A ship waste heat system and method based on rankine cycle

Abstract

The present application relates to steam engine technical field, specifically to a kind of ship waste heat system and method based on Rankine cycle, including cylinder liner water circulation loop and working medium circulation loop, cylinder liner water circulation loop includes sequentially connected into closed loop circuit engine, steam heater, flue gas heater and evaporator.Working medium circulation loop includes sequentially connected into closed loop circuit liquid storage tank, working medium pump, primary preheater, secondary preheater, evaporator, expander and condenser. Wherein, the cylinder liner water discharged by engine is sequentially heated by steam in steam heater and flue gas in flue gas heater, and then enters the heating channel of evaporator. The working medium exported in liquid storage tank is sequentially heated by low-temperature heat source of primary preheater and medium-temperature heat source of secondary preheater, and then enters the working medium channel of evaporator. The cylinder liner water and working medium in evaporator exchange heat, so that working medium vaporizes and expands, and drives expander to generate electricity.

Description

Technical Field

[0001] This invention relates to the field of steam engine technology, and in particular to a waste heat system and method for ships based on the Rankine cycle. Background Technology

[0002] In ship energy systems, the combustion of fuel in the main engine generates a large amount of waste heat resources in the form of high-temperature flue gas and cylinder liner water. Waste heat recovery and power generation systems in ships have become a hot research topic in marine energy conservation in recent years.

[0003] However, the aforementioned waste heat systems generally use a single heat source as the main heat source, resulting in insufficient utilization of the heat source. Utilizing high-temperature flue gas, steam, etc., to directly exchange heat with the working fluid in the power generation system is highly susceptible to large fluctuations in heat load due to changes in the main engine's operating conditions. Consequently, the power generation capacity of the waste heat recovery system becomes unstable, making it difficult to continuously and stably output electrical energy to the ship's power grid.

[0004] Meanwhile, traditional waste heat recovery systems mostly operate with fixed parameters, lacking a response mechanism to changes in operating conditions. This results in some waste heat not being effectively recovered and utilized in a timely manner during high-load or variable-condition operation, leading to low energy utilization. Furthermore, existing waste heat recovery systems lack sufficient safety guarantees: improper control of operating parameters can easily cause thermal load disturbances to the main engine. For example, abnormal fluctuations in cylinder liner water temperature can affect the thermal balance of the main engine, and in severe cases, may even lead to overheating, cylinder explosion, and other malfunctions.

[0005] Finally, existing waste heat recovery systems lack a coordination mechanism: most of them rely on manual or single control logic, which cannot achieve adaptive and coordinated operation between the ship's main engine, expander and steam energy-consuming equipment, making it difficult to achieve the optimal operating state of the system while ensuring safety. Summary of the Invention

[0006] This invention provides a ship waste heat system and method based on the Rankine cycle, which can at least solve one of the above-mentioned technical problems.

[0007] To address the aforementioned technical problems, one or more embodiments of the present invention provide a marine waste heat system based on the Rankine cycle, comprising a cylinder liner water circulation loop and a working fluid circulation loop. The cylinder liner water circulation loop includes an engine, a steam heater, a flue gas heater, and an evaporator, sequentially connected in a closed loop. The working fluid circulation loop includes a storage tank, a working fluid pump, a primary preheater, a secondary preheater, an evaporator, an expander, and a condenser, sequentially connected in a closed loop. The cylinder liner water discharged from the engine is sequentially heated by steam in the steam heater and flue gas in the flue gas heater before entering the heating channel of the evaporator. The working fluid output from the storage tank is sequentially heated by a low-temperature heat source in the primary preheater and a medium-temperature heat source in the secondary preheater before entering the working fluid channel of the evaporator. After heat exchange between the cylinder liner water and the working fluid in the evaporator, the working fluid vaporizes and expands, driving the expander to generate electricity.

