SIEMENS GAS TURBINE SGT-200

Siemens Gas Turbine SGT-200
Power output: ISO 6.75 MW(e) / 7.68 MW The robust and compact industrial gas turbine SGT-200 offers a power output of 6.75 MW for the

single shaft and 7.68 MW for the twin shaft configuration. The SGT-200 is designed to burn a wide range of gaseous and liquid fuels. It is available as a factory assembled package and provides an excellent power-to-weight ratio.

The single-shaft industrial gas turbine SGT-200-1S is an efficient unit used for industrial power generation in the following fields of application:

.simple cycle applications

.combined cycle applications

.combined heat and power (CHP)

power generation for the oil and gas industry, on offshore platforms and FPSO (Floating Production Storage and Offloading) vessels

The twin-shaft industrial gas turbine SGT-200-2S is a proven unit for mechanical drive of compressors and pumps, primarily for the oil and gas industry: It is designed for applications where speeds and loads vary. The SGT-200-2S can operate over a range of different speed and load demands.

Fields of Application:

drive solution for pumping applications including crude oil, other refinery product transmission and water injection drive solution for centrifugal compressors used in gas injection, pipeline transmission and boosting, gas processing and similar applications

SIEMENS GAS TURBINE SGT-200 1S:

DESIGN CONCEPT:
SGT-200-1S single-shaft turbine for Power Generation (up to 6.75 MW)The SGT-200-1S design is uniquely simple, employing a twin bearing gas generator, twin bearing power turbine and heavy duty casings. This allows full site maintenance to be carried out. The single shaft configuration provides excellent load acceptance and rejection characteristics, allowing robust and reliable operation in all applications. The gas turbine is available with a conventional or Dry Low Emissions (DLE) combustion system. Both systems provide dual fuel capability, the DLE system also providing extremely low NOx levels.



Power Generation Package

The SGT-200-1S is available as a factory assembled packaged power plant. It is easily transported, installed and maintained at site. The package incorporates the gas turbine, gearbox, generator and all systems mounted on a single underbase. Turbine controls, generator control panel, motor control center for package motors and variable speed drive for starter motor are normally also package-mounted.



Technical Data

*SGT-200-1S single-shaft turbine for Power Generation
*Power output 6.75 MW(e)
*Fuel: Natural gas / liquid fuel / dual fuel and other fuels capability on request
*Frequency: 50/60 Hz
*Electrical efficiency: 31.5 %
*Heat rate: 11,418 kJ/kW-hr (10,823 Btu/kW-hr)
*Turbine speed: 11,053 rpm
*Compressor pressure ratio: 12.2:1
*Exhaust gas flow / temperature: 29.3 kg/s, 466 °C (64.5 lb/s, 871 °F)
*NOx emissions (with DLE, corrected to 15 % O2 dry): ≤ 25 ppmV

SIEMENS GAS TURBINE SGT-200-2S

SGT-200-2S twin-shaft turbine for Mechanical Drives
Shaft output: (ISO) 7.68 MW
The Siemens SGT-200-2S twin-shaft industrial gas turbine is a proven unit for mechanical drive of compressors and pumps, and is widely used in the oil and gas industry. It offers outstanding reliability, efficiency and maintainability. It is designed to operate on a wide range of gaseous and liquid fuels.

PUMP APPLICATIONS:

The SGT-200-2S gas turbine provides an ideal drive solution for pumping applications. These include crude oil, product transmission and water injection. Drive from the power turbine is usually via a speed reducing gearbox.

COMPRESSOR APPLICATIONS

The SGT-200-2S offers exceptional performance for the drive of centrifugal compressors for gas injection, pipeline transmission and boosting, gas processing, refrigeration applications and a variety of other duties. Due to the high output speed of the power turbine and its ability to operate at full power between 8,000 rpm and 10,950 rpm, most compressor drive applications can be met without the need for a speed-changing gear between the power turbine and gas compressor.

DESIGN CONCEPT:

SGT-200-2S / Shaft output: 6.75 MW The twin-shaft configuration of the SGT-200-2S provides excellent speed and load turndown flexibility. The design is uniquely simple, employing a single gas generator rotor with twin bearings and a two-stage overhung turbine. Rotors are contained in heavy duty casings which are horizontally and vertically split, allowing full site maintenance to be carried out.


The turbine is available with a Dry Low Emissions (DLE) combustion system, providing extremely low NOx levels with gas and liquid fuels and a full dual fuel capability.



