Method for metering an exhaust gas reducing agent and computer program product

Abstract

The present application provides a kind of exhaust reductant metering method, for the metering device of exhaust reductant, the metering device includes supply module and metering module, the supply module is communicated with reductant tank by suction pipeline and reflux pipeline liquid, including the delivery pump of suction reductant, the pressure pipeline connected with the delivery pump of metering module, the pressure sensor for measuring the pressure on pressure pipeline is arranged on the pressure pipeline, one end of the reflux pipeline is connected to pressure pipeline one end is connected to the reductant tank, the suction pump is arranged on the reflux pipeline, including the pressure building step, the delivery pump builds pressure in pressure pipeline;Pressure test step, test whether the pressure in pressure pipeline is greater than normal pressure, if the result of pressure test step is "yes", then enter pressure maintaining step;If the result of pressure test step is "no", then enter metering step;Pressure maintaining step, after reductant is kept in the reflux pipeline for a predetermined time, enter pressure building step;Metering step, reductant is metered in a predetermined manner.The problem that prior art cannot quickly build pressure under icing condition can be solved.

Description

Technical Field

[0001] This application relates to the field of diesel engine exhaust gas treatment, and more particularly to a metering method and computer program product for exhaust gas reducing agent. Background Technology

[0002] To meet environmental regulations, spontaneous combustion engines often incorporate SCR catalytic converters in their exhaust systems. These SCR catalytic converters are capable of removing NOx contained in the exhaust gases. x The compound is converted into water and nitrogen. The reductant is then injected upstream of the SCR catalyst into the exhaust manifold. The reductant used in the exhaust is, for example, an aqueous solution of liquid urea. To achieve this, a metering device is introduced, comprising a supply module and a metering module. The supply module draws the reductant from the reductant tank, and the metering module, similar to the injector in a fuel injection system, injects the reductant into the exhaust manifold. The supply and metering modules are controlled by a controller. The supply module includes a suction pump, which has a certain reserve when drawing in the reductant. Excess reductant is returned to the reductant tank via a return line after each injection by a backflow pump, thus ensuring stable pressure in the pressure line from the suction pump to the metering module.

[0003] A connecting pipe is installed on the return line between the supply module and the reducing agent tank. After the internal combustion engine stops working, some reducing agent remains in the connecting pipe. At low temperatures, the remaining reducing agent may freeze. The solid reducing agent in the connecting pipe can block the return channel of the reducing agent when the reducing agent is supplied again, thus preventing the formation of stable pressure on the pressure line. When stable pressure cannot be formed, the reducing agent metering device cannot start working.

[0004] A quick solution to the above problems is needed. Summary of the Invention

[0005] The purpose of this invention is to provide a metering method for waste gas reducing agents and a computer program product thereof.

[0006] To achieve the above-mentioned objectives, this invention provides a method for metering a waste gas reducing agent, and a metering device for the waste gas reducing agent. The metering device includes a supply module and a metering module. The supply module and the reducing agent tank are connected via a suction pipeline and a return pipeline. The device includes a pump for suctioning the reducing agent, a pressure pipeline connecting the metering module and the pump, a pressure sensor installed on the pressure pipeline for measuring the pressure on the pressure pipeline, a return pipeline with one end connected to the pressure pipeline and the other end connected to the reducing agent tank, and a backflow pump installed on the return pipeline. The method includes the following steps:

[0007] In the pressure building step, the delivery pump builds pressure in the pressure pipeline;

[0008] The pressure test procedure checks whether the pressure in the pressure line is greater than the normal pressure. If the result of the pressure test procedure is "yes", then proceed to the pressure holding procedure; if the result of the pressure test procedure is "no", then proceed to the metering procedure.

[0009] The pressure holding step involves maintaining the reducing agent in the reflux line for a predetermined time before proceeding to the pressure build-up step.

[0010] The metering procedure involves metering the reducing agent according to a predetermined method.

[0011] The present invention also provides a computer program product, which can implement the above-described method for metering waste gas reducing agent when it is run.

[0012] Using the technical solution provided by this invention, the metering system for waste gas reducing agent can be restored to normal operation as soon as possible. Attached Figure Description

[0013] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments described below are for illustrative purposes only and do not limit the scope of this application. In the accompanying drawings:

[0014] Figure 1 This is a structural block diagram of a metering device using the metering method for the waste gas reducing agent of the present invention;

[0015] Figure 2 This is a flowchart of the metering method for the waste gas reducing agent of the present invention. Detailed Implementation

[0016] It should be understood that the accompanying drawings are for illustrative purposes only.

