CN107975432B - A dual fuel engine and its control method - Google Patents

Abstract

The invention discloses a dual-fuel engine and a control method thereof, comprising an ignition device and a throttle valve device, both of which are connected with the engine ECU; the spark plug of the ignition device is installed on the cylinder head of the engine; the throttle valve device is installed On the intake manifold of the engine; a control method for a dual-fuel engine is also disclosed; the present disclosure solves the problem that the existing dual-fuel engine cannot use spark-ignition fuel under small load conditions, and realizes the dual-fuel engine in a small The full substitution of ignition fuel to compression ignition fuel under load conditions (100% substitution rate) improves the economy and emissions of existing dual-fuel engines under low-load conditions, and gives full play to the performance advantages of dual-fuel engines.

Description

A dual fuel engine and its control method

technical field

The invention belongs to the field of engine technology and control methods, and relates to a dual-fuel engine and a control method thereof.

Background technique

Due to the difference in physical and chemical properties, the application methods of ignition fuel in compression ignition engines mainly include emulsion method, combustion-supporting method, direct compression ignition method, and dual-fuel method. Among them, the dual-fuel method means that during the operation of the engine, part of the ignition fuel is input into the cylinder of the compression ignition engine through the intake system or the oil supply system, and a part of the premixed combustible mixture is formed in the cylinder, and then stops at the top of compression. A small amount of compression-ignition fuel is injected into the cylinder near the point, and the pre-mixed combustible gas mixture formed by the ignition-type fuel and air is ignited by compressing the ignition-type fuel, so that the engine can burn the ignition-type fuel and compression-ignition at the same time. type fuel. Using the dual fuel method to apply some ignition fuels (such as natural gas, methanol, etc.) to the compression ignition engine not only helps to improve the effective thermal efficiency of the original compression ignition engine, reduces the equivalent effective fuel consumption rate, but also helps To reduce the exhaust emissions of the original compression ignition engine. Therefore, the application of some ignition fuels (such as natural gas, methanol, etc.) to the compression ignition engine by the dual fuel method is of great significance for alleviating the energy security problems caused by the shortage of traditional compression ignition fuel-diesel supply and improving the original compression ignition type. The environmental problems caused by engine exhaust emission have important theoretical significance and practical value.

Due to the many advantages of the dual-fuel method, many domestic and foreign scientific research institutions and colleges and universities have invested a lot of manpower and material resources to carry out related research, and achieved a series of technical achievements, but also found some outstanding problems, which have not yet been solved. Yao Chunde of Tianjin University, Liu Shenghua of Xi'an Jiaotong University, Zhang Chunhua and Liu Shengquan of Chang'an University and others found that under small load conditions, the injection of ignited fuel (when the substitution rate is small) will cause combustion lag, the combustion temperature will decrease, and the combustion cycle will change. large, the economy deteriorates, accompanied by higher CO and HC emissions; and if you continue to increase the ignition fuel supply (increase the ignition fuel substitution rate) or reduce the engine workload, the pressure that plays the role of ignition at this time. If the amount of ignited fuel is too small, the vaporization of a large amount of ignited fuel has an obvious cooling effect on the fresh charge, and the ignited fuel has an obvious inhibitory effect on the ignition of compression ignition fuel, which may easily cause the engine to misfire and cause the engine to fail to work.

Due to the poor performance of dual-fuel engines using spark-ignition fuel and compression-ignition fuel dual-fuel operation under low-load conditions, in practical applications, dual-fuel engines mainly use spark-ignition fuel and compression-ignition fuel under medium and high load conditions. Due to the dual-fuel operation of type fuel, the substitution rate of ignition type fuel (such as natural gas, methanol, etc.) to compression ignition type fuel is relatively low. Therefore, it is urgent to develop a new type of dual-fuel engine and its system control method, so that the dual-fuel engine can burn ignition fuel under small load conditions, and achieve a substantial increase in the replacement rate of ignition fuel to compression ignition fuel, and Take full advantage of the performance benefits of dual-fuel engines.

SUMMARY OF THE INVENTION

In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a dual-fuel engine and a control method thereof, so as to solve the problem that the existing dual-fuel engine cannot use spark-ignition fuel under low-load conditions, and realize dual-fuel engine. The full substitution of ignition fuel for compression ignition fuel (100% replacement rate) for fuel engines under low load conditions improves the economy and emissions of existing dual-fuel engines under low-load conditions, and gives full play to dual-fuel engines performance advantage.

