Methanol diesel oil HPDI engine and active pressure relief closed-loop control method thereof

Abstract

The invention discloses a methanol diesel oil HPDI engine, and relates to a methanol engine, the methanol diesel oil HPDI engine comprises a methanol supply unit, a diesel oil supply unit, an engine body and an engine controller, the methanol supply unit comprises a methanol fuel tank, a methanol filter, a methanol high-pressure pump and a methanol common rail pipe; the diesel supply unit comprises a diesel fuel tank, a diesel filter, a diesel high-pressure pump and a diesel common rail pipe, a methanol fuel metering valve is mounted on the methanol high-pressure pump, and a diesel fuel metering valve is mounted on the diesel high-pressure pump; the methanol common rail pipe is provided with a methanol electric control pressure release valve and a methanol rail pressure sensor, and the diesel oil common rail pipe is provided with a diesel oil electric control pressure release valve and a diesel oil rail pressure sensor. The invention further discloses an active pressure relief closed-loop control method. By ensuring that the diesel rail pressure is always higher than the methanol rail pressure in the pressure relief process, the risk that in the prior art, due to the pressure unbalance state that the methanol rail pressure is higher than the diesel rail pressure, nozzle abrasion is accelerated, and uncontrolled injection of methanol is increased is avoided.

Description

Technical Field

[0001] The present invention relates to a methanol engine, and more particularly to a methanol diesel HPDI engine and an active pressure relief closed-loop control method thereof. Background Art

[0002] In the current context of energy transformation, methanol has become a highly promising alternative fuel for engines due to its advantages such as cleanliness and wide availability. However, methanol engines still face many challenges in practical applications. Traditional spark-ignition methanol engines use spark plugs to ignite premixed gas, and still have technical bottlenecks such as difficulty in cold starting, high emissions of unburned methanol / formaldehyde, and limited thermal efficiency. For the relatively mature domestic dual-fuel methanol engine technology route of methanol airway / manifold premixing + diesel direct injection, although it can achieve thermal efficiency comparable to that of diesel engines, the methanol substitution rate is affected by detonation and decreases with increasing load. Due to the low proportion of methanol substitution rate, the carbon neutrality goal cannot be achieved.

[0003] In order to break through the above-mentioned technical bottlenecks of methanol engines, this field adopts a methanol-diesel dual high-pressure direct injection technology solution. Through the efficient combustion technology route of diesel micro-ignition and methanol diffusion combustion, the methanol replacement rate can reach more than 90%, and the thermal efficiency is equivalent to that of a diesel engine, realizing a more efficient, stable and clean operation of the methanol engine.

[0004] One approach to implementing a methanol-diesel high-pressure direct injection engine (HPDI) is to inject both fuels at high pressure through an integrated nozzle. However, during actual operation, it has been found that when the engine is shut down or operating under low-load conditions and system pressure relief is required, the methanol rail pressure drops significantly slower than the diesel rail pressure. This results in a pressure imbalance during the pressure relief process, where the methanol rail pressure is higher than the diesel rail pressure. This phenomenon violates the original design intent of the system and, if sustained over a long period, will accelerate nozzle wear and increase the risk of uncontrolled methanol injection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a methanol diesel HPDI engine and an active pressure relief closed-loop control method thereof, which solves the problem in the existing technology that the pressure imbalance state caused by the methanol rail pressure being higher than the diesel rail pressure leads to accelerated nozzle wear and increased risk of uncontrolled methanol injection.

[0006] A methanol-diesel HPDI engine disclosed herein comprises a methanol supply unit, a diesel supply unit, an engine body, and an engine controller. The methanol supply unit comprises a methanol fuel tank, a methanol filter, a methanol high-pressure pump, and a methanol common rail pipe connected in sequence. The diesel supply unit comprises a diesel fuel tank, a diesel filter, a diesel high-pressure pump, and a diesel common rail pipe connected in sequence. The engine body is equipped with an integrated injector connected to both the methanol common rail pipe and the diesel common rail pipe. The methanol high-pressure pump is equipped with a methanol fuel metering valve, and the diesel high-pressure pump is equipped with a diesel fuel metering valve. The methanol common rail pipe is equipped with a methanol electronically controlled pressure relief valve and a methanol rail pressure sensor, and the diesel common rail pipe is equipped with a diesel electronically controlled pressure relief valve and a diesel rail pressure sensor. The engine controller monitors the rail pressures of the methanol common rail pipe and the diesel common rail pipe in real time via the methanol rail pressure sensor and the diesel rail pressure sensor, respectively, and coordinates the coordinated operation of the methanol fuel metering valve, the diesel fuel metering valve, the methanol electronically controlled pressure relief valve, and the diesel electronically controlled pressure relief valve.

