This document discusses ways to improve the efficiency of gas turbine engines through various design modifications and upgrades. It describes how increasing turbine inlet temperatures, improving compressor and turbine components, adding modifications like intercooling and regeneration, and utilizing advanced cooling techniques can boost efficiency. Other methods covered include inlet air cooling systems, compressor and turbine coatings, supercharging, and comprehensive component replacements. The goal of ongoing research is to enhance power output while reducing emissions and fuel consumption.

1. Greetings, Dear Viewers !!
Topic of Discussion: Improved Efficiency of Gas turbine
Presenter: Razin Sazzad Molla
Course: ART- 203
ID: 13107010

2. Gas turbine engine (overview)
• A gas turbine engine, also called a combustion turbine, is a type of internal combustion engine. It has an
upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in between.
• The two major application areas of gas-turbine engines are aircraft propulsion and electric power generation.
When it is used for aircraft propulsion, the gas turbine produces just enough power to drive the compressor
and a small generator to power the auxiliary equipment. The high-velocity exhaust gases are responsible for
producing the necessary thrust to propel the aircraft. Gas turbines are also used as stationary power plants to
generate electricity as stand-alone units or in conjunction with steam power plants on the high-temperature
side.
• All the gas turbines work on Ideal Brayton cycle and fresh atmospheric air works as the working fluid.
• They have very high power to weight ratio compared to other types of IC engine. Compared to steam-turbine
and diesel propulsion systems, the gas turbine offers greater power for a given size and weight, high reliability,
long life, and more convenient operation.
• They also have high back work ratio. (the amount of work needed to run the compressor)
• They usually have less efficiency when simple cycle is used. Efficiency can be as low as 20% only. With
intercooling, reheating and regeneration efficiency can be as high as 69%.

3. • Compressor and turbine are turbo machinery components and efficiency of the gas turbine engine greatly depends on
performance of the components.
• Various types of gas turbine engines for aircraft propulsion are turbojet engine, turboprop engine, turbofan engine,
ramjet or scramjet engine.
Examples of gas turbine configurations:
turbojet
turboprophigh-bypass turbofan

4. turboshaft (electric generator)
low-bypass afterburning turbofan

5. • Gas turbines are used to power aircraft, trains, ships, electrical generators, and tanks.
• Industrial gas turbines differ from aeronautical designs in that the frames, bearings, and blading are of heavier
construction. They are also much more closely integrated with the devices they power— often an electric generator
• The gas turbine engine design is fundamentally, taking the air flow into the compressing stage then combustion stage
to add energy, and finally extracting energy in the turbine module. This journey of the flow in the engine is in serial
connections.

6. Gas turbine engine configuration varies greatly upon its application, when it is used for
aircraft propulsion propulsive power is the most important consideration whereas gas
turbine power plant uses most of its power to rotate the generator.
Turbo jet engine
Gas turbine power
plant

7. Major manufacturers of Gas turbine engines
Some of the well known companies that have been producing gas turbine engines
for all sort of applications are :
• General Electric
• GE-Aviation — US.
• Rolls Royce (Produce engines for Boeing & Airbus)
• United Technologies (Pratt & Whitney)
• Mitsubishi Hitachi Power Systems (MHPS)
• Siemens
• Alstom
The General Electric LM2500
is an industrial and marine
gas turbine produced by GE
Aviation.
The Rolls-Royce RB211 is
a British family of high-
bypass turbofan engines
made by Rolls-Royce

8. Efficiency analysis and factors that affect the gas turbine efficiency
Generally efficiency is determined
for simple ideal Brayton cycle by the
following equation
𝜂 𝑡ℎ,𝐵𝑟𝑎𝑦𝑡𝑜𝑛 = 1 −
1
𝑟𝑃
(𝑘−1)/𝑘
where pressure ratio, 𝑟𝑃 =
𝑃2
𝑃1
and 𝑘
is the specific heat ratio
Thermal efficiency of the ideal Brayton
cycle as a function of the pressure ratio.

9. For fixed values of 𝑇 𝑚𝑖𝑛 and
𝑇 𝑚𝑎𝑥, the net work of the
Brayton cycle first increases
with the pressure ratio, then
reaches a maximum at
𝑟𝑃 = (𝑇 𝑚𝑎𝑥/𝑇 𝑚𝑖𝑛) 𝑘/[2(𝑘−1)]
and finally decreases.

