阅读说明：本技术 多模式船舶主机余热利用系统及运行方法 (Multi-mode ship main engine waste heat utilization system and operation method ) 是由 张强 赵永杰 骆泽威 于 2020-11-25 设计创作，主要内容包括：本发明公开了一种多模式船舶主机余热利用系统及运行方法,该余热系统采用环保的二氧化碳为单一工质,以船舶主机排出的废气为热源,通过调节模式转换阀,系统可在超临界布雷顿循环、跨临界朗肯循环和喷射制冷循环三种工作模式下进行转换和组合,将主机排出的废气余热转换为电能、热能和冷能。本发明可根据船舶运行海域温度的变化情况和用户对能量的需求,灵活调整系统电能、冷能和热能输出量的大小和类型,即合理利用不同品位的能量,又实现余热利用系统不同种类输出能的解耦,达到了船舶主机节能减排的有益效果。(The invention discloses a multi-mode ship host waste heat utilization system and an operation method thereof. The invention can flexibly adjust the size and type of the output quantity of the electric energy, the cold energy and the heat energy of the system according to the change condition of the temperature of the ship operating sea area and the requirement of a user on the energy, thereby not only reasonably utilizing the energy with different grades, but also realizing the decoupling of the different output energies of the waste heat utilization system and achieving the beneficial effects of energy conservation and emission reduction of the ship main engine.)

1. A multi-mode ship host waste heat utilization system is characterized by comprising a gas heater (1), a flow regulating valve (2), a first expansion machine (3), a second expansion machine (4), a generator (5), a high-temperature water heater (6), a mixing valve (7), a condenser (8), a first mode switching valve (9), a working medium pump (10), a main air compressor (11), a three-way valve (12), a heat regenerator (13), a low-temperature water heater (14), a second mode switching valve (15), an ejector (16), a gas-liquid separator (17), an auxiliary air compressor (18), a throttle valve (19) and an evaporator (20); one branch of the low-temperature side outlet of the gas heater (1) is communicated with the first expander (3) and the high-temperature water heater (6) in sequence; the high-temperature side outlet of the high-temperature water heater (6) is communicated with the first inlet of the mixing valve (7), and the outlet of the mixing valve (7) is communicated with the high-temperature side inlet of the condenser (8); the high-temperature side outlet of the condenser (8) is respectively communicated with inlets of a working medium pump (10) and a main air compressor (11) through a first mode conversion valve (9); outlets of the working medium pump (10) and the main air compressor (11) are communicated with the gas heater (1) through a heat regenerator (13); the other branch of the low-temperature side outlet of the gas heater (1) is communicated with a second expansion machine (4), a heat regenerator (13) and a low-temperature water heater (14) in sequence; the high-temperature side outlet of the low-temperature water heater (14) is respectively communicated with the inlet of the ejector (16) and the second inlet of the mixing valve (7) through a second mode switching valve (15); the outlet of the ejector (16) is connected with the inlet of the gas-liquid separator (17); a liquid outlet branch of the gas-liquid separator (17) is communicated with an injection flow inlet of the ejector (16) sequentially through a throttle valve (19) and an evaporator (20), a gas outlet branch of the gas-liquid separator (17) is communicated with an inlet of the auxiliary compressor (18), and an outlet of the auxiliary compressor (18) is communicated with a second inlet of the mixing valve (7); the first expander (3) and the second expander (4) are both connected with a generator (5).

2. The multi-mode marine main engine waste heat utilization system according to claim 1, wherein the low-temperature side outlet of the gas heater (1) is communicated with the inlets of the first expander (3) and the second expander (4) through a flow regulating valve (2).

3. The multi-mode marine main engine waste heat utilization system according to claim 1, wherein outlets of the working medium pump (10) and the main compressor (11) are communicated with an inlet of a low-temperature side of the heat regenerator (13) through a three-way valve (12).

4. The multi-mode marine main engine waste heat utilization system according to claim 1, wherein the first expander (3), the second expander (4), and the generator (5) are connected through a gearbox.

5. The operation method using the multimode marine main engine waste heat utilization system according to claim 1, wherein the second mode switching valve (15) allows all of the carbon dioxide from the high temperature side outlet of the low temperature water heater (14) to flow into the second inlet of the mixing valve (7) when the cold energy is not required by the marine vessel.

