Method and system for actively regulating and controlling temperature of exhaust pipe under engine sliding working condition

Abstract

The invention discloses a method for actively regulating and controlling the temperature of an exhaust pipe under the sliding working condition of an engine, and relates to the engine control technology, the current working condition of the engine is recognized, and if the current working condition is the sliding working condition, an exhaust temperature increasing regulation and control mode is started; according to the exhaust temperature increasing regulation and control mode, a temperature rise demand target is calculated according to the temperature difference value between the current exhaust temperature of an exhaust pipe of the engine and the set target exhaust temperature, and a temperature rise control strategy is selected according to the temperature rise demand target and executed. The invention further discloses a system for actively regulating and controlling the temperature of the exhaust pipe under the engine sliding working condition. The exhaust temperature in the sliding process is increased, the cold and hot temperature difference of the exhaust pipe is reduced, and therefore the reliability of the exhaust pipe is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to engine control technology, more particularly, it relates to an exhaust pipe temperature active regulation method and system under engine coasting condition. BACKGROUND

[0002] When the engine is running, the working condition changes complexly; especially in downhill section, congestion road section, etc., the engine is more likely to run in the process of repeated loading and unloading, at this time, due to the dramatic change of engine working condition, the exhaust temperature of exhaust pipe changes too much, especially the exhaust temperature of gas machine is higher than that of diesel engine. And when the engine is coasting, the engine does not work, which leads to a sharp drop in engine exhaust temperature. Under this repeated working condition, the temperature of the exhaust pipe rises and falls suddenly, which is called cold and hot impact. The cold and hot impact has a great influence on the reliability of the material.

[0003] For example, the measured temperature difference ΔT of gas machine under congestion road condition changes between 650℃ and 100℃. The cold and hot impact caused by the large temperature difference seriously affects the service life of the exhaust pipe, and the thermal fatigue life of the exhaust pipe is only 23,000 cycles, which is far lower than the design requirement of 100,000 times. In view of this problem, the existing passive heat insulation scheme is adopted, such as increasing thermal insulation materials, which has the disadvantage of increasing weight. And the traditional strategy of controlling only through the throttle valve cannot meet the demand of temperature rise. SUMMARY

[0004] The technical problem to be solved by the present application is to provide an exhaust pipe temperature active regulation method and system under engine coasting condition, which improves the exhaust temperature during coasting process and reduces the cold and hot temperature difference of exhaust pipe, so as to improve the reliability of exhaust pipe.

[0005] The exhaust pipe temperature active regulation method under engine coasting condition, the current working condition of the engine is identified, if the current working condition is coasting condition, the exhaust temperature rising regulation mode is entered; The exhaust temperature rising regulation mode is to calculate the temperature rise demand target according to the temperature difference between the current exhaust temperature of the exhaust pipe of the engine and the set target exhaust temperature, select the temperature rise control strategy according to the temperature rise demand target, and execute.

[0006] Preferably, the temperature rise control strategy includes: The first temperature rise control strategy: if the temperature rise demand target is greater than or equal to the preset first low temperature difference threshold, the intake amount of the engine is increased by adjusting the EGR valve opening and the throttle opening; The second temperature rise control strategy: if the temperature rise demand target is less than the first low temperature difference threshold and greater than or equal to the preset second low temperature difference threshold, the exhaust temperature is increased by executing the heat management coordination strategy. Third temperature rise control strategy: If the temperature rise demand target is less than the second low temperature difference threshold, then the first temperature rise control strategy and the second temperature rise control strategy are executed simultaneously.

[0007] Preferably, the thermal management collaborative strategy is as follows: Real-time monitoring of the engine's coolant temperature and the EGR temperature value collected by the EGR temperature sensor; If the real-time water temperature value is less than the preset coasting water temperature threshold, the thermostat will be turned off. If the EGR temperature value is less than the preset EGR temperature threshold, the EGR cooler flow rate is reduced until the temperature rise target is met or the EGR cooler flow rate is minimized.

[0008] Preferably, the target temperature rise demand is calculated using a temperature rise demand forecasting and estimation model: , Where ΔT_req is the temperature rise target; α is the main control weight coefficient; T_normal is the normal operating temperature discharge; T_slide is the current temperature discharge; β is the rate of change correction coefficient; γ is the fatigue accumulation factor; and FLC is the fatigue life counter.

[0009] Preferably, if the temperature rise target is greater than or equal to a preset high temperature difference threshold, the engine maintains its current operating condition.

[0010] An active exhaust pipe temperature control system for engine coasting conditions includes an intake system, a cooling system, an EGR system, an exhaust system, and an ECU. The ECU uses the active exhaust pipe temperature control method for engine coasting conditions to control the intake system, cooling system, and EGR system to execute corresponding strategies to regulate the exhaust temperature of the exhaust system.

