Methanol preheating and catalytic cracking system for methanol engine, ship and control method

Abstract

The invention provides a methanol preheating and catalytic cracking system for a methanol engine, a ship and a control method, and belongs to the technical field of ship methanol engines. The problems that an existing methanol engine is difficult in cold start and methanol gasification are solved. The system comprises a methanol engine, a methanol storage tank, a water storage tank, a heat exchanger, an inlet temperature sensor and an outlet temperature sensor, one passage of a third three-way valve is connected with the waste gas output end of the methanol engine, the other passage of the third three-way valve is connected with another cooling water pipeline, and the methanol output end of the heat exchanger is connected with the methanol input end of the methanol engine. The methanol input end is connected with the methanol storage tank, a methanol pump is arranged on a methanol conveying pipeline between the methanol storage tank and the heat exchanger, two passages of the first three-way valve are arranged between the methanol conveying pipelines, and the inlet temperature sensor and the outlet temperature sensor are respectively arranged at a methanol inlet and a methanol outlet of the heat exchanger. The method is mainly used for starting the methanol engine.

Description

Technical Field

[0001] The invention belongs to the technical field of ship methanol engines, and in particular relates to a methanol preheating and catalytic cracking system for a methanol engine, a ship and a control method. Background Art

[0002] The marine methanol engine is a new type of low-carbon fuel engine. It is based on the marine diesel engine by converting the fuel supply system into a methanol supply system. The gasification effect of methanol directly affects the working performance of the methanol engine. Poor gasification effect will lead to partial combustion of the engine or even misfire. However, the latent heat of gasification of methanol is very large (1109kJ / kg), which is about 4 times that of diesel. The large latent heat of gasification makes it difficult for the engine's methanol fuel supply system to gasify, posing a challenge to the normal operation of the engine. At the same time, the large latent heat of gasification of methanol makes it difficult for the methanol engine to start cold. Therefore, solving the problem of methanol gasification difficulties is an effective way to make the methanol engine run safely and efficiently.

[0003] To solve the problems of methanol gasification difficulties and methanol engine cold start difficulties, methanol is usually preheated by adding glow plugs. The glow plugs are usually installed inside the engine cylinders and use electric heating to heat and vaporize the methanol entering the cylinders. Although the glow plugs can effectively preheat and vaporize methanol, they are not convenient to arrange for engines with smaller cylinder diameters and have high energy consumption, which is not in line with the concept of green environmental protection. Summary of the invention

[0004] In view of this, the present invention aims to propose a methanol preheating and catalytic cracking system, a ship and a control method for a methanol engine, so as to solve the problems of difficulty in cold starting of existing methanol engines and difficulty in methanol gasification.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A methanol preheating and catalytic cracking system for a methanol engine comprises a third three-way valve, a second three-way valve, a methanol engine, a methanol storage tank, a water storage tank, a first three-way valve, a heat exchanger, an inlet temperature sensor and an outlet temperature sensor, wherein one passage of the third three-way valve is connected to the exhaust gas output end of the methanol engine, the second passage is connected to the exhaust gas input end of the heat exchanger, and the other passage is connected to the atmosphere; two cooling water pipelines are connected between the methanol engine and the heat exchanger; two passages of the second three-way valve are respectively installed between one of the cooling water pipelines, and the other passage is connected to the other cooling water pipeline; the methanol output end of the heat exchanger is connected to the methanol input end of the methanol engine, and the methanol input end is connected to the methanol storage tank; a methanol pump is provided on the methanol transportation pipeline between the methanol storage tank and the heat exchanger; two passages of the first three-way valve are arranged between the methanol transportation pipelines, and the other passage is connected to the water storage tank; the inlet temperature sensor and the outlet temperature sensor are respectively arranged at the methanol inlet and outlet of the heat exchanger.

[0007] Furthermore, the flow channel in the heat exchanger adopts a three-layer ring structure design, which is an engine exhaust flow channel, a methanol flow channel and an engine cooling water flow channel from the outside to the inside.

[0008] Furthermore, the flow channel of the heat exchanger radiates 12 ribs from the center outward.

