CN113236426A

CN113236426A - Based on transcritical CO2Multi-mode combined power cycle system and method

Info

Publication number: CN113236426A
Application number: CN202110600051.8A
Authority: CN
Inventors: 葛浩; 岳晨; 范育新; 于文博; 姚尚军
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2021-08-10
Anticipated expiration: 2041-05-31
Also published as: CN113236426B

Abstract

A multi-mode combined power cycle system and method based on transcritical CO2 belong to the field of aviation power propulsion. The invention couples the turbine engine, the ramjet engine and the supercritical CO2 Brayton cycle, so that the hypersonic aircraft can be switched under various modes, thereby achieving the purpose of working in a wider area. The system comprises an air inlet channel (1), an inner duct (2), an outer duct (3), a precooler (4), an air compressor (5), a main combustion chamber (6), an air turbine (7), an afterburner (8), a spray pipe (9), a CO2 turbine (12), a condenser (13), a pump (14), a liquid CO2 tank (10), a liquid oxygen tank (15), a first switch (11) and a second switch (16). According to the combined power cycle provided by the invention, a transcritical CO2 closed type heat energy cascade recovery Brayton cycle is adopted in an ultra-precooling flight mode, and liquid oxygen is utilized for condensation, so that the energy utilization of the system is maximized. In addition, the supercritical CO2 is adopted as the precooling working medium to replace the traditional helium, so that the system is more compact in structure and higher in thrust, and can quickly meet the requirement of wider-area work.

Description

Based on transcritical CO2Multi-mode combined power cycle systemAnd method

Technical Field

The invention relates to a multi-mode combined power circulation system and method based on transcritical CO2, and belongs to the field of improvement of combined power circulation systems of aero-engines.

Background

In hypersonic speed remote cruise flight, a power system needs to meet the requirement that the performance in a Ma 0-5 flight envelope is optimal, and the traditional engine in a single form is difficult to stably work in a full-speed domain range. However, when the flight speed is increased, the total temperature of the inlet airflow of the air inlet channel is increased, and is limited by materials, and the total temperature of the inlet of the air turbine has an upper limit, so that the increase of the total temperature of the incoming flow gradually reduces the heating capacity of the air, and the thrust in the mode switching stage is small. To solve this problem, a composite precooling scheme has come into use, and the most popular scheme is a "bent blade" engine. The engine with the bent blades has two working modes, namely a low-speed mode and a high-speed mode. Thrust is mainly provided through the bypass turbofan engine in the low-speed mode (0-2.5), and the bypass channel is closed in the high-speed mode (2.5-5), and the precooling system is opened to apply work through the turbine ramjet engine. The 'bent blade' engine combines the characteristics of a turbine engine and a ramjet engine, so that the working speed range of the 'bent blade' engine is wider, the working airspace of the 'bent blade' engine is wider, the problem of 'thrust gap' of a mode conversion point of a TBCC engine is avoided, the problem of insufficient injection mode thrust gain of a low-speed section of the RBCC engine is avoided, all parts of the engine in a whole working area can realize high-efficiency work, but the 'bent blade' engine selects helium as a cooling medium, because the characteristics of low density and effective utilization of sensible heat exchange capability will bring about insufficient precooling capability and huge and complex structure of a precooling system, the method puts high requirements on the thermal management technology of the aircraft, simultaneously, the reduction of the oxygen content in an afterburner also becomes one of the key factors that the engine cannot further improve the Mach number, therefore, the aircraft with strong precooling capability and simple precooling system structure becomes an important direction for the next development of the turbo-stamping combined engine.

Disclosure of Invention

The invention aims to provide a multi-mode combined power cycle system based on transcritical CO2 and a method thereof.

A multi-mode combined power cycle system based on transcritical CO2 is characterized by comprising an air inlet channel, an inner duct, an outer duct, a precooler, an air compressor, a main combustion chamber, an air turbine, an afterburner, a spray pipe, a liquid CO2 tank, a first switch, a CO2 turbine, a condenser, a pump, a liquid oxygen tank, a second switch and fuel; the outlet of the air inlet channel is divided into a first outlet branch and a second outlet branch, the first outlet branch is connected with the inlet of the hot side of the precooler through an inner duct, the outlet of the hot side of the precooler is connected with the inlet of the hot side of the main combustion chamber through the compressor, the outlet of the hot side of the main combustion chamber is connected with the inlet of the hot side of the afterburner after the air turbine applies work, and the air in the outlet of the hot side of the afterburner is discharged after passing through the spray pipe; the second outlet branch is connected with the inlet at the hot side of the main combustion chamber through an outer duct; an outlet of the liquid CO2 tank is connected with a cold side inlet of the precooler after passing through a first switch, the cold side outlet of the precooler is connected with a cold side inlet of the main combustion chamber, the cold side outlet of the main combustion chamber is connected with a hot side inlet of the condenser after doing work through a CO2 turbine, and the hot side outlet of the condenser is connected with an inlet of the liquid CO2 tank through a pump; an outlet of the liquid oxygen tank is connected with a cold side inlet of a condenser through a second switch, the cold side outlet of the condenser is connected with a cold side inlet of the afterburner, and the cold side outlet of the afterburner is connected with a hot side inlet of the afterburner; the air inlet channel is an adjustable air inlet channel.

