CN117514495A - Combustion preheating method, device, medium and vehicle - Google Patents
Combustion preheating method, device, medium and vehicle Download PDFInfo
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- CN117514495A CN117514495A CN202311614152.6A CN202311614152A CN117514495A CN 117514495 A CN117514495 A CN 117514495A CN 202311614152 A CN202311614152 A CN 202311614152A CN 117514495 A CN117514495 A CN 117514495A
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 128
- 238000000034 method Methods 0.000 title claims abstract description 54
- 230000003197 catalytic effect Effects 0.000 claims abstract description 136
- 239000000446 fuel Substances 0.000 claims abstract description 56
- 238000006479 redox reaction Methods 0.000 claims abstract description 14
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 153
- 229910021529 ammonia Inorganic materials 0.000 claims description 67
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 53
- 239000001301 oxygen Substances 0.000 claims description 53
- 229910052760 oxygen Inorganic materials 0.000 claims description 53
- 239000003638 chemical reducing agent Substances 0.000 claims description 35
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 230000036284 oxygen consumption Effects 0.000 claims description 10
- 239000002912 waste gas Substances 0.000 claims description 8
- 238000004590 computer program Methods 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 description 40
- 239000007789 gas Substances 0.000 description 15
- 239000000126 substance Substances 0.000 description 13
- 238000010586 diagram Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 6
- 238000010531 catalytic reduction reaction Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000001960 triggered effect Effects 0.000 description 2
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
The invention discloses a combustion preheating method, a combustion preheating device, a combustion preheating medium and a vehicle, wherein the combustion preheating method comprises the following steps: when the engine is started in a cold mode, the engine is controlled to burn by adopting a theoretical air-fuel ratio, and the first actual temperature of a three-way catalytic converter connected to an exhaust pipeline of the engine is detected in real time; and if the first actual temperature reaches a first temperature threshold, controlling the engine to circularly switch between a rich combustion state and a lean combustion state so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
Description
Technical Field
The application relates to the field of tail gas treatment, in particular to a combustion preheating method, a combustion preheating device, a combustion preheating medium and a vehicle.
Background
Low-fuel-consumption, low-emission and low-cost engines are the next-generation development targets of various factories, engine combustion control is an important research project, and elimination of NOx exhaust gas generated when the engines are combusted is a main research direction of combustion control.
In combustion control of an engine, a TWC (Three-Way catalytic converter) and an SCR (Selective Catalytic Reduction, passive selective catalytic reducer) are generally connected to an exhaust pipe of the engine, and when the engine is combusted, ammonia gas generated in the TWC and NOx exhaust gas generated during combustion react chemically, so that the NOx exhaust gas is converted into harmless gas N2, and the emission of the engine is ensured to meet the regulation requirement. The PSCR mainly functions to store ammonia gas.
Because the TWC is at a low temperature when the engine is cold started, NOx exhaust cannot be converted. Therefore, how to control combustion for rapid warm-up of the TWC at cold engine start is a current challenge.
Disclosure of Invention
The invention provides a combustion preheating method, a device, a medium and a vehicle, wherein when an engine is started in a cold mode, a theoretical air-fuel ratio is adopted to control the engine to burn until a first actual temperature of a three-way catalytic converter reaches a first temperature threshold value, so that the three-way catalytic converter has oxygen storage capacity, then the engine is controlled to be switched between a rich combustion state and a lean combustion state in a circulating mode, oxidation-reduction reaction is generated in the three-way catalytic converter by triggering, self-preheating is carried out through heat generated by the oxidation-reduction reaction, so that the preheating speed is increased, and the purpose of quickly preheating the three-way catalytic converter is achieved.
In a first aspect of the invention, a combustion preheating method is disclosed, the method comprising:
when the engine is started in a cold mode, the engine is controlled to burn by adopting a theoretical air-fuel ratio, and the first actual temperature of a three-way catalytic converter connected to an exhaust pipeline of the engine is detected in real time;
and if the first actual temperature reaches a first temperature threshold, controlling the engine to circularly switch between a rich combustion state and a lean combustion state so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
Optionally, the controlling the engine to switch back and forth between the rich state and the lean state specifically includes:
detecting an actual oxygen storage amount in the three-way catalytic converter;
and determining a corresponding air excess coefficient according to the actual oxygen storage amount and the theoretical air-fuel ratio, and controlling the engine to circularly switch between a rich combustion state and a lean combustion state.
Optionally, the determining a corresponding air excess factor according to the actual oxygen storage amount and the theoretical air-fuel ratio, and controlling the engine to circularly switch between a rich combustion state and a lean combustion state specifically includes:
if the actual oxygen storage amount exceeds the upper limit of the set oxygen storage range, determining a first air excess factor based on the theoretical air-fuel ratio to control the engine to enter a rich state;
if the actual oxygen storage amount is lower than the lower limit of the set air storage range, determining a second air excess factor based on the theoretical air-fuel ratio to control the engine to burn and enter a lean combustion state; the first air excess factor is less than the second air excess factor;
and if the actual oxygen storage amount is within the set air storage range, maintaining the combustion state of the engine unchanged.
