Application of Gas Turbine

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Introduction:
Gas turbine is an internal combustion power machine that uses continuous flowing gas as a working substance to drive an impeller to rotate at high speed and convert the energy of fuel into useful work. It is a rotating impeller heat engine.

In the main process of air and fuel gas, only the gas turbine cycle composed of the three major components of the compressor, the combustion chamber and the gas turbine is known as the simple cycle. Most gas turbines use a simple cycle scheme.

The compressor draws air from the external atmospheric environment and compresses it step by step through the axial compressor to increase the pressure, and the air temperature is also increased accordingly; the compressed air is sent to the combustion chamber and mixed with the injected fuel to generate high temperature and pressure Gas; and then enter the turbine to expand the work, push the turbine to drive the compressor and the external load rotor to rotate together at high speed, and realize the partial conversion of the chemical energy of the gas or liquid fuel into mechanical work and output electrical work. The exhaust gas discharged from the turbine is discharged to the atmosphere to release heat naturally. In this way, the gas turbine converts the chemical energy of the fuel into heat energy, and part of the heat energy into mechanical energy. Generally, in gas turbines, the compressor is driven by the expansion of the gas turbine, 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 about 1/3 of the mechanical work is used to drive the generator. When the gas turbine starts, external power is needed first, usually the starter drives the compressor. Until the mechanical work of the gas turbine is greater than the mechanical work consumed by the compressor, the outside starter trips and the gas turbine can work independently.

Working principle:
The working process of the gas turbine is that the compressor (ie, 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, which then flows into the gas turbine The mid-expansion work pushes the turbine impeller to rotate with the compressor impeller; the working power of the heated high-temperature gas is significantly improved, so the gas turbine still has residual power as the output mechanical work of the gas turbine while driving the compressor. When the gas turbine is started from a standstill, it needs to be rotated with the starter, and the starter will not be disengaged until it can be accelerated to run independently.

The working process of the gas turbine is the simplest, called simple cycle; in addition, there are recuperation cycle and complex cycle. The working fluid of the gas turbine comes from the atmosphere, and is finally discharged to the atmosphere, which is an open cycle; in addition, there is a closed cycle in which the working fluid is used in a closed cycle. The combination of a gas turbine and other heat engines is called a compound cycle device.

The initial gas temperature and the compression ratio of the compressor are the two main factors that affect the efficiency of the gas turbine. Increasing the initial gas temperature and correspondingly increasing the compression ratio can significantly increase the efficiency of the gas turbine. At the end of the 1970s, the compression ratio reached a maximum of 31; the initial gas temperature of industrial and marine gas turbines was up to about 1200 ° C, and the aviation gas turbines exceeded 1350 ° C.

Advantages and disadvantages:
Advantage
Directly output rotary motion, do not convert linear reciprocating motion into rotary motion. It is better for gas turbines, so jet engines and ships are very suitable, but generators or cars used by ordinary people are not optimal.

There is no need to warm up the machine and there are not so many cold start problems, and there is no need to add antifreeze or the like in cold weather areas.

Supports multiple fuels: gasoline, diesel, kerosene, peanut oil, almost any flammable liquid or even mixed liquids.

Disadvantage
It is suitable for high-speed and stable operation scenarios. The efficiency at idle or acceleration is relatively much lower, and the fuel consumption at idle is extremely high. This can be regarded as the most unsuitable cause of family cars.

The temperature inside the engine is constantly high during operation, and the high temperature resistance and durability of the materials are expensive, resulting in high prices.

There is a lot of noise, and there is a unique sharp noise. Even if the decibel reduction is still unbearable to many people.

The instantaneous response is not good, which has an impact on the use of cars in urban environments.

NOx nitrogen oxide emissions are exponentially correlated with temperature, so high-temperature turbines have extremely high emissions, which can be regarded as the most fatal flaw under the trend of stricter emission standards.

Application of gas turbine:
1. Power plant
A factory that uses high-temperature gas as the working medium and converts the chemical energy in the working fuel into mechanical energy and electrical energy according to the constant pressure heating cycle. The liquid and gas fuel used in gas turbine power plants is converted into mechanical energy by the gas turbine, and then the generator is driven to generate electricity.

2. Seal
The advanced sealing technology of gas turbines is a branch field that has attracted great attention abroad in the past more than ten years. The benefits of advanced sealing technology have actually improved the performance of ground engines, reduced fuel consumption, and reduced operating and maintenance costs.

3. Warship aircraft
The ship’s power plant mainly includes: steam power plant, diesel engine power plant, nuclear power plant, gas power plant and combined power plant. The first two devices developed relatively early, and are widely used in various types of ships. The latter three are new power devices that have developed rapidly in the past decade. The ship’s gas turbine power plant refers to the full-fired power plant with the gas turbine as the main engine. It has been extremely widely used since the late 1950s, especially since the mid-1960s. The total number of power is increasing, and the range of ship loading is expanding. It has developed from speedboats to frigates, guided missile destroyers, cruisers, and helicopter aircraft carriers.

4. The development of aviation power industry drags down the marine gas turbine

Gas turbine impeller repair:
Considering the harsh conditions of the gas turbine and the expensive cost of replacing hot gas path components, repairing and refurbishing these components is the most economical option for gas turbine end users. Under the current electrical energy production market conditions, retrofitting gas turbine hot gas channel components is considered a technically complex but reliable process.
Brazed repair of worn impellers under vacuum is a new and effective and reliable process in refurbishment, which has gradually occupied the market position of major impeller refurbishments.

Edited by: Ryan Wu;
Copyright: SIMUWU Vacuum Furnace

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