1. A method for controlling an adaptive gas composition for a gas engine, comprising the steps of:

acquiring gas quality component information of gas behind an engine gas rail, and predicting the maximum knock intensity through a knock intensity prediction model;

judging whether the engine is in a steady state working condition, if not, returning to the previous step; if yes, transmitting the gas quality component information to an ECU (electronic control Unit);

correcting the maximum knock intensity by using the ECU according to a knock MAP, and adjusting a knock threshold value in real time based on a correction result;

acquiring engine combustion pressure data by using the ECU, calculating to obtain initial signal energy EISE and initial signal energy KISE, and dividing the initial signal energy KISE and the initial signal energy EISE to calculate to obtain a signal energy factor SEF;

acquiring the pressure of a premixed combustion stage and the pressure of a main combustion stage by utilizing the ECU control unit and calculating to obtain the peak pressure SD of the premixed combustion stage_bp,max,pcpAnd main combustion phase peak pressure SD_bp,max,mcpThe main combustion phase peak pressure SD_bp,max,mcpWith the premixed combustion phase peak pressure SD_bp,max,pcpPerforming a phase division calculation to obtain a peak pressure coefficient PPF;

multiplying the signal energy factor SEF by the peak pressure coefficient PPF to obtain a knock indication level indication IKIL;

judging whether the engine knocks or not based on the knock indication level indication IKIL, and if the knock indication level indication IKIL is smaller than 1, judging that the engine does not knock; if the knock indication level index IKIL is more than or equal to 1, judging that the engine knocks, and entering the next step;

demarcating a plurality of knock levels based on the knock indication level indication IKIL and the knock threshold value;

and respectively formulating knock correction modes which are in one-to-one correspondence with the plurality of knock levels.

2. The method of claim 1, wherein the step of obtaining post-engine gas composition information comprises:

various components and corresponding concentration contents of the fuel gas are detected by utilizing the gas component sensor.

3. The method of claim 1, wherein the step of determining whether the engine is in a steady state condition comprises:

acquiring the rotating speed change rate and/or the load change rate of the engine, judging whether the rotating speed change rate and/or the load change rate exceed a set value, and if so, judging that the engine is in an unsteady state working condition; if not, the engine is determined to be in a steady state operating condition.

4. The method of controlling an adaptive gas composition for a gas engine as recited in claim 1, wherein the knock threshold comprises a first knock threshold and a second knock threshold, the second knock threshold being greater than the first knock threshold.

5. The method of controlling an adaptive gas composition for a gas engine according to claim 4, wherein said step of dividing a plurality of knock levels based on said knock indication level indication IKIL and said knock threshold value comprises:

when the knock indication level indication IKIL is less than the first knock threshold, corresponding to light knock;

when the knock indication level indication IKIL is greater than or equal to the first knock threshold and less than the second knock threshold, corresponding to moderate knock;

when the knock indication level indication IKIL is greater than or equal to the second knock threshold, a corresponding high knock is performed.

6. The control method of adaptive gas composition for a gas engine according to claim 5, wherein said step of individually making knock correction patterns corresponding to a plurality of said knock levels in one-to-one correspondence includes:

formulating a primary knock correction mode corresponding to the light knock, wherein the primary knock correction mode is an air-fuel ratio correction mode;

formulating a second-level knock correction mode corresponding to the moderate knock, wherein the second-level knock correction mode is a synergistic correction mode of air-fuel ratio correction and EGR correction;

and formulating a three-level knock correction mode corresponding to the high knock, wherein the three-level knock correction mode is a synergistic correction mode of air-fuel ratio correction, EGR correction and ignition advance angle correction.

7. The method of claim 1, wherein said step of obtaining engine combustion pressure data and calculating an initial signal energy EISE and a knock initial signal energy KISE using said ECU control unit comprises:

the initial signal energy EISE is obtained by calculation according to the following equation (1),

（1）；

calculating and obtaining knock initial energy KISE according to the following equation (2),

（2）；

where SOC is the initial combustion time, p is the engine combustion pressure, φ is the combustion process, φ is varied by the heat release rateTo judge.

