阅读说明：本技术 一种天然气发动机燃气品质自适应控制方法 (Self-adaptive control method for fuel gas quality of natural gas engine ) 是由 刘锡庆 郑群 周凯 孙万超 武震 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种天然气发动机燃气品质自适应控制方法,包括台架试验,预存参数表、燃气品质自适应、燃气品质自适应条件设置、燃气品质自适应的启动、参数信息对比、获得燃气品质自适应因子、获得修正参数及燃气品质自适应的持续性等步骤,通过电控单元ECU实时检测氧传感器的信息,分析后确定相应的燃气品质自适应因子,根据燃气品质自适应因子确定需要调整的燃气喷射量修正系数、空气需求量修正系数、火角修正度数和EGR修正率,并通过相应的执行部件作用于发动机上,消除因天然气品质发生变化对Lambda稳定性的影响,有利于发动机排放结果的稳定控制,性能的稳定性控制,最终提高整个系统运行的安全性。(The invention discloses a natural gas engine gas quality self-adaptive control method, which comprises the steps of bench test, pre-storing a parameter table, gas quality self-adaption condition setting, gas quality self-adaption starting, parameter information comparison, obtaining a gas quality self-adaption factor, obtaining a correction parameter, gas quality self-adaption continuity and the like, wherein the information of an oxygen sensor is detected in real time through an Electronic Control Unit (ECU), the corresponding gas quality self-adaption factor is determined after analysis, a gas injection quantity correction coefficient, an air demand quantity correction coefficient, a fire angle correction degree and an Exhaust Gas Recirculation (EGR) correction rate which need to be adjusted are determined according to the gas quality self-adaption factor, and the gas injection quantity correction coefficient, the air demand quantity correction coefficient, the fire angle correction degree and the EGR correction rate are acted on an engine through corresponding execution components, so that the influence of Lambda stability caused by the change of, finally, the safety of the whole system operation is improved.)

1. The self-adaptive control method for the fuel gas quality of the natural gas engine is completed under the coordination of an Electronic Control Unit (ECU) on the engine, and is characterized in that: comprises the following steps of (a) carrying out,

step one, bench test, pre-storing parameter table

The method comprises the following steps of implementing a bench test under the coordination of the electronic control unit ECU, presetting an oxygen sensor closed-loop control mode of an engine in the electronic control unit ECU, and detecting and judging whether an oxygen sensor works normally in real time by the electronic control unit ECU;

when the ECU detects and judges that the oxygen sensor is normal and the oxygen sensor enters a closed-loop control state, adjusting the running power of the engine to obtain closed-loop control coefficients of the oxygen sensor corresponding to each running power of the engine, converting each obtained closed-loop control coefficient into a corresponding gas quality adaptive factor in the ECU, and forming a gas quality adaptive factor table to be prestored in the ECU;

respectively adjusting the operation load of the engine according to each specific adaptive factor value in the gas quality adaptive factor table, acquiring a gas injection quantity correction coefficient table, an air demand quantity correction coefficient table, an ignition angle correction degree table and an EGR rate correction table which correspond to each adaptive factor value in each operation load state of the engine, and pre-storing the gas injection quantity correction coefficient table, the air demand quantity correction coefficient table, the ignition angle correction degree table and the EGR rate correction table in the electronic control unit ECU;

step two, setting of gas quality self-adaptive enabling conditions

A lower limit reference parameter and an upper limit reference parameter for judging sudden change of the gas storage tank are arranged in the electronic control unit ECU, and when the detection parameter of the gas storage tank is suddenly increased from being smaller than the lower limit reference parameter to being higher than the upper limit reference parameter, the self-adaptive enabling condition of the gas quality is met;

step three, gas quality self-adaptive condition setting

Setting a gas quality self-adaptive condition in the ECU, namely that the oxygen sensor is normal and enters a closed-loop control state and the load range Q of the running of the engine₁～Q₂The load change rate is less than K₁Engine speed range n₁～n₂And the speed of change of the rotational speed is less than n₃；

