RU2821667C1 - Method of converting thermal energy into electrical energy and turboelectric plant - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: group of inventions relates to conversion of thermal energy into electrical energy, and can be used in various power plants. First object of the group of inventions relates to a method for converting thermal energy into electrical energy, involving the use of a combined Brighton–Rankine cycle, wherein as fuel in the Brighton cycle and the working medium in the organic Rankine cycle, liquefied propane-butane which does not freeze at low negative temperatures of ambient air, before supply to combustion chamber in Brayton cycle air is heated in recuperator of gas turbine engine, and propane-butane is successively heated from stators of electric motors of circulation pumps and in heat exchangers-superheaters of low and high pressure due to energy of exhaust gases coming from gas turbine. At the same time, ORC-turbines are used to increase the electrical efficiency of the power plant, and to increase the efficiency of the Rankine cycle propane-butane is heated in ORC-turbine recuperator before supply to heat exchanger-superheater, propane-butane before supply to the low-pressure heat exchanger-superheater is heated by the heat released in the generator and electric drives stators, wherein the propane-butane in the low-pressure heat exchanger-superheater cools the exhaust gases coming from the gas turbine engine recuperator and the high-pressure heat exchanger-superheater, below the dew point, the formed condensate is supplied through the condensate collector to the inlet of the recuperator of the gas turbine engine, where it evaporates and, when mixed with heated air, forms a steam-air mixture entering the combustion chamber of the gas turbine engine, and the turboelectric plant, which includes an electric machine made in the form of a starter-generator and a shaft with a gas turbine engine, is characterized by that it additionally includes a recuperator of the gas turbine engine and an ORC turbine, note here that gas turbine engine and ORC turbine rotors are located in cold zones. In addition, a turboelectric plant is also disclosed.

EFFECT: increased efficiency of power plant, for example, expressed in increase of reliability and duration of operation, reduction of noise level and visibility in infrared and visible range of electromagnetic spectrum, as well as manufacturability of its maintenance.

2 cl, 1 dwg

Description

The invention relates to methods for converting thermal energy into electrical energy and can be used in various power plants.

Various methods are known to increase the efficiency of gas turbine power plants without increasing the exhaust temperature at the turbine inlet and improving the aerodynamic characteristics of the air compressor and turbine. Such solutions in particular include the use of a recuperator (heat exchanger) to heat the compressed air coming from the compressor into the combustion chamber using the thermal energy of the exhaust gases from the turbine.

From the technical literature, installations are known that implement the Brayton thermodynamic cycle, including heating a gaseous working fluid, converting thermal energy into mechanical energy through a turbocompressor, recovering the heat remaining in the working fluid after conversion and removing residual (after recovery) low-grade heat from the working circuit to the external environment . Steam turbine plants that implement the Rankine cycle are also known.

A combined closed-loop thermal system for waste heat recovery and a method for its operation are known (RU 2551458), including: a Brayton cycle system containing: a heater designed to circulate carbon dioxide vapor during heat exchange with a hot fluid, to heat the carbon dioxide vapor; a first turbine connected to the heater and configured to expand the carbon dioxide vapor; a refrigerator and a compressor for compressing carbon dioxide vapor supplied by the refrigerator; a Rankine cycle system coupled to a Brayton cycle system; wherein the Rankine cycle system includes a first heat exchanger, a second heat exchanger, and a third heat exchanger, wherein the carbon dioxide vapor from the first turbine circulates in heat exchange with the vaporous working fluid sequentially through the first heat exchanger, the second heat exchanger, and the third heat exchanger to heat the working fluid; a refrigerator for cooling carbon dioxide vapor supplied through the first heat exchanger, the second heat exchanger and the third heat exchanger; a fourth heat exchanger designed to circulate a vaporous working fluid in heat exchange with carbon dioxide vapor supplied from the compressor to heat the working fluid; wherein the carbon dioxide vapor from the fourth heat exchanger is heated by the Brayton cycle system heater; a second turbine for expanding a vaporous working fluid supplied from the fourth heat exchanger through the first heat exchanger; a condenser designed to condense the vaporous working fluid supplied from the second turbine through the third heat exchanger. The disadvantages of this system include the complexity of the design, the presence of several shafts and generators.

