Urea nozzle system for urea overflow cooling and control method

Abstract

The invention discloses a urea overflow cooling control method, relates to the technical field of diesel engine tail gas after-treatment and solves the technical problems that an existing urea nozzle cooling mode is poor in effect, a system is complex and actual requirements are difficult to meet. The method comprises the steps that the target temperature and the target urea overflow flow in a nozzle coil are set, the actual urea pump rotating speed is obtained, the required urea overflow flow is calibrated according to the target temperature in the nozzle coil, and the target urea pump rotating speed is obtained according to the target urea overflow flow and the required urea overflow flow. And the target urea overflow amount is obtained according to the target urea pump rotating speed, and the temperature in the urea nozzle is reduced according to the target urea overflow amount. The invention further discloses a urea nozzle system for urea overflow cooling. According to the urea nozzle cooling device, efficient cooling of the urea nozzle is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diesel engine exhaust aftertreatment technology, more particularly, it relates to a urea overflow cooling urea nozzle system and a control method. BACKGROUND

[0002] In the diesel engine exhaust aftertreatment system, the urea nozzle is one of the key components, and its working state directly affects the exhaust treatment effect. However, in the high load working condition or regeneration working condition of the engine, heat will be absorbed and generated in the urea nozzle. Especially in high temperature environment, or after the engine stops working, the engine water pump stops working, and the cooling water of the nozzle stops circulating, which is easy to cause the temperature of the nozzle to be too high, thereby affecting the service life and working performance of the nozzle. In addition, in the low temperature environment in winter, the urea solution is easy to freeze, thereby affecting the normal work of the urea nozzle. In the prior art, the urea nozzle is usually cooled by cooling water, but this way has the problems of poor cooling effect, complex system, and high dependence on electric heating and cooling water, which is difficult to meet the actual demand. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a urea overflow cooling urea nozzle system and a control method to solve the technical problems of poor cooling effect, complex system and difficulty in meeting the actual demand of the existing urea nozzle cooling method.

[0004] The control method for the urea overflow cooling urea nozzle system provided by the present application is characterized in that the target temperature and the target urea overflow flow rate inside the nozzle coil are set, the actual urea pump speed is obtained, the required urea overflow flow rate is calibrated according to the target temperature inside the nozzle coil, the target urea pump speed is obtained according to the target urea overflow flow rate and the required urea overflow flow rate, the target urea overflow flow rate is obtained according to the target urea pump speed, and the temperature inside the urea nozzle is reduced according to the target urea overflow flow rate.

[0005] Further improvement, the method for obtaining the target urea pump speed according to the target urea overflow flow rate and the required urea overflow flow rate is, The target urea overflow flow rate and the required urea overflow flow rate are subtracted to obtain a urea overflow flow rate difference value, the urea overflow flow rate difference value is PID controlled to obtain a control signal amount, the control signal amount is input into the ECU, the ECU sets the target urea pump speed according to the control signal amount, and the ECU calibrates the urea overflow flow rate closed loop correction coefficient according to the control signal amount to correct the urea overflow flow rate difference value.

[0006] Further, the expression for obtaining the control signal amount by PID controlling the urea overflow flow rate difference value is, ; wherein, e(t) is a urea overflow flow rate difference, K p is a proportional gain, K i is an integral gain, K d is a differential gain, de (t) / dt is a rate of change of error, U(t) is a control signal amount.

[0007] Further, a maximum pump speed correction coefficient and a minimum pump speed correction coefficient are set, and when the urea overflow flow rate closed loop correction coefficient is greater than or equal to the maximum pump speed correction coefficient, the urea overflow flow rate closed loop correction coefficient is equal to the maximum pump speed correction coefficient, and when the urea overflow flow rate closed loop correction coefficient is less than or equal to the minimum pump speed correction coefficient, the urea overflow flow rate closed loop correction coefficient is equal to the minimum pump speed correction coefficient.

[0008] Further, a method for obtaining a target urea overflow flow rate according to the target urea pump speed is, a gear modulus of the urea pump, a gear tooth number of the urea pump, and a gear tooth width of the urea pump are obtained, a displacement of the urea pump is calculated according to the gear modulus of the urea pump, the gear tooth number of the urea pump, and the gear tooth width of the urea pump, a theoretical urea flow rate pumped out from the urea tank per unit time is calculated according to the displacement of the urea pump and the target urea pump speed, an actual urea flow rate pumped out from the urea tank per unit time is calculated according to the theoretical urea flow rate pumped out from the urea tank per unit time, and a target urea overflow flow rate is obtained by subtracting an actual nozzle injection amount per unit time from the actual urea flow rate pumped out from the urea tank per unit time.

