Natural gas extreme working condition catalyst inlet temperature increasing device and control method

Abstract

The invention discloses a natural gas extreme working condition catalytic converter inlet temperature rise control method, relates to an internal combustion engine, and solves the technical problems that an existing heavy national 7 natural gas engine is thin in inlet gas and insufficient in combustion under the extreme working condition, and the catalytic converter inlet temperature is difficult to reach the standard. The control method comprises the steps that an electric supercharger is arranged between an air filter and a supercharger, and an exhaust throttle valve is arranged between a catalyst and the supercharger; and according to the collected air inlet pressure, the catalytic converter inlet temperature, the rotating speed and the real-time altitude, the engine working condition is judged, and when it is judged that the engine working condition is the high-altitude and small-air-inlet-pressure working condition, a cooperative control temperature increasing strategy is triggered to control an electric supercharger and an exhaust throttle valve to increase the catalytic converter inlet temperature. The invention further discloses a natural gas extreme working condition catalyst inlet temperature rise control system. The temperature increasing efficiency and stability are improved, and the requirement for long-distance operation of the heavy natural gas engine is met.

Description

Technical Field

[0001] This invention relates to internal combustion engines, and more specifically, to a device and control method for increasing the inlet temperature of a natural gas catalytic converter under extreme operating conditions. Background Technology

[0002] With the release of dual-carbon targets, the transportation industry, as a major contributor to carbon emissions, plays a crucial role in emission reduction. In 2018, the China VI emission standards for heavy-duty engines were implemented. As the deadlines for internal combustion engine technology and dual-carbon targets approach, the China VII emission standards for heavy-duty engines are also imminent. To meet China VII emission standards, various internal combustion engine manufacturers have conducted technical research, focusing on key aspects such as emission control and catalytic converter thermal management. Catalytic converter temperature plays a critical role in catalytic converter efficiency. Under the increasingly stringent China VII emission standards, catalytic converter temperature thermal management is a critical aspect, especially under conditions where engine exhaust temperatures are low, such as idling and low load. How to adapt to extreme high-altitude conditions and meet emission requirements is a key research topic that requires focused attention. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a device and control method for increasing the inlet temperature of a natural gas catalyst under extreme operating conditions, in order to address the shortcomings of the existing technology. This solves the existing technical problems of lean air intake, incomplete combustion, and difficulty in achieving the required catalyst inlet temperature for heavy-duty China VII natural gas engines under extreme operating conditions.

[0004] The present invention discloses a method for controlling the catalytic converter inlet temperature under extreme natural gas operating conditions. The method involves installing an electric turbocharger between the air filter and the turbocharger, and an exhaust throttle valve between the catalytic converter and the turbocharger. The method collects the engine's intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude. Based on these parameters, the engine operating condition is determined. When the engine operating condition is determined to be high altitude and low intake pressure, a coordinated control temperature-boosting strategy is triggered to increase the catalytic converter inlet temperature.

[0005] The system acquires the operating status of the electric turbocharger and the exhaust throttle valve when the coordinated control temperature-boosting strategy is executed. If the operating status of the electric turbocharger or the exhaust throttle valve is in a fault state, the backup temperature-boosting strategy is triggered. The target temperature of the catalyst inlet after the implementation of the coordinated control temperature-raising strategy is obtained, and a closed-loop control strategy is triggered based on the target temperature of the catalyst inlet to adjust the coordinated control temperature-raising strategy.

[0006] As a further improvement, the collaborative control temperature-raising strategy is as follows: Control the electric supercharger to increase the intake pressure to a preset first intake pressure; An intake heating module is installed at the outlet of the electric supercharger, and the intake heating module is controlled to raise the intake temperature to a preset first intake temperature. Set a first ignition advance angle retarding value, and retard the current ignition advance angle according to the first ignition advance angle retarding value; completely close the EGR valve; set a first air-fuel ratio and a second air-fuel ratio, inject into the core area of ​​the cylinder according to the first air-fuel ratio, and inject into the edge area of ​​the cylinder according to the second air-fuel ratio; Set the opening of the exhaust throttle valve to a preset first opening.