The working method of the multi-mode combined power cycle system based on the transcritical CO2 comprises the following processes: can be divided into 3 modes (a turbine mode, a transonic speed mode and a super precooling mode);

turbine mode: the flight Mach number is 0-0.9; the first switch and the second switch are closed, the outer duct is opened by regulating and controlling the air inlet channel, air enters the air inlet channel and then is divided into the inner duct and the outer duct, the air in the outer duct directly enters the main combustion chamber, the air in the inner duct enters the air compressor to be boosted, high-pressure air enters the main combustion chamber to be combusted, high-temperature and high-pressure air does work through the air turbine to provide work required by the air compressor, and the high-temperature and high-pressure air after doing work directly passes through the spray pipe to generate required thrust;

transonic mode: the flight Mach number is 0.9-2.5; on the basis of a turbine mode, high-temperature and high-pressure air which does work through an air turbine (7) firstly enters an afterburner (8) for further combustion, and then air with higher temperature and higher pressure passes through a spray pipe (9) to generate huge thrust;

super-precooling mode: the flight Mach number is 2.5-8.0; opening the first switch and the second switch, enabling liquid CO2 in a liquid CO2 tank to enter a precooler for preheating, introducing primarily heated CO2 gas into a main combustion chamber for heat exchange, heating, introducing high-temperature and high-pressure CO2 gas into a CO2 turbine for work, increasing thrust, condensing CO2 gas after work through a condenser, and then changing the gas into high-pressure liquid CO2 through pressurization of a pump to be stored in a liquid CO2 tank again; meanwhile, the outer duct is closed by regulating and controlling the air inlet channel, air enters the inner duct after entering the air inlet channel, the air in the inner duct enters the air compressor for boosting through the cooling of the precooler, high-pressure air enters the main combustion chamber for combustion, high-temperature and high-pressure air provides work required by the air compressor through the air turbine, the high-temperature and high-pressure air after acting is introduced into the afterburning chamber for further combustion, and then the air with higher temperature and higher pressure is applied through the spray pipe; the liquid oxygen in the liquid oxygen tank is evaporated by the condenser to become O₂The gas is introduced into the afterburner, the oxygen content in the afterburner is increased, the combustion is more sufficient, and higher thrust is obtained, so that higher flight speed is realized.

Compared with the prior art, the invention has at least the following advantages: compared with the traditional helium gas which is super-precooled by sensible heat, the invention adopts the supercritical CO2 as a precooling working medium, fully utilizes the latent heat of vaporization of CO2, enhances the precooling effect, makes the combined cycle have larger thrust in a super-precooling mode, and simultaneously makes up the defect of low helium gas density by the characteristics of high pressure and high density of the supercritical CO2, makes the carrying and the storage more convenient, reduces the space occupancy rate and further reduces the structural complexity; in the system, CO2 is preheated in a precooler and then is further heated in a main combustion chamber, so that the cascade energy recovery of CO2 is realized, the energy recovered by the cascade energy recovery is utilized to do work by a turbine, and the energy utilization maximization of the whole process is realized. Compared with the most advanced engine with the curved blade at present, the invention adds the oxygen supplementing system, solves the problem of difficult ignition due to low oxygen content in the afterburner, improves the combustion efficiency, improves the combustion temperature, increases the thrust, and simultaneously condenses CO2 as an evaporant, so that the whole structure is more compact. The fuel used by the engine in the invention is aviation kerosene, while the fuel adopted in the 'bent blade' engine is liquid hydrogen, and the aviation kerosene has the advantages of high availability, low acquisition cost and high safety factor.

