System and method for testing PN emission characteristics of nitrogen oxide reducing agent of diesel engine

Abstract

The invention belongs to the technical field of diesel engine emission reduction, and particularly relates to a diesel engine nitrogen oxide reducing agent PN emission characteristic test system and test method. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system comprises a combustor, a filter, a mixing pipe, an SCR catalyst and an ASC catalyst which are communicated in sequence. The combustor is used for introducing fuel and carrying out combustion reaction; the filter is used for filtering upstream particulate matters generated by combustion reaction; the mixing pipe is used for introducing a nitrogen oxide reducing agent and a simulation gas component, and is used for mixing the filtered combustion product, the nitrogen oxide reducing agent and the simulation gas component to form a mixed gas; the SCR catalyst is used for promoting a catalytic reduction reaction of the mixed gas; the ASC catalyst is used for carrying out ammoxidation reaction; and a downstream particle counter is arranged at an outlet of the ASC catalytic converter. By using the PN emission characteristic test system for the nitrogen oxide reducing agent of the diesel engine in the technical scheme, the particulate matter emission level of the nitrogen oxide reducing agent of the diesel engine can be tested.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine emission reduction, and in particular to a diesel engine nitrogen oxide reducing agent PN emission characteristic testing system and testing method. Background Art

[0002] During the operation of diesel engines, pollutants such as unburned hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter are emitted. If these substances are directly discharged into the air, they will have a great negative impact on the atmospheric environment and human health. As society's awareness of environmental protection increases, the emission regulations of internal combustion engines in various countries around the world are becoming increasingly stringent, thus promoting cleaner emissions; especially for particulate matter, the Euro VI emission standard and the National VI emission standard have given two types of particulate matter emission limits that must be met at the same time, namely, particle mass (PM) and particle number (PN).

[0003] As emission regulations continue to tighten, the emission control measures of diesel engines alone can no longer meet the emission limits of various pollutants. Therefore, it is necessary to add an off-board purification after-treatment system to the exhaust end of the diesel engine. The most commonly used after-treatment system for National VI generally includes four units (ordered from upstream to downstream in the order of airflow) including DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalytic reduction), and ASC (ammonia slip catalyst).

[0004] DOC is an oxidation catalyst with active catalytic components such as precious metals. It can catalyze the reaction of hydrocarbons with oxygen to convert them into harmless water and carbon dioxide. DPF is generally a honeycomb ceramic structure with a wall-flow structure, which can capture most of the particulate matter in the exhaust. SCR can catalyze the oxidation-reduction reaction of nitrogen oxides in the exhaust with oxygen, additionally injected reductants, etc., thereby converting them into harmless water, carbon dioxide, nitrogen, etc. ASC can catalyze the reaction of excess ammonia in SCR with oxygen, thereby converting it into harmless water and carbon dioxide.

[0005] The most commonly used "extra injected reducing agent" in SCR is urea aqueous solution. When urea aqueous solution is injected into the SCR system, urea undergoes a series of thermal decomposition reactions, most of which is converted into ammonia, and then the SCR reaction occurs with ammonia, nitrogen oxides and oxygen. In addition to urea aqueous solution, there are also technical solutions that use ammonia, solid ammonia, hydrogen and carbon compounds as nitrogen oxide reducing agents.

[0006] Under the same diesel engine and post-treatment hardware and the same operating conditions, the diesel engine emission test was conducted without urea injection and with urea injection. The latter had much higher particulate matter emissions than the former. Since the urea nozzle and SCR catalyst of the National VI post-treatment system are both located downstream of the DPF, most of the particulate matter from the original diesel engine in the SCR has been filtered by the DPF. Obviously, the increase in particulate matter mainly comes from a series of physical and chemical reactions between urea injected into the SCR and the gas phase components in the diesel engine exhaust. Theoretically, these increased particulate matter components may include urea thermal decomposition byproducts, ammonium salts, etc.

[0007] Research in recent years has found that even if the test results of urea aqueous solution meet the national or industry standards, the amount of particulate matter emissions caused by different types of urea aqueous solution is different. In theory, there are two reasons: (1) a small amount of impurities are inevitably mixed into the various processes of preparing urea aqueous solution; (2) additives are deliberately mixed into the urea aqueous solution to improve its performance, such as anti-crystallization additives or anti-icing additives.

