RU2666701C1 - Stoichiometric steam and gas installation - Google Patents

Abstract

FIELD: power engineering.SUBSTANCE: invention relates to power engineering. Steam and gas installation consists of two circuits – internal and external and a gas outlet channel. In the internal circuit there is a turbocharger, in the external one there is a heat exchanger, cooling high-pressure air, used to cool the turbocharger. At the output of the external circuit, a free turbine is installed, at the outlet from the internal circuit there is a gas channel in which two heat exchangers are located that convert the energy of the exhaust gases into steam energy. Working body of the first and the second heat exchangers is water and freon, concordantly. Water vapor is supplied to a mixing chamber located between the combustion chamber and the turbine of the turbocharger. This allows the stoichiometric composition of the air-fuel mixture to be maintained in the combustion chamber. Vapor freon is fed into the steam turbine, which is an element of the closed circuit of the steam power plant.EFFECT: invention allows to increase the effective efficiency of the installation.6 cl, 3 dwg

Description

The invention relates to a power system.

Numerous publications are devoted to gas turbine units (GTU) for various purposes, used in aviation, land and sea transport, at gas pumping stations. In recent years, there has been a significant increase in interest in energy gas turbines and gas turbines (combined cycle plants), their features and work in power plants. Combined cycle plants are the only power plants that release electricity with an efficient efficiency in the condensation mode of operation more than 58% (Gas-turbine and combined-cycle plants of thermal power plants: Textbook for universities / Ed. by S.V. Tsanaev - M .: MEI Publishing House, 2002. P. 3).

The aim of the invention is to increase effective efficiency combined-cycle plants up to 60 ÷ 65%.

A stoichiometric combined-cycle plant is known, consisting of an input device, an internal circuit, inside of which there is a turbo-compressor with a mixing chamber, with a gas channel connecting the circuit to the atmosphere containing a heat exchanger-evaporator, on the one hand connected to a source of feed water, and on the other hand with a mixing chamber, an external circuit at the output of which a free turbine is installed, a heat exchanger-regenerator located behind the turbocompressor and connecting the free turbine to the air cavity in high pressure (patent RU 2287708, 2006).

Gas turbine engines are known in which a diffuser nozzle is installed behind a free turbine, which allows increasing the pressure drop in the turbine more than that available (Nechaev Yu.N., Fedorov PM Theory of aircraft gas turbine engines. Part 2. M: Engineering, 1978, p. 268, Fig. 19.2).

There are known gas ejectors capable of lowering the static pressure at the exit of the jet nozzle (G. N. Abramovich. Applied gas dynamics. M: Nauka, 1976, p. 487, Fig. 9.4).

This goal is achieved by the fact that in a stoichiometric combined-cycle plant, consisting of an input device, an internal circuit, inside which there is a turbocharger with a mixing chamber, with a gas channel connecting the circuit to the atmosphere, containing a heat exchanger-evaporator, on the one hand connected to a source of feed water, and on the other hand, with a mixing chamber, an external circuit at the output of which a free turbine is installed, a heat exchanger-regenerator located behind the turbocompressor and connecting the free a turbine with a high-pressure air cavity, a fan is installed that pumps air into the internal and external circuits, a condenser heat exchanger is connected inside the gas channel, connected to a heat energy recovery unit, a free turbine is connected to the gas channel in the section between the heat exchanger-evaporator and the heat exchanger-condenser, in the external a heat exchanger is located in the circuit, the high-pressure channel of which connects the air cavity behind the compressor with the air channels of the turbocharger turbine for its cooling Denia.

The essence of the invention lies in the use of internal thermodynamic cycles, which, with the same physical limitations, can increase the amount of heat input and reduce the amount of heat removed in a heat engine (Pismenny V.L. Internal thermodynamic cycles // M. - Conversion in mechanical engineering. 2006, No. 3. S. 5 ÷ 10).

In CCGT, it is preferable to have:

the coefficient of excess air in the combustion chamber is less than 1.1;

the degree of increase in air pressure in the fan is more than 7;

the total degree of increase in air pressure over 40;

inside the heat exchanger-regenerator - an ejector;

ceramic nozzle apparatus in a turbocharger turbine;

steam power plant as a heat energy utilizer.

