Natural gas engine egr heating control method, device, system

Abstract

The application provides a natural gas engine EGR heating control method, device and system. The method comprises the following steps: detecting and obtaining an ambient temperature value of an engine; obtaining a preset working mode of a control valve according to the ambient temperature value and a mapping relationship between the ambient temperature value and the preset working mode, wherein the preset working mode comprises a first working mode and a second working mode; in the first working mode, the control valve starts a first backwater pipeline to perform backwater heating on an EGR valve and an EGR valve seat; and in the second working mode, the control valve starts the first backwater pipeline and a second backwater pipeline to perform backwater heating on the EGR valve, the EGR valve seat and an air inlet connecting elbow. The application can effectively prevent icing of an EGR mixer and an air inlet pipeline at the rear end of the mixer.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and more specifically, to a method, apparatus, and system for EGR heating control of a natural gas engine. Background Technology

[0002] In recent years, the energy crisis and environmental pollution have placed stricter demands on the traditional internal combustion engine industry, and global requirements for energy conservation, emission reduction, and environmental protection are increasing. Faced with the energy crisis, the trend is forcing researchers to find alternative energy sources and develop new energy industries.

[0003] Natural gas, with its abundant global reserves, low price, and clean combustion, is the optimal alternative to traditional fossil fuels. In the heavy-duty commercial vehicle sector, natural gas is considered to be the second most important fuel source after diesel. Equivalent combustion, exhaust gas recirculation (EGR), and three-way catalytic converters are the commonly used technologies in natural gas engines for heavy-duty trucks that meet China VI emission standards. However, because natural gas combustion products contain a large amount of water, when the engine adopts EGR technology, the gas passing through the EGR pipeline is mainly composed of carbon dioxide and water, with the water primarily in gaseous form. This water in the EGR gas enters the intake system in gaseous form. When the vehicle operates in extremely cold environments, the gaseous water in the intake system condenses into liquid water, then freezes into ice, and adheres to the intake pipes. This reduces the cross-sectional area of ​​the gas flow in the pipes, leading to insufficient engine intake, performance degradation, and in severe cases, ice blockage of the intake pipes, preventing gas from entering the cylinders, causing the engine to stall and fail to start.

[0004] In another scenario, when the engine is operating under low load, the EGR rate is very low or zero, and the EGR valve is slightly open or closed. Since most EGR valves on the market are mechanical lift valves, even when the valve body and seat are fully closed, slight leakage can still occur. When the leaked gas, carrying a certain temperature, mixes with fresh air in the mixer, the water vapor in the EGR system will condense due to the low air temperature and the very low temperature of the valve arm. During prolonged low-load operation, especially in cold winter conditions in northern regions, this can lead to water leakage. When a vehicle is loading or unloading cargo, it may idle or the driver may turn on the heater while idling. If there is a slight leak in the EGR valve, the leakage flow is too small to carry the generated condensate into the cylinder for mixing and combustion. The condensate tends to adhere to the EGR mixer and freeze, or freeze on the pipe walls after the mixer. Over time, as the ice accumulates, the EGR mixer or the pipes after the mixer become blocked, preventing air from entering the cylinder and causing insufficient engine power or stalling, thus affecting driving safety.

[0005] In existing technologies, the following are common approaches to address the icing problem of the EGR mixer in EGR systems: First, calibration methods and ECU program control are used, utilizing existing engine sensors to identify the icing temperature and increasing engine load to initiate de-icing, thus preventing the risks associated with icing. Second, the EGR mixer is wrapped and equipped with an external liquid heating device, and temperature control devices are used for de-icing. Third, other possible anti-icing measures include insulation or adding a car cover to reduce the impact of icing on the windward surface.

[0006] Among the aforementioned measures to prevent EGR system EGR mixer icing, Method 1 involves calibration and ECU program control, utilizing existing engine sensors to identify icing temperatures and increasing engine load for de-icing. The main problems are numerous calibration control variables, complex program control logic, and the program's dependence determining the measurement accuracy and range adaptability of each sensor. Furthermore, when the driver is unloading or idling, if the engine program detects icing, increasing engine load is necessary for de-icing, sacrificing fuel economy, increasing customer costs, and potentially leading to customer complaints. Method 2 involves wrapping the EGR mixer and installing an external liquid heating device, as well as using a temperature control device for de-icing. This method is costly, and the combination of insulation and electric heating poses safety hazards if the external liquid is heated. Method 3 is relatively simple, mitigating the impact of icing but not completely solving the problem. Summary of the Invention

[0007] This application provides a natural gas engine EGR heating control method that can effectively prevent icing in the EGR mixer and the intake pipeline after the mixer, thereby saving costs.