[0008] Therefore, in order to screen out types of reducing agents with lower particulate matter emission levels, or to monitor the particulate matter emission levels of commercially available reducing agents, there should be a diesel engine nitrogen oxide reducing agent PN emission characteristic test system and test method to systematically test the particulate matter emission levels of different nitrogen oxide reducing agents. Summary of the invention

[0009] The purpose of the present invention is to at least solve the problem of how to test the emission characteristics of particulate matter of a diesel engine nitrogen oxide reducing agent. This purpose is achieved by the following technical solutions:

[0010] The first aspect of the present invention provides a diesel engine nitrogen oxide reducing agent PN emission characteristic test system, comprising a burner, a filter, a mixing pipe, an SCR catalyst and an ASC catalyst connected in sequence;

[0011] The burner is used to introduce fuel, and the fuel can undergo a combustion reaction in the burner;

[0012] The filter is used to filter upstream particulate matter generated by the combustion reaction;

[0013] The mixing tube is used to introduce the nitrogen oxide reducing agent and the simulated gas component, and to mix the filtered combustion products, the nitrogen oxide reducing agent and the simulated gas component to form a mixed gas;

[0014] The SCR catalyst is used to promote the catalytic reduction reaction of the mixed gas;

[0015] The ASC catalyst is used to generate an ammonia oxidation reaction;

[0016] The outlet of the ASC catalyst is provided with a downstream particle counter for measuring the concentration of downstream particulate matter.

[0017] The diesel engine nitrogen oxide reductant PN emission characteristic test system in this technical solution obtains a high-temperature airflow by burning fuel and combustion aid in a burner, simulating the exhaust flow and exhaust temperature of the engine in actual working conditions. The upstream particulate matter generated by the combustion is filtered through a filter, so as to exclude the upstream particulate matter contained in the product of the catalytic reduction reaction as much as possible. The gas components required for the reaction in the actual working conditions, including nitrogen oxide reductant and simulated gas components, are introduced into the mixing tube. After the combustion products, nitrogen oxide reductant and simulated gas components are mixed in the mixing tube, they enter the SCR catalyst for catalytic reduction reaction, and ammonia oxidation reaction occurs in the ASC catalyst. The particulate emission level of the nitrogen oxide reductant is judged according to the particulate concentration after the reaction is stabilized. By replacing the nitrogen oxide reductant, the particulate emission levels of different types of nitrogen oxide reductants can be compared, and it can also be used to monitor the particulate emission levels of commercially available diesel engine nitrogen oxide reductants, thereby eliminating nitrogen oxide reductants with excessively high particulate emission levels and screening out nitrogen oxide reductants with low particulate emission levels for promotion and use.

[0018] In addition, the diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to the present invention may also have the following additional technical features:

[0019] In some embodiments of the present invention, the ASC catalyst is connected to an exhaust gas treatment device, and the exhaust gas treatment device is used to purify exhaust gas.

[0020] In some embodiments of the present invention, a temperature detection unit is provided between the mixing tube and the SCR catalyst, and the temperature detection unit is used to measure the exhaust temperature of the mixed gas.

[0021] In some embodiments of the present invention, a flow detection unit is provided between the filter and the SCR catalyst, and the flow detection unit is used to measure the flow of the gas exhausted from the filter.

[0022] In some embodiments of the present invention, an upstream particle counter is provided between the filter and the SCR catalyst, and the upstream particle counter is used to measure the concentration of upstream particulate matter.

[0023] In some embodiments of the present invention, a gas analyzer is provided at the outlet of the ASC catalyst, and the gas analyzer is used to measure the composition of the gas exhausted by the ASC catalyst.

