A high compression ratio ethanol fuel gasoline engine combustion system and a control method thereof

Abstract

The application provides a high-compression-ratio ethanol fuel gasoline engine combustion system and a control method thereof, wherein the system comprises: a high-compression-ratio combustion structure with a compression ratio of 14-15, the combustion structure comprises a piston top with an omega-shaped shallow pit structure, and the surface of the piston top is provided with a silicon nitride ceramic coating; a cold start enhancement system comprising a PTC ceramic heating module and a high-energy ignition device; a fuel injection system comprising a high-pressure common rail system and a multi-hole swirl oil injector; and a control system comprising an ECU control unit and a UEGO wide-range oxygen sensor. The high-compression-ratio ethanol fuel gasoline engine combustion system and the control method thereof can realize high thermal efficiency, reliable start at low temperature, stable combustion and low emission.

Description

Technical Field

[0001] This invention relates to the field of gasoline engine technology, and more specifically, to a combustion system and control method for a high compression ratio ethanol fuel gasoline engine. Background Technology

[0002] Ethanol fuel has a high octane rating and is clean and environmentally friendly, making it a preferred alternative fuel for gasoline engines. However, directly converting a traditional gasoline engine into an ethanol engine has many drawbacks:

[0003] 1. Poor compression ratio adaptability: Traditional gasoline engines have a compression ratio of only 8 to 10, which cannot fully utilize the high anti-knock properties of ethanol, resulting in a thermal efficiency loss of 15% to 20%.

[0004] 2. Difficulty in cold start: The latent heat of vaporization of ethanol is as high as 840 kJ / kg, which causes a sudden drop in the intake temperature, resulting in an excessively lean mixture and a 30% increase in the low-temperature misfire rate.

[0005] 3. Poor combustion stability: The laminar flame velocity of ethanol (0.37 m / s) is 40% lower than that of gasoline, which can easily cause knocking or partial combustion;

[0006] 4. Difficulty in emission control: Existing technologies have an efficiency of less than 50% in converting unconventional pollutants such as acetaldehyde.

[0007] Current modifications to ethanol engines only increase the fuel injection flow rate, retain the original compression ratio and combustion chamber structure, and compensate for cold starts by extending the injection pulse width and delaying the ignition angle. The effects are limited, and the thermal efficiency, cold start performance, combustion stability, and emission control cannot meet the requirements for efficient pure ethanol combustion. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a high compression ratio ethanol fuel gasoline engine combustion system and its control method to achieve high thermal efficiency, reliable low-temperature start-up, stable combustion, and low emissions.

[0009] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0010] According to a first aspect of the present invention, a high compression ratio ethanol fuel gasoline engine combustion system is provided, comprising:

[0011] A high compression ratio combustion structure with a compression ratio of 14 to 15 is provided. The combustion structure includes a piston top with a shallow ω-shaped recess structure, the recess depth being 3 to 5 mm and the radius of curvature being 15 to 20 mm. The piston top surface is provided with a silicon nitride ceramic coating with a coating thickness of 0.3 to 0.5 mm.

[0012] The cold start enhancement system includes a PTC ceramic heating module and a high-energy ignition device. The PTC ceramic heating module is used to heat the intake air temperature to 40-70°C, and the high-energy ignition device has an ignition energy of ≥120mJ and a secondary voltage of ≥40kV.

[0013] A fuel injection system, comprising a high-pressure common rail system and a multi-hole swirl injector, wherein the high-pressure common rail system has an injection pressure of 20 MPa, and the multi-hole swirl injector has 6 injection holes with a diameter of 0.18–0.22 mm.

[0014] The control system includes an ECU control unit and a UEGO wide-range oxygen sensor, wherein the response time of the UEGO wide-range oxygen sensor is ≤20ms;

[0015] The control system is used to dynamically adjust the fuel injection quantity based on engine speed and load, so that the air-fuel ratio is controlled within the range of λ=1.0±0.02.

[0016] Furthermore, the power density of the PTC ceramic heating module is 1.2W / cm², and the temperature control accuracy is ±2℃.

[0017] Furthermore, the injector adopts a swirling structure and has a tungsten carbide coating on the surface of the nozzle.

[0018] Furthermore, the fuel atomized particle size generated by the fuel injection system is ≤25μm.

[0019] Furthermore, the control system adopts a dual closed-loop control structure, including air-fuel ratio closed-loop control and fuel injection quantity closed-loop control.

[0020] According to a second aspect of the present invention, a control method for a high compression ratio ethanol fuel gasoline engine combustion system is provided, characterized in that the method is used to control the high compression ratio ethanol fuel gasoline engine combustion system as described above, the method comprising:

[0021] S1. During the engine cold start phase, the intake air is preheated by the PTC heating module to bring the intake air temperature to 40-70℃.

