Verification method of engine exhaust pollution conversion efficiency by DOC and engine bench

Abstract

The application discloses a DOC engine exhaust pollution conversion efficiency verification method and an engine bench, and belongs to the technical field of engines. The DOC engine exhaust pollution conversion efficiency verification method and the engine bench refer to two main factors affecting the DOC efficiency, i.e. the bed temperature of the DOC and the volume flow of the exhaust gas entering the DOC, so that the DOC efficiency verification precision is higher and more comprehensive; not only the conversion efficiency of the DOC on THC can be verified, but also the conversion efficiency of the DOC on CO and NO can be verified, the performance verification of the DOC is more comprehensive, and the DOC selection and bench fine calibration process can be used.

Description

Verification method for DOC conversion efficiency of engine exhaust pollutants and engine bench Technical Field

[0001] This invention relates to the field of engine technology, and in particular to a method for verifying the conversion efficiency of engine exhaust pollutants using DOC and an engine test bench. Background Technology

[0002] The main exhaust pollutants from China VI diesel engines include nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (THC), and particulate matter (PM).

[0003] The aftertreatment system of China VI diesel engines includes aftertreatment units such as catalytic oxidation unit (DOC), particulate filter (DPF), oxidation-reduction catalyst (SCR), and ammonia escape catalyst (ASC).

[0004] To meet emission regulations, China VI diesel engines use DOC (Diesel Oxide) for the following purposes:

[0005] 1. Effectively reduces the concentration of THC and CO;

[0006] 2. Increase exhaust gas temperature to improve SCR conversion efficiency;

[0007] 3. It can oxidize NO to NO2, which can effectively improve the passive regeneration capability of DPF;

[0008] 4. When the carbon carrying capacity of the DPF collector reaches its limit, the DPF can be actively regenerated by heating with DOC, meaning that the carbon accumulated in the DPF can be completely burned under the action of DOC.

[0009] When selecting a diesel engine, it is necessary to test the conversion efficiency of DOC (Diesel Oxide Concentrate) for diesel engine exhaust pollutants to predict whether the DOC meets the emission requirements or other related functional requirements of a particular engine model. However, existing methods for verifying the conversion efficiency of DOC for engine exhaust pollutants are not only inaccurate but also cannot verify the impact of DOC on the conversion efficiency of NO. Summary of the Invention

[0010] The purpose of this invention is to provide a method and engine test bench for verifying the conversion efficiency of DOC on engine exhaust pollutants, which is not only highly accurate, but also able to verify the effect of DOC on the conversion efficiency of NO.

[0011] To achieve the above objectives, the following technical solution is provided:

[0012] On the one hand, a method for verifying the conversion efficiency of engine exhaust pollutants using DOC is provided, including the following steps:

[0013] S1. Start the engine and pass the engine exhaust into the DOC;

[0014] S2. Set the bed temperature T of the DOC to a preset bed temperature, and set the volumetric flow rate V of the exhaust gas introduced into the DOC to a preset volumetric flow rate;

[0015] S3. Perform a far-rear injection test on the engine with a preset fuel injection quantity MF, and gradually increase the value of MF from zero until the exhaust temperature at the DOC outlet reaches the preset temperature or the THC concentration at the DOC outlet exceeds the preset concentration.

[0016] S4. For each value of MF, obtain the corresponding mass flow rate ME of the exhaust gas introduced into the DOC, the exhaust temperature T1 at the DOC inlet and the exhaust temperature T2 at the DOC outlet, the THC concentration EH1 at the DOC inlet and the THC concentration EH2 at the DOC outlet, the CO concentration EC11 and CO2 concentration EC12 at the DOC inlet, the CO2 concentration EC22 at the DOC outlet, the NO concentration EN11 and NO2 concentration EN12 at the DOC inlet, and the NO2 concentration EN22 at the DOC outlet.

[0017] S5. For each value of MF, calculate the corresponding conversion efficiency η of the DOC and the conversion efficiency η of the DOC to THC. H The conversion efficiency η of DOC to CO C and the conversion efficiency η of DOC to NO N , Where Cp is the exhaust specific heat; HV is the fuel calorific value;

[0018] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, step S2 includes the following steps:

[0019] S21. Adjust the operating conditions of the engine;

[0020] S22. Real-time acquisition of the exhaust temperature T3 at the DOC inlet and the exhaust temperature T4 at the DOC outlet;

[0021] S23. Calculate the bed temperature T of the DOC and the volumetric flow rate V of the exhaust gas introduced into the DOC until T equals the preset bed temperature and V equals the preset volumetric flow rate, where T = 20%T3 + 80%T4. Where m is the exhaust mass flow rate of the engine; R is the gas constant; and P is the exhaust pressure of the engine.