[0008] Furthermore, it also includes a controller. The evaporator is equipped with a first pressure sensor and a first temperature sensor at the outlet of the working fluid channel. A pressure relief pipeline is connected between the inlet of the working fluid channel and the inlet of the condenser, and the pressure relief pipeline is equipped with an on / off valve. The controller is connected to the signals of the first pressure sensor and the first temperature sensor respectively. The controller can control the opening and closing of the on / off valve and can control the frequency of the working fluid pump.

[0009] This configuration allows the on / off valve to be opened when the motor in the expander overspeeds or shuts down, preventing subsequent working fluid from entering the expander. This prevents the heat source in the waste heat system from shutting down too slowly and causing damage due to excessive motor overspeed. In addition, opening the pressure relief line during shutdown allows the expander to stop working more quickly, achieving system quiescence.

[0010] In addition, the physical parameters of the steam discharged from the expander can be comprehensively monitored by the first temperature sensor and the first pressure sensor, thereby determining whether the expander has made full use of the heat absorbed by the working fluid. This allows the flow rate of the working fluid to be adjusted by adjusting the frequency of the working fluid pump, so that the heat of the waste heat system can be fully utilized.

[0011] Furthermore, a second temperature sensor is installed at the inlet of the cylinder liner water in the engine, and the outlet of the cylinder liner water in the engine is connected to the inlet of a regulating valve. One outlet of the regulating valve is connected to a steam heater, and the other outlet is connected to the engine via a return pipe. The controller is connected to the second temperature sensor and can control the flow rate at both outlets of the regulating valve. This configuration can temporarily stop the supply of a portion of the cylinder liner water to the waste heat recovery system when the cylinder liner water recovery temperature is too low, thereby ensuring that the cylinder liner water temperature and engine operating temperature of the engine system remain within the normal range.

[0012] Furthermore, the piping between the evaporator and the engine is connected to the return pipe via a valve joint. A return water heater is connected in series on the piping between the valve joint and the evaporator. The heating channel of the return water heater is connected to the flue gas outlet of the flue gas heater via a three-way valve. This system enables the third-party utilization of the flue gas discharged from the flue gas heater. In other words, when there is excessive heat loss in the cylinder liner water, the flue gas can be used to heat the cylinder liner water entering the engine, preventing the cylinder liner water temperature from being too low and affecting the normal operation of the engine.

[0013] Furthermore, the steam inlet of the steam heater is equipped with a second pressure sensor and a flow valve. The controller is connected to the second pressure sensor and can control the flow rate of the flow valve.

[0014] This embodiment also provides a method for regulating ship waste heat utilization based on the Rankine cycle, used to achieve the regulation of the aforementioned ship waste heat system based on the Rankine cycle, including the following steps:

[0015] Obtain the preset temperature T1 of the first temperature sensor and the preset pressure P1 of the first pressure sensor; obtain the temperature T11 of the first temperature sensor and the pressure P11 of the first pressure sensor in real time; calculate the difference ΔT1 between T1 and T11, and the difference ΔP1 between P1 and P11.

[0016] When ΔT1 is less than 5℃, the working fluid pump frequency decreases; when ΔT1 is greater than 15℃, the working fluid pump frequency increases.

[0017] When ΔP1 is less than 1 bar, the working fluid pump frequency decreases; when ΔP1 is greater than 1.2 bar, the working fluid pump frequency increases.

[0018] Specifically, when the frequency increase or decrease command of the working fluid pump given by △T1 contradicts the frequency increase or decrease command of the working fluid pump given by △P1, the frequency increase or decrease command of the working fluid pump given by △T1 shall be executed.

