Gas turbine units (GTP) are a single, relatively compact unit in which a power turbine and a generator work in pairs. The system has become widespread in the so-called small-scale power industry. Great for power and heat supply of large enterprises, remote settlements and other consumers. As a rule, gas turbines operate on liquid fuel or gas.

On the cutting edge of progress

In increasing the energy capacity of power plants, the leading role is transferred to gas turbine units and their further evolution - combined-cycle plants (CCGT). Thus, at US power plants since the early 1990s, more than 60% of the commissioned and modernized capacities are already gas turbines and combined cycle plants, and in some countries individual years their share reached 90%.

Simple GTUs are also being built in large numbers. The gas turbine plant - mobile, economical to operate and easy to repair - proved to be the optimal solution to cover peak loads. At the turn of the century (1999-2000), the total capacity of gas turbine plants reached 120,000 MW. For comparison: in the 1980s, the total capacity of systems of this type was 8,000-10,000 MW. A significant part of the gas turbines (more than 60%) were intended for operation as part of large binary combined cycle plants with an average power of about 350 MW.

History reference

The theoretical foundations for the use of combined cycle technologies were studied in sufficient detail in our country in the early 60s. Already at that time, it became clear that the general path for the development of thermal power engineering is connected precisely with combined cycle technologies. However, their successful implementation required reliable and highly efficient gas turbine units.

It is the significant progress in gas turbine construction that determined the modern qualitative leap in thermal power engineering. A number of foreign firms have successfully solved the problem of creating efficient stationary gas turbines at a time when domestic leading leading organizations in a command economy were promoting the least promising steam turbine technologies (STP).

If in the 60s of gas turbine installations it was at the level of 24-32%, then in the late 80s the best stationary gas turbine power plants already had an efficiency factor (in autonomous use) of 36-37%. This made it possible to create CCGTs on their basis, the efficiency of which reached 50%. By the beginning of the new century, this indicator was equal to 40%, and in combination with combined-cycle plants - even 60%.

Comparison of steam turbine and combined cycle plants

In combined-cycle plants based on gas turbines, the immediate and real prospect was to obtain an efficiency of 65% or more. At the same time, for steam turbine plants (developed in the USSR), only in the event of a successful solution of a number of complex scientific problems associated with the generation and use of supercritical steam, one can hope for an efficiency of no more than 46-49%. Thus, in terms of efficiency, steam turbine systems are hopelessly inferior to combined cycle systems.

Steam turbine power plants are also significantly inferior in terms of cost and construction time. In 2005, in the world energy market, the price of 1 kW for a CCGT unit with a capacity of 200 MW or more was $500-600/kW. For CCGTs of smaller capacities, the cost was in the range of $600-900/kW. Powerful gas turbine plants correspond to values ​​of 200-250 $/kW. With a decrease in unit power, their price increases, but usually does not exceed $ 500 / kW. These values ​​are many times less cost kilowatt of electric power of steam turbine systems. For example, the price of an installed kilowatt for condensing steam turbine power plants ranges from 2000-3000 $/kW.

The installation includes three basic units: a combustion chamber and an air compressor. Moreover, all units are housed in a prefabricated single building. The compressor and turbine rotors are rigidly connected to each other, supported by bearings.

Combustion chambers (for example, 14 pieces) are placed around the compressor, each in its own separate housing. The inlet pipe is used to enter the air compressor, from gas turbine air escapes through the exhaust pipe. The gas turbine body is based on powerful supports placed symmetrically on a single frame.

Principle of operation

Most gas turbine installations use the principle of continuous combustion, or an open cycle:

• First, the working fluid (air) is pumped at atmospheric pressure by an appropriate compressor.
• The air is then compressed to more pressure and sent to the combustion chamber.
• It is supplied with fuel, which burns at a constant pressure, providing a constant heat supply. Due to the combustion of fuel, the temperature of the working fluid increases.
• Further, the working fluid (now it is already a gas, which is a mixture of air and combustion products) enters the gas turbine, where, expanding to atmospheric pressure, performs useful work (turns the turbine that generates electricity).
• After the turbine, the gases are discharged into the atmosphere, through which the working cycle is closed.
• The difference between the operation of the turbine and the compressor is perceived by an electric generator located on a common shaft with the turbine and compressor.

Intermittent combustion plants

Unlike the previous design, intermittent combustion plants use two valves instead of one.

• The compressor forces air into the combustion chamber through the first valve while the second valve is closed.
• When the pressure in the combustion chamber rises, the first valve is closed. As a result, the volume of the chamber is closed.
• When the valves are closed, fuel is burned in the chamber, naturally, its combustion occurs at a constant volume. As a result, the pressure of the working fluid further increases.
• Next, the second valve is opened, and the working fluid enters the gas turbine. In this case, the pressure in front of the turbine will gradually decrease. When it approaches atmospheric, the second valve should be closed, and the first one should be opened and the sequence of actions repeated.

Turning to practical implementation of this or that thermodynamic cycle, designers have to face many insurmountable technical obstacles. Most characteristic example: at a steam humidity of more than 8-12%, the losses in the flow path increase sharply, dynamic loads increase, and erosion occurs. This ultimately leads to the destruction of the flow path of the turbine.

As a result of these restrictions in the energy sector (for obtaining work), only two basic thermodynamic Rankine cycles and the Brayton cycle are widely used so far. Most power plants are based on a combination of elements of these cycles.

The Rankine cycle is used for working bodies that, in the process of implementing the cycle, perform phase transition, steam power plants operate according to this cycle. For working fluids that cannot be condensed into real conditions and which we call gases, use the Brayton cycle. Gas turbine plants and internal combustion engines operate according to this cycle.