[0008] In a first aspect, this application provides a natural gas engine EGR heating control method, comprising: detecting and acquiring the ambient temperature value of the engine; obtaining a preset operating mode to which a control valve enters based on the ambient temperature value and a mapping relationship between the ambient temperature value and a preset operating mode, the preset operating mode including a first operating mode and a second operating mode; in the first operating mode, the control valve activates a first return water pipeline to heat the EGR valve and EGR valve seat with return water; in the second operating mode, the control valve activates the first return water pipeline and the second return water pipeline to heat the EGR valve, the EGR valve seat, and the intake connecting bend with return water.

[0009] In some embodiments, obtaining the preset operating mode of the control valve based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset operating mode includes: determining that the control valve enters a first operating mode when the ambient temperature value is greater than or equal to a first temperature threshold; and determining that the control valve enters a second operating mode when the ambient temperature value is less than a second temperature threshold; wherein the second temperature threshold is less than the first temperature threshold.

[0010] In some embodiments, the first temperature threshold is taken within a temperature range greater than or equal to -15°C; the second temperature threshold is taken within a temperature range less than -15°C.

[0011] In some embodiments, the first temperature threshold ranges from -15℃ to -10℃.

[0012] In some embodiments, the second temperature threshold ranges from -20°C to -15°C.

[0013] Secondly, embodiments of this application also provide a natural gas engine EGR heating control device, comprising: a detection module for detecting and acquiring the ambient temperature value of the engine; a processing module for acquiring a preset operating mode to be entered upon startup based on the ambient temperature value and a mapping relationship between the ambient temperature value and a preset operating mode; and a control module for controlling the flow path of the heating fluid medium inside the return water pipe to heat the engine EGR according to the preset operating mode to be started based on the ambient temperature value; the control module is used to execute the natural gas engine EGR heating control method described above.

[0014] In some embodiments, the control module includes a first operating mode and a second operating mode. The first operating mode is to cut off the second return water pipe so that the heating fluid medium passes through the first return water pipe. The second operating mode is to simultaneously open the first return water pipe and the second return water pipe so that the heating fluid medium flows in parallel through the first return water pipe and the second return water pipe.

[0015] Thirdly, this application also provides a natural gas engine EGR intake system, including: an air compressor, provided with an air compressor cooling water pipe and an air compressor return water pipe, the air compressor cooling water pipe connecting the air compressor to the engine cooling system, the first end of the air compressor return water pipe being connected to the outlet end of the air compressor; a first return water pipe, the first end of which is connected to an EGR valve seat; a second return water pipe, the first end of which is connected to the inlet end of the intake connecting bend water jacket; a connecting pipe, connecting the outlet end of the bend water jacket to the inlet end of the EGR valve seat; a third return water pipe, connected to the outlet end of the EGR valve seat and the engine water pump body; and a control valve, connected to the second end of the air compressor return water pipe, the second end of the first return water pipe, and the second end of the second return water pipe, the control valve being electrically connected to the engine ECU to control the operating mode of the control valve according to the ambient temperature value.

[0016] In some embodiments, an EGR valve seat water jacket is also included. The EGR valve seat water jacket surrounds the outer wall of the EGR valve seat. The EGR valve seat water jacket is provided with a cavity, a water jacket inlet, and a water jacket outlet. The water jacket inlet is connected to the first return water pipeline, the water outlet of the EGR valve seat is located at the water jacket outlet, and the water jacket outlet is connected to the third return water pipeline.

[0017] In some embodiments, a one-way valve is also provided in the connecting pipeline, the one-way valve being used to prevent the heating fluid medium in the connecting pipeline from flowing back to the water jacket of the air inlet connecting bend.

