Part of a gas turbine. Gas turbine. Device and principle of operation. Industrial equipment. Use of gas turbines
Gritsyna V.P.
In connection with the multiple growth of electricity tariffs in Russia, many enterprises are considering the construction of their own low-capacity power plants. In a number of regions, programs are being developed for the construction of small or mini thermal power plants, in particular, as a replacement for obsolete boiler houses. At a new small CHP plant with a fuel utilization rate of up to 90% with full use of the body in production and for heating, the cost of electricity received can be significantly lower than the cost of electricity received from the power grid.
When considering projects for the construction of small thermal power plants, power engineers and specialists of enterprises are guided by the indicators achieved in the large power industry. Continuous improvement of gas turbines (GTUs) for use in large-scale power generation has made it possible to increase their efficiency to 36% or more, and the use of a combined steam-gas cycle (CCGT) has increased the electrical efficiency of TPPs to 54% -57%.
However, in small-scale power generation it is inappropriate to consider the possibility of using complex schemes of combined cycles of CCGT for electricity generation. In addition, gas turbines, in comparison with gas engines, as drives for electric generators, lose significantly in terms of efficiency and performance, especially at low powers (less than 10 MW). Since in our country neither gas turbines nor gas piston engines have yet been widely used in small-scale stationary power generation, the choice of a specific technical solution is a significant problem.
This problem is also relevant for large-scale energy, i.e. for power systems. In modern economic conditions, in the absence of funds for the construction of large power plants on obsolete projects, which can already be attributed to the domestic project of a 325 MW CCGT, designed 5 years ago. Energy systems and RAO UES of Russia should pay special attention to the development of small-scale power generation, at whose facilities new technologies can be tested, which will make it possible to begin the revival of domestic turbine-building and machine-building plants and, in the future, move to large capacities.
In the last decade, large diesel or gas engine thermal power plants with a capacity of 100-200 MW have been built abroad. The electrical efficiency of diesel or gas engine power plants (DTPP) reaches 47%, which exceeds the performance of gas turbines (36%-37%), but is inferior to the performance of CCGTs (51%-57%). CCGT power plants include a large range of equipment: a gas turbine, a waste heat steam boiler, a steam turbine, a condenser, a water treatment system (plus a booster compressor if low or medium pressure natural gas is burned. Diesel generators can run on heavy fuel, which is 2 times cheaper than gas turbine fuel and can operate on low-pressure gas without the use of booster compressors.According to S.E.M.T. PIELSTICK, the total cost over 15 years for the operation of a diesel power unit with a capacity of 20 MW is 2 times less than for a gas turbine thermal power plant of the same capacity when using liquid fuel by both power plants.
A promising Russian manufacturer of diesel power units up to 22 MW is the Bryansk Machine-Building Plant, which offers customers power units with increased efficiency up to 50% for operation both on heavy fuel with a viscosity of up to 700 cSt at 50 C and a sulfur content of up to 5%, and for operation on gaseous fuel.
The option of a large diesel thermal power plant may be preferable to a gas turbine power plant.
In small-scale power generation, with unit capacities of less than 10 MW, the advantages of modern diesel generators are even more pronounced.
Let us consider three variants of thermal power plants with gas turbine plants and gas piston engines.
The fuel utilization factor for the first two options of power plants (with different electrical efficiency) due to heat supply can reach 80% -94%, both in the case of gas turbines and for motor drives.
The profitability of all variants of power plants depends on the reliability and efficiency, first of all, of the "first stage" - the drive of the electric generator.
Enthusiasts for the use of small gas turbines are campaigning for their widespread use, noting the higher power density. For example, in [1] it is reported that Elliot Energy Systems (in 1998-1999) is building a distribution network of 240 distributors in North America providing engineering and service support for the sale of "micro" gas turbines. The power grid ordered a 45 kW turbine to be ready for delivery in August 1998. It also stated that the electrical efficiency of the turbine was as high as 17%, and noted that gas turbines were more reliable than diesel generators.
This statement is exactly the opposite!
If you look at Table. 1. then we will see that in such a wide range from hundreds of kW to tens of MW, the efficiency of the motor drive is 13% -17% higher. The indicated resource of the motor drive of the company "Vyartsilya" means a guaranteed resource up to full overhaul. The resource of new gas turbines is a calculated resource, confirmed by tests, but not by statistics of work in real operation. According to numerous sources, the resource of gas turbines is 30-60 thousand hours with a decrease with a decrease in power. The resource of diesel engines of foreign production is 40-100 thousand hours or more.
Table 1
Main technical parameters of electric generator drives
G-gas-turbine power plant, D-gas-piston generating plant of Vyartsilya.
D - diesel from the Gazprom catalog
* The minimum value of the required pressure of the fuel gas = 48 ATA!!
Performance characteristics
Electrical efficiency (and power) According to Värtsilä data, when the load is reduced from 100% to 50%, the efficiency of an electric generator driven by a gas engine changes little.
The efficiency of a gas engine practically does not change up to 25 °C.
The power of the gas turbine drops evenly from -30°C to +30°C.
At temperatures above 40 °C, the reduction in gas turbine power (from nominal) is 20%.
Start time gas engine from 0 to 100% load is less than a minute and emergency in 20 seconds. It takes about 9 minutes to start a gas turbine.
Gas supply pressure for a gas turbine it should be 16-20 bar.
The gas pressure in the network for a gas engine can be 4 bar (abs) and even 1.15 bar for a 175 SG engine.
Capital expenditures at a thermal power plant with a capacity of about 1 MW, according to Vartsila specialists, they amount to $1,400/kW for a gas turbine plant and $900/kW for a gas piston power plant.
Combined cycle application at small CHPPs, by installing an additional steam turbine is impractical, since it doubles the number of thermal and mechanical equipment, the area of the turbine hall and the number of maintenance personnel with an increase in power only 1.5 times.
With a decrease in the capacity of the CCGT from 325 MW to 22 MW, according to the data of the NPP "Mashproekt" plant (Ukraine, Nikolaev), the front efficiency of the power plant decreases from 51.5% to 43.6%.
The efficiency of a diesel power unit (using gas fuel) with a capacity of 20-10 MW is 43.3%. It should be noted that in the summer, at a CHPP with a diesel unit, hot water supply can be provided from the engine cooling system.
Calculations on the competitiveness of power plants based on gas engines showed that the cost of electricity at small (1-1.5 MW) power plants is approximately 4.5 cents / kWh), and at large 32-40 MW gas-powered plants 3, 8 US cents/kWh
According to a similar calculation method, electricity from a condensing nuclear power plant costs approximately 5.5 US cents/kWh. , and coal IES about 5.9 cents. US/kWh Compared to a coal-fired CPP, a plant with gas engines generates electricity 30% cheaper.