Fuel used

The vast majority of gas turbines are designed to operate on natural gas. Sometimes liquid fuel is used in low power systems (less often - medium, very rarely - high power). A new trend is the transition of compact gas turbine systems to the use of solid combustible materials (coal, less often peat and wood). These trends are related to the fact that gas is a valuable technological raw material for chemical industry where its use is often more cost-effective than in the energy sector. The production of gas turbine plants capable of operating efficiently on solid fuel is actively gaining momentum.

The difference between an internal combustion engine and a gas turbine

The fundamental difference between gas turbine complexes is as follows. In an internal combustion engine, the processes of air compression, fuel combustion and expansion of combustion products occur within one structural element called the engine cylinder. In gas turbines, these processes are separated into separate structural units:

• compression is carried out in the compressor;
• combustion of fuel, respectively, in a special chamber;
• expansion is carried out in a gas turbine.

As a result, structurally, gas turbines and internal combustion engines have little similarity, although they operate according to similar thermodynamic cycles.

Conclusion

With the development of small-scale power generation and the increase in its efficiency, GTP and STP systems occupy an increasing share in the overall energy system of the world. Accordingly, the operator of gas turbine installations is increasingly in demand. Following Western partners, a number Russian manufacturers mastered the issue economically efficient installations gas turbine type. The first new generation combined-cycle power plant in the Russian Federation was the Severo-Zapadnaya CHPP in St. Petersburg.

A modern gas turbine plant (GTU) 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. The turbine, in which the gas expands to atmospheric pressure, converts the potential energy of the gas compressed and heated to a high temperature into the kinetic energy of the rotation of the turbine rotor. The turbine drives an electric generator that converts the kinetic energy of rotation of the generator rotor into electric current. The electric generator consists of a stator, in the electric windings of which current is generated, and a rotor, which is an electromagnet, which is powered by an exciter.

Unlike steam turbine plants (STP), where steam is the working fluid, GTPs operate on the products of fuel combustion. In addition, in contrast to the GTP, the STP does not include a boiler, more precisely, the boiler is considered as a separate heat source. A steam turbine plant cannot operate without a boiler as a physical object. In gas turbines, on the contrary, the combustion chamber is its integral part. In this sense, the GTU is self-sufficient. According to the method of heat supply at constant pressure p= const and at a constant volume v= const. All modern gas turbines operate with heat input at p= const. There are open (open) and closed (closed) gas turbine circuits

The simplest scheme of an open gas turbine in symbols, as well as its thermodynamic cycle, are shown in Figure 1. Air from the atmosphere enters the air compressor inlet (point 1 ), which is a rotary turbomachine with a flow path consisting of rotating and fixed gratings. The ratio of the pressure behind the compressor to the pressure in front of it is called the compression ratio of the air compressor and is usually referred to as. The compressor rotor is driven by a gas turbine. The compressed air flow is supplied to one, two or more combustion chambers (point 2 ). 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 burner devices, where fuel (gas or liquid fuel) is also supplied, due to the combustion of which at a constant pressure p= const high temperature combustion products are formed. They are mixed with relatively cold air the second flow in order to obtain gases (they are called working gases) with a temperature acceptable for parts of a gas turbine.

Figure 1 - The simplest scheme of an open gas turbine and its thermodynamic cycle

Working gases with pressure due to the hydraulic resistance of the combustion chamber) are fed into the flow path of the gas turbine (point 3 ), where they expand almost to atmospheric pressure (point 4 ). Then they enter the outlet diffuser , from where - either directly into the chimney, which will cause significant heat losses, or previously into any heat exchanger that uses the heat of the gas turbine exhaust gases.

In a closed circuit (Fig. 2), surface heaters of the working fluid are used instead of the combustion chamber, and the gas (for example, helium) exhausted in the turbine is cooled in special coolers to the lowest temperature, after which it enters the compressor. The thermodynamic cycle of this scheme is similar to that of an open gas turbine.

Due to the expansion of gases in the gas turbine, the latter generates power. A significant part of it is spent on the compressor drive, and the rest is spent on the electric generator drive. This part is called the net power of the gas turbine and is indicated when it is marked.

In real gas turbines, all ongoing processes are accompanied by work losses in the compressor and turbine, as well as pressure losses along the gas turbine path. Given these losses, the real cycle differs from the ideal one. The composition of a real gas turbine includes a combustion chamber (heater of the working fluid in a closed circuit), a gas turbine, a compressor, a starting engine, heat exchangers for various purposes(regenerative heaters, intermediate heaters in turbines) and various auxiliary equipment, as well as an electric generator, if the purpose of the gas turbine is the production electrical energy. Turbine, compressor and generator are placed on the same shaft. The starting motor is connected with a release clutch. In the simplest gas turbines, approximately 70% of the power developed by the turbine is used to drive the compressor, and 30% to drive the generator. The degree of pressure increase in the compressor = 6 ... 7, the efficiency of the installation is 24 ... 27%, the temperature in front of the turbine is 750 ... 800 °C. The range of initial temperatures in front of the gas turbine in the gas turbine is 750 ... 1150 ° C, therefore, based on the strength conditions, the plant elements operating at high temperatures are made of high increased reliability provided for air cooling.

Figure 2 - The simplest scheme of a closed gas turbine

The exhaust gases of the turbine have a high temperature, so their removal to the environment in the open circuit of the gas turbine leads to significant energy losses. In order to increase the efficiency of the installation, regenerative heating of compressed air by the exhaust gases of the turbine is used. This increases the degree of use of the heat of the fuel burned in the combustion chamber and the energy efficiency of the installation.

