A DDPF active regeneration control method based on engine body far post injection

Abstract

The application discloses a DDPF active regeneration control method based on engine body far post-injection, relates to aftertreatment, and has the steps that a first temperature test point is arranged on the inlet side of a DDPF, a second temperature test point is arranged on the outlet side of the DDPF, the DDPF regeneration is controlled according to the mapping relationship between the first temperature test point, the second temperature test point and a set DDPF regeneration temperature parameter, and the DDPF is subjected to regeneration thermal management in the mode of engine body far post-injection during the DDPF regeneration. The application uses the engine body far post-injection as an HC supply source, significantly reduces the hardware cost and system complexity, and simultaneously realizes accurate regeneration temperature management through the closed-loop control of the DDPF outlet temperature T6, so that the DDPF is protected from being burned by high-temperature regeneration.

Description

Technical Field

[0001] This invention relates to aftertreatment, and more specifically, to a method for active regeneration control of DDPF based on engine body far-back injection. Background Technology

[0002] With the implementation of China VI / China VII emission regulations, DPF (diesel particulate filter) has become an essential after-treatment device. Traditional active DPF regeneration mainly employs the following technical routes: (1) In-cylinder post-injection + DOC oxidation heating Post-injection fuel is injected into the combustion chamber of the engine. Unburned HC (hybrid air) enters the DOC (distillate fuel cell) with the exhaust. The DOC oxidizes the HC, releasing heat and raising the exhaust temperature to around 600°C, thus regenerating the DPF (dissipative fuel filter). However, its disadvantages include: post-injection fuel may dilute engine oil, increasing engine wear; high fuel consumption; and poor temperature control accuracy. (2) HC injection in the exhaust tailpipe An HC injector is installed before the DOC (Distillate Calibration) to directly inject diesel fuel or a special reducing agent. The disadvantages of this method are: it requires additional hardware (injector, pump, fuel tank), the system is complex, and the cost is high.

[0003] (3) Traditional DOC + Independent DPF configuration The DOC and DPF are arranged separately, with a clearly defined DOC outlet temperature (T5) measurement point. The control strategy based on the T5 temperature closed loop is mature, adjusting the HC injection quantity through T5 temperature feedback. Its disadvantages are: large aftertreatment space occupation, complex vehicle layout, and slow thermal management response.

[0004] Addressing the shortcomings of traditional DPF technology, DDPF technology emerged. DDPF (DOC on DPF) involves directly coating a DOC catalytic coating onto the front end of a DPF support, and it has the following characteristics: (1) Compact structure: Eliminates the independent DOC, reducing system back pressure and space occupation; (2) Strong thermal coupling: The DOC oxidation zone and the DPF filtration zone are directly coupled, and the temperature transfer is fast.

[0005] Although DDPF technology has solved many of the shortcomings of traditional DPF technology, its limitations in regeneration control have gradually become apparent in practical applications, mainly manifested in the following ways: (1) Insufficient temperature control accuracy: There is no independent DOC outlet temperature measuring point, that is, there is no real T5 measuring point after HC oxidation, making it difficult to accurately control the DDPF regeneration temperature window (600±50℃). (2) High HC supply cost: The system (tailpipe injection) is complex and has high cost. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an active regeneration control method for DDPF based on the engine body's far-rear injection. The method utilizes the engine body's far-rear injection as the HC supply source, which significantly reduces hardware costs and system complexity. At the same time, through closed-loop control of the DDPF outlet temperature T6, precise regeneration temperature management is achieved, protecting the DDPF carrier from being burned by high-temperature regeneration.

[0007] The present invention discloses an active regeneration control method for DDPF based on engine body far-back injection, the method being as follows: A first temperature test point is set on the inlet side of the DDPF, and a second temperature test point is set on the outlet side of the DDPF. The DDPF regeneration is controlled based on the mapping relationship between the first temperature test point, the second temperature test point and the set DDPF regeneration temperature parameter; During the regeneration of the DDPF, the regeneration heat management of the DDPF is performed by the engine body through a remote rear injection method.