The cost of electricity produced by microturbines, according to other sources, is estimated at between $0.06 and $0.10/kWh
The expected price for a complete 75 kW gas turbine generator (US) is $40,000, which corresponds to the unit cost for larger (more than 1000 kW) power plants. The big advantage of power units with gas turbines is their smaller dimensions, 3 or more times less weight.
It should be noted that the unit cost of Russian-made electric generator sets based on automobile engines with a capacity of 50-150 kW may be several times less than the mentioned turbo blocks (USA), given the serial production of engines and the lower cost of materials.
Here is the opinion of Danish experts who evaluate their experience in the implementation of small power plants.
"Investment in a completed turnkey natural gas CHP plant with a capacity of 0.5-40 MW is 6.5-4.5 million Danish krone per MW (1 krone was approximately equal to 1 ruble in the summer of 1998) Combined cycle CHP plants below 50 MW will achieve an electrical efficiency of 40-44%.
Operating costs for lubricating oils, Maintenance and the maintenance of personnel at CHPs reach 0.02 kroons per 1 kWh produced by gas turbines. At CHP plants with gas engines, operating costs are about 0.06 dat. kroons per 1 kWh. At current electricity prices in Denmark, the high performance of gas engines more than offsets their higher operating costs.
Danish specialists believe that most CHP plants below 10 MW will be equipped with gas engines in the coming years."
findings
The above estimates, it would seem, unambiguously show the advantages of a motor drive at low power of power plants.
However, at present, the power of the proposed Russian-made motor drive on natural gas does not exceed the power of 800 kW-1500 kW (RUMO plant, N-Novgorod and Kolomna Machine Plant), and several plants can offer turbo drives of higher power.
Two factories in Russia: plant im. Klimov (St. Petersburg) and Perm Motors are ready to supply complete power units of mini-CHP with waste heat boilers.
In the case of organizing a regional service center issues of maintenance and repair of small turbines of turbines can be solved by replacing the turbine with a backup one in 2-4 hours and its further repair in the factory conditions of the technical center.
The efficiency of gas turbines can currently be increased by 20-30% by applying power injection of steam into a gas turbine (STIG cycle or steam-gas cycle in one turbine). In previous years, this technical solution was tested in full-scale full-scale field tests of the Vodoley power plant in Nikolaev (Ukraine) by Mashproekt Research and Production Enterprise and Zarya Production Association, which made it possible to increase the power of the turbine unit from 16 to 25 MW and the efficiency was increased from 32 .8% to 41.8%.
Nothing prevents us from transferring this experience to smaller capacities and thus implementing a CCGT in serial delivery. In this case, the electrical efficiency is comparable to that of diesel engines, and the specific power increases so much that capital costs can be 50% lower than in a gas engine-driven CHP plant, which is very attractive.
This review was carried out in order to show: that when considering options for the construction of power plants in Russia, and even more so the directions for creating a program for the construction of power plants, it is necessary to consider not individual options that design organizations can offer, but a wide range of issues taking into account the capabilities and interests of domestic and regional manufacturers equipment.
Literature
1. Power Value, Vol.2, No.4, July/August 1998, USA, Ventura, CA.
The Small Turbine Marketplace
Stan Price, Northwest Energy Efficiency Council, Seattle, Washington and Portland, Oregon
2. New directions of energy production in Finland
ASKO VUORINEN, Assoc. tech. Sciences, Vartsila NSD Corporation JSC, "ENERGETIK" -11.1997. page 22
3. District heating. Research and development of technology in Denmark. Ministry of Energy. Energy Administration, 1993
4. DIESEL POWER PLANTS. S.E.M.T. PIELSTICK. POWERTEK 2000 Exhibition Prospectus, March 14-17, 2000
5. Power plants and electrical units recommended for use at the facilities of OAO GAZPROM. CATALOG. Moscow 1999
6. Diesel power station. Prospect of OAO "Bryansk Machine-Building Plant". 1999 Exhibition brochure POWERTEK 2000/
7. NK-900E Block-modular thermal power plant. OJSC Samara Scientific and Technical Complex named after V.I. N.D. Kuznetsova. Exhibition brochure POWERTEK 2000
A traditional modern gas turbine plant (GTP) is a combination of an air compressor, a combustion chamber and a gas turbine, as well as auxiliary systems that ensure its operation. The combination of a gas turbine and an electric generator is called a gas turbine unit.
It is necessary to emphasize one important difference between GTU and PTU. The composition of the PTU does not include a boiler, more precisely, the boiler is considered as a separate source of heat; With this consideration, the boiler is a “black box”: feed water enters it with a temperature of $t_(p.w)$, and steam comes out with parameters $p_0$, $t_0$. A steam turbine plant cannot operate without a boiler as a physical object. In a gas turbine, the combustion chamber is its integral element. In this sense, GTU is self-sufficient.
Gas turbine plants are extremely diverse, perhaps even more than steam turbines. Below we will consider the most promising and most used gas turbines of a simple cycle in the power industry.
circuit diagram such a gas turbine is shown in the figure. Air from the atmosphere enters the inlet of an air compressor, which is a rotary turbomachine with a flow path consisting of rotating and fixed gratings. Compressor pressure ratio p b to the pressure in front of him p a is called the compression ratio of an air compressor and is usually denoted as p to (p to = pb/p a). The compressor rotor is driven by a gas turbine. The compressed air flow is fed into one, two or more combustion chambers. In this case, in most cases, the air flow coming from the compressor is divided into two streams. The first flow is sent to the burners, where fuel (gas or liquid fuel) is also supplied. When fuel is burned, high-temperature combustion products are formed. The relatively cold air of the second flow is mixed with them in order to obtain gases (they are usually called working gases) with a temperature acceptable for parts of a gas turbine.
Working gases with pressure r s (r s < p b due to the hydraulic resistance of the combustion chamber) are fed into the flow path of the gas turbine, the principle of operation of which is no different from the principle of operation of the steam turbine (the only difference is that the gas turbine runs on fuel combustion products, and not on steam). In a gas turbine, the working gases expand to almost atmospheric pressure. p d, enter the outlet diffuser 14, and from it - either immediately into the chimney, or previously into any heat exchanger that uses the heat of the gas turbine exhaust gases.
Due to the expansion of gases in the gas turbine, the latter generates power. A very significant part of it (about half) is spent on the compressor drive, and the rest - on the electric generator drive. This is the net power of the gas turbine, which is indicated when it is marked.
