A methanol diesel dual-nozzle dual-direct-injection engine and a control method thereof
By designing and controlling a methanol-diesel dual-nozzle dual-direct-injection engine, the problems of low thermal efficiency and high emissions of methanol engines have been solved, achieving efficient and clean combustion and stable operation, thus meeting the carbon neutrality target.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGXI YUCHAI MASCH CO LTD
- Filing Date
- 2023-12-29
- Publication Date
- 2026-07-14
AI Technical Summary
Existing methanol engines suffer from low thermal efficiency and high emissions of harmful pollutants, and the methanol substitution rate is affected by knocking, making it difficult to achieve the goal of carbon neutrality.
The engine employs a dual-nozzle, dual-direct-injection methanol-diesel system, which supplies diesel and methanol through a low-pressure fuel pump and a high-pressure fuel pump system, respectively. The diesel injectors are arranged at an angle, while the methanol nozzles are arranged coaxially. By combining different fuel injection modes, including diesel micro-ignition and methanol diffusion combustion under medium and high loads and premixed combustion under low loads, the system achieves efficient mixing and combustion of methanol and diesel.
It achieves improved thermal efficiency and reduced emissions without sacrificing power, ensures stable engine operation under different loads, reduces formaldehyde and unburned methanol emissions, and meets the carbon neutrality target.
Smart Images
Figure CN117869087B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of engine technology, and more specifically, to a methanol-diesel dual-nozzle dual-direct-injection engine and its control method. Background Technology
[0002] Methanol has a high octane number and latent heat of vaporization, and its flame propagation speed is higher than that of gasoline, which helps to suppress knocking and improve thermal efficiency. Methanol molecules contain up to 50% oxygen, and its combustion process produces almost no soot. As the world's largest producer and consumer of methanol, my country has long considered methanol a key energy source. With the rapid development of renewable energy in my country, the use of renewable energy sources such as wind and solar power to generate green hydrogen, and then combining it with CO2 obtained from industrial waste gases to synthesize safe and easily transportable methanol fuel, can be achieved. The CO2 produced after combustion in internal combustion engines can then be used again as a raw material for methanol synthesis, thus achieving zero carbon emissions throughout its entire life cycle.
[0003] Currently, methanol is mainly used in internal combustion engines, either alone or blended with other fuels, achieving ignition and combustion through spark plugs or dual-fuel diesel ignition. In spark-ignition engines, due to methanol's high octane rating, large latent heat of vaporization, and fast flame propagation speed, pure methanol combustion can significantly improve anti-knock properties, thermal efficiency, and emissions. However, it also faces challenges such as difficult cold starts, poor combustion stability under low loads, and limitations in thermal efficiency due to knocking. In dual-fuel diesel-ignited methanol engines, the current domestic approach mainly uses methanol port / manifold premixing combined with diesel direct injection ignition. This combustion mode can achieve thermal efficiency comparable to diesel engines, but the methanol substitution rate is affected by knocking and decreases with increasing load. Due to the low methanol substitution rate, the carbon neutrality target cannot be achieved.
[0004] The methanol-diesel dual direct injection engine operates on a combustion principle similar to a diesel engine. A small amount of diesel fuel is injected to create an ignition source, followed by the injection of high-pressure methanol, which mixes with high-temperature, high-pressure air to form a combustible mixture. When this mixture encounters the micro-ignition source, it ignites spontaneously and expands rapidly, pushing the piston downwards to perform work. Throughout this process, diesel fuel provides the ignition source, while methanol is the primary fuel, with a methanol substitution rate exceeding 90%. Methanol has a fast combustion rate and good anti-knock properties. Furthermore, high-pressure injection increases the uniformity of the mixture, further enhancing the combustion rate. Therefore, the methanol-diesel dual direct injection engine can achieve higher thermal efficiency and lower emissions than diesel engines without sacrificing power performance, representing a key route for reducing carbon emissions and promoting efficient, clean combustion in internal combustion engines.
[0005] However, existing methanol engines still suffer from technical problems such as low thermal efficiency and high emissions of harmful pollutants. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to address the above-mentioned shortcomings of the prior art. The objective of the present invention is to provide a methanol-diesel dual-nozzle dual-direct-injection engine.
[0007] The second objective of this invention is to provide a control method for a methanol-diesel dual-nozzle dual-direct-injection engine.
