Methanol engine fuel heating system and control method

Abstract

The invention discloses a methanol engine fuel heating system and a cold start control method, the system adopts an integrated fuel supply structure, and direct combustion heating of methanol fuel is realized through collaborative design of a dual-mode electric pump, a direct combustion type combustion heater and a common rail pipe. The method has the innovation points that (1) the engine and the heater share a methanol box and an electric pump, and a dual-pressure mode (the engine mode is 0.5 MPa / the heating mode is 0.8 MPa) not only can meet the injection pressure of the engine, but also can meet the pressure required by atomization of the heater; (2) the direct-fired heater heats the fuel through methanol direct-fired heating, the temperature of the methanol fuel can be increased by 60-80 DEG C within 3-6 minutes, and the heat efficiency is larger than or equal to 85%; and 3) an intelligent safety protection mechanism control strategy realizes one-key starting and self-diagnosis functions at two stages of preheating and cold starting, and ensures the starting success rate in an environment of-45 DEG C, and the starting time of the engine is less than or equal to 10 seconds.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol engines, and more particularly to a fuel heating system and control method for a methanol engine. Background Art

[0002] Due to the characteristics of methanol fuel, such as a high ignition point temperature (470°C), a large latent heat of vaporization (1100 kJ / kg), and a low saturated vapor pressure (3.8 kPa @ 20°C), it is very difficult to cold start a methanol engine in a low-temperature environment.

[0003] To meet the cold start performance of methanol engines, the currently mature countermeasure is to use fuels such as gasoline, diesel, or natural gas as auxiliary fuels for low-temperature cold starts. Patent CN115653748A (a methanol and natural gas dual-fuel engine and control method) mentions using natural gas as an auxiliary fuel for cold starts. However, for a mobile vehicle power system, the two-fuel filling scheme is very inconvenient for vehicle end-users to operate, and the vehicle is designed with two fuel systems, which makes the system complex and increases the engine cost.

[0004] For large mining trucks or methanol engines for range extension of construction machinery, in addition to using gasoline fuel for auxiliary starting, some engines also need to be preheated to meet the cold start performance. Currently, there are mainly two ways for the cold start auxiliary heating system of methanol engines. One is to heat the coolant. By using high-temperature coolant to heat the engine body and drive the oil temperature to rise, reducing the engine friction work to meet the cold start performance of the engine; the other is to heat the methanol fuel. Patent CN116335857A (a diesel preheating system, method, and mining truck for a methanol engine of a mining truck) mentions using a diesel burner to heat the engine coolant with diesel as the fuel. The heater using diesel as the fuel has disadvantages similar to those of gasoline and methanol dual-fuel engines. It also requires filling two fuels, diesel and methanol, which is inconvenient for vehicle operation. At the same time, heating the coolant takes a long time (usually 17 - 30 minutes), and the control of this heater is independent of the cold start control of the engine, with insufficient coordination with the engine ECU, resulting in a low starting success rate. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a fuel heating system and control method for a methanol engine, so as to achieve the purpose that the vehicle can use only methanol as fuel and significantly improve the cold start success rate through preheating.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A methanol engine fuel heating system includes an integrated fuel supply system and a direct combustion heater. The integrated fuel supply system includes a methanol tank, an electric methanol pump, a common rail pipe for the methanol engine, and an electromagnetic cut-off valve connected in sequence. The direct combustion heater is connected between the electromagnetic cut-off valve and the methanol tank to achieve fuel supply and combustion. A circulation branch for heating methanol by heat exchange through the direct combustion heater branches between the methanol pump and the common rail pipe of the methanol engine.

[0008] The electric methanol pump is a dual-mode electric pump.

[0009] The direct combustion heater is a methanol combustion heater using direct methanol combustion for heating.

[0010] The methanol engine and the methanol combustion heater share the methanol tank and the dual-mode electric pump.

[0011] A methanol pressure sensor and a methanol temperature sensor for real-time monitoring of the fuel state are provided on the common rail pipe of the methanol engine.

[0012] The direct combustion heater includes a combustion chamber and a heat exchanger. The heat exchanger is connected to the circulation branch and the methanol tank. A heater nozzle, a spark plug, and a blower are provided in the combustion chamber. The heater nozzle is connected to the oil pipe behind the electromagnetic cut-off valve.