To depict gas turbine diagrams, they use conventions, similar to those used for vocational schools.
There can be no simpler gas turbine, since it contains a minimum of necessary components that provide sequential processes of compression, heating and expansion of the working fluid: one compressor, one or more combustion chambers operating under the same conditions, and one gas turbine. Along with simple cycle gas turbines, there are complex cycle gas turbines that may contain several compressors, turbines and combustion chambers. In particular, GT-100-750, built in the USSR in the 70s, belong to this type of gas turbine.
It is made double. High pressure compressor on one shaft KVD and the high-pressure turbine driving it TVD; this shaft has a variable speed. The low pressure turbine is located on the second shaft TND, driving the low pressure compressor KND and electric generator EG; therefore, this shaft has a constant rotational speed of 50 s -1 . Air in the amount of 447 kg / s enters from the atmosphere into KND and is compressed in it to a pressure of approximately 430 kPa (4.3 atm) and then fed into the air cooler IN, where it is cooled with water from 176 to 35 °C. This reduces the work required to compress the air in the high pressure compressor. KVD(compression ratio p k = 6.3). From there, air enters the high pressure combustion chamber. KSVD and combustion products with a temperature of 750 ° C are sent to TVD. From TVD gases containing a significant amount of oxygen enter the low-pressure combustion chamber KSND, in which additional fuel is burned, and from it - into TND. Exhaust gases with a temperature of 390 ° C go either into the chimney or into a heat exchanger to use the heat of the exhaust gases.
GTU is not very economical due to the high temperature of the flue gases. The complication of the circuit makes it possible to increase its efficiency, but at the same time it requires an increase in capital investments and complicates operation.
The figure shows the GTU V94.3 from Siemens. Atmospheric air from the complex air-cleaning device (KVOU) enters the mine 4 , and from it - to the flow part 16 air compressor. Air is compressed in the compressor. The compression ratio in typical compressors is p k = 13-17, and thus the pressure in the gas turbine tract does not exceed 1.3-1.7 MPa (13-17 atm). This is another major difference between a gas turbine and a steam turbine, in which the steam pressure is 10-15 times greater than the gas pressure in the gas turbine. Small pressure working environment determines the small thickness of the walls of the buildings and the ease of their heating. This is what makes the gas turbine very maneuverable, i.e. capable of quick starts and stops. If it takes from 1 hour to several hours to start a steam turbine, depending on its initial temperature state, then the gas turbine can be put into operation in 10-15 minutes.
When compressed in a compressor, the air heats up. This heating can be estimated by a simple approximate relation:
$$T_a/T_b = \pi_k^(0.25)$$
wherein T b and T a- absolute air temperatures behind and before the compressor. If, for example, T a= 300 K, i.e. the ambient temperature is 27 ° C, and p k \u003d 16, then T b= 600 K and, consequently, the air is heated by
$$\Delta t = (600-273)-(300-273) = 300°C.$$
Thus, the air temperature behind the compressor is 300-350 °C. The air between the walls of the flame tube and the body of the combustion chamber moves to the burner, to which the fuel gas is supplied. Since the fuel must enter the combustion chamber, where the pressure is 1.3-1.7 MPa, the gas pressure must be high. To be able to control its flow into the combustion chamber, the gas pressure is approximately twice as high as the pressure in the chamber. If there is such pressure in the supply gas pipeline, then the gas is supplied to the combustion chamber directly from the gas distribution point (GDP). If the gas pressure is insufficient, then a booster gas compressor is installed between the hydraulic fracturing and the chamber.
The fuel gas consumption is only about 1-1.5% of the air flow from the compressor, so the creation of a highly economical booster gas compressor presents certain technical difficulties.
Inside the flame tube 10 high temperature combustion products are formed. After mixing secondary air at the outlet of the combustion chamber, it decreases somewhat, but nevertheless reaches 1350-1400 °C in typical modern gas turbines.
Hot gases from the combustion chamber enter the flow path 7 gas turbine. In it, gases expand to almost atmospheric pressure, since the space behind the gas turbine communicates either with a chimney or with a heat exchanger, the hydraulic resistance of which is small.
When gases expand in a gas turbine, power is generated on its shaft. This power is partially used to drive the air compressor, and its excess is used to drive the rotor 1 generator. One of the characteristic features of a gas turbine is that the compressor requires about half the power developed by the gas turbine. For example, in a gas turbine unit with a capacity of 180 MW (this is the net power) being created in Russia, the compressor capacity is 196 MW. This is one of the fundamental differences between a gas turbine and a steam turbine: in the latter, the power used to compress the feed water even up to a pressure of 23.5 MPa (240 atm) is only a few percent of the steam turbine power. This is due to the fact that water is a low compressible liquid, and air requires a lot of energy to compress.
In the first, rather rough approximation, the gas temperature behind the turbine can be estimated from a simple relationship similar to:
$$T_c/T_d = \pi_k^(0.25).$$
Therefore, if $\pi_k = 16$, and the temperature in front of the turbine T s\u003d 1400 ° С \u003d 1673 K, then the temperature behind it is approximately, K:
$$T_d=T_c/\pi_k^(0.25) = 1673/16^(0.25) = 836.$$
Thus, the gas temperature downstream of the gas turbine is quite high, and a significant amount of heat obtained from fuel combustion literally goes into the chimney. Therefore, during autonomous operation of a gas turbine, its efficiency is low: for typical gas turbines, it is 35-36%, i.e. significantly less than the efficiency of vocational schools. The matter, however, changes drastically when a heat exchanger is installed on the "tail" of the gas turbine unit (a network heater or a waste heat boiler for a combined cycle).
A diffuser is installed behind the gas turbine - a smoothly expanding channel, during the flow in which the velocity pressure of gases is partially converted into pressure. This makes it possible to have a pressure behind the gas turbine that is less than atmospheric pressure, which increases the efficiency of 1 kg of gases in the turbine and, consequently, increases its power.
Air compressor device. As already mentioned, an air compressor is a turbomachine, to the shaft of which power is supplied from a gas turbine; this power is transferred to the air flowing through the flow path of the compressor, as a result of which the air pressure rises up to the pressure in the combustion chamber.
The figure shows a gas turbine rotor placed in thrust bearings; in the foreground, the compressor rotor and stator elements are clearly visible.
From mine 4 air enters the channels formed by the rotary vanes 2 non-rotating inlet guide vane (VNA). The main task of the VNA is to inform the flow moving in the axial (or radial-axial) direction of rotational motion. VNA channels do not fundamentally differ from the nozzle channels of a steam turbine: they are confusing (tapering), and the flow in them accelerates, simultaneously acquiring a circumferential velocity component.