[0018] In this embodiment, the ambient temperature value during engine operation is first obtained; then, based on the mapping relationship between the detected ambient temperature value and the preset working mode, the preset working mode to which the control valve enters is obtained. This preset working mode includes a first working mode and a second working mode; then, based on the working mode corresponding to different ambient temperatures, the return water pipeline activated by the control valve is determined. The control valve activates the corresponding return water pipeline to heat the EGR valve, EGR valve seat, and intake pipeline at the rear end of the EGR mixer as needed. This heating control method based on ambient temperature selection of heating mode can provide targeted heating for the EGR valve, EGR valve seat, and intake connection bend in low-temperature environments, effectively preventing water vapor condensation and freezing, without affecting normal vehicle driving and idling. It is especially suitable for icing conditions such as long downhill deceleration, as well as for frequent switching between deceleration and driving conditions in low-temperature environments, saving costs.

[0019] This application demonstrates through testing that existing circulating water heating structures without this feature exhibit significant icing at the EGR mixer and intake manifold within 10 minutes of operation at idle speed or during long downhill runs under low load in frigid regions where ambient temperatures drop below -15°C. This icing can severely impact engine stalling. This application, by employing a circulating heating control method, significantly reduces the problems caused by icing at the EGR mixer and intake manifold. The effectiveness of this heating method becomes more pronounced as the engine coolant temperature rises during operation, resulting in a more significant anti-icing and de-icing effect. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 Flowcharts of a natural gas engine EGR heating control method provided in some embodiments of this application;

[0022] Figure 2 This is a schematic diagram of the structure of a natural gas engine EGR heating control device provided in some embodiments of this application;

[0023] Figure 3 This is a schematic diagram of the structure of a natural gas engine EGR intake system provided in some embodiments of this application;

[0024] Figure 4 for Figure 3 Schematic diagram of the control valve structure;

[0025] Figure 5 for Figure 4 A schematic diagram of the structure of the middle air intake connecting bend.

[0026] The attached figures are labeled as follows:

[0027] 10-EGR heating control device; 20-EGR intake system;

[0028] 1-Air compressor cooling water pipe; 2-Air compressor; 3-Air compressor return water pipe; 4-Control valve; 5-First return water pipe; 6-Second return water pipe; 7-Intake pipe; 8-Throttle valve; 9-EGR mixer; 10-EGR valve seat; 11-Connecting pipe; 12-Check valve; 13-Intake connection elbow; 41-Inlet; 42-First outlet; 43-Second outlet;

[0029] 101 - Detection module; 102 - Processing module; 103 - Control module. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish different objects, not to describe a particular order or hierarchy.

[0032] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0033] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0035] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0036] In this application, "multiple" means two or more (including two).

[0037] Please refer to Figure 1 This application provides a method for EGR heating control of a natural gas engine, comprising the following steps:

[0038] Step S101: Detect and obtain the ambient temperature value of the engine;

[0039] Step S102: Based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset working mode, obtain the preset working mode that the control valve enters. The preset working mode includes a first working mode and a second working mode.

[0040] Step S103: In the first working mode, the control valve starts the first return water pipeline to heat the EGR valve and EGR valve seat.

[0041] In the second operating mode, the control valve starts the first and second return water lines to heat the EGR valve, EGR valve seat, and air inlet connection bend.

[0042] When the engine is running, the engine ECU identifies the operating environment through the engine's temperature sensor and controls the control valve to cut off the coolant connection to the second return water line. This means the air compressor coolant is a single circulating water line, flowing out through the first return water line to the EGR valve seat, circulating through the EGR valve seat water jacket and the EGR valve seat water jacket, and then returning to the engine water pump. In this application scenario, the EGR system and intake connection lines do not require heating. When the engine is in a lower ambient temperature condition, the engine ECU similarly identifies the operating environment through the engine's built-in ambient temperature sensor and controls the control valve to simultaneously open the first and second return water lines. In this case, the air compressor's return water is in a two-way parallel return water mode. The liquid cooled by the air compressor after drawing coolant from the cylinder block becomes hot circulating water. This hot circulating water, through the control valve, heats the EGR valve, EGR mixer, and intake connection bend respectively via the two parallel return water lines. This mode is particularly suitable for applications in low-temperature environments.

