DPF model feedforward and feedback temperature control method

Abstract

The invention discloses a DPF model feedforward and feedback temperature control method. The method comprises the following steps that the theoretical demand temperature of each block outlet of a DOC temperature model is calculated according to the target temperature of the DOC temperature model outlet; according to the environment temperature, the inlet actual measurement temperature value of the DOC temperature model and the theoretical demand temperature of the outlet of each block, the fuel amount needed by each block is obtained through calculation; calculating the temperature value of the outlet of each block according to the fuel quantity required by each block and the inlet temperature of the DOC temperature model at the previous moment; calculating a DOC inlet compensation temperature value according to the temperature value of the last block outlet of the DOC temperature model, the actually measured temperature value of the DPF inlet and the temperature loss of a pipeline between the DOC outlet and the DPF inlet; and according to the DOC inlet compensation temperature value and the actually measured temperature value of the DOC temperature model inlet, calculating to obtain the adaptive inlet temperature value of the DOC. By adopting the method, the calibration period can be shortened, the problem of DOC aging does not need to be considered, and self-adaptive adjustment is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of DPF model temperature control, and particularly relates to a feedforward and feedback temperature control method for a DPF model. Background Art

[0002] Diesel engines have the disadvantage of relatively high particulate matter (PM) emissions. With the increasingly stringent current emission regulations, the current mainstream measure to control PM emissions is to adopt a post-treatment system composed of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF). When too much PM is collected, a regeneration measure is taken for the DPF to burn off the particulate matter inside. Therefore, how to effectively and accurately control the temperature during this process is the key technology.

[0003] There are currently two mainstream temperature control strategies: 1. A feedforward plus feedback temperature control strategy through a working condition look-up table method; 2. A feedforward plus feedback temperature control strategy based on model calculation.

[0004] Most of the existing ones adopt the former control strategy. However, this control method has a large calibration difficulty and can only meet the temperature control accuracy requirements under steady state. The temperature control effect and anti-interference ability under dynamic switching are average. And the second method also has various problems, such as DOC aging, decreased catalytic performance leading to reduced accuracy of model calculation, deviation of temperature control characteristics; the mechanism model is too complex and has poor generality; the PID control of the closed-loop feedback has a slow response, etc. Summary of the Invention

[0005] In order to solve the problems of large calibration difficulty of the existing method and low calculation accuracy caused by DOC aging, the present invention provides a feedforward and feedback temperature control method for a DPF model.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention discloses a feedforward temperature control method for a DPF model, including the following steps:

[0008] Calculate the theoretical required temperature at the outlet of each block of the DOC temperature model according to the target temperature at the outlet of the DOC temperature model. The DOC temperature model is divided into N blocks along the direction from its inlet to the outlet, and N is a natural number greater than or equal to 2;

[0009] Calculate the fuel quantity required for each block according to the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each block.

[0010] The temperature value at the outlet of each block is calculated based on the fuel quantity required for each block and the inlet temperature of the DOC temperature model at the previous moment;

[0011] The DOC inlet compensation temperature value is calculated based on the temperature value at the outlet of the last block of the DOC temperature model, the measured temperature value at the DPF inlet, and the temperature loss in the pipeline between the DOC outlet and the DPF inlet;

[0012] The adaptive inlet temperature value of the DOC is calculated based on the DOC inlet compensation temperature value and the measured temperature value at the inlet of the DOC temperature model.

[0013] A second aspect of the present invention discloses a DPF model feedforward and feedback temperature control method, including a DPF model feedforward temperature control method described in the first aspect;

[0014] The fuel quantity required for each block is calculated based on the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each block. After that, it further includes:

[0015] The required temperature of each block is calculated based on the fuel quantity required for each block and the theoretical required temperature at the outlet of the previous block;

[0016] The corrected fuel quantity value corresponding to each block is calculated based on the required temperature of each block and the temperature value at the outlet of each block;

[0017] The corrected fuel quantity values corresponding to each block are accumulated to obtain the DPF corrected fuel quantity value;

[0018] The required fuel quantity is determined based on the adaptive inlet temperature value of the DOC;

[0019] The fuel injection quantity of the DOC temperature model is controlled based on the DPF corrected fuel quantity value and the required fuel quantity.