10. Typical thermodynamical methods of increasing the efficiency
1. Increasing the turbine inlet (or firing) temperatures This has been the primary
approach taken to improve gas-turbine efficiency. The turbine inlet temperatures have
increased steadily from about 540 deg C (1000F) in the 1940s to 1425 deg C (2600F) and
even higher today. These increases were made possible by the development of new
materials and the innovative cooling techniques for the critical components such as coating
the turbine blades with ceramic layers and cooling the blades with the discharge air from
the compressor. Maintaining high turbine inlet temperatures with an air-cooling technique
requires the combustion temperature to be higher to compensate for the cooling effect of the
cooling air. However, higher combustion temperatures increase the amount of nitrogen
oxides (NOx), which are responsible for the formation of ozone at ground level and smog.
Using steam as the coolant allowed an increase in the turbine inlet temperatures by 2008F
without an increase in the combustion temperature. Steam is also a much more effective
heat transfer medium than air.

11. 2. Increasing the efficiencies of turbomachinery components The performance of early
turbines suffered greatly from the inefficiencies of turbines and compressors. However,
the advent of computers and advanced techniques for computer-aided design made it
possible to design these components aerodynamically with minimal losses. The increased
efficiencies of the turbines and compressors resulted in a significant increase in the cycle
efficiency.
3. Adding modifications to the basic cycle The simple-cycle efficiencies of early gas
turbines were practically doubled by incorporating intercooling, regeneration (or
recuperation), and reheating

12. THE BRAYTON CYCLE WITH REGENERATION
A gas-turbine
engine with
regenerator.
the thermal efficiency of an ideal Brayton cycle with
regeneration depends on the ratio of the minimum to
maximum temperatures as well as the pressure ratio.

13. Thermal efficiency of the ideal
Brayton cycle with and without
regeneration.

14. THE BRAYTON CYCLE WITH INTERCOOLING, REHEATING, AND REGENERATION
A gas-turbine engine with two-stage compression with
intercooling, two-stage expansion with
reheating, and regeneration.

15. Advanced cooling techniques
Advanced heat transfer and cooling techniques form one of the major pillars supporting the
continuing development of high efficiency, high power output gas turbine engines.
Conventional gas turbine thermal management technology is composed of five main elements
including internal convective cooling, external surface film cooling, materials selection,
thermal-mechanical design at the component and system levels, and selection and/or pre-
treatment of the coolant fluid.
Upgraded cooling technologies representing cutting edge, innovative methods expected to
further enhance the aero-thermal-mechanical performance of turbine engines. The techniques
are forced convective cooling with unconventional turbulators and concavity surface arrays,
swirl-cooling chambers, latticework cooling networks, augmentations of impingement heat
transfer, synergistic approaches using mesh networks, and film cooling.

16. The technology of cooling gas turbine components, primarily via internal convective flows
of single-phase gases and external surface film cooling with air, has developed over the
years into very complex geometries involving many differing surfaces, architectures, and
fluid-surface interactions. The fundamental aim of this technology area is to obtain the
highest overall cooling effectiveness with the lowest possible penalty on the
thermodynamic cycle performance. As a thermodynamic Brayton cycle, the efficiency of
the gas turbine engine can be raised substantially by increasing the firing temperature of
the turbine. Modern gas turbine systems are fired at temperatures far in excess of the
material melting temperature limits. This is made possible by the aggressive cooling of the
hot gas path components using a portion of the compressor discharge air, as depicted in the
following figure.

18. Advanced cooling methods
• Turbulated channel cooling
• Mesh network and micro cooling
• Latticework (vortex) cooling
• Augmented surface impingement cooling
• Concavity surfaces cooling
• Swirl (cyclone) cooling
• Film cooling

19. Comprehensive Upgrades
Comprehensive upgrades of gas turbine involve the replacement of “flange-to-flange” parts with more advanced
designs. Because late-model gas turbines already incorporate advanced technology, these comprehensive upgrades
apply only to older gas turbines that are part of a series or model line that the original equipment manufacturer
(OEM) has redesigned. Examples of these model lines include the Frame 7 and 9 series supplied by GE Power
Systems, Schenectady, NY, and the W251 and W501 series supplied by Siemens Westinghouse Power Corp.,
Orlando, Florida. An upgrade can be applied to individual components or to the entire engine. Examples of
components that can be upgraded include:
• Inlet guide vanes, which allow more air flow
• Improved seals, tighter clearances
• Combustion liners and transition pieces, enabling higher firing temperatures
• Turbine blades and vanes, also enabling higher firing temperatures
The upgrades of eight GE Frame 7Bs by Houston Light & Power Co. (now Reliant Energy HL&P, Houston Texas)
in the 1990s provide a good example of what can be accomplished. Reliant replaced the combustion liners,
transition pieces, 1st stage turbine vanes, and 2nd stage vanes and blades with Frame 7EA parts. This allowed
operators to increase the firing temperature of the machines by 170 deg F. After the upgrades, the eight machines
yielded power increases of 16 to 26%, while the heat rate decreased by 4.5 to 11%