[0043] In one specific embodiment, step S102 above: obtaining the preset operating mode to which the control valve enters based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset operating mode, specifically includes:

[0044] When the ambient temperature is greater than or equal to the first temperature threshold, the control valve is determined to enter the first working mode.

[0045] When the ambient temperature is lower than the second temperature threshold, the control valve is determined to enter the second working mode.

[0046] The second temperature threshold is less than the first temperature threshold.

[0047] For example, the first temperature threshold is taken in a temperature range greater than or equal to -15°C, and the second temperature threshold is taken in a temperature range less than -15°C.

[0048] When the engine ECU obtains the ambient temperature of the engine through the engine temperature sensor, and the ambient temperature is higher than or equal to -15℃, the engine ECU sends a control signal, and the control valve 4 operates in the first working mode, that is, cutting off the second return water pipe 6, so that the return water of the air compressor 2 is in series mode. When the ambient temperature is lower than -15℃, the engine ECU sends a control signal, and the control valve 4 operates in the second working mode, that is, opening the second return water pipe 6, so that the return water of the air compressor 2 is in parallel mode.

[0049] In a preferred embodiment, the first temperature threshold ranges from -15℃ to -10℃. That is, when the temperature sensor detects that the engine's operating ambient temperature is within the range of -15℃ to -10℃, the control valve 4 operates in the first working mode, heating only the EGR valve and the EGR valve seat 10.

[0050] Furthermore, the second temperature threshold ranges from -20℃ to -15℃. When the ambient temperature is within the range of -20℃ to -15℃, the engine ECU controls the control valve 4 to operate in the second working mode, opening the second return water pipe 6 to introduce the heating fluid medium into the water jacket of the EGR valve, EGR valve seat 10, and intake connection bend 13 for heating.

[0051] When the ambient temperature is below -20℃, if the vehicle is started cold and then idles for an extended period, the engine coolant temperature is low and the engine's heat radiation is minimal. The EGR mixer is primarily affected by the external ambient temperature. If there is a slight leak in the EGR valve, the leaked EGR gas contains a large amount of moisture, which easily condenses and freezes at low ambient temperatures. During normal driving, when encountering long downhill sections, drivers often release the accelerator to allow the engine to enter a deceleration and injection-stopping state, where the fuel supply device stops supplying gas, and the throttle valve 8 is opened to ensure good fuel economy and braking function. When the driver presses the accelerator pedal, the control system immediately resumes natural gas injection. In low-temperature areas, when vehicles frequently switch between deceleration and injection-stopping driving conditions, the EGR mixer does not receive sufficient radiant heating. The EGR gas mixes with the low-temperature air entering through the intake manifold 7, causing the internal gaseous water to precipitate and rapidly condense and freeze on the inner surface of the EGR mixer. After verification, the invention can completely solve the problem of icing of EGR valve, EGR mixer 9 and intake bend in cold regions.

[0052] Therefore, this application uses the engine temperature sensor to identify and control the corresponding applicable application scenarios (i.e., application scenarios that require heating to prevent icing and application scenarios that do not require heating to prevent icing) by controlling valve 4 and the engine ECU calibration control strategy.

[0053] In this embodiment, the heating fluid medium can be heated and circulated engine coolant. Therefore, this application utilizes heated and circulated engine coolant to heat the EGR valve, EGR mixer 9, and intake connection bend 13, solving the problem of EGR system icing during cold-region idling and long downhill driving conditions. This application eliminates the need for additional engine load to achieve anti-icing measures, thus improving engine quality.

[0054] like Figure 2 As shown. Furthermore, this application embodiment also provides a natural gas engine EGR heating control device 10, including a detection module 101, a processing module 102, and a control module 103. The detection module 101 can detect and acquire the ambient temperature value of the engine. The processing module 102 can acquire the preset operating mode to be entered upon startup based on the ambient temperature value and the mapping relationship between the ambient temperature value and a preset operating mode. The control module 103 can control the flow path of the heating fluid medium inside the return water pipe to heat the engine EGR according to the preset operating mode corresponding to the ambient temperature value.

[0055] The natural gas engine EGR heating control device 10 provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0056] In one specific embodiment, the control module 103 includes a first working mode and a second working mode. The first working mode is to cut off the second return water pipe 6 so that the heating fluid medium passes through the first return water pipe 5. The second working mode is to simultaneously open the first return water pipe 5 and the second return water pipe 6 so that the heating fluid medium flows in parallel through the first return water pipe 5 and the second return water pipe 6.