Step four, starting of gas quality self-adaption

In the running process of the engine, the ECU receives signals of the oxygen sensor and parameter information of the air storage tank in real time, judges whether the oxygen sensor is normal or not and whether the oxygen sensor enters a closed-loop control state or not according to the signals, further judges whether the parameter information of the air storage tank meets a sudden increase condition or not if the oxygen sensor is normal or not, keeps the current running state or runs according to an actual control instruction of a driver if the oxygen sensor does not meet the sudden increase condition, and executes the next step if the oxygen sensor meets the actual control instruction;

step five, parameter information comparison

In the running process of the engine, the electronic control unit ECU receives the current running load and the current rotating speed of the engine in real time, correspondingly compares the current running load and the current rotating speed with the conditions set in the third step, and when the comparison result shows that the current running load is in the load range Q₁～Q₂The current rotating speed is within the rotating speed range of n₁～n₂And the ECU calculates and obtains the load change rate K₂＜K₁Calculating to obtain the speed n of change of the rotation speed₄＜n₃If yes, executing the next step;

step six, obtaining a gas quality adaptive factor

Inquiring the gas quality adaptive factor table according to the closed-loop control coefficient of the current oxygen sensor to obtain a specific value of the corresponding gas quality adaptive factor;

step seven, obtaining correction parameters

The ECU automatically calls tables prestored in the first step according to the obtained gas quality adaptive factor and the current running load of the engine to determine a gas injection quantity correction coefficient, an air demand quantity correction coefficient, an ignition angle correction degree and an EGR rate correction, and controls corresponding execution components to act according to the determined coefficients to realize the adaptation of the gas quality of the engine;

step eight, continuity of gas quality self-adaption

And continuously using the gas quality self-adaptive factor obtained in the step six from the current driving cycle to the subsequent driving cycle until the next gas quality self-adaptive starting.

2. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 1, characterized in that: in the second step, the gas storage tank is a CNG tank, the parameter of the CNG tank is a pressure parameter, the parameter of the CNG tank detected by the electronic control unit ECU in real time is a pressure, and when the pressure in the CNG tank is lower than the lower limit reference pressure P₁Suddenly increased above an upper limit reference pressure P₂And if so, the electronic control unit ECU judges that the parameters in the CNG tank change suddenly, namely, the parameters meet the gas quality self-adaptive enabling conditions, and executes a step III, wherein the lower limit reference pressure P₁The upper limit reference pressure P₂Respectively are set values.

3. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 2, characterized in that: the lower limit reference pressure P₁Set to 2Mp, the upper limit reference pressure P₂The value was set to 15 Mp.

4. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 1, characterized in that: in the second step, the gas storage tank is an LNG tank, the parameter of the LNG tank is a liquid level parameter, the parameter of the LNG tank detected in real time by the electronic control unit ECU is a liquid level, and when the liquid level in the LNG tank is lower than the lower limit reference liquid level L₁Suddenly increased to be higher than the upper limit reference liquid level L₂And if so, the ECU judges that the parameters in the LNG tank are suddenly changed, namely the parameters meet the gas quality self-adaptive enabling conditions, and executes the step III, wherein the lower limit reference liquid level L₁The upper limit reference liquid level L₂Respectively are set values.

5. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 4, characterized in that: the lower limit reference liquid level L₁Set to 20% of the total liquid level of the LNG tank, the upper limit reference level L₂Set to 80% of the total LNG tank level.

6. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 1, characterized in that: load range Q of engine operation in the third step₁～Q₂Set to 20-60%, load change rate K₁The setting is 2%; engine speed range n₁～n₂Setting the speed to 800-1400 rpm, the speed of rotation change n₃Set at 50 rpm.

7. The adaptive control method for the gas quality of the natural gas engine as claimed in claim 1, characterized in that: the range of the air injection quantity correction coefficient in the gas injection quantity correction coefficient table is 0.8-1.2, the range of the air demand quantity correction coefficient in the air demand quantity correction coefficient table is 0.9-1.1, the range of the ignition angle correction degree in the ignition angle correction degree table is-3 degrees, and the EGR rate correction range in the EGR rate correction table is-1%.

Technical Field

The invention relates to the technical field of natural gas engine operation control, in particular to a natural gas engine fuel gas quality self-adaptive control method.

