Natural gas engine thermal management method and device and post-processing system

Abstract

The invention discloses a natural gas engine thermal management method and device and an aftertreatment system.The method comprises the steps that when a natural gas engine stably operates, the exhaust oxygen content, the excess air coefficient and the outlet temperature of a three-way catalyst are monitored in real time; determining the operation condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content; when it is detected that the operation working condition is in the first state, a bypass valve of the exhaust bypass pipeline is opened in a delayed mode according to first delay time, so that exhaust of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and the exhaust heating system is controlled to conduct heating, so that the conversion efficiency of the three-way catalyst is improved; and when it is detected that the operation working condition is in the second state, opening the bypass valve in a delayed mode according to second delay time, so that exhaust of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and the natural gas nozzle is controlled to spray natural gas, so that the conversion efficiency of the three-way catalyst is improved and recovered to the speed of the specific interval.

Description

Technical Field

[0001] The present application relates to the technical field of engine aftertreatment, and in particular to a natural gas engine thermal management method, device and aftertreatment system. Background Art

[0002] As emission regulations become increasingly stringent in the future, the emission limits of NOx (nitrogen oxides) and CH4 (methane) will be reduced. At present, the cold CH4 emission of natural gas engines is high. How to reduce cold CH4 emission has become the key to the next generation of emission technology. In order to meet more stringent emission regulations in the future, a heatable after-treatment system for combustible gas injection is designed to improve the conversion efficiency of after-treatment during cold start and low exhaust temperature (i.e., low exhaust temperature), increase the outlet temperature, and quickly restore Lambda (excess air coefficient, i.e., the ratio of the actual intake volume in the engine cylinder to the theoretical intake volume) after the gas cut-off conditions such as reverse drag. The heatable TWC (three-way catalytic converter) after-treatment system will be an important technical measure.

[0003] In the prior art, when the engine is cold-started, the conversion efficiency is low when the TWC has not reached the ignition temperature (specifically, the temperature at which the conversion efficiency of TWC to CH4 reaches 50%). At this time, the TWC lacks the ability to convert exhaust gas, and when the engine and its exhaust system are filled with oxygen, the TWC seriously deviates from the conversion efficiency window. If the in-cylinder nozzle is used for enrichment, there will be a large air path delay. It takes a long time to enrich again and return to near Lambda=1. During this time, the TWC conversion efficiency is low.

[0004] Therefore, how to improve the conversion efficiency of TWC has become an urgent problem to be solved in this field. Summary of the invention

[0005] The present application provides a natural gas engine thermal management method, device and aftertreatment system, aiming to improve the TWC conversion efficiency of the natural gas engine aftertreatment system.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] A natural gas engine thermal management method is applied to a post-processor system with a newly added exhaust bypass pipeline, wherein the exhaust bypass pipeline is preset with a natural gas nozzle and an exhaust heating system, and the method comprises:

[0008] When the natural gas engine is running stably, the exhaust oxygen content, excess air coefficient and outlet temperature of the three-way catalytic converter of the post-treatment system are monitored in real time;

[0009] Determining the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content;

[0010] When it is detected that the operating condition is in a first state, the bypass valve of the exhaust bypass pipeline is opened with a delay according to a first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the exhaust heating system is controlled to heat the exhaust gas in the exhaust bypass pipeline to improve the conversion efficiency of the three-way catalytic converter; the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value;

[0011] When it is detected that the operating condition is in the second state, the bypass valve is opened with a delay according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the natural gas nozzle is controlled to spray natural gas into the exhaust gas in the exhaust bypass pipeline, so as to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range; the second state indicates that the gas of the natural gas engine is cut off.

[0012] Optionally, the method further includes:

[0013] In the process of controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the outlet temperature;

[0014] When it is detected that the changed outlet temperature meets the first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

[0015] Optionally, the method further includes:

[0016] In the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the excess air coefficient;

[0017] When it is detected that the changed excess air coefficient meets the second preset threshold, the bypass valve is closed, and the natural gas nozzle is controlled to stop injecting natural gas.

[0018] Optionally, determining the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content includes:

[0019] If the outlet temperature is less than a first calibration temperature, determining that the operating condition of the natural gas engine is in a first state;

[0020] If the exhaust oxygen content is less than the first calibrated concentration, it is determined that the operating condition of the natural gas engine is in the second state.