[0057] The detection module 101 described above can be, but is not limited to, a temperature sensor. The processing module 102 and the control module 103 can be, but are not limited to, integrated controllers, such as an engine ECU.

[0058] like Figures 3 to 5 As shown. In addition, this application embodiment also provides a natural gas engine EGR intake system 20, including an air compressor 2, a first return water pipe 5, a second return water pipe 6, a connecting pipe 11, a third return water pipe, and a control valve 4.

[0059] Air compressor 2 is equipped with air compressor cooling water pipe 1 and air compressor return water pipe 3. Air compressor cooling water pipe 1 connects air compressor 2 to the engine cooling system. The first end of air compressor return water pipe 3 is connected to the outlet end of air compressor 2. The first end of the first return water pipe 5 is connected to EGR valve seat 10. The first end of the second return water pipe 6 is connected to the inlet end of the water jacket of intake connecting bend 13. Connecting pipe 11 connects the outlet end of the water jacket of intake connecting bend 13 to the inlet end of EGR valve seat 10. The third return water pipe is connected to the outlet end of EGR valve seat 10 and the engine water pump body. The inlet 41 of control valve 4 is connected to the second end of air compressor return water pipe 3. The first outlet 42 of control valve 4 is connected to the second end of the first return water pipe 5. The second outlet 43 of control valve 4 is connected to the second end of the second return water pipe 6. Control valve 4 is electrically connected to the engine ECU and its operating mode can be controlled according to the ambient temperature value.

[0060] When the engine is operating normally, the air compressor 2 runs normally under the drive of the engine gear transmission system, providing air supply for the vehicle's braking system. The moving parts inside the air compressor require circulating coolant for heat exchange. One end of the air compressor cooling water pipe 1 is connected to the engine cooling system, and the other end is connected to the air compressor 2. The hot water cooled by the air compressor 2 flows out through the air compressor return water pipe 3. The air compressor return water pipe 3 is connected to the control valve 4. The control valve 4 is an electronic control element, connected in parallel with the first return water pipe 5 and the second return water pipe 6. The control valve 4 is equipped with an electronic control interface, which is connected to the engine ECU through a wiring harness connector.

[0061] When receiving a signal from the ECU, control valve 4 controls the opening and closing of the first return water pipe 5 and the second return water pipe 6. The first return water pipe 5 is connected to the EGR valve seat 10 on the EGR mixer 9. The EGR valve is mounted on the EGR valve seat 10. The water connection serves to heat both the EGR mixer 9 and the EGR valve. The second return water pipe 6 is connected to the intake connection bend 13. Coolant enters the area of ​​the intake connection bend 13 from the second return water pipe 6, serving to heat the intake connection bend 13 and prevent it from freezing. After circulation, the coolant collects from the connecting pipe 11 and the connecting pipe 11 at the EGR valve seat 10, simultaneously heating the EGR valve and the EGR mixer 9. The coolant collected from the first return water pipe 5 and the connecting pipe 11 returns to the engine water pump body after circulation and heating.

[0062] Furthermore, the EGR valve seat 10 is fixedly connected to the outer wall of the EGR mixer 9. An EGR valve seat water jacket is provided on the outer wall of the EGR valve seat 10, and the EGR valve seat water jacket surrounds the outer wall surface of the EGR valve seat 10. The area where the EGR valve seat water jacket is arranged covers the possible icing area of ​​the EGR valve seat 10.

[0063] The EGR valve seat water jacket is equipped with a cavity, a water jacket inlet, and a water jacket outlet. The water jacket inlet is connected to the first return water pipe 5, and the water outlet of the EGR valve seat 10 is located at the water jacket outlet, which is connected to the third return water pipe. The coolant flowing out through the first return water pipe 5 and the connecting pipe 11 flows into the EGR valve seat 10, circulates through the EGR valve seat water jacket and the EGR mixer 9 water jacket, and then flows back to the engine to heat the areas of the EGR valve seat 10, the EGR valve, and the EGR mixer 9 that may freeze.