[0020] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0021] 1. By dividing the DOC temperature model into blocks, the temperature downstream of each block is calculated when the input heat and the upstream temperature are known, and the outlet temperature of the DOC temperature model is obtained. The calibration difficulty of the whole method is reduced, and the calibration period is shortened.

[0022] 2. The whole method does not need to consider the problem of DOC aging, can be adaptively adjusted, and greatly extends the service life of the after-treatment system and the software update frequency. Brief Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 Structural schematic diagram of the DOC temperature model of the present invention

[0025] Figure 2 Schematic diagram of the temperature distribution of the DOC temperature model. Specific embodiments

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the accompanying drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0028] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship when the product of the present invention is normally placed, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0032] In this solution, the DOC temperature model is first divided into N segments along the direction from its inlet to the outlet, where N is a natural number greater than or equal to 2. For a specific cutting example, refer to Figure 1 as shown, where Figure 1 an example of being cut into 6 segments is shown.

[0033] After the division, assuming that the physical properties of each segment are the same, the heat balance equation is applied to each segment respectively. When the input heat and the upstream temperature are known, the temperature downstream of each segment can be calculated, and so on until the temperature at the outlet of the DOC temperature model is calculated.

[0034] Considering the heat dissipation of the DOC carrier, the fuel conversion efficiency, etc., the required fuel injection quantity is calculated. The aging degree of the DOC is calculated through temperature, HC mass flow rate, etc., and the DOC inlet temperature is compensated by integration. That is, the exhaust heat Q in,mass + the diesel combustion heat Q in，fuel = the exhaust heat Q Out,mass + the fuel leakage heat Q Out,slip + the heat loss Q Heatloos .

[0035] If the DOC temperature model is used for a long time, there will be a risk of aging and a decrease in catalytic performance. At this time, the fuel quantity calculated based on the model cannot make the DOC outlet temperature and the DPF inlet temperature reach the target temperature, resulting in problems such as incomplete combustion of particulate matter. Since the internal temperature model of the DOC calculates the fuel quantity based on the inlet temperature measured by the sensor, the first aspect of the present invention discloses a DPF model feedforward temperature control method, including steps S01 to S05.

[0036] When the following situations exist, the method of this solution is used to compensate and correct the inlet temperature of the DOC temperature model:

[0037] 1. The vehicle is in the active regeneration working condition;

[0038] 2. The inlet temperature of the DPF is greater than the threshold;

[0039] 3. The inlet temperature of the DOC is within the threshold range;

[0040] 4. The rate of change of the exhaust mass flow is within the threshold range, and the exhaust mass flow is large;

[0041] 5. There is no fault.

[0042] Step S01: Calculate the theoretical required temperature at the outlet of each section of the DOC temperature model according to the target temperature at the outlet of the DOC temperature model. The DOC temperature model is divided into N sections along the direction from its inlet to the outlet, where N is a natural number greater than or equal to 2.

[0043] In this step, the regeneration set temperature is used as the outlet target temperature T of the last section N,des , at this time, without considering the exothermic reaction and only considering the heat loss to the environment, the theoretical required temperature of each section can be calculated sequentially from the last section forward:

[0044]

[0045] where i is a natural number greater than or equal to 1 and less than or equal to N, and T i is the theoretical required temperature at the outlet of the i-th section, k is the heat dissipation coefficient, m EG is the exhaust mass flow, cp EG is the specific heat capacity of the exhaust gas, and T env is the ambient temperature.

[0046] Step S02: Calculate the fuel quantity required for each section according to the ambient temperature, the measured inlet temperature value of the DOC temperature model, and the theoretical required temperature at the outlet of each section.