When the ship needs cold energy, the second mode switching valve (15) enables all carbon dioxide at the outlet of the high-temperature side of the low-temperature water heater (14) to flow into the ejector (16), the temperature of the carbon dioxide at the outlet of the high-temperature side of the low-temperature water heater (14) is reduced to the working range required by the ejector (16), then enters a nozzle of the ejector (16) for depressurization to form a low-pressure area, carbon dioxide saturated steam at the low-temperature side outlet of the evaporator (20) is ejected into the ejector (16), the working medium forms gas-liquid two-phase flow at the outlet of the ejector (16), and then is separated by a gas-liquid separator (17), the separated saturated liquid is used as a refrigeration working medium, is reduced to evaporation pressure through a throttle valve (19) and then enters the low-temperature side of an evaporator (20), absorbs the heat of the air at the high-temperature side to reduce the temperature of the air, and then returns to the ejector (16) after outputting cold energy outwards. The saturated steam separated from the gas-liquid separator (17) enters an auxiliary compressor (18) to be pressurized to a condensation pressure, and then flows into a second inlet of the mixing valve (7).

6. The operation method of the multi-mode ship host waste heat utilization system according to claim 1 is adopted, wherein when the seawater temperature is high and is not enough to condense the gaseous carbon dioxide working medium into saturated liquid, the first mode switching valve (9) closes a branch communicated with an inlet of the working medium pump (10), the gaseous carbon dioxide is cooled by the seawater at the high-temperature side of the condenser (8) and then completely enters the main compressor (11), and a supercritical Brayton power cycle is formed, and the specific working process is as follows: the carbon dioxide at the outlet of the first mode switching valve (9) enters a main compressor (11) to be compressed to the highest operating pressure of the system, then enters the low-temperature side of the heat regenerator (13) through the three-way valve (12) to absorb heat, the carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator (13) enters the low-temperature side of the gas heater (1) again, is further heated to the highest temperature of the system by the waste gas of the ship main engine which sequentially flows through the high-temperature side of the gas heater (1), enters the first expander (3) from one part of the carbon dioxide working medium at the outlet of the low-temperature side of the gas heater (1) through one outlet of the flow regulating valve (2) to be expanded to the supercritical pressure, and the output mechanical function is used for driving the generator (5) to provide, then the fresh water enters the high-temperature side of the high-temperature water heater (6) to heat the fresh water at the low-temperature side and output high-temperature heat energy to the outside; the other part of carbon dioxide enters the second expansion machine (4) through the other outlet of the flow regulating valve (2) and expands to the same pressure as the outlet of the first expansion machine (3), the output mechanical function is used for driving the generator (5) to provide electric energy to the outside, then the carbon dioxide enters the high-temperature side of the heat regenerator (13) and gives out heat to the carbon dioxide at the low-temperature side of the heat regenerator, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater (14) to heat hot water at the low-temperature side, and the carbon dioxide flows through the second mode conversion valve (15) after outputting low-temperature heat energy to the outside. Carbon dioxide working media at the outlets of the high-temperature water heater (6) and the second mode conversion valve (15) respectively flow into the first inlet and the second inlet of the mixing valve (7) to be mixed, then enter the high-temperature side of the condenser (8) to be cooled by seawater, and then enter the inlet of the main air compressor (11) through the first mode adjusting valve (9) to complete the whole thermal process.

