Methanol-diesel oil dual-fuel combustion method and device adopting staged injection organization

Abstract

The invention relates to the technical field of combustion control of internal combustion engines, and discloses a methanol-diesel dual-fuel combustion method and device.The methanol-diesel dual-fuel combustion method comprises the three stages of methanol main injection in the gas inlet stage, methanol supplementary injection in the final compression stage and diesel micro-ignition, and the fuel evaporation quality is improved through a methanol heater; and a combustion center angle CA50 is calculated in real time based on a cylinder pressure signal, and self-adaptive correction is performed on reinjection timing by using a PI control algorithm, so that closed-loop stable control of a combustion phase is realized. According to the methanol-diesel dual-fuel engine, the uniformity of mixed gas can be remarkably improved, combustion fluctuation is inhibited, the methanol substitution ratio is increased, the fault safety switching function is achieved, and the methanol-diesel dual-fuel engine is suitable for efficient and clean operation of medium-high load methanol-diesel dual-fuel engines.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine combustion control technology, and in particular to a methanol-diesel dual-fuel combustion method and apparatus with a staged injection system. Background Technology

[0002] Methanol-diesel dual-fuel combustion technology is currently one of the important research directions in the field of clean and efficient energy for internal combustion engines, and it is widely used in medium- and high-load power systems such as marine power, generator sets, heavy-duty trucks, and construction machinery. Methanol, as an oxygenated fuel, has advantages such as wide availability, high renewability, and clean combustion. Its use in combination with diesel can significantly reduce carbon emissions and particulate matter emissions, while maintaining power performance similar to that of traditional diesel engines under medium- and high-load conditions. Therefore, it has attracted much attention in the context of the "dual carbon" goal.

[0003] In practical applications, methanol-diesel dual-fuel engines primarily introduce methanol into the cylinder via port injection or direct injection, where it mixes with air to form a combustible mixture. Ignition is then achieved through a small amount of diesel fuel injection, thus completing the combustion process. This technology has been demonstrated in some marine propulsion systems and stationary generator sets, showcasing good economic and environmental potential. However, due to the significant differences in the physical properties of methanol (such as high latent heat of vaporization and low vaporization temperature) compared to diesel, its combustion organization under complex operating conditions still faces numerous technical challenges, directly affecting the engine's reliability, economy, and emissions performance.

[0004] Although the methanol-diesel dual-fuel mode has good emission reduction potential, the following technical problems still exist in practical engineering applications:

[0005] Technical problem 1: Poor uniformity of air-fuel mixture: Methanol has a large latent heat of vaporization, and evaporates slowly, especially at low temperatures. It is easy to form a liquid film in the intake manifold or cylinder wall, resulting in localized overly rich or lean air-fuel mixtures, which affects combustion stability and flame propagation.

[0006] Technical problem 2: Difficulty in controlling combustion phase: Since the combustion rate of methanol is significantly affected by the concentration distribution of the mixture, the traditional single-stage injection method cannot readjust the mixture in the later stage of compression, causing the combustion center angle (CA50) to drift with the operating conditions, affecting thermal efficiency and emission consistency.

[0007] Technical problem three: Insufficient ignition reliability: Although diesel micro-ignition can provide an initial ignition nucleus, its effectiveness is limited by the uniformity of methanol mixing. If the mixture is uneven, the ignition nucleus growth rate fluctuates greatly, which can easily lead to partial cycle misfires or knocking.

[0008] Technical problem four: lack of adaptive adjustment capability: existing systems mostly adopt open-loop control strategies, which cannot dynamically adjust injection parameters according to real-time combustion status, making it difficult to adapt to complex operating conditions such as changing working conditions and changing ambient temperature.

[0009] Technical issue five: Inadequate system safety: In the event of sensor failure or abnormal combustion, there is a lack of effective fault response mechanisms, which may lead to uncontrolled combustion or engine damage.

[0010] Therefore, those skilled in the art urgently need a methanol-diesel dual-fuel combustion technology solution with a staged injection mechanism. Summary of the Invention

[0011] The core technical problem to be solved by this invention is the systemic control challenge of uneven mixture organization, large combustion phase drift, and lack of real-time adaptive adjustment capability during the combustion of methanol-diesel dual fuels.