[0007] Preferably, the methanol electronically controlled pressure relief valve is connected to the methanol fuel tank through a methanol reflux pipeline.

[0008] Preferably, the diesel electronically controlled pressure relief valve is connected to the diesel fuel tank via a diesel return line.

[0009] An active pressure relief closed-loop control method for a methanol-diesel HPDI engine obtains a pressure relief operating condition signal from the engine common rail pipe. When the pressure relief operating condition signal indicates that the common rail pipe needs pressure relief, a combined control mode of a fuel metering valve and an electronically controlled pressure relief valve is executed, so that the methanol fuel metering valve, the diesel fuel metering valve, the methanol electronically controlled pressure relief valve, and the diesel electronically controlled pressure relief valve operate in coordination, thereby constraining the methanol rail pressure in the common rail pipe to be lower than the diesel rail pressure.

[0010] Preferably, the control method of the joint control mode is:

[0011] The methanol fuel metering valve and the diesel fuel metering valve are closed simultaneously, and then the methanol electronically controlled pressure relief valve is opened. After a delay of a set calibration time, the diesel electronically controlled pressure relief valve is opened again, so that the difference between the diesel rail pressure and the methanol rail pressure is a set target value.

[0012] Preferably, when the methanol electronically controlled pressure relief valve and the diesel electronically controlled pressure relief valve are simultaneously started to release pressure, the opening of the methanol electronically controlled pressure relief valve is adjusted through a PID closed-loop control mode to ensure that the difference between the diesel rail pressure and the methanol rail pressure is a set target value.

[0013] Preferably, the pressure relief operating condition signal includes a deceleration fuel cut-off signal and an ignition switch signal; when the deceleration fuel cut-off signal is the deceleration fuel cut-off function established or the ignition switch signal is zero, the combined control mode is enabled; otherwise, the engine is controlled to execute the original control mode.

[0014] Beneficial effects

[0015] The advantages of the present invention are:

[0016] 1. Possesses active pressure relief capabilities for methanol and diesel: By introducing PCV valves on the methanol and diesel high-pressure common rail pipes respectively, independent, rapid, and precise relief of methanol and diesel rail pressures is achieved.

[0017] 2. Coordinated dual-rail pressure control: By synchronously driving the PCV valves on the diesel and methanol common rails and the MEUN valves on the diesel and methanol pumps through the ECU, the methanol rail pressure can be forced to always be lower than the diesel rail pressure, thus avoiding potential risks caused by the methanol rail pressure exceeding the diesel rail pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the fuel supply and injection portion of the methanol diesel HPDI engine of the present invention;

[0019] Figure 2 It is a flow chart of the active pressure relief closed-loop control method of the present invention.

[0020] Among them: 1-methanol fuel tank, 2-methanol filter, 3-methanol high-pressure pump, 4-methanol fuel metering valve, 5-methanol electronically controlled pressure relief valve, 6-methanol common rail pipe, 7-methanol rail pressure sensor, 8-engine controller, 9-integrated injector, 10-diesel rail pressure sensor, 11-diesel common rail pipe, 12-diesel electronically controlled pressure relief valve, 13-diesel fuel metering valve, 14-diesel high-pressure pump, 15-diesel filter, 16-diesel fuel tank. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the embodiments, but this does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0022] Example 1

[0023] See Figure 1 A methanol-diesel HPDI engine according to the present invention comprises a methanol supply unit, a diesel supply unit, an engine body, and an engine controller 8. The methanol supply unit comprises a methanol fuel tank 1, a methanol filter 2, a methanol high-pressure pump 3, and a methanol common rail 6, which are connected in sequence. The diesel supply unit comprises a diesel fuel tank 16, a diesel filter 15, a diesel high-pressure pump 14, and a diesel common rail 11, which are connected in sequence. An integrated injector 9 is mounted on the engine body and is connected to both the methanol common rail 6 and the diesel common rail 11. Its injection pattern is controlled by the engine controller 8.