[0019] Furthermore, the preset temperature T2 of the second temperature sensor and the preset pressure P2 of the second pressure sensor are obtained; the real-time temperature T22 of the second temperature sensor and the pressure P22 of the second pressure sensor are obtained; the difference between T2 and T22, ΔT2, and the difference between P2 and P22, ΔP2, are calculated; when ΔP2 is greater than 0.2 bar, the valve core of the flow valve is activated to reduce the flow rate of steam entering the steam heater;

[0020] When ΔT2 is greater than 10℃, the valve opening of the control valve is adjusted so that some cylinder liner water flows directly back to the engine through the return pipe; when ΔT2 is less than 3℃, the working fluid pump frequency is increased. When the working fluid pump frequency increase command given by ΔT2 contradicts the working fluid pump frequency decrease command given by ΔT1, the working fluid pump frequency decrease command given by ΔT1 is executed first.

[0021] The beneficial effects of one or more of the above technical solutions are as follows:

[0022] This design uses cylinder liner water as the heating medium to form a high-temperature heat source for the evaporator. This high-temperature heat source is generated through a multi-stage heat source gradient heating process. The working fluid used to expand into steam for power generation is also heated by a multi-stage heat source gradient process involving low, medium, and high heat sources. In other words, the dual-cycle multi-stage gradient heating system in this design can fully utilize various types of heat sources in the ship's waste heat system, significantly improving the utilization efficiency of low, medium, and high-grade heat sources, thereby preventing heat waste during ship navigation.

[0023] This scheme, based on the Rankine cycle, utilizes preset temperature T1, preset pressure P1, actual temperature T1, and actual pressure P11 to obtain the difference between T1 and T11, ΔT1, and the difference between P1 and P11, ΔP1. Similarly, it uses preset temperature T2, preset pressure P2, actual temperature T22, and actual pressure P22 to obtain the difference between T2 and T22, ΔT2, and the difference between P2 and P22, ΔP2. This scheme comprehensively monitors various parameters within the waste heat utilization system and adjusts its operating parameters promptly based on changes in these parameters. This ensures efficient waste heat utilization while maintaining the safe operation of the entire ship's main engine system. Furthermore, the scheme assigns different priorities to the adjustment commands for each parameter, creating a coordinated adjustment mechanism that ensures the normal operation of the ship's main engine, expander, and steam-powered equipment while maintaining the overall waste heat system at its optimal efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure in Embodiment 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of the overall structure in Embodiment 2 of the present invention.

[0026] In the diagram, 1. Working fluid pump; 2. Primary preheater; 3. Secondary preheater; 4. Evaporator; 5. Condenser; 6. Liquid storage tank; 7. Expander; 8. Steam heater; 9. Flue gas heater; 10. Engine; 11. On / off valve; 12. First temperature sensor; 13. First pressure sensor; 14. Regulating valve; 15. Second temperature sensor; 16. Three-way valve; 17. Return water heater. Detailed Implementation

[0027] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0028] Example 1

[0029] See Figure 1 This embodiment provides a marine waste heat system based on the Rankine cycle, including a cylinder liner water circulation loop and a working fluid circulation loop. The cylinder liner water circulation loop includes an engine 10, a steam heater 8, a flue gas heater 9, and an evaporator 4, which are connected in a closed loop. The working fluid circulation loop includes a storage tank 6, a working fluid pump 1, a primary preheater 2, a secondary preheater 3, an evaporator 4, an expander 7, and a condenser 5, which are connected in a closed loop. The cylinder liner water discharged from the engine 10 is heated sequentially by steam in the steam heater 8 and flue gas in the flue gas heater 9 before entering the heating channel of the evaporator 4. The working fluid output from the storage tank 6 is heated sequentially by a low-temperature heat source in the primary preheater 2 and a medium-temperature heat source in the secondary preheater 3 before entering the working fluid channel of the evaporator 4. After heat exchange between the cylinder liner water and the working fluid in the evaporator 4, the working fluid vaporizes and expands, driving the expander 7 to generate electricity.