[0047] Take the measured inlet temperature value of the DOC temperature model collected by the sensor as the inlet temperature T of the first section 0， When not considering the heat release capacity and fuel conversion efficiency issues, the temperature distribution curve of the DOC temperature model should be as shown by curve ① in Figure 2 ; due to the limitation of the heat release capacity of the DOC temperature model and the fuel conversion efficiency issue of each internal section, the actual temperature distribution curve should be as shown by curve ② in Figure 2 , therefore, the fuel quantity required for each section is:

[0048]

[0049] m Fu,i = 0, (T i > T i-1 ),

[0050] where m Fu,i is the fuel quantity required for the i-th section, HFu is the fuel calorific value. When i = 1, T i-1 is the measured inlet temperature value of the DOC temperature model.

[0051] The required temperature for each block is:

[0052]

[0053] where H Fu is the fuel calorific value, η i is the fuel conversion efficiency, f loss is the heat loss.

[0054] Step S03: Calculate the temperature value at the outlet of each block based on the fuel quantity required for each block and the inlet temperature of the DOC temperature model at the previous moment.

[0055] Specifically, the temperature value at the outlet of the i-th block is:

[0056] T 0,sim = T′ Adap ,

[0057] where T i,sim is the temperature value at the outlet of the i-th block, m i,Brick is the mass of each block, cp i,Brick is the specific heat capacity of each block, A i,Brick is the contact area of each block with the air, T doc,in is the measured temperature value at the inlet of the DOC temperature model, f loss is the heat loss, T' Adap is the adaptive inlet temperature value of the DOC at the previous moment.

[0058] Step S04: Calculate the DOC inlet compensation temperature value based on the temperature value at the outlet of the last block of the DOC temperature model, the measured temperature value at the inlet of the DPF, and the temperature loss in the pipeline between the DOC outlet and the DPF inlet.

[0059] Specifically, the DOC inlet compensation temperature value is obtained by integral calculation:

[0060] ΔT doc,in = K I *∫(T dpf,in -(T N,sim +T drop ))

[0061] where ΔT doc,in is the DOC inlet compensation temperature value, K I is the integral term coefficient, T N,sim is the temperature value at the outlet of the DOC temperature model, T dpf,inThe measured temperature value at the DPF inlet, T drop is the temperature loss of the pipeline between the DOC outlet and the DPF inlet. Among them, T drop can be obtained according to experiments.

[0062] Step S05: Calculate the adaptive inlet temperature value of the DOC based on the DOC inlet compensation temperature value and the measured temperature value at the inlet of the DOC temperature model.

[0063] Specifically, the adaptive inlet temperature value of the DOC is:

[0064] T Adap = T doc,in + ΔT doc,in ,

[0065] where, T doc,in is the measured temperature value at the inlet of the DOC temperature model.

[0066] Based on this, the second aspect of the present invention also discloses a DPF model feedforward and feedback temperature control method. On the basis of the DPF model feedforward temperature control method in the first aspect, when calculating the fuel quantity required for each cut according to the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each cut, the method further includes steps S11 to S15.

[0067] Step S11: Calculate the required temperature for each cut based on the fuel quantity required for each cut and the theoretical required temperature at the outlet of the previous cut.

[0068] The required temperature for each cut in this step is detailed in the above step S02.

[0069] Step S12: Calculate the corrected fuel quantity value corresponding to each cut according to the required temperature of each cut and the temperature value at the outlet of each cut.

[0070] Specifically, the fuel quantity of each cut is used as the dynamic corrected fuel quantity value Δm Fu,i as:

[0071] Δm Fu,i = K P,i *(T i,des - T i,sim ),

[0072] K P,i is the integral term coefficient for each cut.

[0073] Step S13: Accumulate the corrected fuel quantity values corresponding to each cut to obtain the DPF corrected fuel quantity value.

[0074] Specifically, the DPF corrected fuel quantity value Δm Fu is:

[0075]

[0076] Step S14. Determine the required fuel quantity based on the adaptive inlet temperature value of the DOC.

[0077] Step S15. Control the fuel injection quantity of the DOC temperature model according to the DPF corrected fuel quantity value and the required fuel quantity.

