Natural gas engine thermal management method, device, and aftertreatment system

Abstract

The application discloses a natural gas engine thermal management method, device and aftertreatment system. The method comprises the following steps: when the natural gas engine is in stable operation, the oxygen content of exhaust gas, the excess air coefficient and the outlet temperature of a three-way catalyst are monitored in real time; based on the outlet temperature and the oxygen content of exhaust gas, the operating condition of the natural gas engine is determined; when it is detected that the operating condition is in a first state, a bypass valve of an exhaust gas 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 catalyst through the exhaust gas bypass pipeline, and an exhaust gas heating system is controlled to heat, so as to improve the conversion efficiency of the three-way catalyst; when it is detected that the operating condition is in a 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 catalyst through the exhaust gas bypass pipeline, and a natural gas nozzle is controlled to spray natural gas, so as to improve the speed of the conversion efficiency of the three-way catalyst to recover to a specific interval.

Description

Technical Field

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

[0002] As future emissions regulations become increasingly stringent, NOx (nitrogen oxides) and CH4 (methane) emission limits will be lowered. Currently, natural gas engines emit high levels of cold CH4 emissions, making reducing these emissions a key technology for the next generation of emissions technology. To meet these increasingly stringent regulations, a heated aftertreatment system for combustible gas injection is being designed to improve conversion efficiency during cold starts and low exhaust temperatures (i.e., low exhaust temperatures). This increases outlet temperatures and allows for rapid recovery of Lambda (the ratio of actual to theoretical air intake in the engine cylinder) after gas shutoff conditions such as reverse engine operation. A heated TWC (three-way catalytic converter) aftertreatment system will be a key technical measure.

[0003] In the prior art, when the engine is cold-started, the conversion efficiency is low before the TWC reaches the ignition temperature (specifically, the temperature at which the TWC's CH4 conversion efficiency reaches 50%). At this time, the TWC lacks the ability to convert exhaust gas. Moreover, when the engine and its exhaust system are flooded with oxygen, the TWC deviates significantly from the conversion efficiency window. If the in-cylinder nozzle is used for enrichment, there will be a large air path delay, and it will take a long time to enrich again 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, the purpose of which is 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-processing system with a newly added exhaust bypass line, wherein the exhaust bypass line is pre-installed with a natural gas nozzle and an exhaust heating system. 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 an 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 of the natural gas engine is in the first state, opening the bypass valve of the exhaust bypass pipeline in a delayed manner according to a first delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalyst via the exhaust bypass pipeline, and controlling the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, so as to improve the conversion efficiency of the three-way catalyst; the first state represents that the conversion efficiency of the three-way catalyst is less than a specified value;

[0011] when it is detected that the operating condition of the natural gas engine is in the second state, opening the bypass valve in a delayed manner according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalyst 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 improve the speed of the conversion efficiency of the three-way catalyst to recover to a specific interval; the second state represents that the fuel gas of the natural gas engine is cut off.

[0012] Optionally, the method further comprises:

[0013] monitoring 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;

[0014] when it is detected that the changed outlet temperature meets a first preset threshold, closing the bypass valve and controlling the exhaust heating system to stop heating.

[0015] Optionally, the method further comprises:

[0016] monitoring the change of the excess air coefficient in real time during the process of the natural gas nozzle spraying natural gas into the exhaust gas in the exhaust bypass pipeline;

[0017] when it is detected that the changed excess air coefficient meets a second preset threshold, closing the bypass valve and controlling the natural gas nozzle to stop spraying natural gas.

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

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

[0020] if the oxygen content of the exhaust gas is greater than a first calibration concentration, determining that the operating condition of the natural gas engine is in the second state.

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

[0022] A parameter monitoring unit is configured to monitor, in real time, an exhaust oxygen content, an excess air coefficient, and an outlet temperature of a three-way catalyst of the aftertreatment system when the natural gas engine is in stable operation.

[0023] A working condition identifying unit is configured to determine a working condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content.

