China develops 4.5 times the speed of sound engine: the United States

According to the Guangming Daily’s public report, China has successfully developed a new squeezing engine with 4.5 times the speed of sound, while the previous generation of products was around 3 times the speed of sound. Around this news, you can dig into three very interesting questions: First, what is the significance of ramming the engine? Second, what are the difficulties with ramjet engines? Third, where exactly will the engine of the news be used?

The first problem is that the ramjet engine is the most economical power for all types of aircraft (including airplanes, missiles, etc.) within the atmosphere and for high-speed missions. The suction engines used in traditional supersonic aircrafts, such as turbojet engines and turbojet fan engines, have higher resistance at high speeds and smaller and smaller thrusts, making it difficult to achieve 3 times the speed of sound. .

Instead of using a rocket engine that absorbs air from the outside world, its operating state is not affected by the speed of flight, but due to the need to bring its own oxidants, rocket-powered vehicles with the same tonnage and size restrictions should be used with less than half of the fuel; in other words, aircraft. The range of the missile and the range of the missile are directly to be folded.

Modern rocket engines mostly use high-energy solid fuels (in fact, high-energy explosives that strictly control the combustion speed). The larger the size of the pellets, the higher the requirements for material and process control, and the lower the product qualification rate, and the lower the projected cost will be as the range increases. The skyrocketing proportion.

When the ramjet is working at high speed, the thrust has low resistance and its structure is light and simple. In the case of hypersonic missiles only, the ramjet engine can be used to double the range of products with the same tonnage size; or the volume can be made even smaller with the same range, and the weapon system can carry more missiles at one time. Quantity.

The main difficulties in the practical application of ramjet engines are, first of all, that they can only be started when sufficient intake pressure is obtained at high speeds. Different aircraft have different ways of dealing with the speed of starting. For example, the SR71 Blackbird, whose J58 engine operates in vortex spray mode at low speeds, converts to stamping mode after acceleration is completed. For missiles (especially non-launched), solid rocket boosters are usually used for assisted acceleration.

The next difficulty lies in the fact that structural components have strong requirements for high temperature and high strength, and the last and most difficult problem is to ensure that the fuel mixes with the air evenly and reliably ignites and sustains stable combustion—especially for maneuvers of missiles. The inlet angle, etc., is always in the process of change. The higher the speed, the greater the difficulty in this area. For example, after the 3 times speed of sound is increased to 4.5 times the speed of sound, one of the difficulties encountered is that the temperature of the air flow in the intake port will increase sharply, which will have a huge negative impact on the combustion process.

After high-temperature air and fuel are mixed and burned, the generated carbon dioxide and water vapor will begin to dissociate further; a large amount of carbon monoxide, hydroxyl, atomic oxygen and hydrogen will be decomposed, and at 5 times the speed of sound, the water generated by combustion will be 60%. It is dissociated - and the energy that dissociates carbon dioxide and water comes from the combustion release of the fuel itself. This phenomenon not only leads to a high degree of instability in the combustion process itself, but also leads to a sharp drop in engine thrust. It is one of the key factors that hinder the ramjet from hypersonic flight and is called “high-ultrasonic obstacle”.

Finally, from the application perspective, due to the limitations of the engine itself, thermal barriers and high pressure, it is currently necessary to manufacture large-tonnage, large-size 4.5-speed sonic-class aircraft such as manned aircraft or large and medium-sized drones. The only practical project that can be used is the development of long-range high-speed missiles.

Even more concrete, both ultra-long-range air-to-air missiles (used for large-scale air targets such as early warning aircraft) and long-range anti-ship/missile missiles are within the range of possibility; perhaps after a few years, we can see this. Public appearance of products. (He Zhijian)

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