[0024] The present invention also proposes a diesel engine nitrogen oxide reducing agent PN emission characteristic test method, based on the diesel engine nitrogen oxide reducing agent PN emission characteristic test system in the above embodiment, the diesel engine nitrogen oxide reducing agent PN emission characteristic test method comprises the following steps:

[0025] S100, obtaining a preset flow value of the gas discharged from the filter, a preset exhaust temperature value of the mixed gas, and a preset concentration value of each gas component after the ammonia oxidation reaction, determining an upstream particulate matter concentration limit PN0, and determining the amount of the fuel, the amount of the simulated gas component, and the injection amount of the nitrogen oxide reducing agent;

[0026] S200, without injecting the nitrogen oxide reducing agent, running the diesel engine nitrogen oxide reducing agent PN emission characteristic test system, making the flow value of the gas discharged from the filter equal to the preset exhaust flow value, making the exhaust temperature value of the mixed gas equal to the preset exhaust temperature value, and confirming that the upstream particulate matter concentration value PN1 is less than the upstream particulate matter concentration limit value PN0;

[0027] S300, injecting the nitrogen oxide reducing agent;

[0028] S400, confirming that the concentration value of each gas component after the ammonia oxidation reaction is the same as the preset concentration value of each gas component;

[0029] S500 , recording the upstream particle concentration value PN1 and the downstream particle concentration value PN2 and performing data processing.

[0030] The above diesel engine NOx reductant PN emission characteristic test method simulates the flow, temperature and gas phase components of engine exhaust emissions through a specially built diesel engine NOx reductant PN emission characteristic test system. During the test, the influence of particulate matter emissions in combustion products on the particulate matter emission characteristic test in catalytic reduction products is effectively eliminated, so that the particulate matter emission effect of various NOx reductants can be rigorously and reliably evaluated. This method can be used to monitor the particulate matter emission level of commercially available diesel engine NOx reductants, thereby eliminating NOx reductants with excessively high particulate matter emission levels and screening out NOx reductants with low particulate matter emission levels for promotion and use.

[0031] In some embodiments of the present invention, in S500, the data processing includes calculating the absolute value deviation Σ of the particle emission quantity:

[0032] Σ=PN2-PN1.

[0033] In some embodiments of the present invention, in S500, the data processing includes calculating the absolute value deviation Σ of the particle emission quantity:

[0034] Σ=[(PN2-PN1)-(PN2a-PN1a)] or Σ=[1-(PN2-PN1) / (PN2a-PN1a)];

[0035] Wherein, PN1a is the upstream particulate matter concentration value of the reference nitrogen oxide reducing agent a, and PN2a is the downstream particulate matter concentration value of the reference nitrogen oxide reducing agent a.

[0036] In some embodiments of the present invention, it also includes:

[0037] S600, replacing the nitrogen oxide reducing agent, and repeating S200 to S500;

[0038] S700: Compare the results after data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0040] Figure 1 It is a structural schematic diagram of a diesel engine nitrogen oxide reducing agent PN emission characteristic test system provided by the present invention;

[0041] Figure 2 The present invention provides a flow chart of a method for testing the PN emission characteristics of a diesel engine nitrogen oxide reducing agent.

[0042] In the figure:

[0043] 100. Burner; 200. Filter; 300. Mixing tube; 400. SCR catalyst; 500. ASC catalyst; 600. Exhaust gas treatment device; 10. Flow detection unit; 20. Upstream particle counter; 30. Temperature detection unit; 40. Gas analyzer; 50. Downstream particle counter. DETAILED DESCRIPTION

[0044] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0045] It should be understood that the terms used in the text are only for the purpose of describing specific example embodiments, and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used in the text may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0046] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0047] For ease of description, spatial relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figure, such as "inside", "outside", "inner side", "outer side", "below", "below", "above", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is turned over, then the elements described as "below other elements or features" or "below other elements or features" will subsequently be oriented as "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include both upper and lower orientations. The device can be oriented otherwise (rotated 90 degrees or in other directions) and the spatial relative descriptors used in the text are interpreted accordingly.

[0048] See also Figure 1The present embodiment provides a diesel engine nitrogen oxide reducing agent PN emission characteristic test system, comprising a burner 100, a filter 200, a mixing tube 300, an SCR catalyst 400 and an ASC catalyst 500 connected in sequence; the burner 100 is used to pass fuel, and the fuel can undergo a combustion reaction in the burner 100; the filter 200 is used to filter upstream particulate matter generated by the combustion reaction; the mixing tube 300 is used to pass nitrogen oxide reducing agent and simulated gas components, and is used to mix the filtered combustion products, nitrogen oxide reducing agent and simulated gas components to form a mixed gas; the SCR catalyst 400 is used to promote the catalytic reduction reaction of the mixed gas; the ASC catalyst 500 is used to undergo an ammonia oxidation reaction; the outlet of the ASC catalyst 500 is provided with a downstream particle counter 50 for measuring the concentration of downstream particulate matter.