[0007] Furthermore, the method for obtaining the target catalyst inlet temperature after implementing the aforementioned collaborative control temperature-boosting strategy is as follows: Obtain the exhaust specific heat capacity, the pipe length from the throttle valve outlet to the catalytic converter inlet, the pipe heat dissipation coefficient, the ambient temperature of the engine, the exhaust pressure at the exhaust throttle valve outlet, and the turbine outlet exhaust pressure. Calculate the exhaust throttle valve opening based on the exhaust pressure at the exhaust throttle valve outlet and the turbine outlet exhaust pressure. Obtain the natural gas combustion heat release per unit time, the isobaric specific heat capacity of the EGR exhaust gas, the temperature at which the EGR exhaust gas is introduced, the isobaric specific heat capacity of the fresh air, the EGR exhaust gas mass flow rate, the fresh intake air temperature, the isobaric specific heat capacity of the turbine outlet exhaust, the total exhaust mass flow rate, the turbine output power, the isobaric specific heat capacity of the fresh air, and the fresh air mass flow rate. Calculate the exhaust throttle valve opening based on the natural gas combustion heat release per unit time... The turbocharger outlet temperature is calculated using the specific heat capacity at constant pressure of EGR exhaust gas, the temperature of EGR exhaust gas at introduction, the specific heat capacity at constant pressure of fresh air, the mass flow rate of EGR exhaust gas, the fresh intake temperature, the specific heat capacity at constant pressure of turbine outlet exhaust gas, the total exhaust mass flow rate, the turbine output power, the specific heat capacity at constant pressure of fresh air, and the mass flow rate of fresh air. The target catalytic converter inlet temperature is calculated based on the exhaust throttle valve opening, the turbocharger outlet temperature, the pipe heat dissipation coefficient, the pipe length from the throttle valve outlet to the catalytic converter inlet, the ambient temperature of the engine, and the specific heat capacity of the exhaust gas.

[0008] Furthermore, the calculation expression for the target temperature at the catalyst inlet is as follows: ; Among them, T cat,in T is the catalyst inlet temperature. turb,out Here, θ represents the turbocharger outlet temperature, and θ represents the exhaust throttle valve opening. K The heat dissipation coefficient of the pipeline. L This refers to the length of the pipe from the throttle valve outlet to the catalyst inlet. T amb The ambient temperature at which the engine operates. k This is the specific heat capacity of the exhaust gas.

[0009] Furthermore, the expression for calculating the opening degree of the exhaust throttle valve is as follows: ; in, P throttle,out The exhaust pressure at the outlet of the exhaust throttle valve. P turb,out This refers to the exhaust pressure at the turbine outlet. θ This refers to the opening degree of the exhaust throttle valve.

[0010] Furthermore, the formula for calculating the turbocharger outlet temperature is as follows: ; Among them, T turb,out The outlet temperature of the turbocharger. Q comb The heat released by the combustion of natural gas per unit time. C p，egr The specific heat capacity at constant pressure of EGR exhaust gas. T egr The temperature at which the EGR exhaust gas is introduced. C p,air The specific heat capacity at constant pressure of fresh air. m egr EGR exhaust gas mass flow rate, T air For fresh air intake temperature, C p，exh The specific heat capacity at constant pressure of the turbine outlet exhaust. m exh The total exhaust mass flow rate, W turb For turbine output power, C p，air The specific heat capacity at constant pressure of fresh air. m air This refers to the fresh air mass flow rate.

[0011] Furthermore, the backup warming strategy involves calibrating a second ignition advance angle retarding value based on the engine operating conditions, retarding the current ignition advance angle by increasing the first ignition advance angle retarding value to the second ignition advance angle retarding value, setting a third air-fuel ratio and a fourth air-fuel ratio, increasing the first air-fuel ratio to the third air-fuel ratio, and increasing the second air-fuel ratio to the fourth air-fuel ratio.

[0012] Furthermore, the closed-loop control strategy involves obtaining the ignition temperature of the catalyst, calibrating a first temperature threshold and a second temperature threshold based on the ignition temperature of the catalyst, and strengthening the collaborative control temperature-boosting strategy when the inlet temperature of the catalyst is less than the first temperature threshold. When the catalyst inlet temperature is greater than or equal to the first temperature threshold and less than the second temperature threshold, the coordinated control temperature increase strategy is maintained. When the catalyst inlet temperature is greater than or equal to the second temperature threshold, load reduction durability protection is performed.