When the seawater temperature is low, gaseous working media can be condensed to saturated liquid, a first mode conversion valve (9) closes a branch communicated with a main air compressor (11), carbon dioxide entering a high-temperature side of a condenser (8) is condensed to be liquid by seawater at a low-temperature side and then all enters a working medium pump (10), the thermodynamic cycle mode of the system is transcritical power cycle, and the specific working process is as follows: carbon dioxide at the outlet of the first mode conversion valve (9) all flows into a working medium pump (10) and is compressed to the highest pressure of a system, then the carbon dioxide enters the low-temperature side of a heat regenerator (13) through a three-way valve (12) to absorb heat, carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator (13) enters the low-temperature side of a gas heater (1), the carbon dioxide working medium is further heated to the highest temperature of the system by waste gas of a ship main engine at the high-temperature side of the gas heater (1), part of the carbon dioxide working medium at the outlet of the low-temperature side of the gas heater (1) enters a first expansion machine (3) through one outlet of a flow regulating valve (2) to be fully expanded to condensation pressure, and the output mechanical function is used for driving a generator (5) to provide electric energy for the outside, then the carbon dioxide working medium enters; the other part of carbon dioxide enters a second expansion machine (4) through the other outlet of the flow regulating valve (2) and is expanded to the working pressure required by an ejector (16), the output mechanical function is used for driving a generator (5) to provide electric energy to the outside, then the carbon dioxide enters the high-temperature side of a heat regenerator (13) and gives out heat to the carbon dioxide at the low-temperature side of the heat regenerator, the carbon dioxide with the reduced temperature enters the high-temperature side of a low-temperature water heater (14) to heat hot water at the low-temperature side, and the carbon dioxide flows through a second mode conversion valve (15) after outputting low-temperature heat energy to the. Carbon dioxide working media at the outlets of the high-temperature water heater (6) and the second mode conversion valve (15) respectively flow into the first inlet and the second inlet of the mixing valve (7) to be mixed, then enter the high-temperature side of the condenser (8) to be cooled by seawater, and then enter the inlet of the working medium pump (10) through the first mode adjusting valve (9) to complete the whole thermal process.

Technical Field

The invention belongs to the field of energy conversion and utilization, and particularly relates to a multi-mode ship host waste heat utilization system and an operation method.

Background

In the 21 st century, energy crisis and environmental protection have been the hot topics of much attention. Ships play a great role in social and economic development as the most important means of transportation. However, almost half of the fuel energy of the current marine two-stroke diesel engine main unit with advanced performance is not utilized, and is discharged into the environment along with the exhaust gas and the cooling water. This, on the one hand, increases the operating costs of the ship and, on the other hand, also brings about serious environmental problems. In recent years, the research on ship energy saving technology is receiving attention, and how to effectively improve the heat efficiency of the main engine and utilize the exhaust waste heat of the main engine is one of the problems to be solved urgently.

Meanwhile, with the development of travel demands and traffic of people, the number and the shipping rate of ocean passenger ships and large mail ships are far higher than the past. For such large ships, people can not supply various forms of energy such as electric energy, heat energy, cold energy and the like for activities on the ship due to the generally long voyage time. Typically, the electrical energy is provided by a dedicated diesel generator set in the marine engine room; the heat energy is supplied by steam generated by an oil-fired boiler; the cold energy is generally provided by a compression type air conditioning system independently arranged on the ship. Therefore, such ships need to consume a large amount of fuel during sailing. In addition, these energy requirements also have significant seasonal characteristics. For example, more heat energy is required in winter or at lower ambient temperatures, while the demand for cold energy is relatively increased in summer. How to effectively adjust the quantity and the type of the required energy according to the change of seasons and the environmental temperature characteristics of a sailing area so as to improve the daily life quality of crews and passengers is also one of the key research subjects in the related fields.

At present, the efficiency of the waste heat utilization system of the large-scale ship main engine needs to be further improved. In addition, the multi-mode waste heat utilization combined cooling heating and power generation system aiming at the ship navigation characteristics is not researched much. The existing ship waste heat cogeneration system mostly focuses on cogeneration of heat and power or cogeneration of cold and power, rarely considers the characteristics of more changes of ship navigation areas and frequent changes of energy requirements of users, and lacks of a multi-mode adjustable cogeneration system driven by the waste heat of a host.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a multi-mode ship host waste heat utilization system and an operation method, and solves the problems that the existing ship waste heat system cannot change an operation mode according to navigation characteristics and different energy requirements of users, low-grade heat energy cannot be well utilized, and energy consumption is high. The invention aims to solve the defects in the prior art and provides a multi-mode ship main engine waste heat utilization system and an operation method. According to the invention, the environment-friendly carbon dioxide is used as a single working medium, the waste gas discharged by the ship main engine is used as a heat source, and the system can be converted and combined in three working modes of a supercritical Brayton cycle, a transcritical Rankine cycle and an injection refrigeration cycle by adjusting the mode conversion valve, so that the waste heat of the waste gas discharged by the main engine is converted into electric energy, heat energy and cold energy. The system can flexibly adjust the size and type of the output quantity of the electric energy, the cold energy and the heat energy of the system according to the change condition of the temperature of the ship operating sea area and the requirement of a user on the energy, not only can reasonably utilize the energy with different grades, but also can realize the decoupling of the different types of output energy of the waste heat utilization system, and achieves the beneficial effects of energy conservation and emission reduction of the ship main engine.