[0030] Specifically, the heat source introduced into the primary preheater 2 is a low-temperature heat source with a temperature of 40℃-60℃. The working fluid entering the primary preheater 2 exchanges heat with the low-temperature heat source, such as the hot water from the air cooler, which initially raises the working fluid's temperature to around 40℃. Specifically, the heat source introduced into the secondary preheater 3 is a medium-temperature heat source with a temperature range of 60℃-80℃. The secondary preheater 3 primarily provides a secondary heating of the working fluid after its initial temperature rise, ensuring that the working fluid entering the secondary preheater 3 is heated to above 60℃ via the medium-temperature heat source.

[0031] Evaporator 4 further heats the working fluid after its secondary heating, causing it to vaporize and expand. Specifically, water in the cylinder liner is used as the heating medium, absorbing heat from the steam and flue gas to heat and vaporize the working fluid in evaporator 4. Expander 7 uses the vaporized working fluid to generate electricity. During power generation, the vaporized working fluid drives a high-speed impeller inside expander 7. Expander 7 is a mature product in this technical field, and its principle and structure will not be described in detail here. Storage tank 6 stores the working fluid. In this embodiment, the working fluid is a non-toxic, non-corrosive organic working fluid that can be heated to between 82-160℃ to complete the liquid-to-gas conversion. Specifically, the working fluid here can be R245fa, R134a, etc.

[0032] Additionally, the steam heater 8 uses ship steam to heat the cylinder liner water; the steam temperature is 110-180℃; the flue gas heater 9 uses the flue gas generated by the ship to heat the working medium after it has been heated by the steam heater 8. In this embodiment, the flue gas temperature entering the flue gas heater 9 is 180-200℃.

[0033] As a specific connection configuration for the working fluid circulation loop: a working fluid pump 1 is connected in series on the connecting pipeline between the liquid storage tank 6 and the primary preheater 2. The working fluid pump 1 transports the working fluid in the liquid storage tank 6 to the primary preheater 2. The primary preheater 2 is connected to the secondary preheater 3 through a pipeline. The secondary preheater is connected to the evaporator 4 through a pipeline. The evaporator 4 is connected to the expander 7 through a pipeline. The outlet of the expander 7 is connected to the liquid storage tank 6 through a pipeline.

[0034] During operation, the working fluid stored in the storage tank 6 is pumped into the primary preheater 2 by the working fluid pump 1. The working fluid in the primary preheater 2 exchanges heat with the incoming heat source, completing the first heating stage. After the first heating, the working fluid temperature is approximately 40°C, at which point it is in a liquid state. The working fluid then enters the secondary preheater for a second preheating, raising its temperature to above 60°C. At this point, the working fluid is still in a liquid state. After the second preheating, the working fluid enters the evaporator 4 to exchange heat with the ship's cylinder liner water, completing the vaporization of the working fluid. At this point, the working fluid is heated to above 82°C and vaporized. The vaporized working fluid then enters the expander 7, where the gas expands rapidly, driving the expander 7 impeller to generate electricity. The generated electricity is then sent to the ship's power grid for use or storage.

[0035] After passing through the expander 7, the gas pressure and temperature decrease instantaneously, and it enters the storage tank 6 for storage. In some embodiments, to ensure that the working fluid entering the storage tank 6 is liquid, a condenser 5 is installed between the storage tank 6 and the expander 7. The inlet end of the condenser 5 is connected to the outlet end of the expander 7, and the outlet end of the condenser 5 is connected to the inlet end of the storage tank 6. The working fluid, after generating electricity by the expander 7, enters the condenser 5 for cooling before entering the storage tank 6 for storage. The working fluid after passing through the expander 7 generally has a pressure of about 1.5-3 bar. The low-pressure gas after expansion is cooled into liquid by seawater or other low-temperature cold source through the condenser 5 and stored in the storage tank 6, forming a closed-loop circulation of the working fluid.