[0008] To achieve the aforementioned objective, this invention provides a methanol-diesel dual-nozzle dual-direct-injection engine. The engine is a compression-ignition engine, comprising a low-pressure fuel pump, a diesel filter assembly, a high-pressure fuel pump, a high-pressure diesel common rail, a low-pressure methanol pump, a methanol filter assembly, a high-pressure methanol pump, a high-pressure methanol common rail, and at least one cylinder. Each cylinder is equipped with a diesel injector and a methanol injector. The methanol injector is coaxially arranged with the cylinder, and the diesel injector extends obliquely towards the axis of the cylinder. The axis of the diesel injector is parallel to the axis of the cylinder. The axes are in the same plane, and the angle between the axis of the diesel injector and the axis of the cylinder is 20-40°. The low-pressure oil pump is connected in sequence to the diesel filter assembly, the high-pressure oil pump, the high-pressure diesel common rail, and the diesel injector through oil pipes. The low-pressure alcohol pump is connected in sequence to the methanol filter assembly, the high-pressure methanol pump, the high-pressure methanol common rail, and the methanol injector through alcohol pipes. The nozzles of the diesel injector and the methanol injector are arranged at intervals. Part of the diesel fuel jet sprayed by the diesel injector interferes with the methanol fuel jet sprayed by the methanol injector.
[0009] As a further improvement, the nozzles of the methanol injector are arranged in an axisymmetric manner.
[0010] Furthermore, if the angle between the axis of the diesel injector and the axis of the cylinder is 20-30°, then the nozzle of the diesel injector is arranged axially symmetrically; otherwise, the nozzle of the diesel injector is arranged non-axially symmetrically.
[0011] Furthermore, the diesel filter assembly includes a diesel coarse filter and a diesel fine filter.
[0012] Furthermore, the methanol filtration assembly includes a methanol coarse filter and a methanol fine filter.
[0013] To achieve the second objective mentioned above, this invention provides a control method for a methanol-diesel dual-nozzle dual-direct-injection engine. When the engine is operating under medium to high load, both diesel and methanol are injected in a single injection. The diesel injector injects a small amount of diesel into the cylinder 6-10°CA before the piston approaches top dead center, forming a micro-ignition source. Subsequently, the methanol injector injects methanol into the cylinder 1-4°CA after the diesel injection ends, forming a combustible mixture. The proportion of diesel injection is less than 10% of the total fuel calorific value.
[0014] As a further improvement, when the engine is running at low load, methanol is injected twice and diesel is injected once. The timing of the first methanol injection is within 25°CA before top dead center, and the amount of methanol injected in the first injection accounts for 80-90% of the total calorific value of methanol fuel. The timing of the diesel injection is 6-9°CA before top dead center, and the proportion of diesel injection accounts for 10%-15% of the total calorific value of fuel. The timing of the second methanol injection is 1-3°CA after the diesel injection ends.
[0015] Furthermore, when the engine starts or methanol injection malfunctions, only diesel injection is performed to achieve pure diesel combustion mode.
[0016] Beneficial effects
[0017] Compared with the prior art, the advantages of this invention are as follows:
[0018] 1. In this invention, both methanol and diesel are directly injected into the cylinder before top dead center. High-pressure methanol injection can achieve better atomization and mixing of methanol, enabling the engine to maintain the same power target as a diesel engine, while achieving higher thermal efficiency and lower emissions than a diesel engine.
[0019] 2. The present invention uses a dual direct injection system, which can make methanol combustion more complete. Compared with other methanol engines, it can greatly reduce the emission of formaldehyde and unburned methanol.
[0020] 3. This invention takes into account the load and whether the methanol system fails, and sets different fuel injection schemes to achieve stable operation of the engine under all operating conditions.
[0021] 4. This invention can adjust the ratio of methanol and diesel and the injection timing of methanol and diesel in a timely manner according to load and speed requirements, so as to achieve stable operation of the engine under all operating conditions and efficient and clean combustion. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the engine structure in this invention;
[0023] Figure 2 This is a schematic diagram of methanol and diesel mist when the diesel injector is tilted at a large angle in this invention;
[0024] Figure 3 This is a schematic diagram of methanol and diesel mist when the diesel injector tilt angle is small in this invention;
[0025] Figure 4 This is a flow rate diagram of methanol and diesel fuel when the engine is operating at medium to high load in this invention;
[0026] Figure 5 This is a flow rate diagram of methanol and diesel fuel injection when the engine is operating at low load in this invention.