In order to achieve the above object, the present invention adopts the following technical solutions:

A control method of a dual-fuel engine, comprising the following steps:

(1) The dual-fuel engine is under cold start, warm-up or idling conditions

(1) The opening of the throttle valve remains fully closed;

(2) The compression ignition fuel injector stops working;

(3) Determine the injection quantity of ignition fuel according to the required value of the excess air coefficient λ of the mixture under cold start, warm-up and idling conditions;

(4) ignite when the piston moves to 5° CA before compression top dead center, and ignite the combustible mixture formed by the ignited fuel and air;

(5) The throttle valve position sensor measures the throttle valve opening signal, and the engine ECU performs closed-loop correction on the throttle valve opening ψ according to the throttle valve opening signal, so that the throttle valve of the dual-fuel engine is in cold start, warm-up and idle speed. It is completely closed under working conditions;

The engine ECU performs closed-loop correction on the fuel injection pulse width of the ignition fuel injector according to the oxygen content in the exhaust pipe of the engine, so that the value of the excess air coefficient λ of the mixture is always the mixture under cold start, warm-up and idle speed conditions. The required value of the excess air coefficient λ.

(2) The dual-fuel engine is at idle speed-30% load, that is, under the condition of small load

(1) The throttle opening Φ is increased from 0% to 30%;

(2) The engine ECU adjusts the throttle valve opening degree ψ according to the relationship between the throttle valve opening degree ψ and the accelerator opening degree Φ; according to the required value of the excess air coefficient λ of the mixture under the condition of small load, determines the injection ignition type fuel. quantity; compression ignition fuel injector stops working;

(3) ignite when the piston moves to 10° CA before compression top dead center, and ignite the combustible mixture formed by the ignited fuel and air;

(4) The throttle valve position sensor measures the throttle valve opening signal, and the engine ECU performs closed-loop correction on the throttle valve opening degree ψ according to the throttle valve opening degree signal, so that the throttle valve opening degree conforms to the throttle valve opening degree ψ. The change relationship of degree Φ;

The engine ECU performs closed-loop correction on the injection pulse width of the ignition fuel injector according to the oxygen content, so that the excess air coefficient λ of the mixture is the required value of the excess air coefficient λ of the mixture under the condition of small load.

(3) The dual-fuel engine is under the condition of 30%-100% load

(1) The throttle opening Φ is increased from 30% to 100%;

(2) Determine the engine speed n;

(3) The throttle valve opening ψ is quickly adjusted to fully open;

(4) The spark plug stops flashing;

(5) Determine the value of the excess air coefficient λ of the mixer and the value of the substitution rate L under the current accelerator opening Φ and the engine speed n, and determine the ignition type according to the value of the excess air coefficient λ of the mixer and the value of the substitution rate L. Fuel injection quantity and compression ignition fuel injection quantity;

(6) The engine ECU performs closed-loop correction on the injection pulse width of the compression ignition fuel injector and the ignition fuel injector.

Optionally, the closed-loop correction of the injection pulse width of the compression ignition fuel injector and the ignition fuel injector specifically includes the following process:

Detect the oxygen concentration in the engine exhaust pipe, and the engine ECU compares the detected oxygen concentration with the target range. If the oxygen concentration in the exhaust pipe is lower than the minimum value of the target range, the engine ECU sends a control command and reduces the pressure at the same time. The fuel injection pulse width of the fired fuel injector and the ignition fuel injector;

If the oxygen concentration in the exhaust pipe is higher than the maximum value of the target range, the engine ECU sends a control command and increases the injection pulse width of the compression ignition fuel injector and the ignition fuel injector;

If the oxygen concentration in the exhaust pipe is within the target range, adjust the fuel injection pulse width of the compression ignition fuel injector and the ignition fuel injector. The specific process is: if a knock signal is detected, the engine The ECU sends a control command to reduce the fuel injection pulse width of the ignition fuel injector and correspondingly increase the fuel injection pulse width of the compression ignition fuel injector, and keep the excess air coefficient λ unchanged; if no knocking is detected signal, the engine ECU sends a control command to increase the fuel injection pulse width of the ignition fuel injector and reduce the fuel injection pulse width of the compression ignition fuel injector, and maintain the excess air coefficient λ remains unchanged.