Optionally, the first air excess coefficient lambda 1 E (0.98,1), the second air excess coefficient lambda 2 ∈(1，1.02)。
Optionally, after the controlling the engine to cyclically switch between the rich state and the lean state, the method further includes:
if the first actual temperature reaches a second temperature threshold value, controlling the engine to enter a rich state; the second temperature threshold is greater than the first temperature threshold.
Optionally, if the first actual temperature reaches the second temperature threshold, controlling the engine to enter a rich state specifically includes:
detecting in real time a second actual temperature of a passive selective catalytic reducer connected to the three-way catalytic converter;
and if the second actual temperature reaches a third temperature threshold value, controlling the engine to enter a rich state.
Optionally, after the engine is controlled to enter the rich state, the method further includes:
detecting the actual oxygen consumption in the three-way catalytic converter in real time;
and when the actual oxygen consumption reaches a set oxygen consumption threshold, controlling the engine to enter a lean-burn state.
Optionally, after the engine is controlled to enter the rich state, the method further includes:
detecting the actual ammonia storage amount of the passive selective catalytic reducer in real time;
and controlling the engine to circularly switch between a rich combustion state and a lean combustion state according to the actual ammonia storage amount.
Optionally, the controlling the engine to circularly switch between the rich combustion state and the lean combustion state according to the actual ammonia storage amount specifically includes:
selecting a rich ratio model or a lean ratio model with reference to the actual ammonia storage amount; the rich ratio model is used for controlling the engine to be in a rich state so as to generate ammonia in the three-way catalytic converter and store the ammonia into the passive selective catalytic reducer; the lean burn ratio model is used for controlling the engine to be in a lean burn state, so that the ammonia gas and NOx waste gas generated by the engine are subjected to chemical reaction to be consumed;
and controlling the engine combustion by using the rich ratio model or the lean ratio model so that the actual ammonia storage amount is in a target yield range.
Optionally, the selecting a rich ratio model or a lean ratio model with reference to the actual ammonia storage amount specifically includes:
if the actual ammonia storage amount exceeds the upper limit of the target yield range, selecting the lean ratio model;
and if the actual ammonia storage amount is lower than the lower limit of the target yield range, selecting the rich ratio model.
Alternatively, the rich model is obtained by fitting the engine exhaust flow and the three-way catalytic converter center temperature.
Alternatively, the lean ratio model is obtained by fitting the engine speed and the engine torque.
In a second aspect of the present invention, a combustion preheating apparatus is disclosed, the apparatus comprising:
a control unit for controlling combustion of the engine using a stoichiometric air-fuel ratio at a cold start of the engine and detecting a first actual temperature of a three-way catalytic converter connected to an exhaust line of the engine in real time;
and the switching unit is used for controlling the engine to be circularly switched between a rich combustion state and a lean combustion state if the first actual temperature reaches a first temperature threshold value so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
In a third aspect of the invention, a computer readable storage medium is disclosed, having stored thereon a computer program which when executed by a vehicle processor implements the steps of the method of the first aspect.
In a fourth aspect of the invention, a vehicle is disclosed comprising a memory, a whole vehicle processor and a computer program stored on the memory and operable on the processor, the whole vehicle processor implementing the steps of the method of the first aspect when executing the program.
Through one or more technical schemes of the invention, the invention has the following beneficial effects or advantages:
the invention discloses a combustion preheating method, a combustion preheating device, a medium and a vehicle, wherein the engine is firstly controlled to burn by adopting a theoretical air-fuel ratio until the first actual temperature of a three-way catalytic converter reaches a first temperature threshold value, so that the three-way catalytic converter has oxygen storage capacity, then the engine is controlled to be circularly switched between a rich combustion state and a lean combustion state, oxidation-reduction reaction is generated in the three-way catalytic converter by triggering, and the preheating speed is increased by self-preheating of heat generated by the oxidation-reduction reaction, so that the purpose of quickly preheating the three-way catalytic converter is achieved.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures.
In the drawings:
FIG. 1 shows a schematic diagram of an engine and additional components according to one embodiment of the invention;
FIG. 2 illustrates a flow chart of a combustion preheating method according to an embodiment of the present invention;
FIG. 3 illustrates a logic control diagram for combustion preheating according to one embodiment of the present invention;
FIG. 4 illustrates a logic control schematic of engine combustion states according to one embodiment of the present invention;
FIG. 5 shows a schematic diagram of a connection structure of a combustion preheating apparatus according to an embodiment of the present invention;
FIG. 6 shows a block schematic diagram of a combustion preheating apparatus according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
In a first aspect, an embodiment of the invention discloses a combustion preheating method, which is mainly used for quickly preheating a three-way catalytic converter and a passive selective catalytic reducer which are sequentially connected on an engine exhaust pipe.