[0013] The direct combustion heater is integrated on the engine.

[0014] A cold start control method for the methanol engine fuel heating system described above adopts two working modes; one is the normal start mode, and the other is the preheating cold start mode;

[0015] Normal start mode:

[0016] Cooperate the above three systems of the integrated fuel supply system, the direct combustion heater, and the engine system. By collecting the methanol fuel temperature sensor and combining the coolant temperature sensor, ambient temperature, and speed signal feedback on the engine, cooperate to control the working states of the heater and the engine, and diagnose and provide safety protection for the working states of the heater and the engine;

[0017] Preheating cold start mode: When the ambient temperature < 18°C and the coolant temperature < 45°C, the heater is automatically turned on with one key, and the fuel temperature is raised to 60 - 80°C within a certain time; after the methanol fuel temperature reaches 60°C, the engine automatically starts; if the engine fails to start once, the heater self-start function is performed again.

[0018] When the engine fails to start successfully twice in a row, diagnose the states of the engine and the heater, and output engine fault codes and heater fault codes according to the diagnosis results.

[0019] The methanol engine fuel heating system is equipped with a safety protection mechanism. When the fuel temperature exceeds 60°C, it will automatically cut off. When the pressure is abnormal (exceeding 0.9 MPa or less than 0.2 MPa), it will alarm and implement flameout protection.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. Avoid refueling vehicles with two fuels, diesel and methanol: By adopting the solution of this patent, vehicles can use only methanol as fuel, avoiding the external diesel preheating solution used by methanol engines to improve cold start, and there is no need to refuel diesel additionally; this greatly improves the vehicle commuting rate and reduces the fuel use cost.

[0022] 2. Shorten the cold start preheating time of the engine: The traditional cold start preheating solution for methanol engines is to heat the coolant through a heater to increase the temperature of the engine body and lubricating oil, thereby indirectly improving the cold start performance of the engine. However, due to the large volume of the coolant, the heating time is long, and this method of indirectly improving the methanol atomization quality has poor cold start effect and low cold start success rate; adopting the solution of this patent can effectively shorten the cold start preheating time.

[0023] 3. Reduce system complexity: The methanol engine and the combustion heater share a methanol pump, which improves the reliability of the system and reduces costs.

[0024] 4. Automatically perform cold start of the engine with one key: By adopting the control method of this patent, when the methanol engine performs low-temperature cold start, it can be operated with one key; this avoids relying on manual operation of the external coolant heater, which may lead to inaccurate judgment of cold start conditions and cold start failure. The solution of this patent greatly improves the cold start success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following briefly describes the content expressed by each drawing in this specification and the marks in the drawings:

[0026] Figure 1 It is a schematic diagram of the integrated fuel supply system of the present invention.

[0027] Figure 2 It is a schematic diagram of the direct-fired combustion heater of the present invention.

[0028] Figure 3 It is a schematic diagram of the control of the dual-mode intelligent switching logic module of the present invention.

[0029] Figure 4 It is a schematic diagram of the control of the preheating cold start module of the present invention.

[0030] Figure 5 It is a schematic diagram of the control of the safety protection mechanism module of the present invention.

[0031] Figure 6This is a schematic diagram of the working sequence of each component for preheating and cold starting of the present invention.

[0032] In the figure:

[0033] 1. Methanol tank, 2. Electric methanol pump, 3. Methanol temperature sensor, 4. Methanol nozzle for engine, 5. Methanol pressure sensor, 6. Electromagnetic cut-off valve, 7. Direct combustion heater, 7-1. Heater methanol nozzle, 7-2. Atomization mesh, 7-3. Spark plug, 7-4. Fan. Specific embodiments

[0034] The following further describes in detail the specific embodiments of the present invention by describing the embodiments with reference to the accompanying drawings.