MECHANICAL DRIVE PACKAG:

The SGT-200-2S is available as a factory-assembled package for all mechanical drive applications. It is easily transported, installed and maintained at site. The package incorporates the gas turbine and all systems mounted on a single under base. It is very compact, providing a small footprint and a high power-to-weight ratio.



TECHNICAL DATA:

*SGT-200-2S twin shaft turbine for Mechanical Drive
*Shaft output: 7.68 MW (10,300bhp)
*Fuel: Natural gas / liquid fuel, dual fuel and other fuels capability on request
*Efficiency: 33 %
*Heat rate: 10,906 kJ/kW-hr (7,708 Btu/bhp-hr)
*Turbine speed: 10,950 rpm
*Compressor pressure ratio: 12.3:1
*Exhaust gas flow / temperature: 29.5 kg/s, 489 °C (65.0 lb/s, 912 °F)
*NOx emissions (with DLE, corrected to 15 % O2 dry): ≤ 15ppmV

BENEFITS:
SGT-200-2S

*Proven design resulting in high availability
*Dual-fuel Dry Low Emissions (DLE) combustion system, meeting the most stringent legislation
*Competitive cost-to-power ratio
*Compact size
*Site maintainability
*Alternate rapid core engine exchange option, minimizes downtime

SIEMENS GAS TURBINE SGT-100

Siemens Gas Turbine SGT-100
Power output: ISO 4.35 MW(e) up to 5.25 MW(e) The SGT-100 is an industrial gas turbine with a power output range from 4.35 to 5.25 MW. It offers simple construction along with the latest technology in a compact package. The SGT-100 is available in both single- and twin-shaft configuration.

The single-shaft industrial gas turbine SGT-100-1S is an efficient unit used for industrial power generation in the following fields of application:

.Simple cycle applications

.Combined cycle applications

.Combined heat and power (CHP)

Power generation for the oil and gas industry, on offshore platforms and FPSO vessels (Floating Production Storage and Offloading)

The twin-shaft industrial gas turbine SGT-100-2S is a proven unit for mechanical drive, primarily for the oil and gas industry: It is designed for applications where speeds and loads vary. The SGT-200-2S can operate over a range of different speed and load demands.

Fields of application:

.Drive solution for pumping applications, including crude oil, other refinery product transmission and water injection

.Drive solution for centrifugal compressors used in gas injection, pipeline transmission and boosting, gas processing and similar applications

OPTIMIZING TURBINE BLADES

New materials are making gas and steam turbine blades ever more resistant to heat and corrosion. This results in higher efficiency and lower fuel consumption, thus helping to cut environmental pollution.







(A 300-µm coating developed by Dr. Werner Stamm (left) increases the service life of turbine blades, including those on the world’s largest gas turbine)


As every cook knows, a pinch of salt can transform a bland dish into a tasty one. But just how big that pinch should be is usually a question of experience, and sometimes it has to be mixed with other spices to get the right taste. The lesson isn’t lost on Dr. Werner Stamm—the star chef of materials research at Siemens Power Generation (PG) in Mülheim an der Ruhr, Germany. Stamm is always thinking up new "recipes" for which he’s never received any cooking awards, but instead 52 patents and the title "2006 Inventor of the Year." That’s because his recipes help make gas turbine blades more resistant to heat and corrosion.

The latest spice in Stamm’s kitchen is rhenium, a rare metal characterized by a very high melting point and high density. Adding one to 2 % of rhenium to a mixture of cobalt, nickel, chromium, aluminum, and yttrium (so-called MCrAlY coatings) imbues the complex mixture with extraordinary properties.
At high temperatures, the mixture forms a barrier of aluminum oxide on the MCrAlY surface that protects turbine blades from oxygen in a combustion gas. The rhenium improves the mechanical properties of the protective coating and simultaneously prevents the aluminum from diffusing into the base material. "The coating stops the base material from oxidizing," says Stamm. Without it, the nickel base alloy in the blade would only survive 4,000 hours of operation at maximum operating temperatures. With the coating, however, the alloy can hold out against the oxygen for more than 25,000 hours, longer than power plant operators demand as a minimum.

Stamm’s coating, which is only around 300 micrometers thick, also has another function—to serve as an adhesive agent for ceramic thermal insulation layers. Given a gas temperature of approximately 1,500 °C, this composite system of adhesive agent and ceramic—in conjunction with a special blade-cooling setup that blows air from narrow jets onto the blades—reduces the surface temperature on the metal in the first row of blades from 1,200 to around 950 °C. The newest thermal insulation coating systems can even accommodate ceramic surface temperatures of up to 1,350 °C.

