Recently, China's first 80-ton liquid oxygen methane engine-"Tianque" (TQ-12) was successfully tested in 20 seconds. This is following the US SpaceX raptor engine and the blue-origin BE-4 engine. Enterprise Blue Arrow Aerospace completed the world's third large-thrust liquid oxygen methane rocket engine test drive. To allow objects of tonnage or even hundreds of tons to get rid of the gravity of the earth, the rocket engine must bring its own huge explosive force, and it must not be affected by the explosion. Why is the success of the liquid oxygen methane engine test run significant? What are its characteristics compared with mainstream fuels currently used by rockets? Powerful strength, great thrust meets constellation layout "The establishment of a low-orbit satellite system for commercial enterprises is entering the stage of mass launch. It must require a medium-sized rocket to achieve a faster and more economical launch guarantee." Zhang Changwu, CEO of Blue Arrow Aerospace, believes that market demand is forcing more than one arrow "Become the norm. Liquid fuel has greater thrust potential than solid fuel. Therefore, compared with solid fuel rockets, liquid fuel rockets can hold more satellites. The more practical problem is that the actual weight of satellites is often heavier than expected, which also requires the rocket to have a large range of carrying capacity. The liquid oxygen methane rocket engine uses methane as the propellant and liquid oxygen as the combustion aid. The two atomize at a certain ratio and enter the combustion chamber. After full combustion, they release a huge driving force and push the rocket into the air. The specific impulse is higher than solid fuel rocket engines. Specific impulse is an important physical parameter used to measure the efficiency of rocket or aircraft engines. The higher the specific impulse, the greater the momentum generated by the same quality fuel. In addition, the reason why the liquid oxygen methane rocket engine is the protagonist of "One Arrow, Many Stars" is also due to its ability to complete multiple launch tasks. Once the solid fuel engine is started, it is very difficult to stop the combustion midway. Generally, it will burn until all the propellant is burned out, and the liquid fuel rocket can stop the flow of propellant by closing the valve, thereby shutting down the engine. Zhang Changwu said: "Multi-satellite orbits in different orbits need to have multiple start-up functions in orbit. The satellites are placed in different orbits. Liquid fuel rockets have such capabilities. Solid fuel engines cannot be started multiple times, only applicable. Provide short-term large thrust, for example, for boosting during the take-off phase. " Zhang Changwu explained that the "Suzaku 2" rocket equipped with a liquid oxygen methane engine will have a low orbit carrying capacity of 4 to 5 tons, which can meet the needs of mass launch. If the weight of the satellite is between 300 and 500 kg, a 10 to 20 star launch will be achieved, which will greatly meet the requirements of domestic constellation construction. Its strength continues to grow in subsequent development. "The current fuel cycle method can still be further optimized. In addition, if the engine itself is replaced by new materials and new processes, its own weight can be reduced by at least 30%, which will also greatly increase the carrying capacity of the rocket." . Get rid of carbon deposits and lay a reusable foundation In addition to the liquid oxygen methane engine, the liquid rocket engine family also has liquid oxygen liquid hydrogen engines and liquid oxygen kerosene engines. If the liquid oxygen liquid hydrogen engine is "Bai Fumei" and the liquid oxygen kerosene engine is "black iron cow", then the liquid oxygen methane engine can be called "Jing Shiman". In a liquid oxygen kerosene engine, liquid oxygen is the combustion aid and kerosene is the thrust agent. The carbon chain of kerosene is longer, and the proportion of carbon element is much higher than that of methane, so its combustion is very easy to deposit carbon and coke. "It's actually quite easy to understand that burning kerosene used to emit black smoke, but burning natural gas is a pure blue flame." The relevant experts explained. Due to the advantages of "no trace" after combustion, the liquid oxygen methane engine naturally becomes a potential stock for reusable engines. "We conducted 4 test runs in 6 days, which is relatively high for traditional fuel engines." Zu Cheng said, and this is the same engine, no need to disassemble and re-preparation. In addition, the technical threshold of the liquid oxygen methane engine is also far lower than the liquid oxygen liquid hydrogen engine. Compared with the liquid oxygen liquid hydrogen engine with the highest specific impulse, the design of the liquid oxygen methane engine is less difficult. Yuan Yu, the head of the thrust room of the Blue Arrow Aerospace Power Research and Development Department, attributed it to methane being "tamed", and the liquid hydrogen density is too low. To compress it, a pressure pump with a very high speed is required to fully mix it. "There are two pumps in the hydrogen-oxygen engine, one hydrogen pump and one oxygen pump. The gas from the gas engine has 80% of the power to be supplied to the hydrogen pump." Yuan Yu said. In addition, the liquid oxygen liquid hydrogen engine stores the fuel tank The process difficulty is also large, liquid hydrogen -253 ℃, liquid oxygen -182 ℃, the temperature difference between the two is large to be insulated, and the temperature of liquid oxygen and methane are similar, the process difficulty is greatly reduced. In terms of comprehensive comparison, whether it is from the cost or from the target mission, the liquid oxygen methane engine will greatly reduce the rocket launch cost, so that the dream of ordinary people touching space is getting closer and closer.
Guide Ring is a mechanical seal, also known as a guide ring. It is usually made of metal or plastic and used to support and position pistons or rods. Guide Ring has excellent wear resistance and corrosion resistance, which can effectively reduce leakage and friction, thereby extending equipment life. Guide Ring is widely used in the hydraulic, pneumatic, mechanical, and automotive industries as an important mechanical seal.
The classification of Guide Ring can be divided by material, structure, and purpose. According to material classification, Guide Rings are mainly divided into metal Guide Rings and plastic Guide Rings. Metal Guide Rings are usually made of metals such as copper, iron, and stainless steel, which have high strength, wear resistance, and high-temperature resistance; The plastic Guide Ring is usually made of polytetrafluoroethylene (PTFE), nylon, polyimide and other materials, with good corrosion resistance and low friction coefficient.
According to structural classification, Guide Rings are mainly divided into unidirectional Guide Rings and bidirectional Guide Rings. A unidirectional guide ring can only withstand pressure in one direction and is typically used in hydraulic and pneumatic systems; The bidirectional guide ring can withstand bidirectional pressure and is typically used in the mechanical and automotive industries.
According to usage classification, Guide Rings are mainly divided into piston Guide Rings and rod Guide Rings. The piston guide ring is usually used to support and position the piston, preventing friction and leakage between the piston and the cylinder liner; The rod guide ring is used to support and position the rod, preventing friction and leakage between the rod and the seal.
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