The multi-modal combined power cycle system based on transcritical CO2 is characterized in that: the wall surfaces of the main combustion chamber and the afterburner are respectively provided with a heat exchanger, and the heat exchangers and the condensers both adopt a dividing wall type heat exchanger structure, so that the wall surface of the combustion chamber is effectively cooled, and meanwhile, part of high-grade heat energy can be recovered to improve the thrust of CO2 Brayton cycle; the precooler adopts a wound tube type heat exchanger structure, and the wound tube type heat exchanger has the advantages of compact structure, quick cooling, smaller weight and high heat exchange efficiency, and can effectively avoid blocking an air inlet channel.

The multi-modal combined power cycle system based on transcritical CO2 is characterized in that: the super-precooling working mode adopts CO2 as a working medium. Compared with the traditional helium, the CO2 is used as a working medium, sensible heat exchange with the helium is distinguished, the better precooling effect can be achieved by fully utilizing the gasification potential of the CO2, larger thrust is generated, and the carried supercritical CO2 has the characteristics of high density and high pressure, is more convenient to carry and store compared with the helium, occupies smaller space, and can enable the structure of the whole system to be more compact.

Drawings

FIG. 1 is a multi-modal combined power cycle system based on transcritical CO 2;

number designation in the figures: 1. The system comprises an air inlet channel, 2, an inner duct, 3, an outer duct, 4, a precooler, 5, a compressor, 6, a main combustion chamber, 7, an air turbine, 8, an afterburner, 9, a spray pipe, 10, a liquid CO2 tank, 11, a first switch, 12, a CO2 turbine, 13, a condenser, 14, a pump, 15, a liquid oxygen tank, 16, a second switch, 17 and fuel.

Detailed Description

The operation of the multi-modal combined power cycle system based on transcritical CO2 is described below with reference to fig. 1.

FIG. 1 is a multi-modal combined power cycle system based on transcritical CO2 proposed by the present invention. The working process of the system is as follows: it can be divided into 3 modes (low speed mode, high speed mode and ultra high speed mode).

Turbine mode: the flight Mach number is 0-0.9; closing the first switch 11 and the second switch 16, simultaneously opening the outer duct 3 by regulating the air inlet channel 1, dividing the air into the inner duct 2 and the outer duct 3 after entering the air inlet channel 1, directly entering the air in the outer duct 3 into the main combustion chamber 6, entering the air in the inner duct 2 into the air compressor 5 for boosting, entering the high-pressure air into the main combustion chamber 6 for combustion, applying work to the high-temperature and high-pressure air through the air turbine 7 to provide the work required by the air compressor, and directly passing the high-temperature and high-pressure air after applying work through the spray pipe 9 to generate the required thrust; (ii) a

Transonic mode: the flight Mach number is 0.9-2.5; on the basis of a turbine mode, high-temperature and high-pressure air which does work through an air turbine 7 firstly enters an afterburner 8 for further combustion, and then air with higher temperature and higher pressure passes through a spray pipe 9 to generate huge thrust;

super-precooling mode: the flight Mach number is 2.5-8.0; the first switch 11 and the second switch 16 are opened, liquid CO2 in the liquid CO2 tank 10 enters the precooler 4 to be preheated, the primarily heated CO2 gas is introduced into the main combustion chamber 6 to exchange heat, the temperature is raised, the high-temperature and high-pressure CO2 gas is introduced into the CO2 turbine 12 to do work, the thrust is increased, the CO2 gas after doing work is condensed by the condenser 13, and then the gas is changed into high-pressure liquid CO2 through the pressurization of the pump 14 to be stored in the liquid CO2 tank 10 again; meanwhile, the outer duct 3 is closed by regulating the air inlet 1, and air enters the air inlet 1 and then is cooledThe air enters an inner duct 2, the air in the inner duct 2 is cooled by a precooler 4 and enters an air compressor 5 for boosting, high-pressure air enters a main combustion chamber 6 for combustion, high-temperature and high-pressure air provides work required by the air compressor through an air turbine 7, the high-temperature and high-pressure air after acting is introduced into an afterburning chamber 8 for further combustion, and then the air with higher temperature and higher pressure is used for acting through a spray pipe 9; the liquid oxygen in the liquid oxygen tank 15 is evaporated to O by the condenser 13₂Gas is introduced into the afterburner 8, and the oxygen content in the afterburner 8 is increased, so that combustion is more sufficient, and higher thrust is obtained, and higher flight speed is realized.

