RU2330977C1 - Gas turbine plant output control method - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to heat engineering. The method of the gas turbine plant (GTP) output control consists in that a waste-heat boiler is used in GTP with air bleeding to drive the free turbine, the said boiler being heated by gas generator exhaust gases. The waste-heat boiler increases the total flow rate of working medium not varying the GTP output range and, thus, the blade compressor rpm range reduces to 0.8...1.0.

EFFECT: higher efficiency of gas turbine plant in throttling conditions approximating to that in the rated operating conditions.

7 cl, 6 dwg

Description

The invention relates to a power system.

Known gas turbine engines (Theory, calculation and design of aircraft engines and power plants. Edited by V. A. Sosunov, V. M. Chepkin. M: Publishing House of the Moscow Aviation Institute, 2003, p. 18, Fig. 1.1) , including turboshaft (ibid., p. 387, fig. 11.3), as well as gas turbine units (ibid., p. 658, fig. 22.2). The indicated engines and gas turbine units (GTU) use the Brighton thermodynamic cycle, the efficiency of which is determined by the degree of pressure increase (hereinafter, the compression ratio) of the working fluid (ibid., P.30, Fig. 11.12). When changing the operation mode of a gas turbine engine (power control), the compression ratio of the working fluid changes - it decreases with a decrease in the rotor speed of the engine rotor (ibid., P. 247, Fig. 8.10). In this regard, gas turbine engines and gas turbine engines are characterized by significant changes in the coefficient of performance (COP) depending on the engine operating mode (for example, if in rated modes the efficiency is more than 30%, then in throttle modes close to "low gas" less 10%). This circumstance is a serious drawback for engines and power plants operating in a wide range of capacities.

Known gas turbine engines with air extraction behind the compressor (Patent GB 1201526, IPC F02K 3/02, 1970), in which compressed air is used to drive a free turbine.

Combined-cycle plants are known in which steam is introduced into a gas turbine to boost power and increase the efficiency (Copyright certificate No. 168962, USSR, 1962).

A known power plant (Patent RU No. 2278708, IPC F01K 21/04, 2006), in which air is taken from a compressor of a gas generator and steam generated in a waste heat boiler is used to drive a free turbine. The power plant is single-mode.

A known method of regulating the power of gas turbines, which consists in simultaneously changing the rotor speed and fuel consumption through the main combustion chamber (Theory and calculation of jet engines. Edited by S.M. Shlyakhtenko, M .: Mechanical Engineering, 1987, p.363 .. .364). The specified method is the closest analogue of the claimed method.

The objective of the invention is to increase the efficiency of gas turbine plants at throttle (low) operating modes.

The reason for lowering the efficiency of gas turbine plants in throttle modes is the presence of a rigid connection, established by the characteristic of the axial compressor, between the flow rate of the working fluid and the degree of compression: the stronger the flow rate of the working fluid is, the stronger the degree of compression changes (Theory, design and design of aircraft engines and energy installations, edited by V. A. Sosunov and V. M. Chepkin, Moscow: MAI Publishing House, 2003, p. 247, Fig. 8.10). The presence of this connection leads to the fact that when controlling power (reducing air flow), the degree of compression of the working fluid is significantly reduced and, accordingly, the efficiency of the installation is reduced.

The essence of the invention lies in the fact that in a gas turbine part of the working fluid (air) is replaced by water vapor, which reduces the required air flow (by the amount of steam flow) and, thereby, reduces its effect on the degree of increase in pressure of the working fluid and, accordingly, the efficiency of the installation . To do this, in the gas-turbine gas turbine circuit with air sampling for driving a free turbine (Patent GB 1201526, IPC F02K 3/02, 1970), an additional compressor (a waste heat boiler) is introduced parallel to the main (blade) compressor, heated by the gases leaving the compressor drive turbine, the degree of compression of water vapor in which corresponds to the degree of compression of gas in the main compressor. As a result, the required air flow through a free turbine is reduced. To ensure the possibility of efficient control of gas turbine power at its maximum power, the degree of pressure increase is more than 15, and the gas temperature in front of the turbine is more than 1400 K.

The efficiency of the method (increasing the efficiency of the installation) can be increased if the working fluid at the entrance to a free turbine is heated with gases leaving the compressor drive turbine (regeneration of the heat of the exhaust gases).