[0013] Furthermore, the method for determining engine operating conditions based on the aforementioned intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude is as follows: Set an altitude threshold and an intake pressure threshold. When the intake pressure is less than the intake pressure threshold and the real-time altitude is greater than the altitude threshold, the engine operating condition is determined to be a high-altitude and low-intake-pressure operating condition.

[0014] A natural gas catalytic converter inlet temperature boosting control device under extreme operating conditions, the control device comprising, An electric supercharger is installed between the air filter and the supercharger to increase the intake pressure; An intake heating module is installed at the outlet of the electric supercharger to increase the intake air temperature; The exhaust throttle valve is installed between the catalytic converter and the turbocharger to control the exhaust back pressure; The multi-parameter signal acquisition module is used to acquire the engine's intake pressure, catalyst inlet temperature, speed, and real-time altitude, and output the corresponding intake pressure signal, catalyst inlet temperature signal, speed signal, and altitude signal. The ECU is used to receive the intake pressure signal, catalyst inlet temperature signal, speed signal and altitude signal, and apply the above-mentioned natural gas extreme condition catalyst inlet temperature boosting control method to control the intake heating module, electric supercharger and exhaust throttle valve to boost the catalyst inlet temperature based on the engine's intake pressure, catalyst inlet temperature, speed and real-time altitude.

[0015] Beneficial effects The advantages of this invention are: This invention addresses the problem of low exhaust temperature and excessive emissions caused by lean air intake and incomplete combustion in high-altitude regions. It involves installing an electric supercharger between the air filter and the supercharger, and an exhaust throttle valve between the catalytic converter and the supercharger. The invention collects data on engine intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude. Based on these parameters, it determines the engine operating condition. When the engine is identified as operating at high altitude and with low intake pressure, a coordinated control temperature-boosting strategy is triggered to control the electric supercharger and exhaust throttle valve to increase the catalytic converter inlet temperature. This effectively solves the problem of low exhaust temperature and excessive emissions due to lean air intake and incomplete combustion in high-altitude areas. xThe emissions of NH3 and HC all meet the China VII heavy-duty engine standard. At the same time, the addition of an auxiliary turbocharger ensures that the engine power does not decrease under high-altitude conditions. The synergy between full-section insulation and exhaust throttling further improves the heating efficiency and stability, making it suitable for the long-distance operation needs of heavy-duty natural gas engines. Attached Figure Description

[0016] Figure 1 This is a flowchart of the natural gas extreme operating condition catalyst inlet temperature boosting control method of the present invention; Figure 2 A flowchart of the coordinated control temperature-boosting strategy of the natural gas extreme operating condition catalyst inlet temperature boosting control method of the present invention; Figure 3 This is a schematic diagram of the intake coordination technology in the coordinated control temperature-raising strategy of the present invention; Figure 4 This is a schematic diagram of the in-machine deep heating technology in the collaborative control heating strategy of the present invention; Figure 5 This is a schematic diagram of the exhaust throttling and heat preservation synergistic technology in the synergistic control and temperature raising strategy of the present invention; Figure 6 This is a structural diagram of the natural gas extreme operating condition catalyst inlet temperature boosting control system of the present invention.

[0017] The components are: 1-Intake pipe, 2-Air filter, 3-Intercooler, 4-Electric turbocharger, 5-ECU, 6-Catalyst, 7-Exhaust pipe, 8-Exhaust throttle valve, 9-Turbocharger. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0019] See Figures 1-6 The present invention discloses a method for controlling the catalytic converter inlet temperature under extreme natural gas operating conditions. The method involves installing an electric supercharger 4 between the air filter 2 and the supercharger 9, and an exhaust throttle valve 8 between the catalytic converter 6 and the supercharger 9. The method collects the engine's intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude. Based on the intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude, the engine operating condition is determined. When the engine operating condition is determined to be a high-altitude and low-intake-pressure condition (i.e., an extreme condition), a coordinated control temperature-boosting strategy is triggered to increase the catalytic converter inlet temperature.

[0020] The method for determining engine operating conditions based on intake pressure, catalytic converter inlet temperature, engine speed, and real-time altitude is as follows: set an altitude threshold and an intake pressure threshold. When the intake pressure is less than the intake pressure threshold and the real-time altitude is greater than the altitude threshold, the engine operating condition is determined to be a high-altitude and low-intake-pressure condition.

