Gas Turbine

what is Gas Turbine?

A gas turbine, also known as a combustion turbine, is a type of internal combustion engine that converts the energy from fuel into mechanical energy through a combustion process. It’s commonly used in various applications, including power generation, aviation, and industrial processes.

The basic principle of a gas-turbine involves compressing air and then mixing it with fuel to create a high-temperature, high-pressure gas mixture. This mixture is then ignited, causing it to expand rapidly and exhaust through a nozzle, generating a high-speed jet of gas. The force of this exhaust jet creates a rotational motion in the turbine’s blades, which is connected to a shaft. The rotational motion of the turbine shaft can be used to drive various types of machinery, such as electrical generators, jet engines, or mechanical equipment in industrial processes.

It is known for their efficiency, high power-to-weight ratio, and the ability to generate power quickly, making them suitable for applications where rapid power generation is crucial. They are commonly used in power plants to produce electricity, in aircraft engines to provide thrust for flight, and in various industrial processes to drive machinery.

gas turbine cycle

The gas turbine cycle, known as the Brayton cycle, encompasses four main stages:

1. Compression: Ambient air is drawn in and compressed by the compressor, increasing pressure and temperature.
2. Combustion: The compressed air enters the combustion chamber, where it mixes with fuel, ignites, and releases energy in the form of hot gases.
3. Expansion: These hot gases flow over turbine blades, expanding and converting thermal energy into mechanical work.
4. Exhaust: The gases exit the turbine, having lost energy, and are released into the environment.

Though real-world gas turbines may have losses, the underlying Brayton cycle defines the core process of transforming chemical energy into mechanical power, used for applications like power generation and propulsion.

components of gas turbine

A gas turbine is a complex machine composed of several interconnected components that work harmoniously to convert the energy stored in fuel into mechanical power. These components collectively enable the efficient transformation of chemical energy into kinetic energy and can be categorized as follows:

1. Air Intake: Serving as the gateway to the gas turbine, the air intake system draws in ambient air and directs it towards the compressor. This initial stage plays a critical role in ensuring a steady and controlled flow of air.
2. Compressor: The compressor section consists of alternating rows of rotating blades attached to the compressor rotor and stationary blades on the compressor stator. As air passes through these stages, its pressure and temperature rise significantly due to the mechanical work applied by the rotating blades. This compressed air is then directed into the combustion chamber.
3. Combustion Chamber: The heart of the gas turbine, the combustion chamber, is where the compressed air is mixed with fuel and subsequently ignited. This process creates a controlled explosion, leading to the release of high-energy, high-velocity hot gases.
4. Turbine: Positioned downstream from the combustion chamber, the turbine section is composed of turbine rotor blades and stationary turbine stator blades arranged in stages. The scorching gases from the combustion chamber flow over these blades, causing them to spin. The resulting rotational energy is then transferred to the compressor and other connected systems.
5. Exhaust Outlet: After passing through the turbine stages, the hot gases exit the system through the exhaust outlet. In some applications, the residual energy in these gases can be exploited for secondary processes or waste heat recovery.
6. Shaft: The turbine shaft serves as the mechanical link connecting the compressor and turbine sections. The kinetic energy produced by the turbine blades is transmitted through this shaft, driving the rotation of the compressor and any attached external components.
7. Bearings: Bearings are strategically positioned to provide support and reduce friction between the rotating and stationary parts of the gas turbine. These components are pivotal for maintaining smooth and reliable operation.
8. Auxiliary Systems: The seamless operation of a gas turbine relies on auxiliary systems that manage various functions:

• Fuel System: Precisely delivers the appropriate amount of fuel to the combustion chamber, ensuring efficient combustion.
• Ignition System: Initiates the combustion process by producing an initial spark or heat source.
• Cooling System: Crucial for preventing overheating, the cooling system safeguards sensitive components against the intense temperatures generated.
• Control System: Orchestrates the entire gas turbine process, overseeing performance, efficiency, and safety.

9. Accessory Gearbox: In specific gas turbine designs, an accessory gearbox might be incorporated to power auxiliary mechanisms like pumps, generators, and fans, enhancing overall functionality.

The intricate design and interactions among these components contribute to the gas turbine’s diverse applications across industries such as power generation, aviation, marine propulsion, and more. Continual advancements in materials, coatings, and cooling methods further optimize the efficiency, longevity, and performance of gas turbines in various settings.

gas turbine working

The operation of a gas turbine revolves around a well-defined sequence of thermodynamic processes that convert the chemical energy stored in fuel into valuable mechanical energy. The journey begins as ambient air is drawn into the system through an air intake.