[0036] The specific connection method of the cylinder liner water circulation loop is as follows: the input end of the steam heater 8 is connected to the cylinder liner water output end of the engine 10 through a pipeline; the output end of the steam heater 8 is connected to the heating input end of the flue gas heater 9 through a pipeline; the output end of the flue gas heater 9 is connected to the heat exchange inlet end of the evaporator 4 through a pipeline; and the heat exchange outlet end of the evaporator 4 is connected to the cylinder liner water input end of the engine 10 through a pipeline.

[0037] In this embodiment, the cylinder liner water temperature output by engine 10 is 80-95℃. This cylinder liner water enters steam heater 8 and undergoes a primary heat exchange with the ship's steam entering steam heater 8. In this embodiment, the steam temperature is 100-165℃, and after the steam heat exchange, the cylinder liner water temperature is 100-115℃. After the heat exchange, the cylinder liner water enters flue gas heater 9 and undergoes a secondary heat exchange with the flue gas emitted by the ship. The flue gas temperature entering flue gas heater 9 is 180-200℃. After being heated, the cylinder liner water enters evaporator 4 and undergoes a heat exchange with the working fluid, vaporizing the working fluid entering evaporator 4. After the heat exchange, the temperature of the cylinder liner water decreases, and it re-enters engine 10 for use.

[0038] Through the above work, the heat generated in the ship, such as flue gas, steam, and cylinder liner water, is used to vaporize the working fluid. The vaporized working fluid is then used to drive the expander 7 to generate electricity, effectively utilizing the waste heat generated during the ship's operation and avoiding resource waste.

[0039] In this embodiment, a controller is also included. The evaporator 4 has a first pressure sensor 13 and a first temperature sensor 12 at the outlet of the working fluid channel. A pressure relief pipeline connects the inlet of the working fluid channel and the inlet of the condenser 5, and the pressure relief pipeline is equipped with an on / off valve 11. The on / off valve 11 is normally closed during normal use. When the motor in the expander 7 overspeeds or needs to be shut down, the on / off valve 11 is opened to prevent damage to the motor due to excessive overspeed caused by the heat source shutting down too slowly during the overspeed process. Furthermore, the shutdown process achieves the purpose of opening a bypass, accelerating the stop of the expander 7 and achieving system static state. The controller is connected to the first pressure sensor 13 and the first temperature sensor 12 respectively. The controller can control the opening and closing of the on / off valve 11 and can control the frequency of the working fluid pump 1.

[0040] In some embodiments, the heat source entering the evaporator 4 is only the cylinder liner water (80-95°C), in which case the design pressure before the expander 7 is approximately 6.5-7.2 bar. In other embodiments, when other heat sources such as steam or flue gas are used, the cylinder liner water is heated, in which case the design pressure before the expander 7 is ≥7.2 bar.

[0041] In this embodiment, a second temperature sensor 15 is provided at the inlet of the cylinder liner water in the engine 10, and the outlet of the cylinder liner water in the engine 10 is connected to the inlet of the regulating valve 14. One outlet of the regulating valve 14 is connected to the steam heater 8, and the other outlet is connected to the engine 10 through a return pipe. The controller is connected to the second temperature sensor 15 and can control the opening degree of the two outlets of the regulating valve 14.

[0042] In some embodiments, when the second temperature sensor 15 detects that the temperature of the cylinder liner water entering the engine 10 is below 75°C, the flow rate between the regulating valve 14 and the steam heater 8 needs to be reduced, and the flow rate in the return pipe needs to be increased. Since the required cylinder liner water return temperature varies under different ship loads, the heat load on which the cylinder liner water is used is different under different heat loads. Ships have specific requirements for the temperature of the cylinder liner water under different heat loads. When the return water temperature is too low, the regulating valve 14 is adjusted so that some of the cylinder liner water bypasses the waste heat power generation system and mixes with the cylinder liner water that has passed through the waste heat power generation system to meet the ship's cylinder liner return water temperature requirements.

[0043] In this embodiment, the steam inlet of the steam heater 8 is equipped with a second pressure sensor and a flow valve. The controller is connected to the second pressure sensor and can control the flow rate of the flow valve.