[0021] A natural gas engine thermal management device, comprising:

[0022] The parameter monitoring unit is used to monitor the exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalytic converter of the after-treatment system in real time when the natural gas engine is running stably;

[0023] An operating condition identification unit, used to determine the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content;

[0024] a heating control unit, for, when detecting that the operating condition is in a first state, delaying opening of a bypass valve of an exhaust bypass pipeline according to a first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and controlling an exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, so as to improve the conversion efficiency of the three-way catalytic converter; the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value;

[0025] The gas filling control unit is used for, when it is detected that the operating condition is in the second state, delaying the opening of the bypass valve according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and controlling the natural gas nozzle to spray natural gas into the exhaust gas in the exhaust bypass pipeline, so as to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range; the second state indicates that the gas of the natural gas engine is cut off.

[0026] Optionally, the heating control unit is further used for:

[0027] In the process of controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the outlet temperature;

[0028] When it is detected that the changed outlet temperature meets the first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

[0029] Optionally, the gas filling control unit is further used for:

[0030] In the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the excess air coefficient;

[0031] When it is detected that the changed excess air coefficient meets the second preset threshold, the bypass valve is closed, and the natural gas nozzle is controlled to stop injecting natural gas.

[0032] Optionally, the operating condition identification unit is specifically used for:

[0033] If the outlet temperature is less than a first calibration temperature, determining that the operating condition of the natural gas engine is in a first state;

[0034] If the exhaust oxygen content is less than the first calibrated concentration, it is determined that the operating condition of the natural gas engine is in the second state.

[0035] A post-processing system, comprising:

[0036] Natural gas engine, electronic control unit, exhaust gas recirculation system, exhaust pipe, exhaust bypass line, bypass valve, natural gas nozzle, exhaust heating system, front oxygen sensor, three-way catalytic converter, rear oxygen sensor and temperature sensor;

[0037] Wherein, the exhaust port of the natural gas engine is respectively connected to the intake ports of the exhaust gas recirculation system, the exhaust pipe, and the exhaust bypass pipeline;

[0038] The air inlet of the exhaust bypass pipeline is provided with the bypass valve, the main body of the exhaust bypass pipeline is provided with the natural gas nozzle and the exhaust heating system, and the air outlet of the exhaust bypass pipeline is connected to the three-way catalytic converter;

[0039] The front oxygen sensor is preset on the air inlet of the three-way catalytic converter, and the rear oxygen sensor and the temperature sensor are respectively preset on the air outlet of the three-way catalytic converter;

[0040] The electronic control unit is respectively connected to the natural gas engine, the bypass valve, the natural gas nozzle, the exhaust heating system, the front oxygen sensor, the rear oxygen sensor and the temperature sensor by wired communication, and the electronic control unit is used to execute the above-mentioned natural gas engine thermal management method.

[0041] Optionally, the front oxygen sensor is used to send the exhaust oxygen content to the electronic control unit, the temperature sensor is used to send the outlet temperature to the electronic control unit, and the rear oxygen sensor is used to send the purified exhaust oxygen content to the electronic control unit, so that the electronic control unit calculates the corresponding excess air coefficient based on the purified exhaust oxygen content.

[0042] The technical solution provided by the present application monitors the exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalytic converter in real time when the natural gas engine is running stably. Based on the outlet temperature and exhaust oxygen content, the operating condition of the natural gas engine is determined. When it is detected that the operating condition is in the first state, according to the first delay time, the bypass valve of the exhaust bypass pipeline is opened with a delay, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the exhaust heating system is controlled to heat the exhaust gas to improve the conversion efficiency of the three-way catalytic converter. When it is detected that the operating condition is in the second state, according to the second delay time, the bypass valve is opened with a delay, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the natural gas nozzle is controlled to spray natural gas to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range. This application uses an exhaust heating system, a natural gas nozzle and an exhaust bypass line to solve the problem of low TWC conversion efficiency during cold start and low exhaust temperature of the natural gas engine, greatly improves the control of exhaust temperature (i.e., the outlet temperature of the three-way catalytic converter), and when the natural gas engine is in a gas cut-off condition, it can ensure that the TWC conversion efficiency can be quickly restored to a specific range, thereby effectively improving the overall conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A schematic diagram of the architecture of a post-processing system provided in an embodiment of the present application;