[0027] The components are: 1-Cylinder liner, 2-Piston, 3-Methanol fuel tank, 4-Low-pressure methanol pump, 5-Methanol coarse filter, 6-Methanol fine filter, 7-High-pressure methanol pump, 8-Exhaust valve, 9-Cylinder head, 10-Methanol injector, 11-Diesel injector, 12-Intake valve, 13-High-pressure methanol common rail, 14-ECU, 15-High-pressure diesel common rail, 16-High-pressure fuel pump, 17-Diesel fine filter, 18-Diesel coarse filter, 19-Low-pressure fuel pump, 20-Diesel fuel tank, 21-Cylinder, 22-Diesel filter assembly, 23-Methanol filter assembly, 24-Fuel pipe, 25-Methanol pipe, 26-Diesel fuel jet, 27-Methanol fuel jet, 28-Methanol fuel tank. Detailed Implementation
[0028] The present invention will be further described below with reference to specific embodiments shown in the accompanying drawings.
[0029] See Figures 1-5 A methanol-diesel dual-nozzle dual-direct-injection engine is disclosed. The engine is a compression-ignition engine, comprising a low-pressure fuel pump 19, a diesel filter assembly 22, a high-pressure fuel pump 16, a high-pressure diesel common rail 15, a low-pressure methanol pump 4, a methanol filter assembly 23, a high-pressure methanol pump 7, a high-pressure methanol common rail 13, and at least one cylinder 21. Each cylinder 21 is equipped with a diesel injector 11 and a methanol injector 10. Specifically, each cylinder 21 has a cylinder liner 1, a piston 2 installed within the cylinder liner 1, and a cylinder head 9 mounted on top of the cylinder 21. The sealed space enclosed by the cylinder liner 1, piston 2, and cylinder head 9 constitutes the combustion chamber of the cylinder 21. The cylinder 21 is connected to the intake manifold via an intake valve 12 and to the exhaust manifold via an exhaust valve 8. The intake valve 12 receives fresh air, while the exhaust valve 8 discharges exhaust gases from the combustion chamber. Low-pressure oil pump 19 is connected in sequence to diesel filter assembly 22, high-pressure oil pump 16, high-pressure diesel common rail 15, and diesel injector 11 via oil pipe 24. Low-pressure oil pump 19 is connected to diesel fuel tank 20 via oil pipe 24. Diesel fuel passes sequentially through diesel fuel tank 20, low-pressure oil pump 19, diesel filter assembly 22, and high-pressure oil pump 16 to reach high-pressure diesel common rail 15 and is supplied to diesel injector 11. Low-pressure alcohol pump 4 is connected in sequence to methanol filter assembly 23, high-pressure methanol pump 7, high-pressure methanol common rail 13, and methanol injector 10 via alcohol pipe 25. Low-pressure alcohol pump 4 is connected to methanol fuel tank 28 via alcohol pipe 25. Methanol passes sequentially through methanol fuel tank 3, low-pressure alcohol pump 4, methanol filter assembly 23, and high-pressure methanol pump 7 to reach high-pressure methanol common rail 13 and is supplied to methanol injector 10. ECU14 controls the operation of high-pressure oil pump 16 and high-pressure methanol pump 7 according to the engine operating conditions, so as to control and regulate the pressure of high-pressure diesel common rail 15 and high-pressure methanol common rail 13, and control the injection of in-cylinder methanol injector 10 and diesel injector 11.
[0030] Both the methanol injector 10 and the diesel injector 11 are orifice-type high-pressure common rail injectors. They can achieve single or multiple injections within a single cycle, and the number of injections, injection timing, and injection pulse width can be adjusted according to actual needs.
[0031] The methanol injector 10 is coaxially arranged with the cylinder 21, meaning the axis of the methanol injector 10 coincides with the axis of the cylinder 21. The diesel injector 11 extends obliquely towards the axis of the cylinder 21, with its axis in the same plane as the axis of the cylinder 21, and the angle between their axes being 20-40°. The nozzles of the diesel injector 11 and the methanol injector 10 are spaced apart, meaning there is a certain distance between their heads and both are exposed in the combustion chamber of the cylinder 21. In actual operation, a portion of the diesel fuel jet 26 ejected by the diesel injector 11 interferes with the methanol jet 27 ejected by the methanol injector 10.