A power plant with machine energy conversion is known (RU 2716766), which includes an electric generator, a main closed gas circuit that implements the Brayton thermodynamic cycle, including a heat source, a turbocompressor kinematically connected to the electric generator, a heat exchanger-heat regenerator, a heat exchanger-refrigerator of a low-water exhaust system potential heat from the gas circuit and a main vapor-liquid closed circuit that implements the thermodynamic Rankine cycle, including a heat source in the form of a heat exchanger-steam generator, a turbopump unit kinematically connected to the electric generator, a refrigerator-condenser of the vapor phase of the working fluid, characterized in that the heat exchanger-steam generator is included in the heat transfer path in the gas circuit line between the heater and the turbine of the turbocompressor, the heat receiving path - in the vapor-liquid circuit line at the inlet to the turbine of the turbopump unit, while in the vapor-liquid circuit line between the pump of the turbopump unit and the heat exchanger-steam generator, an inter-circuit heat exchanger, the heat transfer path of which is sequentially connected by the heat receiving paths included in the line between the heat exchanger-heat regenerator and the heat exchanger-refrigerator of the gas circuit, and the heat exchanger-regenerator of the vapor-liquid circuit, the heat receiving path of which is included in the line between the turbine output of the turbopump unit and the entrance to the refrigerator-condenser. The disadvantage of this power plant is that power is transferred to the electric generator shaft mainly in the vapor-liquid circuit of the power plant, which leads to a decrease in the efficiency of the power plant.

The closest analogue, taken as a prototype, is a gas turbine unit with exhaust gas heat recovery (RU 2613756), containing a gas turbine engine consisting of an air compressor, a combustion chamber and a power turbine, and a steam circuit with a steam turbine and an evaporator heat exchanger with a line passing through it exhaust gas of a gas turbine engine, while the shafts of the power turbine and steam turbine are connected through a gearbox to the propeller shaft, characterized in that it is equipped with a cryogenic tank with liquefied natural gas, a cryogenic pump, a liquefied natural gas evaporator, through which an atmospheric air line passes into the air compressor, a natural gas heat exchanger-heater, through which the exhaust gas line of a gas turbine engine passes, while the air compressor, power and steam turbine are located on the same shaft, the steam circuit is made in the form of an organic Rankine cycle (ORC) installation containing a heat exchanger-evaporator, steam turbine, recuperator, heat exchanger-condenser and circulation pump, the exhaust gas line from the power turbine of the gas turbine engine sequentially passes through the steam circuit evaporator heat exchanger and the natural gas heat exchanger-heater, and the cooling medium line passes through the steam circuit heat exchanger-condenser.

The disadvantages of this solution are the use of liquefied natural gas with cryogenic storage temperature, which requires the use of complex storage systems; shallow degree of heat recovery, which is expressed in the use of a single-stage steam turbine unit operating according to the organic Rankine cycle, high temperature of exhaust gases at the outlet of the evaporator heat exchanger, non-use of a recuperator in a gas turbine engine; the use of a massive gearbox to transmit torque to the propeller; the presence of a condenser for cooling which uses sea water; the use of four different liquids: liquefied natural gas - as fuel in a gas turbine engine, working fluid - in ORC, oil - for cooling and lubrication of supports, sea water - for cooling the condenser.

The objective of the present invention is to eliminate these disadvantages and create a reliable and efficient turboelectric power plant.

The technical result of the proposed invention is to increase the efficiency of the power plant, which consists in increasing the reliability and duration of operation, reducing the noise level and visibility in the infrared and visible range of the electromagnetic spectrum, as well as the manufacturability of its maintenance.