The present disclosure also provides a dual-fuel engine, the dual-fuel engine further includes an ignition device and a throttle valve device, both of which are connected to the engine ECU; the spark plug of the ignition device is mounted on the cylinder head of the engine ; the throttle valve device is installed on the intake manifold of the engine;

In the ignition device, when the dual-fuel engine is under cold start, warm-up or idle speed conditions, the spark plug of the ignition device is ignited when the piston moves to 5° CA before compression top dead center, and the ignition-type fuel and air are formed. When the dual-fuel engine is at idle speed -30% load, that is, under the condition of small load, the spark plug ignites when the piston moves to 10° CA before compression top dead center, igniting the combustible mixture formed by the ignited fuel and air. Mixed gas; when the dual-fuel engine is in the working condition of 30%-100% load, the spark plug stops flashing;

The throttle valve device is kept fully closed when the dual-fuel engine is in cold start, warm-up or idling conditions; and when the dual-fuel engine is in idle speed-30% load, that is, a small load condition, the throttle valve is opened. The degree ψ varies with the throttle opening Φ; when the dual-fuel engine is under 30%-100% load conditions, the throttle valve opening ψ is fully open.

Optionally, the throttle valve device includes a throttle valve and a throttle valve position sensor, the throttle valve is a circular structure, and when the axis of the throttle valve is consistent with the axis of the intake manifold, the edge of the throttle valve and the There is a gap between the intake manifolds.

Compared with the prior art, the present invention has the following technical effects:

1. The present invention installs an ignition system on the traditional dual-fuel engine, so that the engine can work in a way of igniting and igniting under cold start, warm-up, idling and low-load conditions, and solves the problem that the traditional dual-fuel engine cannot be under low-load conditions. Disadvantages of normal burning of ignited fuel.

2. Under cold start, warm-up, idle speed and small load conditions, by adjusting the opening of the throttle valve, the relative compression ratio of the in-cylinder mixture under actual operation can be effectively controlled to prevent the ignition of the fuel mixture from occurring during the combustion process. knocking phenomenon.

3. The dual-fuel engine controls the excess air coefficient of the mixture under various operating conditions, and uses a rich mixture in cold start, warm-up and idle conditions, which is convenient for cold start, warm-up and idle speed of the engine; Use an economical mixture to improve the economy of dual-fuel engines using spark-ignition fuel; use a lean mixture under medium and heavy load conditions to improve the combustion quality of dual-fuel engine mixtures, achieve good economy and reduce exhaust emissions .

4. The load adjustment method of dual-fuel engine: under small load conditions, use volume adjustment (adjust the size of the load by adjusting the amount of the mixture), and use quality adjustment under large load conditions (adjust the load by adjusting the amount of work substance The size of the load is adjusted by adjusting the concentration of the mixture).

5. The present invention updates the ECU control strategy of the traditional dual-fuel engine, so as to realize single combustion of ignition type fuel under cold start, warm-up, idle speed and small load conditions, and simultaneous combustion of ignition type fuel and ignition type fuel under medium and large load conditions. Compression ignition fuel.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a dual-fuel engine with spark-in-cylinder injection;

Fig. 2 is the structural principle diagram of the dual-fuel engine with ignition type fuel port injection;

FIG. 3 is a graph showing the change of the throttle opening of the dual-fuel engine with the throttle opening;

Fig. 4 is a graph showing the variation of the mixture concentration of a dual-fuel engine with operating conditions;

Fig. 5 is a graph showing the change of ignition fuel substitution rate with working conditions;

DESCRIPTION OF REFERENCE NUMERALS: 1 muffler; 2 reduction catalytic converter; 3 oxidation catalytic converter; 4 oxygen sensor; 5 exhaust valve; 6 compression ignition fuel supply circuit; 7 compression ignition fuel injector; 8 spark plug ; 9 intake valves; 10 ignition fuel injectors; 11 throttle valves; 12 throttle position sensors; 13 air filters; 14 engine ECUs; 15 engine cylinder walls; 16 engine pistons; 17 throttle valves; 18 throttle position sensors ; 19 knock sensor; 20 rev sensor.

The solution of the present invention will be further explained and described in detail below in conjunction with the accompanying drawings and specific embodiments.

Detailed ways

The present disclosure provides a control method for a dual-fuel engine, which realizes the operation in the mode of ignition and ignition under cold start, warm-up, idle speed and small load conditions, and in the mode of compression ignition under medium and large load conditions. work, including the following:

(1) The dual-fuel engine is under cold start, warm-up or idling conditions

(1) The engine ECU 14 controls the opening of the throttle valve 11 to remain fully closed, and air still enters at this time;

(2) The engine ECU 14 controls the compression ignition fuel injector 7 to stop working;

(3) The engine ECU 14 controls the ignition type fuel injector 10 to determine the amount of injected ignition type fuel according to the requirements of the mixture concentration under cold start, warm-up and idling conditions, that is, the excess air coefficient λ<1. In this embodiment, Excess air coefficient λ=0.85; see Figure 4 for mixture concentration requirements, excess air coefficient λ=actually supplied air amount/air amount required for complete combustion of fuel;