In an ideal gas turbine with regeneration, the scheme and cycle of which is shown in Figure 3, the turbine exhaust gases can be cooled to a temperature equal to the temperature of the air behind the compressor, i.e. up to , and the air compressed by the compressor can be heated to a temperature corresponding to the temperature at the turbine exhaust, i.e. before. In a real installation, the air in the regenerative heat exchanger will be heated to a temperature that is lower, and the exhaust gases will be cooled in the same heat exchanger to a temperature that is higher than the value usually equal to 60 ... 80 ° C in open circuits. Real gas turbines operating in an open circuit at an initial temperature of 750 ... 850 ° C have a degree of regeneration, and an effective efficiency of 26.5 ... 30%.

Figure 3 - Scheme and cycle of gas turbine with regeneration

Gas turbines that provide combined generation of electrical and thermal energy are called cogeneration plants. Thermal energy is generated by using the heat of gases leaving the turbine at high temperature to heat water and produce steam. Heating water used for heating and domestic needs with turbine exhaust gases is the simplest way to increase the thermal efficiency of a gas turbine.

Gaseous and light liquid fuels are used in gas turbines. When using liquid fuels of heavy grades containing harmful impurities, a special fuel preparation system is needed to prevent corrosion of turbine parts under the influence of sulfur and vanadium compounds contained in heavy fuels. The problem of using solid fuel in gas turbines is at the stage of intensive pilot development.

The turbine start-up technology to a large extent depends on the temperature state of the equipment in front of it. There are starts from cold, warm and hot states. If the turbine temperature does not exceed 150 °C, then it is considered that the start-up was made from a cold state. For powerful power units, it takes up to 90 hours to cool down to this temperature. Starts from a hot state correspond to a turbine temperature of 420-450 ° C and higher (reached in 6-10 hours). The uncooled state is intermediate. Any lengthening of the start-up leads to additional fuel costs. Therefore, the start-up must be carried out quickly, but not at the expense of reliability. Turbine start is prohibited:

in the event of a malfunction of the main instruments showing the course of the thermal process in the turbine and its mechanical condition (tachometers, thermometers, pressure gauges, etc.);

with a faulty lubrication system that provides lubrication of the bearings;

in case of malfunction of protection and regulation systems;

with a faulty turning device.

To start the GTU, it is necessary to use the starting device (PU) to rotate the rotor of the turbocharger, to supply air from the compressor simultaneously with fuel to the combustion chamber for its ignition and to perform further operations to start the GTU. Various means can be used as a starting device: an electric motor, a steam or gas (air) turbine, an internal combustion engine. For large power turbines, as a rule, GTU's own electric generator is used as a PU, which turns the GTU rotor to a speed equal to 0.2 - 0.3 nominal. During the start-up period, the compressor control vanes must be covered to reduce air consumption. Anti-surge valves are open at start-up. Fuel is supplied to the combustion chamber, and the air-fuel mixture formed in the mixing device of the combustion chamber is ignited using an ignition device (plasma igniter). Fuel consumption is increased by opening the fuel valve. This causes an increase in the temperature of the gases in front of the turbine, the turbine power and the rotor speed. At a certain gas temperature in front of the turbine and a certain speed, the power of the gas turbine is equal to the power consumed by the air compressor. In this state, after a slight additional increase in fuel consumption, the starting device is turned off, and the gas turbine goes into self-propelled mode. With a further increase in fuel consumption, the turbine unit is turned by the gas turbine until the nominal speed is reached, then the electric generator is synchronized with the network and connected to the network. Thus, the unit is put into idle mode. During start-up, the anti-surge valves are closed, and the adjustable guide vanes are set to the positions prescribed by the start-up program.

In the process of loading the gas turbine to the rated power, the fuel consumption increases by opening the control valve, the installation angles of the adjustable compressor guide vanes are changed according to the corresponding program, the air consumption increases to the nominal value. GTU operation in general case consists of starting, operating with electrical and thermal load, and stopping. The simplest is to work at a constant load. The main task of the personnel servicing the turbine plant, during normal operation, is to provide the specified electrical and thermal power with full guarantee reliable operation and the greatest possible savings.

The operating modes of gas turbines can be divided into stationary and variable.

The stationary mode corresponds to the operation of the turbine at some fixed load. It can flow both at nominal and at partial load. Until recently, this regime was the main one for gas turbines. The turbine stopped several times a year due to malfunctions or scheduled repairs.

The variable modes of the gas turbine are determined by the following reasons in relation to the gas turbine. The first reason is the need to change the power generated by the gas turbine if the power consumed, for example, by an electric generator has changed due to a change in the electrical load of consumers connected to the generator. If the gas turbine drives an electric generator connected in parallel with other power producers, i.e. working for common network(power system), then it is necessary to change the power of this gas turbine in case of a change in the total power consumption in the system. The second reason is a change in atmospheric conditions: pressure and especially temperature of the atmospheric air taken in by the compressor. The most difficult non-stationary mode is the GTP start-up, which includes numerous operations before the rotor kick. Non-stationary modes include abrupt changes in load (shedding or surge), as well as turbine shutdown (unloading, disconnection from the network, rotor run-out for cooling).

Thus, for gas turbines, the main task of control is to provide the necessary power, and for power gas turbines, the constancy of the rotational speed of the driven electric generator. Variable modes of operation of the gas turbine should be carried out in such a way that the efficiency in each mode is as high as possible. The GTU mode is controlled by acting on the control fuel valves that supply fuel directly to the combustion chamber, which leads to a low inertia of the process of heat supply to the working fluid in the combustion chamber. Gas turbines are sensitive to changes in atmospheric conditions. For them, there is a risk of compressor surge. To start the gas turbine, it is necessary that surge be excluded in all possible operating modes. To start the gas turbine, it is necessary to first spin the rotor using a starting device.

