High efficiency ignition control method for liquid ammonia-diesel direct injection internal combustion engine

Abstract

The present application aims to provide a high-efficiency ignition control method suitable for a liquid ammonia-diesel cylinder direct injection internal combustion engine, which comprises a cylinder head, a cylinder sleeve, a piston, an intake valve, an exhaust valve, an electronic control unit, various sensors for measuring the state parameters of the internal combustion engine, etc. The electronic control unit automatically selects a suitable fuel injection mode based on the state parameters of the internal combustion engine, realizing stable operation of the dual-fuel internal combustion engine under variable conditions. When the internal combustion engine is in the starting stage or the idling stage, it runs in the pure diesel mode; when the internal combustion engine is in the medium and low load stage, it runs in the low-ammonia-doped mode; and when the internal combustion engine is in the high load stage, it runs in the high-ammonia-doped mode. When the internal combustion engine adopts the low-ammonia-doped mode or the high-ammonia-doped mode, the fuel injection quantity and injection pressure can be adjusted according to the state parameters of the internal combustion engine, realizing dynamic optimization of the interaction between the liquid ammonia spray and the diesel spray in the cylinder of the internal combustion engine, ensuring the ignition success rate and the combustion efficiency, and effectively solving the problem of difficult ignition of ammonia fuel.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engines, and more specifically to a high-efficiency ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines. Background Technology

[0002] Ammonia, with its low storage and transportation costs and high octane number, is considered a promising alternative fuel for internal combustion engines. However, ammonia fuel is characterized by low flame propagation speed, long ignition delay time, high auto-ignition temperature, and narrow flammability range. To improve the low flammability of ammonia in internal combustion engines, researchers have proposed optimization strategies for ammonia-diesel dual-fuel combustion.

[0003] Currently, ammonia-diesel dual-fuel internal combustion engines can be classified into two types based on the ammonia supply method: low-pressure injection dual-fuel (LPDF) combustion mode and high-pressure injection dual-fuel (HPDF) combustion mode. In LPDF combustion mode, low-pressure gaseous / liquid ammonia mixes with air in the intake manifold before entering the cylinder, forming an ammonia-air mixture, which is then ignited by diesel fuel spray. In HPDF combustion mode, high-pressure liquid ammonia is injected directly into the cylinder after diesel fuel injection and is subsequently ignited by the diesel fuel spray.

[0004] Compared to the LPDF combustion mode, the HPDF combustion mode has the potential to improve the charge coefficient, compression ratio, ammonia substitution rate, and reduce ammonia slip. Studies have shown that the ignition-combustion process of an ammonia-diesel HPDF engine is directly related to the interaction between liquid ammonia spray and diesel spray. Because ammonia has an auto-ignition temperature as high as 924K, the high-temperature zone of the diesel spray flame needs to interact with the liquid ammonia spray to ensure ignition success rate and combustion efficiency. During internal combustion engine operation, the load affects the injection quantity and injection pressure, thereby changing the interaction zone between liquid ammonia spray and diesel spray; however, existing patents do not address the dynamic optimization of the in-cylinder interaction between liquid ammonia spray and diesel spray in internal combustion engines. Summary of the Invention

[0005] Based on the above background, the purpose of this invention is to provide an efficient ignition control method suitable for liquid ammonia-diesel direct injection internal combustion engines, to achieve stable operation of dual-fuel internal combustion engines under varying operating conditions, to ensure ignition success rate and combustion efficiency, and to effectively solve the problem of difficult ignition of ammonia fuel in compression ignition internal combustion engines.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A highly efficient ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines:

[0008] The internal combustion engine includes: a cylinder head, a cylinder liner, a piston, an electronic control unit, and various sensors for measuring the state parameters of the internal combustion engine. The cylinder head is mounted on the cylinder liner, and the piston is movably mounted in the inner cavity of the cylinder liner. The cylinder head is equipped with a diesel injector and a liquid ammonia injector. The nozzles of the diesel injector and the liquid ammonia injector extend into the inner cavity of the cylinder liner. The electronic control unit controls the diesel injector and the liquid ammonia injector, and also controls the various sensors.

[0009] The electronic control unit determines the current operating stage of the internal combustion engine based on the parameters collected by the sensors;

[0010] The appropriate fuel injection mode is selected based on the current operating stage of the internal combustion engine, wherein...