The technical scheme is as follows: the invention relates to a multi-mode ship host waste heat utilization system which comprises a gas heater, a first expander, a second expander, a generator, a high-temperature water heater, a mixing valve, a condenser, a first mode conversion valve, a working medium pump, a main air compressor, a heat regenerator, a low-temperature water heater, a second mode conversion valve, an ejector, a gas-liquid separator, an auxiliary air compressor, a throttle valve and an evaporator, wherein one branch of a low-temperature side outlet of the gas heater is sequentially communicated with the first expander and the high-temperature water heater; the high-temperature side outlet of the high-temperature water heater is communicated with the first inlet of the mixing valve, and the outlet of the mixing valve is communicated with the high-temperature side inlet of the condenser; the high-temperature side outlet of the condenser is respectively communicated with inlets of the working medium pump and the main gas compressor through a first mode conversion valve; outlets of the working medium pump and the main gas compressor are communicated with the gas heater through a heat regenerator; the other branch of the low-temperature side outlet of the gas heater is sequentially communicated with a second expander, a heat regenerator and a low-temperature water heater; the high-temperature side outlet of the low-temperature water heater is respectively communicated with the inlet of the ejector and the second inlet of the mixing valve through a second mode switching valve; the outlet of the ejector is connected with a gas-liquid separator; a liquid outlet branch of the gas-liquid separator is communicated with an injection flow inlet of the ejector through a throttle valve and an evaporator in sequence, a gas outlet branch of the gas-liquid separator is communicated with an inlet of the auxiliary gas compressor, and an outlet of the auxiliary gas compressor is communicated with a second inlet of the mixing valve; the first expander and the second expander are both connected with a generator.

In order to adjust the flow of the carbon dioxide working medium entering the first expander and the second expander, the low-temperature side outlet of the gas heater is respectively communicated with the inlets of the first expander and the second expander through a flow adjusting valve;

outlets of the working medium pump and the main gas compressor are communicated with an inlet at the low-temperature side of the heat regenerator through a three-way valve;

the first expander, the second expander and the generator are connected through a gear box.

According to the operation method of the multi-mode ship host waste heat utilization system, when a ship does not need cold energy, the second mode conversion valve enables all carbon dioxide from the high-temperature side outlet of the low-temperature water heater to flow into the second inlet of the mixing valve;

when the boats and ships need cold energy, the second mode change-over valve makes the whole ejectors that flow into of the carbon dioxide of low temperature water heater high temperature side export, and its course of operation is: the temperature of carbon dioxide at the outlet of the high-temperature side of the low-temperature water heater is reduced to the working range of the ejector, the carbon dioxide enters a nozzle of the ejector to be reduced in pressure to form a low-pressure area, saturated steam at the outlet of the low-temperature side of the evaporator is injected into the ejector, the working medium forms a gas-liquid two-phase flow at the outlet of the ejector, the gas-liquid two-phase flow is separated through a gas-liquid separator, the separated saturated liquid is used as a refrigeration working medium, the refrigeration working medium is reduced to evaporation pressure through a throttle valve and then enters the low-temperature side of the evaporator, the heat of air at the high-temperature. And the saturated steam separated from the gas-liquid separator enters an auxiliary compressor to be pressurized to a condensation pressure, and then flows into a second inlet of the mixing valve.