Among them, the amount of injected ignition fuel is determined according to the excess air coefficient λ. The specific process is as follows: when the dual-fuel engine is in cold start, warm-up or idling conditions, the amount of air entering the engine through the throttle valve is known, According to the excess air coefficient λ, the amount of air required for the complete combustion of the fuel can be known, and the amount of the injected ignition fuel can be determined according to the corresponding relationship between the air amount required for the complete combustion of the fuel and the amount of the injected ignition fuel;

(4) The engine ECU 14 controls the spark plug 8 of the ignition device to ignite when the piston moves to 5° CA before the compression top dead center, and ignites the combustible mixture formed by the ignited fuel and air;

(5) The throttle valve position sensor 12 measures the opening signal of the throttle valve 11, and the engine ECU 14 performs closed-loop correction on the throttle valve opening ψ according to the opening signal of the throttle valve 11, so that the throttle valve 11 is used in cold start, warm-up and idle operation. is completely closed;

The oxygen sensor 4 measures the oxygen content in the exhaust pipe of the engine, and the engine ECU 14 performs closed-loop correction on the fuel injection pulse width of the ignition fuel injector 10 according to the oxygen content, so that the dual-fuel engine can be used for cold start, warm-up and idle speed. Under the working conditions, the excess air coefficient λ of the mixture is controlled at 0.85. Specifically, the oxygen sensor 4 measures the oxygen content in the exhaust pipe, and when the measured oxygen content is greater than the threshold corresponding to λ=0.85, the engine ECU 14 controls the fuel injection pulse width of the ignition fuel injector 10 to increase, When the measured oxygen content is less than the threshold value corresponding to λ=0.85, the engine ECU 14 controls the fuel injection pulse width of the spark ignition fuel injector 10 to decrease.

(2) The dual-fuel engine is at idle speed-30% load, that is, under the condition of small load

(1) Depress the accelerator pedal and increase the accelerator opening Φ from 0% to 30%;

(2) The engine ECU 14 adjusts the opening degree ψ (0-45%) of the throttle valve 11 according to the changing relationship between the throttle valve opening degree ψ and the accelerator opening degree Φ, as shown in FIG. 3; In the case of , the slope of the straight line in FIG. 3 is k=1.5; at the same time, the engine ECU 14 has the mixture excess air coefficient λ=1.05～1.15 according to the mixture concentration requirement under small load conditions. In this embodiment, the mixture excess air Coefficient λ=1.10, determine the amount of injected ignition type fuel, adjust the injection pulse width of ignition type fuel injector 10, at this time compression ignition type fuel injector 7 still stops working under the control of engine ECU14;

(3) The engine ECU 14 controls the spark plug 8 to ignite when the piston moves to 10° CA before the compression top dead center, and ignites the combustible mixture formed by the ignited fuel and air;

(4) The throttle valve position sensor 12 measures the opening degree signal of the throttle valve 11, and the engine ECU 14 performs closed-loop correction on the throttle valve opening degree ψ according to the opening degree signal of the throttle valve 11, so that the throttle valve 11 is kept at the throttle valve obtained according to FIG. 3 . The size of the valve opening;

The oxygen sensor 4 measures the oxygen content in the exhaust pipe, and the engine ECU 14 performs closed-loop correction on the fuel injection pulse width of the ignition fuel injector 10 according to the oxygen content, so that the dual-fuel engine has an excess air ratio of the mixture under low load conditions. Controlled at 1.10. Specifically, the oxygen sensor 4 measures the oxygen content in the exhaust pipe. When the measured oxygen content is greater than the threshold value corresponding to λ=1.10, the engine ECU 14 controls the fuel injection pulse width of the ignition fuel injector 10 to increase, When the measured oxygen content is less than the threshold value corresponding to λ=1.10, the engine ECU 14 controls the fuel injection pulse width of the spark-ignition fuel injector 10 to decrease.