In order to facilitate a better understanding of the technical solution of the invention, additional components connected to the engine are first described. As shown in fig. 1, there is a schematic structural diagram of an engine and additional components, including: engine 10, three-way catalytic converter (Three Way Catalyst Converter, TWC 20) and passive selective catalytic reducer (Passive Selective Catalytic Reduction, PSCR 30). The TWC20 and PSCR30 are in turn connected to the exhaust circuit of the engine.
Because the temperature of the three-way catalytic converter and the temperature of the passive selective catalytic reducer are low when the engine is started cold, the three-way catalytic converter does not have the capability of eliminating NOx waste gas through reaction, and the passive selective catalytic reducer does not have the capability of storing ammonia. Therefore, in this stage, the engine combustion needs to be controlled to quickly preheat the three-way catalytic converter and the passive selective catalytic reducer, so that the three-way catalytic converter has the capability of eliminating NOx exhaust gas by reaction, and the passive selective catalytic reducer has the capability of storing ammonia.
When the three-way catalytic converter has the capability of eliminating NOx exhaust gas by reaction and the passive selective catalytic reducer has the capability of storing ammonia, the three-way catalytic converter can generate ammonia gas to generate chemical reaction with the NOx exhaust gas generated by engine combustion when the engine combusts, so that the NOx exhaust gas is converted into harmless gas N 2 To ensure that the emissions of the engine meet regulatory requirements. The passive selective catalytic reducer is capable of storing ammonia.
In order to achieve rapid warm-up of the three-way catalytic converter and the passive selective catalytic reducer at the time of engine cold start, referring to fig. 2, a schematic flow chart of a combustion warm-up method according to an embodiment of the present invention is disclosed. The combustion preheating method of the embodiment of the invention comprises the following steps:
s201, at the time of engine cold start, the engine combustion is controlled using the stoichiometric air-fuel ratio, and the first actual temperature of the three-way catalytic converter connected to the exhaust line of the engine is detected in real time.
The stoichiometric air-fuel ratio is the ratio of the minimum air mass required for complete combustion of the engine to the fuel mass, and is a known value. By adopting the theoretical air-fuel ratio to control the engine to burn, the engine can be controlled to enter an ideal combustion state to promote the rapid temperature rise of the engine, and the three-way catalytic converter can be rapidly heated through heat transfer. The three-way catalytic converter is correspondingly provided with a temperature sensor for detecting the first actual temperature of the three-way catalytic converter in real time.
S202, if the first actual temperature reaches a first temperature threshold, controlling the engine to circularly switch between a rich combustion state and a lean combustion state so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
When the first actual temperature reaches a first temperature threshold, the three-way catalytic converter has the oxygen storage capacity. On the basis, in order to quickly preheat the three-way catalytic converter, the engine is controlled to be cyclically switched between a rich state and a lean state. The engine can enable oxygen to be stored in the three-way catalytic converter in a lean combustion state, and the three-way catalytic converter is triggered to generate oxidation reaction. The oxidation reaction is shown in chemical formula 1 and chemical formula 2, and the heat generated by the oxidation reaction can self-preheat the inside of the three-way catalytic converter. The engine consumes oxygen stored in the three-way catalytic converter in a rich state, triggers the three-way catalytic converter to generate reduction reaction, the reduction reaction is shown in the following chemical formula 3, and heat generated by the reduction reaction can also enable the three-way catalytic converter to self-preheat.
Chemical formula 1:2CO+O 2 ＝2CO 2
Chemical formula 2:2C 2 H 6 +7O 2 ＝4CO 2 +6H 2 O
Chemical formula 3: nox=n 2 +O 2-
The engine is controlled to be circularly switched between a rich combustion state and a lean combustion state, so that the oxidation-reduction reaction generated in the three-way catalytic converter can be triggered to perform self-preheating, and the required temperature can be quickly reached.
In an alternative embodiment, the exhaust energy is increased by increasing the reserve torque of the three-way catalytic converter, thereby increasing the redox reaction capacity of the three-way catalytic converter, further increasing the temperature of the three-way catalytic converter. The temperature of the three-way catalytic converter can drive the temperature of a passive selective catalytic reducer connected with the three-way catalytic converter under the chassis to rise after rising.
Detecting an actual oxygen storage amount in the three-way catalytic converter in the process of controlling the engine to circularly switch between a rich combustion state and a lean combustion state; and determining a corresponding air excess coefficient according to the actual oxygen storage amount and the theoretical air-fuel ratio, and controlling the engine to circularly switch between a rich combustion state and a lean combustion state. The actual oxygen storage amount is used as a switching condition of a rich state and a lean state, and the combustion degree of the rich state and the lean state of the engine is controlled by combining the air excess coefficient, so that the change of the combustion state of the engine can be effectively controlled, and the three-way catalytic converter is quickly preheated.