[0035] As Figures 1 to 6 shown, the methanol engine fuel heating system includes an integrated fuel supply system and a direct combustion heater. The integrated fuel supply system includes a methanol tank 1, an electric methanol pump 2, a common rail pipe for the methanol engine, and an electromagnetic cut-off valve 6 connected in sequence; the direct combustion heater is connected between the electromagnetic cut-off valve and the methanol tank to realize fuel supply and combustion, and a circulation branch for heating methanol through heat exchange by the direct combustion heater branches between the methanol pump and the common rail pipe of the methanol engine.

[0036] The electric methanol pump 2 is a dual-mode electric pump; the direct combustion heater 7 is a methanol combustion heater using direct methanol combustion; the methanol engine and the methanol combustion heater share the methanol tank and the dual-mode electric pump.

[0037] The direct combustion heater 7 is integrated on the engine. The direct combustion heater includes a combustion chamber and a heat exchanger. The heat exchanger is connected to the circulation branch and the methanol tank. The combustion chamber is provided with a heater nozzle 7-1, a spark plug 7-3, and a fan 7-4. The heater nozzle is connected to the fuel pipe behind the electromagnetic cut-off valve. The vehicle can use methanol as the only fuel. The direct combustion heater uses the heat generated by the combustion of the supplied methanol to heat the methanol in the circulation branch, achieving preheating and greatly improving the cold start success rate.

[0038] Furthermore, a methanol pressure sensor 5 and a methanol temperature sensor 3 for real-time monitoring of the fuel state are provided on the common rail pipe of the methanol engine.

[0039] The methanol engine and the methanol combustion heater share the methanol tank and the dual-mode electric pump. The electric pump is capable of providing different fuel supply pressures for the heater mode (0.8 MPa) and the engine mode (0.5 MPa); the direct combustion heater adopts the direct methanol combustion heating method, with a thermal efficiency ≥ 85%, and includes a combustion chamber and a heat exchanger; the combustion chamber of the combustion heater is equipped with a heater nozzle 7-1, an atomization mesh 7-2, a spark plug 7-3, and a fan 7-4. The spark plug can heat the fuel to above 1300 °C within 3 seconds.

[0040] The cold start control method of the methanol engine fuel heating system of the present invention adopts two working modes; one is the normal start mode, and the other is the preheating cold start mode;

[0041] Normal start mode:

[0042] Cooperate the above three systems of the integrated fuel supply system, direct combustion heater, and engine system to work together. By collecting the methanol fuel temperature sensor and combining the coolant temperature sensor, ambient temperature, and speed signal feedback on the engine, jointly control the working states of the heater and the engine, and diagnose and provide safety protection for the working states of the heater and the engine;

[0043] Preheating cold start mode: When the ambient temperature < 18°C and the coolant temperature < 45°C, automatically turn on the heater with one key, and raise the fuel temperature to 60 - 80°C within a certain time; after the methanol fuel temperature reaches 60°C, the engine starts automatically; if the engine fails to start once, perform the secondary heater self-start function again.

[0044] Furthermore:

[0045] When the engine fails to start successfully twice in a row, diagnose the states of the engine and the heater, and output the engine fault code and the heater fault code according to the diagnosis results. The methanol engine fuel heating system has a safety protection mechanism, automatically cuts off when the fuel temperature exceeds 60°C, alarms and shuts down the engine when the pressure is abnormally high > 0.9 MPa or low < 0.2 MPa.

[0046] A preferred specific example of the present invention is:

[0047] The content of the present invention's patent is a fuel heating system and a cold start control method for a methanol engine. The fuel heating system adopts a novel system architecture, which consists of two parts. The first part is an integrated fuel supply system, and the second part is a direct combustion heater. Combining this novel system architecture, a new cold start control method is developed. This cold start control method consists of two control modules. The first control module is a dual-mode intelligent switching logic module, and the second control module is a safety protection mechanism module.

[0048] The main features of this system architecture are: 1. The combustion heater is integrated on the engine. The combustion heater and the engine use the same methanol fuel and share an electric methanol pump; 2. The heat exchange medium of the methanol burner is also methanol fuel, and the heat exchange medium and the fuel share a methanol tank; 3. The combustion heater and the engine work together. The control system automatically controls the start and stop of the combustion heater according to the signals such as ambient temperature, methanol fuel temperature, and coolant temperature collected, and decides whether to perform preheating control on the engine start.

