Method, device and equipment for controlling formaldehyde emission through methanol engine and storage medium

Abstract

The invention provides a method, device and equipment for controlling formaldehyde emission of a methanol engine and a storage medium. The method is applied to a control system comprising an air inlet pipe pressure and temperature sensor, a fuel pipeline metering valve and the like. According to the method, parameters such as the rotating speed and the load are obtained, a normalized value and a target air-fuel ratio are calculated, and the actual air-fuel ratio and deviation are obtained in combination with air inlet data. Therefore, injection timing and a pressure correction coefficient are determined, and the opening degree of a throttle valve and the injection timing and pressure of the methanol injector are adjusted. The air-fuel ratio and injection parameters of the methanol engine are accurately regulated and controlled, formaldehyde emission is effectively reduced by 26%, the environmental protection performance is improved, and low-carbon transformation of commercial vehicles is assisted.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of methanol engines, and particularly relates to a method, device, equipment and storage medium for controlling formaldehyde emission of a methanol engine. BACKGROUND

[0002] Methanol, as a clean and efficient alternative fuel, has several significant advantages. First, methanol has a high energy density and strong hydrogen-carrying capacity. The hydrogen-carrying capacity of 1 liter of methanol is twice that of 1 liter of liquid hydrogen, which makes long-distance transportation possible. Second, methanol combustion is efficient and clean. Since methanol contains oxygen, the amount of CO2 generated during combustion is less, and almost no soot is produced, which helps to reduce greenhouse gas emissions and air pollution. Third, methanol is easy to store, transport and fill, and can use existing diesel and gasoline infrastructure, reducing the cost of supporting facilities. In addition, methanol, as a renewable energy source, can be produced through electricity and biomass routes. It is estimated that global methanol production capacity will reach 8 million tons by 2027, showing good prospects for sustainable development. Finally, from an economic point of view, the unit price of methanol is only one-third of that of diesel, and the use of methanol engines can significantly reduce operating costs, saving about 1 yuan per kilometer of travel.

[0003] However, methanol engines also face a challenge during the combustion process, which is that the carbon-hydrogen bond in the methanol molecule is easily broken or incompletely oxidized to generate formaldehyde. Formaldehyde is not only a strong irritant pollutant, but also a potential carcinogen, posing a serious threat to human health and the environment. With increasingly stringent environmental regulations, how to effectively reduce the formaldehyde emission of methanol engines has become a key problem that must be solved for their large-scale application. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned prior art, and to provide a method, device, equipment and storage medium for controlling formaldehyde emission of a methanol engine.

[0005] The method for controlling formaldehyde emission of a methanol engine provided by the present application is applied to a methanol engine control system, which includes an intake pipe pressure and temperature sensor, a fuel pipe metering valve, an engine controller, a throttle valve and a methanol injector. The method includes the following steps:

[0006] Obtaining engine speed and engine load from the engine controller, obtaining intake pressure and intake temperature from the intake pipe pressure and temperature sensor, and obtaining methanol injection flow from the fuel pipe metering valve;

[0007] According to the engine speed and engine load, a normalized speed and a normalized torque are calculated, and a target air-fuel ratio is calculated according to the normalized speed, the normalized torque and a plurality of preset correction coefficients;

[0008] calculating an intake flow rate according to the intake pressure and the intake temperature;

[0009] calculating an actual air-fuel ratio according to the intake flow rate and the methanol injection flow rate;

[0010] calculating an air-fuel ratio deviation according to the actual air-fuel ratio and the target air-fuel ratio;

[0011] determining an injection timing correction coefficient and an injection pressure correction coefficient according to the engine speed and the air-fuel ratio deviation;

[0012] adjusting an opening degree of the throttle valve according to the air-fuel ratio deviation, and adjusting an injection timing and an injection pressure of the methanol injector according to the injection timing correction coefficient and the injection pressure correction coefficient.

[0013] Optionally, the calculating the intake flow rate according to the intake pressure and the intake temperature comprises:

[0014] obtaining a cross-sectional area of an exhaust pipe, an exhaust pressure and an exhaust temperature;

[0015] calculating the intake flow rate according to the intake pressure, the intake temperature, the cross-sectional area of the exhaust pipe, the exhaust pressure and the exhaust temperature.

[0016] Optionally, the calculating the target air-fuel ratio according to the normalized speed, the normalized torque and a plurality of preset correction coefficients comprises:

[0017] calculating the target air-fuel ratio using a product term of the normalized speed and the normalized torque and a product term correction coefficient.