In FIG. 1 shows a stoichiometric CCGT.

in FIG. 2 shows the thermodynamic cycle of a stoichiometric CCGT;

in FIG. Figure 3 shows the dependence of the stoichiometric CCGT parameters on the total degree of increase in air pressure.

The stoichiometric CCGT (Fig. 1) consists of an input device 1, a fan 2, internal and external circuits, a gas channel 3, and a heat energy utilizer.

In the internal circuit are located: a turbocompressor 4, a low-pressure cavity of the heat exchanger-regenerator 5, an ejector 6 (located inside the heat exchanger 5 - covers the output section of the turbocompressor). Between the combustion chamber and the turbine of the turbocharger there is a mixing chamber 7.

In the external (second) circuit there are: a heat exchanger 8, a high pressure cavity of the heat exchanger-regenerator 5, a free turbine 9. The internal channels of the heat exchanger 8 are connected on one side to the air cavity behind the turbocompressor compressor, and on the other, to the air channels of the turbocharger turbine.

In the gas channel 3 connecting the low-pressure cavity of the heat exchanger 5 with the atmosphere, there are: a heat exchanger-evaporator 10 and a heat exchanger-condenser 11. The high-pressure cavity of the heat exchanger-regenerator 5 is connected to the gas channel 3 through a turbine 9 in the area between the heat exchangers 10 and 11.

The heat energy utilizer consists of a heat exchanger-condenser 11, a steam turbine 12, a heat exchanger-condenser 13 and a pump (n), which are looped. Freon R22 circulates inside the looped system. The heat exchanger 13 is washed with running water, part of which is supplied with a high pressure pump (n) to the heat exchanger 10.

Fan 2 is connected to turbocharger 4 through a gearbox (P).

The stoichiometric CCGT is as follows. The turbocharger 4 drives a fan 2, which pumps air into the internal and external circuits of the installation.

In the internal circuit, fuel energy Q _{1 is} supplied to the air, part of which in the form of heat (through heat exchanger 8) and work (through fan 2) is transferred to the external circuit of the installation. The air taken from the compressor for cooling the turbine passes through the high pressure channel of the heat exchanger 8 and transfers part of the heat to the air of the external circuit. Fan 2, compresses the air, part of which enters the external circuit. The remaining heat in the form of energy of the outgoing gas enters the low-pressure cavity of the heat exchanger-regenerator 5.

Compressed and heated air of the external circuit enters the high pressure cavity of the heat exchanger-regenerator 5.

The operation of the heat exchanger-regenerator is as follows. Hot gas from the turbocharger flows into the ejector 6. The static pressure in the plane of the outlet section of the turbocharger is lower than the pressure in the low-pressure cavity of the heat exchanger 5, which is close to atmospheric. As a result of the pressure difference outside and inside the ejector 6, gas circulates inside the low pressure cavity of the heat exchanger 5, which intensifies the heat exchange processes. The technical capabilities of the heat exchanger-regenerator are determined by the technical capabilities of the circulation heat exchanger (patent RU 2607916, 2017), i.e. under certain conditions, the difference in gas and air temperatures leaving the heat exchanger-regenerator 5 can be minimized (20 ÷ 30 degrees). Another plus from the use of the heat exchanger-regenerator 5 is the possibility of using the effect of gas over-expansion in the turbine, when the static pressure behind the turbine artificially decreases below atmospheric pressure with its subsequent increase with the removal of heat.

High-pressure air, heated in the heat exchanger 5, enters the receiver of the turbine 9, where it expands - performs work, and then expires in the gas channel 3.

Low pressure gas from the heat exchanger 5 enters the gas channel 3, where part of the heat of the gas is given to the heat exchanger-evaporator 10. Water moves in the high pressure channel of the heat exchanger 10, which when heated turns into saturated steam. The steam enters the mixing chamber 7 of the turbocharger. The amount of water (steam) is selected from the condition of ensuring the stoichiometric composition of the air-fuel mixture in the combustion chamber of the turbocompressor.

