Methanol engine cooling water circulation system and air inlet temperature control method

Abstract

The invention discloses a methanol engine cooling water circulation system and an air inlet temperature control method, and relates to the technical field of methanol engines. An air cooler; a second control valve; a heat exchanger; the inlet of the fresh water pump is connected with the outlet of the fresh water cooler, the outlet of the fresh water pump is connected with the inlet of the cooling water cavity of each cylinder body, the second control valve and the fresh water bypass pipe are connected with the outlet of the cooling water cavity of each cylinder body, and the second control valve is connected with the inlet of the heat exchanger; outlets of the fresh water bypass pipe and the heat exchanger are connected with an inlet of the water return main pipe; an outlet of the water return main pipe is connected with an inlet of the fresh water cooler; a seawater pump; a temperature measuring device; and a control device. The system can increase the air inlet temperature, improve in-cylinder combustion and improve the heat efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol engines, and more specifically, to a methanol engine cooling water circulation system and an intake air temperature control method applied to the methanol engine cooling water circulation system. Background Art

[0002] Methanol engines inject methanol at a certain pressure into the intake manifold or combustion chamber in the form of a liquid atomizer through a methanol injection valve. Methanol is a fuel with a high latent heat of vaporization, requiring it to absorb a significant amount of heat for vaporization and combustion. Especially in northern China, under low load conditions, the intake air temperature is low. After methanol vaporizes and absorbs heat, the ignition temperature in the cylinder cannot be reached, resulting in poor engine combustion, low thermal efficiency, and unstable operation. Furthermore, incomplete combustion can lead to worsening emissions.

[0003] In the prior art, the engine cooling water circulation system consists of freshwater and seawater pipes. The freshwater cooling system utilizes a closed loop (i.e., the cooling medium continuously circulates through the pipes, with the seawater pipes cooling the cooling medium). Water pumped from the freshwater pump enters the cylinder liner cooling water chamber and flows into the main outlet pipe. After passing through an automatic thermostat, if the water temperature exceeds the set temperature, it is cooled by the freshwater cooler and then recirculated into the freshwater pump. If the water temperature is below the set temperature, it is directly recirculated into the freshwater pump. The seawater pipe operates in an open loop (i.e., river and seawater are pumped to various coolers before finally flowing into the river and sea, with the cooling medium always being freshly pumped, rather than continuously circulating through the pipes). The seawater pump pumps the river and seawater through the air cooler, then into the oil cooler, and finally into the freshwater cooler (i.e., cooling the cooling medium in the freshwater cooling system). The water then returns to the source. However, when the ambient temperature is low, the air temperature and cooling water temperature before passing through the air cooler are too low, and the methanol in the cylinder vaporizes and absorbs heat, causing the temperature in the cylinder to drop, failing to reach the ignition point of methanol, resulting in worsened combustion.

[0004] In summary, how to provide a cooling water circulation system that helps to increase intake air temperature, improve combustion in the cylinder, and improve thermal efficiency is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a methanol engine cooling water circulation system, which controls the supercharged air to pass through the air cooler and the heat exchanger in sequence, and according to different working conditions of the engine, controls the first control valve and the second control valve to operate in coordination by detecting the supercharged temperature of the air after supercharging and the intake temperature after heat exchange, so as to control the intake temperature within a set range, effectively increase the intake temperature, improve combustion in the cylinder, and improve thermal efficiency.