[0011] Beneficial effects The advantages of this invention are as follows: by determining whether the engine has entered a coasting condition, and under the coasting condition, by controlling the throttle opening and EGR valve opening, combined with overall engine thermal management adjustment and EGR temperature adjustment, multiple control strategies are adopted to adapt to the current exhaust temperature, thereby completing the overall exhaust temperature increase regulation, thereby achieving the purpose of increasing the engine exhaust temperature, reducing the temperature difference during engine operation, reducing thermal shock to the exhaust pipe, and improving the reliability of the exhaust pipe. Attached Figure Description

[0012] Fig. 1 This is a flowchart of the active exhaust pipe temperature control method of the present invention; Fig. 2 This is a flowchart illustrating the first and second temperature rise control strategies in the active temperature control method for exhaust pipes of the present invention. Detailed Implementation

[0013] 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. Example 1 See Figs. 1-2 This invention discloses an active exhaust pipe temperature control method under engine coasting conditions. The method identifies the engine's current operating condition. If the ECU receives a coasting condition signal (throttle opening of 0), it determines the current operating condition as coasting and enters an exhaust temperature boost control mode. In this embodiment, the exhaust temperature boost control mode calculates the temperature rise target based on the temperature difference between the current exhaust pipe temperature and a set target exhaust temperature. A temperature rise control strategy is then selected and executed based on the target temperature rise. This method, which uses the actual exhaust temperature difference to calculate the temperature rise target in real time, better adjusts the exhaust temperature according to the engine's actual operating conditions. Compared to the traditional method of calibrating the target temperature, it reduces the exhaust pipe temperature difference under different exhaust temperature conditions, reduces thermal shock to the exhaust pipe, and improves the reliability of the exhaust pipe.

[0014] In this embodiment, the temperature rise control strategy includes three temperature rise control strategies.

[0015] The first temperature rise control strategy involves adjusting the EGR valve opening and throttle opening to increase the engine's intake air volume if the target temperature rise is greater than or equal to a preset first low-temperature temperature difference threshold. This increases the engine's frictional work and frictional heat. This strategy effectively increases exhaust temperature when the target temperature rise is not significant. However, when the target temperature rise exceeds a certain threshold, a second temperature rise control strategy is required.

[0016] The second temperature rise control strategy: If the target temperature rise is less than the first low-temperature temperature difference threshold but greater than or equal to the preset second low-temperature temperature difference threshold, a thermal management coordination strategy is implemented to increase exhaust temperature. This thermal management coordination strategy requires coordination with the thermostat, EGR cooler, and other equipment for regulation and management. Specifically, it involves real-time monitoring of the engine's coolant temperature and the EGR temperature value collected by the EGR temperature sensor. If the real-time coolant temperature is less than the preset coasting coolant temperature threshold, the thermostat is closed to prevent coolant from flowing into the radiator, thereby increasing the coolant temperature. This coolant flows through the exhaust pipe, where it exchanges heat with the exhaust gas, thus increasing the exhaust gas temperature. Furthermore, the system also monitors the EGR temperature in real time. If the EGR temperature is less than the preset EGR temperature threshold, the EGR cooler flow rate is reduced until the target temperature rise is met or the EGR cooler flow rate is minimized. Reducing the EGR cooler flow rate significantly reduces heat loss from the exhaust gas in the EGR system, effectively helping to ensure exhaust temperature. It should be noted that when the second temperature rise control strategy is executed, the EGR valve opening and throttle opening can be maintained at the opening at the end of the first temperature rise control strategy, or they can be reset to the calibrated initial opening.

[0017] The third temperature rise control strategy: If the target temperature rise is less than the second low temperature difference threshold, then the first and second temperature rise control strategies are executed simultaneously. That is, by simultaneously increasing the intake air volume and regulating the internal water temperature and exhaust gas temperature, the goal of rapidly increasing the exhaust temperature is achieved.

[0018] In the exhaust temperature rise control mode, the exhaust temperature is controlled in a closed loop. For example, if the second temperature rise control strategy is currently being implemented and the exhaust temperature has increased significantly, when the temperature rise demand target is greater than or equal to the preset first low temperature difference threshold, the second temperature rise control strategy will be exited and the first temperature rise control strategy will be implemented.

[0019] In this embodiment, the target temperature rise demand is calculated using a temperature rise demand forecasting and estimation model, which is as follows: .