[0009] Furthermore, the exhaust gas flow channel is respectively provided with an exhaust gas inlet manifold and an exhaust gas outlet manifold at both ends, the methanol flow channel is respectively provided with a methanol inlet manifold and a methanol outlet manifold at both ends, and the engine cooling water flow channel is respectively provided with a cooling water outlet manifold and a cooling water inlet manifold at both ends.

[0010] Furthermore, the exhaust gas inlet manifold is connected to the exhaust gas output pipeline of the methanol engine, the exhaust gas outlet manifold is connected to the atmosphere or the exhaust gas processor, the methanol inlet manifold is connected to the methanol output pipeline of the methanol storage tank, the methanol outlet manifold is connected to the methanol input pipeline of the methanol engine, the cooling water outlet manifold is connected to the cooling water input pipeline of the methanol engine, and the cooling water inlet manifold is connected to the cooling water output pipeline of the methanol engine.

[0011] Furthermore, a methanol reforming catalyst is arranged in the heat exchanger.

[0012] Furthermore, the outer side of the heat exchanger is coated with a thermal insulation layer.

[0013] Furthermore, a methanol injector is provided on the exhaust gas output pipeline of the methanol engine, and the methanol injector is connected to the methanol storage tank.

[0014] A ship is provided with a methanol engine having a methanol preheating and catalytic cracking system.

[0015] A method for controlling a methanol preheating and catalytic cracking system of a methanol engine comprises the following steps:

[0016] Step 1: When the methanol engine is operating normally, methanol is preheated, at which time the first three-way valve and the water storage tank are completely closed, and methanol is passed into the heat exchanger;

[0017] Step 2: When the outlet temperature sensor detects that the temperature of methanol flowing out of the heat exchanger is lower than 25°C, the third three-way valve and the second three-way valve are opened, and the cooling water and the engine both flow through the heat exchanger;

[0018] Step 3: The outlet temperature sensor detects that the temperature of the methanol flowing out of the heat exchanger is between 20°C and 50°C, the second three-way valve is opened, and the opening of the third three-way valve is PID controlled by using the temperature detected by the inlet temperature sensor as feedforward and the temperature detected by the outlet temperature sensor as feedback;

[0019] Step 4: The outlet temperature sensor detects that the temperature of the methanol flowing out of the heat exchanger is between 50°C and 60°C, the third three-way valve is closed, and the opening of the second three-way valve is PID controlled by using the temperature detected by the inlet temperature sensor as feedforward and the temperature detected by the outlet temperature sensor as feedback;

[0020] Step 5: The outlet temperature sensor detects that the temperature of the methanol flowing out of the heat exchanger is higher than 60°C, and the third three-way valve and the second three-way valve are closed.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses engine exhaust gas and cooling water to preheat methanol, which can ensure that methanol reaches a sufficient temperature before entering the engine combustion chamber, thereby improving the evaporation efficiency of methanol and improving combustion. Methanol engines have difficulty in cold starting in low-temperature environments. Using engine exhaust gas and cooling water to preheat methanol can increase the temperature of methanol, reduce difficulties during cold starting, improve engine reliability, and further improve the efficiency and power of the methanol engine. Preheating methanol can reduce instability during combustion and improve combustion efficiency, thereby improving the power and economy of the engine. Using exhaust gas and cooling water to preheat methanol can enable the engine to reach its operating temperature faster, reduce fuel consumption, and heat the vehicle compartment more quickly.

[0023] 2. When the methanol engine of the present invention is cold started, methanol catalytic reforming is used to generate hydrogen-rich reformed gas, which helps to make it easier to ignite under low temperature conditions, thereby improving the cold start performance of the methanol engine. The production and use of hydrogen can be carried out at the same time, and there is no need to store high-pressure hydrogen, thereby reducing the risks and costs associated with hydrogen storage and transportation. Methanol reforming hydrogen production has a high energy conversion efficiency because methanol contains abundant hydrogen elements. Methanol can be efficiently converted into hydrogen through the catalytic reforming process, thereby improving the energy utilization efficiency of the entire system. The by-products produced in the methanol reforming process are mainly carbon dioxide and water, which helps to reduce the impact on the environment and reduces the chance of methanol directly contacting engine components, thereby reducing corrosion problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 It is a schematic flow diagram of the methanol preheating and catalytic cracking system for a methanol engine according to the present invention;

[0026] Figure 2 It is a schematic diagram of the flow path of the heat exchanger;

[0027] Figure 3 Schematic diagram of the structure of the heat exchanger.