[0006] Another object of the present invention is to provide an intake air temperature control method applied to the above-mentioned methanol engine cooling water circulation system.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A methanol engine cooling water circulation system, comprising:

[0009] a first control valve;

[0010] air cooler;

[0011] Second control valve;

[0012] a heat exchanger connected to the air cooler;

[0013] a fresh water pump, the inlet of which is connected to the outlet of the fresh water cooler, the outlet of the fresh water pump is connected to the inlet of the cooling water chamber of each cylinder, the second control valve and the fresh water bypass pipe are both connected to the outlet of the cooling water chamber of each cylinder, the second control valve is connected to the inlet of the heat exchanger, the outlet of the fresh water bypass pipe and the heat exchanger are both connected to the inlet of the return water main pipe, and the outlet of the return water main pipe is connected to the inlet of the fresh water cooler;

[0014] a seawater pump, the outlet of which is respectively connected to the first control valve and the seawater bypass pipe, the first control valve is connected to the inlet of the air cooler, the outlet of the air cooler and the seawater bypass pipe are both connected to the inlet of the oil cooler, and the outlet of the oil cooler is connected to the inlet of the fresh water cooler;

[0015] a temperature measuring device for detecting the boost temperature of the boost air before it enters the air cooler and detecting the intake temperature of the boost air after it passes through the heat exchanger;

[0016] A control device, wherein the first control valve, the air cooler, the second control valve, the heat exchanger, the fresh water pump, the sea water pump and the temperature measuring device are all connected to the control device.

[0017] In one embodiment, a thermostat is provided between the return water main and the inlet of the fresh water cooler, and the thermostat is connected to the control device.

[0018] In one embodiment, the outlet of the thermostat is connected to the inlet of the fresh water cooler and a bypass pipe respectively, and the bypass pipe is connected to the inlet of the fresh water pump.

[0019] In one embodiment, the system further includes a filter disposed at the front end of the inlet of the seawater pump.

[0020] In one embodiment, the system further includes a shell, wherein the first control valve, the air cooler, the second control valve, the heat exchanger, the temperature measuring device and the control device are all arranged in the shell.

[0021] In one embodiment, the temperature measuring device includes a boost temperature sensor provided at the front end of the inlet of the air cooler and an intake air temperature sensor provided at the rear end of the outlet of the heat exchanger, and both the boost temperature sensor and the intake air temperature sensor are connected to the control device.

[0022] An intake air temperature control method, applied to any of the above-mentioned methanol engine cooling water circulation systems, comprising:

[0023] Detecting the boost temperature T and intake air temperature t of the boost air;

[0024] determining whether the boost temperature T is greater than T2; if so, controlling the first control valve to open and the second control valve to close; then determining whether the intake air temperature t is greater than T1 and less than T2; if not, adjusting the opening of the first control valve; and if so, returning to the step of determining whether the intake air temperature t is greater than T1 and less than T2;

[0025] If not, determine whether the boost temperature T is less than T1. If the boost temperature T is greater than or equal to T1, control both the first control valve and the second control valve to be closed. If the boost temperature T is less than T1, control the first control valve to be closed and the second control valve to be opened. Then, determine whether the intake temperature t is greater than T1 and less than T2. If not, adjust the opening of the second control valve. If so, return to the step of determining whether the intake temperature t is greater than T1 and less than T2.

[0026] In one embodiment, the intake air temperature after passing through the heat exchanger is set in advance to be greater than T1 and less than T2.

[0027] When using the methanol engine cooling water circulation system provided by the present invention, the pressurized air (i.e., air after passing through the supercharger) passes through the air cooler and heat exchanger (the temperature of the pressurized air after passing through the heat exchanger is referred to as the intake air temperature t) before entering each cylinder. The control device can pre-set the intake air temperature range to T1 < t < T2. The temperature measuring device can detect the pressurized air temperature T before entering the air cooler and the intake air temperature t after passing through the heat exchanger in real time. The control device can perform control operations based on the detected pressurized air temperature T and intake air temperature t, as well as the set temperature.

[0028] If the charge air temperature T, as measured by the temperature measuring device, is greater than T2, the control device opens the first control valve and closes the second control valve. Water pumped from the seawater pump flows through the air cooler to cool the charge air. Furthermore, because the second control valve is closed, fresh water flows through each cylinder directly into the return water main via the freshwater bypass line. At this point, the heat exchanger is depleted of fluid and ineffective. The temperature measuring device detects the intake air temperature. If the intake air temperature t is greater than T2, the control device increases the opening of the first control valve to increase the seawater flow rate, creating a closed-loop control loop until the intake air temperature t is greater than T1 and less than T2.