The invention relates to an operation method of a multi-mode ship host waste heat utilization system, when the temperature of seawater is higher and is not enough to condense a gaseous carbon dioxide working medium into saturated liquid, a first mode conversion valve closes a branch communicated with an inlet of a working medium pump, gaseous carbon dioxide at an outlet of a high-temperature side of a condenser is cooled by the seawater and then enters a main compressor, at the moment, the thermodynamic cycle mode of the system is supercritical Brayton power cycle, and the specific working process is as follows: and all carbon dioxide at the outlet of the first mode conversion valve enters the main compressor to be compressed to the highest operating pressure of the system, and then enters the low-temperature side of the regenerator through the three-way valve to absorb heat. The carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator enters the low-temperature side of the gas heater, is further heated to the highest temperature of the system by the exhaust gas of the main engine of the ship sequentially flowing through the inlet and the outlet of the high-temperature side of the gas heater, enters the first expander from one outlet of the flow regulating valve to expand to a certain supercritical pressure, and the output mechanical function is used for driving the generator to provide electric energy to the outside and then enters the high-temperature side of the high-temperature water heater to heat the fresh water at the low-temperature side and output high-temperature heat energy to the outside; the other part of carbon dioxide enters a second expander through the other outlet of the flow regulating valve and expands to the same pressure as the outlet of the first expander, the output mechanical function is used for driving the generator to externally provide electric energy, then the carbon dioxide enters the high-temperature side of the heat regenerator to release heat to the carbon dioxide at the low-temperature side of the heat regenerator, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater to heat hot water at the low-temperature side, the hot water flows through a second mode conversion valve after externally outputting low-temperature heat energy, carbon dioxide working media at the outlets of the high-temperature water heater and the second mode conversion valve respectively flow into a first inlet and a second inlet of the mixing valve to be mixed, then the carbon dioxide working media enter the high-temperature side of the condenser to be cooled by seawater, and then.

When the seawater temperature is low, the gaseous working medium can be condensed to saturated liquid, the first mode conversion valve closes the branch communicated with the main compressor, carbon dioxide at the outlet of the high-temperature side of the condenser is condensed to be liquid by the seawater at the low-temperature side and then all enters the working medium pump, the thermodynamic cycle mode of the system is transcritical power cycle, and the specific working process is as follows: carbon dioxide at the outlet of the first mode conversion valve completely flows into a working medium pump and is compressed to the highest operation pressure of a system, then the carbon dioxide enters the low-temperature side of a heat regenerator through a three-way valve to absorb heat, carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator enters the low-temperature side of a gas heater again and is further heated to the highest temperature of the system by ship main engine waste gas flowing through the inlet and the outlet of the high-temperature side of the gas heater in sequence, part of the carbon dioxide working medium at the outlet of the low-temperature side of the gas heater enters a first expander through one outlet of a flow regulating valve to be fully expanded to condensing pressure, and the output mechanical function is used for driving a generator to provide electric energy to the outside and then enters the high-; the other part of carbon dioxide enters the second expander through the other outlet of the flow regulating valve and expands to the working pressure required by the ejector, the output mechanical function is used for driving the generator to externally provide electric energy, then the carbon dioxide enters the high-temperature side of the heat regenerator and releases heat to the carbon dioxide at the low-temperature side of the heat regenerator, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater to heat hot water at the low-temperature side, and the carbon dioxide flows through the second mode conversion valve after externally outputting low-temperature heat energy. Carbon dioxide working media at the outlets of the high-temperature water heater and the second mode conversion valve respectively flow into the first inlet and the second inlet of the mixing valve to be mixed, then enter the high-temperature side of the condenser to be cooled by seawater, and then enter the inlet of the working medium pump through the first mode regulating valve to complete the whole thermodynamic process.

Has the advantages that: according to the invention, the environment-friendly carbon dioxide is used as a single working medium, the waste gas discharged by the ship main engine is used as a heat source, and the system can be converted and combined in three working modes of a supercritical Brayton cycle, a transcritical Rankine cycle and an injection refrigeration cycle by adjusting the mode conversion valve, so that the waste heat of the waste gas discharged by the main engine is converted into electric energy, heat energy and cold energy. The system can flexibly adjust the size and type of the output quantity of the electric energy, the cold energy and the heat energy of the system according to the change condition of the temperature of the ship operating sea area and the requirement of a user on the energy, thereby not only reasonably utilizing the energy with different grades, but also realizing the decoupling of the different types of output energy of the waste heat utilization system and achieving the purposes of energy conservation and emission reduction of a ship host; the invention adopts the double expanders to work in parallel, and adjusts the flow proportion of the working medium at the outlet through the flow adjusting valve, thereby not only ensuring that the system can adjust the quantity of the generated electric energy, heat energy and cold energy, but also performing cascade utilization on the energy of the working medium at the outlet of the expander; according to the invention, the mode conversion valve is arranged at the inlet of the ejector, so that the system can work in a combined cooling heating and power mode or a combined heating and power mode, and the purpose of changing the type of the output energy of the waste heat utilization system is achieved; compared with the traditional organic working medium, the carbon dioxide working medium adopted by the invention can reduce the volume of system components and improve the compactness of the system. In addition, the carbon dioxide has the advantages of good safety, non-flammability, non-corrosiveness, stable chemical property and no pollution to the environment, is suitable for being applied to a ship waste heat utilization system, and can improve the heat efficiency of a ship main engine.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of a supercritical Brayton power cycle of the present invention;