This air undergoes a remarkable transformation within the compressor section. Here, a meticulously orchestrated arrangement of rotating and stationary blades compresses the air, intensifying its pressure and temperature. The compressed air is then ushered into the combustion chamber, where it mingles with a carefully dosed fuel, such as natural gas or aviation fuel. Ignited by a spark or heat, this mixture ignites in a controlled explosion, generating an expanse of high-temperature, high-pressure gases.

These hot gases surge into the turbine section, where they find purpose in the rows of turbine blades. These blades, linked to a rotor, harness the energy of the gases as they expand and flow over them, setting the blades into motion.

This mechanical energy is seamlessly transmitted to the compressor blades through a central shaft, effectively powering the entire cycle. As the gases relinquish their energy, they exit the system through an exhaust outlet.

The mechanical energy extracted from the turbine serves various functions. In power generation, it propels electrical generators, while in aviation, it fuels aircraft propulsion systems, generating the thrust essential for flight.

This perpetuating cycle, characterized by air intake, compression, combustion, expansion, and exhaust, embodies the gas turbine’s ability to adeptly convert fuel’s potential into kinetic energy, thus fueling industries, transportation, and power generation worldwide.

types of gas turbine

Gas turbines exhibit a diverse range of types and configurations, each meticulously tailored to specific applications and operational demands across various industries. Here’s an elaboration on the main types of gas turbines:

1. Aero-Derivative Gas Turbines: Originating from aircraft jet engines, aero-derivative gas turbines have been ingeniously adapted for multifaceted industrial and power generation purposes. Recognized for their enviable power-to-weight ratios, rapid start-up capabilities, and unmatched flexibility, these turbines are extensively employed in peaking power plants. Their rapid power generation capacity efficiently addresses high-demand periods.
2. Industrial Gas Turbines: Custom-designed for industrial applications, industrial gas turbines form the bedrock of numerous sectors, including power plants, petrochemical facilities, and manufacturing processes. These turbines are meticulously optimized for seamless and durable operation under continuous and demanding conditions.
3. Heavy-Duty Gas Turbines: Representing a league of their own, heavy-duty gas turbines stand as colossal powerhouses, predominantly used in utility-scale power generation. These turbines wield the prowess to generate substantial electricity, often finding their place within combined cycle power plants. Here, their waste heat harmonizes with a steam turbine for augmented power generation efficiency.
4. Micro Gas Turbines: Engineered as scaled-down renditions of gas turbines, micro gas turbines play an indispensable role in distributed power generation and other domains where spatial efficiency and portability are paramount. Deployed in residential, commercial, and small-scale industrial contexts, these turbines embody the essence of compact power.
5. Open-Cycle Gas Turbines: Open-cycle gas turbines adhere to a straightforward operational cycle. Air is compressed, mingled with fuel, and subsequently ignited in the combustion chamber. The ensuing hot gases then traverse the turbine, culminating in power generation. These turbines excel in scenarios where power output and efficiency take precedence over waste heat recovery.
6. Combined Cycle Gas Turbines: Residing at the zenith of efficiency, combined cycle power plants weave gas turbines into a harmonious synergy with steam turbines. Exhaust heat from the gas turbine is harnessed to generate steam, thus propelling a steam turbine for supplementary power generation. This configuration maximizes efficiency by leveraging both gas and steam turbines.
7. Cogeneration (CHP) Gas Turbines: Cogeneration or combined heat and power (CHP) gas turbines embody the epitome of efficiency. Emitting both electricity and useful heat in tandem, these turbines ingeniously utilize the waste heat from exhaust gases to fulfill heating requirements, making them a quintessential choice for energy-intensive applications.
8. Jet Engines: Jet engines, a specialized breed of gas turbines, exclusively serve the realm of aircraft propulsion. This category encompasses turbojet engines, turbofan engines (including high-bypass turbofans powering commercial airliners), and turboprop engines that grace regional aircraft and select military planes.
9. Marine Gas Turbines: Navigating the maritime domain, marine gas turbines underpin marine propulsion systems, encompassing naval vessels, commercial ships, and even luxury cruise liners. Distinguished by their high power density and swift acceleration, these turbines are the propulsion force behind vessels necessitating a fusion of speed and maneuverability.
10. Stationary Gas Turbines: Stationary gas turbines find their niche as unwavering installations catering to power generation, especially in remote locales or regions grappling with infrastructure limitations. Efficaciously fulfilling the energy needs of areas sans centralized power grids, these turbines empower communities with indispensable electricity.