Modern large gas turbines use automated control systems that perform the following functions:

– automatic remote control of GTU start-up, loading and shutdown;

– regulation of such parameters as the rotational speed of the turbine unit with a given degree of unevenness, the gas temperature before and after the turbine, the active load of the electric generator, the compressor operation mode at the required distance from the surge boundary;

– protection of the gas turbine, namely shutdown and shutdown in emergency situations, of which the most serious are such as an unacceptable increase in gas temperatures before and after the gas turbine, an unacceptable increase in gas temperatures before and after the gas turbine, an unacceptable increase in gas temperatures before the gas turbine and behind it, an unacceptable increase in the frequency of the rotor, an unacceptable drop in oil pressure for lubricating bearings, an unacceptable axial shift of the rotor, flame extinction in the combustion chamber, approaching the compressor surge limit, an unacceptable increase in the vibration velocity of the rotor journals and bearing housings.

An event consisting in a malfunction of the gas turbine is called a failure. To maintain high reliability and non-failure operation, the equipment undergoes maintenance, current, medium or major repairs. During current and medium repairs, damaged parts and assemblies are replaced or restored, and during major repairs, a complete restoration of working capacity is carried out. During normal operation of the gas turbine, careful maintenance and regular checks of the protection and control systems are necessary, carried out by the watch personnel and the engineer responsible for the operation of this system. The reliability of its operation depends on the thoroughness of the inspection of the accessible components of the control and protection systems, the comparison of the current indicators of the devices with the previous ones, the performance of all checks and operations provided for by the instructions drawn up taking into account the requirements of the turbine manufacturers of the operating technology rules (PTE) and guidelines for testing and tests. Special attention the inspection should focus on potential sources of oil leaks. It is necessary to monitor the position of nuts, locking parts and other fasteners on rods, spools, since these parts operate in vibration conditions that cause them to unscrew and malfunction. It is necessary to monitor the mechanical condition of all accessible components: cam mechanisms, their shafts, bearings, springs, etc. Particular attention should be paid to vibrations of the control elements, which can cause the drive stems to break due to fatigue. It is necessary to monitor pressure changes and pulsations in the main oil pipelines of control and protection systems: oil supply lines for lubrication, in impulse lines, protection lines and cavities of servomotors. A change in these pressures indicates abnormalities in the control systems, oil supply: leakage of valves, seals of pistons and servomotor rods, clogging of shims. Spool pulsations are caused by abnormal operation of the impeller, contamination of oil lines, solid particles between the spools and bushings, increased air content in the oil, and other reasons.

The first attention of the operating personnel should be paid to exclude the possibility of turbine acceleration when the electric generator is disconnected from the network, which is ensured by a sufficient density of shut-off and control valves and check valves on pipelines. The check is carried out when the turbine is stopped at least once a year, and also without fail when starting after installation. For the turbine to work properly, the oil tank must function properly, ensuring the long-term preservation of the oil, the separation of air, sludge and solid particles from it. The oil level in the tank should be checked once per shift. At the same time, it is necessary to monitor the serviceability of the signaling of the minimum allowable level and the difference in levels in the dirty and clean compartments of the oil tank. Reserve and emergency oil pumps and devices for their automatic activation should be regularly checked at a frequency of 2 times a month. The quality of oil coolers is checked by the pressure difference at the inlet and outlet of oil and cooling water and by heating the cooling water and cooling the oil. The chemical laboratory of the power plant should regularly analyze the operating oil in order to regenerate and replace it in time.

When observing a running turbine, it is necessary to pay attention primarily to the relative elongation of the rotor and its axial shift. When installing and repairing the turbine, the rotor in the housing is installed so that under operating conditions, when these parts warm up, there are sufficiently small gaps between them, but excluding rubbing, otherwise a severe accident may occur.

The unloading of the turbine is carried out by gradually closing the control valves (using the control mechanism). Particular attention should be paid to the relative reduction of the rotor, and if, despite all the measures taken, the reduction approaches a dangerous limit, it is necessary to stop unloading, and possibly even increase the load. The load is usually reduced to 15-20% of the nominal, after which the gas supply to the turbine is stopped. From that moment on, it is rotated by a generator with the frequency of the electrical network. In the short time specified in the instructions (usually a few minutes), you need to make sure that the stop, control valves on the extraction lines are closed, and the wattmeter shows negative power (power consumption from the network). After that, you can turn off the generator from the network. After stopping the turbine rotor, it is necessary to immediately turn on the barring device in order to avoid its thermal deflection. The oil supply must not be turned off. During the first 8 hours, the rotor rotates continuously, and then it is rotated periodically by 180°. The emergency shutdown of the turbine unit is carried out by immediately stopping the supply of the working fluid.

A stopped turbine requires careful maintenance. The greatest danger during idle time for the turbine and some other elements of the turbine installation is parking corrosion, the main cause of which is the simultaneous presence of moisture and air. To prevent this from happening, it is necessary to open the valves that ensure the communication of parts with the atmosphere. When the turbine is stopped, the long-term reserve is taken additional measures. It is disconnected from all pipelines with plugs. The turbine shaft is additionally sealed with a cord, oil is pumped through the bearings at least once a week to create a protective layer of oil on the bearing journals, and the rotor is rotated by a barring device for several revolutions. Turbine conservation is the most effective way to combat parking corrosion.