The obtained technical result is achieved due to the fact that according to the invention, the method of converting thermal energy into electrical energy, including the use of a combined Brayton-Rankine cycle, is characterized in that the fuel in the Brayton cycle and the working fluid in the organic Rankine cycle is used as a fuel that does not freeze at low negative outside temperatures. air is liquefied propane-butane, before being fed into the combustion chamber in the Brayton cycle, the air is heated in the recuperator of the gas turbine engine, and propane-butane is sequentially heated from the stators of electric motors of circulation pumps and in heat exchangers-superheaters of low and high pressure due to the energy of exhaust gases coming from gas turbine, to increase the electrical efficiency of the power plant, ORC turbines are used, to increase the efficiency of the Rankine cycle, propane-butane is heated in the recuperator of the ORC turbine before being supplied to the high-pressure heat exchanger-superheater, propane-butane is heated in the recuperator before being supplied to the low-pressure heat exchanger-superheater due to the heat generated in the stators of the generator and electric drives, and propane-butane in the low-pressure heat exchanger-superheater cools the exhaust gases coming from the gas turbine engine recuperator and the high-pressure heat exchanger-superheater below the dew point, the resulting condensate through the condensate collector enters the inlet of the gas turbine engine recuperator, where evaporates and mixes with heated air to form a steam-air mixture entering the combustion chamber of a gas turbine engine, and a turboelectric installation, including an electric machine made in the form of a starter-generator, and a shaft with a gas turbine engine located on it, is distinguished by the fact that it additionally includes a gas turbine engine recuperator, and an ORC turbine, wherein the rotor supports of the gas turbine engine and the ORC turbine are located in cold areas.

The essence of the invention is illustrated by the installation diagram (Fig. 1), where

1 - fuel tank,

2 - receiver-capacitor,

3 - combustion chamber of a gas turbine engine,

4 - gas turbine engine recuperator,

5 - turbine of a gas turbine engine,

6 - gas turbine engine compressor,

7 - gas turbine engine rotor support,

8 - shaft,

9 - electric vehicle of a hybrid power plant,

10, 11 - superheater - high and low pressure heat exchanger (respectively),

12, 13 - ORC turbines,

14 - ORC turbine rotor support,

15 - condensate collector,

16 - recuperator for preheating the working fluid,

17 - drive-electric motor of the power plant,

18 - regulator valves,

19 - electric pumps.

The movement and dosing of propane-butane in the circuits of the Brayton and Rankine cycles is carried out using regulator valves and electric pump motors, installed accordingly and controlled by an automatic control system (not shown) of the power plant.

The connection between the Brayton and Rankine thermodynamic cycles is carried out through heat exchangers-superheaters 10 and 11.

When starting the power plant using a battery (not shown), the electric motor of the fuel pump is started, which fills the receiver-capacitor 2 with propane-butane from the fuel tank 1, and the electric motor of the circulation pump of the low-pressure circuit, which pumps liquefied propane-butane through the stator windings of the electric machine hybrid power plant 9 and rotor support 14 with the return of propane-butane back to the receiver-condenser 2, electric machine 9 of the hybrid power plant, which, working in starter mode, rotates shaft 8 and rotates the gas turbine engine and ORC turbines and electric motors of circulation pumps, which liquefied propane-butane is sent through a recuperator for preheating the working fluid 16, the stator windings of the electric motor drive of the hybrid installation 17 and the stator windings of the electric machine of the hybrid power plant 9 to the superheaters, high and low pressure heat exchangers 10 and 11. From heat exchangers 10 and 11, propane-butane is in the gaseous state is sent to the ORC of turbines 12 and 13 to perform work, after which it condenses in the receiver-condenser 2. When the shaft reaches 8 idle revolutions, the power supply to all electric pumps and other consumers of the aircraft is switched from the battery to the electric machine 9, as well as the drive - the electric motor of the hybrid power plant 17 - is started.

After starting the power plant, liquefied propane-butane from fuel tank 1 through the stator windings of the electric motors of the circulation pumps enters the combustion chamber 3, where it is ignited and further, due to the energy of the exhaust gases, accelerates the gas turbine engine and ORC turbine. The exhaust gases, cooling in the superheater-heat exchanger 11, condense, and the resulting water accumulates in the condensate collector 15, from which it is partially emptied outside with the help of an electric pump, and also returns back to the Brayton cycle, having previously undergone special treatment, followed by spraying behind the compressor of the gas turbine engine 6.

An increase in the efficiency of the Brayton cycle is ensured by supplying a high-temperature steam-air mixture into the combustion chamber of the gas turbine engine 3, which is formed by spraying water condensate from the condensate collector 15 behind the compressor 6 of the gas turbine engine, using the recuperator 4 of the gas turbine engine, in which, due to the heat of the exhaust gases after the gas turbine engine 5, the steam-air mixture entering the combustion chamber of the gas turbine engine 3 is heated and the propane-butane entering the combustion chamber 3 is subsequently heated and evaporated from low to high temperature due to the heat generated in the stators of the electric motors of the circulation pumps, as well as in the superheaters-heat exchangers 10 and 11 due to the heat of exhaust gases coming from recuperator 4.