The manifold types of gas turbines seamlessly weave efficiency, power magnitude, and adaptability into a tapestry that caters to specific industrial and operational contexts. This diversified array of gas turbines underscores their versatile role in propelling progress across diverse sectors.

application of gas turbine

Gas turbines find a wide range of applications due to their versatility, efficiency, and power-to-weight ratio. Here are some of the major applications of gas turbines:

1. Power Generation: It is commonly used in power plants to generate electricity. They can operate on natural gas, diesel, or other liquid and gaseous fuels. Gas turbine power plants can be quickly started and stopped, making them suitable for meeting fluctuating electricity demands. They are often used in peaking power plants and as backup power sources.
2. Aircraft Propulsion: Gas turbines power jet engines in commercial and military aircraft. They provide the high thrust-to-weight ratio necessary for aircraft to achieve takeoff and maintain flight. Modern jet engines are highly efficient and allow aircraft to travel at high speeds over long distances.
3. Marine Propulsion: It is used to propel naval ships, including warships and cruise liners. Their compact size, rapid acceleration, and high power output make them ideal for ships that require both speed and maneuverability.
4. Industrial Applications: It is utilized in various industrial processes such as driving compressors for natural gas pipelines, providing mechanical power for manufacturing facilities, and generating steam for industrial processes. They are also used in cogeneration or combined heat and power (CHP) systems, where the waste heat from the turbine is captured and used for heating or other industrial processes.
5. Oil and Gas Industry: It is used in the oil and gas sector to drive pumps, compressors, and other equipment for drilling, refining, and transporting oil and natural gas.
6. Power for Remote Locations: It can provide power to remote areas where establishing a conventional power grid might be difficult or expensive. They can run on a variety of fuels, including diesel, natural gas, and even biofuels.
7. Emergency Backup Power: It can serve as backup power sources for critical facilities like hospitals, data centers, and emergency response centers. They can quickly provide electricity in case of grid failures.
8. Cogeneration Plants: In cogeneration (CHP) plants, gas turbines not only generate electricity but also capture waste heat from the exhaust to produce steam for heating or industrial processes, increasing overall efficiency.
9. District Heating: It can be used to generate heat for district heating systems, providing centralized heating for residential and commercial areas.
10. Renewable Energy Integration: It can provide backup power to stabilize electricity grids when renewable energy sources like wind and solar fluctuate due to weather conditions.
11. LNG (Liquefied Natural Gas) Industry: It is used in liquefaction processes to convert natural gas into LNG for storage and transportation.
12. Chemical Industry: It play a role in various chemical processes, including producing hydrogen, ammonia, and other chemical compounds.

These applications highlight the versatility of gas turbines and their importance in various industries and sectors, contributing to energy generation, transportation, manufacturing, and more.

advantages of gas turbine

Gas turbines offer several advantages that make them attractive for various applications. Some of the key advantages of gas turbines include:

1. Efficiency: Gas turbines are known for their high efficiency, especially in combined cycle power plants where waste heat from the gas turbine is used to generate steam and produce additional electricity. This combined cycle configuration can lead to overall efficiencies above 50%, which is higher than many other types of power generation technologies.
2. Quick Start and Stop: It can start up and reach full load within minutes, making them ideal for meeting sudden changes in electricity demand. This flexibility is crucial for stabilizing the power grid and providing peaking power during high-demand periods.
3. Compact Design: It has a relatively small footprint compared to other power generation technologies with similar output. This compact design allows for installation in areas with limited space.
4. High Power-to-Weight Ratio: It has a high power output relative to their weight, which is important for applications where weight is a critical factor, such as aircraft propulsion and mobile power generation units.
5. Low Emissions: Modern gas turbines incorporate advanced combustion technologies that reduce emissions of pollutants like nitrogen oxides (NOx) and particulate matter. Additionally, when used in combined cycle plants, their efficiency can result in lower greenhouse gas emissions per unit of electricity generated compared to other fossil fuel power plants.
6. Fuel Flexibility: It can operate on a variety of fuels, including natural gas, diesel, kerosene, and even renewable fuels like biofuels. This flexibility allows for adaptation to changing fuel availability and prices.
7. Low Water Usage: It do not require significant amounts of water for cooling, unlike some other power generation technologies like steam turbines. This can be advantageous in water-scarce regions.
8. Low Maintenance Requirements: It has fewer moving parts compared to some other engines, leading to reduced maintenance requirements and downtime.
9. Reliability: It is known for their reliability and long operational lifetimes. Properly maintained gas turbines can operate for decades.
10. Cogeneration Potential: It can be integrated into combined heat and power (CHP) systems, where the waste heat is captured and used for heating, further increasing energy efficiency.
11. Decentralized Power Generation: It can be used for distributed and decentralized power generation, which can enhance grid stability and reduce transmission losses.
12. Rapid Response to Grid Demand: It can rapidly adjust their output to match changes in electricity demand, helping to maintain grid stability during fluctuations.
13. Remote Power Generation: It can provide power in remote locations where establishing a conventional power grid might be challenging.
14. Aircraft Propulsion: In aviation, gas turbines provide the high thrust-to-weight ratio necessary for aircraft to achieve takeoff and maintain flight.
15. Marine Propulsion: It offer high power output and rapid acceleration, making them suitable for powering naval and commercial ships.