[0024] A heating control unit is configured to, when detecting that the working condition is in a first state, open a bypass valve of an exhaust bypass pipeline in a first delay time, so that the exhaust of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and control an exhaust heating system to heat the exhaust in the exhaust bypass pipeline, so as to improve conversion efficiency of the three-way catalyst; the first state represents that the conversion efficiency of the three-way catalyst is less than a specified value.

[0025] A gas injection control unit is configured to, when detecting that the working condition is in a second state, open the bypass valve in a second delay time, so that the exhaust of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and control a natural gas nozzle to inject natural gas into the exhaust in the exhaust bypass pipeline, so as to improve a speed of recovering the conversion efficiency of the three-way catalyst to a specific range; the second state represents that the natural gas engine is in a gas cut-off state.

[0026] Optionally, the heating control unit is further configured to:

[0027] monitor, in real time, a change in the outlet temperature during the heating of the exhaust heating system to the exhaust in the exhaust bypass pipeline.

[0028] when detecting that the changed outlet temperature meets a first preset threshold, close the bypass valve and control the exhaust heating system to stop heating.

[0029] Optionally, the gas injection control unit is further configured to:

[0030] monitor, in real time, a change in the excess air coefficient during the injection of the natural gas nozzle to the exhaust in the exhaust bypass pipeline.

[0031] when detecting that the changed excess air coefficient meets a second preset threshold, close the bypass valve and control the natural gas nozzle to stop injecting natural gas.

[0032] Optionally, the working condition identifying unit is specifically configured to:

[0033] if the outlet temperature is less than a first calibration temperature, determine that the working condition of the natural gas engine is in the first state.

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

[0035] A post-processing system, comprising:

[0036] A natural gas engine, an electronic control unit, an exhaust gas recirculation system, an exhaust pipe, an exhaust bypass pipe, a bypass valve, a natural gas nozzle, an exhaust heating system, a front oxygen sensor, a three-way catalyst, a rear oxygen sensor, and a temperature sensor;

[0037] The exhaust port of the natural gas engine is connected to the air inlet of each of the exhaust gas recirculation system, the exhaust pipe, and the exhaust bypass pipe, respectively;

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

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

[0040] The electronic control unit is in wired communication connection with 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, respectively, 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 gas 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 gas oxygen content to the electronic control unit, so that the electronic control unit calculates the corresponding excess air coefficient based on the purified exhaust gas oxygen content.

[0042] The technical scheme provided in the application, when the natural gas engine is stably running, the exhaust oxygen content, the excess air coefficient and the outlet temperature of the three-way catalyst are monitored in real time. Based on the outlet temperature and the exhaust oxygen content, the running condition of the natural gas engine is determined. When it is detected that the running 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 of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and the exhaust heating system is controlled to heat, so as to improve the conversion efficiency of the three-way catalyst. When it is detected that the running condition is in a second state, the bypass valve is opened with a delay according to a second delay time, so that the 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 as to improve the speed of the conversion efficiency of the three-way catalyst to recover to a specific interval. The application applies the exhaust heating system, the natural gas nozzle and the exhaust bypass pipeline, solves the problem of low TWC conversion efficiency of the natural gas engine during cold start and low exhaust temperature, greatly improves the control of the exhaust temperature (i.e. the outlet temperature of the three-way catalyst), and when the natural gas engine is in the gas cut-off condition, the TWC conversion efficiency can be quickly recovered to a specific interval, effectively improving the overall conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0044] Figure 1 An architecture schematic diagram of a post-processing system provided for the embodiments of the present application;

[0045] Figure 2 A flowchart of a natural gas engine thermal management method provided for the embodiments of the present application;

[0046] Figure 3 A schematic diagram of a heating control logic provided for the embodiments of the present application;

[0047] Figure 4 A schematic diagram of a gas filling control logic provided for the embodiments of the present application;

[0048] Figure 5 An architecture schematic diagram of a natural gas engine thermal management device provided for the embodiments of the present application. DETAILED DESCRIPTION

[0049] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present application.