[0008] Preferably, controlling DDPF regeneration according to the mapping relationship specifically involves: Determine whether the temperature value at the first temperature test point is greater than or equal to the set ignition temperature value; If the temperature value at the first temperature test point is lower than the set ignition temperature value, then the temperature value at the first temperature test point is increased. If the temperature value at the first temperature test point is greater than or equal to the set ignition temperature value, then the DDPF is subjected to trial heating, and after the trial heating is successful, the DDPF regeneration stage begins.

[0009] Preferably, the exploratory heating specifically refers to: A set trial small amount of oil is used to perform remote back spraying. After performing remote back spraying, the real-time temperatures of the first temperature test point and the second temperature test point are collected. If the temperature difference between the real-time temperatures of the first temperature test point and the second temperature test point is greater than the set temperature difference threshold, it is determined that the trial heating is successful.

[0010] Preferably, if three trial heating attempts still fail, a fault message is generated.

[0011] Preferably, the trial small amount of oil is 1-10 mg / cycle.

[0012] Preferably, during the DDPF regeneration phase, the temperature value at the first temperature test point must be greater than or equal to the set ignition temperature value.

[0013] Preferably, the set ignition temperature is 260°C.

[0014] Preferably, in the regenerative heat management, the amount of fuel injected far and far behind the engine body is calculated using the following formula: , In the formula, Q post (t) represents the fuel injection quantity at the far-end; e(t) represents the temperature deviation between the target temperature of the second temperature test point and the real-time temperature value of the second temperature test point; K p ,K i ,K d These are the proportional coefficient, integral coefficient, and differential coefficient, respectively; Q ff (t) represents the feedforward compensation amount.

[0015] Preferably, DDPF regeneration is terminated when the real-time carbon load in the DDPF is detected to be less than the set target carbon load threshold or a fault is triggered.

[0016] Preferably, when exiting DDPF regeneration, the amount of fuel injected into the engine body at the far-rear injection point is reduced to 0 at a set ramp rate.

[0017] Beneficial effects The advantages of this invention are: 1. This invention utilizes the engine's own far-rear injection as the HC supply source, significantly reducing hardware costs and system complexity; at the same time, through closed-loop control of the DDPF outlet temperature T6, it achieves precise regeneration temperature management, protecting the DDPF carrier from being burned by high-temperature regeneration.

[0018] 2. Before DDPF enters regeneration, a trial-and-error method of remote spraying is used, combined with monitoring of the temperature difference between the front and rear sides of DDPF, which improves the success rate of DDPF entering regeneration and reduces the risk of emissions exceeding standards due to DDPF failing to enter the regeneration stage normally.

[0019] 3. During the DDPF regeneration exit phase, the fuel injection quantity is reduced at a ramp rate to achieve safe cooling and exit of DDPF regeneration. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the configuration of the National VII dual-injection system (dual-stage SCR aftertreatment) of the present invention.

[0021] Figure 2 This is a schematic diagram comparing the WHTC cycle regeneration temperatures based on the T6 temperature closed loop of the present invention and the T5 temperature closed loop of the traditional technology.

[0022] Figure 3 This is a schematic diagram comparing the regeneration efficiency of WHTC cycles based on the T6 temperature closed loop of the present invention and the T5 temperature closed loop of the traditional technology. Detailed Implementation

[0023] 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. See Figure 1 The present invention provides an active regeneration control method for DDPF based on the engine body remote and rear injection, which is mainly for the configuration of China VII dual injection system (SCR1+ASC1+DDPF+SCR2+ASC2). It uses the engine body remote and rear injection as the HC supply source, and achieves precise regeneration temperature management through closed-loop control of DDPF outlet temperature T6. At the same time, it realizes temperature monitoring and protects DDPF from being burned by high temperature regeneration.