[0045] Figure 2 A schematic flow chart of a natural gas engine thermal management method provided in an embodiment of the present application;

[0046] Figure 3 A schematic diagram of a heating control logic provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of a gas filling control logic provided in an embodiment of the present application;

[0048] Figure 5 A schematic diagram of the architecture of a natural gas engine thermal management device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0051] The applicant found that the heat source of the after-treatment system of the existing natural gas engine relies on the engine exhaust. When the engine is cold-started, the three-way catalytic converter needs a long time to reach the ignition temperature, and the reduction of the engine exhaust temperature during long-term low-load operation will affect the conversion efficiency of the three-way catalytic converter. After the reverse-tow operation of the existing natural gas engine, the three-way catalytic converter is almost exposed to the atmospheric environment, deviating from the conversion efficiency window. After the reverse-tow operation and other gas-cut-off conditions, the excess air coefficient is restored by relying on the natural gas nozzle in the cylinder, resulting in a large gas delay, which affects the overall conversion efficiency.

[0052] To this end, an embodiment of the present application provides a post-processor system suitable for use in natural gas engines to improve the TWC conversion efficiency of the natural gas engine post-processing process.

[0053] like Figure 1 As shown, it is a schematic diagram of the architecture of a post-processing system provided in an embodiment of the present application, which includes the following components.

[0054] Natural gas engine 1, electronic control unit 2, exhaust gas recirculation system 3, exhaust pipe 4, exhaust bypass line 5, bypass valve 6, natural gas nozzle 7, exhaust heating system 8, front oxygen sensor 9, three-way catalytic converter 10, rear oxygen sensor 11 and temperature sensor 12.

[0055] The exhaust port of the natural gas engine 1 is connected to the intake ports of the exhaust gas recirculation system 3 , the exhaust pipe 4 , and the exhaust bypass pipeline 5 .

[0056] The air inlet of the exhaust bypass pipeline 5 is provided with a bypass valve 6 , the main body of the exhaust bypass pipeline 5 is provided with a natural gas nozzle 7 and an exhaust heating system 8 , and the air outlet of the exhaust bypass pipeline 5 is connected to a three-way catalytic converter 10 .

[0057] The front oxygen sensor 9 is preset on the air inlet of the three-way catalytic converter 10 , and the rear oxygen sensor 11 and the temperature sensor 12 are preset on the air outlets of the three-way catalytic converter 10 .

[0058] The electronic control unit 2 is connected to the natural gas engine 1 , the bypass valve 6 , the natural gas nozzle 7 , the exhaust heating system 8 , the front oxygen sensor 9 , the rear oxygen sensor 11 and the temperature sensor 12 by wired communication.

[0059] In some examples, the bypass valve 6 may be a three-way valve.

[0060] In some examples, the heating method provided by the exhaust heating system 8 includes but is not limited to electric heating, infrared heating, electromagnetic induction heating, etc.

[0061] In some examples, the front oxygen sensor 9 is used to collect the exhaust oxygen content of the after-treatment system in real time (understood as the oxygen concentration in the exhaust), the temperature sensor 12 is used to collect the outlet temperature of the three-way catalytic converter 10 in real time, and the rear oxygen sensor 11 is used to collect the purified exhaust oxygen content (the oxygen concentration in the purified exhaust) after treatment by the three-way catalytic converter 10 in real time. The purified exhaust oxygen content is related to the excess air coefficient of the after-treatment system, and the corresponding excess air coefficient can be calculated based on the purified exhaust oxygen content.

[0062] Optionally, the front oxygen sensor 9 is used to send the exhaust oxygen content to the electronic control unit 2, the temperature sensor 12 is used to send the outlet temperature to the electronic control unit 2, and the rear oxygen sensor 11 is used to send the purified exhaust oxygen content to the electronic control unit 2, so that the electronic control unit 2 calculates the corresponding excess air coefficient based on the purified exhaust oxygen content.