[0049] The first part of the system architecture is the integrated fuel supply system, which consists of an electric methanol pump, a common rail pipe, a temperature sensor, an electromagnetic cut-off valve, a combustion heater, an engine nozzle, a burner nozzle, a methanol tank, etc. The methanol engine adopts the intake port fuel injection method, and the fuel injectors of each cylinder are installed on the common rail pipe. The electromagnetic cut-off valve is arranged between the combustion heater and the common rail pipe, and can control the cut-off of methanol fuel entering the combustion heater; there is a burner nozzle arranged on the combustion heater, which is different from the engine methanol nozzle, and its flow rate is much smaller than that of the engine nozzle. The fuel inlet pipe of the burner is connected behind the electric methanol pump and is connected to the engine fuel inlet pipe, forming a one-in-two-out connection with the electric methanol pump. The methanol temperature sensor is arranged on the common rail pipe and can measure and sense the temperature of the methanol fuel.

[0050] The second part of the system architecture is the direct combustion heater. This heater is a self-volatile combustion heater fueled by methanol. The heater mainly consists of two parts, one is the combustion chamber and the other is the heat exchanger. The combustion chamber consists of a methanol nozzle, a methanol spark plug, a methanol atomization net, a blower, etc. The methanol fuel is sprayed on the atomization net in the combustion chamber through the methanol nozzle, and the electric methanol pump provides the injection pressure; there is a methanol spark plug arranged in the combustion chamber, and its heating temperature can reach above 1300 °C. The methanol is heated at a high temperature by the spark plug and forms combustible methanol gas on the methanol atomization net. After the temperature reaches the self-ignition temperature, it catches fire and burns. The heat exchanger is designed with an interlayer water jacket, and fins are arranged on the outside. The fins contact the high-temperature gas burned in the combustion chamber and transfer the heat to the internal heat exchange medium methanol, and the electric methanol pump ensures the flow rate of the methanol heat exchange medium.

[0051] The cold start control method consists of two control modules. The two control modules work together the above three systems of the integrated fuel supply system, the direct combustion heater, and the engine system. By collecting the methanol fuel temperature sensor and combining the signal feedback of the coolant temperature sensor, ambient temperature, engine speed, etc. on the engine, the working states of the heater and the engine are jointly controlled, and the working states of the heater and the engine are diagnosed and protected. Through the energy management module, the best cold start control strategy is achieved.

[0052] The first control module is a dual-mode intelligent switching logic module. This control module is mainly divided into two working modes, one is the normal start mode and the other is the cold start mode. In the normal start mode, the combustion heater does not need to be turned on, the methanol fuel solenoid valve is in the closed state, and the engine starts using the conventional start control strategy;

[0053] Preheating cold start mode: When the control system detects that the ambient temperature and coolant temperature are lower than the judgment threshold, the cold start mode is activated. First, the methanol fuel solenoid valve opens, and the combustion heater is turned on. Methanol fuel is heated in the methanol burner and enters the preheating mode. When the methanol temperature meets the temperature required for the engine cold start, the starter is used to drag the engine for cold start. After the engine starts successfully, it is judged according to parameters such as engine speed, coolant temperature, and methanol fuel temperature whether to turn off the methanol combustion heater and perform delayed control management on the methanol electromagnetic cut-off valve;

[0054] The second control module is a safety protection mechanism module. This control module mainly monitors and diagnoses the working states of the combustion heater and the engine, judges the response strategy executed after two consecutive cold start failures, judges the working states of the heater and the engine, and outputs relevant alarm information for prompt.

[0055] One of the characteristics of this invention patent is that the methanol combustion heater and the methanol engine share the same fuel, which greatly improves the convenience of product application. And using the same fuel simplifies the structural layout of the fuel supply system of the methanol engine and methanol vehicle, reduces the system complexity, and makes the system have higher reliability and lower cost;

[0056] Another characteristic of this invention patent is that the methanol combustion heater and the methanol engine share the same methanol pump. This structural layout saves the pumps for the heat exchange medium and the pumps for fuel injection for the methanol combustion heater system, integrating three pumps into one. By using the original electric methanol pump of the engine, a higher methanol injection pressure is provided for the methanol burner, enabling the methanol to be atomized and burned more fully in the burner, with higher thermal efficiency, and ensuring the flow rate of the heat exchange medium.