The GTU is assembled at the turbine plant after individual parts and assemblies have been manufactured in its workshops. Unlike a steam turbine, there is no testing after assembly at the GTU plant. As a result, several separately transported units leave the turbine plant for the TPP installation site: a turbo group (compressor and turbine), two combustion chambers, an oil tank with equipment installed on it, a compressor inlet pipe, and an outlet diffuser. All parts are closed with plugs. Unlike steam turbine s, gas turbines are placed at thermal power plants not on a frame foundation, but directly on a concrete base installed at the zero level of the turbine hall. The compressor inlet shaft is connected by means of an air box to the KVOU, where thorough air filtration takes place, which excludes wear of the compressor flow path, clogging of the cooling channels in the rotor blades and other troubles. KVOU is placed on the roof of the building, saving the area of ​​the building. The rotor of the electric generator is connected to the outlet end of the compressor shaft, and a transitional diffuser is connected to the outlet diffuser of the gas turbine unit, which directs gases to the waste heat boiler.

GTU is a universal engine with various purposes. They are most widely used in aviation and long-distance gas supply. In stationary power engineering, gas turbines for various purposes are used at thermal power plants. Peak gas turbines operate during periods of maximum electrical energy consumption. Standby gas turbines provide for the own needs of TPPs during the period when the main equipment is not in operation. The industries where the use of gas turbines creates great advantages include blast furnace production, where the gas turbine, being the drive of the blower that supplies air to the blast furnace, uses blast-furnace gas, which is a by-product of the blast furnace. In railway transport, gas turbine locomotives (gas turbine locomotives) have received some use on long lines. A number of gas turbines are operated in the merchant and navy, mainly on light and high-speed patrol vessels, where special meaning has compactness and small mass of the engine. The gas-turbine car is in the stage of research of experimental models. The best experimental engines have reached the level of modern gasoline automobile engines in terms of efficiency with less weight.

GAS TURBINE PLANTS (GTU)

GTU workflow. In modern gas turbines, a combustion cycle is used at p = const (Fig. 6.5).

The GTP usually includes a combustion chamber, a gas turbine, an air compressor, heat exchangers for various purposes (air coolers, oil coolers of the lubrication system, regenerative heat exchangers) and auxiliary devices (oil pumps, water supply elements, etc.).

The working body of the gas turbine is the products of combustion of fuel, which is used as natural gas, well-purified artificial gases (blast furnace, coke oven, generator) and special gas turbine liquid fuel (processed diesel engine and solar oil).

The working mixture is prepared in the combustion chamber. The fire volume of the chamber (Fig. 20.9) is divided into a combustion zone, where fuel is burned at a temperature of about 2000 ° C, and a mixing zone, where air is mixed with the combustion products to reduce their temperature to 750-1090 ° C in stationary turbines and up to 1400 °С - in aviation turbines.

The principle of operation of gas and steam turbines is the same, but the design of the flow path of gas turbines is much simpler. They operate on a relatively small available heat drop and therefore have a small number of steps.

Due to the high temperature of the combustion products, the details of the flow path of turbines (nozzles, rotor blades, disks, shafts) are made of alloyed high-quality steels. For reliable operation, most turbines provide for intensive cooling of the most loaded parts of the casing and rotor.

In real conditions, all processes in the GTP are non-equilibrium, which is associated with work losses in the turbine and compressor, as well as with aerodynamic drag in the GTP duct. On fig. 20.10, the actual compression process in the compressor is shown by line 1-2, and the expansion process in the turbine is shown by line 3-4. Points 2a and 4a mark the state of the working fluid, respectively, at the end of equilibrium adiabatic compression and expansion, point O - environmental parameters. Due to pressure losses in the compressor suction path (line 01), the compression process starts at point 1.

Thus, a lot of work is spent on compressing air in a real cycle, and when expanding gas in a turbine, less work is obtained compared to perfect cycle. The cycle efficiency is lower. The greater the degree of pressure increase π (i.e., the higher p 2), the greater the sum of these losses compared to useful work. At a certain value of π (it is the higher, the greater the Tg and the internal relative efficiency of the turbine and compressor, i.e., the less the loss in them), the operation of the turbine can become equal to the work expended on the compressor drive, and the useful work is zero.

Therefore, the greatest efficiency of the real cycle, in contrast to the ideal one, is achieved at a certain (optimal) degree of pressure increase, and each value of Tz has its own π opt (Fig. 20.11). The efficiency of the simplest gas turbines does not exceed 14-18%, and in order to increase it, gas turbines are performed with several stages of heat supply and intermediate cooling of compressed air, as well as with regenerative heating of compressed air by exhaust gases after the turbine, thereby bringing the real cycle closer to the Carnot cycle.

GTP with waste heat recovery. The heat of gases leaving the gas turbine can be used to produce steam and hot water in conventional heat exchangers. Thus, GT-25-700 LMZ units are equipped with heaters that heat water in the heating system up to 150-160 °C.

However, comparatively high level coefficient of excess air in the gas turbine allows you to burn enough a large number of additional fuel in the environment of combustion products. As a result, gases with a sufficiently high temperature exit from the additional combustion chamber after the gas turbine, suitable for obtaining steam of energy parameters in a steam generator specially installed for this purpose. At the Karmanovskaya GRES, a boiler for a unit with an electric power of 500 MW is being built according to this scheme.

Application of GTU. In recent years, gas turbines have been widely used in various fields: in transport, in the energy sector, for driving stationary installations, etc.