[0032] The methanol injector 10 has an axisymmetric arrangement of nozzles, which ensures that the high-pressure methanol is evenly distributed within the cylinder liner 1 after injection. The direct injection diesel injector 11 has its nozzle design based on the tilt angle. When the tilt angle is large, a non-axisymmetric design is used; when the tilt angle is small, an axisymmetric design is used.
[0033] Preferably, if the angle between the axis of the diesel injector 11 and the axis of the cylinder 21 is 20-30°, then the nozzle of the diesel injector 11 is arranged axially symmetrically; otherwise, the nozzle of the diesel injector 11 is arranged non-axially symmetrically.
[0034] The diesel filter assembly 22 includes a diesel coarse filter 18 and a diesel fine filter 17, and the methanol filter assembly 23 includes a methanol coarse filter 5 and a methanol fine filter 6. The two-stage filtration effectively removes impurities from diesel and methanol, ensuring the working stability of the diesel injection system and the methanol injection system. The diesel injection system includes the aforementioned low-pressure oil pump 19, diesel filter assembly 22, high-pressure oil pump 16, high-pressure diesel common rail 15, and diesel injector 11. The methanol injection system includes the aforementioned low-pressure methanol pump 4, methanol filter assembly 23, high-pressure methanol pump 7, high-pressure methanol common rail 13, and methanol injector 10.
[0035] A control method for a methanol-diesel dual-nozzle dual-direct-injection engine includes a diesel micro-ignition methanol diffusion combustion mode under medium-to-high load, a premixed combustion + partial diffusion combustion mode under low load, and a pure diesel combustion mode. To avoid methanol spray hitting the inner wall of cylinder 21, the injection timing of high-pressure methanol should not be too early; all methanol injection timings are within 25°CA before top dead center. High-pressure methanol injection is used in all dual-fuel modes (i.e., the diesel micro-ignition methanol diffusion combustion mode under medium-to-high load and the premixed combustion + partial diffusion combustion mode under low load) to ensure better methanol atomization and vaporization, and to ensure injection is completed within the required pulse width. In dual-fuel mode, the diesel injector 11 mainly serves as an ignition point, with an injection ratio not exceeding 15%, and all injections are single-shot, with an injection timing of 1-9°CA before top dead center. The pure diesel mode is mainly used for engine starting and in cases of methanol injection system malfunction, allowing for on-demand switching between methanol-diesel dual-fuel mode and pure diesel mode.
[0036] like Figure 4 As shown, the diesel micro-ignition methanol diffusion combustion mode under medium-to-high load is as follows: When the engine is running under medium-to-high load, both diesel and methanol are injected in a single injection. The diesel injector 11 injects a small amount of diesel into the cylinder 21 6-10°CA before the piston 2 approaches top dead center, forming a micro-ignition source. The proportion of diesel injection is less than 10% of the total fuel calorific value. Subsequently, the methanol injector 10 injects methanol into the combustion chamber of the cylinder 21 1-4°CA after the diesel injection ends, which mixes with the high-temperature and high-pressure air to form a combustible mixture. When the mixture encounters the micro-ignition source formed by diesel, it ignites spontaneously and expands rapidly, pushing the piston 2 downward to do work. The entire combustion process is diesel micro-ignition methanol diffusion combustion.
[0037] like Figure 5As shown, the low-load premixed combustion + partial diffusion combustion mode specifically involves: when the engine is running at low load, methanol is injected twice, and diesel is injected once; the timing of the first methanol injection is within 25°CA before top dead center to avoid collision caused by premature high-pressure methanol injection, and the amount of methanol injected in the first injection accounts for 80-90% of the total methanol fuel calorific value; the timing of diesel injection is 6-9°CA before top dead center, and the proportion of diesel injection accounts for 10%-15% of the total fuel calorific value to improve combustion stability under low load; as most of the methanol is injected in the first injection... The methanol is injected into the cylinder and quickly forms a premixed mixture with the surrounding air. Then, diesel fuel is injected, which rapidly atomizes, evaporates, and ignites. The high-temperature zone formed by combustion ignites the methanol premixed mixture formed in the previous step. To control the combustion reaction rate, the methanol is injected a second time 1-3°CA after the diesel fuel injection ends, injecting the remaining methanol into the cylinder and burning it. This can reduce the reaction temperature to a certain extent, control the reaction rate, and suppress knocking. The combustion mode at low loads is mostly premixed combustion plus a small amount of diffusion combustion, which can maximize the engine's thermal efficiency while avoiding knocking and excessive pressure rise.