[0021] like Figure 2 As shown, the collaborative control temperature-boosting strategy includes high-altitude intake pressure compensation and temperature-boosting collaborative technology, in-engine extreme condition deep temperature-boosting technology and exhaust throttling and full-section insulation collaborative technology.

[0022] like Figure 3 As shown, the high-altitude intake boosting compensation and temperature-increasing synergistic technology involves: adding an auxiliary boosting device (small electric supercharger) to work in conjunction with the main turbocharger. When the altitude is >2000m and the intake pressure is <30kPa, the auxiliary supercharger automatically starts, controlling the electric supercharger 4) to increase the intake pressure to a preset first intake pressure, which is 35-40kPa, thereby solving the problem of lean intake air at high altitudes. Simultaneously, an intake heating module is added to the outlet of the electric supercharger 4, controlling the intake heating module to heat the boosted intake air to a first intake temperature, which in this embodiment is 40℃-60℃, thereby increasing the in-cylinder combustion temperature and thus increasing the exhaust temperature. The boosting logic of the main turbocharger is simultaneously optimized to increase the boost pressure under low-load conditions, assisting in exhaust temperature increase.

[0023] like Figure 4 As shown, the in-cylinder extreme condition deep temperature enhancement technology employs a "ignition retarding + EGR complete shutdown + mixture optimization" strategy for high-altitude and low-intake-pressure conditions. This involves setting a first ignition advance angle retarding value, and then retarding the current ignition advance angle based on this value. In this embodiment, the first ignition advance angle retarding value is 10-18°CA, maximizing the shift of the combustion center of gravity and retaining more combustion heat. The EGR valve is completely closed to prevent exhaust gas from diluting the mixture, ensuring complete combustion in the cylinder and increasing exhaust temperature. Layered injection technology is used to optimize the mixture concentration distribution, setting a first air-fuel ratio and a second air-fuel ratio. In this embodiment, the first air-fuel ratio is λ=1.0-1.1, and the second air-fuel ratio is λ=1.2-1.3 (to control emissions). Injection is performed on the core area of ​​the cylinder based on the first air-fuel ratio to ensure intense combustion, while injection is performed on the edge area of ​​the cylinder based on the second air-fuel ratio to achieve a balance between temperature enhancement and emissions.

[0024] like Figure 5As shown, the exhaust throttling and full-section heat preservation synergistic technology is as follows: An exhaust throttling valve 8 is added in front of the catalyst inlet. Under extreme conditions, the ECU automatically controls the opening of the throttling valve and sets the opening of the exhaust throttling valve 8 to a preset first opening. In this embodiment, the first opening is to reduce the flow area by 30-40% of the initial opening, increase the exhaust back pressure, increase the in-cylinder combustion temperature and exhaust temperature, and assist in increasing the catalyst inlet temperature by 20-50°C.

[0025] The exhaust system adopts a full-section double-layer insulation structure. The exhaust pipe, turbine outlet, and catalytic converter are all wrapped with a high-temperature resistant ceramic fiber insulation layer (thickness 8-10mm). A metal protective shell is added to the outer layer of the insulation layer to reduce exhaust heat loss and ensure that the exhaust temperature decay is ≤15℃ / m, so as to maximize the transfer of heat from the engine and the throttling boost to the catalytic converter inlet.

[0026] The system acquires the operating status of the electric turbocharger 4 and the exhaust throttle valve 8 when executing the coordinated control temperature-boosting strategy. If the operating status of the electric turbocharger 4 or the exhaust throttle valve 8 is in a fault state, the backup temperature-boosting strategy is triggered.

[0027] The backup warm-up strategy is to calibrate the second ignition advance angle retarding value according to the engine operating conditions, and to retard the current ignition advance angle by increasing the first ignition advance angle retarding value to the second ignition advance angle retarding value. A third air-fuel ratio and a fourth air-fuel ratio are set, and the first air-fuel ratio is increased to the third air-fuel ratio and the second air-fuel ratio is increased to the fourth air-fuel ratio.

[0028] Extreme operating condition adaptive calibration and fault-tolerant control technology: Construct a dedicated calibration MAP for high altitude and low intake pressure, integrating multiple parameters such as altitude, intake pressure, catalytic converter inlet temperature, and engine speed to achieve adaptive coordination of various technologies; Add a fault-tolerant control module, when a certain temperature-boosting component (such as auxiliary turbocharger or exhaust throttle valve) fails, automatically activate the backup temperature-boosting strategy (such as further delaying ignition and increasing the air-fuel ratio enrichment) to ensure that the catalytic converter inlet temperature can still be stable at ≥280℃, avoiding excessive emissions.