Background

The natural gas used by the engine in the current market has larger composition difference, because the natural gas with various qualities is mixed with inert gases such as ethane, propane, nitrogen and the like with a certain proportion, and the content of the inert gases in the natural gas with different qualities is also different. The calorific value of ethane, propane and other components is high, and the addition of the ethane, the propane and other components changes the calorific value of pure natural gas during combustion, so that the combustion speed of gas mixed with oxygen is changed, the actual EGR rate of the engine gas mixture is influenced, the actual EGR rate is larger than the EGR rate calculated by an Engine Control Unit (ECU), and the fire risk of the engine is increased. In addition, the control accuracy of the Lambda of the engine is influenced by the difference of the natural gas components, the control accuracy of the Lambda is adjusted by closed-loop control of an oxygen sensor in the traditional method, but the control accuracy of the Lambda of the engine cannot be ensured by the closed-loop control of the oxygen sensor due to the influence of various inert gases, and the operating state of the engine is influenced finally.

In addition, the difference of natural gas components also affects the consistency of the net power of the engine, the combustion in a cylinder of the engine is changed, the net power of the engine cannot meet the requirements of relevant regulations, and in addition, the emission and the power set when the currently used engine leaves a factory are consistent, after mixed gas with inconsistent combustion speed is used, the consistency of the emission and the power of the engine is damaged, the generation of the engine knock phenomenon is easily aggravated, and in severe cases, the engine is damaged even because of the knock phenomenon. For the above reasons, it is necessary to develop a technical solution capable of automatically adjusting the operation of the engine according to the quality of the combustion gas, so as to eliminate the above drawbacks.

Disclosure of Invention

The invention aims to provide a natural gas engine fuel gas quality self-adaptive control method which can effectively control the discharged pollutants and ensure the net power consistency and the operation safety of the engine.

In order to solve the technical problems, the technical scheme of the invention is as follows: a self-adaptive control method for the quality of fuel gas of natural gas engine is completed under the cooperation of an Electronic Control Unit (ECU) on the engine and comprises the following steps,

step one, bench test, pre-storing parameter table

The method comprises the following steps of implementing a bench test under the coordination of the electronic control unit ECU, presetting an oxygen sensor closed-loop control mode of an engine in the electronic control unit ECU, and detecting and judging whether an oxygen sensor works normally in real time by the electronic control unit ECU;

when the ECU detects and judges that the oxygen sensor is normal and the oxygen sensor enters a closed-loop control state, adjusting the running power of the engine to obtain closed-loop control coefficients of the oxygen sensor corresponding to each running power of the engine, converting each obtained closed-loop control coefficient into a corresponding gas quality adaptive factor in the ECU, and forming a gas quality adaptive factor table to be prestored in the ECU;

respectively adjusting the operation load of the engine according to each specific adaptive factor value in the gas quality adaptive factor table, acquiring a gas injection quantity correction coefficient table, an air demand quantity correction coefficient table, an ignition angle correction degree table and an EGR rate correction table which correspond to each adaptive factor value in each operation load state of the engine, and pre-storing the gas injection quantity correction coefficient table, the air demand quantity correction coefficient table, the ignition angle correction degree table and the EGR rate correction table in the electronic control unit ECU;

step two, setting of gas quality self-adaptive enabling conditions

A lower limit reference parameter and an upper limit reference parameter for judging sudden change of the gas storage tank are arranged in the electronic control unit ECU, and when the detection parameter of the gas storage tank is suddenly increased from being smaller than the lower limit reference parameter to being higher than the upper limit reference parameter, the self-adaptive enabling condition of the gas quality is met;

step three, gas quality self-adaptive condition setting

Setting a gas quality self-adaptive condition in the ECU, namely that the oxygen sensor is normal and enters a closed-loop control state and the load range Q of the running of the engine₁～Q₂The load change rate is less than K₁Engine speed range n₁～n₂And the speed of change of the rotational speed is less than n₃；