[0029] If the charge air temperature T, as detected by the temperature measuring device, is less than T1, the control device closes the first control valve and opens the second control valve. Water pumped from the seawater pump enters the oil cooler through the seawater bypass line. At this point, the air cooler is deactivated, as it has no circulating medium. Furthermore, because the second control valve is open, the fresh water, after cooling the cylinders, reaches a higher temperature. This high-temperature fresh water then passes through the heat exchanger and enters the return water main, heating the charge air. The temperature measuring device detects the intake air temperature. If the intake air temperature t is less than T1, the control device increases the opening of the second control valve to increase the fresh water flow rate, forming a closed-loop control loop until the intake air temperature t is greater than T1 and less than T2.

[0030] If the boost air temperature T detected by the temperature measuring device is greater than T1 and less than T2, the control device controls the closing of both the first and second control valves. Water pumped from the seawater pump enters the oil cooler through the seawater bypass line. At this point, the air cooler has no circulating medium and is inoperative. Furthermore, because the second control valve is also closed, fresh water, after passing through each cylinder, flows directly into the return water main through the freshwater bypass line. At this point, the heat exchanger has no circulating medium and is inoperative, ensuring that the intake air temperature t is greater than T1 and less than T2.

[0031] In summary, the methanol engine cooling water circulation system provided by the present invention controls the pressurized air to pass through the air cooler and the heat exchanger in sequence, and according to different operating conditions of the engine, controls the first control valve and the second control valve to operate in coordination by detecting the pressurized temperature after air supercharging and the intake temperature after heat exchange, so as to control the intake temperature within a set range, effectively increase the intake temperature, improve combustion in the cylinder, and improve thermal efficiency.

[0032] In addition, the present invention also provides an intake air temperature control method applied to the above-mentioned methanol engine cooling water circulation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 This is a schematic structural diagram of the methanol engine cooling water circulation system provided by the present invention;

[0035] Figure 2 This is a schematic diagram of the fresh water circulation pipeline;

[0036] Figure 3 This is a schematic diagram of the seawater cooling pipeline;

[0037] Figure 4 It is a structural diagram of an air cooler, a heat exchanger and a temperature measuring device;

[0038] Figure 5 This is a flow chart of the intake air temperature control method provided by the present invention.

[0039] Figure 1-Figure 5 middle:

[0040] 1 is the seawater bypass pipe, 2 is the first control valve, 3 is the air cooler, 4 is the second control valve, 5 is the heat exchanger, 6 is the fresh water bypass pipe, 7 is the boost temperature sensor, 8 is the intake air temperature sensor, 9 is the seawater pump, 10 is the fresh water pump, 11 is the thermostat, 12 is the bypass pipe, 13 is the filter, 14 is the cylinder block, 15 is the fresh water cooler, 16 is the oil cooler, 17 is the return water main, A is the fresh water circulation pipeline, and B is the seawater cooling pipeline. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] The core of this invention is to provide a methanol engine cooling water circulation system. This system controls the flow of pressurized air through an air cooler and heat exchanger. Based on different engine operating conditions, the system detects the boost temperature after supercharging and the intake air temperature after heat exchange to control the coordinated operation of a first control valve and a second control valve. This ensures the intake air temperature remains within a set range, effectively raising the intake air temperature, improving in-cylinder combustion, and increasing thermal efficiency. Another core of this invention is to provide an intake air temperature control method applicable to the aforementioned methanol engine cooling water circulation system.