[0049] The diesel engine nitrogen oxide reducing agent PN emission characteristic test system obtains a high-temperature airflow by burning fuel and combustion aid in the burner 100, simulating the exhaust flow and exhaust temperature of the engine in the actual working condition. The upstream particulate matter generated by the combustion is filtered through the filter 200, so as to exclude the upstream particulate matter contained in the product of the catalytic reduction reaction as much as possible. The gas components required for the reaction in the actual working condition, including the nitrogen oxide reducing agent and the simulated gas component, are introduced into the mixing tube 300. After the combustion products, the nitrogen oxide reducing agent and the simulated gas component are mixed in the mixing tube 300, they enter the SCR catalyst 400 for catalytic reduction reaction, and an ammonia oxidation reaction occurs in the ASC catalyst 500. The particulate emission level of the nitrogen oxide reducing agent is judged according to the concentration of particulate matter eliminated after the reaction is stable. By replacing the nitrogen oxide reducing agent, the particulate emission levels of different types of nitrogen oxide reducing agents can be compared, and it can also be used to monitor the particulate emission levels of commercially available diesel engine nitrogen oxide reducing agents, thereby eliminating nitrogen oxide reducing agents with excessively high particulate emission levels, and screening out nitrogen oxide reducing agents with low particulate emission levels for promotion and use.

[0050] Since the generation of upstream particulate matter is unrelated to the use of nitrogen oxide reducing agent, it is necessary to avoid mixing upstream particulate matter in downstream particulate matter to avoid the influence of upstream particulate matter on the measurement results. Therefore, on the one hand, the fuel selection can be a fuel that can be fully burned and has a relatively small amount of particulate matter generated during the combustion process. For example, the fuel can be methane or alcohol. Optionally, the combustion aid can be air; on the other hand, the filter 200 is used to filter the upstream particulate matter. Although alcohol-based fuels have higher environmental benefits than traditional petroleum fuels, when methane or alcohols are burned, in addition to producing gases such as carbon dioxide, carbon monoxide, and nitrogen oxides, a small amount of particulate matter will still be produced. The setting of the filter can filter out the particulate matter generated during combustion as much as possible, and prevent the particulate matter generated by combustion from entering the SCR catalyst. Optionally, the filter can be a diesel particulate filter or other filter that can filter upstream particulate matter.

[0051] Optionally, the combustion products are filtered and then enter the mixing tube 300, and the nitrogen oxide reducing agent and the simulated gas components are introduced through the front side of the mixing tube 300. The filtered combustion products, the nitrogen oxide reducing agent and the simulated gas components are fully mixed and uniformly formed in the mixing tube 300 to form a mixed gas so as to be transported to the SCR catalyst 400 for reaction. Optionally, a nitrogen oxide reducing agent injection device for injecting nitrogen oxide reducing agent into the pipeline is connected between the filter 200 and the mixing tube 300. The nitrogen oxide reducing agent injection device includes a liquid storage tank, a pump, a nozzle and an injection control unit. The pump is responsible for extracting the nitrogen oxide reducing agent from the liquid storage tank and injecting it into the pipeline through the nozzle. The injection control unit controls the operation of the pump according to the preset injection amount. The simulated gas components include nitrogen oxides, oxygen, water and carbon dioxide, etc. The types and proportions of the gases in the simulated gas components are determined according to the gas components in the SCR catalyst 400 in the actual working conditions.

[0052] Furthermore, the ASC catalyst 500 is connected to an exhaust gas treatment device 600, which is used to purify the exhaust gas. The exhaust gas treatment device 600 purifies the exhaust gas generated during the test to prevent the exhaust gas from being discharged into the air and causing environmental pollution.

[0053] Optionally, the diesel engine nitrogen oxide reducing agent PN emission characteristic test system also includes a controller, which is used to receive signals from the detection device and issue control instructions according to preset instructions. The method of receiving signals and sending instructions by the controller is a conventional technology in the field and will not be described in detail here.