Step four, starting of gas quality self-adaption

In the running process of the engine, the ECU receives signals of the oxygen sensor and parameter information of the air storage tank in real time, judges whether the oxygen sensor is normal or not and whether the oxygen sensor enters a closed-loop control state or not according to the signals, further judges whether the parameter information of the air storage tank meets a sudden increase condition or not if the oxygen sensor is normal or not, keeps the current running state or runs according to an actual control instruction of a driver if the oxygen sensor does not meet the sudden increase condition, and executes the next step if the oxygen sensor meets the actual control instruction;

step five, parameter information comparison

In the running process of the engine, the electronic control unit ECU receives the current running load and the current rotating speed of the engine in real time, correspondingly compares the current running load and the current rotating speed with the conditions set in the third step, and when the comparison result shows that the current running load is in the load range Q₁～Q₂The current rotating speed is within the rotating speed range of n₁～n₂And the ECU calculates and obtains the load change rate K₂＜K₁Calculating to obtain the speed n of change of the rotation speed₄＜n₃If yes, executing the next step;

step six, obtaining a gas quality adaptive factor

Inquiring the gas quality adaptive factor table according to the closed-loop control coefficient of the current oxygen sensor to obtain a specific value of the corresponding gas quality adaptive factor;

step seven, obtaining correction parameters

The ECU automatically calls tables prestored in the first step according to the obtained gas quality adaptive factor and the current running load of the engine to determine a gas injection quantity correction coefficient, an air demand quantity correction coefficient, an ignition angle correction degree and an EGR rate correction, and controls corresponding execution components to act according to the determined coefficients to realize the adaptation of the gas quality of the engine;

step eight, continuity of gas quality self-adaption

And continuously using the gas quality self-adaptive factor obtained in the step six from the current driving cycle to the subsequent driving cycle until the next gas quality self-adaptive starting.

As a preferable technical scheme, in the second step, the gas storage tank is a CNG tank, the parameter of the CNG tank is a pressure parameter, the parameter of the CNG tank detected by the electronic control unit ECU in real time is a pressure, and when the pressure in the CNG tank is lower than the lower limit reference pressure P₁Suddenly increased above an upper limit reference pressure P₂And if so, the electronic control unit ECU judges that the parameters in the CNG tank change suddenly, namely, the parameters meet the gas quality self-adaptive enabling conditions, and executes a step III, wherein the lower limit reference pressure P₁The upper limit reference pressure P₂Respectively are set values.

Preferably, the lower reference pressure P is set to be lower than the lower reference pressure P₁Set to 2Mp, the upper limit reference pressure P₂The value was set to 15 Mp.

As a preferred technical scheme, in the second step, the gas storage tank is an LNG tank, the parameter of the LNG tank is a liquid level parameter, the parameter of the LNG tank detected by the electronic control unit ECU in real time is a liquid level, and when the liquid level in the LNG tank is lower than a lower limit reference liquid level L₁Suddenly increased to be higher than the upper limit reference liquid level L₂And if so, the ECU judges that the parameters in the LNG tank are suddenly changed, namely the parameters meet the gas quality self-adaptive enabling conditions, and executes the step III, wherein the lower limit reference liquid level L₁The upper limit reference liquid level L₂Respectively are set values.

Preferably, the lower reference level L is₁Set to 20% of the total liquid level of the LNG tank, the upper limit reference level L₂Set to 80% of the total LNG tank level.

As a preferred technical solution, it is proposed that,load range Q of engine operation in the third step₁～Q₂Set to 20-60%, load change rate K₁The setting is 2%; engine speed range n₁～n₂Setting the speed to 800-1400 rpm, the speed of rotation change n₃Set at 50 rpm.

In an improvement of the above aspect, the range of the gas injection amount correction coefficient in the gas injection amount correction coefficient table is 0.8 to 1.2, the range of the air demand amount correction coefficient in the air demand amount correction coefficient table is 0.9 to 1.1, the range of the ignition angle correction degree in the ignition angle correction degree table is-3 to 3 °, and the EGR rate correction range in the EGR rate correction table is-1 to 1%.