FIG. 3 is a schematic diagram of the transcritical power cycle of the present invention;

fig. 4 is a schematic diagram of the transcritical power and ejector refrigeration combined cycle of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, in the multi-mode ship host waste heat utilization system disclosed by the invention, components forming a transcritical rankine power cycle and a supercritical carbon dioxide brayton cycle comprise a gas heater 1, a flow regulating valve 2, a first expander 3, a second expander 4, a generator 5, a high-temperature water heater 6, a mixing valve 7, a condenser 8, a first mode switching valve 9, a working medium pump 10, a main air compressor 11, a three-way valve 12, a heat regenerator 13 and a low-temperature water heater 14; the components constituting the carbon dioxide injection refrigeration cycle include a second mode converter 15, an ejector 16, a gas-liquid separator 17, an auxiliary compressor 18, a throttle valve 19, and an evaporator 20.

In a transcritical Rankine power cycle and supercritical Brayton power cycle branch, high-temperature waste gas of a ship main engine sequentially passes through an inlet and an outlet on the high-temperature side of a gas heater 1, a low-temperature side inlet of the gas heater 1 is communicated with a low-temperature side outlet of a heat regenerator 13, a low-temperature side outlet of the gas heater 1 is communicated with an inlet of a flow regulating valve 2, a first outlet of the flow regulating valve 2 is communicated with an inlet of a first expander 3, an outlet of the first expander 3 is communicated with a high-temperature side inlet of a high-temperature water heater 6, a high-temperature side outlet of the high-temperature water heater 6 is communicated with a first inlet of a mixing valve 7, a second outlet of the flow regulating valve 2 is communicated with an inlet of a second expander 4, an outlet of the second expander 4 is communicated with a high-temperature side inlet of the heat regenerator 13, a high-temperature side outlet of the heat regenerator 13 is communicated with a high-temperature side inlet of a low-temperature, a first outlet of a second mode conversion valve 15 is communicated with a second inlet of the mixing valve 7, an outlet of the mixing valve 7 is communicated with a high-temperature side inlet of the condenser 8, a high-temperature side outlet of the condenser 8 is communicated with an inlet of the first mode conversion valve 9, one outlet of the first mode conversion valve 9 is communicated with an inlet of the working medium pump 10, an outlet of the working medium pump 10 is communicated with one inlet of a three-way valve 12, the other outlet of the first mode conversion valve 9 is communicated with an inlet of the main compressor 11, an outlet of the main compressor 11 is communicated with the other inlet of the three-way valve 12, and an outlet of the three-way valve 12 is communicated with a low-temperature side inlet of the heat. The first expander 3, the second expander 4 and the generator are connected through a gear box.

In the carbon dioxide injection refrigeration cycle branch, a second outlet of the second mode switching valve 15 is communicated with a working fluid inlet of the ejector 16, an injection flow inlet of the ejector 16 is communicated with a low-temperature side outlet of the evaporator 20, an outlet of the ejector 16 is communicated with an inlet of the gas-liquid separator 17, a liquid outlet of the gas-liquid separator 17 is communicated with an inlet of the throttle valve 19, an outlet of the throttle valve 19 is communicated with a low-temperature side inlet of the evaporator 20, a gas outlet of the gas-liquid separator 17 is communicated with an inlet of the auxiliary compressor 18, and an outlet of the auxiliary compressor 18 is communicated with a second inlet of the mixing valve 7.

The operation process of the invention is as follows:

when the seawater temperature in the ship driving area is high (for example, over 25 ℃), and the seawater is not enough to condense the gaseous carbon dioxide working medium in the condenser 8 to saturated liquid, the first mode conversion valve 9 closes a branch communicated with the inlet of the working medium pump 10, the gaseous carbon dioxide is cooled by the seawater at the high-temperature side of the condenser 8 and then completely enters the main compressor 11, the thermodynamic cycle mode of the system is supercritical Brayton power cycle, and the waste heat utilization system outputs heat energy and electric energy outwards. By adjusting the opening of the flow control valve 2, the flow of the carbon dioxide flowing into the first expander 3 and the second expander 4 can be controlled, so that the output quantity of the high-temperature heat energy and the low-temperature heat energy generated by the high-temperature water heater 6 and the low-temperature water heater 14 can be adjusted.

