RU2284418C1 - Gas-turbine plant boosting method - Google Patents

Abstract

FIELD: mechanical engineering; gas-turbine plants.

SUBSTANCE: according to proposed method of boosting of gas-turbine plant water is delivered inside axial-flow compressor. Water is fed into inner space of rotor (drum) of axial-flow compressor with compression ratio not less than 15, and into heat exchanger arranged in compressor stator housing in amount not less than 3% of air flow through compressor. Steam formed in drum and heat exchanger is directed into gas-air duct of gas-turbine plant.

EFFECT: increased effective efficiency of gas-turbine plant.

6 cl, 7 dwg

Description

The invention relates to a power system.

A known method of forcing gas turbine engines (GTE) by injecting water at the entrance to an axial compressor (Theory and calculation of jet engines. Edited by S.M. Shlyakhtenko. M.: Engineering, 1987, S. 374-376). The method allows to increase the power of a gas turbine engine, but at the same time the efficiency of the engines is deteriorating. As experiments show, in the conditions of an axial compressor a gas turbine engine evaporates from 30 to 50% of the water injected in front of the compressor. The remaining water evaporates in the combustion chamber. Evaporation of water in the gas-air path of the compressor leads to cooling of the air (an increase in its flow rate, as well as a change in the heat capacity of the mixture) and, as a result, an increase in engine power. Evaporation of the remaining part of the water in the combustion chamber leads to the absorption of part of the energy of the hot gases and, as a consequence, to a decrease in the engine efficiency. In addition, the amount of water injected into the axial compressor is limited by the stability of the compressor and, as a rule, does not exceed 3% of the air flow through the compressor.

Known fuel-air heat exchanger (Patent RU No. 2241937, IPC 7 F 28 D 11/02, 2004), allowing to cool the air in the gas-air duct of the axial compressor. The heat exchanger is designed for gas turbine engines using cryogenic fuels. The capabilities of the heat exchanger are limited by the fuel consumption through the engine.

The problem to which the present invention is directed, is to increase the efficiency of gas turbine plants: effective efficiency η _e and effective power Ne.

The problem is solved due to the fact that in the method of forcing a gas turbine installation, which consists in supplying water to the inside of an axial compressor, water is supplied to the internal rotor cavity (drum) of the axial compressor having a compression ratio of at least 15 and to a heat exchanger located in the stator housing compressor, in an amount of at least 3% of the air flow through the compressor, with the subsequent removal of steam generated in the indicated drum and heat exchanger into the gas-air path of the gas turbine installation.

The problem is also solved due to the fact that the water is supplied in a boiling state (wet steam).

The problem is also solved due to the fact that part of the water (wet steam) from the inner cavity of the compressor drum is transferred to the gas-air path of the compressor.

The problem is also solved due to the fact that the water is heated in a heat exchanger located in the outlet channel behind the turbines of the installation.

The problem is also solved due to the fact that the gas temperature behind the turbines is less than 100 ° C.

The problem is also solved due to the fact that the compressor blades and the body of its stator are made of aluminum alloys.

The essence of the invention lies in the fact that in the inner cavity of the drum of the axial compressor of a gas turbine with a compression ratio of more than 15, and at the same time, water (wet steam) in an amount of more than 3% of the air flow is supplied to the channels (heat exchanger) made in the stator housing of this compressor through the compressor. When moving along the inner surface of the drum, water absorbs (due to heating and evaporation) part of the thermal energy of the air moving along the flow part of the compressor. The same thing happens when water moves along the stator channels. The steam generated in either case enters the turbine. The transfer of energy from the compressor flow path to the turbine provides a double effect:

- reduce the work of air compression (due to air cooling);

- increase the turbine (due to the use of steam energy and increase the mass of the working fluid).

Figure 1 shows a diagram of a gas turbine.

Figure 2 shows the dependence of effective efficiency on the parameters of the work process of a gas turbine.

Figure 3 shows the dependence of the effective power on the parameters of the work process of a gas turbine.

Figure 4 shows the dependence of effective efficiency on the parameters of the work process of a gas turbine.

Figure 5 shows the dependence of effective efficiency on the parameters of the work process of a gas turbine.

Figure 6 shows a diagram of a gas turbine.

Figure 7 shows the dependence of the effective efficiency of gas turbines and water parameters on the compression ratio of the gas turbine compressor.

The application of this method is illustrated by the operation of the gas turbine, the circuit of which is shown in figure 1.