[0057] Another characteristic of this invention patent is that the heat exchange medium of the methanol burner is the methanol fuel itself. This way, methanol serves as both fuel and heat exchange medium, and there is no need to indirectly re-heat the methanol fuel through the coolant, which can quickly heat the methanol fuel.

[0058] Another characteristic of this patented invention is that this control method has a normal start mode and a cold start mode, and the two start modes are automatically judged by the controller. This control method combines the start control of the engine and the operation control of the combustion heater, without the need for separate manual control of the heater. At the same time, it also automatically manages the engine cold start, avoiding the engine start failure caused by the over-long or insufficient heating time of the methanol combustion heater.

[0059] Next, with reference to the accompanying drawings, taking a 15L heavy-duty commercial vehicle methanol engine as an example, the specific implementation manner of this invention patent will be further described in detail, aiming to demonstrate the technical characteristics and advantages of this invention patent.

[0060] Fuel heating supply system integration: The engine and the heater share the same methanol tank, electric methanol pump, and common rail pipe. The two-way fuel supply switching is achieved through an electromagnetic cut-off valve. The electric methanol pump adopts a dual-pressure control mode: the engine injection mode (0.7 - 0.6 MPa) to meet the methanol injection and atomization in the engine intake port; the heater working mode (0.2 - 0.3 MPa) to improve the atomization effect of the heater and regulate the methanol flow rate of the heat exchange medium.

[0061] The combustion chamber of the direct-fired combustion heater adopts methanol atomization direct combustion technology. The heater nozzle sprays methanol onto the atomization net in the combustion chamber, and the fuel is heated to over 1300 °C by the spark plug to form a combustible mixture. The heat exchanger directly receives the heat of the methanol combustion gas, heats the internal methanol liquid, converts the chemical energy of methanol combustion into the internal energy of methanol, provides the methanol fuel temperature, and the thermal efficiency is over 85%. The methanol fuel temperature can be increased by 60 - 80 °C within 3 - 6 minutes.

[0062] Dual-mode intelligent switching logic module: The ECU real-time collects signals such as methanol fuel temperature, coolant temperature (Tcool), and ambient temperature (Tenv), and realizes the coordinated control of the electric methanol pump, electromagnetic cut-off valve, and heater through the CAN bus, so as to realize the normal start mode and the pre-heating cold start mode.

[0063] Timing diagram of the pre-heating cold start mode:

[0064] T0 = 0 s: The ECU detects that Tenv < 18 °C and Tcool < 25 °C. If one of the two conditions is met, the cold start pre-heating mode is activated.

[0065] T0 + 2 s: The electromagnetic cut-off valve opens, and the electric fuel pump boosts the pressure to 0.3 MPa through speed control, and the fan starts (500 rpm).

[0066] T0 + 5 s: The spark plug is energized and heats up to 1200 °C within 3 s.

[0067] T0 + 15 s: The burner nozzle (frequency 1 Hz) starts to spray, the temperature around the spark plug reaches 1350 °C, the methanol mixture is ignited, and the heater starts to ignite and work.

[0068] T0 + 30 s: Gradually increase the burner nozzle (frequency 1 - 10 Hz), increase the methanol injection volume, the thermal power reaches 3 - 5 kW, and the fuel temperature gradually rises from -35 °C to 55 °C (temperature rise rate 0.2 °C / s). The temperature rise rate of the methanol fuel can be closed-loop feedback controlled according to the methanol fuel temperature sensor.

[0069] T0 + 300 s: The temperature of the methanol fuel reaches 60 °C, meeting the starting threshold (≥60 °C). Enter the starting preparation, and the engine electronic control system is powered on to complete the self-check.

[0070] T0 + 303 s: Cut off the injection of the burner nozzle, the methanol burner goes out, the electric fuel pump boosts the pressure to 0.5 MPa through speed control, and the fan speed drops to (500 rpm); the starter (24 V, 6 kW) drags the engine speed up to 200 r / min, and the engine starts according to the normal procedure. The first telephone start of the engine is successful, with a speed threshold (≥800 r / min), a speed fluctuation <50 r / min, and the speed stabilizes at 700 - 800 r / min.