Specifically, as shown in fig. 2, all the carbon dioxide at the outlet of the first mode switching valve 9 enters the main compressor 11 to be compressed to the maximum operating pressure 16MPa of the system, and then enters the low-temperature side of the regenerator 13 through the three-way valve 12 to absorb the heat released by the carbon dioxide at the high-temperature side. The carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator 13 enters the low-temperature side of the gas heater 1 again, and is further heated to the highest temperature of 230 ℃ of the system by the exhaust gas (the temperature is 270 ℃) of the marine main engine flowing through the high-temperature side of the gas heater 1. A part of carbon dioxide working medium from the outlet of the low-temperature side of the gas heater 1 enters the first expander 3 through an outlet of the flow regulating valve 2 and is fully expanded to 7.8MPa, the output mechanical function is used for driving the generator 5 to provide electric energy to the outside, then the carbon dioxide working medium enters the high-temperature side of the high-temperature water heater 6, fresh water at the low-temperature side is heated to 90 ℃, and high-temperature heat energy is output to the outside; the other part of carbon dioxide enters the second expander 4 through the other outlet of the flow regulating valve 2 to be expanded to 7.4MPa, the output mechanical function is used for driving the generator 5 to provide electric energy to the outside, then enters the high-temperature side of the heat regenerator 13, heat is released to the carbon dioxide at the low-temperature side of the heat regenerator 13, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater 14 to heat hot water at the low-temperature side to 45 ℃, low-temperature heat energy is output to the outside and flows through the second mode switching valve 15, carbon dioxide working media at the outlets of the high-temperature water heater 6 and the second mode switching valve 15 respectively flow into the first inlet and the second inlet of the mixing valve 7 to be converged, then enter the high-temperature side of the condenser 8 to be cooled to 35 ℃ by seawater at the low-temperature side, and then enter the.

When the temperature of the seawater is low (for example, lower than 25 ℃), the gaseous working medium can be condensed to saturated liquid, and the ship does not need cold energy supply, the first mode conversion valve 9 closes a branch communicated with the main compressor 11, and carbon dioxide is condensed into liquid by the seawater at the low temperature side at the high temperature side of the condenser 8 and then completely enters the working medium pump 10; in addition, the second mode switching valve 15 causes all of the carbon dioxide from the high temperature side outlet of the low temperature water heater 14 to flow into the second inlet of the mixing valve 7. At the moment, the thermodynamic cycle mode of the system is transcritical power cycle, and the waste heat utilization system outputs heat energy and electric energy outwards. By adjusting the opening of the flow control valve 2, the flow of the carbon dioxide flowing into the first expander 3 and the second expander 4 can be controlled, so that the output quantity of the high-temperature heat energy and the low-temperature heat energy generated by the high-temperature water heater 6 and the low-temperature water heater 14 can be adjusted.

Specifically, as shown in fig. 3, all the carbon dioxide at the outlet of the first mode switching valve 9 flows into the working medium pump 10, is compressed to the highest operating pressure of the system of 13MPa, and then enters the low-temperature side of the regenerator 13 through the three-way valve 12 to absorb heat. The carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator 13 enters the low-temperature side of the gas heater 1 again, and is further heated to the highest temperature of 230 ℃ of the system by the exhaust gas (the temperature is 270 ℃) of the marine main engine which sequentially flows through the inlet and the outlet of the high-temperature side of the gas heater 1. A part of carbon dioxide working medium from the outlet of the low-temperature side of the gas heater 1 enters the first expander 3 through an outlet of the flow regulating valve 2 and is fully expanded to the condensation pressure of 5.73MPa, the output mechanical function is used for driving the generator 5 to provide electric energy to the outside, then the carbon dioxide working medium enters the high-temperature side of the high-temperature water heater 6, the fresh water at the low-temperature side is heated to 90 ℃, and high-temperature heat energy is output to the outside; the other part of carbon dioxide enters the second expander 4 through the other outlet of the flow regulating valve 2 and is expanded to the working pressure 8.4MPa required by the ejector 16, the output mechanical function is used for driving the generator 5 to provide electric energy to the outside, then the carbon dioxide enters the high-temperature side of the heat regenerator 13, heat is released to the carbon dioxide at the low-temperature side of the heat regenerator 13, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater 14, hot water at the low-temperature side is heated to 45 ℃, the carbon dioxide flows through the second mode conversion valve 15 after outputting low-temperature heat energy to the outside, carbon dioxide working media at the outlets of the high-temperature water heater 6 and the second mode conversion valve 15 respectively flow into the first inlet and the second inlet of the mixing valve 7 to be mixed, then the carbon dioxide working media enter the high-temperature side of the condenser 8 to be.