[0024] The China VII dual-injection system refers to the configuration of two independent urea injection systems, located before SCR1 and after DDPF (before SCR2), respectively. In the China VII dual-injection system configuration, SCR1 / ASC1 is a pre-stage SCR and ammonia escape catalyst, handling NOx during cold starts and at low loads; DDPF is an integrated DOC-DPF, combining oxidation and capture functions; SCR2 / ASC2 is a post-stage SCR and ammonia escape catalyst, handling NOx and NH3 under high-temperature conditions. Remote after-injection refers to fuel injection after the engine's power stroke and at the beginning of the exhaust stroke, with the fuel entering the aftertreatment system along with the exhaust gas.

[0025] The following is the specific technical solution of the DDPF active regeneration control method based on the engine body remote rear injection of the present invention.

[0026] Temperature test points T5 and T6 are set on both sides of the DDPF, where T5 is the DDPF inlet temperature (first temperature test point) and T6 is the DDPF outlet temperature (second temperature test point). A mapping relationship is established between T5, T6, and the set DDPF regeneration temperature. The temperature test points and target values ​​are set as shown in Table 1 below.

[0027]

[0028] Specifically, under the basic operating condition of DDPF regeneration, T 6，target = 600±20℃; Under high carbon loading (>5g / L) conditions of DDPF, T 6，target = 550℃ (target regeneration temperature).

[0029] During DDPF regeneration, the engine's remote rear injection system replaces the external injection system for DDPF regeneration thermal management. This approach reduces the need for an HC injection unit and its control unit, significantly lowering hardware costs and system complexity, while ensuring regeneration reliability under China VII emission regulations.

[0030] The control logic for DDPF regeneration mainly includes the following four stages: Phase 1: Preparation Phase. The temperature T5 is used to determine whether this phase is in progress. When T5 < 260℃, it indicates the preparation phase, and the far-to-rear injection quantity is 0. T5 can be increased at this stage by methods such as intake throttling, near-to-rear injection, retarding the ignition timing, and reducing rail pressure.

[0031] Phase 2: Heating phase, i.e., T5 ≥ 260℃.

[0032] At this point, a small, trial-and-error fuel injection rate is used. This trial-and-error rate can be set to 1-10 mg / cycle. After the injection is performed, the temperature difference ΔT between T6 and T5 is monitored. If ΔT > 30℃, it indicates that the DOC coating has successfully ignited, and the DDPF heating is considered successful. If three attempts fail, a fault is reported, prompting maintenance.

[0033] Phase 3: Regeneration Phase. During this phase, T5 needs to be maintained above 260°C.

[0034] During DDPF regeneration, the fuel injection quantity is controlled using closed-loop PID control, specifically as follows: .

[0035] Among them, Q post (t): Rear fuel injection quantity (mg / cycle); e(t) = T 6，target T6(t): Temperature deviation (°C); K p ,K i ,K d The specific values ​​for the proportional coefficient, integral coefficient, and differential coefficient can be found in Table 2; Q ff (t): Feedforward compensation amount.

[0036]

[0037] In this embodiment, the formula for calculating the feedforward compensation amount is: .

[0038] in: Exhaust mass flow rate (kg / h); c p Specific heat capacity of exhaust gas (≈1.05 kJ / kg·K); LHV fuel Low calorific value of fuel oil (≈42.5 MJ / kg); η DOC DDPF oxidation efficiency (calibrated value, 0.9-0.95); n cyl Number of cylinders; f engEngine speed (rps); T4 is the front exhaust temperature of SCR1 / ASC1.

[0039] Depend on Figure 2 It is evident that the T6 temperature closed-loop system of this invention achieves a regeneration temperature significantly closer to the target regeneration temperature during regeneration compared to the T5 temperature closed-loop system used in traditional WHTC cycles. Furthermore, as... Figure 3 As shown, the regeneration efficiency of WHTC cycle based on T6 temperature closed loop is significantly higher than that of WHTC cycle based on T5 temperature closed loop in traditional technology, and is also higher than the target regeneration efficiency of 80% of the engineering target.

[0040] Phase 4: Exit Phase.