[0012] This invention addresses the aforementioned core technical problems by designing a methanol-diesel dual-fuel combustion method and apparatus with a staged injection system. It employs a coordinated injection strategy of "main injection + supplementary injection + diesel micro-ignition," combined with an adaptive control mechanism based on cylinder pressure feedback, to achieve closed-loop regulation of the combustion phase. The main features of the entire technical solution are as follows:

[0013] During the intake phase, a large amount of methanol is injected to form a basic uniform mixture.

[0014] A small dose of methanol was injected at the end of the compression phase to adjust the local concentration distribution.

[0015] Inject a small amount of diesel fuel near the top dead center of the compressor to ensure reliable ignition;

[0016] Improve the quality of methanol evaporation by using a methanol heater;

[0017] The cylinder pressure signal is acquired in real time, the combustion center angle CA50 is calculated, and the injection timing is dynamically corrected through the PI control algorithm to keep the combustion phase stable in the target range.

[0018] It has self-diagnosis and mode switching functions to ensure safe system operation.

[0019] The specific technical solution of the present invention to achieve the above objectives is a methanol-diesel dual-fuel combustion method with staged injection organization, comprising the following steps:

[0020] (1) Methanol is heated to 40-70℃ by a heater before injection;

[0021] (2) Methanol main injection is performed in the early or middle stage of the intake stroke, and the main injection volume accounts for 70%-90% of the total methanol injection volume;

[0022] (3) Methanol supplementary injection is performed in the later stage of the compression stroke, and the supplementary injection amount accounts for 10%-30% of the total methanol injection amount;

[0023] (4) A small amount of diesel fuel is injected near the top dead center of the compression stroke, and its energy accounts for 3%-10% of the total fuel energy;

[0024] (5) Real-time acquisition of cylinder pressure signals and calculation of multi-cycle average combustion center angle CA50;

[0025] (6) Based on the deviation between CA50 and the target value, adaptively correct the supplementary injection timing.

[0026] It should be noted that the entire method (i.e., the staged injection-organized methanol-diesel dual-fuel combustion method) includes a main injection stage, a supplementary injection stage, and a diesel micro-ignition stage. The main methanol injection is performed in the early or middle of the intake stroke (30-150°C after the start of the intake stroke), accounting for 70%–90% of the total methanol injection, and is used to form a basic homogeneous mixture. The supplementary methanol injection is performed in the late compression stroke (10-40°C before top dead center), accounting for 10%–30% of the total methanol injection, and is used to regulate the local equivalence ratio distribution within the cylinder. Diesel injection is performed near top dead center, accounting for 3%–10% of the total fuel energy, and is used to form the initial combustion nucleus. Simultaneously, the methanol is heated by a methanol heater before injection, with the heating temperature controlled at 40-70°C, to increase the evaporation rate and reduce methanol impact on the combustion walls.

[0027] In other words, the main methanol injection is completed within the range of 30-150°CA after the start of the intake stroke, and the supplementary methanol injection is completed within the range of 10-40°CA before the top dead center of the compression stroke.

[0028] The correction of the injection timing employs a proportional-integral (PI) closed-loop control algorithm, which is based on the error... As input, the output is the timing correction amount for the additional injection. The expression:

[0029]

[0030] In the formula, This represents the error input at the current moment, where k indicates the current moment (it should be noted that "k" and "k-1" are used to distinguish between the current calculation round and the previous calculation round). This is the proportional gain coefficient. This is the integral gain coefficient. To control the signal update cycle;

[0031] The staged injection combustion method involves real-time acquisition of cylinder pressure signals and calculation of the multi-cycle combustion center angle CA50. The acquired and calculated results are then compared with the target value. When the deviation exceeds a set threshold, adaptive correction of the injection timing is performed to bring the combustion center angle back to the target range.