Power gas turbines. A gas turbine is smaller and lighter than a steam turbine, so it warms up to operating temperatures much faster during start-up. The combustion chamber is put into operation almost instantly, in contrast to a steam boiler, which requires slow long-term (many hours and even tens of hours) heating in order to avoid an accident due to uneven thermal elongations, especially a massive drum up to 1.5 m in diameter, up to 15 m long. m, with a wall thickness of more than 100 mm.

Therefore, gas turbines are primarily used to cover peak loads and as an emergency reserve for the own needs of large power systems, when it is necessary to put the unit into operation very quickly. The lower efficiency of the gas turbine compared to the PSU does not play a role in this case, since the units operate for short periods of time. Such gas turbines are characterized by frequent starts (up to 1000 per year) with a relatively small number of hours of use (from 100 to 1500 hours per year). The range of unit capacities of such gas turbines is from 1 to 100 MW.

Gas turbines are also used to drive an electric generator and generate electricity in mobile installations (for example, on ships). Such gas turbines usually operate in the load range of 30-110% of the nominal load, with frequent starts and stops. The unit power of such gas turbines ranges from tens of kilowatts to 10 MW. The rapid development of nuclear power plants with reactors cooled, for example, by helium, opens up the prospect of using single-loop GTUs operating in a closed cycle (the working fluid does not leave the plant).

A specific group of power gas turbine units is made up of installations operating in the technological schemes of chemical, oil refining, metallurgical and other plants (energy technology). They operate in the base load mode and are most often designed to drive a compressor that provides the process with compressed air or gas due to the expansion energy of the gases generated as a result of the process itself.

Drive gas turbines are widely used to drive centrifugal blowers of natural gas at compressor stations of main pipelines, as well as pumps for transporting oil and oil products and blowers in combined cycle plants. The useful power of such gas turbines ranges from 2 to 30 MW.

Transport gas turbines are widely used as the main and afterburner engines of aircraft (turbojet and turboprop) and ships of the navy. This is due to the possibility of obtaining record figures in terms of specific power and overall dimensions compared to other types of engines, despite somewhat overestimated fuel consumption. Gas turbines are very promising as locomotive engines, where their small size and lack of water requirements are especially valuable. Transport gas turbines operate in a wide range of loads and are suitable for short-term forcing.

The unit power of the gas turbine does not yet exceed 100 MW, and the efficiency of the plant is 27-37%. With an increase in the initial gas temperature to 1200 °C, the capacity of the gas turbine will be increased to 200 MW and the efficiency of the plant will be up to 38-40%.

Gas turbine plant is a universal modular device that combines: an electric generator, a gearbox, a gas turbine and a control unit. Also, there is optional equipment, such as: compressor, starting device, heat exchanger.

A gas turbine plant is able to operate not only in the mode of generating electricity, but also to produce joint production of electrical energy with thermal energy.

Based on what the customer wishes, the production of gas turbine plants can be carried out with a universal system, when the exhaust gases are used to produce steam or hot water.

Diagram of a gas turbine plant

This equipment has two main blocks: a power-type turbine and a generator. They are placed in one block.

The scheme of a gas turbine plant is very simple: the gas formed after the fuel burns out begins to contribute to the rotation of the blades of the turbine itself.

Thus, a torque is generated. This leads to the generation of electrical energy. Outgoing gases convert water into steam in the waste heat boiler. Gas in this case works with a double benefit.

Cycles of gas turbine plants

This equipment can be made with different cycles work.

Closed cycle gas turbine plant implies the following: gas is supplied through the compressor to the heater (heat exchanger), where heat is supplied from external sources. It is then fed into a gas turbine where it is expanded. This results in less gas pressure.

After that, the gases enter the refrigeration chamber. Heat is removed from there to external environment. The gas is then sent to the compressor. The cycle then restarts. Today, similar equipment is almost never used in the energy sector.

The production of gas turbine plants of this type is carried out in large sizes. Also, there are losses and low efficiency value, which directly depends on the temperature indicators of the gas itself before the turbine.

Open loop gas turbine plant are used much more frequently. In this equipment, the compressor supplies air from the environment, which, when high pressure enters a specially designed combustion chamber. This is where fuel is burned.

The temperature of organic fuel reaches 2000 degrees. Doing so may damage the metal of the camera itself. To prevent this, a lot of air is supplied to it than it needs (about 5 times). This significantly reduces the temperature of the gas itself and protects the metal.

Scheme of a gas turbine plant with an open cycle

The scheme of a gas turbine plant with an open cycle is as follows: fuel is supplied to gas burner(nozzle) located inside the heat-resistant pipe. Air is also injected there, after which the combustion process of the fuel is carried out.

There are several such pipes and they are arranged concentrically. Air enters the gaps between them, creating a protective barrier and preventing burnout.

Thanks to pipes and airflow, the chamber is in reliable protection from overheating. At the same time, the temperature of the gases at the outlet is lower than that of the fuel itself.

The metal can withstand 1000 - 1300°C. It is these chamber gas temperature indicators that are present in modern gas turbine apparatuses.

Differences between gas turbine plants of closed and open type

The main difference between gas turbine plants of a closed type and an open one is based on the fact that in the first case there is no combustion chamber, but a heater is used. Here the air is heated, while it does not participate in the process of heat generation itself.

Such equipment is performed exclusively with combustion, at a constant pressure value. Organic or nuclear fuel is used here.

Nuclear units use not air, but helium, carbon dioxide or nitrogen. The advantages of such equipment include the ability to use the heat of atomic decay, which is released in nuclear reactors.