[0054] Further, a temperature detection unit 30 is provided between the mixing tube 300 and the SCR catalyst 400, and the temperature detection unit 30 is used to measure the exhaust temperature of the mixed gas. The temperature in the SCR catalyst 400 is provided by the combustion reaction in the burner 100, and the exhaust temperature value is determined according to the exhaust temperature in the SCR catalyst 400 in the actual working condition. It can be understood that the amount of fuel is directly related to the heat released during the combustion process, thereby affecting the temperature. When the exhaust temperature is lower than the preset exhaust temperature, the amount of fuel and fuel agent used is increased, and when the exhaust temperature is higher than the preset exhaust temperature, the amount of fuel and fuel agent used is reduced. Optionally, the temperature detection unit 30 can be a temperature sensor, and the temperature sensor detects the exhaust temperature in the pipeline in real time. And the temperature signal is converted into an electrical signal and transmitted to the controller, the controller receives the electrical signal of the sensor, and converts it into an actual temperature value, and the controller controls the delivery amount of fuel and fuel agent according to the preset exhaust temperature. Optionally, temperature regulating valves may be provided on the fuel and fuel agent delivery pipelines, respectively, and the controller may control the opening of the solenoid valve according to the deviation between the measurement structure of the temperature sensor and the preset exhaust temperature, thereby controlling the delivery amount of the fuel and fuel agent to achieve the purpose of adjusting the exhaust temperature. Optionally, the temperature regulating valve may be a solenoid valve.

[0055] Further, a flow detection unit 10 is provided between the filter 200 and the SCR catalyst 400, and the flow detection unit 10 is used to measure the flow of the gas discharged from the filter 200. The exhaust flow is provided by the combustion reaction in the burner 100, and the exhaust flow value is determined according to the exhaust flow in the SCR catalyst 400 in the actual working condition. Optionally, the flow detection unit 10 can be a gas flow meter, such as a volume flow meter, a mass flow meter and a differential pressure flow meter. Optionally, a flow regulating valve can be provided between the gas flow meter and the burner 100. The gas flow meter detects the exhaust flow in real time and transmits the measurement result to the controller. The controller controls the opening of the flow regulating valve according to the preset exhaust flow. When the exhaust flow is less than the preset exhaust flow, the opening of the flow regulating valve is increased, and when the exhaust flow is greater than the preset exhaust flow, the opening of the flow regulating valve is reduced. Optionally, the flow regulating valve can be a solenoid valve.

[0056] Furthermore, an upstream particle counter 20 is provided between the filter 200 and the SCR catalyst 400, and the upstream particle counter 20 is used to measure the concentration of upstream particulate matter. The purification effect of the filter 200 on the upstream particulate matter is confirmed according to the concentration of the upstream particulate matter. The upstream particulate matter concentration PN1 is lower than the upstream particulate matter concentration limit PN0, which reduces the amount of upstream particulate matter mixed in the downstream particulate matter, and ensures the accuracy of the measurement result.

[0057] Furthermore, a gas analyzer 40 is provided at the outlet of the ASC catalyst 500, and the gas analyzer 40 is used to measure the gas composition discharged from the ASC catalyst 500, so as to confirm the purification effect of nitrogen oxides. The gas analyzer 40 is a process analysis instrument for measuring gas composition, and a gas sensor is provided in the gas analyzer 40, and the gas sensor is a sensor for detecting the composition and content of the gas. For example, the gas analyzer 40 can be a thermal conductivity gas analyzer, an electrochemical gas analyzer, or an infrared absorption analyzer.

[0058] Further, see Figure 1 and Figure 2 The present embodiment further provides a diesel engine nitrogen oxide reducing agent PN emission characteristic test method. Based on the diesel engine nitrogen oxide reducing agent PN emission characteristic test system, the diesel engine nitrogen oxide reducing agent PN emission characteristic test method comprises the following steps:

[0059] S100, obtaining the preset flow value of the gas discharged from the filter 200, the preset exhaust temperature value of the mixed gas and the preset concentration value of each gas component after the ammonia oxidation reaction, determining the upstream particulate matter concentration limit PN0, determining the amount of fuel, the amount of simulated gas components and the injection amount of nitrogen oxide reducing agent.