Specifically, the set oxygen storage range is set as a reference for the rich-lean switching of the engine. If the actual oxygen storage amount exceeds the upper limit of the set oxygen storage range, determining a first air excess factor based on the theoretical air-fuel ratio to control the engine to enter a rich state; if the actual oxygen storage amount is lower than the lower limit of the set air storage range, determining a second air excess factor based on the theoretical air-fuel ratio to control the engine to burn and enter a lean combustion state; the first air excess factor is less than the second air excess factor; and if the actual oxygen storage amount is within the set air storage range, maintaining the combustion state of the engine unchanged. For example, the set oxygen storage range is set to [35%,80% ]. If the actual oxygen storage amount in the three-way catalytic converter is lower than 35%, the oxygen content in the three-way catalytic converter is not high, and the oxidation reaction effect is not good, so that the second air excess factor is determined based on the theoretical air-fuel ratio to control the engine to burn and enter a lean combustion state, the three-way catalytic converter stores oxygen gradually, and the oxygen storage amount in the three-way catalytic converter is improved. If the actual oxygen storage amount in the three-way catalytic converter exceeds 80%, which means that the oxygen content in the three-way catalytic converter exceeds the standard, the three-way catalytic converter may be broken down to enable oxygen to overflow to the passive selective catalytic reducer, ammonia stored in the passive selective catalytic reducer is consumed, the elimination effect of NOx waste gas is poor, and therefore the engine needs to be controlled to enter a rich combustion state based on the first air excess coefficient determined based on the theoretical air-fuel ratio, and oxygen in the three-way catalytic converter is consumed. If the actual oxygen storage amount is [35%,80% ], which means that the oxygen content is appropriate, the combustion state of the engine is maintained unchanged.
The air excess coefficient λ is a ratio of an actual air mass and a theoretical air mass when the engine is completely combusted, and may also represent a degree of difference between the actual air-fuel ratio and the theoretical air-fuel ratio: λ=actual air mass when the engine is fully combusted/theoretical air mass when the engine is fully combusted=actual air-fuel ratio/theoretical air-fuel ratio. The air excess coefficient lambda is used to control the degree of combustion of the engine. λ=1, indicating that the actual air-fuel ratio is equal to the stoichiometric air-fuel ratio, indicating that the stoichiometric mixture concentration is formed in the engine. Lambda > 1, the actual air-fuel ratio is greater than the theoretical air-fuel ratio, the air is excessive, lean mixture is formed in the engine, and the engine is promoted to enter a lean combustion state. Lambda < 1 indicates that the actual air-fuel ratio is less than the stoichiometric air-fuel ratio, and that air is deficient, a rich mixture is formed in the engine, causing the engine to enter a rich condition.
Wherein, the first air excess coefficient lambda for controlling the engine to enter the rich state 1 E (0.98,1), a second air excess coefficient lambda controlling the engine to enter lean burn state 2 ∈(1，1.02)。
After controlling the engine to circularly switch between a rich state and a lean state, detecting and connecting a first actual temperature in real time, and if the first actual temperature reaches a second temperature threshold value, indicating that the three-way catalytic converter has the ammonia production capacity, and controlling the engine to enter the rich state; the second temperature threshold is greater than the first temperature threshold. Illustratively, the second temperature threshold is 350 ℃, and the first temperature threshold is 200 ℃, but this is not limiting.
In an alternative embodiment, if the first actual temperature reaches a second temperature threshold, detecting in real time a second actual temperature of a passive selective catalytic reducer connected to the three-way catalytic converter; if the second actual temperature reaches the third temperature threshold on the basis that the first actual temperature reaches the second temperature threshold, the passive selective catalytic reduction device has the ammonia storage capacity at the same time of the ammonia production capacity of the three-way catalytic converter, and the engine is controlled to enter a rich combustion state so as to rapidly produce ammonia. The third temperature threshold is, for example, 150 ℃, but is not limiting.
For the purposes of illustrating and explaining the present invention, reference is now made to FIG. 3, which is a logic control diagram for combustion preheating.
S301, engine combustion is controlled using the stoichiometric air-fuel ratio.
S302, judging whether the first actual temperature of the three-way catalytic converter reaches 200 ℃. If so, it indicates that the three-way catalytic converter has the oxygen storage capacity, the routine proceeds to S303. If not, return to S301.
S303, controlling the engine rich-lean switching. The main purpose of the rich-lean switching is to trigger the oxidation-reduction reaction generated inside the three-way catalytic converter to perform self-preheating.
S304, judging whether the three-way catalytic converter reaches 350 ℃. If not, return to S303.
S305, judging whether the passive selective catalytic reducer reaches 150 ℃. If not, return to S303.
If the determination results of S304 and S305 are both yes, S306 is executed.
S306, controlling the engine to enter a rich state.
When the engine is controlled to enter a rich state, a rich ratio model can be used for control, and the air excess coefficient is used for controlling the combustion degree of the engine in the rich state. Illustratively, the air excess coefficient λε (0.95-0.96). The rich ratio model will be described in detail later, and will not be described in detail here. It is noted that the air excess factor may also be used directly to control the degree of combustion in the rich condition of the engine.