8. The method for controlling adaptive gas composition for gas engine according to claim 1, wherein the premixed combustion phase peak pressure SD is obtained by obtaining the premixed combustion phase pressure and the main combustion phase pressure by the ECU control unit and calculating_bp,max,pcpAnd main combustion phase peak pressure SD_bp,max,mcpComprises the following steps:

calculating premixed combustion phase peak pressure data SD according to the following formula (3)_bp,max,pcp，

（3）；

Calculating main combustion phase peak pressure data SD according to the following equation (4)_bp,max,mcp，

（4）；

Wherein SOC is an initial combustion time, P_pcpFor premixing combustion stage pressure, P_mcpIs the pressure of the main combustion stage, phi is the combustion process, phi is changed by the heat release rateTo judge.

9. The method of claim 1, wherein the step of individually setting knock correction modes corresponding to the knock levels further comprises the steps of:

and correcting the knock of the engine according to the knock correction mode, and training the knock intensity prediction model based on the knock correction result.

10. The control method for adaptive gas composition for gas engines according to any one of claims 1 to 9, applied to natural gas engines.

Background

Natural gas engines are widely used due to the advantages of clean combustion and high heating value. Natural gas is complex in composition, and the main component is saturated hydrocarbon mainly containing methane, and simultaneously contains unequal amounts of ethane, propane, butane and a small amount of non-hydrocarbon gas. Due to the difference of natural gas production places and the difference of extraction processes in the production process, the natural gas composition difference in the market is large, and the physicochemical characteristics of the natural gas, such as quality, density, heat value and the like, are further influenced. Due to the lack of uniform standards, the quality of the natural gas on the market is uneven, and the gas quality and the composition of the natural gas in different areas are greatly different. This affects not only the dynamics of the natural gas engine, but also engine ignition, flame propagation, and combustion heat release. When the content of alkanes (such as propane) with higher activity in natural gas is higher, abnormal combustion phenomena such as engine knocking and the like can be caused, so that the power of the engine is reduced, the oil consumption is increased, and the emission is deteriorated. In the worst case, knocking, engine flameout and damage to mechanical parts of the engine can be caused, and the service life of the engine is shortened.

The traditional natural gas engine knock detection and suppression means mainly comprise: the knock sensor is used for identifying a knock signal, the detected knock signal is sent to an ECU of the engine, the ECU processes the knock signal and outputs a control signal after receiving the knock signal, the control signal is transmitted to the ignition module, and the ignition module delays ignition to inhibit knocking. However, because the natural gas engine has the particularity of slow flame propagation speed, severe afterburning and the like, the power performance and the emission performance of the natural gas engine are deteriorated due to single ignition delay, and the self-adaptability of the engine is poor.

In order to ensure efficient combustion of natural gas with different components and inhibit engine knocking, the key is to improve the self-adaptive capacity of the actual natural gas engine and ensure that large combustion performance difference cannot be caused when the component difference of the natural gas is large.

At present, the problem to be solved urgently is to ensure that natural gas with different components is reasonably and efficiently combusted in an engine cylinder and engine knocking is inhibited. The key point for solving the detonation problem of the natural gas with different components in the combustion of the engine is to improve the self-adaptive capacity of the engine, so that the natural gas with larger component difference can not have larger performance difference when being combusted in a cylinder, thereby avoiding the detonation and protecting the engine from being damaged.

Therefore, how to improve the adaptive capacity of the gas engine is a technical problem that needs to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a method for controlling adaptive gas components for a gas engine, which can enhance the adaptive capability of the gas engine, so that gas with large component difference can be reasonably and efficiently combusted in an engine cylinder, and strong knocking is avoided.

In order to achieve the above object, the present invention provides the following technical solutions.