[0050] In the present application, the relational terms such as first and second and the like are used only to differentiate one entity or operation from another, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a", "comprising", or "includes" does not, without more restrictions, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0051] The applicant finds that the heat source of the existing natural gas engine aftertreatment system relies on engine exhaust, and when the engine is cold started, the three-way catalyst needs a long time to reach the light-off temperature, and the engine exhaust temperature is reduced for a long time under low load conditions, which affects the conversion efficiency of the three-way catalyst; after the existing natural gas engine reverse drag condition ends, the three-way catalyst is almost exposed to the atmosphere, deviating from the conversion efficiency window, and there is a large gas delay in relying on the in-cylinder natural gas nozzle to restore the excess air coefficient after the end of the reverse drag and gas cut-off condition, affecting the overall conversion efficiency.

[0052] Therefore, the embodiment of the present application provides an aftertreatment system suitable for the use scenario of a natural gas engine to improve the TWC conversion efficiency of the natural gas engine aftertreatment process.

[0053] As shown in FIG. 1, an architecture schematic diagram of an aftertreatment system provided by an embodiment of the present application includes the following components. Figure 1

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

[0055] The exhaust port of the natural gas engine 1 is connected to the respective gas inlets 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 pipe 5 is provided with a bypass valve 6 , the main body of the exhaust bypass pipe 5 is provided with a natural gas nozzle 7 and an exhaust heating system 8 , and the air outlet of the exhaust bypass pipe 5 is connected to the 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 respectively preset on the air outlet 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 through wired communication.

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

[0060] In some examples, the heating methods provided by the exhaust heating system 8 include but are 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 (understood as the oxygen concentration in the exhaust) in real time, 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 after treatment by the three-way catalytic converter 10 (the oxygen concentration in the purified exhaust) 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. As a result, when the natural gas engine ends the reverse towing and other gas cut-off conditions, 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 , which is a flow chart of a natural gas engine thermal management method provided in an embodiment of the present application, can be executed based on an ECU (Electronic Control Unit), and includes the following steps.

[0065] S201: Real-time monitoring of exhaust oxygen content, excess air coefficient, and outlet temperature of the three-way catalyst when the natural gas engine is stably running.

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

[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 running condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content.

[0069] Based on the outlet temperature and the exhaust oxygen content, the running condition that affects the conversion efficiency of the three-way catalyst can be determined, such as the conversion efficiency of the three-way catalyst being less than a specified value (i.e., the TWC conversion efficiency is low) due to the cold start of the natural gas engine and the low exhaust temperature, or the speed of the TWC conversion efficiency recovering to a specific interval (i.e., the conversion efficiency interval corresponding to Lambda = 1 when Lambda is restored) being reduced due to the gas cut-off condition of the natural gas engine ending the reverse drag.

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

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

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

[0073] S203: When it is detected that the running condition is in the first state, open the bypass valve of the exhaust bypass pipeline according to a first delay time, so that the exhaust of the natural gas engine flows into the three-way catalyst through the exhaust bypass pipeline, and control the exhaust heating system to heat the exhaust in the exhaust bypass pipeline to improve the conversion efficiency of the three-way catalyst.

[0074] Controlling the exhaust heating system to heat the exhaust in the exhaust bypass pipeline can improve the outlet temperature, so that the conversion efficiency of the three-way catalyst is improved.

[0075] It should be noted that according to the first delay time, the bypass valve opening the exhaust bypass pipeline in time can eliminate the advance 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, during the process of controlling the exhaust heating system to heat the exhaust in the exhaust bypass pipeline, the change of the outlet temperature is monitored in real time, and when the changed outlet temperature meets the first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

[0077] It can be understood that when the exhaust heating system is controlled to heat the exhaust in the exhaust bypass pipeline, the outlet temperature will rise, and by monitoring the change of the outlet temperature in real time, when the changed outlet temperature meets the first preset threshold, that is, the conversion efficiency of the TWC has recovered (that is, the TWC conversion efficiency is greater than or equal to a specified value), there is no need to heat the exhaust, so the bypass valve is closed, and the exhaust heating system is controlled to stop heating, so as to save energy consumption.