[0022] S2. Control the high-energy ignition device to output ≥120mJ of ignition energy;

[0023] S3. During engine operation, fuel is injected at a pressure of 20MPa through the high-pressure common rail system;

[0024] S4. Adjust the fuel injection ratio according to the engine speed N and load P, where the calculation formula is:

[0025] α=0.7+0.2×(N / 4000)+0.1×(P / 100);

[0026] S5. The air-fuel ratio is detected in real time by the UEGO sensor and closed-loop correction is performed to keep the air-fuel ratio at λ=1.0±0.02.

[0027] Furthermore, when the ambient temperature is ≤-20℃, the ignition energy is increased to 150mJ.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention provides a high compression ratio ethanol fuel gasoline engine combustion system and its control method, which adopts a high compression ratio of 14 to 15, makes full use of the high octane number of ethanol, breaks through the limitation of the compression ratio of traditional gasoline engines, greatly improves thermal efficiency, and at the same time adopts shallow pit piston and silicon nitride coating to optimize combustion chamber turbulence, improve flame propagation speed, enhance heat dissipation capacity, and reduce the risk of knocking.

[0030] 2. The present invention provides a high compression ratio ethanol fuel gasoline engine combustion system and its control method, which greatly improves cold start performance. The PTC preheating system can heat the intake air within 30 seconds to offset the temperature drop caused by the high latent heat of vaporization of ethanol, and ensure reliable start-up at low temperatures.

[0031] 3. The present invention provides a high compression ratio ethanol fuel gasoline engine combustion system and its control method, which enhances combustion stability, adopts a 20MPa high-pressure direct injection system, atomized particle size ≤25μm, optimizes the uniformity of air-fuel mixture, reduces the risk of misfire and knock, and at the same time adjusts the injection quantity in real time based on speed and load to ensure precise control of air-fuel ratio.

[0032] 4. The present invention provides a high compression ratio ethanol fuel gasoline engine combustion system and its control method, which adopts a UEGO wide-range oxygen sensor. Compared with the traditional zirconium oxide sensor, the air-fuel ratio adjustment speed is increased by 2.5 times, reducing emission fluctuations and facilitating the control of emissions such as formaldehyde. Attached Figure Description

[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1 This is a flowchart of the control method for the combustion system of a high compression ratio ethanol fuel gasoline engine in Example 2. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application 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. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0037] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, all directional indications (such as up, down, left, right, front, back, bottom, etc.) in this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indication will also change accordingly. Furthermore, descriptions involving "first," "second," etc., in this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0038] Example 1

[0039] This embodiment provides a high compression ratio ethanol fuel gasoline engine combustion system, including:

[0040] The high compression ratio combustion structure has a compression ratio of 14 to 15. The combustion structure includes a piston crown with a shallow ω-shaped recess structure, the recess depth is 3 to 5 mm, and the radius of curvature is 15 to 20 mm. The piston crown surface is coated with a silicon nitride ceramic coating with a coating thickness of 0.3 to 0.5 mm.

[0041] The cold start enhancement system includes a PTC ceramic heating module and a high-energy ignition device. The PTC ceramic heating module heats the intake air temperature to 40–70°C, and the high-energy ignition device has an ignition energy ≥120mJ and a secondary voltage ≥40kV. In this embodiment, the power density of the PTC ceramic heating module is 1.2W / cm², and the temperature control accuracy is ±2°C.

[0042] The fuel injection system includes a high-pressure common rail system and a multi-orifice swirl injector. The high-pressure common rail system has an injection pressure of 20 MPa, and the multi-orifice swirl injector has 6 nozzles with a diameter of 0.18–0.22 mm. Furthermore, the injector employs a swirl structure and has a tungsten carbide coating on the nozzle surface. The fuel atomized particle size produced by the fuel injection system is ≤25 μm.

[0043] The control system includes an ECU control unit and a UEGO wide-range oxygen sensor, with a response time of ≤20ms. The control system adopts a dual closed-loop control structure, including air-fuel ratio closed-loop control and fuel injection quantity closed-loop control.

[0044] The control system is used to dynamically adjust the fuel injection quantity based on engine speed and load, so that the air-fuel ratio is controlled within the range of λ=1.0±0.02.

[0045] This invention provides a high compression ratio ethanol fuel gasoline engine combustion system and its control method. First, it employs a high compression ratio of 14-15, fully utilizing the high octane number of ethanol to overcome the limitations of traditional gasoline engine compression ratios, significantly improving thermal efficiency. Simultaneously, it utilizes a shallow-dimpled piston and a silicon nitride coating to optimize combustion chamber turbulence, increase flame propagation speed, enhance heat dissipation, and reduce the risk of knocking. Second, it significantly improves cold-start performance. The PTC preheating system can heat the intake air within 30 seconds, offsetting the temperature drop caused by the high latent heat of vaporization of ethanol, ensuring reliable low-temperature starting. Third, it enhances combustion stability. A 20MPa high-pressure direct injection system with an atomized particle size ≤25μm optimizes mixture uniformity, reducing the risk of misfire and knocking. Simultaneously, it adjusts the injection quantity in real time based on engine speed and load to ensure precise air-fuel ratio control. Finally, it employs a UEGO wide-range oxygen sensor, which, compared to traditional zirconium oxide sensors, increases the air-fuel ratio adjustment speed by 2.5 times, reducing emission fluctuations and facilitating the control of emissions such as formaldehyde.