A method for controlling an adaptive gas composition for a gas engine, comprising the steps of:

acquiring gas quality component information of gas behind an engine gas rail, and predicting the maximum knock intensity through a knock intensity prediction model;

judging whether the engine is in a steady state working condition, if not, returning to the previous step; if yes, transmitting the gas quality component information to an ECU (electronic control Unit);

correcting the maximum knock intensity by using the ECU according to a knock MAP, and adjusting a knock threshold value in real time based on a correction result;

acquiring engine combustion pressure data by using the ECU, calculating to obtain initial signal energy EISE and initial signal energy KISE, and dividing the initial signal energy KISE and the initial signal energy EISE to calculate to obtain a signal energy factor SEF;

acquiring the pressure of a premixed combustion stage and the pressure of a main combustion stage by utilizing the ECU control unit and calculating to obtain the peak pressure SD of the premixed combustion stage_bp,max,pcpAnd main combustion phase peak pressure SD_bp,max,mcpThe main combustion phase peak pressure SD_bp,max,mcpWith the premixed combustion phase peak pressure SD_bp,max,pcpPerforming a phase division calculation to obtain a peak pressure coefficient PPF;

multiplying the signal energy factor SEF by the peak pressure coefficient PPF to obtain a knock indication level indication IKIL;

judging whether the engine knocks or not based on the knock indication level indication IKIL, and if the knock indication level indication IKIL is smaller than 1, judging that the engine does not knock; if the knock indication level index IKIL is more than or equal to 1, judging that the engine knocks, and entering the next step;

demarcating a plurality of knock levels based on the knock indication level indication IKIL and the knock threshold value;

and respectively formulating knock correction modes which are in one-to-one correspondence with the plurality of knock levels.

Preferably, the step of acquiring the gas quality component information after the engine air rail comprises:

various components and corresponding concentration contents of the fuel gas are detected by utilizing the gas component sensor.

Preferably, the step of determining whether the engine is in a steady-state operating condition comprises:

acquiring the rotating speed change rate and/or the load change rate of the engine, judging whether the rotating speed change rate and/or the load change rate exceed a set value, and if so, judging that the engine is in an unsteady state working condition; if not, the engine is determined to be in a steady state operating condition.

Preferably, the knock threshold includes a first knock threshold and a second knock threshold, the second knock threshold being greater than the first knock threshold.

Preferably, said step of dividing a plurality of knock levels based on said indication of knock indication level IKIL and said knock threshold value comprises:

when the knock indication level indication IKIL is less than the first knock threshold, corresponding to light knock;

when the knock indication level indication IKIL is greater than or equal to the first knock threshold and less than the second knock threshold, corresponding to moderate knock;

when the knock indication level indication IKIL is greater than or equal to the second knock threshold, a corresponding high knock is performed.

Preferably, the step of formulating knock correction manners corresponding to the plurality of knock levels one to one respectively includes:

formulating a primary knock correction mode corresponding to the light knock, wherein the primary knock correction mode is an air-fuel ratio correction mode;

formulating a second-level knock correction mode corresponding to the moderate knock, wherein the second-level knock correction mode is a synergistic correction mode of air-fuel ratio correction and EGR correction;

and formulating a three-level knock correction mode corresponding to the high knock, wherein the three-level knock correction mode is a synergistic correction mode of air-fuel ratio correction, EGR correction and ignition advance angle correction.

Preferably, the step of acquiring engine combustion pressure data and calculating an initial signal energy EISE and a knock initial signal energy KISE by using the ECU control unit comprises:

the initial signal energy EISE is obtained by calculation according to the following equation (1),

（1）；

calculating and obtaining knock initial energy KISE according to the following equation (2),

（2）；

where SOC is the initial combustion time, p is the engine combustion pressure, φ is the combustion process, φ is varied by the heat release rateTo judge.

Preferably, the ECU is used for acquiring the pressure of the premixed combustion stage and the pressure of the main combustion stage and calculating to obtain the peak pressure SD of the premixed combustion stage_bp,max,pcpAnd main combustion phase peak pressure SD_bp,max,mcpComprises the following steps:

calculating the premixed combustion phase according to the following equation (3)Bit peak pressure data SD_bp,max,pcp，

（3）；

Calculating main combustion phase peak pressure data SD according to the following equation (4)_bp,max,mcp，

（4）；

Wherein SOC is an initial combustion time, P_pcpFor premixing combustion stage pressure, P_mcpIs the pressure of the main combustion stage, phi is the combustion process;

phi through heat release rate changeTo judge.