A gas turbine (Fig. 1) consists of an input device, an axial compressor 1, consisting of a stator and a rotor, a combustion chamber 2, a mixing chamber 3, a compressor drive turbine 4, a free turbine 5, an output device, pumps (n) standing in the discharge lines water and fuel, respectively. In the stator housing, channels 6 (heat exchanger) are made, connecting the source of feed water to the cavity behind the compressor (mixing chamber). The inner cavity of the rotor (drum) is connected on one side to a source of feed water and, on the other hand, to a cavity behind the compressor (mixing chamber).

The method of forcing a gas turbine is as follows. Air through the input device enters the compressor 1 for compression. Compressed to a predetermined pressure air (compression ratio of at least 15) is sent to combustion chamber 2, where finely atomized fuel is simultaneously supplied. The gas resulting from combustion is directed into the mixing chamber 3.

Water under a pressure exceeding the pressure behind the compressor is supplied to the stator channels 6 and to the internal cavity of the compressor drum 1.

In channels 6, water evaporates due to heat exchange with the stator housing, turning into dry (superheated steam).

When water enters the inner cavity of the rotor on its inner surface under the action of centrifugal forces, a film is formed that moves (through the holes in the disks) towards the more heated part of the compressor. The film is heated on both sides: on the outside - by the rotor housing; with internal - dry steam circulating in the internal cavity of the rotor. The steam circulation occurs due to the pressure difference between the peripheral and central layers - the so-called reverse current zones (Yu.N. Nechaev, P.M. Fedorov. Theory of aircraft gas turbine engines. 4.2. M .: Mashinostroenie, 1978, p. 66, Fig. 11.6). As a result of double exposure, the film is heated and evaporated intensively, absorbing a significant amount of heat.

As a result of heating and evaporation of water, the stator housing and rotor housing are cooled. The resulting temperature difference (thermal pressure) between the air and the compressor design creates a heat flow that lowers the air temperature in the compressor flow path. The amount of heat flow with sufficient water flow is determined by the compression ratio of the compressor and the thermal resistance of the rotor and stator housings.

Lowering the temperature of the air when it is compressed in the compressor reduces the work required to drive the compressor, which reduces the pressure drop across the turbine of the drive 4. The dry steam generated by the evaporation of water through the corresponding channels enters the mixing chamber 3.

In the mixing chamber 3, hot gas and dry (superheated) steam are mixed, as a result of which the temperature of the working fluid (steam-gas mixture) is set within the limits allowed by the strength conditions of the turbine blades, and the enthalpy of the working fluid and its mass increase. From the mixing chamber 3, the working fluid enters the drive turbine 4, and then into the free turbine 5, which performs useful work. Useful work increases for three reasons:

- increases the pressure drop across a free turbine due to a decrease in the pressure drop across the drive turbine 4;

- the enthalpy of the working fluid increases due to the addition of the energies of gas and steam;

- increases the mass of the working fluid due to the addition of masses of air, fuel and water. The working fluid through the output device is removed into the atmosphere.

Thus, the proposed method allows to increase the useful work of gas turbines, i.e. effective efficiency. In addition, the method allows to increase the effective capacity of gas turbines (power per kilogram of air flow). Using the mixing chamber 3 allows to reduce the coefficient of excess air in the combustion chamber, which is equivalent to increasing the effective power of gas turbines.

Figures 2 and 3 show the effect of the proposed method on the effective efficiency and effective capacity of a gas turbine, depending on the degree of compression of the compressor Pc and the gas temperature in front of the turbine Tg *, respectively (dashed lines show the initial characteristics of a gas turbine, solid lines when using the method). In the calculation, the following assumptions were made: thermal head ΔТ between air and steam at the outlet of the compressor - 150 ° С; Compressor efficiency - 0.85; Turbine efficiency - 0.94; pressure loss in the combustion chamber and the mixing chamber of 3%. The disadvantage of GTU of conventional schemes, as is known, is their degeneration with increasing PC, which can be seen from the dependences shown in Fig. 2 (dashed lines). The proposed method solves the problem of degeneration of gas turbines. So with an increase in Pc (in the case of water supply to the gas turbine compressor), the coefficient of excess air in the combustion chamber practically does not change. The fact is that in a gas turbine with water supply, the temperature at the outlet of the combustion chamber is not limited by the temperature of the gas in front of the turbine and increases with increasing PC. In addition, the temperature at the outlet of the compressor (at the entrance to the combustion chamber) increases more slowly than in conventional gas turbines. The proposed method also solves the problem of high gas temperatures in front of the turbine turbine. In GTU of conventional schemes, the increase in Tg *, as is known, is dictated by the desire to increase efficiency through the use of higher Pc. In gas turbine engines with water supply, this is not necessary, since there are no reasons for the degeneration of gas turbines. On the contrary, in a gas turbine with water supply, it is necessary to strive to lower Tg *, because while reducing losses with exhaust (figure 2).