In an alternative embodiment, after the engine is controlled to enter a rich state, the rich time of the engine needs to consider the consumption of oxygen storage amount in the three-way catalytic converter, and as the rich consumes oxygen in the three-way catalytic converter, the situation that the consumption of oxygen is excessive to cause breakdown of the catalyst, and CO and HC cannot be oxidized to cause emissions exceeding standards needs to be avoided. In specific implementation, detecting the actual oxygen consumption in the three-way catalytic converter in real time; and when the actual oxygen consumption reaches a set oxygen consumption threshold, controlling the engine to enter a lean-burn state. Illustratively, the oxygen consumption threshold is set at 20% of the maximum oxygen storage. Specifically, when the engine is controlled to enter a lean-burn state, a lean-burn ratio model can be used for control, and the air excess coefficient is used for controlling the combustion degree of the engine in the lean-burn state. The lean burn ratio model will be described in detail later, and will not be described in detail here. It is noted that the air excess factor may also be used directly herein to control the degree of combustion in the lean state of the engine.
In an alternative embodiment, the combustion state of the engine is divided into a rich state and a lean state. In the rich state of the engine, the generated tail gas can generate ammonia in the three-way catalytic converter: NH (NH) 3 The main reaction equations are chemical formulas 4 and 5, and are stored in a passive selective catalytic reducer. In addition, the engine additionally consumes oxygen stored in the three-way catalytic converter in a rich condition. In the lean-burn state of the engine, the ammonia stored in the passive selective catalytic reducer reacts with NOx waste gas in the tail gas to convert the NOx waste gas into harmless gas N 2 To reduce NOx emissions and ensure that the emissions of the engine meet regulatory requirements. Similarly, the ammonia stored in the passive selective catalytic reducer is consumed by the chemical reaction, and the ammonia storage amount in the passive selective catalytic reducer is reduced, and the main reaction equations are chemical formula 6 and chemical formula 7. At this time, the three-way catalytic converter gradually stores oxygen due to the lean-burn state of the engine, and the oxygen content in the three-way catalytic converter can rise.
Chemical formula 4:2CO+2NO+3H 2 →2NH 3 +2CO 2 。
Chemical formula 5:2NO+5H 2 →2NH 3 +2H 2 O。
Chemical formula 6: NH (NH) 3 +NOx→N 2 +H 2 O。
Chemical formula 7: NH (NH) 3 +O 2 →N 2 +H 2 O。
Notably, the amount of ammonia stored in the passive selective catalytic reducer is dynamically variable, but needs to be maintained within a target production range. If the actual ammonia storage amount exceeds the upper limit of the target yield range, selecting the lean burn ratio model, and controlling the engine to enter a lean burn state; and if the actual ammonia storage amount is lower than the lower limit of the target yield range, selecting the rich ratio model, and controlling the engine to enter a rich state. And if the ammonia storage amount is in the target yield range, maintaining the combustion state of the engine unchanged. Illustratively, the target production range is [ 10% of the saturated stored ammonia amount to 90% of the saturated stored ammonia amount ], but no limitation is made. If the ammonia gas leakage rate exceeds 90%, an ammonia gas leakage accident is liable to occur. If the amount is less than 10%, nox exhaust gas cannot be converted effectively, and Nox exhaust gas emission accidents are liable to occur. Therefore, in the specific implementation process, if the ammonia storage amount L is more than 90%, the lean burn ratio model is selected to control the combustion state of the engine to be a lean burn state, and ammonia is consumed, so that the ammonia storage amount is reduced; if L is less than 10%, the engine combustion state is controlled to be a rich combustion state by selecting a rich combustion ratio model, ammonia gas is generated, and the ammonia storage amount is increased.
In order to accurately control the ammonia yield, detecting the actual ammonia storage amount of the passive selective catalytic reducer in real time; and controlling the engine to be cyclically switched between a rich combustion state and a lean combustion state according to the actual ammonia storage amount, and controlling the ammonia storage amount in the passive selective catalytic reducer within a target yield range.
In a specific implementation process, selecting a rich ratio model or a lean ratio model by referring to the actual ammonia storage amount; and controlling the engine combustion by using the rich ratio model or the lean ratio model so that the actual ammonia storage amount is in a target yield range.
The engine is controlled to be in a rich state by the rich ratio model, so that ammonia gas is generated in the three-way catalytic converter and stored in the passive selective catalytic reducer. The lean burn ratio model is used for controlling the engine to be in a lean burn state, so that the ammonia gas and NOx waste gas generated by the engine are subjected to chemical reaction to be consumed.