[0078] In some examples, the implementation logic of controlling the exhaust heating system to perform heating work can refer to the steps shown in FIG. 8. Figure 3 The outlet temperature T of the TWC is monitored, it is judged whether T is lower than T1 (that is, the first calibration temperature), if T is less than T1, it is determined that the operating condition of the natural gas engine is in the TWC low conversion efficiency state (that is, the first state), and step (4) is performed, if T is greater than or equal to T1, step (8) is performed, delay time D1 (that is, the first delay time) is determined, the bypass valve is opened, and the electric heating (that is, the heating mode of the exhaust heating system is electric heating) is started to heat, so as to reach the TWC superheat temperature as soon as possible and improve the TWC conversion efficiency, during the heating process, it is judged whether T is greater than T1+a (a is a calibration value), if T is less than or equal to T1+a, the heating is continued, if T is greater than T1+a, it is judged whether T is less than T1-b (b is a calibration value), if T is less than T1-b, the heating is continued, if T is greater than or equal to T1-b (T can be considered to have reached the superheat temperature), step (8) is performed, the bypass valve is closed, and the electric heating stops heating.

[0079] S204: When it is detected that the operating condition is in the second state, the bypass valve is opened in time according to the second delay time, so that the exhaust of the natural gas engine flows into the TWC through the exhaust bypass pipeline, and the natural gas nozzle sprays natural gas into the exhaust in the exhaust bypass pipeline, so as to improve the speed of restoring the conversion efficiency of the TWC to a specific interval.

[0080] The natural gas nozzle sprays natural gas into the exhaust bypass pipeline, which can reduce the excess air coefficient (the difference between the reduced Lambda and Lambda = 1 is shortened), so that the conversion efficiency of the three-way catalyst recovers to a specific interval at a higher speed.

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

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

[0083] It can be understood that the natural gas nozzle sprays natural gas into the exhaust bypass pipeline, which can reduce the excess air coefficient, and by monitoring the change of the excess air coefficient in real time, it can be determined that the conversion efficiency of the three-way catalyst can recover to a specific interval within a controllable time when the changed excess air coefficient meets the second preset threshold, without the need for further gas injection to the exhaust gas. Therefore, the bypass valve is closed, and the natural gas nozzle is controlled to stop spraying natural gas, so as to save energy consumption.

[0084] In some examples, the implementation logic of controlling the natural gas nozzle to perform the gas injection work can refer to the steps shown in FIG. 8. Figure 4 The steps shown in FIG. 8 are as follows: (1) monitoring the front oxygen sensor signal (i.e. the oxygen content of the exhaust gas); (2) judging whether the natural gas engine is in the gas cut-off state (i.e. the second state) based on the oxygen content of the exhaust gas, if the natural gas engine is in the gas cut-off state, step (3) is performed, otherwise step (7) is performed; (3) delay time D2 (i.e. second delay time); (4) the bypass valve is opened, and the bypass gas nozzle (i.e. natural gas nozzle) starts to spray; (5) during the gas injection process, it is judged whether Lambda is less than 1-d (d is a calibration value), if Lambda is less than 1-d, the gas injection is continued; (6) if Lambda is greater than or equal to 1-d, it is judged whether Lambda is greater than 1+e (e is a calibration value), if Lambda is greater than 1+e, the gas injection is continued, if Lambda is less than or equal to 1+e, step (7) is performed; (7) the bypass valve is closed, and the bypass gas nozzle stops spraying.

[0085] It should be emphasized that the first calibration temperature, first delay time, second delay time, first preset threshold value, and 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 to ensure that when the natural gas engine is cold started or exits the gas shut-off state, the CH4 and NOx emissions after catalysis by the three-way catalytic converter have no obvious peaks, thereby significantly improving the overall conversion efficiency.