[0028] 1-the third three-way valve, 2-the second three-way valve, 3-methanol engine, 4-methanol storage tank, 5-methanol pump, 6-water storage tank, 7-the first three-way valve, 8-heat exchanger, 9-inlet temperature sensor, 10-outlet temperature sensor, 11-methanol injector, 12-engine exhaust flow channel, 13-methanol flow channel, 14-engine cooling water flow channel, 15-methanol inlet manifold, 16-exhaust gas inlet manifold, 17-insulation layer, 18-methanol reforming catalyst, 19-exhaust gas outlet manifold, 20-methanol outlet manifold, 21-cooling water outlet manifold, 22-cooling water inlet manifold. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0030] See also Figure 1-3The methanol preheating and catalytic cracking system for a methanol engine includes a third three-way valve 1, a second three-way valve 2, a methanol engine 3, a methanol storage tank 4, a water storage tank 6, a first three-way valve 7, a heat exchanger 8, an inlet temperature sensor 9, and an outlet temperature sensor 10. One of the passages of the third three-way valve 1 is connected to the exhaust gas output end of the methanol engine 3, the second passage is connected to the exhaust gas input end of the heat exchanger 8, and the other passage is connected to the atmosphere. Two cooling water pipelines are connected between the methanol engine 3 and the heat exchanger 8. The second three-way valve 2 Two of the passages are respectively installed between one of the cooling water pipelines, and the other passage is connected to the other cooling water pipeline. The methanol output end of the heat exchanger 8 is connected to the methanol input end of the methanol engine 3, and the methanol input end is connected to the methanol storage tank 4. A methanol pump 5 is provided on the methanol storage tank 4 and the methanol delivery pipeline of the heat exchanger 8. Two of the passages of the first three-way valve 7 are arranged between the methanol delivery pipeline, and the other passage is connected to the water storage tank 6. The inlet temperature sensor 9 and the outlet temperature sensor 10 are respectively arranged at the methanol inlet and outlet of the heat exchanger 8.

[0031] The methanol fuel flows out of the methanol storage tank 4, is pressurized by the methanol pump 5, flows through the first three-way valve 7, and then enters the heat exchanger 8 for preheating or catalytic reforming. The preheated or catalytically reformed methanol fuel is supplied to the fuel system of the methanol engine 3, thereby realizing the fuel supply of the methanol engine 3. An inlet temperature sensor 9 and an outlet temperature sensor 10 are installed on the methanol inlet and outlet sides of the heat exchanger 8 to detect the temperature of the methanol at the inlet and outlet of the heat exchanger 8. In the engine cooling water pipeline, the cooling water flows out of the methanol engine 3 and flows through the first three-way valve 7. The exhaust gas from the methanol engine 3 is discharged through the third three-way valve 1, and then through the heat exchanger 8 and discharged into the atmosphere or the exhaust gas treatment system. A methanol injector 11 is installed on the inlet side of the heat exchanger of the exhaust gas pipeline of the methanol engine 3. The methanol injector 11 is connected to the methanol storage tank 4 and is used to supplement the combustion of methanol under cold start conditions to provide heat for the methanol catalytic reforming reaction. When the methanol engine 3 is cold started, the engine is supplied with hydrogen-rich reformed gas by methanol catalytic reforming to promote combustion during cold start. At this time, the first three-way valve 7 is opened on the water storage tank 6 side, so that methanol and water enter the heat exchanger 8 together for catalytic reforming reaction. Since the cooling water temperature is low during cold start of the methanol engine 3, the ECU controls the heat exchanger 8 side of the second three-way valve 2 to be completely closed to prevent low-temperature cooling water from flowing through the heat exchanger, and controls the heat exchanger 8 side of the third three-way valve 1 to be fully opened to allow all the exhaust gas of the methanol engine 3 to flow out. Through the heat exchanger 8, the outlet temperature sensor 10 monitors the temperature of the reformed gas flowing out of the heat exchanger 8. When the reformed gas temperature is lower than 250°C, the ECU controls the methanol injector to inject methanol into the exhaust gas pipeline of the methanol engine 3, and ignites the methanol with the temperature of the exhaust gas, thereby realizing the supplementary combustion of methanol to provide heat for the methanol catalytic reforming reaction. When the temperature monitored by the outlet temperature sensor 10 is higher than 300°C, the ECU controls the opening of the third three-way valve 1 on the heat exchanger 8 side to gradually decrease at intervals of 5%, so as to realize the control of the catalytic reforming temperature.