Claims

1. A multi-mode combined power cycle system based on transcritical CO2 is characterized by comprising an air inlet channel (1), an inner duct (2), an outer duct (3), a precooler (4), an air compressor (5), a main combustion chamber (6), an air turbine (7), an afterburner (8), a spray pipe (9), a liquid CO2 tank (10), a first switch (11), a CO2 turbine (12), a condenser (13), a pump (14), a liquid oxygen tank (15), a second switch (16) and fuel (17); the outlet of the air inlet channel (1) is divided into a first outlet branch and a second outlet branch, the first outlet branch is connected with the hot-side inlet of the precooler (4) through an inner duct (2), the hot-side outlet of the precooler (4) is connected with the hot-side inlet of the main combustion chamber (6) through the air compressor (5), the hot-side outlet of the main combustion chamber (6) is connected with the hot-side inlet of the afterburner (8) after acting through the air turbine (7), and air in the hot-side outlet of the afterburner (8) is discharged after passing through the spray pipe (9); the second outlet branch is connected with a hot side inlet of the main combustion chamber (6) through an outer duct (3); an outlet of a liquid CO2 tank (10) is connected with a cold side inlet of a precooler (4) after passing through a first switch (11), the cold side outlet of the precooler (4) is connected with a cold side inlet of a main combustion chamber (6), the cold side outlet of the main combustion chamber (6) is connected with a hot side inlet of a condenser (13) after acting through a CO2 turbine (12), and the hot side outlet of the condenser (13) is connected with the inlet of a liquid CO2 tank (10) through a pump (14); an outlet of the liquid oxygen tank (15) is connected with a cold side inlet of the condenser (13) through a second switch (16), a cold side outlet of the condenser (13) is connected with a cold side inlet of the afterburner (8), and a cold side outlet of the afterburner (8) is connected with a hot side inlet of the afterburner (8); the air inlet (1) is an adjustable air inlet.

2. The method of operating a multi-modal combined power cycle system based on transcritical CO2 as claimed in claim 1 comprising the following processes: can be divided into 3 modes;

turbine mode: the flight Mach number is 0-0.9; the first switch (11) and the second switch (16) are closed, meanwhile, the outer duct (3) is opened by regulating the air inlet channel (1), air enters the air inlet channel (1) and then is divided into the inner duct (2) and the outer duct (3), the air in the outer duct (3) directly enters the main combustion chamber (6), the air in the inner duct (2) enters the air compressor (5) to be boosted, high-pressure air enters the main combustion chamber (6) to be combusted, high-temperature and high-pressure air does work through the air turbine (7) to provide work required by the air compressor, and the high-temperature and high-pressure air after doing work directly passes through the spray pipe (9) to generate required thrust;

super-precooling mode: the flight Mach number is 2.5-8.0; the first switch (11) and the second switch (16) are opened, liquid CO2 in a liquid CO2 tank (10) enters a precooler (4) to be preheated, the primarily heated CO2 gas is introduced into a main combustion chamber (6) to exchange heat, the temperature is raised, the high-temperature and high-pressure CO2 gas is introduced into a CO2 turbine (12) to do work, the thrust is increased, the CO2 gas after doing work is condensed through a condenser (13), and then the CO 3583 is changed into high-pressure liquid CO2 through the pressurization of a pump (14) to be stored in the liquid CO2 tank (10) again; meanwhile, the outer duct (3) is closed by regulating the air inlet (1), and air enters the inner duct (2) after entering the air inlet (1)) Air in the inner duct (2) is cooled by the precooler (4) and enters the air compressor (5) to be boosted, high-pressure air enters the main combustion chamber (6) to be combusted, high-temperature and high-pressure air provides work required by the air compressor through the air turbine (7), the high-temperature and high-pressure air after acting is introduced into the afterburning chamber (8) to be further combusted, and then air with higher temperature and higher pressure is used for acting through the spray pipe (9); the liquid oxygen in the liquid oxygen tank (15) is evaporated into O through the condenser (13)₂The gas is introduced into the afterburner (8), and the oxygen content in the afterburner (8) is increased, so that the combustion is more sufficient, and higher thrust is obtained, and higher flight speed is realized.

3. The transcritical CO2 based multi-modal combined power cycle system according to claim 1, wherein: the wall surfaces of the main combustion chamber (6) and the afterburner (8) are respectively provided with a heat exchanger, and the heat exchangers adopt a dividing wall type heat exchanger structure; the precooler (4) and the condenser (13) both adopt a wound tube type heat exchanger structure.

4. The transcritical CO2 based multi-modal combined power cycle system of claim 3, wherein: the super-precooling working mode adopts CO2 as a working medium.