[0044] Ship steam is mainly used for fuel heating and daily life. The amount of steam used by ships is mainly controlled by controlling the steam pressure. When the steam pressure is sufficient, the ship assumes that the amount of steam is sufficient. Therefore, the system is equipped with a flow valve. By monitoring the steam pressure, the amount of steam used can be controlled to ensure that the ship can use steam normally.

[0045] In this embodiment, the temperature of the water in the cylinder liner of the evaporator 4 is greater than 80°C.

[0046] In this embodiment, the heat load of the cylinder liner water is x, the heat loads of the low-temperature heat source and the medium-temperature heat source are y, the heat load of the steam is z, the heat load of the flue gas is w, and the heat lifting efficiency of the ship's waste heat system is defined as a%. , where a is set to be greater than 65 and less than 75.

[0047] In this embodiment, there are multiple expanders 7, which are connected in parallel between the evaporator 4 and the condenser 5.

[0048] This embodiment also provides a method for regulating ship waste heat utilization based on the Rankine cycle, used to achieve the regulation of the aforementioned ship waste heat system based on the Rankine cycle, including the following steps:

[0049] Obtain the preset temperature T1 of the first temperature sensor 12 and the preset pressure P1 of the first pressure sensor 13; obtain the temperature T11 of the first temperature sensor 12 and the pressure P11 of the first pressure sensor 13 in real time; calculate the difference ΔT1 between T1 and T11, and the difference ΔP1 between P1 and P11.

[0050] When ΔT1 is less than 5℃, the working fluid pump 1 reduces its frequency; when ΔT1 is greater than 15℃, the working fluid pump 1 increases its frequency.

[0051] When ΔP1 is less than 1 bar, the working fluid pump 1 reduces its frequency; when ΔP1 is greater than 1.2 bar, the working fluid pump 1 increases its frequency.

[0052] When the frequency increase or decrease command of working fluid pump 1 given by △T1 contradicts the frequency increase or decrease command of working fluid pump 1 given by △P1, the influence of temperature on the vaporization efficiency of working fluid is greater than that of pressure, so the frequency increase or decrease command of working fluid pump 1 given by △T1 is executed first.

[0053] Furthermore, the preset temperature T2 of the second temperature sensor 15 and the preset pressure P2 of the second pressure sensor are obtained; the real-time temperature T22 of the second temperature sensor 15 and the pressure P22 of the second pressure sensor are obtained; the difference between T2 and T22, ΔT2, and the difference between P2 and P22, ΔP2, are calculated; when ΔP2 is greater than 0.2 bar, the valve core of the flow valve is activated to reduce the flow rate of steam entering the steam heater 8;

[0054] When △T2 is greater than 10℃, the opening of the regulating valve is controlled so that some cylinder liner water flows back to the engine directly through the return pipe; when △T2 is less than 3℃, the working fluid pump frequency is increased; when the working fluid pump frequency increase command given by △T2 contradicts the working fluid pump frequency decrease command given by △T1, the working fluid pump frequency decrease command given by △T1 is executed first.

[0055] This embodiment focuses on a 400,000-ton ocean-going bulk carrier, covering the full operating range from low to high load, including normal and abnormal operating conditions. System parameters are determined based on actual ship operating data through thermodynamic calculations and actual testing. Preset values ​​for the first temperature sensor T1: 97℃; the first pressure sensor P1: 8.4 bar; the second temperature sensor T2: 90℃; and the second pressure sensor P2: 1.1 bar.

[0056] Based on the above control instructions, in the waste heat power generation system: T11 should be controlled at 82℃-92℃ (balancing the working fluid vaporization temperature and the optimal operating temperature of the expander), P11 should be controlled at 7.2bar-7.4bar (based on the saturation pressure of the working fluid), T22 should be controlled at 80℃-87℃ (based on the engine cylinder liner water inlet temperature requirement), and P22 should be controlled above 0.9bar (based on the normal operating pressure of the steam system).