[0032] like Figure 1As shown, the system mainly includes a methanol fuel supply pipeline, an engine cooling water pipeline, and an engine exhaust pipeline. In the methanol fuel supply pipeline, the methanol fuel flows out from the methanol storage tank 4, is pressurized by the methanol pump 5, flows through the first three-way valve 7, and then enters the heat exchanger 8 for preheating or catalytic reforming. The methanol fuel after preheating or catalytic reforming is supplied to the fuel system of the methanol engine 3, thereby realizing the fuel supply of the methanol engine. An inlet temperature sensor 9 and an outlet temperature sensor 10 are installed on the methanol inlet and outlet sides of the heat exchanger 8 for detecting the temperature of the methanol at the inlet and outlet of the heat exchanger 8. In the engine cooling water pipeline, the cooling water flows out of the methanol engine 3 and flows through the second three-way valve 2, and then flows back to the methanol engine 3 after passing through the heat exchanger 8, completing the methanol. The preheating of alcohol and the cooling water circulation of the methanol engine 3, the second three-way valve 2 is an electronically controlled flow control valve, which can control the cooling water flow of the methanol engine 3 flowing through the heat exchanger 8 according to the command of the ECU, so as to realize the control of the methanol preheating temperature. In the engine exhaust gas pipeline, the exhaust gas is discharged from the engine and passes through the third three-way valve 1, and then passes through the heat exchanger 8 and is discharged into the atmosphere or the exhaust gas treatment system. Similar to the engine cooling water pipeline, the third three-way valve 1 is also an electronically controlled flow control valve, which can control the exhaust gas flow through the heat exchanger 8 according to the command of the ECU. A methanol injector 11 is installed on the inlet side of the heat exchanger 8 of the engine exhaust gas pipeline. The methanol injector 11 is connected to the methanol storage tank 4 and is used to supplement the combustion of methanol under cold start conditions to provide heat for the methanol catalytic reforming reaction.

[0033] When the methanol engine is cold started, the engine is supplied with hydrogen-rich reformed gas by methanol catalytic reforming to promote combustion during cold start. At this time, the water storage tank side of the first three-way valve 7 is opened to allow methanol and water to enter the heat exchanger 8 for catalytic reforming reaction. Since the cooling water temperature is low when the engine is cold started, the ECU controls the heat exchanger side of the second three-way valve 2 to be completely closed to prevent low-temperature cooling water from flowing through the heat exchanger 8, and controls the heat exchanger side of the third three-way valve 1 to be fully opened to allow all engine exhaust gas to flow through the heat exchanger 8. At the same time, the outlet temperature sensor 10 monitors the reformed gas temperature flowing out of the heat exchanger. When the reformed gas temperature is lower than 250°C, the ECU controls the methanol injector 11 to inject methanol into the engine exhaust gas pipeline to ignite methanol at the temperature of the exhaust gas, thereby realizing the supplementary combustion of methanol to provide heat for the methanol catalytic reforming reaction. When the temperature monitored by the outlet temperature sensor 10 is higher than 300°C, the ECU controls the opening of the heat exchanger side of the third three-way valve 1 to gradually decrease at intervals of 5% to achieve control of the catalytic reforming temperature.