[0032] The control unit of the staged injection combustion regulation method employs a proportional-integral (PI) closed-loop control algorithm, outputting a supplementary injection timing correction based on the magnitude of the combustion center angle deviation; using the error... As the input, the timing correction for the supplementary injection is calculated according to the PI control law. ;in, For the target combustion center angle, The average combustion center angle over multiple cycles is typically calculated using 100 cycles. This is the proportional gain coefficient. This is the integral gain coefficient. To control the signal update cycle.

[0033] When the cylinder pressure signal is abnormal or the sensor is detected to be malfunctioning, the system automatically switches to single-stage methanol injection mode.

[0034] A methanol-diesel dual-fuel combustion device with a staged injection mechanism, the device being used to implement the steps of the method according to any one of claims 1 to 6, comprising:

[0035] The methanol injection system includes a main injection unit and a supplementary injection unit;

[0036] Diesel injection system;

[0037] Methanol heater;

[0038] Signal acquisition system;

[0039] The control unit is used to execute the injection logic and adaptive corrections.

[0040] The methanol injection system includes a main injection unit and a supplementary injection unit. The main injection unit uses a manifold injection valve or an intake manifold injection valve, which is suitable for large-dose methanol injection. The supplementary injection unit uses an in-cylinder direct injection valve for small-dose precise injection at the end of compression. Diesel injection uses in-cylinder direct injection. The methanol heater is connected to the liquid supply lines of the main injection unit and the supplementary injection unit, and is heated by cylinder liner water. After heating, the methanol temperature is about 60°C. The control unit includes a limiting module and a rate limiting module to suppress transient changes in injection phase adjustment.

[0041] The main injection unit uses an intake manifold injection valve, and the supplementary injection unit uses a cylinder direct injection valve.

[0042] The methanol heater uses cylinder liner water for heating.

[0043] The control unit includes a limiting module and a rate limiting module, used to suppress transient fluctuations in the injection phase adjustment.

[0044] It should be noted that achieving precise organization of methanol-diesel dual-fuel combustion requires a reasonable balance between mixture homogeneity, fuel injection phase matching, and combustion phase control. The supplementary injection volume is smaller, and its injection phase control precision requirements are far higher than traditional injection strategies. To achieve reliable closed-loop combustion phase regulation, it is necessary to integrate real-time acquisition and analysis of cylinder pressure signals, rapid calculation of the combustion center angle CA50, and stable design of the control algorithm. Simultaneously, the increased risk of knocking due to cylinder pressure fluctuations during transient adjustments must be addressed. Therefore, the controller needs to possess adaptive adjustment capabilities to cope with potential cyclic fluctuations during methanol combustion, ensuring the smoothness and reliability of the adjustment process.

[0045] Correction amount for re-spraying timing Implement rate limiting to prevent rapid changes in ignition advance angle that could lead to engine instability.

[0046]

[0047] in, This is the rate limiting factor (unit: °CA / s).

[0048] Compared with the prior art, the technical solution disclosed in this application has the following non-obvious technical features:

[0049] First, this application adopts a staged methanol injection organization, which divides methanol injection into two stages: main injection (intake stage) and supplementary injection (compression end stage). Through supplementary injection, the distribution of the in-cylinder mixture is finely adjusted in real time, which significantly improves the uniformity of the mixture and the controllability of combustion.

[0050] Second, this application realizes closed-loop control based on combustion center angle (CA50). CA50 is calculated by real-time cylinder pressure signal and compared with target value. The PI control algorithm is used to dynamically correct the injection timing to achieve adaptive and stable control of combustion phase.

[0051] Third, this application employs a precise methanol heating and temperature control mechanism, setting up a methanol heater and controlling the injection temperature at 40–70°C, which effectively increases the methanol evaporation rate, reduces liquid film formation, and improves mixing quality.

[0052] Fourth, this application sets up a fail-safe mechanism. When an abnormal cylinder pressure signal or sensor failure is detected, the system automatically switches to single-stage injection mode or fixed parameter mode to ensure the basic operational safety of the engine.