[0009] Further, an expression for calculating the theoretical urea flow rate pumped out from the urea tank per unit time according to the displacement of the urea pump and the target urea pump speed is, ; wherein Q0 is the urea flow rate pumped out from the urea tank per unit time, V is the displacement of the urea pump, and N is the target urea overflow flow rate.

[0010] Further, an expression for calculating the actual urea flow rate pumped out from the urea tank per unit time according to the theoretical urea flow rate pumped out from the urea tank per unit time is, ; wherein Q0 is the urea flow rate pumped out from the urea tank per unit time, Q1 is the actual urea flow rate pumped out from the urea tank per unit time, and ηv is a volumetric efficiency of the urea pump.

[0011] Further, the expression for calculating the displacement of the urea pump is, wherein V is the displacement of the urea pump, m is the gear modulus of the urea pump, z is the gear tooth number of the urea pump, and b is the gear tooth width of the urea pump.

[0012] Further, a shutdown working time is set, after the engine is shut down, the actual temperature inside the nozzle coil is obtained, the urea pump continues to run for the shutdown working time, and the speed of the urea pump is calibrated according to the actual temperature inside the nozzle coil to reduce the temperature inside the nozzle coil.

[0013] A urea overflow cooling urea nozzle system, comprising, a urea nozzle for spraying urea solution into an exhaust treatment system of an engine; a urea pump for driving circulation flow of the urea solution; a urea tank for storing the urea solution; a temperature sensor for detecting real-time temperature of a urea nozzle coil and outputting a temperature detection signal; an ECU receiving the temperature detection signal and applying the above-mentioned urea overflow cooling control method to control the urea pump according to the temperature detection signal to reduce the temperature inside the urea nozzle.

[0014] Advantages The present application has the advantages that: The present application uses urea pump overflow urea solution as a cooling medium, sets a target temperature inside the nozzle coil and a target urea overflow flow rate, obtains an actual urea pump speed, calibrates a required urea overflow flow rate according to the target temperature inside the nozzle coil, obtains a target urea pump speed according to the target urea overflow flow rate and the required urea overflow flow rate, obtains a target urea overflow flow rate according to the target urea pump speed, reduces the temperature inside the urea nozzle according to the target urea overflow flow rate, and realizes efficient cooling of the urea nozzle, optimizes the cooling effect of the urea nozzle, and improves the environmental adaptability and operation efficiency of cooling. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A flow chart of the urea overflow cooling control method of the present application; Figure 2 A general structure diagram of the urea nozzle system of the present application; Figure 3 An internal structure diagram of the urea nozzle of the present application; Figure 4 A coil temperature comparison diagram of different cooling modes of the engine after DPF regeneration of the present application; Figure 5 ​This is a schematic diagram showing the change between the target temperature inside the nozzle coil and the required urea overflow flow rate according to the present invention.

[0016] Among them: 1-Urea nozzle, 2-Urea pump, 3-Urea tank, 4-Temperature sensor, 5-Urea nozzle valve core, 6-Nozzle valve core coil. Detailed Implementation

[0017] 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 Figures 1-5 The present invention provides a method for controlling urea overflow cooling, such as... Figure 1 As shown, the method involves setting the target temperature and target urea overflow flow rate inside the nozzle coil, and then obtaining the actual urea pump speed, such as... Figure 5 As shown, the required urea overflow flow rate is calibrated based on the target temperature inside the nozzle coil, and the target urea pump speed is obtained based on the target urea overflow flow rate and the required urea overflow flow rate.

[0018] The method for obtaining the target urea pump speed based on the target urea overflow flow rate and the required urea overflow flow rate is as follows: the difference between the target urea overflow flow rate and the required urea overflow flow rate is obtained; the urea overflow flow rate difference is used for PID control to obtain a control signal; the control signal is input into the ECU; the ECU sets the target urea pump speed according to the control signal; and the ECU calibrates the urea overflow flow rate closed-loop correction coefficient according to the control signal to correct the urea overflow flow rate difference.

[0019] The expression for the control signal obtained by applying PID control to the urea overflow flow difference is as follows: ; in, e(t) This is the difference in urea overflow flow rate. K p It is proportional gain. K i It is integral gain. K d It is the differential gain. de (t) / dt The rate of change of error represents the error. e(t) Regarding time t derivative , U(t) To control the signal quantity. Error. e(t) Increase control signals during rapid changes. U(t), To quickly reduce errors; when errors e(t) Reduce control signals when changes are slow or tend to stabilize. U(t), To avoid overreacting.

[0020] The maximum pump speed correction coefficient and the minimum pump speed correction coefficient are set, and when the urea overflow flow closed-loop correction coefficient is greater than or equal to the maximum pump speed correction coefficient, the urea overflow flow closed-loop correction coefficient is equal to the maximum pump speed correction coefficient; when the urea overflow flow closed-loop correction coefficient is less than or equal to the minimum pump speed correction coefficient, the urea overflow flow closed-loop correction coefficient is equal to the minimum pump speed correction coefficient.