[0064] In addition, a one-way valve 12 is provided on the connecting pipe 11. The one-way valve 12 can prevent the heating fluid medium in the connecting pipe 11 from flowing back to the water jacket of the air inlet connecting bend 13, prevent the coolant from flowing back, and ensure heating efficiency.

[0065] The above provides a detailed description of the natural gas engine EGR heating control method, apparatus, and system provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A method for EGR heating control of a natural gas engine, characterized in that, include: Detect and obtain the ambient temperature value of the engine; Based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset working mode, the preset working mode to which the control valve enters is obtained. The preset working mode includes a first working mode and a second working mode. In the first working mode, the control valve starts the first return water pipeline to heat the EGR valve and EGR valve seat; In the second working mode, the control valve starts the first return water pipeline and the second return water pipeline to heat the EGR valve, the EGR valve seat and the air inlet connecting bend; The step of obtaining the preset operating mode of the control valve based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset operating mode includes: determining that the control valve enters the first operating mode when the ambient temperature value is greater than or equal to a first temperature threshold, and determining that the control valve enters the second operating mode when the ambient temperature value is less than a second temperature threshold, wherein the second temperature threshold is less than the first temperature threshold.

2. The natural gas engine EGR heating control method according to claim 1, characterized in that, The first temperature threshold is taken within a temperature range greater than or equal to -15℃; The second temperature threshold is taken within a temperature range of less than -15°C.

3. The natural gas engine EGR heating control method according to claim 2, characterized in that, The first temperature threshold ranges from -15℃ to -10℃.

4. The natural gas engine EGR heating control method according to claim 2, characterized in that, The second temperature threshold ranges from -20℃ to -15℃.

5. A natural gas engine EGR heating control device, characterized in that, include: The detection module (101) is used to detect and acquire the ambient temperature value of the engine; The processing module (102) is used to obtain the preset working mode to be entered based on the ambient temperature value and the mapping relationship between the ambient temperature value and the preset working mode. The control module (103) is used to control the flow path of the heating fluid medium inside the return water pipe and heat the engine EGR according to the preset working mode corresponding to the ambient temperature value. The control module (103) is used to execute the natural gas engine EGR heating control method according to any one of claims 1 to 4.

6. The natural gas engine EGR heating control device according to claim 5, characterized in that, The control module (103) includes a first working mode and a second working mode. The first working mode is to cut off the second return water pipe (6) so that the heating fluid medium passes through the first return water pipe (5). The second working mode is to open the first return water pipe (5) and the second return water pipe (6) at the same time so that the heating fluid medium flows in parallel through the first return water pipe (5) and the second return water pipe (6).

7. An EGR intake system for a natural gas engine, characterized in that, include: An air compressor (2) is provided with an air compressor cooling water pipe (1) and an air compressor return water pipe (3). The air compressor cooling water pipe (1) connects the air compressor (2) to the engine cooling system. The first end of the air compressor return water pipe (3) is connected to the water outlet of the air compressor (2). The first return water pipe (5) is connected to the EGR valve seat (10) at the first end. The second return water pipe (6) is connected at the first end to the water inlet end of the air inlet connecting bend water jacket; Connect the pipe (11) to the outlet end of the bend water jacket and the inlet end of the EGR valve seat (10); The third return water pipe is connected to the outlet end of the EGR valve seat (10) and the engine water pump body; The control valve (4) is connected to the second end of the air compressor return water pipe (3), the second end of the first return water pipe (5) and the second return water pipe (6). The control valve (4) is electrically connected to the engine ECU to control the working mode of the control valve (4) according to the ambient temperature value.

8. The natural gas engine EGR intake system according to claim 7, characterized in that, It also includes an EGR valve seat water jacket, which surrounds the outer wall of the EGR valve seat (10). The EGR valve seat water jacket is provided with a cavity, a water jacket inlet and a water jacket outlet. The water jacket inlet is connected to the first return water pipeline (5), and the water outlet of the EGR valve seat (10) is located at the water jacket outlet. The water jacket outlet is connected to the third return water pipeline.

9. The natural gas engine EGR intake system according to claim 7, characterized in that, It also includes a one-way valve (12) disposed in the connecting pipe (11), the one-way valve (12) being used to prevent the heating fluid medium in the connecting pipe (11) from flowing back to the water jacket of the air inlet connecting bend.

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