Preferably, the step of formulating knock correction manners corresponding to the plurality of knock levels one to one is further followed by the steps of:

and correcting the knock of the engine according to the knock correction mode, and training the knock intensity prediction model based on the knock correction result.

Preferably, the control method provided by the invention is applied to a natural gas engine.

According to the technical scheme, the engine knock threshold value is directly obtained by performing reinforcement learning on the gas with different components, the knock indication level index is obtained based on the combustion pressure, so that whether the engine knocks or not and the knock level are judged, then, different knock correction modes are adopted to perform self-adaptive grading correction according to the divided knock levels, further, the knock is inhibited until the engine knocks disappear, and the self-adaptive capacity of the gas engine is improved. The control method breaks through a single identification mode of the knock sensor in the traditional technology, and meanwhile compared with a single correction mode of delaying the ignition advance angle, the control method has the advantages that the influence of graded correction on the performance of the engine is minimum, and the self-adaptability is greatly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a control flow diagram of a control method in an embodiment of the invention;

FIG. 2 is a graph comparing cylinder pressure with a prior art uncorrected for knock classification correction in an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a control flow chart of a control method in an embodiment of the invention.

In order to improve the self-adaptive capacity of the gas engine and enable the gas engine to adapt to gas with different producing areas or different components, the invention provides a control method of the self-adaptive gas components for the gas engine, which comprises the following steps:

(a) and acquiring gas quality component information of the gas behind the gas track of the engine, and predicting the maximum knock intensity through a knock intensity prediction model. Specifically, according to the scheme, a high-sensitivity gas composition sensor can be installed behind an engine gas rail, various components and corresponding concentration contents of gas are detected by the gas composition sensor, and then, information of the various components and the corresponding concentration contents of the gas is input into a pre-trained knock intensity prediction model, so that the maximum knock intensity corresponding to the current gas composition is obtained through prediction, wherein the knock intensity prediction model is a strengthened learning model and has the function of predicting the maximum knock intensity of the gas during combustion in the engine according to the various components and the corresponding concentration contents of the gas.

(b) Judging whether the engine is in a steady state working condition, if not, returning to the previous step; and if so, transmitting the gas quality component information to an ECU (electronic control Unit). It should be noted that the engine may relate to an unsteady state condition (a transient state condition) and a steady state condition during the working process, and may be determined by the engine speed and the load, specifically, the engine speed may be detected by a speed sensor, the load of the engine may be determined by detecting the opening degree by a throttle sensor, the speed change rate and/or the load change rate of the engine may be obtained, whether the speed change rate and/or the load change rate exceed a set value (for example, whether the speed change rate or the load change rate is greater than 5%) is determined, and if so, it is determined that the engine is in the unsteady state condition (i.e., the transient state condition), and the process returns to the previous step; if not, the engine is judged to be in a steady-state working condition, namely the gas in the engine cylinder is in steady-state combustion, and at the moment, the gas quality component information can be transmitted to the ECU. It should be noted that the present invention can also be implemented by a coefficient of cyclic variation COV_IMEPThe combustion stability of the engine can be judged, specifically, the in-cylinder pressure data collected by the cylinder pressure sensor can be transmitted to a combustion analyzer after being amplified by a charge amplifier, and a set program in the combustion analyzer can automatically calculate the cyclic variation coefficient COV_IMEPIf COV_IMEPAnd when the combustion temperature is less than or equal to 5 percent, the engine is in steady-state combustion, otherwise, the engine is in non-steady-state combustion.

(c) And correcting the maximum knock intensity by using the ECU according to a knock MAP, and adjusting a knock threshold value in real time based on the correction result. The knock threshold determined in this step is the knock threshold adapted to the current gas composition. The knock MAP is a reference MAP stored in advance in the ECU control unit, which is a correspondence relationship between the gas composition information and parameters such as the maximum knock intensity and the knock threshold.