(3) The dual-fuel engine is under 30%-100% load conditions

(1) Depress the accelerator pedal and increase the accelerator opening Φ from 30% to 100%;

(2) The engine ECU 14 analyzes and processes the accelerator opening signal obtained by the accelerator position sensor 18 and the rotational speed signal obtained by the rotational speed sensor 20, and determines the accelerator opening Φ (30%-100%) and the engine speed n;

(3) The engine ECU14 controls the throttle valve opening ψ to be quickly adjusted to fully open;

(4) The engine ECU 14 controls the spark plug 8 to stop sparking;

(5) The engine ECU 14 determines the value of the excess air coefficient λ of the mixer under the current accelerator opening Φ (30%-100%) and the engine speed n according to the change curve of the mixture concentration with the working conditions (Fig. 4). The excess air coefficient λ determines the total amount of the two fuels; in the case of determining the total amount of the two fuels, according to the change curve of the substitution rate with the working conditions (Fig. 5), find the fuel injection of the spark-ignited fuel injector 10 and the injection amount of the compression ignition fuel injector 7, and adjust the injection pulse width of the ignition fuel injector 10 and the injection pulse width of the compression ignition fuel injector 7 according to the obtained fuel injection amount ;

Among them, the replacement rate

Note: m _D - ignition fuel mass consumption rate

H _μD - Ignition fuel low calorific value

m _Y - Compression ignition fuel mass consumption rate

H _μY - low calorific value of compression ignition fuel

Among them, H _μD - the low calorific value of the ignition fuel and H _μY - the low calorific value of the compression ignition fuel are constants. When the total amount of the two fuels is known, the mass consumption rate m of the ignition fuel can be obtained according to the above formula _D and the compression ignition fuel mass consumption rate m _Y .

In this embodiment, in the curve equation shown in Figure 4, when the rotational speed n=1550r/min, the corresponding relationship between the excess air coefficient and the accelerator opening is as follows:

When n=1850r/min, the corresponding relationship between the excess air coefficient and the throttle opening is as follows:

Among them, y is the excess air coefficient; x is the throttle opening

The curve equation shown in Figure 5, when n=1550r/min, the corresponding relationship between the substitution rate and the accelerator opening is as follows:

When n=1850r/min, the corresponding relationship between the substitution rate and the accelerator opening is as follows:

Among them, z is the replacement rate; x is the accelerator opening.

(6) The engine ECU 14 performs closed-loop correction on the injection pulse widths of the compression ignition fuel injector 7 and the ignition fuel injector 10 according to the feedback signals of the oxygen sensor 4 and the knock sensor 19, thereby realizing precise adjustment of the engine load . The specific process is:

The oxygen sensor 4 detects the oxygen concentration in the engine exhaust pipe, and feeds back the detection result to the engine ECU 14 . The engine ECU 14 compares the detection result with the target range, and if the oxygen concentration in the exhaust pipe is lower than the minimum value of the target range, the engine ECU 14 issues a control command and simultaneously reduces the compression ignition fuel injector 7 and the ignition fuel injection The fuel injection pulse width of the injector 10;

If the oxygen concentration in the exhaust pipe is higher than the maximum value of the target range, the engine ECU 14 issues a control command, and simultaneously increases the injection pulse width of the compression ignition fuel injector 7 and the ignition fuel injector 10;

If the oxygen concentration in the exhaust pipe is within the target range, the injection pulse width of the compression ignition fuel injector 7 and the ignition fuel injector 10 is adjusted according to the feedback signal of the knock sensor 19. The sensor 19 detects the knock signal, and the engine ECU 14 issues a control command to reduce the fuel injection pulse width of the ignition type fuel injector 10 and correspondingly increase the fuel injection pulse width of the compression ignition fuel injector 7, and maintain the excess air coefficient λ remain unchanged; if the knock sensor 19 does not detect a knock signal, the engine ECU 14 sends a control command to increase the injection pulse width of the ignition type fuel injector 10 and reduce the injection pulse width of the compression ignition type fuel injector 7 wide, and the excess air coefficient λ remains unchanged.

(4) The process of reducing the load of the dual-fuel engine

In the process of load reduction, it will return to the idle state or stop in the reverse direction according to the control route of the original load increase process.

The invention controls the mixture gas concentration under each working condition of the dual-fuel engine, and adopts a rich mixture (excess air coefficient λ=0.85) under cold start, warm-up and idling conditions, so that the engine is easy to start from cold, accelerate to warm-up and improve the efficiency of the engine. The idle speed is stable; the economical mixture (excess air coefficient λ=1.10) is used under small load conditions to improve the economy of dual-fuel engines using sparked fuel; in medium and large load conditions, the lean mixture is used, Improve the combustion quality of the dual-fuel engine mixture, obtain good economy and reduce exhaust emissions.

The dual-fuel engine combines the characteristics of its own exhaust emission pollutants, and adopts an oxidation catalytic converter and a reduction catalytic converter at the same time, which can better reduce the soot, NOx, CO and HC in the exhaust.

