Disclosure of Invention
In view of the above, the present invention provides a control method for a urea injection system, which can improve the atomization effect of urea and reduce the risk of urea crystallization when the exhaust temperature is low. It is another object of the present invention to provide a urea injection system, as well as a controller and storage medium.
In order to achieve the purpose, the invention provides the following technical scheme:
a method of controlling a urea injection system, comprising the steps of:
acquiring the exhaust temperature in an exhaust pipe and the temperature of a urea solution in a urea supply pipeline;
when the exhaust temperature is lower than a preset exhaust temperature, calculating the saturation temperature of the urea solution corresponding to the exhaust pressure based on the exhaust pressure in the exhaust pipe;
when the temperature of the urea solution is lower than the saturation temperature, determining that the temperature control mode of the urea solution in the urea supply pipeline is as follows: increasing to above the saturation temperature.
The working principle of the invention is as follows: when exhaust temperature is less than preset exhaust temperature, the risk of urea crystallization increases, and this scheme rises the temperature of urea solution to above the saturation temperature of the urea solution that the exhaust pressure corresponds, and in the urea injection process, when urea nozzle internal pressure reduces below the saturation pressure, the urea solution can produce the flash boiling, and the quick expansion of gaseous phase can make the urea solution atomize into very tiny liquid drop to improve urea atomization effect, reduce the urea crystallization risk when exhaust temperature is low.
Preferably, when the exhaust gas temperature in the exhaust pipe and the urea solution temperature in the urea supply line are obtained, the exhaust gas pressure in the exhaust pipe is also obtained.
Preferably, when the exhaust temperature is greater than or equal to a preset exhaust temperature, a control command is output: and controlling the urea nozzle to spray the urea solution.
Preferably, when the urea solution temperature is equal to or higher than the saturation temperature, a control command is output: and controlling the urea nozzle to spray the urea solution.
Preferably, when the urea solution temperature is less than the saturation temperature, the temperature control manner of the urea solution in the urea supply line is determined as follows: and increasing the temperature to be above the saturation temperature, and outputting a control instruction: heating the urea solution in the urea supply pipeline according to the temperature control mode;
when the temperature of the urea solution is greater than or equal to the saturation temperature, outputting a control command: and controlling the urea nozzle to spray the urea solution.
The invention also provides a controller comprising a memory for storing a program and a processor for executing the program and implementing a method of controlling a urea injection system as described in any one of the above.
The present invention also provides a urea injection system comprising:
a first temperature sensor for detecting a temperature of exhaust gas in the exhaust pipe;
a second temperature sensor for detecting a temperature of the urea solution in the urea supply line;
a urea heating device disposed in the urea supply line;
a controller as described above is also included.
Preferably, the urea injection system further comprises a urea pump and a urea nozzle for injecting urea solution, a pressure pipe and the second temperature sensor are arranged on the urea supply pipeline between the urea pump and the urea nozzle, and the urea heating device is a heating resistance wire arranged in the pressure pipe.
The invention also provides a storage medium having stored thereon a computer program which, when being executed by a processor, carries out the individual steps of the method of controlling a urea injection system as defined in any one of the preceding claims.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 3, the present invention provides a control method of a urea injection system, which specifically includes the following steps:
s100: the exhaust gas temperature in the exhaust pipe 9 and the urea solution temperature in the urea supply line 4 are obtained. In step S100, the exhaust gas temperature in the exhaust pipe 9 may be detected by the first temperature sensor 6, and the urea solution temperature in the urea supply line 4 may be detected by the second temperature sensor 7. Preferably, in step S100, the exhaust pressure in the exhaust pipe 9 is also obtained, and may be detected by a pressure sensor on the exhaust pipe 9. The data of the exhaust temperature, the urea solution temperature, the exhaust pressure and the like detected in the step can be sent to the control unit, so that the data can be acquired.