[0018] Optionally, the determining the injection timing correction coefficient according to the engine speed and the air-fuel ratio deviation comprises:

[0019] calculating the injection timing correction coefficient according to a quadratic polynomial function of the normalized speed.

[0020] Optionally, the calculating the injection timing correction coefficient according to the quadratic polynomial function of the normalized speed comprises:

[0021] calculating the injection timing correction coefficient according to a linear function of the normalized torque.

[0022] Optionally, the calculating the injection timing correction coefficient according to the linear function of the normalized torque comprises:

[0023] calculating the injection timing correction coefficient according to a product term of the normalized speed and the normalized torque and an interaction term correction coefficient.

[0024] Optionally, the adjusting the injection pressure comprises:

[0025] adjusting the injection pressure conditionally according to the engine speed and the air-fuel ratio deviation;

[0026] wherein the injection pressure is increased when the engine speed is greater than a preset speed threshold and the air-fuel ratio deviation is greater than a first deviation threshold;

[0027] wherein the injection pressure is decreased when the engine speed is less than the preset speed threshold and the air-fuel ratio deviation is less than a second deviation threshold.

[0028] The application also provides a device for controlling formaldehyde emission of a methanol engine, which is applied to a methanol engine control system, and the methanol engine control system comprises an intake pipe pressure temperature sensor, a fuel pipe metering valve, an engine controller, a throttle valve and a methanol injector.

[0029] The acquisition module acquires the engine speed and engine load from the engine controller, acquires the intake pressure and intake temperature from the intake pipe pressure temperature sensor, and acquires the methanol injection flow from the fuel pipe metering valve; calculates the normalized speed and normalized torque according to the engine speed and engine load; and calculates the target air-fuel ratio according to the normalized speed, the normalized torque and a plurality of preset correction coefficients.

[0030] The calculation module calculates the intake flow according to the intake pressure and intake temperature, calculates the actual air-fuel ratio according to the intake flow and methanol injection flow, and calculates the air-fuel ratio deviation according to the actual air-fuel ratio and the target air-fuel ratio.

[0031] The coefficient module determines the injection timing correction coefficient and the injection pressure correction coefficient according to the engine speed and the air-fuel ratio deviation.

[0032] The adjustment module adjusts the opening degree of the throttle valve according to the air-fuel ratio deviation, and adjusts the injection timing and injection pressure of the methanol injector according to the injection timing correction coefficient and the injection pressure correction coefficient.

[0033] The application also provides an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to control the execution of the above method.

[0034] The application also provides a computer readable storage medium, which stores a computer program, and when the computer program is executed in a computer, the computer controls the execution of the above method.

[0035] The application has the following beneficial effects:

[0036] The application provides a method for controlling formaldehyde emission of a methanol engine, which is applied to a methanol engine control system, and the methanol engine control system comprises an intake pipe pressure and temperature sensor, a fuel pipe metering valve, an engine controller, a throttle valve and a methanol injector, and the method comprises the following steps: obtaining engine speed and engine load from the engine controller, obtaining intake pressure and intake temperature from the intake pipe pressure and temperature sensor, and obtaining methanol injection flow from the fuel pipe metering valve; calculating normalized speed and normalized torque according to the engine speed and the engine load; calculating target air-fuel ratio according to the normalized speed, the normalized torque and a plurality of preset correction coefficients; calculating intake flow according to the intake pressure and the intake temperature; calculating actual air-fuel ratio according to the intake flow and the methanol injection flow; calculating air-fuel ratio deviation according to the actual air-fuel ratio and the target air-fuel ratio; determining injection timing correction coefficient and injection pressure correction coefficient according to the engine speed and the air-fuel ratio deviation; adjusting the opening degree of the throttle valve according to the air-fuel ratio deviation; and adjusting the injection timing and the injection pressure of the methanol injector according to the injection timing correction coefficient and the injection pressure correction coefficient. The application can effectively reduce the formaldehyde emission by 26% by accurately controlling the air-fuel ratio of the methanol engine and the methanol injection timing and pressure, significantly improves the environmental protection performance of the engine, and helps the commercial vehicle industry to realize low-carbon and green transformation. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a methanol engine control flow diagram in the application;

[0038] Figure 2 is a methanol injection timing transient correction coefficient diagram in the application;

[0039] Figure 3 is a formaldehyde emission reduction diagram in the application. DETAILED DESCRIPTION