The invention controls the dual-fuel engine under the small load condition by adopting the quantity adjustment, and solves the disadvantage of the narrow ignition limit of the ignition type fuel. So that the ignition fuel can ensure good performance in the entire small load working range.

The present invention realizes the full substitution of the ignition type fuel for the compression ignition type fuel (the replacement rate is 100%) under the conditions of cold start, warm-up, idle speed and small load of the dual-fuel engine, which will greatly improve the dual-fuel engine ignition type fuel ( Such as natural gas, methanol, etc.) to the replacement rate of compression ignition fuel, thereby further alleviating the shortage of traditional compression ignition fuel-diesel supply in my country. At the same time, the use of ignited fuel at a higher relative compression ratio is conducive to giving full play to the high octane number of some ignited fuels (such as natural gas, methanol, etc.), and improving the power, economy and efficiency of the new dual-fuel engine. Emissions, which not only help to further reduce fuel consumption and improve energy security, but also help to reduce pollutant emissions and improve the environmental protection of fuels.

Another aspect of the present disclosure provides a dual fuel engine, referring to FIGS. 1 and 2 , comprising an ignition device and a throttle valve device, a spark plug 8 of the ignition device is mounted on a cylinder head of the dual fuel engine, and is controlled by the engine ECU 14 The throttle valve device is installed on the intake manifold, and the throttle valve device is connected to the engine ECU 14 ; the throttle valve device includes a throttle valve 11 and a throttle valve position sensor 12 .

The present disclosure installs an ignition system on a traditional dual-fuel engine, so that the engine can work in a way of igniting and igniting under cold start, warm-up, idling and low-load conditions, and solves the problem that the traditional dual-fuel engine cannot be ignited under low-load conditions. Disadvantages of ignited fuel. Under cold start, warm-up, idling and low-load conditions, the throttle position sensor 12 can collect the opening degree information of the throttle valve 11, and transmit the information to the engine ECU 14. By adjusting the opening degree of the throttle valve 11, the relative compression ratio of the in-cylinder mixture under the actual working state can be effectively controlled, and the knocking phenomenon can be prevented during the combustion process of the ignition fuel mixture. .

In this embodiment, the ignition type fuel can be port injection or in-cylinder direct injection. An oxygen sensor 4, a rotational speed sensor 20 and a knock sensor 19 are also installed on the dual-fuel engine, wherein the oxygen sensor 4 is installed on the exhaust pipe, the rotational speed sensor 20 is installed at the end of the crankshaft, and the knock sensor 19 is installed on the dual-fuel engine on the body.

In this embodiment, the throttle valve 11 has a circular structure. When the axis of the throttle valve 11 is consistent with the axis of the intake manifold, there is a gap between the edge of the throttle valve 11 and the intake manifold. The gap ensures that when the throttle valve 11 is in a fully closed state, there is still air entering the cylinder of the engine from the intake manifold. The engine burns combustibles, and then converts the heat energy released by the combustion into mechanical energy, thereby performing work on the outside world. Combustible combustion must have oxygen (air). Under cold start, warm-up and idling conditions, the throttle valve is fully closed (that is, the throttle valve opening is the smallest).

In the described ignition device, when the dual-fuel engine is under cold start, warm-up or idle speed conditions, the spark plug 8 of the ignition device is ignited when the piston moves to 5° CA before compression top dead center, and the ignition type fuel and air are ignited. The formed combustible gas mixture; when the dual-fuel engine is at idle speed -30% load, that is, under the condition of small load, the spark plug 8 ignites when the piston moves to 10° CA before the compression top dead center, and the ignition type fuel and air are ignited. When the dual-fuel engine is under the condition of 30%-100% load, the spark plug 8 stops flashing.

The throttle valve device is kept fully closed when the dual-fuel engine is in cold start, warm-up or idling conditions; and when the dual-fuel engine is in idle speed-30% load, that is, a small load condition, the throttle valve is opened. The degree ψ varies with the throttle opening Φ; when the dual-fuel engine is under 30%-100% load conditions, the throttle valve opening ψ is fully open.

The engine of the invention adopts the air intake throttling method to change the relative compression ratio of the dual-fuel engine under cold start, warm-up, idling and low-load conditions, so as to avoid the dual-fuel engine's excessively large compression ratio causing the dual-fuel engine to use the ignition type The fuel is knocked.

By installing the ignition system, the dual-fuel engine can work in the way of ignition and ignition under cold start, warm-up, idle speed and small load conditions, which solves the defect of low cetane number and difficult compression ignition of ignition type fuel.