[0063] It should be noted that the natural gas engine thermal management method shown in the embodiment of the present application can be executed by the electronic control unit 2 in the after-treatment system to solve the problem of low conversion efficiency of the three-way catalytic converter during cold start and low exhaust temperature, so that when the natural gas engine ends the gas cut-off condition such as reverse towing, the three-way catalytic converter can quickly return to the conversion efficiency range of excess air coefficient = 1, thereby improving the overall conversion efficiency.

[0064] like Figure 2 As shown, it is a flow chart of a natural gas engine thermal management method provided in an embodiment of the present application, which can be executed based on an ECU (Electronic Control Unit) and includes the following steps.

[0065] S201: When the natural gas engine is running stably, the exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalytic converter of the after-treatment system are monitored in real time.

[0066] Among them, the natural gas engine will report multiple performance parameters (such as output torque, intake volume, output speed, etc.) to the ECU in real time. Therefore, based on the multiple performance parameters of the natural gas engine, the ECU can identify whether the natural gas engine is running stably.

[0067] In some examples, the ECU can monitor the exhaust oxygen content in real time through the signal reported by the front oxygen sensor, monitor the excess air coefficient in real time through the signal reported by the rear oxygen sensor, and detect the outlet temperature in real time through the signal reported by the temperature sensor.

[0068] S202: Determine the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content.

[0069] Among them, based on the outlet temperature and the exhaust oxygen content, the operating conditions that affect the conversion efficiency of the three-way catalytic converter can be determined, such as the conversion efficiency of the three-way catalytic converter being less than a specified value (i.e., the TWC conversion efficiency is low) due to operating conditions such as cold start of the natural gas engine and low exhaust temperature, or the speed at which the TWC conversion efficiency recovers to a specific range (i.e., Lambda is restored to the conversion efficiency range corresponding to Lambda=1) being reduced due to gas cut-off conditions such as the end of reverse towing of the natural gas generator.

[0070] Optionally, if the outlet temperature is less than the first calibration temperature, it is determined that the operating condition of the natural gas engine is in the first state. If the exhaust oxygen content is less than the first calibration concentration, it is determined that the operating condition of the natural gas engine is in the second state.

[0071] It should be noted that the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value, and the second state indicates that the gas of the natural gas engine is cut off.

[0072] In some examples, specific values ​​of the first calibrated temperature and the first calibrated concentration may be determined based on performance parameters of the natural gas engine.

[0073] S203: When it is detected that the operating condition is in the first state, the bypass valve of the exhaust bypass line is opened with a delay according to the first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter through the exhaust bypass line, and the exhaust heating system is controlled to heat the exhaust gas in the exhaust bypass line to improve the conversion efficiency of the three-way catalytic converter.

[0074] Among them, controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipe can increase the outlet temperature, so as to improve the conversion efficiency of the three-way catalytic converter.

[0075] It should be noted that, according to the first delay time, delaying the opening of the bypass valve of the exhaust bypass line can eliminate the premature heating behavior caused by the detection deviation of the outlet temperature, and ensure that the heating behavior is performed when the operating condition is in the first state.

[0076] Optionally, while controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass duct, changes in the outlet temperature are monitored in real time. When it is detected that the changed outlet temperature meets a first preset threshold, the bypass valve is closed and the exhaust heating system is controlled to stop heating.

[0077] It is understandable that by controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipe, the outlet temperature will increase. By monitoring the changes in the outlet temperature in real time, when the changed outlet temperature meets the first preset threshold, that is, the conversion efficiency of the three-way catalytic converter has been restored (that is, the TWC conversion efficiency is greater than or equal to the specified value), there is no need to heat the exhaust gas anymore, so the bypass valve is closed and the exhaust heating system is controlled to stop heating to save energy consumption.

