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Gas turbine originated in the 19th century. It is the product of the second industrial revolution. Now it is also widely used in transportation, electric power, aerospace and other fields. But in fact, gas turbine is still the most difficult mechanical equipment to manufacture.
01 how difficult is it to manufacture gas turbines?
The gas turbine is composed of compressor, combustor and turbine. The principle is that the compressor sucks air from the outside and compresses and pressurizes it step by step through the axial compressor; The compressed air enters the combustion chamber and is injected into the fuel for combustion to generate high-temperature and high-pressure gas, which is discharged through the gas discharge valve. The rotating blade drives the turbine to rotate, so as to make the compressor rotate at high speed.
In the gas turbine, the compressor is driven by the expansion of the gas turbine. About half of the mechanical work generated by the turbine drives the compressor, and the rest is power output; Therefore, when starting the gas turbine, the compressor needs to be driven by the motor first. Until the mechanical work of the gas turbine is greater than the mechanical work consumed by the compressor, the gas turbine can work independently.
The principle does not seem complicated, but in order to maintain a high power during the continuous operation of the gas turbine, the temperature should be maintained at about 1000 degrees, and it needs to be maintained at this temperature for tens of thousands of hours for a long time without damage, which has extremely high requirements for the materials of the gas turbine.
In addition to the materials, it is also necessary to consider how to fully burn the compression ratio of the compressor and the fuel in the combustion chamber to produce the maximum pressure. At the same time, the high-temperature and high-pressure gas is blown to the impeller. The impeller should be able to rotate stably for a long time under high temperature and high pressure, which is the same as putting ice in a fire and requiring that the ice cannot melt away.
In this case, it is necessary to reduce the mechanical energy of the compressor driven by the rotation of the impeller and increase the mechanical energy generated by the turbine equipment. This requires continuous improvement and Optimization in cooling mode, flow channel, blade profile, material, coating, control, etc. in order to improve the efficiency, but these technologies have long been used by GE, Siemens Heavy gas turbine products dominated by Mitsubishi monopolize and refuse technology transfer. China can only conduct self-research, and there is still a large gap between the technical level and the top giants.
02 why focus on gas turbines?
In fact, gas turbine is the product of the second industrial revolution. Now that electric motor is very common, many people may have questions. Why do we spend so much energy on studying an outdated thing? As a reliable science writer, I can tell you that gas turbine is not only not outdated, but also very important.
Gas turbines do not have high requirements for fuel, and any fuel can be used. However, in order to improve efficiency and protect the environment, they mainly burn natural gas. With the implementation of China's green energy development plan in the 14th five year plan, low-carbon economy and carbon neutralization have become the top priority. Low pollution energy has been paid attention to, and the R & D work of its related industries has already begun, The 13th five year plan for power development has defined the construction objectives of natural gas power generation projects. By 2020, the installed capacity of gas power generation will account for more than 5% and the overall scale will reach 110gw (GW).
In the 13th five year plan for energy development, hydrogen energy and fuel cell are listed as key technologies that need to be tackled intensively. Developed countries such as the United States, Japan and Europe have successively included hydrogen energy development in the national energy development plan. At present, the industry is developing rapidly. Replacing natural gas with clean hydrogen fuel is also the trend of gas turbine power generation in the future.
However, the disadvantages of hydrogen are also obvious. Firstly, it is highly corrosive, high calorific value and fast combustion, so it is difficult to control the fuel supply rate. Therefore, it is difficult to use alone at present. Most of them are mixed with natural gas and added to gas turbines, or through industrial processing, hydrogen and carbon dioxide form clean energy such as methane and methanol.
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