[0043] Please refer to Figure 1 This specific embodiment provides a methanol engine cooling water circulation system, including:

[0044] First control valve 2;

[0045] Air cooler 3;

[0046] Second control valve 4;

[0047] a heat exchanger 5 connected to the air cooler 3;

[0048] A fresh water pump 10, the inlet of which is connected to the outlet of a fresh water cooler 15, the outlet of the fresh water pump 10 is connected to the inlet of a cooling water chamber of each cylinder 14, the second control valve 4 and the fresh water bypass pipe 6 are both connected to the outlet of the cooling water chamber of each cylinder 14, the second control valve 4 is connected to the inlet of a heat exchanger 5, the outlets of the fresh water bypass pipe 6 and the heat exchanger 5 are both connected to the inlet of a return water main 17, and the outlet of the return water main 17 is connected to the inlet of the fresh water cooler 15;

[0049] a seawater pump 9, the outlet of which is respectively connected to the first control valve 2 and the seawater bypass pipe 1; the first control valve 2 is connected to the inlet of the air cooler 3; the outlet of the air cooler 3 and the seawater bypass pipe 1 are both connected to the inlet of the oil cooler 16; and the outlet of the oil cooler 16 is connected to the inlet of the fresh water cooler 15;

[0050] A temperature measuring device for detecting the boost temperature of the boost air before it enters the air cooler 3 and the intake air temperature of the boost air after it passes through the heat exchanger 5;

[0051] The control device, the first control valve 2, the air cooler 3, the second control valve 4, the heat exchanger 5, the fresh water pump 10, the sea water pump 9 and the temperature measuring device are all connected to the control device.

[0052] It should be noted that the freshwater pump 10 and the seawater pump 9 are always running, and even if the first control valve 2 and the second control valve 4 are closed, freshwater and seawater are still circulating in the system. Furthermore, components such as the oil cooler 16, the freshwater cooler 15, and the cylinder block 14 require cooling. When no freshwater or seawater is flowing through the air cooler 3 and the heat exchanger 5, it is considered that the air cooler 3 is not cooling the charge air and the heat exchanger 5 is not heating the charge air, that is, the air cooler 3 and the heat exchanger 5 are not functioning.

[0053] In addition, the first control valve 2 and the second control valve 4 can be set as flow regulating valves. In order to solve the problem that the engine is under low load, the efficiency of the supercharger is low, the intake temperature is low, the methanol enters the cylinder and vaporizes and absorbs heat, and the temperature in the cylinder is too low, resulting in low combustion efficiency. The present application adds a heat exchanger 5 to the cooling water circulation pipeline, and uses the high-temperature water passing through the cylinder jacket of each cylinder body 14 to heat the supercharged air. At the same time, by detecting the intake temperature, the opening of the first control valve 2 and the second control valve 4 is adjusted to achieve regulation and control of the intake temperature t. In addition, the system includes a fresh water circulation pipeline A (such as Figure 2 As shown) and seawater cooling pipe B (as Figure 3 shown).

[0054] During actual use, the shape, structure, material, position, etc. of the first control valve 2, air cooler 3, second control valve 4, heat exchanger 5, fresh water pump 10, seawater pump 9, temperature measuring device and control device can be determined according to actual conditions and actual needs.

[0055] When using the methanol engine cooling water circulation system provided by the present invention, the pressurized air (i.e., air after passing through the supercharger) passes sequentially through the air cooler 3 and the heat exchanger 5 (the temperature of the pressurized air after passing through the heat exchanger 5 is referred to as the intake air temperature t) before entering each cylinder 14. The control device can pre-set the intake air temperature range to T1 < t < T2. The temperature measuring device can detect the pressurized air temperature T before entering the air cooler 3 and the intake air temperature t after passing through the heat exchanger 5 in real time. The control device can perform control operations based on the detected pressurized air temperature T and intake air temperature t, as well as the set temperature.