[0020] Wherein, ΔT_req is the temperature rise target; α is the main control weight coefficient; T_normal is the normal operating temperature, which ranges from 600 to 650℃; T_slide is the current temperature; β is the rate of change correction coefficient; γ is the fatigue accumulation factor, which ranges from 0 to 1; and FLC is the fatigue life counter.

[0021] As can be seen from the above model, it takes into account the different real-time exhaust temperatures (i.e., the current exhaust temperature T_slide) under different engine operating conditions, and calculates the temperature rise target by combining the fatigue life counter. It fully considers the factors affecting the durability of the exhaust pipe, and is more suitable for exhaust temperature management under different engine operating conditions, and has a more significant improvement on the durability performance of the exhaust pipe.

[0022] Furthermore, if the target temperature rise is greater than or equal to a preset high-temperature temperature difference threshold, the engine maintains its current operating condition. In this embodiment, the temperature difference thresholds are set in the following relationship: the high-temperature temperature difference threshold is greater than the first low-temperature temperature difference threshold, which is greater than the second low-temperature temperature difference threshold.

[0023] Based on the above methods, a temperature rise verification comparison was conducted. As can be seen from the comparison results in Table 1, in the existing scheme, under the tested urban coasting conditions, the engine exhaust temperature drops from 650℃ to 110℃, with a temperature difference of 540℃. However, with the scheme adopted, the final exhaust temperature is 290℃, and the temperature difference is reduced to 360℃. The overall thermal cycle life of the exhaust pipe is increased by about 2.5 times, and the durability of the exhaust pipe is significantly improved.

[0024]

[0025] Example 2 An active exhaust pipe temperature control system for engine coasting conditions includes an intake system, a cooling system, an EGR system, an exhaust system, and an ECU. Specific components include, but are not limited to, a throttle valve, an EGR valve, a thermostat, an electronic water pump, and a regulating valve for the cooler. The ECU uses the aforementioned active exhaust pipe temperature control method for engine coasting conditions to control the intake system, cooling system, and EGR system to execute corresponding strategies, thereby regulating the exhaust temperature to increase the exhaust pipe temperature, reduce engine temperature differences, minimize thermal shock to the exhaust pipe, and improve exhaust pipe reliability.

[0026] 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. An engine exhaust pipe temperature active regulation method in a coasting condition, characterized in that, identifying a current working condition of the engine, if the current working condition is a coasting working condition, entering a temperature rising regulation mode; the temperature rising regulation mode is to calculate a temperature rising demand target according to a temperature difference between a current exhaust temperature of the engine and a set target exhaust temperature, select a temperature rising control strategy according to the temperature rising demand target, and execute.

2. The method according to claim 1, wherein, the temperature rising control strategy includes: a first temperature rising control strategy: if the temperature rising demand target is greater than or equal to a preset first low-temperature temperature difference threshold, adjusting the EGR valve opening and the throttle opening to increase the intake air amount of the engine; a second temperature rising control strategy: if the temperature rising demand target is less than the first low-temperature temperature difference threshold and greater than or equal to a preset second low-temperature temperature difference threshold, executing a thermal management coordination strategy to increase the exhaust temperature; a third temperature rising control strategy: if the temperature rising demand target is less than the second low-temperature temperature difference threshold, simultaneously executing the first temperature rising control strategy and the second temperature rising control strategy.

3. The method of claim 2, wherein the method further comprises: the thermal management coordination strategy is: real-time monitoring of a real-time water temperature value of the engine and an EGR temperature value collected by an EGR temperature sensor; if the real-time water temperature value is less than a preset coasting water temperature threshold, closing the thermostat; if the EGR temperature value is less than a preset EGR temperature threshold, reducing the EGR cooler flow until the temperature rising demand target meets the requirements or the flow of the EGR cooler is the smallest.

4. The method of claim 3, wherein, calculating the temperature rising demand target by a temperature rising demand prediction estimation model: ， wherein, ΔT_req is the temperature rising demand target; α is a main control weight coefficient; T_normal is a normal working condition exhaust temperature; T_slide is a current exhaust temperature; β is a change rate correction coefficient; γ is a fatigue cumulative factor; FLC is a fatigue life counter.

5. The method of claim 2, wherein the method further comprises: if the temperature rising demand target is greater than or equal to a preset high-temperature temperature difference threshold, the engine maintains the current working condition.

6. An exhaust pipe temperature active regulation system in engine coast down condition, characterized in that, including an intake system, a cooling system, an EGR system, an exhaust system and an ECU, the ECU applies the exhaust pipe temperature active regulation method under the engine coasting working condition according to any one of claims 1-5 to control the intake system, the cooling system and the EGR system to execute corresponding strategies to regulate the exhaust temperature of the exhaust system.

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