[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 are applied, which can 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, using an exhaust heating system, a natural gas nozzle, and an exhaust bypass line, solves the problem of low TWC conversion efficiency during cold start and low exhaust temperature of the natural gas engine. It greatly improves the control of exhaust temperature (i.e., the outlet temperature of the three-way catalytic converter) and ensures that the TWC conversion efficiency can be quickly restored to a specific range when the natural gas engine is in a gas cut-off condition, 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 greater 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 configured to, when detecting that the operating condition is in the first state, open the bypass valve of the exhaust bypass pipeline in a delayed manner according to a first delay time, so that the exhaust gas of the natural gas engine flows into the TWC via the exhaust bypass pipeline, and control the exhaust heating system to heat the exhaust gas in the exhaust bypass pipeline, so as to improve the conversion efficiency of the TWC; the first state represents that the conversion efficiency of the TWC is less than a specified value.

[0093] Optionally, the heating control unit 300 is specifically configured 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; and when detecting that the changed outlet temperature meets a first preset threshold, close the bypass valve and control the exhaust heating system to stop heating.

[0094] The gas filling control unit 400 is configured to, when detecting that the operating condition is in the second state, open the bypass valve in a delayed manner according to a second delay time, so that the exhaust gas of the natural gas engine flows into the TWC via the exhaust bypass pipeline, and control the natural gas nozzle to spray natural gas into the exhaust gas in the exhaust bypass pipeline, so as to improve the speed of restoring the conversion efficiency of the TWC to a specific interval; the second state represents that the fuel gas of the natural gas engine is cut off.

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

[0096] The above-mentioned various units apply the exhaust heating system, the natural gas nozzle and the exhaust bypass pipeline, solve the problem of low TWC conversion efficiency of the natural gas engine during cold start and low exhaust temperature, greatly improve the control of the exhaust temperature (i.e. the outlet temperature of the TWC), and when the natural gas engine is in the fuel gas cut-off condition, the TWC conversion efficiency can be quickly restored to a specific interval, and the overall conversion efficiency is effectively improved.

[0097] In addition, the functions described above in the embodiments of the present application can be performed at least in part by one or more hardware logic components. For example, non-limiting examples of exemplary types of hardware logic components that can be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system on a chip (SOCs), complex programmable logic devices (CPLDs), and the like.

[0098] While several inventive embodiments have been described above, it should be appreciated that many modifications can be made of these embodiments in light of the above disclosure. Therefore, the disclosed embodiments are not intended to limit the scope of the application to the particular embodiments disclosed herein but can be practiced with modifications and changes by those having ordinary skill in the art without departing from the scope of the following claims.

[0099] The above description is merely illustrative of the application and the application should not be limited to the specific embodiments that have been described, which are presented as examples. Various modifications within the scope of the application can be made by those skilled in the art, and the application is not intended to be limited to the embodiments described herein, excluding only other embodiments encompassed within the spirit or scope of the application.

Claims

1. A natural gas engine thermal management method, characterized by, The application relates to a method for controlling a post-processing system applied to an exhaust bypass pipeline, wherein a natural gas nozzle and an exhaust heating system are preset on the exhaust bypass pipeline, and the method comprises the following steps: When the natural gas engine is in stable operation, the exhaust oxygen content, the excess air coefficient and the outlet temperature of the three-way catalyst of the post-processing system are monitored in real time; Based on the outlet temperature and the exhaust oxygen content, the operation condition of the natural gas engine is determined; When the operation condition is detected to be in a first state, the bypass valve of the exhaust bypass pipeline is opened in a delayed manner according to a first delay time, so that the 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 heat the exhaust in the exhaust bypass pipeline, so as to improve the conversion efficiency of the three-way catalyst; the first state represents that the conversion efficiency of the three-way catalyst is less than a specified value; When the operation condition is detected to be in a second state, the bypass valve is opened in a delayed manner according to a second delay time, so that the 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 into the exhaust in the exhaust bypass pipeline, so as to improve the speed of restoring the conversion efficiency of the three-way catalyst to a specific interval; the second state represents that the fuel gas of the natural gas engine is cut off.

2. The method of claim 1, wherein, The method further comprises the following steps: During the process of controlling the exhaust heating system to heat the exhaust in the exhaust bypass pipeline, the change of the outlet temperature is monitored in real time; When the changed outlet temperature meets a first preset threshold, the bypass valve is closed, and the exhaust heating system is controlled to stop heating.