[0017] Please see Figure 1The diagram shows a structural block diagram of a metering device using the metering method for the exhaust gas reducing agent of this invention. In this embodiment, the metering device is used in a diesel engine exhaust gas treatment system and includes a supply module and a metering module 5. As shown in the dashed box in the diagram, the supply module is in liquid communication with the reducing agent tank 1 via a suction line 11 and a return line 13. It draws the reducing agent from the suction line 11 and returns the reducing agent to the reducing agent tank 1 via the return line 13. The supply module also includes a delivery pump 3, one end of which is connected to the suction line 11. A pre-filter 2 is installed on the suction line 11. In this embodiment, the delivery pump 3 also includes a one-way valve (not labeled), which is connected to the metering module 5 via a pressure line 12. A main filter 16 and a pressure sensor 4 are installed on the pressure line 12. The pressure sensor 4 can measure the real-time pressure value on the pressure line 12. A return line 13 is connected to the pressure line 12. In this embodiment, the return line 13 is located downstream of the main filter 16, and its other end is connected to the reducing agent line 1. Parallel liquid circuits are provided on the return line 13, each equipped with a backflow pump 7 and a valve unit 6. The valve unit 6 includes a throttle valve, and the backflow pump 7 includes a reversing valve 10. The return line 13 downstream of the valve unit 6 and the backflow pump 7 is connected at one point and returns to the reducing agent tank 1 via a connecting pipe 9. An electric heating device (not shown) is provided in the reducing agent tank 1, while no heating device is provided in the connecting pipe 9. The metering device is controlled by a controller (not shown) for its normal metering operation. The metering method of this invention is also controlled by a controller, which is generally a controller for a diesel engine exhaust gas treatment system, but can also be any other controller configured to control the operation of the metering device. In this embodiment, the reducing agent is an aqueous urea solution.

[0018] Under normal conditions, the suction pump 3 in the supply module draws reducing agent from the reducing agent tank 1. Under the control of the controller, the supply module draws slightly more reducing agent than the metering module 5 needs to inject to maintain sufficient pressure in the supply module. Excess reducing agent flows back to the reducing agent tank 1 through the throttle valve in the valve unit 6. After the metering operation is completed, the back suction pump 7 attempts to completely empty the reducing agent in the supply module to prevent residual reducing agent from freezing at low temperatures. However, in practice, reducing agent tends to remain in the connecting pipe 9 downstream of the back suction pump 7, making complete emptying impossible and leading to the formation of solid reducing agent in the connecting pipe 9. At the start of the next metering operation, effective backflow cannot be formed, resulting in the inability to establish stable pressure within the supply module.

[0019] Please see Figure 2The flowchart shown is for the metering method of exhaust gas reducing agent according to the present invention. After the diesel engine system is started, the pressure building step S001 is performed first. The delivery pump 3 draws reducing agent from the reducing agent tank 1 through the suction line 11 and attempts to build pressure in the pressure line 12. Then, in the pressure testing step S002, it is tested whether the pressure in the pressure line 12 is greater than the normal pressure. In this embodiment, the real-time pressure in the pressure line 12 is obtained in real time by the pressure sensor 4. The normal pressure value is preset in the controller of the metering device in this embodiment. The normal pressure value is determined by comparing the measured value of the pressure sensor 4 with the normal pressure value. If the test result is "yes", the pressure holding step S003 is performed. If the test result is "no", the metering step S004 is performed. In other embodiments, the normal pressure value is expressed as a pressure corresponding value that changes with the pressure building time. This correspondence is set in the controller. For example, the normal pressure value after 5 seconds of pressure building and the normal pressure value after 10 seconds of pressure building are shown. The pressure in pressure line 12 is determined by comparing the pressure value measured by pressure sensor 4 at a specific pressure build-up time with the preset pressure value at that specific time. The normal pressure value or pressure curve can be calculated or obtained through practice. In pressure holding step S003, the reducing agent is kept in return line 13, thereby allowing the liquid reducing agent to flush or heat the solid reducing agent in return line 13, especially the solid reducing agent in connecting pipe 9. Of course, if the reducing agent in reducing agent tank 1 also freezes after the diesel engine starts, it can be heated to a liquid state using the electric heating device in reducing agent tank 1 before starting pressure build-up. After holding the reducing agent in return line 13 for a predetermined time, pressure build-up step S001 is entered again to attempt pressure build-up, followed by pressure testing step S002. If the normal pressure is successfully reached again, the metering step S004 is entered; otherwise, the cycle repeats to pressure holding step S003. The pressure holding step S003 can be completed by suction pump 3 or by back suction pump 7. Of course, in actual operation, the solid reducing agent in connecting pipe 9 may not completely block the reducing agent reflux, and the amount of reducing agent reflux gradually increases as the solid reducing agent melts. In other embodiments, the above-mentioned normal pressure value can also be expressed as a precise pressure value or as a pressure range.