In modern gas turbines, the inlet guide vane is made rotatable. The need for a rotary VNA is caused by the desire to prevent a decrease in efficiency when the GTU load is reduced. The point is that the shafts of the compressor and the electric generator have the same rotational speed, equal to the frequency of the network. Therefore, if VNA is not used, then the amount of air supplied by the compressor to the combustion chamber is constant and does not depend on the turbine load. And you can change the power of the gas turbine only by changing the fuel flow into the combustion chamber. Therefore, with a decrease in fuel consumption and a constant amount of air supplied by the compressor, the temperature of the working gases decreases both before and after the gas turbine. This leads to a very significant reduction in the efficiency of the gas turbine. Rotation of the blades with a decrease in load around the axis 1 by 25 - 30° allows to narrow the flow sections of the VNA channels and reduce the air flow into the combustion chamber, maintaining a constant ratio between the air and fuel consumption. The installation of the inlet guide vane makes it possible to maintain the gas temperature in front of the gas turbine and behind it constant in the power range of approximately 100-80%.
The figure shows the VNA blade drive. A rotary lever is attached to the axes of each blade 2 , which through the lever 4 associated with a swivel ring 1 . If necessary, change the air flow ring 1 rotates with the help of rods and an electric motor with a gearbox; while turning all the levers at the same time 2 and, accordingly, the VNA blades 5 .
The air swirling with the help of VNA enters the 1st stage of the air compressor, which consists of two gratings: rotating and stationary. Both gratings, in contrast to turbine gratings, have expanding (diffuser) channels, i.e. inlet air passage area F 1 less than F 2 at the exit.
When air moves in such a channel, its speed decreases ( w 2 < w 1), and the pressure increases ( R 2 > R one). Unfortunately, to make the diffuser grill economical, i.e. so that the flow rate w 1 to the maximum degree would be converted into pressure, and not into heat, only possible with a small degree of compression R 2 /R 1 (usually 1.2 - 1.3), which leads to a large number of compressor stages (14 - 16 with a compressor compression ratio p k \u003d 13 - 16).
The figure shows the air flow in the compressor stage. From the input (fixed) rotary nozzle apparatus, the air exits at a speed c 1 (see the upper speed triangle), having the necessary circumferential twist (a 1< 90°). Если расположенная за ВНА вращающаяся (рабочая) решетка имеет скорость u 1 , then the relative speed of entering it w 1 will be equal to the difference of vectors c 1 and u 1 , and this difference will be greater than c 1 i.e. w 1 > c one . When moving in the channel, the air speed decreases to the value w 2 and it comes out at an angle b 2 determined by the inclination of the profiles. However, due to the rotation and supply of energy to the air from the rotor blades, its speed with 2 in absolute motion will be greater than c one . The blades of the fixed grid are installed so that the air inlet into the channel is shock-free. Since the channels of this grating are expanding, the velocity in it decreases to the value c" 1 , and the pressure increases from R 1 to R 2. The grid is designed so that c" 1 = c 1, a a "1 = a 1. Therefore, in the second stage and subsequent stages, the compression process will proceed in a similar way. In this case, the height of their gratings will decrease in accordance with the increased air density due to compression.
Sometimes the guide vanes of the first few stages of the compressor are made rotary in the same way as the VNA vanes. This makes it possible to expand the power range of the gas turbine, in which the temperature of the gases in front of the gas turbine and behind it remains unchanged. Accordingly, the economy also increases. The use of several rotary guide vanes allows you to work economically in the range of 100 - 50% of the power.
The last stage of the compressor is arranged in the same way as the previous ones, with the only difference that the task of the last guide vane 1 is not only to increase the pressure, but also to ensure the axial exit of the air flow. Air enters the annular outlet diffuser 23 where the pressure rises to its maximum value. With this pressure, air enters the combustion zone 9 .
Air is taken from the air compressor housing to cool the elements of the gas turbine. To do this, annular chambers are made in its body, communicating with the space behind the corresponding stage. The air from the chambers is removed by pipelines.
In addition, the compressor has so-called anti-surge valves and bypass pipes. 6 , bypassing air from the intermediate stages of the compressor into the outlet diffuser of the gas turbine when it is started and stopped. This eliminates the unstable operation of the compressor at low air flow rates (this phenomenon is called surge), which is expressed in intense vibration of the entire machine.
The creation of highly economical air compressors is an extremely complex task, which, unlike turbines, cannot be solved only by calculation and design. Since the compressor power is approximately equal to the power of the gas turbine, a deterioration in the efficiency of the compressor by 1% leads to a decrease in the efficiency of the entire gas turbine by 2-2.5%. Therefore, the creation of a good compressor is one of the key problems in the creation of gas turbines. Usually compressors are created by modeling (scaling) using a model compressor created by long experimental refinement.
Gas turbine combustion chambers are very diverse. Above is a gas turbine with two external chambers. The figure shows a GTU type 13E with a capacity of 140 MW from ABB with one remote combustion chamber, the device of which is similar to the device of the chamber shown in the figure. The air from the compressor from the annular diffuser enters the space between the chamber body and the flame tube and is then used for gas combustion and for cooling the flame tube.
The main disadvantage of remote combustion chambers is their large dimensions, which are clearly visible from the figure. To the right of the chamber is a gas turbine, to the left - a compressor. Three holes are visible from above in the body for accommodating anti-surge valves and then - the VNA drive. In modern gas turbines, built-in combustion chambers are mainly used: annular and tubular-annular.
The figure shows an integrated annular combustion chamber. The annular space for combustion is formed by the internal 17 and outdoor 11 fiery pipes. From the inside, the pipes are lined with special inserts 13 and 16 having a thermal barrier coating on the side facing the flame; on the opposite side, the inserts are ribbed, which improves their cooling by air entering through the annular gaps between the inserts inside the flame tube. Thus, the temperature of the flame tube is 750-800 °C in the combustion zone. The frontal microflare burner device of the chamber consists of several hundred burners 10 , to which gas is supplied from four collectors 5 -8 . Turning off the collectors in turn, you can change the power of the gas turbine.
The burner device is shown in the figure. From the collector, gas enters through drilling in the stem 3 to the inner cavity of the shoulder blades 6 swirler. The latter is a hollow radial straight blades that cause the air coming from the combustion chamber to twist and rotate around the axis of the rod. This rotating air vortex receives natural gas from the inner cavity of the swirler blades. 6 through small holes 7 . In this case, a homogeneous fuel-air mixture is formed, which emerges in the form of a swirling jet from the zone 5 . An annular rotating vortex ensures stable combustion of the gas.