[0078] For steps S14 and S15 of this solution, refer to the existing methods, and this solution will not be elaborated.

[0079] Using the above method, it has the following advantages:

[0080] (1) Simplify the calibration difficulty, reduce the calibration cycle, increase the universality of a set of calibration data, and save development costs;

[0081] (2) Under steady-state conditions (parked regeneration), the temperature can be accurately controlled within ±3°C, and under dynamic conditions (driving regeneration), the temperature can also be controlled within ±10°C, improving the DPF regeneration efficiency and the engine fuel consumption performance, enhancing the safety and reliability during the regeneration process, and reducing the risk of DPF damage and failure;

[0082] (3) For the problem of DOC aging in the diesel vehicle market, it can be adaptively adjusted, greatly extending the service life of the after-treatment system and the software update frequency. This adaptive strategy increases the anti-interference ability during the regeneration process.

[0083] To verify the solution effect, for example:

[0084] Such as Figure 1 As shown, drill holes in the DOC carrier and install 6 thermocouples with a diameter of 0.5 mm at positions T1 to T6. The thermocouple at the first T0 position can use a temperature sensor and needs to be installed at a position about 3 to 4 mm outside the carrier. The last thermocouple needs to be installed at a position about 3 to 4 mm inside the carrier from the outlet.

[0085] First, conduct a DOC inlet temperature universal characteristic experiment, measure the hydrocarbon and carbon monoxide emissions of the original exhaust, and calculate the near-post injection fuel efficiency according to the following formula:

[0086]

[0087] Among them, η POI2 is the near-post injection combustion efficiency, HC and CO are the hydrocarbon and carbon monoxide contents respectively, with the unit of ppm, N is the engine speed, and q POI2,des is the near-post injection required fuel quantity. Draw a three-dimensional MAP diagram from the speed, fuel injection quantity, and efficiency for subsequent calculations.

[0088] According to the engine universal characteristic, 36 steady-state operating points are uniformly selected based on the engine speed and torque. Manually control the injection quantity of the far post-injection. When the DPF inlet temperature stabilizes at 610 °C at different operating points, record the temperature of the thermocouple T6 under different operating conditions, and record it as the target temperature of the last segment of the DOC. Calculate the fuel conversion efficiency η of each segment using the temperature value of each thermocouple i :

[0089]

[0090] Take the exhaust mass flow rate m EG as the abscissa and η i as the ordinate to draw several two-dimensional scatter plots, and fit them into curves to form a three-dimensional MAP diagram and fill it into the corresponding calibration MAP. Subsequently, optimize the conversion efficiency at intervals of 50 kg / h of the exhaust mass flow rate, and adjust the fuel conversion efficiency η i of each operating point so that the target temperature T i,des of each block is equal to the simulated temperature T i,sim .

[0091] Adjust the combustion efficiency of the calibrated far post-injection quantity so that the thermocouple value T i , the target temperature T i,des and the simulated temperature T i,sim are all equal, and conduct a universal characteristic experiment for temperature inspection. Take the exhaust mass flow rate as the abscissa and T 6,sim as the ordinate, and draw a three-dimensional MAP diagram with the difference between the DPF inlet temperature T dpf,act measured by the sensor and T 6,sim as the Z-axis to obtain the temperature drop T drop .

[0092] According to experience and experimental calibration of the brick mass, dynamic correction coefficient Kp, and relevant coefficients of the adaptive observer, etc. Finally, pay attention to the dynamic performance of the temperature. First, warm up the engine, switch to the regeneration mode, and conduct the WHTC (Woeldwide harmonized Light-duty Test Cycle) cycle experiment. It can be observed that the DPF inlet temperature can meet the target, with an error within ±15 °C, and the actual value of the inlet temperature is consistent with the simulated value

