Gas turbine along with it’s different parts, classification, working principles, advantages, disadvantages, etc. are captured in this article.
Let’s understand the basics of a gas turbine. There are various types of prime movers available nowadays. One of the simple power-producing ways is the gas turbine.
Some features of gas turbine make it even better and it’s used in power plants as well as in gas turbine engines.
We all know how the turbine is operated.
The gas turbine is defined as the combustion engine which produces electricity by expanding natural gas.
Now let’s see the parts used in the gas turbines and later open cycle and closed gas turbines in brief.
There are few main components,
In a simple gas turbine, the centrifugal compressor is used.
That’s how they are useful in turbocharged engines.
This one is another important part of the gas turbine. The whole combustion process takes place in the combustion chamber. Why is it important?
In the combustor the fuel ix mixed with high pressurized air coming from compressor. The mixture is burned and the high temperature exhaust gas is passed over the turbine and the turbine rotate.
The turbine in case of gas turbines can be reaction or impulse turbines. Turbines drives the compressors and powers up the compressors.
There are some turbine requirements like,
There are few interesting things about turbines,
The high-pressure turbine is helpful in increasing product of combustions. As we have already known the turbine and compressor are mounted on the same shaft.
The low-pressure turbine does the work of power generation. Its shaft is connected to the generator.
The intercooler is used in case of the compressor.
The regenerator work is to preheat the air flowing into combustion chamber to increase fuel efficiency and decrease the fuel consumption.
This one is the additional mounting available to the exhaust gases coming out from the high-pressure turbines.
It heats the products coming from a high-pressure turbine and then transfer to a low-pressure turbine.
Now we have known the parts or components used in the gas turbine. Now let’s see the brief about the types of gas turbine.
Let’s a very simple schematic diagram of a gas turbine to understand the parts.
Gas turbine with intercooler system is given below,
In the gas turbine parts, we have seen gas turbine can have regenerator system as well, so how it looks in schematics?
Refer the below images, to get a basic concept,
Now, this intercooler and regenerator can have in a single gas turbine, and the schematics will be simple, just both the things will be combined.
Firstly let’s know simple basic classifications of the gas turbines.
Basically, there are two classifications of gas turbines, open cycle gas turbine and closed-cycle gas turbine. But also, the turbines are classified on the basis of their operation, type of cycle used, etc.
Let’s check the gas turbine classifications.
On the basis of cycle of operation
On the basis of Thermodynamic cycle
According to applications
According to method of combustion
So, these are all the classifications of the gas turbines. There are various parts in working with the gas turbine.
The gas turbines are considered for replacements for cylinder piston type reciprocating combustions. These gas turbines are used in lots of applications as we have seen in the above classifications according to applications of gas turbines.
We have already seen various types of gas turbines. However, gas turbines are mainly working in line with Brayton Cycle.
A simple Brayton cycle is shall consists the followings:
Point 1-2 Process of Isentropic compression
In this process, compressor helps to compress the working gas adiabatically from point 1 to point 2.
Point 2-3 Process of Isobaric heat addition
Heat addition happens at constant pressure that is isobaric process.
Point 3-4 Process of Isentropic expansion
In this process, heated gas expanded adiabatically in the turbine from point 3 to point 4.
Point 4-1 Process of Isobaric heat rejection
Here, after expansion of the gas, it is required to reject the heat from the gas. How to do it? It simple, by using heat exchanger like point 4 to point 1, the heat can be rejected with a help of a heat exchanger.
Hence, we have understood that, there are two types of work,
New Work output = Wnet = W turbine – Wcomp
Now, after learning the basic principle, we will see how does an open and closed gas turbine works.
The open cycle gas turbine is the simplest constructed version.
It has the followings,
Let’s see the working of the open cycle turbine.
You can check gas turbine mathematical expressions.
So, how does an open cycle gas turbine work? – let’s learn step by step!
In the aircraft, open-cycle gas turbines are used where exhaust is released into the atmosphere.
Let’s check with a diagram,
The name open cycle gas turbine is because the expanded gas is directed towards the atmosphere. Thus, indicating an open cycle.
The expanded gas is wasted and the new fuel and air are burned in the combustion chamber again and the cycle continues.
Now let’s check out the closed cycle gas turbine working process.
So, let’s check how does a closed cycle gas turbine works? – let’s learn.