The figure shows a tubular-annular combustion chamber GTE-180. Into the annular space 24 between the outlet of the air compressor and the inlet of the gas turbine using perforated cones 3 place 12 flame tubes 10 . The flame tube contains numerous holes with a diameter of 1 mm, arranged in annular rows at a distance of 6 mm between them; distance between rows of holes 23 mm. Through these openings, "cold" air enters from the outside, providing convective-film cooling and the temperature of the flame tube is not higher than 850 °C. A thermal barrier coating 0.4 mm thick is applied to the inner surface of the flame tube.
On the front plate 8 flame tube, a burner device is installed, consisting of a central pilot burner 6 igniting fuel at start-up using a candle 5 , and five main modules, one of which is shown in the figure. The module allows you to burn gas and diesel fuel. Gas through fitting 1 after filter 6 enters the annular fuel gas manifold 5 , and from it into cavities containing small holes (diameter 0.7 mm, step 8 mm). Through these holes, the gas enters the annular space. There are six tangential grooves in the walls of the module 9 , through which the main amount of air supplied for combustion from the air compressor enters. In the tangential slots, the air is twisted and, thus, inside the cavity 8 a rotating vortex is formed, moving towards the outlet of the burner. To the periphery of the vortex through the holes 3 gas enters, mixes with air, and the resulting homogeneous mixture exits the burner, where it ignites and burns. The combustion products enter the nozzle apparatus of the 1st stage of the gas turbine.
The gas turbine is the most complex element of the gas turbine, which is primarily due to the very high temperature of the working gases flowing through its flow path: the gas temperature in front of the turbine of 1350 ° C is currently considered “standard”, and leading companies, primarily General Electric, work on mastering the initial temperature of 1500 °C. Recall that the "standard" initial temperature for steam turbines is 540 °C, and in the future - a temperature of 600-620 °C.
The desire to increase the initial temperature is associated, first of all, with the gain in efficiency that it gives. This is clearly seen from the figure summarizing the achieved level of gas turbine construction: an increase in the initial temperature from 1100 to 1450 °C gives an increase in absolute efficiency from 32 to 40%, i.e. results in fuel savings of 25%. Of course, part of this savings is associated not only with an increase in temperature, but also with the improvement of other elements of the gas turbine, and the initial temperature is still the determining factor.
To ensure long-term operation of a gas turbine, a combination of two means is used. The first means is the use of heat-resistant materials for the most loaded parts that can resist the action of high mechanical loads and temperatures (primarily for nozzle and rotor blades). If steels (i.e. iron-based alloys) with a chromium content of 12-13% are used for steam turbine blades and some other elements, then nickel-based alloys (nimonic) are used for gas turbine blades, which are capable of and the required service life to withstand temperatures of 800-850 °C. Therefore, together with the first, a second means is used - cooling the hottest parts.
Most modern gas turbines are cooled using bleed air from various stages of an air compressor. Gas turbines are already in operation, which use water vapor for cooling, which is a better cooling agent than air. Cooling air after heating in the cooled part is discharged into the flow path of the gas turbine. Such a cooling system is called open. There are closed cooling systems in which the coolant heated in the part is sent to the refrigerator and then returned again to cool the part. Such a system is not only very complicated, but also requires the utilization of heat taken from the refrigerator.
The gas turbine cooling system is the most complex system in a gas turbine, which determines its service life. It ensures not only maintaining the permissible level of working and nozzle blades, but also body elements, disks carrying working blades, locking bearing seals where oil circulates, etc. This system is extremely branched and organized so that each cooled element receives cooling air of the parameters and in the amount necessary to maintain its optimum temperature. Excessive cooling of parts is just as harmful as insufficient, since it leads to increased costs of cooling air, the compression of which in the compressor consumes turbine power. In addition, increased air consumption for cooling leads to a decrease in the temperature of the gases behind the turbine, which has a very significant effect on the operation of the equipment installed behind the gas turbine (for example, a steam turbine unit operating as part of a steam turbine). Finally, the cooling system must ensure not only the required temperature level of the parts, but also the uniformity of their heating, which excludes the appearance of dangerous thermal stresses, the cyclic action of which leads to the appearance of cracks.
The figure shows an example of a typical gas turbine cooling circuit. The values of gas temperatures are given in rectangular frames. In front of the nozzle apparatus of the 1st stage 1 it reaches 1350 °C. Behind him, i.e. in front of the working grate of the 1st stage, it is 1130 °C. Even in front of the working blade of the last stage, it is at the level of 600 °C. Gases of this temperature wash the nozzle and working blades, and if they were not cooled, then their temperature would be equal to the temperature of the gases and their service life would be limited to several hours.
To cool the elements of a gas turbine, air is used that is taken from the compressor in that stage where its pressure is slightly higher than the pressure of the working gases in that zone of the gas turbine into which air is supplied. For example, for cooling the nozzle vanes of the 1st stage, cooling air in the amount of 4.5% of the air flow at the compressor inlet is taken from the compressor outlet diffuser, and for cooling the nozzle vanes of the last stage and the adjoining section of the housing - from the 5th stage of the compressor. Sometimes, to cool the hottest elements of a gas turbine, the air taken from the compressor outlet diffuser is first sent to an air cooler, where it is cooled (usually with water) to 180–200 °C and then sent for cooling. In this case, less air is required for cooling, but at the same time, the cost of an air cooler appears, the gas turbine becomes more complicated, and part of the heat removed by the cooling water is lost.
A gas turbine usually has 3-4 stages, i.e. 6-8 rims of gratings, and most often the blades of all rims are cooled, except for the working blades of the last stage. Air for cooling the nozzle vanes is supplied inside through their ends and discharged through numerous (600-700 holes with a diameter of 0.5-0.6 mm) holes located in the corresponding areas of the profile. Cooling air is supplied to the working blades through holes made in the ends of the shank.
In order to understand how cooled blades are arranged, it is necessary to consider at least in general terms the technology of their manufacture. Due to the extreme difficulty machining Nickel alloys for the production of blades are mainly used investment casting. To implement it, first, casting cores are made from ceramic-based materials using a special technology of molding and heat treatment. The casting core is an exact copy of the cavity inside the future blade, into which cooling air will flow and flow in the required direction. The casting core is placed in a mold, the internal cavity of which fully corresponds to the blade to be obtained. The resulting free space between the rod and the wall of the mold is filled with a heated low-melting mass (for example, plastic), which solidifies. The rod, together with the hardening mass enveloping it, repeating the external shape of the blade, is an investment model. It is placed in a mold, to which the nimonic melt is fed. The latter melts the plastic, takes its place, and as a result, a cast blade appears with an internal cavity filled with a rod. The rod is removed by etching with special chemical solutions. The obtained nozzle vanes practically do not require additional machining (except for the manufacture of numerous holes for the exit of cooling air). Working cast blades require processing of the shank with a special abrasive tool.