[0078] In some examples, the implementation logic of controlling the exhaust heating system to perform heating work can be found in Figure 3 The steps shown are as follows: (1) monitoring the outlet temperature T of the TWC; (2) determining whether T is lower than T1 (i.e., the first calibration temperature); if T is lower than T1, determining that the operating condition of the natural gas engine is the TWC low conversion efficiency state (i.e., the first state), and executing step (4); if T is greater than or equal to T1, executing step (8); (3) delay time D1 (i.e., the first delay time); (4) opening the bypass valve, and starting the electric heating (i.e., the heating method of the exhaust heating system is electric heating) to heat, so as to reach the TWC transcendental temperature as soon as possible and improve the TWC conversion efficiency; (5) during the heating process, determining whether T is greater than T1+a (a is a calibration value); if T is less than or equal to T1+a, continuing the heating; (6) if T is greater than T1+a, determining whether T is less than T1-b (b is a calibration value); if T is less than T1-b, continuing the heating; if T is greater than or equal to T1-b (it can be considered that T has reached the transcendental temperature), executing step (8); (8) closing the bypass valve, and stopping the electric heating.

[0079] S204: When it is detected that the operating condition is in the second state, the bypass valve is opened with a delay according to the second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter through the exhaust bypass line, and the natural gas nozzle is controlled to spray natural gas into the exhaust gas in the exhaust bypass line, so as to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range.

[0080] Among them, controlling the natural gas nozzle to inject natural gas into the exhaust gas in the exhaust bypass pipe can reduce the excess air coefficient (when the excess air coefficient is reduced, the difference between the reduced Lambda and Lambda=1 will be shortened), so that the speed at which the conversion efficiency of the three-way catalytic converter recovers to a specific range is increased.

[0081] It should be noted that, according to the second delay time, the delayed opening of the bypass valve of the exhaust bypass pipeline can eliminate the premature gas filling behavior caused by the detection deviation of the exhaust oxygen content, and ensure that the gas filling behavior is performed when the operating condition is in the second state.

[0082] Optionally, during the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline, the change of the excess air coefficient is monitored in real time. When it is detected that the changed excess air coefficient meets the second preset threshold, the bypass valve is closed and the natural gas nozzle is controlled to stop injecting natural gas.

[0083] It is understandable that by controlling the natural gas nozzle to spray natural gas into the exhaust gas in the exhaust bypass line, the excess air coefficient will decrease. By monitoring the changes in the excess air coefficient in real time, when the changed excess air coefficient meets the second preset threshold, it can be determined that the conversion efficiency of the three-way catalytic converter can be restored to a specific range within a controllable time, and there is no need to add gas to the exhaust gas. Therefore, the bypass valve is closed and the natural gas nozzle is controlled to stop spraying natural gas to save energy consumption.

[0084] In some examples, the implementation logic of controlling the natural gas nozzle to perform gas filling can be found in Figure 4 The steps shown are as follows: (1) monitoring the front oxygen sensor signal (i.e., exhaust oxygen content); (2) based on the exhaust oxygen content, determining whether the natural gas engine is in a gas cut-off state (i.e., a second state); if the natural gas engine is in a gas cut-off state, executing step (3); otherwise executing step (7); (3) delay time D2 (i.e., a second delay time); (4) the bypass valve is opened, and the bypass gas nozzle (i.e., the natural gas nozzle) starts to spray; (5) during the gas filling process, determining whether Lambda is less than 1-d (d is a calibration value); if Lambda is less than 1-d, continuing to fill with gas; (6) if Lambda is greater than or equal to 1-d, determining whether Lambda is greater than 1+e (e is a calibration value); if Lambda is greater than 1+e, continuing to fill with gas; if Lambda is less than or equal to 1+e, executing step (7); (7) the bypass valve is closed, and the bypass gas nozzle stops spraying.

[0085] It should be emphasized that the first calibration temperature, the first delay time, the second delay time, the first preset threshold value, and the second preset threshold value are calibration quantities, which can be calibrated on the engine test bench according to the natural gas engine and TWC status. They are mainly used for the natural gas engine when it is cold started or exits the gas cut-off state. The CH4 and NOx emissions after catalysis by the three-way catalytic converter have no obvious peaks, so that the overall conversion efficiency is significantly improved.

[0086] It can be understood that by determining whether the natural gas engine is in the first state and the second state, the exhaust heating system and the natural gas nozzle can be applied to greatly improve the control of the exhaust temperature (i.e., the outlet temperature), so that the TWC conversion efficiency can be quickly restored to a specific range, thereby improving the overall conversion efficiency. The control strategy logic is simple and the thinking is clear. Through simple experiments, the calibration of various data (such as the first calibration temperature T1, the first delay time D1, the second delay time D2, the first preset threshold, the second preset threshold, a, b, d, e) can be completed.