[0034] When the methanol engine is operating normally, due to the fast propagation speed of hydrogen flame, if the hydrogen-rich reforming gas is continued to be burned at this time, it is easy to cause abnormal combustion phenomena such as engine knock. Therefore, the engine is running with pure methanol as fuel. At this time, the methanol needs to be preheated to reduce the problem of methanol gasification difficulty. At this time, the first three-way valve 7 on the water storage tank side is completely closed, and only pure methanol is passed into the heat exchanger 8. When the outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger is lower than 25°C, the second three-way valve 2 and the third three-way valve 1 are fully opened, and all the cooling water and engine exhaust gas flow through the heat exchanger 8; when the temperature detected by the outlet temperature sensor 10 is between 25°C and 50°C, the third three-way valve 1 is fully opened. The second three-way valve 2 is fully opened, and the opening of the third three-way valve 1 is PID controlled with the temperature of the inlet temperature sensor 9 as feedforward and the temperature of the outlet temperature sensor 10 as feedback; when the temperature detected by the outlet temperature sensor 10 is between 50°C and 60°C, the third three-way valve 1 is fully closed, and at the same time, the opening of the second three-way valve 2 is PID controlled with the temperature of the inlet temperature sensor 9 as feedforward and the temperature of the outlet temperature sensor 10 as feedback; when the temperature detected by the outlet temperature sensor 10 is higher than 60°C, the second three-way valve 2 and the third three-way valve 1 are both fully closed. Through this control strategy, the temperature of methanol supplied to the engine can be controlled within a reasonable range.

[0035] Preheating methanol using exhaust gas and cooling water from the methanol engine 3 can ensure that the methanol reaches a sufficient temperature before entering the combustion chamber of the methanol engine 3, thereby improving the evaporation efficiency of the methanol and improving combustion. The methanol engine 3 has difficulty in cold starting in a low-temperature environment. Preheating methanol using exhaust gas and cooling water from the methanol engine 3 can increase the temperature of the methanol, reduce the difficulty during cold starting, improve the reliability of the engine, and further improve the efficiency and power of the methanol engine. Preheating methanol can reduce the instability during the combustion process, improve the combustion efficiency, and thus improve the power and economy of the engine. Preheating methanol using exhaust gas and cooling water can enable the engine to reach its operating temperature faster, reduce fuel consumption, and can start more quickly. The interior of the vehicle is heated and methanol catalytic reforming is used to produce hydrogen-rich reformed gas, which helps to ignite more easily under low temperature conditions, thereby improving the cold start performance of the methanol engine 3. The production and use of hydrogen can be carried out at the same time, and there is no need to store high-pressure hydrogen, thereby reducing the risks and costs associated with hydrogen storage and transportation. Methanol reforming hydrogen production has a high energy conversion efficiency because methanol contains rich hydrogen elements. Methanol can be efficiently converted into hydrogen through the catalytic reforming process, thereby improving the energy utilization efficiency of the entire system. The by-products produced in the methanol reforming process are mainly carbon dioxide and water, which helps to reduce the impact on the environment and reduces the chance of methanol directly contacting engine components, thereby reducing corrosion problems.

[0036] Furthermore, the flow channel in the heat exchanger 8 adopts a three-layer annular structure design, which is an engine exhaust flow channel 12, a methanol flow channel 13 and an engine cooling water flow channel 14 from the outside to the inside. The flow channel of the heat exchanger 8 radiates 12 ribs from the center to the outside, and the angle between each rib is 30°. A methanol reforming catalyst 18 is provided in the heat exchanger 8. The flow channel is made of a material with a high thermal conductivity. The methanol flow channel 13 is in the middle position and can exchange heat with the engine aircraft and cooling water at the same time. The flow channel radiates 12 ribs from the center to the outside to enhance the heat exchange problem. The outer wall surface of the heat exchanger 8 is covered with an insulation layer 17, which can reduce heat loss. The wall surface of the methanol flow channel 13 of the heat exchanger 8 is coated with a methanol reforming catalyst 18, which can be used for methanol catalytic reforming reaction.

[0037] Furthermore, an exhaust gas inlet manifold 16 and an exhaust gas outlet manifold 19 are respectively installed at both ends of the exhaust gas flow channel 12, a methanol inlet manifold 15 and a methanol outlet manifold 20 are respectively installed at both ends of the methanol flow channel 13, and a cooling water outlet manifold 21 and a cooling water inlet manifold 22 are respectively installed at both ends of the engine cooling water flow channel 14.

[0038] Furthermore, the exhaust gas inlet manifold 16 is connected to the exhaust gas output pipeline of the methanol engine 3, the exhaust gas outlet manifold 19 is connected to the atmosphere or the exhaust gas processor, the methanol inlet manifold 15 is connected to the methanol output pipeline of the methanol storage tank 4, the methanol outlet manifold 20 is connected to the methanol input pipeline of the methanol engine 3, the cooling water outlet manifold 21 is connected to the cooling water input pipeline of the methanol engine 3, and the cooling water inlet manifold 22 is connected to the cooling water output pipeline of the methanol engine 3.