The effectiveness of the method (expanding the range of capacities) can be increased if the steam flow rate is regulated.

The effectiveness of the method (reduction of water and thermal energy losses with exhaust gases) can be improved if the steam-air mixture leaving the free turbine is mixed with feed water.

The effectiveness of the method (increasing the efficiency of the installation) can be increased if a low pressure section is made in the waste heat boiler — an economizer.

The effectiveness of the method (increasing the efficiency of the installation) can be improved if the area of the passage sections of the nozzle apparatus of the turbines is regulated.

Figure 1 ... 6 shows gas-dynamic schemes and characteristics illustrating the possibilities of implementing the method:

figure 1 shows a diagram of the CCGT;

figure 2 shows a diagram of the CCGT;

figure 3 shows the dependence of efficiency on the operating mode of the CCGT unit;

figure 4 shows the dependence of the gas temperature in front of the compressor drive turbine on the operating mode of the CCGT unit;

figure 5 shows the characteristic of the compressor with a working line in the CCGT system;

figure 6 shows the dependence of the efficiency of the turbines and compressor on the operating mode of the CCGT unit.

The implementation of the method is illustrated by the example of CCGT, depicted in figure 1.

The CCGT consists of a gas generator, which includes: a blade compressor 1, a combustion chamber 2, a compressor drive turbine 3, a recovery boiler 4 filled with water and heated by gases leaving the compressor drive turbine 1, a mixing chamber 5, into which air is supplied taken from the compressor 1, and the steam leaving the waste heat boiler 4, a free turbine 6, located behind the mixing chamber 5, the generator 7.

The method is implemented as follows.

In the design (maximum) mode, the air taken after the compressor 1 of the gas generator is supplied to the mixing chamber 5. There, steam generated in the recovery boiler 4 is supplied. From the mixing chamber, the mixture of air and steam is fed into a free turbine that performs mechanical work.

With a decrease in the fuel supply to the combustion chamber 2, the air and steam flow rates entering the mixing chamber 5 decrease. The decrease in these costs is associated with a decrease in the capacity of the turbine 3 and the waste heat boiler 4 as a result of a decrease in the gas temperature in front of the turbine. The decrease in air flow, as in the known method, is accompanied by a decrease in the rotor speed and, accordingly, a decrease in the degree of compression of the working fluid (air and steam). However, the indicated decrease in the rotational speed (compression ratio of the working fluid) is smaller than in the known method, since the magnitude of the change in air flow (by the amount of steam flow) is smaller. Accordingly, higher compression ratios of the working fluid allow higher efficiency.

To ensure the required efficiency in the proposed method (more than 30%) at the CCGT maximum power mode, the degree of pressure increase in the axial compressor should be at least 15, and the gas temperature in front of the turbine at least 1400 K.

The effectiveness of the method can be increased:

1. If the steam-air mixture before being fed into a free turbine, heat with hot gases leaving the compressor drive turbine in the gas-air heat exchanger 8 (Fig.2).

2. If a low pressure section is made in the waste heat boiler, an economizer 9 (Fig. 2), where cold water will flow before it enters the waste heat boiler. The principle of operation of the economizer 9 is based on the difference in boiling points in the economizer ~ 100 ° С (pressure corresponds to atmospheric) and the waste heat boiler ~ 200 ° С (pressure corresponds to the air pressure behind the compressor). As a result of this difference, the temperature of the exhaust gas decreases by ~ 100 degrees, which increases the steam output from the recovery boiler.

3. If the flow rate of steam entering the mixing chamber, adjust the surge damper 10 (figure 2). In this case, the operational range of CCGT power changes can be expanded by lowering the rotor speed to values less than 80% of the maximum speed.

4. If the steam-air mixture leaving the free turbine is mixed with feed water in the contact type condenser 11 (Fig. 2), followed by cooling of the condensate in the gas-liquid heat exchanger 12. In this case, the steam in the steam-air mixture can be reused in the heat cycle PSU.

5. If you adjust the area of the flow areas of the nozzle apparatus of the turbine. In this case, the effect of using steam can be enhanced by the effect of the redistribution of air between the CCGT turbines (circuits), which will further narrow the range of variation in the degree of compression of the working fluid and, accordingly, bring the efficiency in throttle modes even closer to the efficiency in nominal modes.