[0041] When the carbon load is <0.5g / L, or when a fault is triggered, DDPF regeneration is discontinued. Fault triggering includes T6 upper limit protection and temperature rise rate protection. When T6 ≥ 650℃, T6 upper limit protection is triggered, displaying a Level 2 fault and cutting off remote and rear injection. When dT6 / dt > 50℃ / s, temperature rise rate protection is triggered, cutting off remote and rear injection while reducing power. If, after cutting off remote and rear injection, T6 still rises to 700℃, T6 danger protection is triggered, displaying a Level 3 fault and limiting engine torque.

[0042] During this stage, the fuel injection quantity at the far end decreases to 0 at a certain ramp rate, which is ≤10% / s. After the fuel injection quantity at the far end decreases to 0, cooling monitoring is performed at T6. When T6 < 350℃, it is confirmed that the temperature has dropped to a safe range, and regeneration is discontinued.

[0043] 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 active regeneration control of DDPF based on engine body far-rear injection, characterized in that, The method is as follows: A first temperature test point is set on the inlet side of the DDPF, and a second temperature test point is set on the outlet side of the DDPF. The DDPF regeneration is controlled based on the mapping relationship between the first temperature test point, the second temperature test point and the set DDPF regeneration temperature parameter; During the regeneration of the DDPF, the regeneration heat management of the DDPF is performed by the engine body through a remote rear injection method.

2. The DDPF active regeneration control method based on engine body far-rear injection according to claim 1, characterized in that, The control of DDPF regeneration based on the aforementioned mapping relationship is specifically as follows: Determine whether the temperature value at the first temperature test point is greater than or equal to the set ignition temperature value; If the temperature value at the first temperature test point is lower than the set ignition temperature value, then the temperature value at the first temperature test point is increased. If the temperature value at the first temperature test point is greater than or equal to the set ignition temperature value, then the DDPF is subjected to trial heating, and after the trial heating is successful, the DDPF regeneration stage begins.

3. The DDPF active regeneration control method based on engine body far-rear injection according to claim 2, characterized in that, The tentative heating specifically refers to: A set trial small amount of oil is used to perform remote back spraying. After performing remote back spraying, the real-time temperatures of the first temperature test point and the second temperature test point are collected. If the temperature difference between the real-time temperatures of the first temperature test point and the second temperature test point is greater than the set temperature difference threshold, it is determined that the trial heating is successful.

4. The DDPF active regeneration control method based on engine body far-rear injection according to claim 3, characterized in that, If three attempts to heat the device fail, a fault message will be generated.

5. The DDPF active regeneration control method based on engine body far-rear injection according to claim 3, characterized in that, The initial small oil volume is 1-10 mg / cycle.

6. The DDPF active regeneration control method based on engine body far-rear injection according to claim 2, characterized in that, During the DDPF regeneration phase, the temperature value at the first temperature test point must be greater than or equal to the set ignition temperature value.

7. The active regeneration control method for DDPF based on engine body far-rear injection according to claim 2, characterized in that, The set ignition temperature is 260°C.

8. A method for active regeneration control of DDPF based on engine body far-rear injection according to any one of claims 1-7, characterized in that, In the regenerative heat management, the amount of fuel injected far and behind the engine body is calculated using the following formula: ， In the formula, Q post (t) is the far post-injection amount; e(t) is the temperature deviation between the set second temperature test point target temperature and the real-time temperature value of the second temperature test point; K p ,K i ,K d are proportional coefficient, integral coefficient, and differential coefficient, respectively; Q ff (t) is the feedforward compensation amount.

9. A method for active regeneration control of DDPF based on engine body far-rear injection according to any one of claims 1-7, characterized in that, When the real-time carbon load in the DDPF is detected to be less than the set target carbon load threshold or a fault is triggered, DDPF regeneration is terminated.

10. The DDPF active regeneration control method based on engine body far-rear injection according to claim 9, characterized in that, When DDPF regeneration is discontinued, the amount of fuel injected into the engine body at the far-rear injection point is reduced to 0 at a set ramp rate.

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