The technology described briefly is borrowed from aeronautical technology, where the temperatures achieved are much higher than in stationary steam turbines. The difficulty of mastering these technologies is associated with much larger blade sizes for stationary gas turbines, which grow in proportion to the gas flow rate, i.e. GTU power.
The use of so-called single-crystal blades, which are made from a single crystal, seems very promising. This is due to the fact that the presence of grain boundaries during a long stay at a high temperature leads to a deterioration in the properties of the metal.
The gas turbine rotor is a unique prefabricated structure. Before assembling individual discs 5 compressor and disc 7 gas turbine are bladed and balanced, end parts are manufactured 1 and 8 , spacer 11 and center pin 6 . Each of the discs has two annular collars, on which hirts (named after the inventor - Hirth) are made - strictly radial teeth of a triangular profile. Adjacent pieces have exactly the same collars with exactly the same hirts. With a good manufacturing quality of the hirt connection, the absolute centering of adjacent disks is ensured (this ensures the radiality of the hirts) and the repeatability of the assembly after disassembly of the rotor.
The rotor is assembled on a special stand, which is an elevator with an annular platform for assembly personnel, inside which assembly is carried out. First, the end part of the rotor is assembled on the thread 1 and tie rod 6 . The rod is placed vertically inside the annular platform and the disk of the 1st stage of the compressor is lowered on top of it with the help of a crane. The centering of the disk and the end part is carried out by hirts. Moving upwards on a special elevator, the installation staff disc by disc [first of the compressor, then the spacer, and then the turbine and the right end 8 ] collects the entire rotor. A nut is screwed onto the right end 9 , and a hydraulic device is installed on the remaining part of the threaded part of the tie rod, squeezing the discs and pulling the tie rod. After drawing the rod, the nut 9 is screwed up to the stop, and the hydraulic device is removed. The stretched rod securely tightens the discs together and turns the rotor into a single rigid structure. The assembled rotor is removed from the assembly stand, and it is ready for installation in the gas turbine.
The main advantage of the gas turbine is its compactness. Indeed, first of all, there is no steam boiler in the gas turbine - a structure that reaches a great height and requires a separate room for installation. This circumstance is connected, first of all, with the high pressure in the combustion chamber (1.2-2 MPa); in the boiler, combustion occurs at atmospheric pressure and, accordingly, the volume of hot gases formed is 12-20 times larger. Further, in a gas turbine, the gas expansion process takes place in a gas turbine consisting of only 3-5 stages, while a steam turbine with the same power consists of 3-4 cylinders containing 25-30 stages. Even taking into account both the combustion chamber and the air compressor, a 150 MW gas turbine has a length of 8-12 m, and the length of a steam turbine of the same power with a three-cylinder design is 1.5 times longer. At the same time, for the steam turbine, in addition to the boiler, it is necessary to provide for the installation of a condenser with circulation and condensate pumps, a regeneration system of 7-9 heaters, feed turbopumps (from one to three), and a deaerator. As a result, the gas turbine unit can be installed on a concrete base at the zero level of the machine hall, and the STU requires a frame foundation 9-16 m high with the steam turbine placed on the upper foundation slab and auxiliary equipment in the condensation room.
The compactness of the gas turbine allows it to be assembled at the turbine plant, delivered to the engine room by rail or road for installation on a simple foundation. So, in particular, gas turbines with built-in combustion chambers are transported. When transporting gas turbines with remote chambers, the latter are transported separately, but are easily and quickly attached to the compressor-gas turbine module using flanges. The steam turbine is supplied with numerous assemblies and parts, the installation of both itself and numerous auxiliary equipment and connections between them takes several times more time than a gas turbine.
GTU does not require cooling water. As a result, the gas turbine does not have a condenser and a system technical water supply with a pumping unit and a cooling tower (with circulating water supply). As a result, all this leads to the fact that the cost of 1 kW of installed capacity of a gas turbine power plant is much less. At the same time, the cost of the GTU itself (compressor + combustion chamber + gas turbine), due to its complexity, turns out to be 3-4 times more than the cost of a steam turbine of the same power.
An important advantage of a gas turbine is its high maneuverability, determined by a low pressure level (compared to the pressure in a steam turbine) and, consequently, easy heating and cooling without dangerous thermal stresses and deformations.
However, gas turbines also have significant drawbacks, of which, first of all, it should be noted that they are less economical than those of a steam power plant. The average efficiency of sufficiently good gas turbines is 37-38%, and for steam turbine power units - 42-43%. The ceiling for powerful power gas turbines, as it is currently seen, is an efficiency of 41-42% (and maybe even higher, given the large reserves for increasing the initial temperature). The lower efficiency of the gas turbine is associated with the high temperature of the exhaust gases.
Another disadvantage of gas turbines is the impossibility of using low-grade fuels in them, at least at present. It can only work well on gas or good liquid fuels such as diesel. Steam power units can operate on any fuel, including the poorest quality.
The low initial cost of thermal power plants with gas turbines and at the same time relatively low efficiency and high cost of the fuel used and maneuverability determine the main area for individual use of gas turbines: they should be used in power systems as peak or backup power sources operating several hours a day.
At the same time, the situation changes dramatically when the heat of the gas turbine exhaust gases is used in heating plants or in a combined (steam-and-gas) cycle.
Thermal turbine of constant action, in which the thermal energy of compressed and heated gas (usually fuel combustion products) is converted into mechanical rotational work on a shaft; is a structural element of a gas turbine engine.
Heating of compressed gas, as a rule, occurs in the combustion chamber. It is also possible to carry out heating in a nuclear reactor, etc. Gas turbines first appeared at the end of the 19th century. as a gas turbine engine and in terms of design, they approached a steam turbine. Structurally, a gas turbine is a series of orderly arranged stationary blade rims of the nozzle apparatus and rotating rims of the impeller, which as a result form a flow part. The turbine stage is a nozzle apparatus combined with an impeller. The stage consists of a stator, which includes stationary parts (housing, nozzle blades, shroud rings), and a rotor, which is a set of rotating parts (such as rotor blades, disks, shaft).