[0071] T0 + 360 s: The methanol engine completes the cold start. The electromagnetic cut-off valve closes with a 3 s delay to prevent oil return shock and allows the combustion chamber to complete cooling, avoiding excessive local temperature oxidation of the methanol fuel; the fan closes with a 30 s delay to ensure that the remaining methanol fuel burns out.

[0072] Safety protection mechanism module: The ECU real-time collects signals of the methanol fuel temperature, coolant temperature (Tcool), and engine speed (n). If the engine start count exceeds 2 times, it judges which fault mode it is according to conditions such as the methanol fuel temperature and methanol injection pressure, whether it belongs to a heater fault or an engine fault, and outputs a fault code. The common fault codes, phenomena, diagnostic steps, and solutions for the heater are as follows:

[0073]

[0074] The above is only a description of the preferred embodiments of the present invention. The above technical features can be arbitrarily combined to form multiple embodiment schemes of the present invention.

[0075] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A methanol engine fuel heating system, characterized in that: It includes an integrated fuel supply system and a direct-fired combustion heater. The integrated fuel supply system includes a methanol tank, an electric methanol pump, a methanol engine common rail pipe and an electromagnetic shut-off valve which are connected in sequence. The direct-fired combustion heater is connected between the electromagnetic shut-off valve and the methanol tank to realize fuel supply and combustion. A circulation branch for heating methanol through heat exchange through the direct-fired combustion heater is branched between the methanol pump and the methanol engine common rail pipe.

2. The methanol engine fuel heating system as claimed in claim 1, characterized in that: The electric methanol pump is a dual-mode electric pump.

3. The methanol engine fuel heating system as claimed in claim 2, characterized in that: The direct-fired combustion heater is a methanol combustion heater that uses methanol for direct heating.

4. The methanol engine fuel heating system as claimed in claim 3, characterized in that: The methanol engine and the methanol combustion heater share a methanol tank and a dual-mode electric pump.

5. The methanol engine fuel heating system as claimed in claim 1, characterized in that: The methanol engine common rail pipe is provided with a methanol pressure sensor and a methanol temperature sensor for real-time monitoring of the fuel state.

6. The methanol engine fuel heating system as claimed in claim 4, characterized in that: The direct-fired combustion heater includes a combustion chamber and a heat exchanger, the heat exchanger is connected to a circulation branch and a methanol tank, a heater nozzle, an ignition plug and a blower are arranged in the combustion chamber, and the heater nozzle is connected to an oil pipe behind an electromagnetic shut-off valve.

7. The methanol engine fuel heating system as claimed in claim 6, characterized in that: The direct-fired combustion heater is integrated on the engine.

8. A cold start control method for a methanol engine fuel heating system as claimed in claim 1, characterized in that: The cold start control method adopts two working modes: one is a normal start mode, and the other is a preheat cold start mode; Normal start mode: The above-mentioned integrated fuel supply system, direct-fired combustion heater and engine system are coordinated to work together. By collecting the methanol fuel temperature sensor and combining the coolant temperature sensor, ambient temperature and speed signal feedback on the engine, the heater and engine working status are coordinated to control, diagnose and safely protect the heater and engine working status; Preheating cold start mode: When the ambient temperature is less than 18℃ and the coolant temperature is less than 45℃, the heater is automatically turned on with one button, and the fuel temperature is raised to 60-80℃ within a certain period of time; after the methanol fuel temperature reaches 60℃, the engine starts automatically; if the engine fails to start once, the heater self-start function is performed twice.

9. The control method according to claim 8, characterized in that: When the engine fails to start twice in succession, the engine and heater status are diagnosed, and the engine fault code and heater fault code are output according to the diagnosis results.

10. The control method according to claim 8, characterized in that: The methanol engine fuel heating system is equipped with a safety protection mechanism, which can automatically cut off the fuel if it overheats by more than 60°C, and alarm and flameout protection if the pressure is abnormally greater than 0.9MPa or less than 0.2MPa.

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