[0046] Example 2

[0047] like Figure 1 The diagram illustrates a control method for a high-compression-ratio ethanol fuel gasoline engine combustion system provided in this embodiment. This method controls the high-compression-ratio ethanol fuel gasoline engine combustion system as described in Embodiment 1, and includes:

[0048] S1. During the engine cold start phase, the intake air is preheated by the PTC heating module to bring the intake air temperature to 40-70℃.

[0049] S2. Control the high-energy ignition device to output ≥120mJ of ignition energy. Further, when the ambient temperature is ≤-20℃, control the ignition energy to be increased to 150mJ.

[0050] S3. During engine operation, fuel is injected at a pressure of 20MPa through the high-pressure common rail system.

[0051] S4. Adjust the fuel injection ratio according to the engine speed N and load P, where the calculation formula is:

[0052] α=0.7+0.2×(N / 4000)+0.1×(P / 100).

[0053] S5. The air-fuel ratio is detected in real time by the UEGO sensor and closed-loop correction is performed to keep the air-fuel ratio at λ=1.0±0.02.

[0054] The specific embodiments of the present invention have been described above. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A combustion system for a high compression ratio ethanol fuel gasoline engine, characterized in that, include: A high compression ratio combustion structure with a compression ratio of 14 to 15 is provided. The combustion structure includes a piston top with a shallow ω-shaped recess structure, the recess depth being 3 to 5 mm and the radius of curvature being 15 to 20 mm. The piston top surface is provided with a silicon nitride ceramic coating with a coating thickness of 0.3 to 0.5 mm. The cold start enhancement system includes a PTC ceramic heating module and a high-energy ignition device. The PTC ceramic heating module is used to heat the intake air temperature to 40-70°C, and the high-energy ignition device has an ignition energy of ≥120mJ and a secondary voltage of ≥40kV. A fuel injection system, comprising a high-pressure common rail system and a multi-hole swirl injector, wherein the high-pressure common rail system has an injection pressure of 20 MPa, and the multi-hole swirl injector has 6 injection holes with a diameter of 0.18–0.22 mm. The control system includes an ECU control unit and a UEGO wide-range oxygen sensor, wherein the response time of the UEGO wide-range oxygen sensor is ≤20ms; The control system is used to dynamically adjust the fuel injection quantity based on engine speed and load, so that the air-fuel ratio is controlled within the range of λ=1.0±0.

02.

2. The high compression ratio ethanol fuel gasoline engine combustion system according to claim 1, characterized in that, The PTC ceramic heating module has a power density of 1.2 W / cm² and a temperature control accuracy of ±2℃.

3. The high compression ratio ethanol fuel gasoline engine combustion system according to claim 1, characterized in that, The injector adopts a swirling structure and has a tungsten carbide coating on the surface of the nozzle.

4. The high compression ratio ethanol fuel gasoline engine combustion system according to claim 1, characterized in that, The fuel atomization particle size generated by the fuel injection system is ≤25μm.

5. The high compression ratio ethanol fuel gasoline engine combustion system according to claim 1, characterized in that, The control system adopts a dual closed-loop control structure, including air-fuel ratio closed-loop control and fuel injection quantity closed-loop control.

6. A control method for a combustion system of a high compression ratio ethanol fuel gasoline engine, characterized in that, The method for controlling the combustion system of a high compression ratio ethanol fuel gasoline engine as described in any one of claims 1 to 5, the method comprising: S1. During the engine cold start phase, the intake air is preheated by the PTC heating module to bring the intake air temperature to 40-70℃. S2. Control the high-energy ignition device to output ≥120mJ of ignition energy; S3. During engine operation, fuel is injected at a pressure of 20MPa through the high-pressure common rail system; S4. Adjust the fuel injection ratio according to the engine speed N and load P, where the calculation formula is: α=0.7+0.2×(N / 4000)+0.1×(P / 100); S5. The air-fuel ratio is detected in real time by the UEGO sensor and closed-loop correction is performed to keep the air-fuel ratio at λ=1.0±0.

02.

7. The control method for the combustion system of a high compression ratio ethanol fuel gasoline engine according to claim 6, characterized in that, When the ambient temperature is ≤-20℃, the ignition energy is increased to 150mJ.

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