Due to the adoption of the technical scheme, the invention has the following technical effects: the method comprises the steps of detecting information of an oxygen sensor in real time through an Electronic Control Unit (ECU), determining a corresponding gas quality adaptive factor after analysis, determining a gas injection quantity correction coefficient, an air demand quantity correction coefficient, a fire angle correction degree and an EGR correction rate which need to be adjusted according to the gas quality adaptive factor, and acting on an engine through a corresponding execution component, so that the influence on Lambda stability due to the change of natural gas quality is eliminated, the stable control of an engine emission result and the stability control of performance are facilitated, the influence on the safe operation of the engine due to the change of the natural gas quality is reduced, the knocking risk and the fire catching risk are reduced, and the operation safety of the whole system is finally improved.

Drawings

The drawings are only for purposes of illustrating and explaining the present invention and are not to be construed as limiting the scope of the present invention. Wherein:

FIG. 1 is a flow chart of the operation of an embodiment of the present invention.

Detailed Description

The invention is further illustrated below with reference to the figures and examples. In the following detailed description, certain exemplary embodiments of the present invention are described by way of illustration only. Needless to say, a person skilled in the art realizes that the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are illustrative in nature and not intended to limit the scope of the claims.

As shown in fig. 1, in the control method described in this embodiment, the ECU needs to cooperate with various execution components on the engine, and specifically includes the following steps:

step one, bench test, pre-storing parameter table

The method comprises the steps that a bench test is implemented under the cooperation of the electronic control unit ECU, an oxygen sensor closed-loop control mode of an engine is preset in the electronic control unit ECU, and the electronic control unit ECU detects and judges whether the oxygen sensor works normally or not in real time.

When the ECU detects and judges that the oxygen sensor is normal and the oxygen sensor enters a closed-loop control state, the running power of the engine is adjusted to obtain the closed-loop control coefficient of the oxygen sensor corresponding to each running power of the engine, each obtained closed-loop control coefficient is converted into a corresponding gas quality adaptive factor in the ECU, and a gas quality adaptive factor table is formed and is prestored in the ECU. The specific process or manner of converting the closed-loop control coefficient into the corresponding gas quality adaptive factor by using the ECU in this step is well known to those skilled in the art and will not be described in detail herein.

And respectively adjusting the operation load of the engine according to each specific adaptive factor value in the gas quality adaptive factor table, and acquiring a gas injection quantity correction coefficient table, an air demand quantity correction coefficient table, an ignition angle correction degree table and an EGR rate correction table which correspond to each adaptive factor value in each operation load state of the engine, wherein the gas injection quantity correction coefficient table, the air demand quantity correction coefficient table, the ignition angle correction degree table and the EGR rate correction table are prestored in the electronic control unit ECU so as to be convenient for use in the subsequent gas quality adaptive step.

In the present embodiment, the range of the air injection amount correction coefficient in the gas injection amount correction coefficient table is 0.8 to 1.2, the range of the air demand amount correction coefficient in the air demand amount correction coefficient table is 0.9 to 1.1, the range of the ignition angle correction degree in the ignition angle correction degree table is-3 to 3 °, and the EGR rate correction range in the EGR rate correction table is-1 to 1%.

Step two, setting of gas quality self-adaptive enabling conditions

And when the detection parameter of the gas storage tank is suddenly increased from being smaller than the lower limit reference parameter to being higher than the upper limit reference parameter, the ECU judges that the gas storage tank of the engine completes one gas filling task, namely, the gas quality self-adaptive enabling condition is met, namely, the enabling condition is a starting allowing condition.

In the second step, the gas storage tank may be a CNG tank or an LNG tank, but the parameters detected by the CNG tank and the LNG tank are different. When the gas storage tank is a CNG tank, the detected CNG tank parameter is a pressure parameter, the CNG tank parameter detected by the electronic control unit ECU in real time is a pressure, and the pressure in the CNG tank is controlled by the pressure lower than the lower limit reference pressure P₁Suddenly increased above an upper limit reference pressure P₂And if so, the electronic control unit ECU judges that the parameters in the CNG tank change suddenly, namely, the parameters meet the gas quality self-adaptive enabling conditions, and executes a step III, wherein the lower limit reference pressure P₁The upper limit reference pressure P₂Respectively are set values. In the present embodiment, the lower limit reference pressure P₁May be set to 2Mp, the upper limit reference pressure P₂Can be set to 15 Mp. Namely, when the electronic control unit ECU detects that the pressure in the CNG tank suddenly increases from lower than 2Mp to higher than 15Mp, the CNG tank is judged to complete a gas filling task, and a new gas quality adaptive factor needs to be determined with the help of an oxygen sensor closed-loop control coefficient, so that a gas injection quantity correction coefficient, an air demand quantity correction coefficient, an ignition angle correction degree and a corrected EGR rate are reselected, corresponding execution components of the engine are adjusted according to the quality of natural gas, and the purpose of ensuring the running state of the engine to be stable is achieved.