When a rich combustion ratio model or a lean combustion ratio model is selected with reference to the actual ammonia storage amount, if the ammonia storage amount exceeds the upper limit of the target yield range, the actual ammonia storage amount is excessive, and overflow accidents are easy to occur, so that the lean combustion ratio model is selected to control the engine to be in a lean combustion state, and ammonia gas is consumed; if the ammonia storage amount is lower than the lower limit of the target yield range, which means that the ammonia storage amount is insufficient and NOx waste gas cannot be effectively removed, a rich combustion ratio model is selected to control the engine to enter a rich combustion state, and ammonia gas is generated; and if the ammonia storage amount is in the target yield range, maintaining the selected rich ratio model or lean ratio model unchanged.
In an alternative embodiment, the rich model is obtained by fitting the engine exhaust flow and the three-way catalytic converter center temperature. The relation of the rich ratio model is as follows: AF (AF) 1 =f (Q, T). Wherein AF is the same as 1 And the fuel ratio is a fuel ratio value corresponding to the fuel ratio model, Q is the exhaust flow of the three-way catalytic converter, and T is the center temperature of the three-way catalytic converter. It is worth noting that the lean ratio value changes in real time following the actual operating parameters of the three-way catalytic converter. When the engine combustion is controlled by the rich ratio model, the current engine exhaust flow and the center temperature of the current three-way catalytic converter are brought into the rich ratio model for calculation, and then the actual rich ratio value can be obtained. It is worth noting that the rich ratio model fitted by different vehicle models is different.
Further, the purpose of the rich combustion is to improve the ammonia gas generation efficiency. Even though the engine is controlled by a rich ratio model, the engine has different ammonia gas generating efficiency when facing different working conditions. Therefore, in order to improve the ammonia gas generation efficiency, the ammonia gas generation efficiency can be consulted to reversely restrict the rich ratio model, so that the actual rich ratio value corresponding to different working conditions is obtained, and the ammonia gas generation efficiency can be ensured when the engine faces different working conditions. It is worth noting that the actual rich ratio value shows adaptive dynamic change according to different working conditions. Specifically, a corresponding air excess coefficient is determined according to a target ammonia gas generation efficiency interval, and the air excess coefficient is utilized to restrict the rich ratio model in real time. Illustratively, the air excess coefficient λε (0.95-0.96). The relation between the air excess coefficient lambda and the rich ratio model is as follows: air excess coefficient λ=the intake air amount corresponding to the actual rich ratio value/the standard intake air amount. Therefore, a specific value of the air excess coefficient lambda is determined according to the interval, and the actual rich ratio value of the rich ratio model is constrained in real time by combining the relational expression.
In an alternative embodiment, when the fuel supply is restored due to the fuel cut of the engine, oxygen breaks down the three-way catalytic converter and overflows into the passive selective catalytic reducer, and the oxygen reacts with the ammonia in the passive selective catalytic reducer to consume the ammonia. And if the fuel cut of the engine is detected and the fuel supply is restored, the engine is controlled to burn by using the rich ratio model to supplement ammonia gas, so that the generated NOx is prevented from being unable to be reduced. The engine speed is illustratively sensed in real time and when the engine speed reaches a set threshold, such as 8000 rpm, an indication of engine fuel cut is provided. When the engine speed is less than a set threshold, such as 8000 rpm, the engine resumes fueling. Of course, the invention can also refer to other ways to detect engine fuel cut and fuel return, without limitation.
The above is a related description of controlling engine combustion in a rich model, and the following describes a specific implementation of controlling engine combustion in a lean model.
The lean burn ratio model is obtained by fitting the engine speed and the engine torque. The lean ratio model has the following relation: AF (AF) 2 ＝f(N，T 1 ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein AF is the same as 2 Is a lean burn ratio value corresponding to the lean burn ratio model, N is the engine speed, T 1 Is the engine torque. When the lean ratio model is used for controlling the combustion of the engine, the current engine speed and the current engine torque are carried into the lean ratio model for calculation, and then the actual lean ratio value can be obtained. Notably, the lean ratio value varies in real time with the actual operating parameters of the engine. Because the lean burn aims at saving fuel, the optimal fuel consumption ratio is utilized to determine the corresponding air excess coefficient lambda, and the lean burn ratio model is constrained in real time by utilizing the air excess coefficient lambda, so that the engine achieves the optimal fuel consumption ratio in a lean burn state. The relation between the air excess coefficient lambda and the lean burn ratio model is as follows: air excess coefficient lambda=the intake air amount corresponding to the actual lean ratio valueStandard intake air amount. Therefore, the specific value of the air excess coefficient lambda is determined according to the interval, and the actual lean ratio value of the lean ratio model is constrained in real time by combining the relation, so that the engine reaches the optimal fuel consumption ratio in the lean state.