Increasing the efficiency of the organic Rankine cycle is ensured by deep utilization of exhaust gas heat, for which two circuits are implemented in the Rankine cycle: a high and low pressure circuit. The heat source in the high-pressure circuit is the exhaust gases, which come from the recuperator 4 of the gas turbine engine into the high-pressure superheater-heat exchanger 10, as well as the low-grade heat of propane-butane at the outlet of the ORC turbine wheel 13.

The heat sources in the low-pressure circuit are exhaust gases that come from the high-pressure superheater-heat exchanger 10 to the low-pressure superheater-heat exchanger 11 and thermal energy from the windings of the electric machine of the hybrid power plant 9 and the drive of the electric motor of the power plant 17, as well as the rotor support 14 ORC- turbines In this case, the exhaust gases in the low-pressure heat exchanger-superheater 11 are cooled below the dew point, releasing the latent heat of vaporization used in the cycle, and the resulting condensate from the condensate collector 15, having undergone processing, enters the recuperator of the gas turbine engine, where it evaporates and mixes with heated air to form a steam-air system. mixture entering the combustion chamber of a gas turbine engine, which also increases the efficiency of the Brayton cycle.

The proposed method of converting thermal energy into electrical energy and the design of the installation allow:

- increase the existing level of efficiency and reliability in terms of ensuring a longer operating time of the power plant, as well as by expanding the operating temperature range in which it starts reliably;

- increase the environmental friendliness of the power plant through the use of a combustion chamber using gaseous fuel, as well as reducing the level of emissions of nitrogen oxides, carbon monoxide and carbon dioxide in the exhaust gases due to their absorption by water vapor in the combustion chamber and the low-pressure superheater-heat exchanger;

- reduce the noise level created by exhaust gases and the turbine of a gas turbine engine;

- reduce installation maintenance costs by eliminating the oil system;

- simplify the design by using the generator as a starter during startup, as well as reducing the number of supports and placing supports in cold areas;

- reduce the visibility of the installation in the visible and infrared range of the electromagnetic spectrum, due to the deep heat recovery of exhaust gases, the absence of soot particles due to the use of propane-butane as fuel, as well as due to the condensation of water vapor inside the installation and the absence of a contrail.

Claims (2)

1. A method for converting thermal energy into electrical energy, including the use of a combined Brayton-Rankine cycle, characterized in that liquefied propane-butane is used as a fuel in the Brayton cycle and a working fluid in the organic Rankine cycle; the air is heated before being fed into the combustion chamber in the Brayton cycle in the recuperator of a gas turbine engine, and propane-butane is sequentially heated in the stators of electric motors of circulation pumps, heat exchangers-superheaters of low and high pressure due to the energy of exhaust gases coming from behind the gas turbine, to increase the efficiency of the propane-butane Rankine cycle before being fed into the heat exchanger - the high-pressure superheater is heated in the recuperator of the ORC turbine, and before being fed into the low-pressure heat exchanger-superheater it is heated by the heat generated in the stators of the generator and electric drives; propane-butane in the low-pressure heat exchanger-superheater cools the exhaust gases coming from the gas turbine engine recuperator and high-pressure heat exchanger-superheater, below the dew point, and the resulting condensate through the condensate collector enters the inlet of the gas turbine engine recuperator, where it evaporates and, mixing with heated air, forms a steam-air mixture entering the combustion chamber of the gas turbine engine. 2. A turbo-electric installation, including a battery, an electric machine, an electric motor, static voltage converters, at least one shaft for outputting power with a gas turbine engine located on it, consisting of a compressor, a combustion chamber and a gas turbine, characterized in that it additionally includes a fuel tank, receiver-condenser, superheaters-heat exchangers of high and low pressure, at least two ORC turbines, one of which operates in turboexpander mode with a two-phase flow at the output, a gas turbine engine recuperator used to heat the air entering the combustion chamber, for exhaust gas heat account, and an ORC-turbine recuperator, used to heat the working fluid supplied from the receiver-condenser to the high-pressure superheater-heat exchanger, due to the heat at the outlet of the ORC-turbine, and the electric machine is made in the form of a starter-generator, and The rotor supports of gas turbine engines and ORC turbines are located in cold areas.