When the gas storage tank is an LNG tank, the parameter of the LNG tank is a liquid level parameter, the parameter of the LNG tank detected by the electronic control unit ECU in real time is a liquid level, and the liquid level in the LNG tank is determined by the reference liquid level L lower than the lower limit₁Suddenly increased to be higher than the upper limit reference liquid level L₂And if so, the ECU judges that the parameters in the LNG tank are suddenly changed, namely the parameters meet the gas quality self-adaptive enabling conditions, and executes the step III, wherein the lower limit reference liquid level L₁The upper limit reference liquid level L₂Respectively are set values. The lower limit reference liquid level L₁May be set to 20% of the total level of the LNG tank, the upper reference level L₂May be set to 80% of the total LNG tank level. Namely, when the electronic control unit ECU detects that the liquid level in the LNG tank is suddenly increased from 20% lower than the total liquid level of the LNG tank to 80% higher than the total liquid level of the LNG tank, it determines that the LNG tank completes a gas filling task, and determines a new gas quality adaptive factor with the help of an oxygen sensor closed-loop control coefficient, so as to reselect a gas injection amount correction coefficient, an air demand correction coefficient, an ignition angle correction degree and a corrected EGR rate, thereby adjusting corresponding execution components of an engine according to the quality of natural gas, and achieving the purpose of ensuring the running state of the engine to be stable.

Step three, gas quality self-adaptive condition setting

Setting a gas quality self-adaptive condition in the ECU, namely that the oxygen sensor is normal and enters a closed-loop control state and the load range Q of the running of the engine₁～Q₂The load change rate is less than K₁Engine speed range n₁～n₂And the speed of change of the rotational speed is less than n₃. E.g. load range Q for running the engine₁～Q₂Set to 20-60%, load change rate K₁The setting is 2%; engine speed range n₁～n₂Setting the speed to 800-1400 rpm, the speed of rotation change n₃The rotational speed was set at 50rpm, and the above data may be adjusted as appropriate.

Step four, starting of gas quality self-adaption

In the running process of the engine, the ECU receives signals of the oxygen sensor and parameter information of the air storage tank in real time, judges whether the oxygen sensor is normal or not and whether the oxygen sensor enters a closed-loop control state or not according to the signals, further judges whether the parameter information of the air storage tank meets a sudden increase condition or not if the oxygen sensor is normal or not, keeps the current running state or runs according to an actual control instruction of a driver if the oxygen sensor does not meet the sudden increase condition, and executes the next step if the oxygen sensor meets the actual control instruction.

Step five, parameter information comparison

In the running process of the engine, the electronic control unit ECU receives the current running load and the current rotating speed of the engine in real time, correspondingly compares the current running load and the current rotating speed with the conditions set in the third step, and when the comparison result shows that the current running load is in the load range Q₁～Q₂The current rotating speed is within the rotating speed range of n₁～n₂And the ECU calculates and obtains the load change rate K₂＜K₁Calculating to obtain the speed n of change of the rotation speed₄＜n₃When the oxygen sensor of the engine works normally and is in a closed-loop control state, the load and the rotating speed of the engine meet the conditions, and then the gas quality self-adaptation can be started.

Step six, obtaining a gas quality adaptive factor

And inquiring the gas quality adaptive factor table according to the closed-loop control coefficient of the current oxygen sensor to obtain the specific value of the corresponding gas quality adaptive factor.

Step seven, obtaining correction parameters

And the ECU automatically calls tables prestored in the first step according to the obtained gas quality adaptive factor and the current running load of the engine to determine a gas injection quantity correction coefficient, an air demand quantity correction coefficient, an ignition angle correction degree and an EGR rate correction, and controls corresponding execution components to act according to the determined coefficients to realize the adaptation of the gas quality of the engine.