[0087] The process shown in S201-S204 above uses an exhaust heating system, a natural gas nozzle and an exhaust bypass line to solve the problem of low TWC conversion efficiency during cold start and low exhaust temperature of the natural gas engine, greatly improves the control of exhaust temperature (i.e., the outlet temperature of the three-way catalytic converter), and when the natural gas engine is in a gas cut-off condition, it can ensure that the TWC conversion efficiency can be quickly restored to a specific range, effectively improving the overall conversion efficiency.

[0088] like Figure 5 , which is a schematic diagram of the architecture of a natural gas engine thermal management device provided in an embodiment of the present application, including the units shown below.

[0089] The parameter monitoring unit 100 is used to monitor the exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalytic converter of the after-treatment system in real time when the natural gas engine is running stably.

[0090] The operating condition identification unit 200 is used to determine the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content.

[0091] Optionally, the operating condition identification unit 200 is specifically used to: if the outlet temperature is less than the first calibration temperature, determine that the operating condition of the natural gas engine is in the first state; if the exhaust oxygen content is less than the first calibration concentration, determine that the operating condition of the natural gas engine is in the second state.

[0092] The heating control unit 300 is used to, when it is detected that the operating condition is in the first state, delay the opening of the bypass valve of the exhaust bypass line according to the first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter through the exhaust bypass line, and control the exhaust heating system to heat the exhaust gas in the exhaust bypass line to improve the conversion efficiency of the three-way catalytic converter; the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value.

[0093] Optionally, the heating control unit 300 is specifically used to: monitor the change of the outlet temperature in real time during the process of controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline; when it is detected that the changed outlet temperature meets the first preset threshold value, close the bypass valve and control the exhaust heating system to stop heating.

[0094] The gas filling control unit 400 is used to delay opening of the bypass valve according to a second delay time when it is detected that the operating condition is in the second state, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter through the exhaust bypass pipeline, and control the natural gas nozzle to spray natural gas into the exhaust gas in the exhaust bypass pipeline to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range; the second state indicates that the gas of the natural gas engine is cut off.

[0095] Optionally, the gas filling control unit 400 is specifically used to: monitor the change of the excess air coefficient in real time during the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline; when it is detected that the changed excess air coefficient meets the second preset threshold value, close the bypass valve and control the natural gas nozzle to stop injecting natural gas.

[0096] The above-mentioned units use an exhaust heating system, a natural gas nozzle and an exhaust bypass line to solve the problem of low TWC conversion efficiency during cold start and low exhaust temperature of the natural gas transmitter, greatly improve the control of exhaust temperature (i.e., the outlet temperature of the three-way catalytic converter), and when the natural gas engine is in a gas cut-off condition, ensure that the TWC conversion efficiency can be quickly restored to a specific range, thereby effectively improving the overall conversion efficiency.

[0097] In addition, the functions described above in the embodiments of the present application may be at least partially performed by one or more hardware logic components. For example, without limitation, exemplary types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), and the like.

[0098] Although several specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present application. Certain features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0099] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of disclosure involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other to form a technical solution.

Claims

1. A natural gas engine thermal management method, characterized in that: A post-processor system applied to a newly added exhaust bypass pipeline, wherein the exhaust bypass pipeline is preset with a natural gas nozzle and an exhaust heating system, and the method comprises: When the natural gas engine is running stably, the exhaust oxygen content, excess air coefficient and outlet temperature of the three-way catalytic converter of the post-treatment system are monitored in real time; Determining the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content; When it is detected that the operating condition is in a first state, the bypass valve of the exhaust bypass pipeline is opened with a delay according to a first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the exhaust heating system is controlled to heat the exhaust gas in the exhaust bypass pipeline to improve the conversion efficiency of the three-way catalytic converter; the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value; When it is detected that the operating condition is in the second state, the bypass valve is opened with a delay according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and the natural gas nozzle is controlled to spray natural gas into the exhaust gas in the exhaust bypass pipeline, so as to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range; the second state indicates that the gas of the natural gas engine is cut off.