[0029] Simultaneously, the catalyst inlet temperature is monitored in real time. When the temperature is ≥320℃, various temperature-boosting parameters are automatically adjusted to balance them. The target catalyst inlet temperature after implementing the coordinated control temperature-boosting strategy is obtained, and a closed-loop control strategy is triggered based on the target catalyst inlet temperature to adjust the coordinated control temperature-boosting strategy.

[0030] The closed-loop control strategy involves acquiring the ignition temperature of the catalyst, calibrating a first and second temperature threshold based on this temperature, and then strengthening the coordinated control temperature-boosting strategy when the catalyst inlet temperature is lower than the first temperature threshold. This enhanced temperature boosting involves setting a third ignition advance angle retardation value, and then retarding the current ignition advance angle based on this value. The third ignition advance angle retardation value must be greater than the first ignition advance angle retardation value. A fifth and sixth air-fuel ratio are also set, increasing the first air-fuel ratio to the fifth and the second air-fuel ratio to the sixth.

[0031] When the catalyst inlet temperature is greater than or equal to the first temperature threshold and less than the second temperature threshold, the coordinated control temperature increase strategy is maintained.

[0032] When the catalytic converter inlet temperature is greater than or equal to the second temperature threshold, load reduction durability protection is applied. Load reduction durability protection: A fourth ignition advance angle retardation value is set, and the current ignition advance angle is retarded based on this value. The fourth ignition advance angle retardation value is less than the first ignition advance angle retardation value. A seventh and eighth air-fuel ratio are set, reducing the first air-fuel ratio to the seventh air-fuel ratio, and then reducing the first air-fuel ratio to the eighth air-fuel ratio.

[0033] The ultimate control objective is to ensure that the catalyst temperature is greater than or equal to the catalyst ignition temperature threshold; to avoid exceeding emission standards; and to take into account engine durability. The catalyst ignition temperature threshold is equal to the first temperature threshold.

[0034] For cost control reasons, the target catalytic converter inlet temperature can be estimated using a model. This model estimates the catalytic converter inlet temperature based on factors such as engine operating conditions, exhaust flow, turbocharger operating conditions, pipeline temperature drop, and throttle valve opening. It primarily considers five key influencing factors: combustion heat release, EGR mixing, turbocharger power, throttle heating, and pipeline heat loss. The following parameters are obtained: exhaust specific heat capacity, pipe length from throttle valve outlet to catalytic converter inlet, pipe heat dissipation coefficient, ambient temperature of the engine, exhaust pressure at throttle valve outlet, exhaust pressure at turbine outlet, heat release from natural gas combustion per unit time, isobaric specific heat capacity of EGR exhaust gas, temperature of EGR exhaust gas during introduction, isobaric specific heat capacity of fresh air, EGR exhaust gas mass flow rate, fresh intake air temperature, isobaric specific heat capacity of turbine outlet exhaust gas, total exhaust mass flow rate, turbine output power, isobaric specific heat capacity of fresh air, and fresh air mass flow rate.

[0035] The exhaust throttle valve opening is calculated based on the exhaust pressure at the exhaust outlet and the turbine outlet. The expression for calculating the exhaust throttle valve opening is as follows: ; in, P throttle,outThis is the exhaust pressure at the outlet of the exhaust throttle valve, expressed in kPa. It is less than the turbine outlet pressure, and the smaller the opening, the greater the difference. P turb,out This refers to the turbine outlet exhaust pressure, expressed in kPa. ， Steady-state operating conditions for China VI natural gas engines: 105~130 kPa θ The opening of the exhaust throttle valve is θ=0°, which means fully closed and θ=90°, which means fully open. The commonly used opening for China VI emission standard is 15~45°.