A third aspect of the present disclosure provides a method for controlling a dual-fuel engine, comprising the following steps:

(1) The dual-fuel engine is under cold start, warm-up or idling conditions

(1) The opening of the throttle valve (11) remains fully closed;

(2) The compression ignition fuel injector 7 stops working;

(3) Determine the injection quantity of ignition fuel according to the required value of the excess air coefficient λ of the mixture under cold start, warm-up and idling conditions;

(4) ignite when the piston moves to 5° CA before compression top dead center, and ignite the combustible mixture formed by the ignited fuel and air;

(5) The throttle valve position sensor 12 measures the opening degree signal of the throttle valve 11, and the engine ECU 14 performs closed-loop correction on the throttle valve opening degree ψ according to the opening degree signal of the throttle valve 11, so that the throttle valve 11 of the dual-fuel engine is cold-started, Fully shut down in warm and idling conditions;

The engine ECU 14 performs closed-loop correction on the fuel injection pulse width of the ignition fuel injector 10 according to the oxygen content in the exhaust pipe of the engine, so that the value of the excess air coefficient λ of the mixture is always the same as that under cold start, warm-up and idle speed conditions. The required value of the excess air coefficient λ of the mixture.

(2) The dual-fuel engine is at idle speed-30% load, that is, under the condition of small load

(1) The throttle opening Φ is increased from 0% to 30%;

(2) The engine ECU 14 adjusts the opening degree ψ of the throttle valve 11 according to the relationship between the throttle valve opening degree ψ and the accelerator opening degree Φ; and determines the injection ignition type fuel according to the required value of the excess air coefficient λ of the mixture under the condition of small load amount; the compression ignition fuel injector 7 stops working;

(3) ignite when the piston moves to 10° CA before compression top dead center, and ignite the combustible mixture formed by the ignited fuel and air;

(4) The throttle valve position sensor 12 measures the opening degree signal of the throttle valve 11, and the engine ECU 14 performs closed-loop correction on the throttle valve opening degree ψ according to the opening degree signal of the throttle valve 11, so that the opening degree of the throttle valve 11 matches the throttle valve opening degree The relationship between ψ and the throttle opening Φ;

The engine ECU 14 performs closed-loop correction on the injection pulse width of the spark-ignition fuel injector 10 according to the oxygen content, so that the mixture excess air coefficient λ is the required value of the mixture excess air coefficient λ under light load conditions.

(3) The dual-fuel engine is under the condition of 30%-100% load

(1) The throttle opening Φ is increased from 30% to 100%;

(2) Determine the engine speed n;

(3) The throttle valve opening ψ is quickly adjusted to fully open;

(4) The spark plug 8 stops flashing;

(5) Determine the value of the excess air coefficient λ of the mixer and the value of the substitution rate under the current accelerator opening Φ and the engine speed n, and determine the value of the ignition fuel according to the value of the excess air coefficient λ of the mixer and the value of the substitution rate. The amount of fuel injected and the amount of compression ignition fuel;

(6) The engine ECU 14 performs closed-loop correction on the injection pulse widths of the compression ignition type fuel injector 7 and the ignition type fuel injector 10 .

Claims (3)