[0021] The target urea overflow flow is obtained according to the target urea pump speed, and the temperature inside the urea nozzle is reduced according to the target urea overflow flow.

[0022] The method for obtaining the target urea overflow flow according to the target urea pump speed is, The actual nozzle injection amount per unit time Q2, the gear modulus of the urea pump, the gear tooth number of the urea pump, and the gear tooth width of the urea pump are obtained, the displacement of the urea pump is calculated according to the gear modulus of the urea pump, the gear tooth number of the urea pump, and the gear tooth width of the urea pump, the theoretical urea flow per unit time pumped from the urea tank is calculated according to the displacement of the urea pump and the target urea pump speed, the actual urea flow per unit time pumped from the urea tank Q1 is calculated according to the theoretical urea flow per unit time pumped from the urea tank, and the target urea overflow flow Q is obtained by subtracting the actual nozzle injection amount per unit time Q2 from the actual urea flow per unit time pumped from the urea tank Q1.

[0023] The expression for calculating the theoretical urea flow per unit time pumped from the urea tank according to the displacement of the urea pump and the target urea pump speed is, ; Wherein, Q0 is the urea flow per unit time pumped from the urea tank, V is the displacement of the urea pump, and N is the target urea overflow flow.

[0024] The expression for calculating the actual urea flow per unit time pumped from the urea tank is, ; Wherein, Q0 is the urea flow per unit time pumped from the urea tank, Q1 is the actual urea flow per unit time pumped from the urea tank, and ηv is the volumetric efficiency of the urea pump.

[0025] The volumetric efficiency refers to the ratio of the actual flow to the theoretical flow, and reflects the efficiency loss of the pump in actual operation due to factors such as leakage. The volumetric efficiency is usually represented by ηv, and its value is usually 0.9.

[0026] The expression for calculating the displacement of the urea pump is, ; Wherein, V is the displacement of the urea pump, m is the gear modulus of the urea pump, the unit is meter; z is the gear tooth number of the urea pump; b is the gear tooth width of the urea pump, the unit is meter. The structure in the urea pump 2 is a gear pump, and the working principle is that two intermeshing gears rotate in the pump body to form a low pressure area and a high pressure area, thereby realizing the suction and discharge of urea. The displacement of the urea pump 2 refers to the volume of urea that the pump can discharge when the gear rotates one revolution, and the unit is cubic meters per revolution.

[0027] The shutdown working time is set, the actual temperature inside the nozzle coil is obtained after the engine is stopped, the urea pump continues to run for the shutdown working time, and the speed of the urea pump is calibrated according to the actual temperature inside the nozzle coil to reduce the temperature inside the nozzle coil. Further change the urea overflow flow in the urea nozzle cooling flow channel. This process can conduct the heat of the urea nozzle 1 to the urea tank 3 through the urea solution, significantly reduce the temperature inside the nozzle, and ensure that the urea nozzle 1 can also be fully cooled after the engine is stopped.

[0028] As shown in Figure 2 A urea overflow cooling urea nozzle system, which comprises, The urea nozzle 1 is used for spraying urea solution into the exhaust treatment system of the engine.

[0029] The urea pump 2 is used for driving the circulation flow of the urea solution.

[0030] The urea tank 3 is used for storing the urea solution.

[0031] The temperature sensor 4 is used for detecting the real-time temperature of the urea nozzle coil and outputting a temperature detection signal.

[0032] After the engine is warmed up, the temperature of the urea is obviously lower than the temperature of the engine coolant, and the cooling capacity of the urea is superior to that of the coolant.

[0033] The ECU receives the temperature detection signal and applies the above-mentioned control method of urea overflow cooling to control the urea pump 2 according to the temperature detection signal to adjust the overflow flow of the urea solution to reduce the temperature inside the urea nozzle 1.

[0034] The present application uses the urea pump overflow urea solution as the cooling medium, (as Figure 1 The urea overflow liquid and the liquid return port are marked. When the urea solution is sprayed in excess, the excess urea solution will be discharged through the overflow port) according to the proposed urea overflow flow calculation formula and combined with the PID closed-loop control logic, as Figure 4 As shown, efficient cooling of the urea nozzle is realized. At the same time, by continuing to run the urea pump after the engine is stopped, using the engine exhaust heat to thaw and thaw, and promoting the urea hydrolysis reaction, the cooling effect, environmental adaptability and operating efficiency of the system are further optimized.

[0035] The above description is only the preferred embodiment of the present application, it should be pointed out that for those skilled in the art, without departing from the structure of the present application, several modifications and improvements can be made, which will not affect the effect and practicality of the patent.