[0036] The turbocharger outlet temperature is calculated based on the heat released by natural gas combustion per unit time, the isobaric specific heat capacity of EGR exhaust gas, the temperature of EGR exhaust gas at introduction, the isobaric specific heat capacity of fresh air, the mass flow rate of EGR exhaust gas, the fresh intake air temperature, the isobaric specific heat capacity of turbine outlet exhaust gas, the total exhaust mass flow rate, the turbine output power, the isobaric specific heat capacity of fresh air, and the fresh air mass flow rate. The expression for calculating the turbocharger outlet temperature is as follows: ; Among them, T turb,out The turbocharger outlet temperature is the exhaust temperature at the exhaust throttle valve outlet (turbine outlet → throttle valve outlet), and the unit is K or ℃. The core intermediate parameter = turbine outlet temperature + throttle temperature rise. Q comb It represents the heat released by natural gas combustion per unit time, expressed in kJ / s (or kW). When burning at equivalent rates, it is calculated based on the stoichiometric air-fuel ratio. C p，egr The isobaric specific heat capacity of the EGR exhaust gas is expressed in kJ / (kg·K), which can be approximated as 1.05~1.10 kJ / (kg·K) depending on the EGR temperature. T egr The temperature at which the EGR exhaust gas is introduced is expressed in K (or °C), approximately taken as the exhaust manifold outlet temperature, about 800~950K. C p,air This is the specific heat capacity of fresh air at constant pressure, expressed in kJ / (kg·K). At room temperature, it is approximately taken as 1.005 kJ / (kg·K), and can be slightly adjusted according to the intake air temperature. m egr The EGR exhaust gas mass flow rate is expressed in kg / s and is calculated from the EGR rate and the total intake flow rate. T air The fresh intake air temperature is expressed in K (or °C), and is taken as the compressor outlet intake air temperature (including the boost temperature). C p，exh The isobaric specific heat capacity of the exhaust gas at the turbine outlet is expressed in kJ / (kg·K), and is approximately taken as 1.08~1.12 kJ / (kg·K) depending on the exhaust temperature. m exhThe total exhaust mass flow rate is expressed in kg / s. W turb The turbine output power is measured in kJ / s (or kW). Ignoring mechanical losses, it is approximately equal to the compressor power consumption. C p，air The specific heat capacity at constant pressure of fresh air. m air The mass flow rate of fresh air is expressed in kg / s and is estimated by actual measurement from an air flow meter or by intake pressure and temperature.

[0037] Finally, based on the exhaust throttle valve opening, turbocharger outlet temperature, pipe heat dissipation coefficient, pipe length from throttle valve outlet to catalytic converter inlet, ambient engine temperature, and exhaust specific heat capacity, the target catalytic converter inlet temperature is calculated. The expression for calculating the target catalytic converter inlet temperature is as follows: ; Among them, T cat,in This refers to the catalytic converter inlet temperature, expressed in K (or °C, units must be consistent). China VI emission standards require the catalytic converter inlet temperature to be between 250 and 600 °C (steady-state operating conditions). T turb,out θ represents the turbocharger outlet temperature, expressed in K (or °C), a core intermediate parameter determined by combustion and turbine power output; θ represents the exhaust throttle valve opening. K The heat dissipation coefficient of the pipeline is expressed in W / (m²·K), which is related to the pipeline material and the thickness of the insulation layer. For China VI engine exhaust pipelines, it is usually 15~30 W / (m·K); L is the pipeline length from the throttle valve outlet to the catalytic converter inlet, expressed in m. For conventional heavy-duty engines, it is 0.5~1.2 m (the pipeline length is shortened after the addition of the throttle valve). T amb The ambient temperature of the engine is in K (or °C). The standard operating condition is taken as 298K (25 °C), and the extreme operating condition is substituted with the actual value. k For exhaust specific heat capacity (constant pressure specific heat capacity / constant volume specific heat capacity), the exhaust of China VI natural gas engine is approximately taken as 1.35 (adapted to equivalent combustion + EGR).

[0038] like Figure 6 As shown, a natural gas catalytic converter inlet temperature boosting control device under extreme operating conditions is disclosed. This control device includes... An electric supercharger 4 is installed between the air filter 2 and the supercharger 9 to increase the intake pressure. An intake heating module is installed at the outlet of the electric supercharger 4.

[0039] The exhaust throttle valve 8 is installed between the catalytic converter 6 and the turbocharger 9 to control the exhaust back pressure.

[0040] The multi-parameter signal acquisition module is used to acquire the engine's intake pressure, catalyst inlet temperature, speed, and real-time altitude, and output the corresponding intake pressure signal, catalyst inlet temperature signal, speed signal, and altitude signal.