[0011] When the internal combustion engine is in the starting or idling stage, it operates in pure diesel mode; when the internal combustion engine is in the low-to-medium load stage, it operates in low ammonia blending mode; when the internal combustion engine is in the high load stage, it operates in high ammonia blending mode.

[0012] The highly efficient ignition control method described above, further:

[0013] In the pure diesel mode, when the piston reaches 10° before top dead center to 10° after top dead center, the electronic control unit controls the diesel injector to inject diesel fuel. The electronic control unit calculates the required diesel injection quantity and injection pressure based on the parameters collected by the sensor.

[0014] The highly efficient ignition control method described above, further:

[0015] In the low-ammonia blending mode, the liquid ammonia injection quantity accounts for 30%-60% of the total fuel energy fraction. In the low-ammonia blending mode, when the piston reaches 0°-10° before top dead center, the electronic control unit controls the diesel injector to perform main injection, accounting for 70%-90% of the diesel injection quantity; when the piston reaches 5° before top dead center to 15° after top dead center, the electronic control unit controls the liquid ammonia injector to perform main injection; when the piston reaches 15°-20° after top dead center, the electronic control unit controls the diesel injector to perform post-injection, accounting for 10%-30% of the diesel injection quantity.

[0016] The highly efficient ignition control method described above, further:

[0017] In the high-ammonia blending mode, the liquid ammonia injection quantity accounts for 60%-95% of the total fuel energy fraction. When the piston reaches 5°-10° before top dead center, the electronic control unit controls the diesel injector to pre-inject, accounting for 50%-70% of the diesel injection quantity. When the piston reaches 5° before top dead center to 15° after top dead center, the electronic control unit controls the liquid ammonia injector to perform main injection. When the piston reaches 15°-20° after top dead center, the electronic control unit controls the diesel injector to perform post-injection, accounting for 30%-50% of the diesel injection quantity.

[0018] The highly efficient ignition control method described above, further:

[0019] When the internal combustion engine adopts a low ammonia blending mode or a high ammonia blending mode, the electronic control unit calculates the required fuel injection quantity based on the various parameters collected by the sensor, and calculates the flame rise height of the diesel spray according to the semi-empirical formula obtained from experimental calibration.

[0020] The highly efficient ignition control method described above, further:

[0021] By adjusting the diesel injection pressure, the high-temperature zone of the diesel spray flame interacts with the liquid ammonia spray, thereby ensuring the ignition effect.

[0022] The highly efficient ignition control method described above, further:

[0023] When the electronic control unit detects a change in the load of the internal combustion engine, it determines whether it is necessary to switch the fuel injection mode. If the fuel injection mode does not need to be changed, it recalculates the fuel injection quantity and adjusts the diesel injection pressure to achieve dynamic optimization of the interaction between liquid ammonia spray and diesel spray.

[0024] The highly efficient ignition control method described above, further:

[0025] The electronic control unit calculates the ammonia slip rate based on the ammonia concentration in the exhaust gas. When the ammonia slip rate exceeds the threshold, the diesel fuel injection volume is increased to improve the combustion efficiency of ammonia.

[0026] The highly efficient ignition control method described above, further:

[0027] The liquid ammonia injection quantity and diesel injection quantity under different loads can be obtained through calibration experiments and stored in the electronic control unit, and then corrected according to the actual operating conditions of the internal combustion engine.

[0028] The highly efficient ignition control method described above, further:

[0029] The cylinder head is also provided with an intake valve and an exhaust valve, and the intake valve and the exhaust valve are respectively equipped with an intake valve and an exhaust valve, and the electronic control unit controls the intake valve and the exhaust valve with a control signal.

[0030] Compared with the prior art, the advantages of this invention are as follows:

[0031] (1) Based on the internal combustion engine state parameters, the appropriate fuel injection mode is automatically selected to realize the stable operation of the dual-fuel internal combustion engine under varying working conditions.

[0032] (2) When the internal combustion engine is in dual-fuel injection mode, the amount of fuel injected and the injection pressure can be adjusted according to the state parameters of the internal combustion engine to achieve dynamic optimization of the interaction between liquid ammonia spray and diesel spray in the internal combustion engine cylinder, and ensure ignition success rate and combustion efficiency.

[0033] (3) Effectively solves the problem of difficult ignition of ammonia fuel in compression-ignition internal combustion engines.