[0024] In this example, a methanol fuel metering valve 4 is installed on the methanol high-pressure pump 3, and a diesel fuel metering valve 13 is installed on the diesel high-pressure pump 14. A methanol electronically controlled pressure relief valve 5 and a methanol rail pressure sensor 7 are installed on the methanol common rail 6, and a diesel electronically controlled pressure relief valve 12 and a diesel rail pressure sensor 10 are installed on the diesel common rail 11. The engine controller 8 monitors the rail pressures of the methanol common rail 6 and the diesel common rail 11 in real time via the methanol rail pressure sensor 7 and the diesel rail pressure sensor 10, respectively. It coordinates the operation of the methanol fuel metering valve 4 and the diesel fuel metering valve 13 with the methanol electronically controlled pressure relief valve 5 and the diesel electronically controlled pressure relief valve 12 to ensure that the diesel rail pressure remains higher than the methanol rail pressure during the pressure relief process. This solves the problem in the prior art of accelerated nozzle wear and increased risk of uncontrolled methanol injection caused by a pressure imbalance resulting from a higher methanol rail pressure than the diesel rail pressure.

[0025] In this embodiment, the methanol electronically controlled pressure relief valve 5 is connected to the methanol fuel tank 1 via a methanol return line to recover the methanol fuel that flows out of the methanol common rail 6 during pressure relief. Furthermore, the diesel electronically controlled pressure relief valve 12 is connected to the diesel fuel tank 1 via a diesel return line to similarly recover diesel fuel, thus preventing waste.

[0026] Example 2

[0027] See Figure 1 and Figure 2 The active pressure relief closed-loop control method of this embodiment is primarily based on the common rail pressure relief control of the aforementioned methanol-diesel HPDI engine. This control method involves obtaining a pressure relief condition signal from the engine's common rail. When the pressure relief condition signal indicates that the common rail requires pressure relief, a combined control mode of the fuel metering valve and the electronically controlled pressure relief valve is implemented. This causes the methanol fuel metering valve 4 and diesel fuel metering valve 13 to coordinate with the methanol electronically controlled pressure relief valve 5 and diesel electronically controlled pressure relief valve 12, ensuring that the methanol rail pressure in the common rail is always lower than the diesel rail pressure.

[0028] In this system, diesel and methanol are supplied to the same nozzle body, namely the integrated injector 9, via independent high-pressure fuel lines. The system design requires that during the pressure relief process, the methanol rail pressure must always be lower than the diesel rail pressure. The core purpose of this design principle is to avoid potential risks caused by the methanol rail pressure exceeding the diesel rail pressure, including:

[0029] 1. Prevent the injection valve from opening uncontrollably due to abnormal pressure difference, causing accidental injection of a small amount of methanol;

[0030] 2. Prevent the internal sealing structure of the nozzle from failing due to pressure imbalance, which will cause increased wear on the sealing surface of precision valve parts.

[0031] The present invention proposes an innovative dual-rail active pressure relief closed-loop control method, which dynamically regulates the pressure gradient of the diesel common rail pipe 11 and the methanol common rail pipe 6 through the dual-rail pressure coordinated control of the engine controller 8, that is, the ECU, to ensure that the design constraint of methanol rail pressure < diesel rail pressure is strictly followed under specified operating conditions, thereby improving system reliability and the service life of key components such as integrated nozzles and sealing components.

[0032] The specific control method of the joint control mode is introduced below:

[0033] The enabling condition for the combined control mode is determined by the pressure relief condition signal, which includes the deceleration fuel cutoff signal and the ignition switch signal. When the deceleration fuel cutoff signal is set or the ignition switch signal is reset, the combined control mode is enabled; otherwise, the engine is controlled to execute the original control mode. If either of these two conditions is met, the combined control mode of the Meun and PCV valves is enabled. It should be noted that the Meun valve represents the fuel metering valve, and the PCV valve represents the electronically controlled pressure relief valve.

