sentences per person, and if you have the a

Summer is at its most beautiful and coolest at night. Every year as soon as summer comes, I look forward to getting to night as soon as possible, because the days are indescribably hot. But the summer has the longest day, and I have been looking forward to it for a long time before the night comes.

How beautiful summer is! Mountains, rivers, flowers and trees are full of vitality. I love summer because it blooms with all kinds of small flowers, including moon and red.

Plantain ......They come in a variety of forms. The willow tree also evokes a strong vitality, in the breeze, the branches of the willow tree are as beautiful as the long hair of a girl, and the poplar tree is even more luxuriant, holding up a natural umbrella for us in the hot summer.

Summers are hot. The red sun was like a big ball of fire. Everyone wore their favorite tank tops and shorts. Many adults were chatting and enjoying the coolness, and the children on the side were eating with popsicles.

Summer is warm and brings me endless goodness.

Summer is hot and leisurely, suitable for making a cup of tea in a quiet afternoon, sitting on a stone bench in the shade of a tree, and counting the flowers blooming and falling.

Summer is a more romantic season, we can travel outside in this season, the temperature is more suitable, and there are many outdoor activities.

Summer is green, sunny, scorching, and everything is thriving.

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 July, the sky was clear and the sun hung like a fireball, and the clouds seemed to have been burned by the sun and disappeared without a trace.

Spring is gone with the falling flowers, and the green leaves in summer are jumping in the warm breeze.

The early summer sun shines through the dense layers of foliage, and the ground is covered with sparkling spots the size of copper coins.

The wind blows with a slight warmth, and from time to time it brings the cuckoo call, which tells us: "Spring has returned." ”

Grass, reeds, and red, white, and purple wildflowers were basked by the fiery sun that hung high in the sky, and the air was filled with a sweet and intoxicating scent.

Baked by the sun, sweat like tears.

In the summer, the whole city is like a burnt brick cellar, leaving people breathless. Knowing the heat, he kept chirping: "Know, know!" "The dog was so hot that he lay down in the shade of the tree, and spat out his bright red tongue, and gasped for breath; The chicken was so hot that it drooped its head and walked weakly.

Summer is leisurely and comfortable, we can play outside freely, when thirsty you can eat a cold ice cream, take a few bites, your heart immediately feels cold, or take out a piece of watermelon from the refrigerator and eat it to your heart's content, you can taste the taste of summer

In summer, the whole city is like a burnt brick hole that makes people breathless, and the ** hot non-stop chirping knows. The dog was so hot that he lay in the shade of the tree, spitting out his bright red tongue, and kept panting heavily, and the chicken was so hot that he was deaf and walked weakly with his head pulled.

The following is a passage describing summer:

1. The moonlight is like flowing water, quietly pouring in the small river, intertwining with the river water, forming a moving picture. I walked under the vast moon, beside me was a babbling and clear river, the pure water of which was like a mirror, reflecting the swaying shadows of the trees and my body.

2. I turned the road and returned, reminiscing about the bright moonlight, the pretty trees, the clear lake, and the cicadas chirping at that time, ah, it was an incomparably beautiful picture. I felt like I was in a fairyland, swimming in the paintings.

3. The beautiful summer is hot, and the old grandfathers all go to the trees to enjoy the shade, and some are playing chess. The old grandmother was chatting while fanning her under the tree of the Xinna shed, and the children liked to play and frolic in the water.

4. Summer, cloudy, unpredictable, and capricious. In the summer, the sun is shining and the golden sun shines on the beach near my house. The waters of the beach are not as smooth as a mirror, but sparkling and intriguing.

5. The beautiful scenery of spring is gradually gone, ushering in the vigorous, colorful and brilliant of summer. How beautiful this summer is, inheriting the vitality of spring, containing the maturity of autumn, and the colorful shaking of the earth stirring the spirit of summer.

6. Summer is a hot season, the fiery sun shines on us, the light and heat seem to pour out without money, and people are like being soaked in boiling water. The sun is like a big fireball hanging in the sky, it's really dazzling.

7. In summer, like a teenager humming a little song, he sprinkled every brilliant color on the earth like a prank. The fields changed to the faint colors of spring, and everywhere they were painted with colorful paint, and large swaths of color came into view.

8. A cool breeze with the fragrance of the earth blows, looking from afar, it is like a turbulent wave in the green sea, and the wheat seedlings are as green as a huge emerald placed in the field.

9. The little bird didn't know where to hide, and the grass and trees were all depressed, as if they were dying, only that knew it, and kept screaming on the branches, which was really breaking gongs and drums to cheer for the scorching sun.

10. On that day, the weather was so hot that it was crazy, as soon as the sun came out, the ground was already on fire, and some gray gas that seemed to be clouds but not clouds, like fog and not fog, floated low in the air, making people feel breathless.