When the waste heat utilization system works in a transcritical Rankine power cycle, and when the ship needs cold energy, the second mode conversion valve 15 enables carbon dioxide at the high-temperature side outlet of the low-temperature water heater 14 to completely flow into the ejector 16, the thermodynamic cycle mode of the system is a transcritical power and jet refrigeration combined cycle, and the waste heat utilization system outputs electric energy, heat energy and cold energy outwards. By adjusting the opening degree of the flow rate adjustment valve 2, the flow rate of carbon dioxide flowing into the first expander 3 and the second expander 4 can be controlled, thereby achieving the purpose of adjusting the output amount of electric energy, heat energy and cold energy.

Specifically, as shown in fig. 4, all the carbon dioxide at the outlet of the first mode switching valve 9 flows into the working medium pump 10, is compressed to the highest operating pressure of the system of 13MPa, and then enters the low-temperature side of the regenerator 13 through the three-way valve 12 to absorb heat. The carbon dioxide working medium at the outlet of the low-temperature side of the heat regenerator 13 enters the low-temperature side of the gas heater 1 again, and is further heated to the highest temperature of 230 ℃ of the system by the exhaust gas (the temperature is 270 ℃) of the marine main engine which sequentially flows through the inlet and the outlet of the high-temperature side of the gas heater 1. A part of carbon dioxide working medium from the outlet of the low-temperature side of the gas heater 1 enters the first expander 3 through an outlet of the flow regulating valve 2 and is fully expanded to the condensation pressure of 5.73MPa, the output mechanical function is used for driving the generator 5 to provide electric energy to the outside, then the carbon dioxide working medium enters the high-temperature side of the high-temperature water heater 6, the fresh water at the low-temperature side is heated to 90 ℃, and high-temperature heat energy is output to the outside; the other part of carbon dioxide enters the second expander 4 through the other outlet of the flow regulating valve 2 and expands to 8.4MPa of working pressure required by the ejector 16, the output mechanical function is used for driving the generator 5 to provide electric energy for the outside, then the carbon dioxide enters the high-temperature side of the heat regenerator 13 and gives out heat to the carbon dioxide at the low-temperature side of the heat regenerator 13, the carbon dioxide with the reduced temperature enters the high-temperature side of the low-temperature water heater 14 and heats hot water at the low-temperature side to 45 ℃, and low-temperature heat energy is output for the outside. The temperature of the carbon dioxide from the outlet of the high temperature side of the low temperature water heater 14 is reduced to 36 ℃, and then the carbon dioxide enters the nozzle of the ejector 16 to be depressurized, so as to form a low pressure area, and the saturated steam from the outlet of the low temperature side of the evaporator 20 is introduced into the ejector 16. The working medium forms a gas-liquid two-phase flow at the outlet of the ejector 16, then the gas-liquid two-phase flow is separated by the gas-liquid separator 17, the separated saturated liquid as a refrigeration working medium is reduced to evaporation pressure by the throttle valve 19 and enters the low-temperature side of the evaporator 20, the heat of the air at the high-temperature side is absorbed, and the air is cooled to 5 ℃ so as to output cold energy to the outside and then returns to the ejector 16 again. The saturated carbon dioxide steam separated from the gas-liquid separator 17 enters an auxiliary compressor 18 to be pressurized to a condensing pressure; carbon dioxide working media at the outlets of the high-temperature water heater 6 and the auxiliary air compressor 18 respectively flow into a first inlet and a second inlet of the mixing valve 7 to be mixed, then enter a high-temperature side of the condenser 8 to be cooled into saturated liquid by seawater, and then enter an inlet of the working medium pump 10 through the first mode adjusting valve 9 to complete the whole thermodynamic process.