20. The development of ceramic materials for incorporation into the hot section of gas
turbine engines has been ongoing for about fifty years.
Researchers have designed, developed, and tested ceramic gas turbine components in
rigs and engines for automotive, aero-propulsion, industrial, and utility power
applications.
Today, primarily because of materials limitations and/or economic factors, major
challenges still remain for the implementation of ceramic components in gas turbines.
For example, because of low fracture toughness, monolithic ceramics continue to suffer
from the risk of failure due to unknown extrinsic damage events during engine service.
On the other hand, ceramic matrix composites (CMC) with their ability to display much
higher damage tolerance appear to be the materials of choice for current and future
engine components. CMC materials can be implemented within the combustor and
turbine sections for gas turbine engine applications.
Use of ceramic materials(CMC) in different turbomachinery components

21. Hot Section Coatings
Another option for upgrading gas turbine performance is to apply ceramic coatings to internal
components. Thermal barrier coatings (TBCs) are applied to hot section parts in advanced gas
turbines. These same coatings can be applied to the hot sections of older gas turbines in the
field. The TBCs provide an insulating barrier between the hot combustion gases and the metal
parts. TBCs will provide longer parts life at the same firing temperature, or will allow the user
to increase firing temperature while maintaining the original design life of the hot section. A
recent analysis sponsored by the Combustion Turbine Combine Cycle Users Organization
showed that adding a 10 mil coating to the 1st stage blades and vanes of a GE Frame 7EA
would allow an increase in firing temperature from 2020 deg F to 2035 deg F. The report
calculated that this small increase could provide $4 million of net revenue over the life of the
coating. A similar study conducted by Fern Engineering, Inc., Pocasset, Mass., for the Electric
Power Research Institute, Palo Alto, Calif., concluded that the addition of TBCs to a GE
Frame 7B would provide an increase of 5.5 MW in power, at an incremental cost of $140/kW.

22. Compressor Coatings can also be applied to gas turbine compressor blades (the “cold end”
of the machine) to improve performance. Unlike hot section coatings, the purpose of
compressor blade coatings is not to insulate the metal blades from the compressed air.
Rather, the coatings are applied in order to provide smoother, more aerodynamic surfaces,
which increase compressor efficiency.
Figure: Corrosion-resistance tests conducted on high-pressure compressor vanes revealed
the significant benefit of coatings. The upper section has no coating; bottom section was
coated with SermeTel 5380DP.

24. Supercharging
A more novel approach, but one that deserves more attention, is supercharging. Supercharging of a gas turbine
entails the addition of a fan to boost the pressure of the air entering the inlet of the compressor by 40 to 80 in.
H2O. In some ways, supercharging mimics the upgrade tactic used by several OEMs of adding a “zero stage”
to the compressor. However, in the case of supercharging the additional stage of compression is not driven by
the main gas turbine shaft, but rather by an electric motor. The parasitic power of the fan motor is less than the
additional output of the gas turbine, so the net result is a capacity boost.
The impact of supercharging is especially significant if it is coupled with inlet fogging downstream of the fan.
The fan stage increases the air temperature, which increases the difference between the dry bulb and wet bulb
temperatures. This allows more cooling to be provided by the fogging system.
One application of supercharging was on a W301G combined cycle in San Angelo, Texas, in the 1960s.
However, analysis has shown that the net power boost from supercharging increases with turbine firing
temperature (Figure 3). As a result, the cost per kilowatt of supercharging should be significantly less than it
was for turbines built 40 years ago.

25. Figure 4: Supercharging a gas turbine boosts power output in
proportion to firing temperature. Graph assumes a 40 in. H2O,
fan-driven pressure increase, followed by fog cooling back to
ambient temperature.

26. Improvement of gas turbine performance based on inlet air cooling systems
Performance of a gas turbine mainly depends on the inlet air temperature. The power output
of a gas turbine depends on the flow of mass through it. This is precisely the reason why on
hot days, when air is less dense, power output falls off. A rise of 1°C temperature of inlet air
decreases the power output by 1%.
GAS TURBINE INLET AIR COOLING SYSTEM
The gas turbine inlet air cooling methods can be divided
into five categories including the evaporative cooler, indirect
mechanical refrigeration system, direct mechanical
refrigeration system, mechanical refrigeration system with
chilled water storage and absorption chiller inlet air cooling
system.

27. Fig : Schematic of evaporative air cooling with optional water
treatment.

28. Figure: Gas turbine with mechanical chiller.

29. Conclusion
Gas turbine performance is a crucial matter since it contributes to world’s power production
in a great extent. Various researches have been going on in many different countries at
world’s leading manufacturing labs to increase the power with reduced fuel consumption.
Environmental issue is also a great concern. Researchers are generally focused on reducing
emissions while working at a peak performance.