[0040] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, the embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0041] Please Figure 1 As shown in the drawings, the application provides a method for controlling formaldehyde emission of a methanol engine, which is applied to the field of methanol engine control and used for reducing formaldehyde emission of a methanol engine, and the method comprises the following steps:

[0042] S101, obtaining engine speed and engine load from the engine controller, obtaining intake pressure and intake temperature from the intake pipe pressure temperature sensor, and obtaining methanol injection flow from the fuel pipe metering valve;

[0043] Engine speed and engine load are monitored in real time by the engine controller; intake pressure and intake temperature are measured in real time by the pressure temperature sensor installed in the intake pipe of the methanol engine; methanol injection flow is measured in real time by the metering valve installed in the fuel pipe.

[0044] S102, calculating normalized speed and normalized torque according to the engine speed and engine load, and calculating target air-fuel ratio according to the normalized speed, the normalized torque and a plurality of preset correction coefficients;

[0045] The calculation formula of normalized speed is:

[0046]

[0047] Among them, is the speed normalization value, which maps the speed to the 0-1 interval, is the idle speed, such as 600 r / min, is the rated speed, such as 2200 r / min, and N is the current engine speed.

[0048] The calculation formula of normalized torque is:

[0049]

[0050] Among them, is the torque normalization value, which maps the torque to the 0-1 interval, is 0 Nm, is the maximum torque, such as 1400 Nm, and T is the current engine torque.

[0051] The calculation formula of target air-fuel ratio is:

[0052]

[0053]

[0054] Among them is the target air-fuel ratio, is the theoretical air-fuel ratio, = 6.45, - is the working condition correction coefficient, which needs to be obtained by fitting test data on the bench to ensure that the model error is <5%.

[0055] The core of this mathematical model is the correction coefficient - The accurate fitting is achieved through three steps: "bench test - data acquisition - least squares fitting".

[0056] Studies have shown that methanol combustion produces the least amount of formaldehyde within a certain air-fuel ratio range. If the air-fuel ratio is too low, insufficient oxygen will prevent methanol from being completely oxidized into CO2 and H2O, easily generating formaldehyde. If the air-fuel ratio is too high, excessive oxygen can promote oxidation, but it may lead to unstable combustion and misfire, which will increase the amount of unburned methanol. Unburned methanol is converted into formaldehyde in the exhaust system.

[0057] The chemical reaction for the complete combustion of methanol is: 2CH3OH + 3O2 → 2CO2 + 4H2O, where the molar mass of methanol is 32.04 g / mol, the average molar mass of air is 28.97 g / mol, and the volume fraction of oxygen in air is 21%.

[0058] S103. Calculate the intake flow rate based on the intake pressure and intake temperature;

[0059] This requires obtaining the cross-sectional area of ​​the exhaust pipe, the exhaust pressure, and the exhaust temperature.

[0060] The formula for calculating the cross-sectional area A of the exhaust pipe is:

[0061]

[0062] Where d is the diameter of the exhaust pipe.

[0063] The calculation of intake flow rate Q requires parameters such as intake pressure P, intake temperature T, exhaust pressure P, exhaust temperature T, the ratio of the specific heat capacity at constant pressure to the specific heat capacity at constant volume Y of the exhaust gas, the specific gas constant R of the exhaust mixture, and atmospheric pressure K. The specific calculation formula is as follows:

[0064]

[0065] Furthermore, parameter Y is the ratio of the isobaric specific heat capacity to the isovolumetric specific heat capacity of the exhaust gas, parameter R is the specific gas constant of the exhaust mixture, and parameter K is the atmospheric pressure.

[0066] S104. Calculate the actual air-fuel ratio based on the intake air flow rate and methanol injection flow rate;

[0067] The formula for calculating the actual air-fuel ratio β is:

[0068]

[0069] S105. Calculate the air-fuel ratio deviation based on the actual air-fuel ratio and the target air-fuel ratio;

[0070] By comparing the actual air-fuel ratio β and the target air-fuel ratio , to obtain an air-fuel ratio deviation:

[0071]

[0072] S106, according to the engine speed and the air-fuel ratio deviation, determine the injection timing correction coefficient and the injection pressure correction coefficient;

[0073] Wherein the injection timing correction coefficient is calculated by the transient correction model of methanol injection, the horizontal coordinate is the engine speed, and the vertical coordinate is the difference between the actual air-fuel ratio β and the target air-fuel ratio The injection timing represents the time of methanol injection. If the injection is too early, the methanol stays in the low-temperature cylinder wall or intake port for too long, which is easy to form a wall oil film, and the unburned methanol is oxidized to formaldehyde with the exhaust gas; If the injection is too late, the combustion duration is shortened, and the methanol cannot be fully burned, which directly increases the formaldehyde emission.