Percentage Points Worth Fighting For. But Stamm and his coworkers still aren’t satisfied. That’s because as temperature increases, the efficiency of the system (the share of useful energy obtained from combustion) improves. And with raw material prices rising, power plant operators and designers are struggling to achieve gains of just tenths of a percent. This was the rationale behind development of the most modern—and with 340 MW of output also the largest—gas turbine in the world, which Siemens delivered to the E.ON plant in Irsching in 2007. Plans call for the giant powerhouse to be used in conjunction with a steam turbine beginning in 2011—a system that is set to break the 60-% efficiency mark (see World’s Largest Gas Turbine). "This moves us into a completely new realm of technology," says Dr. Johannes Teyssen, chief operating officer of E.ON AG in Düsseldorf. "And we fully expect the higher efficiency to result in lower power generation costs."

Additional efficiency could be gained by reducing air cooling in the turbine blades, as the air used here is carried through the turbine, thus lowering efficiency. Less cooling air would, however, raise the temperature in the first row of blades by over 100 °C—too much for the materials currently used. The gas turbine in Irsching already has an optimal cooling system—thanks to Werner Stamm’s MCrAlY protective coating. However, as Stamm points out, it won’t be possible to determine exactly how the turbine handles the strain until after it’s been operating normally for several years. "Labs and real machines are two different things," he says.

Heat-resistant and heat-insulating protective coatings like Stamm’s still offer huge untapped potential. If, for example, researchers are able to increase the surface temperatures of the ceramic material and reduce the formation of oxides on the MCrAlY layer, both efficiency and operating life could be significantly increased. And ultimately, the special ceramics are only an interim step on the road to full ceramics that require no cooling. But that’s a long way off, says Stamm, "Maybe in 15 years—but people were also saying that 15 years ago."

Siemens' acquisition of Westinghouse has brought new life to ceramic development, and engineers are now trying to increase temperatures—and thus efficiency—by utilizing oxide ceramics. Other companies in the sector are opting for a base material of silicon carbide, whose structure and properties resemble those of diamonds. Silicon carbide is a high-strength material that has one key disadvantage: It oxidizes when in contact with oxygen at high temperatures—and oxygen is something gas turbines have plenty of. Siemens researchers are therefore focusing on the development of oxide ceramics that have already reacted with oxygen. The material’s lower rigidity is not a drawback, as the most important thing is its actual useful expansion, which is greater than that of silicon carbide.

Still, ceramic blades need to be reinforced if they’re going to survive at least the 25,000 hours of operation customers demand of them. That’s because ceramics are brittle. Dr. Ulrich Bast of Siemens Corporate Technology in Munich, together with colleagues in Orlando, Florida, are therefore developing and testing fiber-reinforced ceramics . "The fibers provide a reserve for handling stress and keep the ceramic intact, even if it already has cracks in some places," says Bast. The combination of two brittle materials—a ceramic matrix and fiber—results in high tolerance to strain and damage. The oxidized fibers of aluminum oxide and silicon dioxide nevertheless remain the weakest link in the chain. Although they too no longer react with oxygen, they can only withstand temperatures up to 1,200 °C. Ceramic alone can handle up to 1,700 °C; when used in certain gas turbine components, it therefore requires no cooling. The fiber compound thus has to be protected from the extreme temperature of the heated gas by a thick ceramic insulation. Tests on a ring segment made of fiber-reinforced ceramic have already produced very promising results.

Generation 50plus. E.ON plans to begin building a new generation of coal-fired steam power plants in 2014 that will achieve an efficiency of above 50 %. Several preliminary projects are now under way for "Generation 50plus," with Siemens working on the development of components for such a plant. At the Scholven power generation center near Gelsenkirchen, Germany, for example, the COMTES700 project is testing materials for use in boilers, pipes and turbines that will be exposed to a steam temperature of 700 °C. This high temperature will enable the new plants to make the leap in efficiency from today’s maximum 46 % to 50 %. But higher temperatures alone won’t be enough, according to Dr. Ernst-Wilhelm Pfitzinger, project manager for the 700-degree turbine in Mülheim. Pfitzinger says achieving the final percentage point will depend on finding a favorable location with good cooling conditions—like the Baltic Sea. In a study known as NRWPP700, several partners, including Siemens, are already designing a demonstration plant whose components will withstand steam temperatures of 720 °C.