[0034] (4) It is applicable not only to liquid ammonia-diesel internal combustion engines, but also to other types of liquid ammonia-liquid fuel internal combustion engines, such as liquid ammonia-methanol internal combustion engines. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of the internal combustion engine structure used for a high-efficiency ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines;

[0037] Figure 2 A flowchart illustrating the efficient ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines;

[0038] Figure 3 Fuel injection flow rate diagram during the start-up or idling phases for an efficient ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines;

[0039] Figure 4 Fuel injection flow rate diagram for a high-efficiency ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines at medium and low loads;

[0040] Figure 5 Fuel injection flow rate diagram during high-load phase for an efficient ignition control method applicable to liquid ammonia-diesel direct injection internal combustion engines. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] Example:

[0043] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, in the embodiments of this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0044] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0045] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] The present invention relates to a high-efficiency ignition control method for liquid ammonia-diesel direct injection internal combustion engines. A schematic diagram of the internal combustion engine structure used in this method is shown below. Figure 1As shown in the figure, the internal combustion engine used in this invention includes a cylinder head 1, a cylinder liner 2, a piston 3, an intake valve 4, an exhaust valve 5, an electronic control unit 6, and various sensors for measuring the state parameters of the internal combustion engine. As shown, the cylinder head is mounted on the cylinder liner, and the piston is movably mounted within the cylinder liner's inner cavity. The cylinder head is equipped with a diesel injector and a liquid ammonia injector, the nozzles of which extend into the inner cavity of the cylinder liner (between the cylinder head and the piston). The electronic control unit connects control signals to the diesel injector and the liquid ammonia injector.

[0047] As an optional implementation, in some embodiments, the cylinder head is provided with mounting holes reserved for diesel injector 7 and liquid ammonia injector 8, and the nozzles of diesel injector 7 and liquid ammonia injector 8 are respectively installed in the mounting holes.

[0048] As an alternative implementation, in some embodiments, the central axes of the two nozzles form an angle of 30°-60° within the cylinder.

[0049] As an alternative implementation, in some embodiments, the nozzles of both the diesel injector and the liquid ammonia injector are single-hole nozzles, and the two nozzles are arranged symmetrically. Since the calorific value per unit mass of liquid ammonia is approximately one-third that of diesel, the liquid ammonia nozzle typically has a larger diameter to provide a greater flow rate.

[0050] As an optional implementation, in some embodiments, the cylinder head is further provided with an intake valve and an exhaust valve, and the intake valve and exhaust valve are respectively equipped with an intake valve and an exhaust valve, and the electronic control unit control signal is connected to the intake valve and the exhaust valve.

[0051] As an optional implementation, the sensors may include speed sensors, component concentration sensors, temperature sensors, pressure sensors, etc. The diesel injector 7, the liquid ammonia injector 8, and various sensors are connected to the electronic control unit 6.

[0052] It should be noted that the control method in this embodiment is also applicable to different nozzle arrangement schemes.

[0053] The control method of this embodiment is described below:

[0054] See Figure 2 The electronic control unit 6 determines the current operating stage of the internal combustion engine based on the various parameters collected by the sensors, and selects the appropriate fuel injection mode, namely: pure diesel mode, low ammonia blending mode or high ammonia blending mode, to achieve stable operation of the internal combustion engine under varying operating conditions.

[0055] When the internal combustion engine is in the starting or idling phase, it operates in pure diesel mode. When piston 3 moves 10° before to 10° after top dead center, the electronic control unit 6 controls the diesel injector 7 to inject fuel. The electronic control unit 6 calculates the required diesel injection quantity and pressure based on various parameters collected by sensors. The fuel injection flow diagram for this mode is shown below. Figure 3 As shown.

[0056] When the internal combustion engine is under low to medium load, it operates in a low-ammonia blending mode. This low-ammonia blending mode refers to a fuel injection mode where liquid ammonia injection accounts for 30%-60% of the total fuel energy fraction. The ammonia blending ratio increases with the engine load. When piston 3 reaches 0°-10° before top dead center, the electronic control unit 6 controls diesel injector 7 for main injection (accounting for 70%-90% of the diesel injection quantity); when piston 3 reaches 5° before to 15° after top dead center, the electronic control unit 6 controls liquid ammonia injector 8 for main injection; when piston 3 reaches 15°-20° after top dead center, the electronic control unit 6 controls diesel injector 7 for post-injection (accounting for 10%-30% of the diesel injection quantity). The fuel injection flow diagram for this mode is shown below. Figure 4 As shown.