6. If part of the steam (up to 20%) generated in the waste heat boiler is fed to the compressor turbine inlet. In this case, the power of the compressor drive turbine can be increased without increasing the gas temperature in front of the turbine, which will allow to redistribute the air flow in favor of a free turbine, increasing its power, and therefore, the CCGT efficiency.

где Ne_max - максимальная мощность ПГУ. Расчетный режим обозначен точкой PP. Разрыв характеристик вызван переходным процессом, происходящим в момент закрытия (открытия) противопомпажной заслонки 10 (фиг.2).Figure 3 ... 6 shows the dependencies that characterize the example of CCGT (figure 2) the effectiveness of the claimed method. CCP operation mode is set by relative power

where Ne _max is the maximum power of CCGT. The design mode is indicated by the point PP. The gap in characteristics is caused by a transition process occurring at the moment of closing (opening) of the anti-surge damper 10 (Fig. 2).

As can be seen from figure 3, the efficiency of the CCGT unit in the operating range of capacities has a rather gentle characteristic for gas turbine units, namely: with moderate parameters of the working process (figure 4, figure 5), the CCGT efficiency is 0.34 ... 0 42. In warm-up modes (without steam supply), the efficiency of the CCGT unit is reduced to 0.25 ... 0.2 (Fig. 3). Changing the efficiency of blade machines (compressor, compressor turbine, free turbine) is shown in Fig.6.

The proposed method allows to solve current economic problems:

1. In the railway transport. CCP (Fig.2) with a capacity of 1 ... 1.5 MW can be used as a power plant in rolling stock, where a wide range of operating modes is required. In addition, the heat removed in the heat exchanger 12 can be used to heat and supply hot water to the train cars.

2. In water (sea) transport. CCP (Fig.2) with a capacity of 1 ... 10 MW can be used as a ship power plant. In this case, the selection of heat in the heat exchanger 12 can be carried out by using the cold resource of river (sea) water.

3. In the housing and communal services of the country. CCGT (figure 2) with a capacity of 1 ... 2 MW is an autonomous source of energy supply (electricity, hot water, hot air) of a residential complex (multi-storey building), designed for 3000 ... 5000 residents. The use of autonomous sources of energy supply (figure 2) allows for significant cost savings associated with the transportation of energy. The fact is that the transportation of energy (thermal, electric) requires the construction of communications (thermal and electric networks) and is accompanied by significant energy losses, while there are no such drawbacks in the transportation of fuel.

Claims (7)

1. A method of controlling the power of a gas turbine installation, which consists in simultaneously changing the rotor speed and fuel consumption in the combustion chamber of the installation, provided that the air compressed in the compressor simultaneously enters the combustion chamber of the installation located in front of the compressor drive turbine and the mixing chamber, located in front of the free turbine, the gas leaving the compressor drive turbine heats the water in the recovery boiler to a boiling point at a pressure corresponding to the air pressure and behind the compressor, characterized in that the steam generated in the waste heat boiler enters the aforementioned mixing chamber, the degree of increase in air pressure in the compressor at maximum power is more than 15, and the gas temperature in front of the compressor drive turbine at maximum power is more than 1400 K . 2. The method of controlling the power of a gas turbine installation according to claim 1, characterized in that the mixture of air and steam coming from the mixing chamber into a free turbine is heated by gases leaving the compressor drive turbine. 3. The method of regulating the power of a gas turbine installation according to claim 1, characterized in that the flow rate of steam entering the mixing chamber is regulated. 4. The method of regulating the power of a gas turbine installation according to claim 1, characterized in that at the exit of the free turbine the steam-air mixture is mixed with water. 5. The method of regulating the power of a gas turbine installation according to claim 1, characterized in that the waste heat boiler has a low pressure section - an economizer. 6. The method of regulating the power of a gas turbine installation according to claim 1, characterized in that the area of the flow areas of the nozzle apparatus of the turbines are regulated. 7. The method of controlling the power of a gas turbine installation according to claim 1, characterized in that a part of the steam generated in the recovery boiler is fed to the compressor turbine inlet.

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