[0034] After enabling the combined control mode, the ECU monitors and collects the methanol rail pressure and diesel rail pressure in real time. In the subsequent control process, to ensure the pressure gradient condition of "diesel rail pressure - methanol rail pressure = calibration value" is met, the methanol fuel metering valve 4 and the diesel fuel metering valve 13 are first closed simultaneously. Then, the methanol electronically controlled pressure relief valve 5 is opened to relieve the pressure in the methanol common rail 6, thereby reducing the methanol rail pressure. However, the diesel electronically controlled pressure relief valve 12 does not open simultaneously; instead, it is delayed. The purpose of this delay is to ensure that "diesel rail pressure - methanol rail pressure = calibration value" is quickly met. The delay time can be set through calibration. According to general testing, it is sufficient to ensure that the calibration time is the duration between the opening of the methanol electronically controlled pressure relief valve 5 and the moment when "diesel rail pressure - methanol rail pressure = calibration value" is met. The calibration value can be calibrated to a range of values ​​and should be positive. During the execution process, due to differences in the control of the two PCV valves, occasional unsatisfactory conditions may occur. In these cases, closed-loop control is used to adjust the methanol PCV so that "diesel rail pressure - methanol rail pressure = calibration value," achieving full control of the entire process and ultimately ensuring that the condition of "diesel rail pressure - methanol rail pressure = calibration value" is met, thereby achieving independent, rapid, and precise relief of methanol and diesel rail pressures. The control method can adopt the conventional method of increasing valve opening. For example, when the methanol rail pressure is monitored to be close to the diesel rail pressure, the methanol electronically controlled pressure relief valve opening is automatically increased and the diesel electronically controlled pressure relief valve opening is simultaneously decreased.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These modifications and improvements will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A methanol diesel HPDI engine, comprising a methanol supply unit, a diesel supply unit, an engine body and an engine controller (8), wherein the methanol supply unit comprises a methanol fuel tank (1), a methanol filter (2), a methanol high-pressure pump (3) and a methanol common rail pipe (6) connected in sequence, and the diesel supply unit comprises a diesel fuel tank (16), a diesel filter (15), a diesel high-pressure pump (14) and a diesel common rail pipe (11) connected in sequence, and an integrated injector (9) connected to both the methanol common rail pipe (6) and the diesel common rail pipe (11) is installed on the engine body, characterized in that: The methanol high-pressure pump (3) is equipped with a methanol fuel metering valve (4), and the diesel high-pressure pump (14) is equipped with a diesel fuel metering valve (13); the methanol common rail pipe (6) is equipped with a methanol electronically controlled pressure relief valve (5) and a methanol rail pressure sensor (7); the diesel common rail pipe (11) is equipped with a diesel electronically controlled pressure relief valve (12) and a diesel rail pressure sensor (10); the engine controller (8) monitors the rail pressures of the methanol common rail pipe (6) and the diesel common rail pipe (11) in real time through the methanol rail pressure sensor (7) and the diesel rail pressure sensor (10), and coordinates and controls the coordinated actions of the methanol fuel metering valve (4), the diesel fuel metering valve (13), the methanol electronically controlled pressure relief valve (5), and the diesel electronically controlled pressure relief valve (12).

2. A methanol diesel HPDI engine according to claim 1, characterized in that: The methanol electronically controlled pressure relief valve (5) is connected to the methanol fuel tank (1) via a methanol reflux pipeline.

3. A methanol diesel HPDI engine according to claim 2, characterized in that: The diesel electric-controlled pressure relief valve (12) is connected to the diesel fuel tank (1) via a diesel return line.

4. An active pressure relief closed-loop control method for a methanol diesel HPDI engine according to any one of claims 1 to 3, characterized in that: A pressure relief working condition signal of the engine common rail pipe is obtained. When the pressure relief working condition signal indicates that the common rail pipe needs to be relieved, a combined control mode of the fuel metering valve and the electronically controlled pressure relief valve is executed, so that the methanol fuel metering valve (4), the diesel fuel metering valve (13), the methanol electronically controlled pressure relief valve (5), and the diesel electronically controlled pressure relief valve (12) are coordinated to constrain the methanol rail pressure in the common rail pipe to be lower than the diesel rail pressure.

5. The active pressure relief closed-loop control method according to claim 4, characterized in that: The control method of the joint control mode is: The methanol fuel metering valve (4) and the diesel fuel metering valve (13) are closed simultaneously, and then the methanol electronically controlled pressure relief valve (5) is opened. After a delay of a set calibration time, the diesel electronically controlled pressure relief valve (12) is opened again, so that the difference between the diesel rail pressure and the methanol rail pressure is a set target value.

6. The active pressure relief closed-loop control method according to claim 5, characterized in that: During the simultaneous activation of the methanol electronically controlled pressure relief valve (5) and the diesel electronically controlled pressure relief valve (12) for pressure relief, the opening of the methanol electronically controlled pressure relief valve (5) is adjusted through a PID closed-loop control mode to ensure that the difference between the diesel rail pressure and the methanol rail pressure is a set target value.

7. The active pressure relief closed-loop control method according to claim 4, characterized in that: The pressure relief working condition signal includes a deceleration fuel cut-off signal and an ignition switch signal; when the deceleration fuel cut-off signal is the deceleration fuel cut-off function established or the ignition switch signal is zero, the joint control mode is enabled; otherwise, the engine is controlled to execute the original control mode.

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