[0057] Example 2

[0058] See Figure 2 This embodiment also provides a marine waste heat system based on the Rankine cycle. The difference is that in this embodiment, the pipeline between the evaporator 4 and the engine 10 is connected to the return pipe through a valve node. A return water heater 17 is connected in series on the pipeline between the valve node and the evaporator 4. The heating channel of the return water heater 17 is connected to the flue gas outlet of the flue gas heater 9 through a three-way valve 16.

[0059] Example 3

[0060] Taking a 400,000-ton ocean-going vessel as an example, the cylinder liner water heat load is 2800kW, and the steam volume is 1 ton or more. According to the single heat source mode of the commonly used waste heat utilization system, and calculated based on the low-temperature heat source thermal efficiency of 6%, the system power generation is only about 178kW. In this embodiment, under the mode of low-temperature heat source as the main heat load, multiple heat sources can be utilized. In the system, the cylinder liner water is first heated by steam and then heated by flue gas. At this time, the cylinder liner water temperature rises, and the main heat load that the system can utilize is 4500kW. Calculated based on an efficiency of 7%, the power generation is 310kW, which is about 74% higher than the power generation of a single heat source system. This significantly reduces energy waste, improves the green index of ships, and reduces carbon tax payments.

[0061] Example 4

[0062] Taking a 400,000-ton ore carrier as an example, the ship's usable waste heat includes: cylinder liner water flow of 200 m³ / h, cylinder liner water outlet temperature of 90℃ and return water temperature of 78℃ at 65% load, with a heat load of approximately 2800 kW; waste heat steam of 1.8 t / h, outlet temperature of 165℃, with a heat load of approximately 1000 kW; excess steam after heating in the ship's oil tanks, temperature of 110℃, flow rate of approximately 300 kg / h, with a heat load of approximately 200 kW; in addition, there is water from the air cooler, temperature of approximately 50℃; and ship flue gas at 180℃, with a heat load of approximately 700 kW.

[0063] The working fluid flows at a rate of approximately 5.6 kg / s through working fluid pump 1, with a post-pump temperature of 26°C and a pressure of 7.2 bar. After primary preheating, the temperature reaches 32°C, and after secondary preheating, the temperature reaches 60°C. After passing through evaporator 4, the working fluid temperature is 82°C and the pressure is 6.99 bar. At this point, the high-pressure, high-temperature gas enters expander 7, where it expands to generate approximately 310 kW of electricity. The working fluid pressure then becomes 2.12 bar and the temperature reaches 55°C. After being cooled to 26°C by condenser 5, the working fluid enters the storage tank for continued circulation.

[0064] The specific embodiments described above should not be construed as limiting the scope of protection of this invention. Any alternative modifications or variations made to the embodiments of this invention by those skilled in the art will fall within the scope of protection of this invention. Any aspects not detailed in this invention are well-known to those skilled in the art.

Claims

1. A ship waste heat system based on the Rankine cycle, characterized in that, It includes a cylinder liner water circulation loop and a working fluid circulation loop. The cylinder liner water circulation loop includes an engine, a steam heater, a flue gas heater, and an evaporator connected in sequence to form a closed loop. The working fluid circulation loop includes a liquid storage tank, a working fluid pump, a primary preheater, a secondary preheater, an evaporator, an expander, and a condenser connected in sequence to form a closed loop. The cylinder liner water discharged from the engine is heated sequentially by steam in the steam heater and flue gas in the flue gas heater before entering the heating channel of the evaporator; the working fluid output from the liquid storage tank is heated sequentially by the low temperature heat source of the primary preheater and the medium temperature heat source of the secondary preheater before entering the working fluid channel of the evaporator; after the cylinder liner water in the evaporator exchanges heat with the working fluid, the working fluid vaporizes and expands, driving the expander to generate electricity. The system also includes a controller. The evaporator has a first pressure sensor and a first temperature sensor at the outlet of the working fluid channel. A pressure relief pipeline connects the inlet of the working fluid channel and the inlet of the condenser, and the pressure relief pipeline has an on / off valve. The controller is connected to the first pressure sensor and the first temperature sensor, and can control the opening and closing of the on / off valve and the frequency of the working fluid pump. The inlet of the cylinder liner water in the engine has a second temperature sensor, and the outlet of the cylinder liner water in the engine is connected to the inlet of a regulating valve. One outlet of the regulating valve is connected to a steam heater, and the other outlet is connected to the engine via a return pipe. The controller is connected to the second temperature sensor and can control the opening degree of the regulating valve. The steam inlet of the steam heater has a second pressure sensor and a flow valve. The controller is connected to the second pressure sensor and can control the flow rate of the flow valve.