S200: and judging whether the exhaust temperature is lower than the preset exhaust temperature, if so, entering the step S300. Preferably, when the result of the determination in this step is no, that is, when the exhaust temperature is equal to or higher than the preset exhaust temperature, since the exhaust temperature is high, the mixing effect of the urea solution and the exhaust gas can be ensured, and the risk of urea crystallization can be reduced, the process proceeds to step S800 to perform urea injection. The step S200 may be performed by a control unit alone, and the control unit may store a preset exhaust temperature (for example, 250 ℃, and a specific temperature value may be calibrated) in advance.
S300: based on the exhaust pressure in the exhaust pipe 9, the saturation temperature of the urea solution corresponding to the exhaust pressure is calculated. This step S300 may be performed by the control unit alone. The saturation temperature is a temperature at which the liquid and the vapor are in a dynamic equilibrium state, i.e., a saturated state. In the saturated state, the temperatures of the liquid and vapor are equal. When the saturation temperature is constant, the saturation pressure is also constant; conversely, the saturation temperature is constant when the saturation pressure is constant.
S400: judging whether the temperature of the urea solution is less than the saturation temperature (for example, 100 ℃, and the specific temperature value corresponds to the exhaust pressure and can be calibrated), and if so, entering the step S500; preferably, when the result of the determination in this step is no, that is, when the urea solution temperature is equal to or higher than the saturation temperature, the process proceeds to step S800. This step S400 may be performed by the control unit alone.
S500: the temperature control mode for the urea solution in the urea supply line 4 is determined as follows: increasing to above the saturation temperature. The step determines a temperature control strategy of the urea solution in the urea supply pipeline, and the urea is sprayed to realize flash boiling under the low-speed and low-load working condition through heating according to the control strategy, so that the urea atomization effect is improved, and the urea crystallization risk is reduced. Further preferably, the control method further proceeds to the following step S600 after the step S500 determines the temperature control manner of the urea solution.
S600: and (3) outputting a control command: the urea solution in the urea supply line 4 is heated in the temperature control manner. In step S600, a control command may be output by the control unit to a urea temperature control element, such as a heating resistance wire 2, or a PTC heating element, or the like. The urea solution in the urea supply line 4 is heated by the urea temperature control element. Meanwhile, the process advances to step S700.
S700: judging whether the temperature of the urea solution is less than the saturation temperature, if so, returning to the step S600 to continue heating the urea solution; if not, the heating of the urea solution is stopped, and the process proceeds to step S800. This step S700 may be performed by the control unit alone.
S800: and (3) outputting a control command: the urea nozzle 8 is controlled to inject urea solution. In this step S800, a control command may be output to the urea nozzle 8 by the control unit, thereby realizing the open/close control of the urea nozzle 8.
The working principle of the invention is as follows: when the exhaust temperature in the exhaust pipe 9 is lower than the preset exhaust temperature (for example, 250 ℃ and can be calibrated), the risk of urea crystallization is increased, the scheme raises the temperature of the urea solution to be higher than the saturation temperature (for example, 100 ℃ and can be calibrated) of the urea solution corresponding to the exhaust pressure, in the urea injection process, when the pressure in the urea nozzle 8 is reduced to be lower than the saturation pressure corresponding to the temperature of the urea solution, the urea solution enters a metastable overheating zone, at this time, a large amount of bubbles are generated in the urea solution, and as the pressure is further reduced, the bubbles will grow gradually, when the urea pressure is lower than the pressure corresponding to the overheat limit, part of the urea solution can be explosively vaporized to generate flash boiling, and the urea solution can be atomized into very fine liquid drops through the rapid expansion of the gas phase, so that the urea atomization effect is improved, and the urea crystallization risk when the exhaust temperature is low is reduced. Among them, flash boiling is a phenomenon in which a jet liquid is rapidly vaporized and well mixed with air.
The invention also provides a controller comprising a memory and a processor. The memory may include, among other things, high-speed RAM memory, and may also include non-volatile memory, such as at least one disk memory. The processor may be a central processing unit CPU, or an application Specific Integrated circuit asic, or one or more Integrated circuits configured to implement embodiments of the present invention, or the like. Preferably, the controller in the scheme adopts a vehicle control unit ECU.