[0060] This method should restore the particle emission characteristics under a typical working condition or several typical working conditions in the actual operation of the engine as much as possible. The particle emission characteristics that need to be determined in the test include original engine emission (upstream of the after-treatment system) and tail pipe emission (downstream of the after-treatment system), and its key parameters include exhaust flow, exhaust temperature, concentration of various substances in the exhaust (generally including oxygen, water, nitrogen oxides, etc.) and injection amount of nitrogen oxide reducing agent. It can be understood that the key parameters of the engine under different working conditions are different, and the required amount of fuel, the amount of simulated gas components and the injection amount of nitrogen oxide reducing agent are different. Accordingly, the same nitrogen oxide reducing agent can be tested under different working conditions, so as to obtain rich measurement data and ensure the accuracy of the test results. The preset exhaust flow value, the preset exhaust temperature value, the preset concentration value of each gas component, the amount of fuel, the amount of simulated gas components and the injection amount of nitrogen oxide reducing agent can be obtained in advance through engine or vehicle emission tests. The engine emission test can test the automobile engine in a special test room, and the test methods mainly include bench method and rotor method. The bench method is to fix the car on the test bench and simulate different driving conditions by controlling the engine load and speed to test the engine performance and emissions. The rotor method is to dismantle the engine and install it on the rotor test bench for testing. The vehicle emission test is to test the car under actual road conditions. The test methods mainly include route testing and block testing. The route test is to evaluate the engine performance and emissions by testing the vehicle speed, rotation speed, fuel consumption, etc. under different road conditions. The block test is to simulate real driving conditions by testing in urban blocks to evaluate the performance and emissions of the car engine in actual use.

[0061] S200. Without injecting nitrogen oxide reducing agent, operate the diesel engine nitrogen oxide reducing agent PN emission characteristic test system, make the flow value of the gas discharged from the filter 200 equal to the preset exhaust flow value, make the exhaust temperature value of the mixed gas equal to the preset exhaust temperature value, and confirm that the upstream particulate matter concentration value PN1 is less than the upstream particulate matter concentration limit value PN0.

[0062] The purpose of S200 is to run the system and reproduce the corresponding parameters according to the parameters obtained in S100 to ensure that the system can operate normally and simulate the actual working conditions of the engine aftertreatment. Figure 1, the exhaust temperature and exhaust flow are obtained through the combustion products of the burner 100, and the nitrogen oxide reducing agent and the simulated gas components are introduced through the front side of the mixing tube 300. The exhaust flow value is measured by the flow detection unit 10, and the exhaust temperature value is measured by the temperature detection unit 30. It should be confirmed that the upstream particulate matter concentration PN1 is less than the upstream particulate matter concentration limit PN0, so as to avoid the interference of the upstream particulate matter on the nitrogen oxide reducing agent particulate matter emission level test. In addition, the concentration of each gas component downstream of the ASC catalyst 500 is measured by the gas analyzer 40. Since the nitrogen oxide reducing agent has not been injected, nitrogen oxides and the like will not react in the SCR catalyst 400 and the ASC catalyst 500. At this time, it should be confirmed whether the concentration of each gas component measured by the gas analyzer 40 is consistent with the amount of the simulated gas component introduced. If the results are consistent, it means that the gas analyzer 40 is operating normally and the next step can be continued; if they are inconsistent, it means that there is a problem with the measurement of the gas analyzer 40 and it should be replaced or repaired.

[0063] S300: Inject nitrogen oxide reducing agent.

[0064] After confirming that all system parameters are normal, the nitrogen oxide reducing agent can be injected. The nitrogen oxide reducing agent here can be various types of automotive urea, ammonia, etc. The nitrogen oxide reducing agent injection device should be as consistent as possible with the nitrogen oxide reducing agent injection device used in the engine in S100. The injection amount of the nitrogen oxide reducing agent should maintain an equal ammonia-nitrogen ratio with the injection amount of the nitrogen oxide reducing agent used in the emission test in S100. It should be noted that the nitrogen oxide reducing agent generates ammonia after thermal decomposition, and the ammonia-nitrogen ratio is the molar ratio of ammonia to nitrogen oxides. If the type of nitrogen oxide reducing agent being tested is different from the type of nitrogen oxide reducing agent used in the emission test in S100, the specific injection amount required under the equal ammonia-nitrogen ratio should be converted by molecular formula and concentration.