It should be noted that, in this scheme, the ECU control unit may be used to determine one knock threshold or multiple knock thresholds, and the division of the knock intensity in the subsequent step may be divided into different knock levels according to the number of knock thresholds determined in this step, so that the harmful effect of the knock on the engine is large, and at the same time, in order to further simplify the control strategy for the knock, it is not recommended to determine too many knock thresholds in this step. Preferably, the knock threshold determined in this step includes a first knock threshold and a second knock threshold, the second knock threshold being greater than the first knock threshold, and the first knock threshold being greater than 1.

(d) And acquiring engine combustion pressure data by using the ECU, calculating to obtain initial signal energy EISE and initial signal energy KISE, and dividing the initial signal energy KISE and the initial signal energy EISE to calculate to obtain a signal energy factor SEF. In the step, combustion pressure data of the engine can be acquired through the cylinder pressure sensor, the charge amplifier and the combustion analyzer, and the combustion pressure data of the engine is transmitted to the ECU to be subjected to signal conversion and participate in calculation.

Specifically, the ECU control unit combines a reference MAP graph and calculates and obtains an initial signal energy EISE according to the following equation (1),

（1）；

then, the ECU control unit obtains knock initial energy KISE by calculating according to the following equation (2) in combination with the reference MAP,

（2）；

where SOC is the initial combustion time, p is the engine combustion pressure, φ is the combustion process, φ can be varied by the heat release rateJudging; the reference MAP here refers to a reference MAP stored in advance in the ECU control unit, which is a MAP of the correspondence relationship between engine operating parameters (e.g., engine speed, ignition timing, injection timing, etc.).

Then, the signal energy factor SEF ═ KISE ÷ EISE is calculated.

(e) Acquiring the pressure of the premixed combustion stage and the pressure of the main combustion stage by utilizing the ECU control unit and calculating to obtain the peak pressure SD of the premixed combustion phase_bp,max,pcpAnd main combustion phase peak pressure SD_bp,max,mcpThe main combustion phase peak pressure SD_bp,max,mcpWith the premixed combustion phase peak pressure SD_bp,max,pcpAnd (5) performing division calculation to obtain a peak pressure coefficient PPF.

Specifically, the step can acquire the pressure P of the premixed combustion stage of the engine through a cylinder pressure sensor, a charge amplifier and a combustion analyzer_pcpAnd main combustion stage pressure P_mcpAnd premixing combustion stage pressure P_pcpAnd main combustion stage pressure P_mcpAnd the signals are transmitted to an ECU control unit for signal conversion and participation in calculation.

Specifically, in this step, the premixed combustion phase peak pressure data SD is calculated according to the following equation (3)_bp,max,pcp，

（3）；

And calculates main combustion phase peak pressure data SD according to the following equation (4)_bp,max,mcp，

（4）；

Wherein SOC is an initial combustion time, P_pcpFor premixing combustion stage pressure, P_mcpIs the main combustion stage pressure;

phi is the combustion process and phi can be varied by the heat release rateTo judge.

Then, the peak pressure coefficient PPF is calculated as SD_bp,max,mcp÷SD_bp,max,pcp。

(f) And multiplying the signal energy factor SEF by the peak pressure coefficient PPF to obtain a knock indication level indication IKIL, namely, the IKIL is SEF multiplied by PPF.

(g) Judging whether the engine knocks or not based on the knock indication level indication number IKIL, if the knock indication level indication number IKIL is smaller than 1, judging that the engine does not knock, and at the moment, continuing normal operation of the engine; if the knock indication level index IKIL is more than or equal to 1, judging that the engine knocks, and entering the next step to carry out knock level division;

(h) and demarcating a plurality of knock levels based on the knock indication level indication IKIL and the knock threshold value. It should be noted that, the level division of the knock intensity in this step is divided into knock levels of different intensities according to the number of knock thresholds determined in the above step (c). For example, if a knock threshold is determined in step (c), then in this step, the knock indication level indication IKIL may be classified as light knock if it is less than the knock threshold, and highly knock if it is equal to or greater than the knock threshold. Preferably, in this embodiment, step (c) determines two knock thresholds, namely, a first knock threshold and a second knock threshold, and in this step, the knock intensity is divided into three knock levels, which are: light knock, medium knock, high knock.