[0041] ECU5 is used to receive intake pressure signal, catalyst inlet temperature signal, speed signal and altitude signal, and apply the above-mentioned natural gas extreme condition catalyst inlet temperature boosting control method to control electric supercharger 4 and exhaust throttle valve 8 to boost catalyst inlet temperature based on engine intake pressure, catalyst inlet temperature, speed and real-time altitude.

[0042] ECU5 is electrically connected to the controller of exhaust throttle valve 8, and ECU5 is electrically connected to electric supercharger 4.

[0043] The exhaust system adopts a full-section double-layer insulation structure. The exhaust pipe 7, turbine outlet, and catalytic converter 6 are fully wrapped with a high-temperature resistant ceramic fiber insulation layer (thickness 8-10mm). A metal protective shell is added to the outer layer of the insulation layer to reduce exhaust heat loss and ensure that the exhaust temperature decay is ≤15℃ / m, so as to maximize the transfer of heat from the engine and the throttling boost to the inlet of the catalytic converter 6.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions, characterized in that, The control method is as follows: an electric supercharger (4) is installed between the air filter (2) and the supercharger (9), and an exhaust throttle valve (8) is installed between the catalyst (6) and the supercharger (9); the intake pressure, catalyst inlet temperature, speed and real-time altitude of the engine are collected, and the engine operating condition is determined based on the intake pressure, catalyst inlet temperature, speed and real-time altitude. When the engine operating condition is determined to be a high altitude and low intake pressure condition, a coordinated control temperature-boosting strategy is triggered to increase the catalyst inlet temperature. The operating status of the electric booster (4) and the operating status of the exhaust throttle valve (8) are obtained when the cooperative control temperature-raising strategy is executed. When the operating status of the electric booster (4) or the operating status of the exhaust throttle valve (8) is in a fault state, the backup temperature-raising strategy is triggered. The target temperature of the catalyst inlet after the implementation of the coordinated control temperature-raising strategy is obtained, and a closed-loop control strategy is triggered based on the target temperature of the catalyst inlet to adjust the coordinated control temperature-raising strategy.

2. The method for controlling the inlet temperature of a natural gas catalyst under extreme operating conditions according to claim 1, characterized in that, The coordinated control temperature-raising strategy is as follows: Control the electric booster (4) to increase the intake pressure to a preset first intake pressure; An intake heating module is provided at the outlet of the electric booster (4), and the intake heating module is controlled to raise the intake temperature to a preset first intake temperature. Set a first ignition advance angle retarding value, and retard the current ignition advance angle according to the first ignition advance angle retarding value; Completely close the EGR valve; set a first air-fuel ratio and a second air-fuel ratio, inject into the core area of ​​the cylinder according to the first air-fuel ratio, and inject into the edge area of ​​the cylinder according to the second air-fuel ratio; Set the opening of the exhaust throttle valve (8) to a preset first opening.

3. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 2, characterized in that, The method for obtaining the target catalyst inlet temperature after implementing the aforementioned collaborative control temperature-boosting strategy is as follows: The following parameters are obtained: exhaust specific heat capacity, pipe length from throttle valve outlet to catalytic converter inlet, pipe heat dissipation coefficient, ambient temperature of the engine, exhaust pressure at throttle valve outlet, and turbine outlet exhaust pressure. The exhaust throttle valve opening is calculated based on these parameters. The following parameters are also obtained: natural gas combustion heat release per unit time, EGR exhaust gas specific heat capacity at constant pressure, EGR exhaust gas temperature upon introduction, fresh air specific heat capacity at constant pressure, EGR exhaust gas mass flow rate, fresh air temperature, turbine outlet exhaust specific heat capacity at constant pressure, total exhaust mass flow rate, turbine output power, and fresh air specific heat capacity and mass flow rate. The calculation of the exhaust throttle valve opening based on these parameters is then performed. The turbocharger outlet temperature is calculated using the specific heat capacity at constant pressure of EGR exhaust gas, the temperature of EGR exhaust gas at introduction, the specific heat capacity at constant pressure of fresh air, the mass flow rate of EGR exhaust gas, the fresh intake temperature, the specific heat capacity at constant pressure of turbine outlet exhaust gas, the total exhaust mass flow rate, the turbine output power, the specific heat capacity at constant pressure of fresh air, and the mass flow rate of fresh air. The target catalytic converter inlet temperature is calculated based on the exhaust throttle valve opening, the turbocharger outlet temperature, the pipe heat dissipation coefficient, the pipe length from the throttle valve outlet to the catalytic converter inlet, the ambient temperature of the engine, and the specific heat capacity of the exhaust gas.

4. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 3, characterized in that, The formula for calculating the target temperature at the catalyst inlet is: ； Among them, T cat,in T is the catalyst inlet temperature. turb,out Here, θ represents the turbocharger outlet temperature, and θ represents the exhaust throttle valve opening. K The heat dissipation coefficient of the pipeline. L This refers to the length of the pipe from the throttle valve outlet to the catalyst inlet. T amb The ambient temperature at which the engine operates. k This is the specific heat capacity of the exhaust gas.

5. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 3, characterized in that, The expression for calculating the opening degree of the exhaust throttle valve is as follows: ； in, P throttle,out The exhaust pressure at the outlet of the exhaust throttle valve. P turb,out This refers to the exhaust pressure at the turbine outlet. θ This refers to the opening degree of the exhaust throttle valve.

6. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 3, characterized in that, The formula for calculating the turbocharger outlet temperature is as follows: ； Among them, T turb,out The outlet temperature of the turbocharger. Q comb The heat released by the combustion of natural gas per unit time. C p，egr The specific heat capacity at constant pressure of EGR exhaust gas. T egr The temperature at which the EGR exhaust gas is introduced. C p,air The specific heat capacity at constant pressure of fresh air. m egr EGR exhaust gas mass flow rate, T air For fresh air intake temperature, C p，exh The specific heat capacity at constant pressure of the turbine outlet exhaust. m exh The total exhaust mass flow rate, W turb For turbine output power, C p，air The specific heat capacity at constant pressure of fresh air. m air This refers to the fresh air mass flow rate.

7. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 2, characterized in that, The backup warm-up strategy is as follows: calibrate the second ignition advance angle retarding value according to the engine operating conditions, retard the current ignition advance angle by increasing the first ignition advance angle retarding value to the second ignition advance angle retarding value, set a third air-fuel ratio and a fourth air-fuel ratio, increase the first air-fuel ratio to the third air-fuel ratio, and increase the second air-fuel ratio to the fourth air-fuel ratio.

8. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 2, characterized in that, The closed-loop control strategy is to obtain the ignition temperature of the catalyst, calibrate a first temperature threshold and a second temperature threshold based on the ignition temperature of the catalyst, and strengthen the collaborative control temperature-boosting strategy when the inlet temperature of the catalyst is less than the first temperature threshold. When the catalyst inlet temperature is greater than or equal to the first temperature threshold and less than the second temperature threshold, the coordinated control temperature increase strategy is maintained. When the catalyst inlet temperature is greater than or equal to the second temperature threshold, load reduction durability protection is performed.

9. The method for controlling the inlet temperature of a natural gas catalytic converter under extreme operating conditions according to claim 1, characterized in that, The method for determining engine operating conditions based on the aforementioned intake pressure, catalyst inlet temperature, engine speed, and real-time altitude is as follows: Set an altitude threshold and an intake pressure threshold. When the intake pressure is less than the intake pressure threshold and the real-time altitude is greater than the altitude threshold, the engine operating condition is determined to be a high-altitude and low-intake-pressure operating condition.

10. A natural gas catalytic converter inlet temperature boosting control device under extreme operating conditions, characterized in that, The control device includes, An electric supercharger (4) is installed between the air filter (2) and the supercharger (9) to increase the intake pressure; An intake heating module is installed at the outlet of the electric booster (4) to increase the intake temperature; An exhaust throttle valve (8) is installed between the catalyst (6) and the turbocharger (9) to control the exhaust back pressure; The multi-parameter signal acquisition module is used to acquire the engine's intake pressure, catalyst inlet temperature, speed, and real-time altitude, and output the corresponding intake pressure signal, catalyst inlet temperature signal, speed signal, and altitude signal. ECU (5) is used to receive the intake pressure signal, catalyst inlet temperature signal, speed signal and altitude signal and apply the natural gas extreme condition catalyst inlet temperature increase control method according to any one of claims 1-9 to control the intake heating module, electric supercharger (4) and exhaust throttle valve (8) to increase the catalyst inlet temperature based on the engine intake pressure, catalyst inlet temperature, speed and real-time altitude.

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