[0065] S400, confirming that the concentration value of each gas component after the ammonia oxidation reaction is the same as the preset concentration value of each gas component.

[0066] After the nitrogen oxide reducing agent is injected, the system simulates the state of the engine aftertreatment system when it is working normally, so it should be confirmed that the measurement results of the gas analyzer 40 are consistent with the exhaust emission results downstream of the engine aftertreatment system. The measurement results need to focus on the concentrations of nitrogen oxides and ammonia, because these two gases are concerned by emission regulations. In the emission control of the engine, the emission levels of these two substances need to be controlled below the limits required by the regulations.

[0067] S500 , recording the upstream particle concentration value PN1 and the downstream particle concentration value PN2 and performing data processing.

[0068] It should be noted that when the operating conditions are switched but the nitrogen oxide reducing agent has not yet been injected, the upstream particulate matter concentration value PN1 will have obvious fluctuations. When the exhaust temperature, the flow rate of the gas discharged from the filter 200, the concentration of each gas component, etc. are almost stable, the value of the upstream particulate matter concentration value PN1 will generally stabilize. When the reducing agent begins to be injected, the downstream particulate matter concentration value PN2 will suddenly increase and fluctuate for a period of time. When recording the upstream particulate matter concentration value PN1 and the downstream particulate matter concentration value PN2, the recording should be made when the upstream particulate matter concentration value PN1 and the downstream particulate matter concentration value PN2 no longer fluctuate significantly to avoid errors caused by inaccurate counting. Optionally, the upstream particulate matter concentration value PN1 is measured by the upstream particle counter 20, and the downstream particulate matter concentration value PN2 is measured by the downstream particle counter 50.

[0069] To avoid the influence of upstream particulate matter on the measurement results, the PN1 and PN2 values ​​in each test can be used to compare the extent to which different reducing agents cause increased PN emissions under the same operating conditions.

[0070] In one embodiment, in S500, data processing includes calculating the absolute value deviation Σ of the particle emission quantity:

[0071] Σ=PN2-PN1.

[0072] Since PN1 is affected by the filtering capacity of the filter 200, the absolute value deviation Σ of the particulate matter emission quantity suitable for each nitrogen oxide reducing agent is (PN2-PN1) rather than the ratio (1-PN2 / PN1).

[0073] In another embodiment, in S500, the data processing includes calculating the absolute value deviation Σ of the particle emission quantity:

[0074] Σ=[(PN2-PN1)-(PN2a-PN1a)] or Σ=[1-(PN2-PN1) / (PN2a-PN1a)];

[0075] Wherein, PN1a is the upstream particulate matter concentration value of the reference nitrogen oxide reducing agent a, and PN2a is the downstream particulate matter concentration value of the reference nitrogen oxide reducing agent a. The reference reducing agent a can be a urea aqueous solution with a known low particulate matter emission amount, or ammonia with a theoretically low particulate matter emission amount.

[0076] When it is necessary to test or compare a variety of nitrogen oxide reducing agents, S200 to S500 can be repeated, and the absolute value deviation Σ of the particulate matter emission quantity obtained by using different types of nitrogen oxide reducing agents can be compared to draw a conclusion.

[0077] The above-mentioned diesel engine nitrogen oxide reductant PN emission characteristic test method simulates the flow, temperature and gas phase composition characteristics of engine exhaust emissions through a specially constructed diesel engine nitrogen oxide reductant PN emission characteristic test system. During the test, the influence of particulate matter emissions in combustion products on the particulate matter emission characteristic test in catalytic reduction products is effectively eliminated, thereby being able to rigorously and reliably evaluate the particulate matter emission effects of various nitrogen oxide reductants.

[0078] Furthermore, the diesel engine nitrogen oxide reducing agent PN emission characteristic test method also includes:

[0079] S600, replace the nitrogen oxide reducing agent, and repeat S200 to S500;

[0080] S700: Compare the results after data processing.