[0039] Furthermore, a methanol injector 11 is provided on the exhaust gas output pipeline of the methanol engine 3, and the methanol injector 11 is connected to the methanol storage tank 4, and is used to supplement the combustion of methanol under cold start conditions to provide heat for the methanol catalytic reforming reaction.

[0040] Furthermore, a method for controlling a methanol preheating and catalytic cracking system of a methanol engine comprises the following steps:

[0041] Step 1: When the methanol engine 3 is operating normally, methanol is preheated, at which time the first three-way valve 7 and the water storage tank 6 are completely closed, and methanol is passed into the heat exchanger 8;

[0042] Step 2: When the outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger 8 is lower than 25°C, the third three-way valve 1 and the second three-way valve 2 are opened, and the cooling water and the engine both flow through the heat exchanger 8;

[0043] Step 3: The outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger 8 is between 20°C and 50°C, the second three-way valve 2 is opened, and the opening of the third three-way valve 1 is PID controlled by using the temperature detected by the inlet temperature sensor 9 as feedforward and the temperature detected by the outlet temperature sensor 10 as feedback;

[0044] Step 4: The outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger 8 is between 50°C and 60°C, the third three-way valve 1 is closed, and the opening of the second three-way valve 2 is PID controlled by using the temperature detected by the inlet temperature sensor 9 as feedforward and the temperature detected by the outlet temperature sensor 10 as feedback;

[0045] Step 5: The outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger 8 is higher than 60° C., and the third three-way valve 1 and the second three-way valve 2 are closed.

[0046] When the methanol engine 3 is operating normally, the methanol is preheated to reduce the problem of methanol gasification difficulties. At this time, the first three-way valve 7 on the water storage tank 6 side is completely closed, and only pure methanol is passed into the heat exchanger 8. When the outlet temperature sensor 10 detects that the temperature of the methanol flowing out of the heat exchanger 8 is lower than 25°C, the third three-way valve 1 and the second three-way valve 2 are fully opened, and all the cooling water and engine exhaust gas flow through the heat exchanger 8; when the temperature detected by the outlet temperature sensor 10 is between 25°C and 50°C, the second three-way valve 2 is fully opened, using the temperature of the inlet temperature sensor 9 as the feedforward and the outlet temperature sensor 9 as the feedforward. The temperature of the temperature sensor 10 is used as feedback to perform PID control on the opening of the third three-way valve 1; when the temperature detected by the outlet temperature sensor 10 is between 50°C and 60°C, the third three-way valve 1 is completely closed, and at the same time, the opening of the second three-way valve 2 is PID controlled with the temperature of the inlet temperature sensor 9 as feedforward and the temperature of the outlet temperature sensor 10 as feedback; when the temperature detected by the outlet temperature sensor is higher than 60°C, the second three-way valve 2 and the third three-way valve 1 are both completely closed. Through this control strategy, the temperature of methanol supplied to the engine can be controlled within a reasonable range.

[0047] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A methanol preheating and catalytic cracking system for a methanol engine, characterized by: The invention comprises a third three-way valve (1), a second three-way valve (2), a methanol engine (3), a methanol storage tank (4), a water storage tank (6), a first three-way valve (7), a heat exchanger (8), an inlet temperature sensor (9) and an outlet temperature sensor (10), wherein one passage of the third three-way valve (1) is connected to the exhaust gas output end of the methanol engine (3), a second passage is connected to the exhaust gas input end of the heat exchanger (8), and another passage is connected to the atmosphere; two cooling water pipelines are connected between the methanol engine (3) and the heat exchanger (8); two passages of the second three-way valve (2) are respectively connected to the exhaust gas output end of the methanol engine (3); It is installed between one of the cooling water pipelines, and the other passage is connected to the other cooling water pipeline. The methanol output end of the heat exchanger (8) is connected to the methanol input end of the methanol engine (3), and the methanol input end is connected to the methanol storage tank (4). A methanol pump (5) is provided on the methanol storage tank (4) and the methanol delivery pipeline of the heat exchanger (8). Two passages of the first three-way valve (7) are arranged between the methanol delivery pipelines, and the other passage is connected to the water storage tank (6). The inlet temperature sensor (9) and the outlet temperature sensor (10) are respectively arranged at the methanol inlet and outlet of the heat exchanger (8).