3. The method of claim 1, wherein, The method further comprises the following steps: During the process of spraying natural gas into the exhaust in the exhaust bypass pipeline by the natural gas nozzle, the change of the excess air coefficient is monitored in real time; When the changed excess air coefficient meets a second preset threshold, the bypass valve is closed, and the natural gas nozzle is controlled to stop spraying natural gas.

4. The method of claim 1, wherein, Based on the outlet temperature and the exhaust oxygen content, the operation condition of the natural gas engine is determined, which comprises the following steps: If the outlet temperature is less than a first calibration temperature, it is determined that the operation condition of the natural gas engine is in the first state; If the exhaust oxygen content is greater than a first calibration concentration, it is determined that the operation condition of the natural gas engine is in the second state.

5. A natural gas engine thermal management device, characterized by, The method further comprises the following steps: A parameter monitoring unit is used for monitoring the exhaust oxygen content, the excess air coefficient and the outlet temperature of the three-way catalyst of the post-processing system in real time when the natural gas engine is in stable operation; An operation condition identification unit is used for determining the operation condition of the natural gas engine based on the outlet temperature and the exhaust oxygen content. The heating control unit is configured to, when detecting that the operating condition is in a first state, open a bypass valve of an exhaust bypass pipeline in a delayed manner according to a first delay time, so that the exhaust gas of the natural gas engine flows into a three-way catalyst via the exhaust bypass pipeline, and control 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 catalyst; the first state represents that the conversion efficiency of the three-way catalyst is less than a specified value. The gas injection control unit is configured to, when detecting that the operating condition is in a second state, open the bypass valve in a delayed manner according to a second delay time, so that the exhaust gas of the natural gas engine flows into the three-way catalyst via the exhaust bypass pipeline, and control a natural gas nozzle to inject natural gas into the exhaust gas in the exhaust bypass pipeline, so as to improve the speed of the conversion efficiency of the three-way catalyst to return to a specific range; the second state represents that the fuel gas of the natural gas engine is cut off.

6. The apparatus of claim 5, wherein, The heating control unit is further configured 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 detecting that the changed outlet temperature meets a first preset threshold, close the bypass valve and control the exhaust heating system to stop heating.

7. The apparatus of claim 5, wherein, The gas injection control unit is further configured 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 detecting that the changed excess air coefficient meets a second preset threshold, close the bypass valve and control the natural gas nozzle to stop injecting natural gas.

8. The apparatus of claim 5, wherein, The condition identification unit is specifically configured to: if the outlet temperature is less than a first calibration temperature, determine that the operating condition of the natural gas engine is in the first state; if the oxygen content of the exhaust gas is greater than a first calibration concentration, determine that the operating condition of the natural gas engine is in the second state.

9. An aftertreatment system characterized by, The system comprises: a natural gas engine, an electronic control unit, an exhaust gas recirculation system, an exhaust pipe, an exhaust bypass pipeline, a bypass valve, a natural gas nozzle, an exhaust heating system, a front oxygen sensor, a three-way catalyst, a rear oxygen sensor and a temperature sensor; wherein the exhaust port of the natural gas engine is connected to the respective gas inlets of the exhaust gas recirculation system, the exhaust pipe and the exhaust bypass pipeline; the gas 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 gas outlet of the exhaust bypass pipeline is connected to the three-way catalyst; the front oxygen sensor is preset on the gas inlet of the three-way catalyst, and the rear oxygen sensor and the temperature sensor are respectively preset on the gas outlet of the three-way catalyst; the electronic control unit is in wired communication connection with 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, and the electronic control unit is configured to execute the natural gas engine thermal management method of any one of claims 1-4.

10. The aftertreatment system of claim 9, wherein, The front oxygen sensor is configured to send exhaust gas oxygen content to the electronic control unit, the temperature sensor is configured to send outlet temperature to the electronic control unit, and the rear oxygen sensor is configured to send purified exhaust gas oxygen content to the electronic control unit, so that the electronic control unit calculates a corresponding excess air coefficient based on the purified exhaust gas oxygen content.

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