[0056] If the boost air temperature T detected by the temperature measuring device is greater than T2, the control device opens the first control valve 2 and closes the second control valve 4. Water pumped from the seawater pump 9 flows through the air cooler 3 to cool the boost air. Furthermore, since the second control valve 4 is closed, fresh water flows through each cylinder 14 and then directly into the return water main 17 via the freshwater bypass line 6. At this point, the heat exchanger 5 has no circulating medium and is ineffective. The temperature measuring device detects the intake air temperature. If the intake air temperature t is greater than T2, the control device controls the first control valve 2 to open wider to increase the seawater flow rate, forming a closed-loop control loop. This continues until the intake air temperature t is greater than T1 and less than T2. This means that the opening of the first control valve 2 is now in closed-loop control, with the opening adjusted in real time based on the intake air temperature t.

[0057] If the boost air temperature T detected by the temperature measuring device is less than T1, the control device controls the first control valve 2 to close and the second control valve 4 to open. Water pumped from the seawater pump 9 enters the oil cooler 16 through the seawater bypass line 1. At this point, the air cooler 3 has no circulating medium and is ineffective. Furthermore, because the second control valve 4 is open, the fresh water has a high temperature after cooling the cylinders 14. Afterwards, the high-temperature fresh water passes through the heat exchanger 5 and enters the return water main 17, heating the boost air. The temperature measuring device detects the intake air temperature. If the intake air temperature t is less than T1, the control device controls the second control valve 4 to open wider to increase the fresh water flow rate, forming a closed-loop control loop until the intake air temperature t is greater than T1 and less than T2.

[0058] If the boost air temperature T detected by the temperature measuring device is greater than T1 and less than T2, the control device controls both first control valve 2 and second control valve 4 to close. Water pumped from seawater pump 9 enters oil cooler 16 through seawater bypass line 1. At this point, air cooler 3 has no circulating medium and is inoperative. Furthermore, because second control valve 4 is also closed, fresh water passes through each cylinder 14 and directly enters return water main 17 through freshwater bypass line 6. At this point, heat exchanger 5 has no circulating medium and is inoperative, ensuring that intake air temperature t is greater than T1 and less than T2.

[0059] In summary, the methanol engine cooling water circulation system provided by the present invention controls the pressurized air to pass through the air cooler and the heat exchanger in sequence, and according to different operating conditions of the engine, controls the first control valve and the second control valve to operate in coordination by detecting the pressurized temperature after air supercharging and the intake temperature after heat exchange, so as to control the intake temperature within a set range, effectively increase the intake temperature, improve combustion in the cylinder, and improve thermal efficiency.

[0060] In one embodiment, a thermostat 11 is provided between the return water main 17 and the inlet of the fresh water cooler 15. The thermostat 11 is connected to the control device to regulate the temperature of the water flow on the return water main 17 through the thermostat 11 to change the temperature of the water flow entering the fresh water cooler 15.

[0061] In one embodiment, if Figure 1 As shown, the outlet of the thermostat 11 is connected to the inlet of the fresh water cooler 15 and the bypass pipe 12, respectively. The bypass pipe 12 is connected to the inlet of the fresh water pump 10. In other words, water can enter the fresh water cooler 15 after passing through the thermostat 11, or directly enter the fresh water pump 10 through the bypass pipe 12. When the temperature of the water flowing through the return water main 17 is lower than the set temperature of the thermostat 11, the water flows directly into the fresh water pump 10 through the bypass pipe 12. When the temperature of the water flowing through the return water main 17 is higher than the set temperature of the thermostat 11, the water flows through the fresh water cooler 15 and then enters the fresh water pump 10.

[0062] In one embodiment, a filter 13 is further included at the front end of the inlet of the seawater pump 9 to prevent the seawater from flowing into the seawater pump 9 from having too many impurities, which may cause too many impurities to enter the seawater pump 9 and cause the seawater pump 9 to be unable to operate normally.

[0063] In one embodiment, a shell is further included, and the first control valve 2, the air cooler 3, the second control valve 4, the heat exchanger 5, the temperature measuring device and the control device are all arranged in the shell, so that the first control valve 2, the air cooler 3, the second control valve 4, the heat exchanger 5, the temperature measuring device and the control device and other components are effectively protected by the shell, and the shell has waterproof protection to prevent these components from being damaged or unable to operate normally.