1. a control method of a dual fuel engine, is characterized in that, comprises the following steps: (1) The dual-fuel engine is under cold start, warm-up or idling conditions (1) The opening of the throttle valve (11) remains fully closed. When the axis of the throttle valve (11) is consistent with the axis of the intake manifold, there is a gap between the edge of the throttle valve (11) and the intake manifold. void; (2) The compression ignition fuel injector (7) stops working; (3) Determine the injection quantity of ignition fuel according to the required value of the excess air coefficient λ of the mixture under cold start, warm-up or idling conditions; (4) Ignition is carried out when the piston moves to 5°CA before compression top dead center, and the combustible mixture formed by ignition fuel and air is ignited; (5) The throttle valve position sensor (12) measures the opening degree signal of the throttle valve (11), and the engine ECU (14) performs closed-loop correction on the throttle valve opening degree ψ according to the opening degree signal of the throttle valve (11), so that the dual fuel The throttle valve (11) of the engine is fully closed during cold start, warm-up or idle conditions; The engine ECU (14) performs closed-loop correction on the fuel injection pulse width of the ignition type fuel injector (10) according to the oxygen content in the exhaust pipe of the engine, so that the value of the excess air coefficient λ of the mixture is always the value of cold start and warm-up. or the required value of the excess air coefficient λ of the mixture under idle speed conditions; (2) The dual-fuel engine is at idle speed-30% load, that is, under the condition of small load (1) The throttle opening Φ is increased from 0% to 30%; (2) The engine ECU (14) adjusts the opening degree ψ of the throttle valve (11) according to the relationship between the throttle valve opening degree ψ and the accelerator opening degree Φ; Determine the amount of injected ignition fuel; the compression ignition fuel injector (7) stops working; (3) Ignition is carried out when the piston moves to 10°CA before compression top dead center, and the combustible mixture formed by the ignition fuel and air is ignited; (4) The throttle valve position sensor (12) measures the opening degree signal of the throttle valve (11), and the engine ECU (14) performs closed-loop correction on the throttle valve opening degree ψ according to the opening degree signal of the throttle valve (11), so that the throttle valve The opening of (11) conforms to the relationship between the throttle opening ψ and the throttle opening Φ; The engine ECU (14) performs closed-loop correction on the fuel injection pulse width of the spark-ignited fuel injector (10) according to the oxygen content, so that the excess air ratio λ of the mixture is the required value of the excess air ratio λ under the condition of small load; (3) The dual-fuel engine is under the condition of 30%-100% load (1) The throttle opening Φ is increased from 30% to 100%; (2) Determine the engine speed n; (3) The throttle valve opening ψ is quickly adjusted to fully open; (4) The spark plug (8) stops flashing; (5) Determine the value of the excess air coefficient λ of the mixer and the value of the substitution rate L under the current accelerator opening Φ and the engine speed n, and determine the ignition type according to the value of the excess air coefficient λ of the mixer and the value of the substitution rate L. Fuel injection quantity and compression ignition fuel injection quantity; (6) The engine ECU (14) performs closed-loop correction on the injection pulse width of the compression ignition fuel injector (7) and the ignition fuel injector (10). 2. The control method of a dual-fuel engine according to claim 1, wherein the injection pulse width of the compression-ignition fuel injector (7) and the ignition fuel injector (10) is performed. The closed-loop correction includes the following processes: The oxygen concentration in the exhaust pipe of the engine is detected, and the engine ECU (14) compares the detected oxygen concentration with the target range. If the oxygen concentration in the exhaust pipe is lower than the minimum value of the target range, the engine ECU (14) sends out a Control commands while reducing the injection pulse width of the compression ignition fuel injector (7) and the ignition fuel injector (10); If the oxygen concentration in the exhaust pipe is higher than the maximum value of the target range, the engine ECU (14) issues a control command and simultaneously increases the Injection pulse width; If the oxygen concentration in the exhaust pipe is within the target range, adjust the fuel injection pulse width of the compression ignition fuel injector (7) and the ignition fuel injector (10). When the knock signal arrives, the engine ECU (14) issues a control command to reduce the fuel injection pulse width of the ignition type fuel injector (10) and correspondingly increase the fuel injection pulse width of the compression ignition fuel injector (7), and Keep the excess air coefficient λ unchanged; if no knock signal is detected, the engine ECU (14) sends a control command to increase the injection pulse width of the ignition type fuel injector (10) and reduce the compression ignition type fuel injection The fuel injection pulse width of the fuel injector (7) is maintained, and the excess air coefficient λ remains unchanged. 3. A dual-fuel engine, comprising an engine, characterized in that the dual-fuel engine further comprises an ignition device and a throttle valve device, both of which are connected with the engine ECU (14); a spark plug (8) of the ignition device installed on the cylinder head of the engine; the throttle device is installed on the intake manifold of the engine; In the ignition device, when the dual-fuel engine is under cold start, warm-up or idle speed conditions, the spark plug (8) of the ignition device ignites when the piston moves to 5°CA before compression top dead center, igniting the ignition type fuel. Combustible mixture formed with air; when the dual-fuel engine is at idle speed -30% load, that is, under the condition of small load, the spark plug (8) ignites when the piston moves to 10°CA before compression top dead center. Combustible gas mixture formed by fuel and air; when the dual-fuel engine is under the working condition of 30%-100% load, the spark plug stops flashing; The throttle valve device is kept fully closed when the dual-fuel engine is in cold start, warm-up or idling conditions; and when the dual-fuel engine is in idle speed-30% load, that is, a small load condition, the throttle valve is opened. The degree ψ changes with the throttle opening degree Φ; when the dual-fuel engine is under 30%-100% load conditions, the throttle valve opening degree ψ is fully open; The throttle valve device comprises a throttle valve (11) and a throttle valve position sensor (12). The throttle valve (11) has a circular structure, and when the axis of the throttle valve (11) is consistent with the axis of the intake manifold , a gap is left between the edge of the throttle valve (11) and the intake manifold.