A gas turbine is a kind of machine that uses gas and air as power, and is much more used in large-scale industries. Many people have never heard of this term, let alone what a gas turbine is. The following small series will introduce the working process, classification, working principle, characteristics and key technologies of gas turbines.
Brief Introduction of Gas Turbine:
Gas turbine is a rotating power machine that uses a continuous flow of gas as the working fluid and converts heat energy into mechanical work. In the main process of air and gas, only the compressor, combustion chamber and turbine (Turbine) three components of the gas turbine cycle, commonly known as the simple cycle. Most gas turbines use a simple cycle scheme. Because its structure is the simplest, and it can best reflect a series of advantages such as small size, light weight, fast start-up, and little or no cooling water unique to gas turbines.
Usually in a gas turbine, the compressor is driven by the work of gas turbine expansion, which is the load of the turbine. In a simple cycle, about 1/2 to 2/3 of the mechanical work emitted by the turbine is used to drive the compressor, and the remaining 1/3 or so is used to drive the generator. When the gas turbine starts, external power is first required, generally the starter drives the compressor, until the mechanical power emitted by the gas turbine is greater than the mechanical power consumed by the compressor, the external starter trips, and the gas turbine can work independently.
The Working Process of A Gas Turbine:
The working process of a gas turbine is that the compressor (that is, the compressor) continuously draws air from the atmosphere and compresses it; The compressed air enters the combustion chamber, mixes with the injected fuel and burns to become high-temperature gas, and then flows into the gas turbine to expand and do work, pushing the turbine impeller to rotate with the compressor impeller; The functional power of the heated high-temperature gas is significantly improved, so the gas turbine has residual work as the output mechanical work of the gas turbine while driving the compressor.
The initial temperature of the gas and the compression ratio of the compressor are the two main factors affecting the efficiency of the gas turbine. Increasing the initial gas temperature and increasing the compression ratio accordingly can significantly improve the efficiency of the gas turbine. At the end of the 70s, the compression ratio reached a maximum of 31; The initial gas temperature of industrial and marine gas turbines is up to about 1200 °C, and the aviation gas turbine is more than 1350 °C.
The Kinds of Gas Turbine:
1. Design characteristics of heavy-duty gas turbines: the parts are relatively thick, and the main purpose of the design is not to reduce weight, but to achieve the purpose of long-term safe work in the case of the application of materials that are not very good. The mass per unit power is 2-5 kg/kW.
2. Design characteristics of light gas turbine: made of better materials, compact structure, light weight, and the mass per unit power is less than 2 kg/kW.
Structural features: (1) The axial assembly method is adopted, that is, the entire stator is not all horizontally divided, and only the local stator such as the compressor cylinder is divided into two halves for disassembly and assembly. (2) The rotor is supported by rolling bearings.
3. Micro gas turbine design features: the gas turbine and generator are designed as a whole, with small volume and light weight.
Structural features: (1) The use of run-off turbomachinery. (2) Some units also use air bearings, which do not require lubricating oil.
4. Large and medium-sized gas turbines: gas turbines with power greater than 20MW.
5. Small gas turbine: power range is 0.3MW-20MW.
6. Micro gas turbine: gas turbine with power range of 30-300KW or less.