[0064] In one embodiment, if Figure 4 As shown, the temperature measuring device includes a boost temperature sensor 7 provided at the front end of the inlet of the air cooler 3 and an intake air temperature sensor 8 provided at the rear end of the outlet of the heat exchanger 5. The boost temperature sensor 7 and the intake air temperature sensor 8 are both connected to the control device. Moreover, the air cooler 3 and the heat exchanger 5 can be connected through an air pipe, the supercharger can be connected to the air cooler 3 through the air pipe, and the heat exchanger 5 can also be connected to other components through the air pipe.

[0065] In addition to the above-mentioned methanol engine cooling water circulation system, the present invention also provides an intake air temperature control method for the methanol engine cooling water circulation system disclosed in the above-mentioned embodiment. The intake air temperature control method has a flow chart as follows: Figure 5 Shown, including:

[0066] Step S1, detecting the boost temperature T and intake air temperature t of the boost air;

[0067] Step S2: Determine whether the boost temperature T is greater than T2. If so, control the first control valve 2 to open and the second control valve 4 to close. Then, determine whether the intake air temperature t is greater than T1 and less than T2. If not, adjust the opening of the first control valve 2. If so, return to the step of determining whether the intake air temperature t is greater than T1 and less than T2.

[0068] If not, determine whether the boost temperature T is less than T1. If the boost temperature T is greater than or equal to T1, control both the first control valve 2 and the second control valve 4 to be closed. If the boost temperature T is less than T1, control the first control valve 2 to be closed and the second control valve 4 to be opened. Then, determine whether the intake temperature t is greater than T1 and less than T2. If not, adjust the opening of the second control valve 4. If so, return to the step of determining whether the intake temperature t is greater than T1 and less than T2.

[0069] In one embodiment, the temperature range of the intake air after passing through the heat exchanger 5 is set in advance to be greater than T1 and less than T2.

[0070] It should be noted that this application controls the intake air temperature t in three different ways, depending on the engine's operating conditions, by detecting the supercharged air temperature T. Specifically, the intake air temperature t detected by the intake air temperature sensor 8 is compared with a target temperature set in advance by the system, and the openings of the first control valve 2 and the second control valve 4 are adjusted to control the intake air temperature t within the target temperature range.

[0071] For example, when the intake air temperature t is too low, the heat exchanger 5 heats the air passing through it using hot water from the freshwater circulation line A, after passing through the cooling water chambers of each cylinder 14. This causes the air cooler 3 to lose its medium flow and become inoperative, thus achieving the supercharged heating function. When the intake air temperature t is too high, the air cooler 3 cools the air passing through it using seawater from the seawater cooling line B. This causes the heat exchanger 5 to lose its medium flow and become inoperative, thus achieving the supercharged intercooling function. When the intake air temperature t is within a pre-set target range, no medium flows through either the air cooler 3 or the heat exchanger 5, meaning that the supercharged air does not require cooling or heating. This state is supercharged without intercooling. This means that by utilizing the aforementioned intake air temperature control method, this system can achieve functions such as supercharged intercooling, supercharged without intercooling, and supercharged heating.

[0072] It should be noted that the first control valve 2 and the second control valve 4 mentioned in this application document are only used to distinguish the difference in position and there is no order of precedence.

[0073] In addition, it should be noted that the orientation or positional relationship indicated by "in and out" etc. in this application is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of simplifying the description and facilitating understanding, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0074] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. Any combination of all the embodiments provided by the present invention is within the scope of protection of this invention and will not be described in detail here.