[0081] S600 and S700 can be used to test the particulate matter emission levels of different nitrogen oxide reducing agents, thereby eliminating nitrogen oxide reducing agents with excessively high particulate matter emission levels and screening out nitrogen oxide reducing agents with lower particulate matter emission levels for promotion and use.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A diesel engine nitrogen oxide reducing agent PN emission characteristic test system, characterized in that: It comprises a burner (100), a filter (200), a mixing tube (300), an SCR catalyst (400) and an ASC catalyst (500) which are connected in sequence; The burner (100) is used to introduce fuel, and the fuel can undergo a combustion reaction in the burner (100); The filter (200) is used to filter upstream particulate matter generated by the combustion reaction; The mixing tube (300) is used to introduce a nitrogen oxide reducing agent and a simulated gas component, and to mix the filtered combustion product, the nitrogen oxide reducing agent and the simulated gas component to form a mixed gas; The SCR catalyst (400) is used to promote the catalytic reduction reaction of the mixed gas; The ASC catalyst (500) is used to generate an ammonia oxidation reaction; The outlet of the ASC catalyst (500) is provided with a downstream particle counter (50) for measuring the concentration of downstream particulate matter.

2. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to claim 1 is characterized in that: The ASC catalyst (500) is connected to an exhaust gas treatment device (600), and the exhaust gas treatment device (600) is used to purify exhaust gas.

3. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to claim 2 is characterized in that: A temperature detection unit (30) is provided between the mixing tube (300) and the SCR catalyst (400), and the temperature detection unit (30) is used to measure the exhaust temperature of the mixed gas.

4. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to claim 1, characterized in that: A flow detection unit (10) is provided between the filter (200) and the SCR catalyst (400), and the flow detection unit (10) is used to measure the flow of gas discharged from the filter (200).

5. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to claim 1, characterized in that: An upstream particle counter (20) is arranged between the filter (200) and the SCR catalyst (400), and the upstream particle counter (20) is used to measure the concentration of upstream particulate matter.

6. The diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to claim 1, characterized in that: A gas analyzer (40) is provided at the outlet of the ASC catalyst (500), and the gas analyzer (40) is used to measure the components of the gas discharged from the ASC catalyst (500).

7. A diesel engine nitrogen oxide reducing agent PN emission characteristic test method, characterized in that: Based on the diesel engine nitrogen oxide reducing agent PN emission characteristic test system according to any one of claims 1 to 6, the diesel engine nitrogen oxide reducing agent PN emission characteristic test method comprises the following steps: S100, obtaining a preset flow value of the gas discharged from the filter (200), a preset exhaust temperature value of the mixed gas, and a preset concentration value of each gas component after the ammonia oxidation reaction, determining an upstream particulate matter concentration limit PN0, and determining an amount of the fuel, an amount of the simulated gas component, and an injection amount of the nitrogen oxide reducing agent; S200, operating the diesel engine nitrogen oxide reducing agent PN emission characteristic test system without injecting the nitrogen oxide reducing agent, making the flow value of the gas discharged from the filter (200) equal to the preset exhaust flow value, making the exhaust temperature value of the mixed gas equal to the preset exhaust temperature value, and confirming that the upstream particulate matter concentration value PN1 is less than the upstream particulate matter concentration limit value PN0; S300, injecting the nitrogen oxide reducing agent; S400, confirming that the concentration value of each gas component after the ammonia oxidation reaction is the same as the preset concentration value of each gas component; S500 , recording the upstream particle concentration value PN1 and the downstream particle concentration value PN2 and performing data processing.

8. The diesel engine nitrogen oxide reducing agent PN emission characteristic test method according to claim 7, characterized in that: In S500, the data processing includes calculating the absolute value deviation Σ of the particle emission quantity: Σ=PN2-PN1.

9. The diesel engine nitrogen oxide reducing agent PN emission characteristic test method according to claim 7, characterized in that: In S500, the data processing includes calculating the absolute value deviation Σ of the particle emission quantity: Σ=[(PN2-PN1)-(PN2a-PN1a)] or Σ=[1-(PN2-PN1) / (PN2a-PN1a)]; Wherein, PN1a is the upstream particulate matter concentration value of the reference nitrogen oxide reducing agent a, and PN2a is the downstream particulate matter concentration value of the reference nitrogen oxide reducing agent a.

10. The diesel engine nitrogen oxide reducing agent PN emission characteristic test method according to claim 7, characterized in that: Also includes: S600, replacing the nitrogen oxide reducing agent, and repeating S200 to S500; S700: Compare the results after data processing.

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