While 720 °C might sound almost refreshing compared to the hellish temperatures in a gas turbine, the demands placed on high and medium-pressure turbines are nevertheless enormous. In addition to the heat, there’s also the stress of 250 bar of pressure; in E.ON’s 50plus plant, that will likely increase to 350 bar. By comparison, a normal gas turbine is subjected to a pressure of only 25 bar or so.

Engineers building the steam turbine at Siemens PG in Mülheim can call upon the material expertise of their colleagues from gas turbine development, but the processing of the materials is extremely difficult. Whereas housings, blades and shafts in a gas turbine have a filigree design and are formed from thin plates and sheets, the forged shafts of a large steam turbine can be up to a meter thick, and individual components can weigh more than 20 t. What’s more, after being processed, all components may not deviate from pre-calculated shapes by more than a few hundredths of a millimeter. Welded seams 20 cm wide require the use of completely new welding techniques and, above all, new testing methods such as X-ray procedures, and ultrasound cannot penetrate far enough into the metal. The processing of alloys into thick-walled forged and cast components also necessitates a complicated recalculation of material data that takes into account the hot steam atmosphere. Such efforts increase costs—and the new alloy is also five times more expensive than high-quality turbine steel. Designers therefore only want to use a nickel-based alloy for those components such as rotor cores, blades, and internal housings that are truly subjected to high stresses. "This requires not only new processing techniques for compounds of various metals but also new cooling concepts," says Pfitzinger. "However, it should be possible to go above 720 °C."




World’s Largest Turbine Blade. Jörn Bettentrup doesn’t have to worry about too much heat. A development project manager at Siemens PG, Bettentrup designs new running blades for the final stage of low-pressure steam turbines, which are generally used together with high and medium-pressure turbines. Steam in the three turbines gradually expands and then slackens in the end, cooling down to 30 °C at a pressure of 45 mbar. The expansion sharply increases the volume of flow, however, which means the last blade wheel has to be the largest. The biggest blade wheel made by Siemens for final-stage operation has a flow surface of 12.5 m². "The trend is toward even larger areas," says Bettentrup, which is why he and his team are looking to build a steam turbine with the world’s largest blade wheel area—16 m². The turbine is also to be used at the E.ON plant in Irsching. Even the jet engines in an Airbus A380 don’t come close to this.

There’s a simple reason why the giant wheel is so attractive to customers: A 16-m² turbine can replace two 8-m² turbines, which saves a lot of money in terms of room, bearings and piping. It presents a major challenge for developers, however, as associated centrifugal forces put huge stresses on the blades. At 3,000 revolutions per minute, several hundred tons of force act on the blade roots and the grooves that join it with the rotor. Conventional blade steel is not strong enough to withstand this, so engineers need a very rigid material that’s light, thereby reducing the centrifugal force. They’ve now decided on titanium, an expensive metal with a matte finish that’s also popular among jewelers. Titanium weighs around half as much as normal turbine steel, is somewhat stronger, and displays good erosion-resistance properties. Titanium’s ability to damp oscillations is, however, slightly lower than that of steel, which is why titanium blades are equipped with special coupling and support elements. The structure of this blade system is extremely complex.

Most manufacturers now offer titanium blades for the final stages of their low-pressure turbines—but none have dared to build one as big as Siemens plans to produce. Tests and experiments designed to overcome technical hurdles still need to be carried out before the design is approved. But all operating parameters have already been tested for around two years using a small model turbine. The blade development team’s job is now to employ the material in an optimal design at a favorable cost, as production of titanium blades is more complicated—and therefore more expensive—than the process for conventional steel blades. Additional costs are generated by the high and increasingly volatile price of raw materials. Despite this, Bettentrup’s calculations show that, "It will definitely pay off for our customers."

WORLD LARGEST GAS TURBINE

Unmatched Efficiency

The world’s largest turbine, with an output of 340 MW, will enter trial service in November 2007. In combination with a downstream steam turbine, it will help ensure that a new combined cycle power plant achieves a record-breaking efficiency of more than 60 % when it goes into operation in 2011.