After the heat exchanger 10, the gas moving along the channel 3 is mixed with the air flowing out from the turbine 9. The resulting mixture (exhaust gases) enters the heat exchanger-condenser 11. In the heat exchanger-condenser 11, the heat of the exhaust gases is transferred to freon R22, which circulates in the high channel pressure of the heat exchanger 11. When cooling the exhaust gases, condensate (water used in the heat exchanger 10) is released, which together with the exhaust gases is removed into the atmosphere.

The operation of the heat recovery unit is as follows.

The critical pressure and critical temperature of Freon R22 are: P _cr = 5 MPa and T _cr = 96 ° C, respectively. Freon under a critical pressure pump (n) is fed into the high pressure channel of the heat exchanger 11, where it is heated to a critical temperature. In the steam turbine 12, the freon expands to a pressure at which it is condensed in the heat exchanger 13. The turbine 12 does the work. The heat released during condensation is removed by running water (initial temperature ~ 15 ° C; final temperature ~ 30 ° C). The cooled freon is compressed by the pump (n). The cycle repeats.

Feed water pump (n) is supplied to the heat exchanger-evaporator 10.

In FIG. 2 in P-υ coordinates shows the thermodynamic cycle of the stoichiometric CCGT (Fig. 1). The cycle consists of an external cycle 1 (Brighton cycle) and two internal cycles: 2 (Brighton cycle) and 3 (Rankine cycle). The external cycle has energy exchange with the external environment, the internal - with the external cycle. Heat Q ₁ is supplied to the external cycle, Qr is removed. Thermal efficiency stoichiometric CCGT is defined as η _t = 1-Qr / Q ₁ .

The essence of the invention lies in the fact that at the same time two factors are used to increase the efficiency of the heat engine: a) the stoichiometric composition of the air-fuel mixture; b) internal thermodynamic cycles. The stoichiometric composition of the air-fuel mixture allows to maximize the amount of heat input Q ₁ . Internal thermodynamic cycles maximize the amount of heat removed Qr. Both that, and another increases thermal efficiency heat engine and, as a result, effective efficiency

The stoichiometric composition of the air-fuel mixture in the CCGT combustion chamber is ensured by the presence of a mixing chamber 7 in the CCGT circuit (Fig. 1), which protects the turbine blades from overheating (thermal energy is distributed over a large mass of gas) for any composition of the air-fuel mixture, including stoichiometric. Use of the mixing chamber allows to increase the maximum temperature of the gas in the outer loop (Fig. 2) to the gas temperature in the combustion chamber _kc ^* T which is higher than the gas temperature before the turbine T _r ^* (FIG. 2). It is known from thermodynamics that an increase in the maximum gas temperature in the Brighton cycle increases its work and efficiency, which, in fact, occurs in stoichiometric CCGT.

The effectiveness of using internal thermodynamic cycles is a direct consequence of the laws of thermodynamics. In accordance with the first law of thermodynamics, heat Q ₁ is spent on the operation of the external cycle 1, internal cycles 2 and 3 (the work of the cycles is determined taking into account the flow rate of the working fluid), heat loss Qr. In the absence of internal cycles 2 and 3, the same heat Q ₁ will be spent on the operation of external cycle 1 and the loss of Qr, which implies that in the absence of internal cycles, the loss of Qr increases by the amount of work of these cycles.

The heat fluxes occurring in the stoichiometric CCGT are shown in FIG. 2. Heat Q _{1 is} supplied to the external cycle (process k-g). Part of this heat is converted into work Lс ₁ , which is used to compress the working fluid _{of the} internal cycles, including in pumps (n). Another part of the heat (Q _1-2 and Q _1-3 ) is transferred to the internal cycles, in which it is converted into work Lts ₂ and Lts ₃ . The heat Q _2-1 and Q _{3-1 that is not} realized in internal cycles is returned (conditionally) to the external cycle, after which it is dissipated in the atmosphere in the form of heat Qr. A small part of the heat Q _{1-1 is} regenerated in the external cycle.