2. The methanol preheating and catalytic cracking system for a methanol engine according to claim 1, characterized in that: The flow channels in the heat exchanger (8) are designed with a three-layer annular structure, which are, from the outside to the inside, an engine exhaust flow channel (12), a methanol flow channel (13) and an engine cooling water flow channel (14).

3. The methanol preheating and catalytic cracking system for a methanol engine according to claim 2, characterized in that: The flow channel of the heat exchanger (8) has 12 ribs radiating outward from the center.

4. The methanol preheating and catalytic cracking system for a methanol engine according to claim 2, characterized in that: An exhaust gas inlet manifold (16) and an exhaust gas outlet manifold (19) are respectively installed at both ends of the exhaust gas flow channel (12), a methanol inlet manifold (15) and a methanol outlet manifold (20) are respectively installed at both ends of the methanol flow channel (13), and a cooling water outlet manifold (21) and a cooling water inlet manifold (22) are respectively installed at both ends of the engine cooling water flow channel (14).

5. The methanol preheating and catalytic cracking system for a methanol engine according to claim 4, characterized in that: The exhaust gas inlet manifold (16) is connected to the exhaust gas output pipeline of the methanol engine (3), the exhaust gas outlet manifold (19) is connected to the atmosphere or the exhaust gas processor, the methanol inlet manifold (15) is connected to the methanol output pipeline of the methanol storage tank (4), the methanol outlet manifold (20) is connected to the methanol input pipeline of the methanol engine (3), the cooling water outlet manifold (21) is connected to the cooling water input pipeline of the methanol engine (3), and the cooling water inlet manifold (22) is connected to the cooling water output pipeline of the methanol engine (3).

6. The methanol preheating and catalytic cracking system for a methanol engine according to claim 2, characterized in that: A methanol reforming catalyst (18) is provided on the inner wall of the methanol flow channel (13).

7. The methanol preheating and catalytic cracking system for a methanol engine according to claim 2, characterized in that: The outer side of the heat exchanger (8) is coated with a thermal insulation layer (17).

8. The methanol preheating and catalytic cracking system for a methanol engine according to claim 5, characterized in that: A methanol injector (11) is provided on the exhaust gas output pipeline of the methanol engine (3), and the methanol injector (11) is connected to the methanol storage tank (4).

9. A ship, characterized in that: A methanol engine with a methanol preheating and catalytic cracking system according to any one of claims 1 to 8 is installed in the ship.

10. A method for controlling a methanol preheating and catalytic cracking system of a methanol engine according to any one of claims 1 to 8, characterized in that: It includes the following steps: Step 1: When the methanol engine (3) is operating normally, methanol is preheated, at which time the first three-way valve (7) and the water storage tank (6) are completely closed, and methanol is passed into the heat exchanger (8); Step 2: When the outlet temperature sensor (10) detects that the temperature of the methanol flowing out of the heat exchanger (8) is lower than 25°C, the third three-way valve (1) and the second three-way valve (2) are opened, and the cooling water and the engine both flow through the heat exchanger (8); Step 3: The outlet temperature sensor (10) detects that the temperature of the methanol flowing out of the heat exchanger (8) is between 20°C and 50°C, the second three-way valve (2) is opened, and the opening of the third three-way valve (1) is PID controlled by using the temperature detected by the inlet temperature sensor (9) as feedforward and the temperature detected by the outlet temperature sensor (10) as feedback; Step 4: The outlet temperature sensor (10) detects that the temperature of the methanol flowing out of the heat exchanger (8) is between 50°C and 60°C, the third three-way valve (1) is closed, and the opening of the second three-way valve (2) is PID controlled by using the temperature detected by the inlet temperature sensor (9) as feedforward and the temperature detected by the outlet temperature sensor (10) as feedback; Step 5: The outlet temperature sensor (10) detects that the temperature of the methanol flowing out of the heat exchanger (8) is higher than 60°C, and the third three-way valve (1) and the second three-way valve (2) are closed.

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