Claims

1. A control method of urea overflow cooling, characterized by, The method comprises the following steps: setting a target temperature inside a nozzle coil and a target urea overflow flow, obtaining an actual urea pump rotating speed, calibrating a required urea overflow flow according to the target temperature inside the nozzle coil, obtaining a target urea pump rotating speed according to the target urea overflow flow and the required urea overflow flow, obtaining a target urea overflow flow according to the target urea pump rotating speed, and reducing the temperature inside the urea nozzle according to the target urea overflow flow.

2. A control method of urea overflow cooling according to claim 1, characterized in that, The method for obtaining the target urea pump rotating speed according to the target urea overflow flow and the required urea overflow flow comprises the following steps: The target urea overflow flow and the required urea overflow flow are subtracted to obtain a urea overflow flow difference value, the urea overflow flow difference value is subjected to PID control to obtain a control signal amount, the control signal amount is input into an ECU, the ECU sets a target urea pump rotating speed according to the control signal amount, and the ECU calibrates a urea overflow flow closed-loop correction coefficient according to the control signal amount.

3. A control method of urea overflow cooling according to claim 2, characterized in that, The expression for obtaining the control signal amount by subjecting the urea overflow flow difference value to PID control is as follows: ； wherein, e(t) is the urea overflow flow difference, K p is a proportional gain, K i is an integral gain, K d is a derivative gain, de(t) / dt is a rate of change of error, U(t) is a control signal quantity.

4. A control method of urea overflow cooling according to claim 2, characterized in that, A maximum pump rotating speed correction coefficient and a minimum pump rotating speed correction coefficient are set, when the urea overflow flow closed-loop correction coefficient is greater than or equal to the maximum pump rotating speed correction coefficient, the urea overflow flow closed-loop correction coefficient is equal to the maximum pump rotating speed correction coefficient, and when the urea overflow flow closed-loop correction coefficient is less than or equal to the minimum pump rotating speed correction coefficient, the urea overflow flow closed-loop correction coefficient is equal to the minimum pump rotating speed correction coefficient.

5. A control method of urea overflow cooling according to claim 1, characterized in that, The method for obtaining the target urea overflow flow according to the target urea pump rotating speed comprises the following steps: The actual nozzle injection amount per unit time, the gear modulus of the urea pump, the gear tooth number of the urea pump and the gear tooth width of the urea pump are obtained, the displacement of the urea pump is calculated according to the gear modulus of the urea pump, the gear tooth number of the urea pump and the gear tooth width of the urea pump, the theoretical urea flow pumped out from the urea tank per unit time is calculated according to the displacement of the urea pump and the target urea pump rotating speed, the actual urea flow pumped out from the urea tank per unit time is calculated according to the theoretical urea flow pumped out from the urea tank per unit time, and the target urea overflow flow is obtained by subtracting the actual nozzle injection amount per unit time from the actual urea flow pumped out from the urea tank per unit time.

6. A control method of urea overflow cooling according to claim 5, characterized in that, The expression for calculating the theoretical urea flow pumped out from the urea tank per unit time according to the displacement of the urea pump and the target urea pump rotating speed is as follows: ； wherein Q0 represents the urea flow pumped out from the urea tank per unit time, V represents the displacement of the urea pump, and N represents the target urea overflow flow.

7. A control method of urea overflow cooling according to claim 5, characterized in that, The expression for calculating the actual urea flow pumped out from the urea tank per unit time according to the theoretical urea flow pumped out from the urea tank per unit time is as follows: ； wherein Q0 represents the urea flow pumped out from the urea tank per unit time, Q1 represents the actual urea flow pumped out from the urea tank per unit time, and ηv represents the volumetric efficiency of the urea pump.

8. A control method of urea overflow cooling according to claim 5, characterized in that, The expression for calculating the displacement of the urea pump is as follows: ； wherein V represents the displacement of the urea pump, m represents the gear modulus of the urea pump, z represents the gear tooth number of the urea pump, and b represents the gear tooth width of the urea pump.

9. A control method of urea overflow cooling according to claim 1, characterized in that, Set the shutdown working time, after the engine is shut down, the actual temperature inside the nozzle coil is obtained, the urea pump continues to run for the shutdown working time, and the speed of the urea pump is calibrated according to the actual temperature inside the nozzle coil to reduce the temperature inside the nozzle coil.

10. A urea spill cooled urea nozzle system characterized by, It includes, A urea nozzle (1) for spraying urea solution into an exhaust treatment system of an engine; A urea pump (2) for driving circulation flow of the urea solution; A urea tank (3) for storing the urea solution; A temperature sensor (4) for detecting real-time temperature of a urea nozzle coil and outputting a temperature detection signal; An ECU receiving the temperature detection signal and applying a urea overflow cooling control method according to any one of claims 1-9 to control the urea pump (2) to reduce the temperature inside the urea nozzle (1).

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