The above is a description of controlling engine combustion in a lean ratio model, and it is noted that the rich and lean ratio models of the present invention are two different air-fuel ratio models, and the rich ratio model focuses on ammonia production efficiency, so it is mainly obtained by fitting with reference to the exhaust flow rate and the center temperature of the three-way catalytic converter. Furthermore, in order to ensure the ammonia generation efficiency, the corresponding air excess coefficient is set to restrict the rich combustion ratio model by referring to the relation between the ammonia generation efficiency and the air excess coefficient, so that the three-way catalytic converter can generate ammonia more quickly under the rich combustion state of the engine, and the supplementing efficiency when the ammonia is insufficient is ensured. In addition, the oxygen storage characteristic of the three-way catalytic converter and the enrichment time of the ammonia generation efficiency control rich combustion ratio model are considered, so that on the basis of ensuring the ammonia generation efficiency, each emission index of the engine is ensured to meet the regulation requirement. The lean ratio model is focused on fuel consumption, so the lean ratio model is obtained by fitting the rotating speed of the reference engine and the torque of the engine. Further, in order to keep low fuel consumption combustion, the optimal fuel consumption ratio is referred to determine a corresponding air excess coefficient, and the lean burn ratio model is constrained in real time by utilizing the corresponding air excess coefficient lambda, so that the fuel consumption of the engine can be reduced as much as possible in a lean burn state, and the engine meets the economic requirement.
For further explanation and explanation of the present invention, reference is now made to FIG. 4, which is a schematic diagram of the logic control of engine combustion conditions. When the engine is cold started, the air supply excess coefficient λ=1 is controlled until the temperature of the three-way catalytic converter (simply referred to as a catalyst in fig. 4) reaches 200 ℃, and then the air supply excess coefficient λ is controlled to be in the vicinity of the theoretical air-fuel ratio: and the engine is quickly switched between 0.98 and 1.02 to quickly switch between rich and lean. The triggering condition for the switch refers to the change in oxygen storage of the three-way catalytic converter until the temperature of the three-way catalytic converter reaches 350 ℃ and the passive selective catalytic reducer reaches 150 ℃. And controlling the engine to be in a rich state by adopting a rich ratio model. At this time, the oxygen storage amount of the three-way catalytic converter is decreased, the ammonia storage amount in the passive selective catalytic reduction device is increased, and the oxygen storage amount of the three-way catalytic converter is 10% or the ammonia storage amount in the passive selective catalytic reduction device is more than 90% to switch. The combustion of the subsequent engine may be rich-lean with reference to the oxygen storage amount of the three-way catalytic converter and/or the ammonia storage amount in the passive selective catalytic reducer. It is noted that the specific values in fig. 4 are for example only, and may be adapted in actual situations.
In a second aspect, based on the same inventive concept as the combustion preheating method provided in the foregoing first aspect, the embodiment of the present disclosure further provides a combustion preheating device, in which an exhaust line of an engine is sequentially connected to a three-way catalytic converter and a passive selective catalytic reducer, and the combustion preheating device is connected to the engine, the three-way catalytic converter and the passive selective catalytic reducer, and a connection structure thereof is schematically shown in fig. 5.
Referring to fig. 6, a schematic block diagram of a combustion preheating apparatus includes:
a control unit 601 for controlling combustion of an engine using a stoichiometric air-fuel ratio at a cold start of the engine, and detecting a first actual temperature of a three-way catalytic converter connected to an exhaust line of the engine in real time;
and the switching unit 602 is configured to control the engine to switch between the rich state and the lean state in a circulating manner if the first actual temperature reaches a first temperature threshold, so as to trigger the three-way catalytic converter to generate an oxidation-reduction reaction for self-preheating.
It should be noted that, the specific manner in which the operation of each device is performed in the combustion preheating apparatus provided in the embodiment of the first aspect is described in detail in the embodiment of the method provided in the first aspect, and the specific implementation process may refer to the embodiment of the method provided in the first aspect, which will not be described in detail herein.
In a third aspect, based on the same inventive concept as the combustion preheating method provided in the foregoing first aspect embodiment, the present specification further provides a computer-readable storage medium having stored thereon a computer program which, when executed by a vehicle processor, implements the steps of the method described in the foregoing first aspect.
It should be noted that, the specific manner of the computer readable storage medium provided in the embodiments of the present specification has been described in detail in the method embodiments provided in the first aspect, and the specific implementation process may refer to the method embodiments provided in the first aspect, which will not be described in detail herein.
In a fourth aspect, based on the same inventive concept as the combustion preheating method provided in the foregoing first aspect, an embodiment of the present disclosure further provides a vehicle, including a memory, a whole vehicle processor, and a computer program stored on the memory and capable of running on the processor, where the whole vehicle processor implements the steps of the method in the first aspect when executing the program.
It should be noted that, the specific manner in which the operations of the respective devices are performed in the vehicle provided in the embodiments of the first aspect is described in detail in the embodiments of the method provided in the first aspect, and the specific implementation process may refer to the embodiments of the method provided in the first aspect, which will not be described in detail herein.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.