Materials for the Environment – World’s Largest Gas Turbine

After assembly at Siemens’ gas turbine plant in Berlin (above), the world’s largest gas turbine hits the road. Bottom: The turbine arrives on a flatbed trailer at its destination




Residents of the town of Irsching in Bavaria, came out in droves this year to witness the traditional raising of their white and blue maypole. Three weeks later, they appeared in droves again—this time out of concern for the pole, as an oversized trailer had shown up carrying a new turbine for the town’s power plant. The residents were worried that the turbine, which measured 13 m in length, five meters in height, and weighed 444 t, could pose a threat to their beloved maypole. This was not the case, however; specialists supervising the transport were actually more concerned about a bridge at the entrance to the town, which they renovated as a precautionary measure prior to the turbine’s arrival.

The world’s largest turbine, which was built at Siemens’ Power Generation (PG) plant in Berlin, traveled 1,500 km to get to Irsching—initially by water along the Havel river, various canals, the Rhine, and the Main. It then went down the Main-Danube Canal to Kelheim, where it was loaded onto a truck for the final 40 km. This odyssey was undertaken because the only way to truly test such a large and powerful turbine is to put it into operation at a power plant. "It was a nice coincidence that the energy company E.ON was planning to expand the power station in Irsching," says Hans-Otto Rohwer, PG project manager in Irsching.

Siemens will now build a combined cycle plant at the Bavarian facility (Block 5) for E.ON Kraftwerke GmbH. Scheduled for completion in 2009, the plant will house two small gas turbines and a steam turbine. Siemens will also build the plant’s new Block 4, where the giant turbine will be installed. The new turbine’s output of 340 MW, which equals that of 13 jumbo jet engines, is enough to supply power to the population of a city the size of Hamburg.

"Block 4 is our project at the moment," says Rohwer. Siemens will use the existing infrastructure here, purchase gas from E.ON-Ruhrgas, and sell the electricity it produces at the plant. That’s not that important now, however, as the turbine first needs to be tested over the next 18 months. To this end, the unit has been equipped with 3,000 sensors that measure just about everything modern technology can register—from temperature and pressure to mechanical stress and material strain. If a component is defective, or fails, computers linked to the sensors call attention to the problem immediately. The component will then be removed, replaced, or reworked.

Most of the measuring technology is hidden; the thing that stands out at the facility is a section of 21 office trailers housing the measurement stations. The trailers look tiny next to the turbine hall, which is 30 m high. Despite its massive size, the new facility’s metal facade makes it seem light and modern compared to the plant’s three old concrete towers from the 1960s and ’70s, each of which is 200 m high. "The hall is still a long way from finished," says Rohwer, as he points to a big hole in the floor between the turbine and generator. "This is where we’re going to install the oil systems to keep all movable parts of the shaft assembly lubricated. This is also where most of the smokestack, nearly all the electrical equipment, and the gas tanks will be located."

Efficiency Record. Rohwer points to an opening in one of the walls and explains that it is the connection to the air intake unit, which will draw in fresh air from the outside. Equipped with a special housing, filters, and sound absorbers, the unit will channel in 800 kg of air per second when the facility operates at full capacity—an amount that would exhaust the air inside the hall in just a few minutes. But it will be worth the effort because the gas turbine and a downstream steam turbine will set a new world record with an efficiency rating of over 60 %, two percentage points higher than the previous titleholder, the Mainz-Wiesbaden power plant. Relatively speaking, therefore, less fuel will be burned and 40,000 t less carbon dioxide (CO2) per year will be emitted into the atmosphere than would be the case with the Mainz-Wiesbaden plant. And compared to the average coal-fired plant, which has an efficiency of 42 %, the new facility in Irsching will emit around 2.3 million t less CO2 per year, while producing the same amount of electricity.



Weighing in at 444 t, the world’s largest turbine is carefully positioned

There will still be plenty of work to do even after the plant has been built, as technicians will have to test all systems to ensure that the gas lines are pressure-tight, electrical cables are properly secured, and all valves open and close quickly and reliably. It’s like a final check before a space mission—and the countdown is now under way, with ignition scheduled for mid-December, 2007.

There’s good reason for Siemens’ decision to use one giant turbine rather than the two smaller ones E.ON will put into operation next door. "The price per megawatt (MW) of output and efficiency correlate with the size of the turbine—in other words, the bigger it is, the more economical it will be," explains Willibald Fischer, who is responsible for development of the 8000H turbine family. "In 1990, the largest gas turbine produced 150 MW, and, in conjunction with a 75-MW steam turbine, had an efficiency of 52 %. Our gas turbine has an output of 340 MW. In combination with a 190-MW steam turbine it utilizes more than 60 % of the energy content of the gas fuel."