[0093] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention

Claims

1. A feedforward temperature control method for a DPF model, characterized in that It includes the following steps: Calculating the theoretical required temperature at the outlet of each block of the DOC temperature model according to the target temperature at the outlet of the DOC temperature model. The DOC temperature model is divided into N blocks along the direction from its inlet to the outlet, and N is a natural number greater than or equal to 2; Calculating the fuel quantity required for each block according to the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each block; Calculating the temperature value at the outlet of each block according to the fuel quantity required for each block and the inlet temperature of the DOC temperature model at the previous moment; Calculating the DOC inlet compensation temperature value according to the temperature value at the outlet of the last block of the DOC temperature model, the measured temperature value at the inlet of the DPF, and the temperature loss in the pipeline between the DOC outlet and the DPF inlet; Calculating the adaptive inlet temperature value of the DOC according to the DOC inlet compensation temperature value and the measured temperature value at the inlet of the DOC temperature model.

2. The feed-forward temperature control method for a DPF model according to claim 1, characterized in that: The calculation of the theoretical required temperature at the outlet of each block of the DOC temperature model according to the target temperature at the outlet of the DOC temperature model is as follows: where i is a natural number greater than or equal to 1 and less than or equal to N, T i is the theoretical required temperature of the i-th cut-off outlet, k is the heat dissipation coefficient, m EG is the exhaust gas mass flow rate, cp EG is the specific heat capacity of the exhaust gas, T env is the ambient temperature.

3. The feedforward temperature control method for a DPF model according to claim 2, characterized in that: The calculation of the fuel quantity required for each block according to the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each block is as follows: m Fu,i = 0, (T i > T i-1 ), where m Fu,i is the fuel quantity required for the i-th cut, H Fu is the calorific value of the fuel. When i = 1, T i-1 is the measured inlet temperature value of the DOC temperature model.

4. A DPF model feedforward temperature control method according to claim 3, characterized in that: The calculation of the temperature value at the outlet of each block according to the fuel quantity required for each block and the inlet temperature of the DOC temperature model at the previous moment is as follows: Among them, T i,sim is the temperature value at the outlet of the i-th cut, m i,Brick is the mass of each cut, cp i,Brick is the specific heat capacity of each cut, A i,Brick is the contact area of each cut with the air, T doc,in is the measured temperature value at the inlet of the DOC temperature model, f loss is the heat loss, T’ Adap is the adaptive inlet temperature value of the DOC at the previous moment.

5. A feedforward temperature control method for a DPF model according to claim 1, characterized in that: The calculation of the DOC inlet compensation temperature value according to the temperature value at the outlet of the last block of the DOC temperature model, the measured temperature value at the inlet of the DOC temperature model, and the temperature loss in the pipeline between the DOC outlet and the DPF inlet is as follows: ΔT doc,in = K I * ∫(T dpf,in -(T N,sim + T drop )) where, ΔT doc,in is the DOC inlet compensation temperature value, in K I is the integral term coefficient, T N,sim is the temperature value at the outlet of the DOC temperature model, in T dpf,in is the measured temperature value at the DPF inlet, in T drop is the temperature loss of the pipeline between the DOC outlet and the DPF inlet.

6. A DPF model feedforward and feedback temperature control method, characterized in that: It includes a DPF model feedforward temperature control method as described in any one of claims 1 to 5; After calculating the fuel quantity required for each block according to the ambient temperature, the measured temperature value at the inlet of the DOC temperature model, and the theoretical required temperature at the outlet of each block, it further includes: Calculating the required temperature of each block according to the fuel quantity required for each block and the theoretical required temperature at the outlet of the previous block; Calculating the corrected fuel quantity value corresponding to each block according to the required temperature of each block and the temperature value at the outlet of each block; Accumulating the corrected fuel quantity values corresponding to each block to obtain the DPF corrected fuel quantity value; Determining the required fuel quantity according to the adaptive inlet temperature value of the DOC; Controlling the fuel injection quantity of the DOC temperature model according to the DPF corrected fuel quantity value and the required fuel quantity.

7. A DPF model feedforward and feedback temperature control method according to claim 6, characterized in that: The calculation of the required temperature of each block according to the fuel quantity required for each block and the theoretical required temperature at the outlet of the previous block is as follows:

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