The main structural problem in the implementation of the method is the organization of effective heat transfer in the compressor between air and water. An indicator of the efficiency of heat transfer is the temperature difference ΔT between air and steam at the outlet of the compressor.

Figure 4 shows the effect of ΔT on the effective efficiency of a gas turbine at a gas temperature in front of the turbine of 1000 K. The contours corresponding to the same water flow t, expressed as a percentage of air flow, are plotted here. It can be seen that the effectiveness of the method begins to manifest itself with a PC of large 15 and m large 3%.

A decrease in ΔT can be achieved by the following measures:

- the use of materials with high coefficients of thermal conductivity, for example, aluminum alloys, in the design of the compressor;

- an increase in the number of compressor stages;

- an increase in the relative diameter of the sleeve of the compressor rotor;

- using partial bypass of water (wet steam) from the inner cavity of the drum or through the stator to the flow part of the compressor (through perforated holes);

- a decrease in the speed of air movement along the flow part of the compressor;

- the use of a "water jacket" around the compressor stator.

The greatest efficiency from the application of the method occurs if the gas temperature behind the turbine is lowered to 100 ° C or lower. Figure 5 shows the effective efficiency of gas turbines, which are obtained in this case, as well as the parameters of the work process. It is seen that in order to achieve maximum efficiency it is necessary to have high Pc and sufficiently low ΔТ, which is not always possible.

The effectiveness of the proposed method can be improved by using the energy of the gases leaving the turbines of the gas turbine, which allows to obtain high efficiency with moderate parameters of the working process. Figure 6 shows a diagram of a gas turbine with an additional heat exchanger 7 installed behind a gas turbine turbine. Water in the heat exchanger 7 turns into wet steam, the degree of humidity of which depends on the parameters of the working process (the lower the PC, the higher the humidity of the steam). From the heat exchanger 7, water (wet steam) enters the inside of the compressor drum 1.

7 shows the effective efficiency (for three values of the gas temperature in front of the turbine: 1000, 1200 and 1400 K) depending on the PC and the corresponding water parameters: water flow m; steam humidity x; water temperature (wet steam) TV. Dependences (Fig. 7) are constructed for the circuit (Fig. 6) with a thermal pressure at the outlet of the compressor ΔT = 150 ° C. A step change in the parameters (Fig. 7) corresponds to the transition of steam into water and back, which is determined by the energy of the heat exchanger. It can be seen that the effective efficiency even with moderate PCs exceeds 50%.

Thus, the proposed method of forcing a gas turbine allows increasing the effective efficiency up to 70% or more, which is significantly higher than modern technologies for manufacturing power plants can offer today. So, for example, the efficiency of promising combined cycle plants today is focused on the level of 58 ÷ 60%. The proposed method also allows to increase the effective capacity of gas turbines. So, for example, if you compare the installation with the water supply with the installation without water supply, then the increase in power can be 100 ÷ 200%. A very attractive consequence of the proposed method is the low gas temperature in front of the turbine, which guarantees a high resource and relatively low cost of manufacturing the installation, which at the current cost of manufacturing modern gas turbines is important.

Claims (6)

1. The method of forcing a gas turbine installation, which consists in supplying water to the inside of an axial compressor, characterized in that the water is supplied to the inner cavity of the rotor (drum) of the axial compressor having a compression ratio of at least 15, and to a heat exchanger located in the compressor stator housing, the amount of not less than 3% of the air flow through the compressor, with the subsequent removal of the steam generated in the indicated drum and heat exchanger into the gas-air path of the gas turbine installation. 2. The method of forcing a gas turbine installation according to claim 1, characterized in that the water is supplied in a boiling state (wet steam). 3. The method of forcing a gas turbine installation according to claim 1, characterized in that part of the water (wet steam) from the internal cavity of the compressor drum is bypassed into the gas-air path of the compressor. 4. The method of forcing a gas turbine installation according to claim 1, characterized in that the water is heated in a heat exchanger located in the outlet channel behind the turbines of the installation. 5. The method of forcing a gas turbine installation according to claim 1, characterized in that the gas temperature behind the turbines is less than 100 ° C. 6. The method of forcing a gas turbine installation according to claim 1, characterized in that the compressor blades and the body of its stator are made of aluminum alloys.

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