Wherein the memory is configured to store a program, and the processor is configured to execute the program, the program being configured to implement the respective steps of the control method of the urea injection system described above:
acquiring the exhaust temperature in an exhaust pipe and the temperature of a urea solution in a urea supply pipeline;
when the exhaust temperature is lower than a preset exhaust temperature, calculating the saturation temperature of the urea solution corresponding to the exhaust pressure based on the exhaust pressure in the exhaust pipe;
when the temperature of the urea solution is lower than the saturation temperature, determining that the temperature control mode of the urea solution in the urea supply pipeline is as follows: increasing to above the saturation temperature.
Alternatively, the detailed function and the extended function of the program may refer to the above description.
The present invention also provides a storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the control method of the urea injection system described above:
acquiring the exhaust temperature in an exhaust pipe and the temperature of a urea solution in a urea supply pipeline;
when the exhaust temperature is lower than a preset exhaust temperature, calculating the saturation temperature of the urea solution corresponding to the exhaust pressure based on the exhaust pressure in the exhaust pipe;
when the temperature of the urea solution is lower than the saturation temperature, determining that the temperature control mode of the urea solution in the urea supply pipeline is as follows: increasing to above the saturation temperature.
The storage medium includes: u disk, removable hard disk, read only memory, random access memory, magnetic or optical disk, etc. for storing program codes.
Alternatively, the detailed function and the extended function of the program may refer to the above description.
The present invention also provides a urea injection system comprising:
a first temperature sensor 6 for detecting the exhaust gas temperature in the exhaust pipe 9;
a second temperature sensor 7 for detecting the temperature of the urea solution in the urea supply line 4;
a urea heating device provided in the urea supply line 4;
a controller as described above is also included.
Preferably, the urea injection system further comprises a urea tank for containing the urea solution, a urea pump 3 for supplying the urea solution to the urea nozzle 8, and the urea nozzle 8 for injecting the urea solution, the urea supply line 4 between the urea pump 3 and the urea nozzle 8 is provided with a pressure tube 5 and a second temperature sensor 7, and the urea heating device may employ a heating resistance wire, or a PTC heating element, or the like. Preferably, the urea heating device in the present solution is a heating resistance wire 2 arranged inside the pressure tube 5, as shown in fig. 1. The hollow arrows in fig. 1 represent the direction of exhaust gas flow inside the exhaust pipe 9.
Referring to fig. 2, the on-off control principle of the heating resistance wire 2 is as follows: when the exhaust temperature is lower than the preset exhaust temperature (for example, 250 ℃ can be calibrated), and the temperature of the urea solution is lower than the saturation temperature (for example, 100 ℃ can be calibrated), the control circuit of the heating resistance wire 2 is switched on, so that the heating of the urea solution is realized. And if the exhaust temperature is more than or equal to the preset exhaust temperature, or when the temperature of the urea solution is heated to be higher than the saturation temperature, the control circuit of the heating resistance wire 2 is disconnected, and the heating of the urea solution is stopped.
The specific implementation process of the urea injection system provided by the scheme is as follows: when the engine is at low speed and low load, the exhaust temperature may be lower than 250 ℃. When the exhaust temperature is below 250 ℃, the risk of urea crystallization increases. At this moment, start heating resistor wire 2 in the pressure pipe 5, stop heating after heating urea temperature to 100 ℃, urea is spouted with the flash boiling form from the 8 exports of mechanical urea nozzle, can show the mixed effect that improves urea and carminative, reduces urea crystallization risk. When the exhaust temperature is higher than 250 ℃, the heating of the heating resistance wire 2 in the pressure pipe 5 is closed, and at the moment, the urea enters the exhaust pipe 9 at the conventional temperature, so that the mixing effect of the urea and the exhaust gas can be ensured, and the crystallization risk of the urea can be reduced.
The invention adopts the urea pump 3 with flow metering function, matches with the mechanical urea nozzle 8, adds a temperature sensor in the urea supply pipeline 4, and adds control logic, thus having little change to the system and remarkable effect.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.