[0074] Therefore, the transient correction model of methanol injection adjusts the injection timing according to the engine speed and the air-fuel ratio deviation. When the air-fuel ratio deviation is small at low speed, the injection is appropriately delayed to avoid the formation of a wall oil film; When the air-fuel ratio deviation is large at high speed, the injection is advanced to ensure the combustion duration.

[0075] Increasing the injection pressure of methanol can enhance the atomization effect of methanol, make the methanol and air mix more uniformly, and avoid the occurrence of local over-concentration gas. However, if a higher injection pressure is still used in the area with a small injection timing, the penetration distance of the liquid is large, and the methanol at the end will directly hit the piston to form a wall oil film.

[0076] Therefore, the transient correction model of methanol injection adjusts the injection pressure according to the engine speed and the air-fuel ratio deviation. When the air-fuel ratio deviation is large at high speed, the injection pressure is increased to improve the atomization of methanol; When the air-fuel ratio deviation is small at low speed, the injection pressure is reduced to avoid the formation of a wall oil film by methanol hitting the wall.

[0077] Specifically, when the engine speed is greater than a preset speed threshold and the air-fuel ratio deviation is greater than a first deviation threshold, the injection pressure is increased; when the engine speed is less than the preset speed threshold and the air-fuel ratio deviation is less than a second deviation threshold, the injection pressure is reduced.

[0078] The injection timing correction coefficient is as shown in Figure 2 The calculation formula is:

[0079]

[0080] Wherein, is the transient correction coefficient of methanol injection timing. The calculation formula of the speed correction coefficient is:

[0081]

[0082] Wherein 、 、 is a coefficient, which needs to be fitted by test data on the test bench, and the quadratic term fitting is used to cover the high and low speed nonlinear characteristics.

[0083] Torque correction coefficient The calculation formula is:

[0084]

[0085] wherein 、 is a coefficient, which needs to be fitted by test data on the test bench, and the linear fitting is used for high load to stabilize the increase time.

[0086] Coupling correction coefficient The calculation formula is:

[0087]

[0088] wherein is a coefficient, which needs to be fitted by test data on the test bench, and the interaction term fitting is only used for extreme conditions to take effect.

[0089] The above coefficients need to ensure that the model matches the actual engine performance, with an error of <5%.

[0090] S107, according to the air-fuel ratio deviation, adjusting the opening of the throttle; and according to the injection timing correction coefficient and the injection pressure correction coefficient, adjusting the injection timing and injection pressure of the methanol injector.

[0091] According to the air-fuel ratio deviation, adjusting the opening of the throttle; wherein when β , the intake air amount is reduced by reducing the opening of the throttle valve installed in the intake pipe; when β , the intake air amount is increased by increasing the opening of the throttle valve.

[0092] The final injection timing output value = basic timing x injection timing correction coefficient, and the adjustment method of the injection pressure is consistent with the injection timing correction method.

[0093] As shown in Figure 3 , by implementing the method, the problem of local rich mixture caused by the rapid change of air-fuel ratio of the engine during acceleration or load mutation is solved, and the bench test shows that the formaldehyde emission of the engine in the WHTC cycle is reduced by 25% after using the method.

[0094] The application further provides a device for controlling formaldehyde emission of a methanol engine, which is applied to a methanol engine control system.

[0095] The acquisition module acquires engine speed and engine load from the engine controller, acquires intake pressure and intake temperature from the intake pipe pressure temperature sensor, and acquires methanol injection flow from the fuel pipeline metering valve; according to the engine speed and engine load, normalized speed and normalized torque are calculated; according to the normalized speed, the normalized torque and a plurality of preset correction coefficients, a target air-fuel ratio is calculated.

[0096] The calculation module calculates intake flow according to the intake pressure and intake temperature, calculates an actual air-fuel ratio according to the intake flow and methanol injection flow, and calculates an air-fuel ratio deviation according to the actual air-fuel ratio and the target air-fuel ratio.

[0097] The coefficient module determines injection timing correction coefficients and injection pressure correction coefficients according to the engine speed and the air-fuel ratio deviation.

[0098] The adjustment module adjusts the opening degree of the throttle valve according to the air-fuel ratio deviation, and adjusts the injection timing and injection pressure of the methanol injector according to the injection timing correction coefficients and injection pressure correction coefficients.