[0057] When the internal combustion engine is under high load, it operates in a high ammonia blending mode. This high ammonia blending mode refers to a fuel injection mode where liquid ammonia injection accounts for 60%-95% of the total fuel energy fraction, and the ammonia blending ratio increases with the engine load. When piston 3 reaches 5°-10° before top dead center, the electronic control unit 6 controls diesel injector 7 for pre-injection (accounting for 50%-70% of the diesel injection quantity); when piston 3 reaches 5° before top dead center to 15° after top dead center, the electronic control unit 6 controls liquid ammonia injector 8 for main injection; and when piston 3 reaches 15°-20° after top dead center, the electronic control unit 6 controls diesel injector 7 for post-injection (accounting for 30%-50% of the diesel injection quantity). The fuel injection flow diagram for this mode is shown below. Figure 5 As shown.

[0058] When the internal combustion engine adopts a low ammonia blending mode or a high ammonia blending mode, the electronic control unit 3 calculates the required fuel injection quantity based on the various parameters collected by the sensors, and calculates the flame rise height of the diesel spray according to the semi-empirical formula obtained from the experimental calibration.

[0059] In some embodiments of the application, the flame lift height (LOL) of the diesel spray can be calculated by the following formula:

[0060]

[0061] Among them, T a ρ is the temperature of the gas inside the cylinder. a Y is the gas density inside the cylinder. O2 The oxygen concentration inside the cylinder is measured by a sensor; c0-c4 are empirical constants obtained from calibration experimental data. thThe theoretical jet velocity at the nozzle is calculated using the following formula:

[0062]

[0063] Where ΔP is the difference between the injection pressure and the in-cylinder ambient pressure, ρ f Fuel density.

[0064] It is worth noting that the flame rise height of the diesel spray can be calculated using other forms of semi-empirical formulas.

[0065] By adjusting the diesel injection pressure, the high-temperature zone of the diesel spray flame interacts with the liquid ammonia spray, thus ensuring ignition effectiveness. Simultaneously, to guarantee atomization, the diesel injection pressure should generally not be lower than 120 MPa. At this point, the following relationship exists:

[0066] LOL = K·L

[0067] Where L is the distance from the diesel nozzle to the intersection of the central axes of the two nozzles; K is a correction factor considering the diesel atomization effect and the liquid ammonia ignition effect under different loads, which is obtained from calibration experimental data.

[0068] When the electronic control unit 6 detects a change in the internal combustion engine load, it determines whether a change in fuel injection mode is necessary. If the fuel injection mode does not need to be changed, it recalculates the injection quantity and adjusts the diesel injection pressure to achieve dynamic optimization of the interaction between liquid ammonia spray and diesel spray. The electronic control unit 6 calculates the ammonia slip rate based on the ammonia concentration in the exhaust gas. When the ammonia slip rate exceeds a threshold, it increases the diesel post-injection quantity to improve the combustion efficiency of ammonia.

[0069] The liquid ammonia injection quantity and diesel injection quantity under different loads mentioned above can be obtained through calibration experiments and stored in the electronic control unit 6, and then corrected according to the actual operating conditions of the internal combustion engine.