Correcting the gas injection amount: after the gas storage tank is filled with gas, natural gas components comprise gas components such as ethane, propane and nitrogen, after the quality of the gas is changed, the previously calculated gas injection amount cannot meet the Lambda closed loop responsiveness in real time, a certain time delay exists in the Lambda closed loop of the engine, so that the difference of emission result compliance occurs, in order to make up for the difference, the gas injection amount needs to be corrected in advance through the gas quality adaptive factor obtained in the step six, the rapid response of gas supply is ensured, the good stability of the Lambda is maintained, and the emission of the engine is favorable for meeting relevant regulations. The control process is that a correction coefficient (the coefficient range is 0.8-1.2) is obtained according to the gas quality adaptive factor and the current engine operation load, and the coefficient is used for calculating the gas demand, so that the gas supply is accurate and timely, the gas demand is specifically calculated to be preset in the electronic control unit ECU, the method is a known technical means, and detailed description is omitted.

Air demand correction: after the quality of the natural gas changes, the combustion stability of the engine is affected, the combustion rate of mixed gas of the engine is changed, and further the net power of the engine changes, so that the air input of the engine needs to be corrected according to the change factor of the quality of the gas, and the consistency of the net power of the engine is ensured. When the gas quality factor is increased, it is indicated that more inert gas is contained in the gas, so that the combustion of the engine is deteriorated, the power of the engine is reduced, and at this time, a correction coefficient Mfac (0.9-1.1) needs to be obtained according to the gas quality adaptive factor and the current operation load of the engine, so as to increase the required intake pressure of the engine, so as to achieve the purpose of increasing the intake flow, further ensure the power consistency of the engine, and meet the national regulation requirements, and vice versa.

And (3) correcting the ignition angle: after the natural gas quality changes, the combustion detonation tendency of the engine is strengthened, so that the ignition angle of the engine needs to be reduced, the detonation of the engine needs to be prevented in advance, the safety of the engine needs to be protected, and the ignition angle is not corrected when the detonation of the engine is detected. The ignition angle range is corrected (-3 degrees) according to the variation factor of the gas quality and the current rotating speed of the engine, when the variation factor of the gas quality is increased, the ignition advance angle is actively reduced through the correction coefficient, and the engine knock is prevented in advance to protect the safe operation of the engine; when the variation factor of the gas quality is reduced, the ignition advance angle is actively increased through the correction coefficient so as to improve the economy of the engine.

And (3) EGR rate correction: after the quality of the natural gas is changed, the heat value of the fuel gas is changed, and the inert gas such as nitrogen also changes the actual EGR rate of the mixed gas, so that the actual EGR rate of the engine is larger than the actual calculated EGR rate, the fire risk of the engine is increased, and therefore the required value of the EGR rate needs to be corrected to prevent the fire phenomenon of the engine and avoid emission deterioration, catalyst damage and the like. The method comprises the steps of actively reducing an EGR rate requirement value through a correction coefficient when a gas quality adaptive coefficient is increased to prevent an engine fire phenomenon, specifically, indicating that high-calorific-value gas is mixed in the gas when a variation factor of the gas quality is reduced, and actively increasing the EGR rate requirement value through the correction coefficient to prevent the engine knock phenomenon to achieve the purpose of actively adjusting and enabling the engine to safely operate.

Step eight, continuity of gas quality self-adaption

In this embodiment, the gas quality adaptive factor obtained in step six is continuously used from the current driving cycle to the subsequent driving cycle until the next gas quality adaptive start.

The invention detects the information of the oxygen sensor in real time through the ECU, determines the corresponding gas quality adaptive factor after analysis, determines the gas injection quantity correction coefficient, the air demand correction coefficient, the fire angle correction degree and the EGR correction rate which need to be adjusted according to the gas quality adaptive factor, and acts on the engine through the corresponding execution component, thereby eliminating the influence on the Lambda stability caused by the change of the natural gas quality, being beneficial to the stable control of the engine emission result and the stable control of the performance, reducing the influence on the safe operation of the engine caused by the change of the natural gas quality, reducing the detonation risk and the fire risk, and finally improving the operation safety of the whole system.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.