Check a NICE ANIMATED video from GE Power,
Let’s have a look at the difference between these two types of gas turbines,
The main differences are, as follows,
|Open Cycle GT||Closed Cycle GT|
|We have seen in the open cycle; the expanded gas is released to the atmosphere.||In case of the closed cycle, the expanded gas is reused after cooling.|
|Gas is replaced continuously as it is an open system||The same gas is continuously circulated as it is a closed system.|
|Working fluid is air.||Apart from air, other gas like helium can be used.|
|Normally used in moving vehicles.||Normally used for stationary applications.|
|Lower maintenance cost.||Higher maintenance cost comparatively.|
Now if you understood both types let’s check the close cycle advantages and disadvantages over the open cycle gas turbines.
Advantages of closed-cycle over the open cycle, are as follows,
Disadvantages of closed-cycle over the open cycle, are as follows,
The gas turbine can be coupled with other plants like steam power plants and diesel power plants. It can be used to satisfy different purposes for different processes. The combination of gas turbine cycles can be used in the following plants.
Combination with the steam power plants
Combination with the diesel power plants
Now we have known about the combinations the gas turbine can be used. Now let’s check out the advantages and disadvantages of gas turbines.
Advantages of gas turbines over steam turbines, are as follows,
Let’s have a look at the difference between gas turbines and steam turbines in tabulated form,
|Description||Gas turbine||Steam turbine|
|Basic Cycle||It works based on Brayton Cycle||It works based on Rankine Cycle|
|Working Fluid||It uses air or gas based on the applications||It uses steam|
|Power||Power generation depends on the combustion reaction and work output is in the form of toque or thrust||Power generation depends on the steam expansion and work output is in the form of toque|
|Components||Mainly compressor, combustion chamber, and power turbine are main components.||Boiler & accessories are used to produce the steam for steam turbine.|
|Efficiency||High with respect to steam turbine higher than steam turbines||Less with respect to gas turbine|
|Internal temperature||Very high, around 1500 deg. C based on project requirements.||Comparatively low, like 450-650 deg. C based on project requirements.|
|Lubrication||Lubrication of the is easy as only the lubrication of the main bearing and turbine is needed.||Here, it is complex.|
|Starting||Quick & Easy||Takes more time & Complex|
|Output||Torque or thrust||Torque|
|Startup and Control||Easy and quick. In case, load changes, control is easy for gas turbine.||Difficult and time taking. In case, load changes, control is complex for steam turbine.|
|Water Requirements||Not required||Main working fluid.|
Advantages are as follows,
The kind of turbines are popularly used in the aviation sector. Gas turbines provides the motive power required for the jet propulsion.
Electric power generation
The turbines available in electric power generations are steam turbines and gas turbines. Due to the its less space, easy to mount and other advantages gas turbines are also beneficial for the electric power generation.
Hence the gas turbines are widely used in medium sized peak load plants to run intermittently. Various other improvements and modernization is done to make the best use of gas turbines in electric power generations.
Uses in the industry
The size variation of the gas turbines enables it to be used in lots of industrial applications. It includes works like driving compressors, oil refining processes known houdry processes etc.
The gas turbines are lightweight and compact. In the year of 1970s, they were used by the US Navy to power ship by the gas turbines with 20000 horsepower.
They are now used to power other navy vessels.
The gas turbines were used to power up the locomotives in 1950-1960s year. But they didn’t have the success due to various reasons over the diesel-powered locomotives.
These are basically powered engines, widely used in the 1960s. But they didn’t that much of success. Later they were extensively used in supercharging and turbocharging. They became popular with the turbocharging and they are still used in the turbocharged vehicles.
Most importantly they are becoming more and more useful in electric power generation sectors. The advancements in gas turbines are making them even more useful and effective and various applications. The development of computational fluid dynamics, finite element analysis and advanced materials are helping gas turbines.
There are several gas turbine projects already executed across the word, a list is added for reference,
There are so many gas turbine manufacturers are available across the world, few of the main suppliers are captured below,
API STD 616 – Gas Turbines for Petroleum, Chemical, and Gas Industry Services,
SO 10494:2018 is applicable to turbines and turbine sets for power plant and industrial applications (e.g. stationery),
ISO 2314:2009 – Gas turbines — Acceptance tests,
ISO 3977-3:2004 design requirements for the procurement of all applications of gas turbines,Codes & Standards for Gas Turbine
Hence, we have got a basic idea about the gas turbines, its parts, types, working principle, advantages, disadvantages, etc. Any doubt, please let us know.
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