[0038] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.
Claims
1. A methanol-diesel dual-nozzle dual-direct-injection engine, characterized in that, The engine is a compression ignition engine, including a low-pressure oil pump (19), a diesel filter assembly (22), a high-pressure oil pump (16), a high-pressure diesel common rail (15), a low-pressure methanol pump (4), a methanol filter assembly (23), a high-pressure methanol pump (7), a high-pressure methanol common rail (13), and at least one cylinder (21). Each cylinder (21) is equipped with a diesel injector (11) and a methanol injector (10). The methanol injector (10) is coaxially arranged with the cylinder (21). The diesel injector (11) extends obliquely towards the axis of the cylinder (21), and the axis of the diesel injector (11) is in the same plane as the axis of the cylinder (21). The angle between the axis of 1) and the axis of the cylinder (21) is 20-40°. The low-pressure oil pump (19) is connected in sequence to the diesel filter assembly (22), the high-pressure oil pump (16), the high-pressure diesel common rail (15), and the diesel injector (11) through the oil pipe (24). The low-pressure alcohol pump (4) is connected in sequence to the methanol filter assembly (23), the high-pressure methanol pump (7), the high-pressure methanol common rail (13), and the methanol injector (10) through the alcohol pipe (25). The nozzles of the diesel injector (11) and the nozzles of the methanol injector (10) are arranged at intervals. Part of the diesel oil jet (26) sprayed by the diesel injector (11) interferes with the methanol alcohol jet (27) sprayed by the methanol injector (10). If the angle between the axis of the diesel injector (11) and the axis of the cylinder (21) is 20-30°, then the nozzle of the diesel injector (11) is arranged axially symmetrically; otherwise, the nozzle of the diesel injector (11) is arranged non-axially symmetrically.
2. The methanol-diesel dual-nozzle dual-direct-injection engine according to claim 1, characterized in that, The nozzles of the methanol injector (10) are arranged in an axisymmetric manner.
3. A methanol-diesel dual-nozzle dual-direct-injection engine according to claim 1, characterized in that, The diesel filter assembly (22) includes a diesel coarse filter (18) and a diesel fine filter (17).
4. A methanol-diesel dual-nozzle dual-direct-injection engine according to claim 1, characterized in that, The methanol filtration assembly (23) includes a methanol coarse filter (5) and a methanol fine filter (6).
5. A control method applied to the methanol-diesel dual-nozzle dual-direct-injection engine according to any one of claims 1-4, characterized in that, When the engine is running at medium to high load, both diesel and methanol are injected in a single injection. The diesel injector (11) injects a small amount of diesel into the cylinder (21) 6-10°CA before the piston (2) of the cylinder (21) approaches the top dead center, forming a micro-ignition source. Subsequently, the methanol injector (10) injects methanol into the cylinder (21) 1-4°CA after the diesel injection ends, forming a combustible mixture. The proportion of diesel injection is less than 10% of the total fuel calorific value.
6. The control method for a methanol-diesel dual-nozzle dual-direct-injection engine according to claim 5, characterized in that, When the engine is running at low load, methanol is injected twice, while diesel is injected once. The timing of the first methanol injection is within 25°CA before top dead center, and the amount of methanol injected in the first injection accounts for 80-90% of the total calorific value of methanol fuel. The timing of the diesel injection is 6-9°CA before top dead center, and the proportion of diesel injection accounts for 10%-15% of the total calorific value of fuel. The timing of the second methanol injection is 1-3°CA after the diesel injection ends.
7. The control method for a methanol-diesel dual-nozzle dual-direct-injection engine according to claim 6, characterized in that, When the engine starts or methanol injection malfunctions, only diesel injection is performed to achieve pure diesel combustion mode.