Due to the high concentration of the “working fluid”, it became possible to achieve high readings of the heat transfer coefficient inside the regenerator itself. This also contributes to an increase in the level of regeneration at small sizes. However, such equipment has not yet been widely used.

Power gas turbine installations

Gas turbine power plants are also called "gas turbine mini power plants". They are used as permanent, emergency or backup sources of supply for cities and hard-to-reach areas.

Gas turbine power plants are used in many industries:

• oil refining;
• gas production;
• metalworking;
• forestry and woodworking;
• metallurgical;
• Agriculture;
• waste disposal, etc.

What types of fuels are used in gas turbines?

This equipment is capable of operating on different types of fuel.

Gas turbines use the following types of fuel:

• natural gas;
• kerosene;
• biogas;
• diesel fuel;
• petroleum gas of associated type;
• coke, wood, mine gas and other types.

Many of these turbines are also capable of operating on low-calorie fuels containing small amounts of methane (on the order of 3 percent).

Other features of gas turbine plants

Distinctive features of gas turbine plants:

• Minor harm caused environment. This is low oil consumption. The ability to work on the waste of the production itself. The emission of harmful substances into the atmosphere is 25 ppm.
• Small dimensions and weight. This allows you to locate this equipment in small areas, which saves money.
• Insignificant level of noise, and also vibrations. This indicator is in the range of 80 - 85 dBA.
• The ability of gas turbine equipment to operate on various fuels makes it possible to use it in almost any industry. At the same time, the enterprise will be able to choose an economically profitable type of fuel, based on the specifics of its activities.
• Continuous operation with minimal load. This also applies to the idle mode.
• For one minute, this equipment is capable of withstanding an excess of the rated current by 150 percent. And within 2 hours - 110%.
• With a three-phase symmetrical "short circuit", the generator system is able to withstand for 10 seconds about 300 percent of the rated continuous current.
• No water cooling.
• High operational reliability.
• Long service life (about 200,000 hours).
• Use of equipment in any climatic conditions.
• Moderate construction cost and low costs during the work itself, repairs and maintenance.

The electrical power of gas turbine equipment ranges from tens of kW to several MW. The maximum efficiency is achieved if the gas turbine plant operates in the mode of simultaneous production of heat and electricity (cogeneration).

Due to the receipt of such inexpensive energy, it becomes possible to quickly pay off this kind of equipment. The power plant and the exhaust gas recovery boiler contribute to a more efficient use of fuel.

With gas turbine machines, the task of obtaining high power has been greatly simplified. And when all the thermal features of gas-type turbines are fulfilled, the value of a large electrical efficiency fades into the background. If we take into account great importance temperature of exhaust gases of gas turbine equipment, it is possible to carry out a combination of the use of gas and steam turbines.

Given engineering solution helps enterprises to significantly increase productivity from the use of fuel and increase electrical efficiency to a mark of 57 - 59 percent. This method is very good, but it leads to financial costs and complexity of the equipment design. Therefore, it is often used only by large industries.

The ratio of produced electrical energy to thermal energy in a gas turbine plant is 1 to 2. Thus, for example, if a gas turbine plant has a capacity of 10 megawatts, then it is capable of generating 20 MW of thermal energy. To convert Megawatts to gigacalories, you must use a special coefficient, which is equal to 1.163.

Depending on what exactly the customer needs, gas turbine equipment can be additionally equipped with water heating and steam boilers. This allows you to get steam with different pressures, which will be used to solve various production problems. Also, it allows you to get hot water, which will have a standard temperature.

During the combined operation of two types of energy, it is possible to obtain an increase in the fuel utilization factor (FUFR) of a gas turbine thermal power plant of up to 90 percent.

When using gas turbine plants in the form of power-type equipment for powerful thermal power plants, as well as mini-CHPs, you will get a justified economic solution. This is due to the fact that today almost all power plants operate on gas. They have a very low unit cost for the consumer in terms of construction and low costs during subsequent use.

Superfluous, and even free, thermal energy allows you to set up ventilation (air conditioning) without any electricity costs industrial premises. And this can be done at any time of the year. The coolant cooled in this way can be used for various industrial needs. This type of technology is called "trigeneration".

Gas turbine plants at the exhibition

The central complex of the Expocentre Central Exhibition Complex is a very comfortable site, which is located in Moscow, near the metro stations Vystavochnaya and Delovoy Tsentr.

Thanks to the high professionalism of the employees of this complex and their companies, the ideal logistics for the creation of exhibitions and the rapid processing of customs documents, loading, unloading and installation work. Also, the continuous operation of the installations during its presentation is supported.

The exhibition pavilion area of ​​the Expocentre Central Exhibition Complex has all the necessary equipment for holding such large-scale events. Thanks to the open area, you can easily present your innovative or energy-intensive equipment that works in real time.

The annual international exhibition "Electro" is a large-scale event in Russia and the CIS. It will demonstrate electrical equipment for power engineering, electrical engineering, industrial lighting equipment, as well as enterprise automation.

At the exhibition "Electro", you can see modern tendencies industries, from the generation of electrical energy to its final use. Thanks to innovative technologies and high-quality equipment, your enterprise can get a "sip fresh air and be reborn.

Such modernization of production cannot be ignored by consumers of your services and goods. Such equipment can significantly reduce the cost and costs of electrical energy.

Every year this event is attended by manufacturers from more than twenty countries of the world. You can visit it too. To do this, you should fill out the appropriate application on our website or call us. At our exhibition you will be able to present your new product samples, utility models and inventions, new original products and much more related to energy and electrical equipment.