Claims (15)
1. A combustion preheating method, characterized in that the method comprises:
when the engine is started in a cold mode, the engine is controlled to burn by adopting a theoretical air-fuel ratio, and the first actual temperature of a three-way catalytic converter connected to an exhaust pipeline of the engine is detected in real time;
and if the first actual temperature reaches a first temperature threshold, controlling the engine to circularly switch between a rich combustion state and a lean combustion state so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
2. The method of claim 1, wherein said controlling said engine to switch back and forth between a rich condition and a lean condition comprises:
detecting an actual oxygen storage amount in the three-way catalytic converter;
and determining a corresponding air excess coefficient according to the actual oxygen storage amount and the theoretical air-fuel ratio, and controlling the engine to circularly switch between a rich combustion state and a lean combustion state.
3. The method according to claim 2, wherein the determining the corresponding air excess ratio according to the actual oxygen storage amount and the stoichiometric air-fuel ratio controls the engine to cyclically switch between a rich state and a lean state, specifically comprising:
if the actual oxygen storage amount exceeds the upper limit of the set oxygen storage range, determining a first air excess factor based on the theoretical air-fuel ratio to control the engine to enter a rich state;
if the actual oxygen storage amount is lower than the lower limit of the set air storage range, determining a second air excess factor based on the theoretical air-fuel ratio to control the engine to burn and enter a lean combustion state; the first air excess factor is less than the second air excess factor;
and if the actual oxygen storage amount is within the set air storage range, maintaining the combustion state of the engine unchanged.
4. A method according to claim 3, wherein the first air excess factor λ 1 ∈(0.98，1) The second air excess coefficient lambda 2 ∈(1，1.02)。
5. The method of claim 1, wherein after said controlling the engine to cyclically switch between a rich state and a lean state, the method further comprises:
if the first actual temperature reaches a second temperature threshold value, controlling the engine to enter a rich state; the second temperature threshold is greater than the first temperature threshold.
6. The method of claim 5, wherein controlling the engine to enter the rich condition if the first actual temperature reaches a second temperature threshold, specifically comprises:
detecting in real time a second actual temperature of a passive selective catalytic reducer connected to the three-way catalytic converter;
and if the second actual temperature reaches a third temperature threshold value, controlling the engine to enter a rich state.
7. The method of claim 6, wherein after said controlling said engine into a rich condition, said method further comprises:
detecting the actual oxygen consumption in the three-way catalytic converter in real time;
and when the actual oxygen consumption reaches a set oxygen consumption threshold, controlling the engine to enter a lean-burn state.
8. The method of claim 6, wherein after said controlling said engine into a rich condition, said method further comprises:
detecting the actual ammonia storage amount of the passive selective catalytic reducer in real time;
and controlling the engine to circularly switch between a rich combustion state and a lean combustion state according to the actual ammonia storage amount.
9. The method of claim 8, wherein said controlling the engine to cycle between rich and lean conditions based on the actual ammonia storage amount comprises:
selecting a rich ratio model or a lean ratio model with reference to the actual ammonia storage amount; the rich ratio model is used for controlling the engine to be in a rich state so as to generate ammonia in the three-way catalytic converter and store the ammonia into the passive selective catalytic reducer; the lean burn ratio model is used for controlling the engine to be in a lean burn state, so that the ammonia gas and NOx waste gas generated by the engine are subjected to chemical reaction to be consumed;
and controlling the engine combustion by using the rich ratio model or the lean ratio model so that the actual ammonia storage amount is in a target yield range.
10. The method of claim 9, wherein said selecting a rich or lean model with reference to said actual ammonia storage amount comprises:
if the actual ammonia storage amount exceeds the upper limit of the target yield range, selecting the lean ratio model;
and if the actual ammonia storage amount is lower than the lower limit of the target yield range, selecting the rich ratio model.
11. The method of claim 9 wherein the rich model is obtained by fitting an engine exhaust flow and a three-way catalytic converter center temperature.
12. The method of claim 9, wherein the lean ratio model is derived by fitting an engine speed and an engine torque.
13. A combustion preheating apparatus, the apparatus comprising:
a control unit for controlling combustion of the engine using a stoichiometric air-fuel ratio at a cold start of the engine and detecting a first actual temperature of a three-way catalytic converter connected to an exhaust line of the engine in real time;
and the switching unit is used for controlling the engine to be circularly switched between a rich combustion state and a lean combustion state if the first actual temperature reaches a first temperature threshold value so as to trigger the three-way catalytic converter to generate oxidation-reduction reaction for self-preheating.
14. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a vehicle processor, implements the steps of the method according to any of claims 1-12.
15. A vehicle comprising a memory, a vehicle processor and a computer program stored on the memory and operable on the processor, wherein the vehicle processor performs the steps of the method of any of claims 1-12 when the program is executed.
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| CN202311614152.6A CN117514495A (en) | 2023-11-27 | 2023-11-27 | Combustion preheating method, device, medium and vehicle |
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| CN202311614152.6A CN117514495A (en) | 2023-11-27 | 2023-11-27 | Combustion preheating method, device, medium and vehicle |
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