[0075] The above describes in detail the methanol engine cooling water circulation system and intake air temperature control method provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is intended only to facilitate understanding of the method and core concepts of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A methanol engine cooling water circulation system, characterized in that: include: A first control valve (2); Air cooler (3); A second control valve (4); a heat exchanger (5) connected to the air cooler (3); A fresh water pump (10), the inlet of which is connected to the outlet of the fresh water cooler (15), the outlet of the fresh water pump (10) is connected to the inlet of the cooling water chamber of each cylinder (14), the second control valve (4) and the fresh water bypass pipe (6) are both connected to the outlet of the cooling water chamber of each cylinder (14), the second control valve (4) is connected to the inlet of the heat exchanger (5), the outlet of the fresh water bypass pipe (6) and the heat exchanger (5) are both connected to the inlet of the return water main pipe (17), and the outlet of the return water main pipe (17) is connected to the inlet of the fresh water cooler (15); a seawater pump (9), the outlet of which is respectively connected to the first control valve (2) and the seawater bypass pipe (1); the first control valve (2) is connected to the inlet of the air cooler (3); the outlet of the air cooler (3) and the seawater bypass pipe (1) are both connected to the inlet of the oil cooler (16); and the outlet of the oil cooler (16) is connected to the inlet of the fresh water cooler (15); a temperature measuring device for detecting the boost temperature of the boost air before it enters the air cooler (3) and detecting the intake temperature of the boost air after it passes through the heat exchanger (5); A control device, the first control valve (2), the air cooler (3), the second control valve (4), the heat exchanger (5), the fresh water pump (10), the sea water pump (9) and the temperature measuring device are all connected to the control device.

2. The methanol engine cooling water circulation system according to claim 1, characterized in that: A thermostat (11) is provided between the return water main pipe (17) and the inlet of the fresh water cooler (15), and the thermostat (11) is connected to the control device.

3. The methanol engine cooling water circulation system according to claim 2, characterized in that: The outlet of the thermostat (11) is connected to the inlet of the fresh water cooler (15) and the side branch pipe (12), respectively, and the side branch pipe (12) is connected to the inlet of the fresh water pump (10).

4. The methanol engine cooling water circulation system according to any one of claims 1 to 3, characterized in that: It also includes a filter (13) provided at the front end of the inlet of the seawater pump (9).

5. The methanol engine cooling water circulation system according to any one of claims 1 to 3, characterized in that: It also includes a shell, in which the first control valve (2), the air cooler (3), the second control valve (4), the heat exchanger (5), the temperature measuring device and the control device are all arranged.

6. The methanol engine cooling water circulation system according to any one of claims 1 to 3, characterized in that: The temperature measuring device comprises a boost temperature sensor (7) provided at the front end of the inlet of the air cooler (3) and an intake air temperature sensor (8) provided at the rear end of the outlet of the heat exchanger (5), and both the boost temperature sensor (7) and the intake air temperature sensor (8) are connected to the control device.

7. An intake air temperature control method, applied to the methanol engine cooling water circulation system according to any one of claims 1 to 6, characterized in that: include: Detecting the boost temperature T and intake air temperature t of the boost air; Determine whether the boost temperature T is greater than T2. If so, control the first control valve (2) to open and the second control valve (4) to close. Then, determine whether the intake air temperature t is greater than T1 and less than T2. If not, adjust the opening of the first control valve (2). If so, return to the step of determining whether the intake air temperature t is greater than T1 and less than T2. If not, it is determined whether the boost temperature T is less than T1. If the boost temperature T is greater than or equal to T1, the first control valve (2) and the second control valve (4) are both controlled to be closed. If the boost temperature T is less than T1, the first control valve (2) is controlled to be closed and the second control valve (4) is controlled to be open. Afterwards, it is determined whether the intake air temperature t is greater than T1 and less than T2. If not, the opening of the second control valve (4) is adjusted. If yes, the process returns to the step of determining whether the intake air temperature t is greater than T1 and less than T2.

8. The intake air temperature control method according to claim 7, characterized in that: The target range of the intake air temperature t is set in advance to be greater than T1 and less than T2.

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