The classification of a gas turbine is carried out according to many design features: in the direction of the gas flow, the number of stages, the method of using the heat difference and the method of supplying gas to the impeller. In the direction of the gas flow, gas turbines can be distinguished axial (the most common) and radial, as well as diagonal and tangential. In axial gas turbines, the flow in the meridional section is transported mainly along the entire axis of the turbine; in radial turbines, on the contrary, it is perpendicular to the axis. Radial turbines are divided into centripetal and centrifugal. In a diagonal turbine, the gas flows at some angle to the axis of rotation of the turbine. The impeller of a tangential turbine has no blades; such turbines are used at very low gas flow rates, usually in measuring instruments. gas turbines There are single, double and multi-stage.
The number of stages is determined by many factors: the purpose of the turbine, its design scheme, the total power and developed by one stage, as well as the actuated pressure drop. According to the method of using the available heat difference, turbines with speed stages are distinguished, in which only the flow turns in the impeller, without pressure change (active turbines), and turbines with pressure stages, in which the pressure decreases both in the nozzle apparatus and on the rotor blades (jet turbines). In partial gas turbines, gas is supplied to the impeller along a part of the circumference of the nozzle apparatus or along its full circumference.
In a multistage turbine, the energy conversion process consists of a number of successive processes in individual stages. Compressed and heated gas is supplied to the interblade channels of the nozzle apparatus at an initial speed, where, in the process of expansion, a part of the available heat drop is converted into kinetic energy flow jets. Further expansion of the gas and the conversion of the heat drop into useful work occur in the interblade channels of the impeller. The gas flow, acting on the rotor blades, creates a torque on the main shaft of the turbine. In this case, the absolute velocity of the gas decreases. The lower this speed, the greater part of the gas energy is converted into mechanical work on the turbine shaft.
Efficiency characterizes the efficiency of gas turbines, which is the ratio of the work removed from the shaft to the available gas energy in front of the turbine. The effective efficiency of modern multistage turbines is quite high and reaches 92-94%.
The principle of operation of a gas turbine is as follows: gas is injected into the combustion chamber by a compressor, mixed with air, forms a fuel mixture and is ignited. The resulting combustion products with high temperature (900-1200 °C) pass through several rows of blades mounted on the turbine shaft and cause the turbine to rotate. The resulting mechanical energy of the shaft is transmitted through a gearbox to a generator that generates electricity.
Thermal energy gases leaving the turbine enter the heat exchanger. Also, instead of generating electricity, the mechanical energy of the turbine can be used to operate various pumps, compressors, etc. The most commonly used fuel for gas turbines is natural gas, although this cannot exclude the possibility of using other types of gaseous fuels. But at the same time, gas turbines are very capricious and place high demands on the quality of its preparation (certain mechanical inclusions, humidity are necessary).
The temperature of gases leaving the turbine is 450-550 °C. The quantitative ratio of thermal energy to electrical energy in gas turbines ranges from 1.5: 1 to 2.5: 1, which makes it possible to build cogeneration systems that differ in the type of coolant:
1) direct (direct) use of exhaust hot gases;
2) production of low or medium pressure steam (8-18 kg/cm2) in an external boiler;
3) production of hot water (better when the required temperature exceeds 140 °C);
4) production of high pressure steam.
A great contribution to the development of gas turbines was made by Soviet scientists B. S. Stechkin, G. S. Zhiritsky, N. R. Briling, V. V. Uvarov, K. V. Kholshchevikov, I. I. Kirillov, and others. the creation of gas turbines for stationary and mobile gas turbine plants was achieved by foreign companies (the Swiss Brown-Boveri, in which the famous Slovak scientist A. Stodola worked, and Sulzer, the American General Electric, etc.).
AT further development gas turbines depends on the possibility of increasing the gas temperature in front of the turbine. This is due to the creation of new heat-resistant materials and reliable cooling systems for rotor blades with a significant improvement in the flow path, etc.
Thanks to the widespread transition in the 1990s. natural gas as the main fuel for power generation, gas turbines have occupied a significant segment of the market. Despite the fact that the maximum efficiency of the equipment is achieved at capacities from 5 MW and higher (up to 300 MW), some manufacturers produce models in the 1-5 MW range.
Gas turbines are used in aviation and power plants.
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A turbine is an engine in which the potential energy of a compressible fluid is converted into kinetic energy in the blade apparatus, and the latter in the impellers into mechanical work transmitted to a continuously rotating shaft.
Steam turbines by their design represent a heat engine that is constantly in operation. During operation, superheated or saturated water vapor enters the flow path and, due to its expansion, forces the rotor to rotate. Rotation occurs as a result of the steam flow acting on the blade apparatus.
The steam turbine is part of the steam turbine design, which is designed to generate energy. There are also installations that, in addition to electricity, can generate thermal energy - the steam that has passed through the steam blades enters the network water heaters. This type of turbine is called industrial-cogeneration or cogeneration type of turbines. In the first case, steam extraction is provided for industrial purposes in the turbine. Complete with a generator, a steam turbine is a turbine unit.
Steam turbine types
Turbines are divided, depending on the direction in which the steam moves, into radial and axial turbines. The steam flow in radial turbines is directed perpendicular to the axis. Steam turbines can be one-, two- and three-case. The steam turbine is equipped with a variety of technical devices that prevent the ingress of ambient air into the casing. These are a variety of seals, which are supplied with water vapor in a small amount.
A safety regulator is located on the front section of the shaft, designed to turn off the steam supply when the turbine speed increases.
Characteristics of the main parameters nominal values
· Turbine rated power- the maximum power that the turbine must develop for a long time at the terminals of the electric generator, with normal values of the main parameters or when they change within the limits specified by the industry and state standards. A controlled steam extraction turbine can develop power above its nominal power if this is in accordance with the strength conditions of its parts.
· Turbine economic power- the power at which the turbine operates with the greatest efficiency. Depending on the parameters of live steam and the purpose of the turbine, the rated power can be equal to the economic power or more by 10-25%.
· Nominal temperature of regenerative feed water heating- the temperature of the feed water downstream of the last heater in the direction of the water.
· Rated cooling water temperature- the temperature of the cooling water at the inlet to the condenser.
gas turbine(fr. turbine from lat. turbo swirl, rotation) is a continuous heat engine, in the blade apparatus of which the energy of compressed and heated gas is converted into mechanical work on the shaft. It consists of a rotor (blades fixed on disks) and a stator (guide vanes fixed in the housing).