These advantages highlight the importance of gas turbines in a variety of industries and applications, from power generation to transportation and industrial processes. However, it’s worth noting that each application has its specific requirements and considerations, so the suitability of gas turbines depends on factors such as fuel availability, operational conditions, and environmental regulations.

disadvantages of gas turbine

While gas turbines offer several advantages, they also come with certain disadvantages and challenges. Here are some of the key disadvantages of gas turbines:

1. Lower Efficiency at Partial Load: It tend to have lower efficiency at partial load or during periods of varying demand. This can be a drawback when they are used in applications that experience frequent load fluctuations, as their efficiency might decrease during off-peak demand.
2. High Fuel Consumption at Low Loads: It can be less fuel-efficient when operating at low loads, which could result in higher fuel consumption and increased operational costs.
3. High Initial Costs: The capital investment required for purchasing and installing gas turbines can be relatively high, especially for larger units and combined cycle configurations. This initial cost can sometimes be a barrier to adoption, particularly for smaller organizations or projects.
4. Emissions: While gas turbines generally emit fewer pollutants compared to some other combustion technologies, they still produce emissions, including nitrogen oxides (NOx) and carbon dioxide (CO2). The emissions can vary based on the type of fuel used and the combustion process.
5. Dependence on Fuel Supply: It require a consistent and reliable supply of fuel, which could be natural gas, diesel, or other fuels. Any disruption in the fuel supply could lead to operational challenges.
6. Heat Recovery Challenges: While combined cycle configurations can capture waste heat for enhanced efficiency, implementing effective heat recovery systems can be complex and costly.
7. Mechanical Complexity: It involve high-speed rotating machinery, which requires precision engineering and maintenance expertise. The mechanical complexity can lead to maintenance challenges and downtime if not properly managed.
8. Noise Generation: Gas turbines, especially in aviation and industrial applications, can generate significant noise during operation. Noise reduction measures may be necessary, particularly in environments where noise pollution is a concern.
9. Limited Start-Stop Cycles: Frequent start-stop cycles can increase wear and tear on gas turbine components, potentially leading to higher maintenance and reduced operational lifespan. This limitation can be problematic in applications that require frequent startups and shutdowns.
10. Environmental Impact: While gas turbines emit fewer pollutants compared to some alternatives, they still contribute to air pollution and greenhouse gas emissions, particularly if the fuel source is not clean.
11. Limited Efficiency Gain from Fuel Mixtures: While some other combustion technologies can adapt to a wider range of fuel mixtures, gas turbines might have limitations in this regard, affecting their ability to utilize certain alternative fuels efficiently.
12. Technical Expertise Required: Operating and maintaining gas turbines require specialized technical expertise. Skilled personnel are needed for proper installation, operation, and maintenance, which can increase operational costs.
13. Lack of Energy Storage: It do not have built-in energy storage capabilities. As a result, they might require additional systems (like batteries or energy storage facilities) to address fluctuations in electricity demand and supply.

It’s important to consider both the advantages and disadvantages of gas turbines when evaluating their suitability for a particular application. The choice of technology should be based on the specific operational requirements, cost considerations, environmental concerns, and available resources.

Gas turbine vs steam turbine

Certainly, here’s a comparison between gas turbines and steam turbines in a table format:

Keep in mind that the choice between gas turbines and steam turbines depends on various factors including the specific application, efficiency requirements, environmental concerns, available resources, and operational characteristics.

Reference : https://www.britannica.com/technology/gas-turbine-engine