[0099] The application further provides an electronic device, which comprises a memory and a processor, the memory stores a computer program, and the processor controls the execution of the above method when executing the computer program.

[0100] The application further provides a computer readable storage medium, which stores a computer program, and the computer program controls the execution of the above method when executed in a computer.

Claims

1. A method of controlling the emission of formaldehyde from a methanol engine, characterized by, The method is applied to a methanol engine control system, and the methanol engine control system comprises an intake pipe pressure temperature sensor, a fuel pipe metering valve, an engine controller, a throttle valve and a methanol injector. Obtaining engine speed and engine load from the engine controller, obtaining intake pressure and intake temperature from the intake pipe pressure temperature sensor, and obtaining methanol injection flow from the fuel pipe metering valve; According to the engine speed and engine load, calculating a normalized speed and a normalized torque; according to the normalized speed, the normalized torque and a plurality of preset correction coefficients, calculating a target air-fuel ratio; According to the intake pressure and the intake temperature, calculating an intake flow; According to the intake flow and the methanol injection flow, calculating an actual air-fuel ratio; According to the actual air-fuel ratio and the target air-fuel ratio, calculating an air-fuel ratio deviation; According to the engine speed and the air-fuel ratio deviation, determining an injection timing correction coefficient and an injection pressure correction coefficient; According to the air-fuel ratio deviation, adjusting the opening degree of the throttle valve; and according to the injection timing correction coefficient and the injection pressure correction coefficient, adjusting the injection timing and the injection pressure of the methanol injector.

2. The method of claim 1, wherein, The method comprises: Obtaining an exhaust pipe cross-sectional area, an exhaust pressure and an exhaust temperature; According to the intake pressure, the intake temperature, the exhaust pipe cross-sectional area, the exhaust pressure and the exhaust temperature, calculating an intake flow.

3. The method of claim 1, wherein, The method comprises: Using a product term of the normalized speed and the normalized torque and a product term correction coefficient to calculate the target air-fuel ratio.

4. The method of claim 1, wherein, The method comprises: According to a quadratic polynomial function of the normalized speed, calculating the injection timing correction coefficient.

5. The method of claim 4, wherein, The method comprises: According to a linear function of the normalized torque, calculating the injection timing correction coefficient.

6. The method of claim 5, wherein, The method comprises: According to a product term and an interaction term correction coefficient of the normalized speed and the normalized torque, calculating the injection timing correction coefficient.

7. The method of claim 1, wherein, The method comprises: Conditionally adjusting the injection pressure according to the size of the engine speed and the air-fuel ratio deviation; When the engine speed is greater than a preset speed threshold and the air-fuel ratio deviation is greater than a first deviation threshold, the injection pressure is increased; When the engine speed is less than a preset speed threshold and the air-fuel ratio deviation is less than a second deviation threshold, the injection pressure is decreased.

8. An apparatus for controlling the emission of formaldehyde from a methanol engine, characterized by comprising: The method is applied to a methanol engine control system, and the methanol engine control system comprises an intake pipe pressure temperature sensor, a fuel pipe metering valve, an engine controller, a throttle valve and a methanol injector. An acquisition module acquires engine speed and engine load from the engine controller, acquires intake pressure and intake temperature from the intake pipe pressure temperature sensor, and acquires methanol injection flow rate from the fuel pipe metering valve; calculates normalized speed and normalized torque based on the engine speed and engine load; and calculates target air-fuel ratio based on the normalized speed, the normalized torque, and a plurality of preset correction coefficients; A calculation module calculates intake flow rate based on the intake pressure and intake temperature, calculates actual air-fuel ratio based on the intake flow rate and methanol injection flow rate, and calculates air-fuel ratio deviation based on the actual air-fuel ratio and the target air-fuel ratio; A coefficient module determines injection timing correction coefficient and injection pressure correction coefficient based on the engine speed and the air-fuel ratio deviation; An adjustment module adjusts the opening degree of the throttle valve based on the air-fuel ratio deviation, and adjusts the injection timing and injection pressure of the methanol injector based on the injection timing correction coefficient and injection pressure correction coefficient.

9. An electronic device, comprising: A computer program product including a memory and a processor, the memory having stored therein a computer program, the processor, when executing the computer program, controlling execution of the method of any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, A computer program product having stored thereon a computer program that, when executed in a computer, causes the computer to control execution of the method of any one of claims 1-7.

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