2. The method according to claim 1, characterized in that The method further comprises: In the process of controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the outlet temperature; When it is detected that the changed outlet temperature meets the first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

3. The method according to claim 1, characterized in that The method further comprises: In the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the excess air coefficient; When it is detected that the changed excess air coefficient meets the second preset threshold, the bypass valve is closed, and the natural gas nozzle is controlled to stop injecting natural gas.

4. The method according to claim 1, characterized in that: Determining the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content includes: If the outlet temperature is less than a first calibration temperature, determining that the operating condition of the natural gas engine is in a first state; If the exhaust oxygen content is less than the first calibrated concentration, it is determined that the operating condition of the natural gas engine is in the second state.

5. A thermal management device for a natural gas engine, characterized in that: include: The parameter monitoring unit is used to monitor the exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalytic converter of the after-treatment system in real time when the natural gas engine is running stably; An operating condition identification unit, used to determine the operating condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content; a heating control unit, for, when detecting that the operating condition is in a first state, delaying opening of a bypass valve of an exhaust bypass pipeline according to a first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and controlling an exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, so as to improve the conversion efficiency of the three-way catalytic converter; the first state indicates that the conversion efficiency of the three-way catalytic converter is less than a specified value; The gas filling control unit is used for, when it is detected that the operating condition is in the second state, delaying the opening of the bypass valve according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalytic converter via the exhaust bypass pipeline, and controlling the natural gas nozzle to spray natural gas into the exhaust gas in the exhaust bypass pipeline, so as to increase the speed at which the conversion efficiency of the three-way catalytic converter is restored to a specific range; the second state indicates that the gas of the natural gas engine is cut off.

6. The device according to claim 5, characterized in that The heating control unit is also used for: In the process of controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the outlet temperature; When it is detected that the changed outlet temperature meets the first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

7. The device according to claim 5, characterized in that The gas filling control unit is also used for: In the process of the natural gas nozzle injecting natural gas into the exhaust gas in the exhaust bypass pipeline, real-time monitoring of the change of the excess air coefficient; When it is detected that the changed excess air coefficient meets the second preset threshold, the bypass valve is closed, and the natural gas nozzle is controlled to stop injecting natural gas.

8. The device according to claim 5, characterized in that The operating condition identification unit is specifically used for: If the outlet temperature is less than a first calibration temperature, determining that the operating condition of the natural gas engine is in a first state; If the exhaust oxygen content is less than the first calibrated concentration, it is determined that the operating condition of the natural gas engine is in the second state.

9. A post-processing system, characterized in that: include: Natural gas engine, electronic control unit, exhaust gas recirculation system, exhaust pipe, exhaust bypass line, bypass valve, natural gas nozzle, exhaust heating system, front oxygen sensor, three-way catalytic converter, rear oxygen sensor and temperature sensor; Wherein, the exhaust port of the natural gas engine is respectively connected to the intake ports of the exhaust gas recirculation system, the exhaust pipe, and the exhaust bypass pipeline; The air inlet of the exhaust bypass pipeline is provided with the bypass valve, the main body of the exhaust bypass pipeline is provided with the natural gas nozzle and the exhaust heating system, and the air outlet of the exhaust bypass pipeline is connected to the three-way catalytic converter; The front oxygen sensor is preset on the air inlet of the three-way catalytic converter, and the rear oxygen sensor and the temperature sensor are respectively preset on the air outlet of the three-way catalytic converter; The electronic control unit is respectively connected to the natural gas engine, the bypass valve, the natural gas nozzle, the exhaust heating system, the front oxygen sensor, the rear oxygen sensor and the temperature sensor by wired communication, and the electronic control unit is used to execute the natural gas engine thermal management method described in any one of claims 1 to 4 above.

10. The post-treatment system according to claim 9, characterized in that: The front oxygen sensor is used to send the exhaust oxygen content to the electronic control unit, the temperature sensor is used to send the outlet temperature to the electronic control unit, and the rear oxygen sensor is used to send the purified exhaust oxygen content to the electronic control unit, so that the electronic control unit calculates the corresponding excess air coefficient based on the purified exhaust oxygen content.

Images