[0053] Fifth, this application adopts a dynamic correction mechanism for the timing of the supplementary spray: using a multi-cycle average CA50 as the control input, combined with the amplitude limiting and rate limiting modules, to avoid instantaneous fluctuations during the adjustment process and improve system stability.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. This invention improves combustion stability by significantly suppressing combustion cycle fluctuations and enhancing engine running smoothness through staged injection and closed-loop control;

[0056] 2. This invention improves emission performance, optimizes the mixture distribution and combustion process, reduces NOx and particulate matter emissions, and enhances environmental performance;

[0057] 3. This invention improves the methanol substitution ratio. Under the premise of ensuring reliable ignition and stable combustion, it can further increase the proportion of methanol in the total fuel and reduce diesel consumption.

[0058] 4. This invention enhances the system's adaptability to different operating conditions. The adaptive control mechanism enables the system to cope with changes in different loads, speeds, and ambient temperatures, thus expanding the engine's operating range.

[0059] 5. This invention improves system security, has fault diagnosis and mode switching functions, and enhances system robustness and reliability;

[0060] 6. This invention effectively simplifies the system structure. Through integrated control units and modular design, it reduces system complexity and facilitates engineering implementation and maintenance. Attached Figure Description

[0061] Figure 1 This is a flowchart of the method described in Embodiment 1 of the present invention;

[0062] Figure 2 This is a schematic diagram of the device described in Embodiment 2 of the present invention. Detailed Implementation

[0063] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0064] Example 1:

[0065] A staged injection-organized methanol-diesel dual-fuel combustion method, the process of which is as follows: Figure 1 As shown, the method employs an injection strategy combining main injection, supplementary injection, and diesel micro-ignition to improve the evaporation and mixing process of methanol in the cylinder. It also achieves closed-loop management of the combustion process by adjusting the supplementary injection timing through feedback control based on the combustion phase. The method includes the following steps:

[0066] (1) Methanol is heated to 40-70℃ by a heater before injection;

[0067] (2) Methanol main injection is performed in the early or middle stage of the intake stroke, and the main injection volume accounts for 70%-90% of the total methanol injection volume;

[0068] (3) Methanol supplementary injection is performed in the later stage of the compression stroke, and the supplementary injection amount accounts for 10%-30% of the total methanol injection amount;

[0069] (4) A small amount of diesel fuel is injected near the top dead center of the compression stroke, and its energy accounts for 3%-10% of the total fuel energy;

[0070] (5) Real-time acquisition of cylinder pressure signals and calculation of multi-cycle average combustion center angle CA50;

[0071] (6) Based on the deviation between CA50 and the target value, adaptively correct the supplementary injection timing.

[0072] During the main injection phase, a larger volume of methanol is injected in the early intake stage to promote fuel evaporation and form a basic homogeneous mixture using intake flow. At the end of compression, a smaller volume and precise timing of supplementary injection is performed to adjust local fuel concentration and optimize methanol distribution. Micro-injected diesel fuel serves as the ignition nucleus, providing active free radicals and ensuring ignition reliability. To address the high latent heat of methanol vaporization, this method introduces a methanol heater to improve evaporation quality, reduce the formation of liquid films in the intake manifold and cylinder walls, thereby reducing combustion lag and heat release concentration, and maintaining consistent methanol supply under varying ambient temperatures.

[0073] It should be noted that the main methanol injection is completed within the range of 30-150℃A after the start of the intake stroke, and the supplementary methanol injection is completed within the range of 10-40℃A before the top dead center of the compression stroke.

[0074] Furthermore, the correction of the injection timing employs a proportional-integral (PI) closed-loop control algorithm, which is based on the error... As input, the output is the timing correction amount for the additional injection. The expression:

[0075]

[0076] In the formula, This is the proportional gain coefficient. This is the integral gain coefficient. To control the signal update cycle.

[0077] When the cylinder pressure signal is abnormal or the sensor is detected as malfunctioning, the system automatically switches to a single-stage methanol injection mode. This method calculates the multi-cycle average combustion center angle CA50 by collecting cylinder pressure signals and adaptively corrects the deviation between CA50 and the target value using a PI control algorithm. This stabilizes the combustion phase within a preset range, thereby suppressing the impact of cycle fluctuations on the combustion process, improving combustion stability, and expanding the operating condition adaptability range. The implementation of this application overcomes the shortcomings of single-stage injection and open-loop control in mixture preparation and combustion regulation, improving the controllability, stability, and efficiency of the dual-fuel combustion process.