Gas having a high temperature and pressure enters through the turbine nozzle apparatus into the low pressure area behind the nozzle part, simultaneously expanding and accelerating. Further, the gas flow enters the turbine blades, giving them part of its kinetic energy and imparting torque to the blades. The rotor blades transmit torque through the turbine discs to the shaft. Beneficial features gas turbine: a gas turbine, for example, drives a generator located on the same shaft with it, which is the useful work of a gas turbine.
Gas turbines are used as part of gas turbine engines (used for transport) and gas turbine units (used at thermal power plants as part of stationary GTUs, CCGTs). Gas turbines are described by the Brayton thermodynamic cycle, in which air is first adiabatically compressed, then burned at constant pressure, and then adiabatically expanded back to starting pressure.
Types of gas turbines
- Aircraft and jet engines
- Auxiliary power unit
- Industrial gas turbines for electricity production
- Turboshaft engines
- Radial gas turbines
- Microturbines
Mechanically, gas turbines can be considerably simpler than reciprocating internal combustion engines. Simple turbines may have one moving part: shaft/compressor/turbine/alternate rotor assembly (see image above), not including the fuel system.
More complex turbines (those used in modern jet engines) may have multiple shafts (coils), hundreds of turbine blades, moving stator blades, and an extensive system of complex piping, combustion chambers, and heat exchangers.
As a general rule, the smaller the motor, the higher the speed of the shaft(s) required to maintain the maximum linear speed of the blades. Max Speed turbine blades determines the maximum pressure that can be achieved, resulting in maximum power, regardless of engine size. The jet engine rotates at about 10,000 rpm and the micro-turbine at about 100,000 rpm.
Thermal turbine of constant action, in which the thermal energy of compressed and heated gas (usually fuel combustion products) is converted into mechanical rotational work on a shaft; is a structural element of a gas turbine engine.
Heating of compressed gas, as a rule, occurs in the combustion chamber. It is also possible to carry out heating in a nuclear reactor, etc. Gas turbines first appeared at the end of the 19th century. as a gas turbine engine and in terms of design, they approached a steam turbine. Structurally, a gas turbine is a series of orderly arranged stationary blade rims of the nozzle apparatus and rotating rims of the impeller, which as a result form a flow part. The turbine stage is a nozzle apparatus combined with an impeller. The stage consists of a stator, which includes stationary parts (housing, nozzle blades, shroud rings), and a rotor, which is a set of rotating parts (such as rotor blades, disks, shaft).
The classification of a gas turbine is carried out according to many design features: in the direction of the gas flow, the number of stages, the method of using the heat difference and the method of supplying gas to the impeller. In the direction of the gas flow, gas turbines can be distinguished axial (the most common) and radial, as well as diagonal and tangential. In axial gas turbines, the flow in the meridional section is transported mainly along the entire axis of the turbine; in radial turbines, on the contrary, it is perpendicular to the axis. Radial turbines are divided into centripetal and centrifugal. In a diagonal turbine, the gas flows at some angle to the axis of rotation of the turbine. The impeller of a tangential turbine has no blades; such turbines are used at very low gas flow rates, usually in measuring instruments. Gas turbines are single, double and multi-stage.
The number of stages is determined by many factors: the purpose of the turbine, its design scheme, the total power and developed by one stage, as well as the actuated pressure drop. According to the method of using the available heat difference, turbines with speed stages are distinguished, in which only the flow turns in the impeller, without pressure change (active turbines), and turbines with pressure stages, in which the pressure decreases both in the nozzle apparatus and on the rotor blades (jet turbines). In partial gas turbines, gas is supplied to the impeller along a part of the circumference of the nozzle apparatus or along its full circumference.
In a multistage turbine, the energy conversion process consists of a number of successive processes in individual stages. Compressed and heated gas is supplied to the interblade channels of the nozzle apparatus at an initial speed, where, in the process of expansion, a part of the available heat drop is converted into the kinetic energy of the outflow jet. Further expansion of the gas and the conversion of the heat drop into useful work occur in the interblade channels of the impeller. The gas flow, acting on the rotor blades, creates a torque on the main shaft of the turbine. In this case, the absolute velocity of the gas decreases. The lower this speed, the greater part of the gas energy is converted into mechanical work on the turbine shaft.
Efficiency characterizes the efficiency of gas turbines, which is the ratio of the work removed from the shaft to the available gas energy in front of the turbine. The effective efficiency of modern multistage turbines is quite high and reaches 92-94%.
The principle of operation of a gas turbine is as follows: gas is injected into the combustion chamber by a compressor, mixed with air, forms a fuel mixture and is ignited. The resulting combustion products with high temperature (900-1200 °C) pass through several rows of blades mounted on the turbine shaft and cause the turbine to rotate. The resulting mechanical energy of the shaft is transmitted through a gearbox to a generator that generates electricity.
Thermal energy gases leaving the turbine enter the heat exchanger. Also, instead of generating electricity, the mechanical energy of the turbine can be used to operate various pumps, compressors, etc. The most commonly used fuel for gas turbines is natural gas, although this cannot exclude the possibility of using other types of gaseous fuels. But at the same time, gas turbines are very capricious and place high demands on the quality of its preparation (certain mechanical inclusions, humidity are necessary).
The temperature of gases leaving the turbine is 450-550 °C. The quantitative ratio of thermal energy to electrical energy in gas turbines ranges from 1.5: 1 to 2.5: 1, which makes it possible to build cogeneration systems that differ in the type of coolant:
1) direct (direct) use of exhaust hot gases;
2) production of low or medium pressure steam (8-18 kg/cm2) in an external boiler;
3) production of hot water (better when the required temperature exceeds 140 °C);
4) production of high pressure steam.
A great contribution to the development of gas turbines was made by Soviet scientists B. S. Stechkin, G. S. Zhiritsky, N. R. Briling, V. V. Uvarov, K. V. Kholshchevikov, I. I. Kirillov, and others. the creation of gas turbines for stationary and mobile gas turbine plants was achieved by foreign companies (the Swiss Brown-Boveri, in which the famous Slovak scientist A. Stodola worked, and Sulzer, the American General Electric, etc.).
In the future, the development of gas turbines depends on the possibility of increasing the gas temperature in front of the turbine. This is due to the creation of new heat-resistant materials and reliable cooling systems for rotor blades with a significant improvement in the flow path, etc.
Thanks to the widespread transition in the 1990s. natural gas as the main fuel for power generation, gas turbines have occupied a significant segment of the market. Despite the fact that the maximum efficiency of the equipment is achieved at capacities from 5 MW and higher (up to 300 MW), some manufacturers produce models in the 1-5 MW range.
Gas turbines are used in aviation and power plants.
- Previous: GAS ANALYZER
- Following: GAS ENGINE