The conditions for participation in the exhibition at the Expocentre Fairgrounds are very transparent. Any right holder, if he finds various violations of his rights to intellectual property, can count on legal assistance. This allows you to increase the responsibility and discretion of each exhibitor during the presentation of their product.

GAS TURBINE PLANT

INTRODUCTION

At the first stages of the development of gas turbines, two types of combustion chambers were used for fuel combustion. In the combustion chamber of the first type, fuel and oxidizer (air) were supplied continuously, their combustion was also maintained continuously, and the pressure did not change. In the combustion chamber, the second type of fuel and oxidizer (air) were supplied in portions. The mixture was ignited and burned in a closed volume, and then the combustion products entered the turbine. In such a combustion chamber, the temperature and pressure are not constant: they increase sharply at the moment of fuel combustion.

Over time, the undoubted advantages of the first type of combustion chambers were revealed. Therefore, in modern gas turbines, fuel is in most cases burned at a constant pressure in the combustion chamber.

The first gas turbines had low efficiency, since gas turbines and compressors were imperfect. With the improvement of these units, the efficiency of gas turbine plants increased, and they became competitive with respect to other types of heat engines.

At present, gas turbine units are the main type of engines used in aviation, due to the simplicity of their design, the ability to quickly gain load, high power with low weight, and the possibility of full automation of control. An aircraft powered by a gas turbine engine first flew in 1941.

In the energy sector, gas turbines operate mainly at a time when electricity consumption increases sharply, i.e. during load peaks. Although the efficiency of gas turbines is lower than that of steam turbine plants (at a power of 20–100 MW, the efficiency of gas turbines reaches 20–30%), their use in peak mode turns out to be beneficial, since start-up takes much less time.

In some peak gas turbines, aircraft turbojet engines that have served their time in aviation are used as gas sources for the turbine that rotates the electric generator. Along with internal combustion engines, gas turbines are used as the main engines in mobile power plants.

In technological processes of oil refinery and chemical industries combustible waste is used as fuel for gas turbines.

Gas turbine plants are also widely used in railway, sea, river and road transport. So, on high-speed hydrofoils and hovercraft, GTUs are engines. On heavy vehicles, they can be used as both the main and auxiliary engine, designed to supply air to the main internal combustion engine and run on its exhaust gases.

In addition, gas turbines serve as a drive for natural gas blowers on main gas pipelines, backup electric generators for fire pumps.

! The main direction in which the gas turbine industry is developing is to increase the efficiency of gas turbines by increasing the temperature and pressure of the gas in front of the gas turbine. For this purpose, complex cooling systems are developed for the most stressed parts of turbines or new, high-strength materials are used - heat-resistant nickel-based, ceramics, etc.

Gas turbine plants are usually reliable and easy to operate, subject to strict observance of established rules and operating modes, deviation from which can cause destruction of turbines, compressor failure, explosions in combustion chambers, etc.

MAIN ELEMENTS OF GAS TURBINE PLANT

GENERAL INFORMATION ABOUT GAS TURBINE PLANT

Gas turbine engine(GTE) - one of the types of heat engine in which the gas is compressed and heated, and then the energy of the compressed and heated gas is converted into mechanical work on the shaft of the gas turbine. A gas turbine plant consists of three main elements: a gas turbine, combustion chambers and an air compressor.

The transformation of heat into work is carried out in several GTE units (Fig. 1)

Rice. 1. Scheme of a gas turbine engine:

TN - fuel pump; CS - combustion chamber; K - compressor; T - turbine; EG - electric generator.

Fuel and compressed air are supplied to the combustion chamber by a fuel pump after the compressor. The fuel is mixed with air, which serves as an oxidizing agent, ignited and burned. Pure products of combustion are also mixed with air so that the temperature of the gas obtained after mixing does not exceed a predetermined value. From the combustion chambers, the gas enters the gas turbine, which is designed to convert its potential energy into mechanical work. When doing work, the gas cools and its pressure decreases to atmospheric pressure. From the gas turbine, gas is released into the environment.

Clean air enters the compressor from the atmosphere. In the compressor, its pressure increases and the temperature rises. The compressor drive has to take a significant part of the turbine power.

Gas turbine plants operating according to this scheme are called open circuit plants. Most modern gas turbines operate according to this scheme.

Rice. 2. Gas turbine engine cycle.

Replacing fuel combustion with isobaric heat input (line 2-3 in Fig. 2), and cooling of combustion products emitted into the atmosphere with isobaric heat removal (line 1-4), we get the GTE cycle:

1-2 - compression of the working fluid from atmospheric pressure to pressure in the engine;

2-3 - combustion in the chamber;

3-4 - the process of adiabatic expansion of the working fluid;

4-1 - exhaust gases are released into the atmosphere

In addition, apply closed gas turbines(Fig. 3). Closed gas turbines also have compressor 3 and turbine 2 . Heat source 1 is used instead of the combustion chamber , in which heat is transferred to the working fluid without mixing with the fuel. Air, carbon dioxide, mercury vapor or other gases can be used as a working fluid.

The working fluid, the pressure of which is increased in the compressor, heats up in the heat source 1 and enters the turbine 2 , in which he gives his energy. After the turbine, the gas enters the intermediate heat exchanger 5 (regenerator), in which it heats the air, and then cools in the cooler 4 , enters the compressor 3, and the cycle is repeated. As a source of heat, special boilers can be used to heat the working body with the energy of the burned fuel or nuclear reactors.

Rice. 3. Scheme of a gas turbine engine operating in a closed cycle: 1 - surface heater; 2 - turbine; 3 - compressor; 4 - cooler; 5 - regenerator; 6 - air accumulator; 7 - auxiliary compressor.