2. The Rankine cycle-based ship waste heat system according to claim 1, characterized in that, The temperature of the low-temperature heat source is 40℃-60℃, the temperature of the medium-temperature heat source is 60℃-80℃, and the temperature of the water in the cylinder liner of the evaporator is greater than 80℃.

3. The Rankine cycle-based ship waste heat system according to claim 2, characterized in that, The heat load of the cylinder liner water is x, the heat load of the low-temperature heat source and the medium-temperature heat source is y, the heat load of the steam is z, and the heat load of the flue gas is w. The heat lifting efficiency of the ship's waste heat system is defined as a%. ; where 'a' is set to be greater than 65 and less than 75.

4. The Rankine cycle-based ship waste heat system according to claim 1, characterized in that, The pipeline between the evaporator and the engine is connected to the return pipe via a valve node. A return water heater is connected in series on the pipeline between the valve node and the evaporator. The heating channel of the return water heater is connected to the flue gas outlet of the flue gas heater via a three-way valve.

5. The Rankine cycle-based ship waste heat system according to claim 1, characterized in that, The number of expanders is multiple, and the multiple expanders are connected in parallel between the evaporator and the condenser.

6. A method for regulating ship waste heat utilization based on the Rankine cycle, used to regulate the ship waste heat system based on the Rankine cycle as described in claim 1, characterized in that, Includes the following steps: Obtain the preset temperature T1 of the first temperature sensor and the preset pressure P1 of the first pressure sensor; obtain the temperature T11 of the first temperature sensor and the pressure P11 of the first pressure sensor in real time; calculate the difference ΔT1 between T1 and T11, and the difference ΔP1 between P1 and P11. When ΔT1 is less than 5℃, the working fluid pump frequency decreases; when ΔT1 is greater than 15℃, the working fluid pump frequency increases. When ΔP1 is less than 1 bar, the working fluid pump frequency decreases; when ΔP1 is greater than 1.2 bar, the working fluid pump frequency increases. When the frequency increase or decrease command of the working fluid pump given by △T1 contradicts the frequency increase or decrease command of the working fluid pump given by △P1, the frequency increase or decrease command of the working fluid pump given by △T1 shall be executed. Obtain the preset temperature T2 of the second temperature sensor and the preset pressure P2 of the second pressure sensor; obtain the real-time temperature T22 of the second temperature sensor and the pressure P22 of the second pressure sensor; calculate the difference between T2 and T22 ΔT2, and the difference between P2 and P22 ΔP2; when ΔP2 is greater than 0.2 bar, the valve core of the flow valve actuates to reduce the flow rate of steam entering the steam heater; When △T2 is greater than 10℃, the opening of the regulating valve is controlled so that some cylinder liner water flows back to the engine directly through the return pipe; when △T2 is less than 3℃, the working fluid pump frequency is increased; when the working fluid pump frequency increase command given by △T2 contradicts the working fluid pump frequency decrease command given by △T1, the working fluid pump frequency decrease command given by △T1 is executed first.

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