[0078] Example 2:

[0079] A methanol-diesel dual-fuel combustion device with a staged injection system, the structure of which is as follows: Figure 2 As shown, the apparatus is used to implement the steps of the method described in Embodiment 1, and the apparatus includes:

[0080] The methanol injection system includes a main injection unit and a supplementary injection unit;

[0081] Diesel injection system;

[0082] Methanol heater;

[0083] Signal acquisition system;

[0084] The control unit is used to execute the injection logic and adaptive corrections.

[0085] The methanol injection system includes a main injection unit and a supplementary injection unit. The main injection unit uses a manifold injection valve or an intake manifold injection valve, which is suitable for large-dose methanol injection. The supplementary injection unit uses an in-cylinder direct injection valve for small-dose precise injection at the end of compression. Diesel injection uses in-cylinder direct injection. The methanol heater is connected to the liquid supply lines of the main injection unit and the supplementary injection unit, and is heated by cylinder liner water. After heating, the methanol temperature is about 60°C. The control unit includes a limiting module and a rate limiting module to suppress transient changes in injection phase adjustment.

[0086] The main injection unit uses an intake manifold injection valve, and the supplementary injection unit uses a cylinder direct injection valve.

[0087] The methanol heater uses cylinder liner water for heating.

[0088] The control unit includes a limiting module and a rate limiting module, used to suppress transient fluctuations in the injection phase adjustment.

[0089] Example 3:

[0090] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in Embodiment 1. Everything else is the same as in Embodiment 1.

[0091] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0092] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A methanol-diesel dual-fuel combustion method with staged injection organization, characterized in that, Includes the following steps: (1) Methanol is heated to 40-70℃ by a heater before injection; (2) Methanol main injection is performed in the early or middle stage of the intake stroke, and the main injection volume accounts for 70%-90% of the total methanol injection volume; (3) Methanol supplementary injection is performed in the later stage of the compression stroke, and the supplementary injection amount accounts for 10%-30% of the total methanol injection amount; (4) A small amount of diesel fuel is injected near the top dead center of the compression stroke, and its energy accounts for 3%-10% of the total fuel energy; (5) Real-time acquisition of cylinder pressure signals and calculation of multi-cycle average combustion center angle CA50; (6) Based on the deviation between CA50 and the target value, adaptively correct the supplementary injection timing.

2. The method according to claim 1, characterized in that, The main methanol injection is completed within the range of 30-150°C after the start of the intake stroke.

3. The method according to claim 1, characterized in that, The methanol injection is completed within the range of 10-40°CA before the top dead center of the compression.

4. The method according to claim 1, characterized in that, The correction of the supplementary injection timing adopts a proportional-integral (PI) closed-loop control algorithm.

5. The method according to claim 1, characterized in that, The proportional-integral (PI) closed-loop control algorithm is based on error. As input, the output is the timing correction amount for the additional injection. The expression: In the formula, This is the error input at the current moment. This is the proportional gain coefficient. This is the integral gain coefficient. To control the signal update cycle.

6. The method according to claim 1, characterized in that, When the cylinder pressure signal is abnormal or the sensor is detected to be malfunctioning, the system automatically switches to single-stage methanol injection mode.

7. A methanol-diesel dual-fuel combustion device with a staged injection mechanism, the device being used to implement the steps of the method according to any one of claims 1 to 6, characterized in that, include: The methanol injection system includes a main injection unit and a supplementary injection unit; Diesel injection system; Methanol heater; Signal acquisition system; The control unit is used to execute the injection logic and adaptive corrections.

8. The apparatus according to claim 7, characterized in that, The main injection unit uses an intake manifold injection valve, and the supplementary injection unit uses a cylinder direct injection valve.

9. The apparatus according to claim 8, characterized in that, The methanol heater uses cylinder liner water for heating.

10. The apparatus according to claim 9, characterized in that, The control unit includes a limiting module and a rate limiting module, used to suppress transient fluctuations in the injection phase adjustment.

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