A compressor, combustion chamber, and turbine are the basic components of an open cycle gas turbine plant. The compressor compresses the air, fuel is added to the combustion chamber, and the hot gases are expanded in the turbine. Two pressures must be considered, which are frequently expressed as a pressure ratio. The constant pressure lines on the T-S and P-V diagrams represent these pressures. Because the compressor and turbine share a common shaft, some of the work generated by the turbine is lost in the process of running the compressor.
Gas turbines were developed as technology advanced in fields such as internal combustion engines and steam turbines. Gas turbines were developed in the 1940s as a result of operations in both of these fields. Researchers developed various models that used steam or hot gas to create motion between 1500 and 1870. This article provides a thorough understanding of a specific type of gas turbine, the open cycle gas turbine, as well as its operating principles, benefits, and applications.
The Fundamentals of an Open Cycle Gas Turbine
Open cycle gas turbines are liquid-fueled combustion turbines that drive a rotor generator to generate electricity. At nearly 5500 degrees, the remaining heat will be exhausted to the atmosphere. Generators and turbines are housed in noise-reduction enclosures measuring nearly 75m by 75m per unit. The exhaust stack stands nearly 30 meters tall, while the intake structure stands 20 meters tall. Gas and steam turbine control systems can improve security and secure the turbines. IS200VPROH1B, IS200VPWRH1A are some examples of GE turbine control system components.
The Operation of an Open Cycle Gas Turbine
A compressor, a power turbine unit, and a combustor are the three components of an open cycle gas turbine. An open cycle gas turbine draws in fresh atmospheric air and compresses it using centrifugal or axial flow compressors. The compressor compresses atmospheric air through a series of compressor stages. When compressed air is injected into the combustion chamber, it is mixed with fuel. The turbine is powered by high-pressure hot gases. When the mixture is ignited, velocity gas is produced.
As the velocity gas passes through the turbine blades, it turns the shaft, which is connected to the generator’s rotor section. The energy generated by turning the turbine shaft can be used to power a variety of industrial devices as well as generate electricity.
Turbine emissions are released into the atmosphere. The system is classified as an open cycle because the exhaust gases are not recirculated but instead released into the atmosphere. Some of the turbine’s power is used to drive the compressor and other equipment, while the rest is used to generate electricity. The compressor receives fresh air, and the turbine’s gases are exhausted into the atmosphere, ensuring that the working medium is constantly replaced. This is how an open cycle gas turbine plant operates.
The combustion products in an open cycle gas turbine come into direct contact with the turbine blades. It is recommended to use fuels whose combustion products do not cause corrosion or high-temperature ash depositing, and whose residual solids are small enough not to cause erosion. Natural gas, refinery gas, blast furnace gas, and distillate oil are all suitable fuels for gas turbines. Contaminants may be present in residual fuel oils.
Advantages of Open Cycle Gas Turbine
The main benefits of open-cycle gas turbines are as follows:
- Warm-up time: Once the starting motor has accelerated the turbine to its rated speed and the fuel has been ignited, the gas turbine can be accelerated from a cold start to full load without requiring any warm-up time.
- Because of their quick start times and ability to take up load quickly; open-cycle plants are preferred as peak load plants.
- Low weight and size: The weight generated per kW is low.
Closed-cycle plants require more space than open-cycle plants.
- Fuels: Any type of hydrocarbon fuel, from heavy diesel oils to high-octane gasoline, can be used in the combustion chamber.
- Component and auxiliary refinements are commonly used in open cycle gas turbine plants to improve thermal efficiency. Depending on the load factors and other operating conditions, they can also provide the most cost-effective overall cost.
- There is no need for a cooling medium: Except for those equipped with intercoolers, open-cycle gas turbines do not require cooling water. As a result, the plant becomes self-contained and no longer requires a cooling medium.
Disadvantages of Open Cycle Gas Turbine
The following are the drawbacks of an open cycle gas turbine:
- Low part-load efficiency: Because a significant portion of the turbine’s power is used to drive the compressor, the efficiency decreases rapidly at part load.
- Sensitivities: The efficiency of the system’s components, particularly the compressor, is critical. It is affected by changes in atmospheric temperature, pressure, and humidity.
- Heat loss from exhaust gas: Because the open cycle plant has a higher air rate than the closed-cycle plant, heat loss in the exhaust gases increases, necessitating the use of large diameter ducts.
- Erosion: Keeping dust out of the compressor is critical for avoiding erosion and deposition on the compressor blades and passages. As a result, their reputation suffers. The carbon and ash deposited on the turbine blades are undesirable because they reduce the efficiency of the open cycle gas turbine plant.
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