[0070] In summary, this invention automatically selects the appropriate fuel injection mode based on the internal combustion engine's state parameters, achieving stable operation of a dual-fuel internal combustion engine under varying operating conditions. When the internal combustion engine is in dual-fuel injection mode, the injection quantity and injection pressure can be adjusted according to the engine's state parameters to achieve dynamic optimization of the interaction between in-cylinder liquid ammonia spray and diesel spray, ensuring ignition success rate and combustion efficiency. This effectively solves the problem of difficult ignition of ammonia fuel in compression-ignition internal combustion engines. It is not only applicable to liquid ammonia-diesel internal combustion engines but also to other types of liquid ammonia-liquid fuel internal combustion engines, such as liquid ammonia-methanol internal combustion engines.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency ignition control method, applicable to liquid ammonia-diesel direct injection internal combustion engines, characterized in that: The internal combustion engine includes: a cylinder head, a cylinder liner, a piston, an electronic control unit, and various sensors for measuring the state parameters of the internal combustion engine. The cylinder head is mounted on the cylinder liner, and the piston is movably mounted in the inner cavity of the cylinder liner. The cylinder head is equipped with a diesel injector and a liquid ammonia injector. The nozzles of the diesel injector and the liquid ammonia injector extend into the inner cavity of the cylinder liner. The electronic control unit controls the diesel injector and the liquid ammonia injector, and also controls the various sensors. The electronic control unit determines the current operating stage of the internal combustion engine based on the parameters collected by the sensors; The appropriate fuel injection mode is selected based on the current operating stage of the internal combustion engine, wherein... When the internal combustion engine is in the starting or idling stage, it operates in pure diesel mode; when the internal combustion engine is in the low-to-medium load stage, it operates in low-ammonia blending mode; when the internal combustion engine is in the high load stage, it operates in high-ammonia blending mode. In the low-ammonia blending mode, the liquid ammonia injection quantity accounts for 30%-60% of the total fuel energy fraction. In the low-ammonia blending mode, when the piston reaches 0°-10° before top dead center, the electronic control unit controls the diesel injector to perform main injection, accounting for 70%-90% of the diesel injection quantity; when the piston reaches 5° before top dead center to 15° after top dead center, the electronic control unit controls the liquid ammonia injector to perform main injection; when the piston reaches 15°-20° after top dead center, the electronic control unit controls the diesel injector to perform post-injection, accounting for 10%-30% of the diesel injection quantity.

2. The high-efficiency ignition control method according to claim 1, characterized in that: In the pure diesel mode, when the piston reaches 10° before top dead center to 10° after top dead center, the electronic control unit controls the diesel injector to inject diesel fuel. The electronic control unit calculates the required diesel injection quantity and injection pressure based on the parameters collected by the sensor.

3. The high-efficiency ignition control method according to claim 1, characterized in that: In the high-ammonia blending mode, the liquid ammonia injection quantity accounts for 60%-95% of the total fuel energy fraction. When the piston reaches 5°-10° before top dead center, the electronic control unit controls the diesel injector to pre-inject, accounting for 50%-70% of the diesel injection quantity. When the piston reaches 5° before top dead center to 15° after top dead center, the electronic control unit controls the liquid ammonia injector to perform main injection. When the piston reaches 15°-20° after top dead center, the electronic control unit controls the diesel injector to perform post-injection, accounting for 30%-50% of the diesel injection quantity.

4. The high-efficiency ignition control method according to claim 1 or 3, characterized in that: When the internal combustion engine adopts a low ammonia blending mode or a high ammonia blending mode, the electronic control unit calculates the required fuel injection quantity based on the various parameters collected by the sensor, and calculates the flame rise height of the diesel spray according to the semi-empirical formula obtained from experimental calibration.

5. The high-efficiency ignition control method according to claim 4, characterized in that: By adjusting the diesel injection pressure, the high-temperature zone of the diesel spray flame interacts with the liquid ammonia spray, thereby ensuring the ignition effect.

6. The high-efficiency ignition control method according to claim 5, characterized in that: When the electronic control unit detects a change in the load of the internal combustion engine, it determines whether it is necessary to switch the fuel injection mode. If the fuel injection mode does not need to be changed, it recalculates the fuel injection quantity and adjusts the diesel injection pressure to achieve dynamic optimization of the interaction between liquid ammonia spray and diesel spray.

7. The high-efficiency ignition control method according to claim 6, characterized in that: The electronic control unit calculates the ammonia slip rate based on the ammonia concentration in the exhaust gas. When the ammonia slip rate exceeds the threshold, the diesel fuel injection volume is increased to improve the combustion efficiency of ammonia.

8. The high-efficiency ignition control method according to claim 1 or 2, characterized in that: The liquid ammonia injection quantity and diesel injection quantity under different loads can be obtained through calibration experiments and stored in the electronic control unit, and then corrected according to the actual operating conditions of the internal combustion engine.

9. The high-efficiency ignition control method according to claim 1, characterized in that: The cylinder head is also provided with an intake valve and an exhaust valve, and the intake valve and the exhaust valve are respectively equipped with an intake valve and an exhaust valve, and the electronic control unit controls the intake valve and the exhaust valve with a control signal.

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