In FIG. 3 shows the characteristics of the stoichiometric CCGT (Fig. 1) depending on the total degree of increase in air pressure π _∑ . Legend: π _B is the degree of increase in air pressure in the fan, π _k is the degree of increase in air pressure in the compressor; m is the bypass ratio; m _in - the relative flow rate of water (relative to the flow rate of air through the internal circuit); m _f - the relative consumption of freon (similarly); Tv ^* - air temperature at the outlet of the fan; Tk ^* - air temperature at the outlet of the compressor; Tks ^* - gas temperature at the outlet of the combustion chamber; Tg ^* is the temperature of the gas at the entrance to the turbine of the turbocompressor; TVG ^* - air temperature at the inlet to a free turbine; tin - gas temperature at the inlet to the heat energy utilizer; tout - gas temperature at the outlet of the heat energy utilizer; η _e∑ - total effective efficiency CCP, η _e - effective efficiency CCPP (without heat energy utilizer).

CCP initial data: standard external conditions; fuel - kerosene; working body of an energy utilizer - freon R22; the coefficient of excess air in the combustion chamber is 1.05; the degree of increase in pressure in the fan - 8; gas temperature in front of the turbine - 2400 K; the temperature of the blades of the first stage of the turbine is 1250 K; coefficient of intensity of cooling of the turbine blades - 0.65; air extraction for cooling the turbine - 18%; efficiency fan - 0.83; efficiency compressor - 0.83; efficiency turbocharger turbines - 0.96; efficiency free turbine - 0.95; efficiency steam turbine - 0.9; mechanical efficiency - 0.99; the completeness of fuel combustion is 0.99; the pressure recovery coefficient in the combustion chamber is 0.98; Coefficients of pressure recovery in heat exchangers - 0.98.

It is seen (Fig. 3) that the method of internal thermodynamic cycles (Pismenny VL Internal thermodynamic cycles // M. - Conversion in mechanical engineering. 2006, No. 3. P. 5 ÷ 10) in combination with aviation technologies of the fifth-sixth gas turbine engine generations (cooled single-crystal blades, ceramic nozzle apparatuses, blisk technology, high efficiency of blade machines and etc.) allows you to create heat engines with effective efficiency 65 percent or more, which gives reason to consider stoichiometric CCGT as a breakthrough technology in the field of heat power.

The needs of society in providing energy are constantly growing despite the fact that the possibilities of increasing the production of hydrocarbon fuels have reached their limits. In these conditions, the creation of energy-saving technologies becomes an urgent task. In Russia, according to the author, a program should be adopted to develop and introduce stoichiometric CCGTs into the national economy. This will make it possible, at the same fuel consumption, to increase the generation of electricity at thermal power plants by 2–3 times.

Claims (6)

1. A stoichiometric combined-cycle plant, consisting of an input device, an internal circuit, inside of which there is a turbocharger with a mixing chamber, with a gas channel connecting the circuit to the atmosphere containing a heat exchanger-evaporator, on the one hand connected to a source of feed water, and on the other, from a mixing chamber, an external circuit at the output of which a free turbine is installed, a heat exchanger-regenerator located behind the turbocompressor and connecting a free turbine with an air cavity of high pressure, characterized in that it contains a fan that pumps air into the internal and external circuits, inside the gas channel there is a condenser heat exchanger connected to a heat energy utilizer, a free turbine is connected to the gas channel in the area between the heat exchanger-evaporator and the heat exchanger-condenser, in the external circuit a heat exchanger is located, the high-pressure channel of which connects the air cavity behind the compressor with the air channels of the turbocharger turbine to cool it. 2. The stoichiometric combined-cycle plant according to claim 1, characterized in that the coefficient of excess air in the combustion chamber is less than 1.1. 3. The stoichiometric combined-cycle plant according to claim 1, characterized in that the degree of increase in air pressure in the fan is more than 7, the total degree of increase in air pressure is more than 40. 4. The stoichiometric combined-cycle plant according to claim 1, characterized in that a gas ejector is located inside the heat exchanger-regenerator. 5. The stoichiometric combined-cycle plant according to claim 1, characterized in that the nozzle apparatus of the turbocharger turbine is ceramic. 6. The stoichiometric combined-cycle plant according to claim 1, characterized in that the heat energy utilizer is a steam power plant.

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