[0020] In other embodiments, for example, in the pressure test step S002, if the test result is "no", before proceeding to the metering step S004, there is a step to determine whether the pressure in the pressure pipeline is significantly lower than the normal pressure. If it is not significantly lower than the normal pressure, then proceed to the metering step S004. If it is significantly lower than the normal pressure, the supply module finds the cause and makes corrections under the control of the controller. This will not be elaborated further here.

[0021] The present invention also includes a computer program product, which, when run, can implement the measurement method of the present invention, and the computer program product is stored in the controller.

[0022] The metering method and computer program of this invention can heat the solid reducing agent remaining in the return pipeline, especially the connecting pipe, which does not have a heating device, by using the liquid reducing agent, thereby enabling the metering device to work normally more quickly.

Claims

1. A metering method for a waste gas reducing agent, and a metering device for the waste gas reducing agent, the metering device comprising a supply module and a metering module (5), the supply module being liquid-connected to a reducing agent tank (1) via a suction line (11) and a return line (13), comprising a delivery pump (3) for absorbing the reducing agent, a pressure line (12) connecting the metering module (5) and the delivery pump (3), a pressure sensor (4) installed on the pressure line (12) for measuring the pressure on the pressure line, one end of the return line (13) being connected to the pressure line (12) and the other end being connected to the reducing agent tank (1), and a back-suction pump (7) installed on the return line (13), comprising the following steps, In the pressure building step, the delivery pump (3) builds up pressure in the pressure line (12); The pressure test step tests whether the pressure in the pressure line (12) is greater than the normal pressure. If the result of the pressure test step is "yes", then proceed to the pressure holding step; if the result of the pressure test step is "no", then proceed to the metering step. The pressure holding step allows the reducing agent to remain in the reflux line (13) for a predetermined time before proceeding to the pressure build-up step; The metering procedure involves metering the reducing agent according to a predetermined method.

2. The method for metering the waste gas reducing agent as described in claim 1, wherein, The reducing agent is drawn from the reducing agent tank (1) by the delivery pump (3) and pressure is established in the pressure line (12).

3. The method for metering the waste gas reducing agent as described in claim 2, wherein, The normal pressure in the pressure line (12) is preset in the controller of the metering device. The pressure in the pressure line (12) is determined to be greater than the normal pressure by comparing the pressure value measured by the pressure sensor (4) with the preset pressure value.

4. The method for metering the waste gas reducing agent as described in claim 2, wherein, The normal pressure in the pressure line (12) is preset in the controller of the metering device according to the corresponding value of the pressure build-up time. The pressure in the pressure line (12) is determined to be greater than the normal pressure by comparing the pressure value measured by the pressure sensor (4) at a specific pressure build-up time with the preset pressure value at that specific time.

5. The method for metering the waste gas reducing agent as described in claim 3 or 4, wherein, If the result of the pressure test step is "no", there is a step to determine whether the pressure in the pressure pipeline is lower than the normal pressure before proceeding to the metering step. If it is not lower than the normal pressure, then proceed to the metering step.

6. The method for metering the waste gas reducing agent as described in any one of claims 1 to 4, wherein, The return line (13) has a valve unit (6) connected in parallel with the back suction pump (7).

7. The method for metering the waste gas reducing agent as described in any one of claims 1 to 4, wherein, The suction line (11) has a pre-filter (2), the pressure line (12) has a main filter (8), and the back suction pump (7) includes a reversing valve (10).

8. The method for metering the waste gas reducing agent as described in any one of claims 1 to 4, wherein, A connecting pipe (9) is provided on the reflux pipeline (13) between the backflow pump (7) and the reducing agent tank (1). The connecting pipe (9) does not have a heating device, while the reducing agent tank (1) is equipped with a heating device.

9. The method for metering the waste gas reducing agent as described in any one of claims 1 to 4, wherein, The reducing agent is an aqueous solution of urea, and the metering device is used in a diesel engine.

10. A computer program product, characterized in that, When it is in operation, it can implement the metering method of the waste gas reducing agent as described in any one of claims 1 to 9.

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