Engineers at PG overcame two challenges while designing the turbine. They increased the amount of air and combustion gases that flow through the turbine each second, which causes output to rise more than the losses in the turbine, and they raised the temperature of the combustion gases, which increases efficiency. "It’s tricky when you send gas heated to 1,200 to 1,500 °C across metal turbine blades," says Fischer. "That’s because the highest temperature the blade surfaces are allowed to be exposed to is 950 degrees, at which point they begin to glow red. If it gets any hotter, the material begins to lose its stability and oxidizes."

Ceramic Coating. Siemens engineers have been creative in tackling this problem. One thing they did was lower the heat transfer from the combustion gas to the metal by applying a protective thermal coating consisting of two layers: a 300-µm-thick undercoating directly on the metal and a thin ceramic layer on top of that, which provides heat insulation (see Optimizing Turbine Blades: Taking the Heat). The blades are also actively cooled, as they are hollow inside and are exposed to cool airflows generated by the compressor. The blades at the very front (the hottest part of the turbine) also have fine holes, from which air is released that then flows across the blades, covering them with a thin insulating film, like a protective shield.

As turbine blades spin, massive centrifugal forces come into play. The end of each blade is exposed to a maximum force of 10,000 times the earth’s gravitational pull, which is the equivalent of each cubic centimeter of such a blade weighing as much as an adult human being.

The blades are made of a nickel alloy. These used to be cast and then left to harden. Later, crystallites were made to grow in the same direction as the centrifugal forces. But now the blades on the giant turbine in Irsching contain alloys that have mostly been grown as single crystals through the utilization of special cooling processes. They are therefore extremely resistant to breaking, as there are no longer any grain boundaries between the crystallites in the alloy that can rupture.

Engineers also optimized the shape of the blades with the help of 3D simulation programs, whereby the edges were designed to keep the gap between the blades and the turbine wall as small as possible. As a result, practically all the gas passes across the blades and is utilized. The blade-wall gap is made even smaller due to the turbine’s operation in a cone. This means that the shaft can be shifted several millimeters during operation until the blades nearly touch the housing—a practice known as "hydraulic gap optimization."

Trial Run. Each off the measures mentioned above produces only a fractional increase in efficiency or output. But taken together they add up to a new record. Whether or not everything works as planned will be revealed by the 18-month trial period that will begin in November 2007. If preliminary test results are satisfactory, engineers will sign off on the new mega-turbine in August 2008, allowing Siemens to begin marketing it.

After successful completion of all tests in mid-2009, things will quiet down in Irsching. The turbine will then be overhauled and disassembled, and all of its components will be thoroughly examined. If everything is found to be in order, the unit will be reassembled minus its specialized measuring equipment.

During the overhaul, engineers will install an additional steam turbine on the shaft at the end of the generator. The turbine will make use of the generator’s 600-°C gas to generate steam in a heat exchanger. Only through this combined cycle process can the energy in the gas be so effectively exploited as to achieve the record efficiency of 60 %.

Conventional gas turbine power plants are generally pure peak-load facilities that can be turned on very quickly. But the Irsching plant is simply too good for that. "If the gas turbine proves itself during the trial period, we’ll assume control of the plant in 2011," says Alfred Beck from E.ON Kraftwerke GmbH. "It’s high efficiency will make it profitable for use in medium load operations, despite slightly higher gas prices." The facility will then generate electricity for between 3,000 and 7,000 hours each year, and will definitely be a superlative power plant.
Bernhard Gerl

BRAYTON CYCLE

Four processes occur in gas turbine engines, as illustrated above. These processes, first
described by George Brayton and called the Brayton cycle, occur in all internal combustion
engines. The Brayton steps are as follows:
> Compression occurs between the intake and the outlet of the compressor (Line A-B).
During this process, pressure and temperature of the air increases.
> Combustion occurs in the combustion chamber where fuel and air are mixed to explosive proportions and ignited. The addition of heat causes a sharp increase in volume (Line B-C)
> Expansion occurs as hot gas accelerates from the combustion chamber. The gases at constant pressure and increased volume enter the turbine and expand through it. The sharp decrease in pressure and temperature (Line C-D).
> Exhaust occurs at the engine exhaust stack with a large drop in volume and at a constant pressure (Line D-A).

The number of stages of compression and the arrangement of turbines that convert the energy of accelerating hot gas into mechanical energy are design variables. However, the basic operation of all gas turbines is the same.