Wherein when the knock indication level indication IKIL is greater than or equal to 1 and less than the first knock threshold value, light knock is corresponded;

when the knock indication level indication IKIL is greater than or equal to the first knock threshold and less than the second knock threshold, corresponding to moderate knock;

when the knock indication level indication IKIL is greater than or equal to the second knock threshold, a corresponding high knock is performed.

(i) And respectively formulating knock correction modes which are in one-to-one correspondence with the plurality of knock levels. In this step, three different knock correction modes are formulated for the three knock levels divided in the previous step, that is, the scheme can realize adaptive knock grading correction, and specifically, the step includes the following contents:

formulating a first-level knock correction mode corresponding to the light knock, wherein the first-level knock correction mode is an air-fuel ratio correction mode, and specifically, the air-fuel ratio correction mode is to reduce the fuel injection quantity while improving the air intake quantity so as to gradually increase the air-fuel ratio until the knock cycle is eliminated;

formulating a second-stage knock correction mode corresponding to the moderate knock, wherein the second-stage knock correction mode is a synergistic correction mode of air-fuel ratio correction and EGR correction, and specifically means that the air-fuel ratio is gradually increased by reducing the fuel injection amount while improving the air intake amount and EGR and inhibiting the occurrence of a knock cycle until the knock cycle is eliminated;

and formulating a three-level knock correction mode corresponding to the high knock, wherein the three-level knock correction mode is a synergistic correction mode of air-fuel ratio correction, EGR correction and ignition advance angle correction, specifically, the air-fuel ratio is gradually increased by reducing the fuel injection amount while improving the air intake amount and EGR, and meanwhile, the ignition advance angle is increased until the knock phenomenon is eliminated.

It should be noted that the cooperative modification in this step refers to performing related operations synchronously without differentiating priority order.

Preferably, the step of formulating knock correction manners corresponding to the plurality of knock levels one to one is further followed by the steps of:

(j) and correcting the knock of the engine according to the knock correction mode, and training the knock intensity prediction model based on the knock correction result. Specifically, the step (a) judges whether the maximum knock intensity predicted in the step (a) is accurate or not, and identifies whether the knock grading correction mode is effective or not, if the predicted maximum knock intensity is accurate and the knock grading correction mode has a good correction effect, the knock prediction and identification results can be output to the knock intensity prediction model for learning and storing, so that the knock control of the next working cycle of the engine can be better guided.

Preferably, the control method provided by the present invention can be applied to various gas engines, for example, hydrogen engines, ammonia engines, natural gas engines, methanol engines, biomass gas engines, and the like. Preferably, the control method is applied to a natural gas engine fueled by natural gas.

Referring to FIG. 2, FIG. 2 is a graph illustrating a comparison of cylinder pressure with a conventional uncorrected cylinder pressure for knock classification correction in an embodiment of the present invention. As can be seen from the graph 2, in the whole combustion period, the pressure of the cylinder before correction changes violently, and the cylinder pressure is suddenly increased due to knocking.

According to the technical scheme, the knock threshold value of the engine is directly obtained by performing reinforcement learning on the gas with different components, and the integrated knock indication level index is obtained based on the combustion pressure, so that whether the engine knocks or not is judged, the knock intensity is divided into different knock levels, then the divided knock levels are subjected to self-adaptive grading correction in different knock correction modes, the knock is further inhibited until the knock cycle of the engine is eliminated, and the self-adaptive capacity of the gas engine is improved. The control method provided by the invention breaks through the single recognition mode of the knock sensor in the traditional technology and creatively divides the knock level. Meanwhile, compared with the traditional single correction mode of delaying the advance angle of ignition, the invention adopts the step correction which has the minimum influence on the performance of the engine and greatly improves the self-adaptability.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.