[0022] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, the following steps are also included after step S5:

[0023] S6. Change the value of the preset bed temperature and the value of the preset volumetric flow rate, and repeat steps S3-S5.

[0024] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, the following steps are also included after step S6:

[0025] Different preset bed temperatures and preset volumetric flow rates are prepared with respect to η and / or η. H And / or the η N A chart showing the correspondence between them.

[0026] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, in step S1, both the engine and the DOC are mounted on an engine test bench.

[0027] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, in step S3, the preset temperature is 600°C.

[0028] In step S3, the preset concentration is 2000 ppm.

[0029] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, step S4 further includes the following steps:

[0030] When the DOC is located in the post-processor assembly, and the post-processor also includes a preset post-processing unit, the preset post-processing unit is replaced with an empty bucket.

[0031] The concentration of THC at the outlet of the after-processor assembly is obtained, and the obtained concentration of THC at the outlet of the after-processor assembly is the EH2.

[0032] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, step S4 further includes the following steps:

[0033] If the intake air flow rate of the engine is obtained, then ME is equal to the sum of the obtained intake air flow rate of the engine and the corresponding MF.

[0034] As an optional method for verifying the conversion efficiency of engine exhaust pollutants using DOC, step S3 further includes the following steps:

[0035] If the fuel consumption of the engine is obtained, the obtained fuel consumption is the preset fuel injection quantity, and the accuracy of the obtained fuel consumption is not less than 0.01 kg / h.

[0036] On the other hand, an engine bench is provided for implementing the verification method of DOC for engine exhaust pollutant conversion efficiency as described in any of the preceding claims.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The present invention provides a method and engine test bench for verifying the conversion efficiency of DOC for engine exhaust pollutants. It takes into account two main factors affecting DOC efficiency: the bed temperature of the DOC and the volumetric flow rate of the exhaust gas introduced into the DOC, making the DOC efficiency verification more accurate and comprehensive. It can not only verify the conversion efficiency of DOC for THC, but also the conversion efficiency of DOC for CO and NO, making the performance verification of DOC more comprehensive. It can be used for DOC selection and fine test bench calibration. Attached Figure Description

[0039] Figure 1 is a flowchart of the method for verifying the conversion efficiency of engine exhaust pollutants by DOC in an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0043] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0047] As shown in Figure 1, this embodiment provides a method for verifying the conversion efficiency of engine exhaust pollutants using DOC, including the following steps:

[0048] S1. Start the engine and let the engine exhaust flow into the DOC.

[0049] In this embodiment, both the engine and the DOC are mounted on an engine test bench, which allows for the use of an existing test bench to verify the conversion efficiency of the DOC for engine exhaust pollutants, thus saving costs.

[0050] S2. Set the bed temperature T of the DOC to the preset bed temperature, and set the volumetric flow rate V of the exhaust gas introduced into the DOC to the preset volumetric flow rate.

[0051] It should be noted that the two main factors affecting DOC efficiency are the bed temperature of the DOC and the volumetric flow rate of the exhaust gas introduced into the DOC. In this embodiment, the bed temperature T of the DOC is first set to a preset bed temperature, and the volumetric flow rate V of the exhaust gas introduced into the DOC is set to a preset volumetric flow rate. Then, the DOC efficiency is verified. Compared with the prior art, the verification accuracy is higher and the reference value is greater.

[0052] Since the bed temperature and volumetric flow rate of the exhaust gas entering the DOC mainly depend on the engine speed and torque, when determining the preset bed temperature and preset volumetric flow rate, it is necessary to consider the engine's common operating conditions, but not be limited to a certain engine speed and a certain actual load. It is only necessary to cover the engine's common speed and torque, so as to accurately verify whether the DOC meets the engine's emission requirements or other related functional requirements.

[0053] Therefore, in step S2, it is necessary to first select the common operating conditions of the engine. For example, the common operating conditions include multiple different preset operating conditions. When the engine is under different preset operating conditions, the engine speed and torque are different. When the engine is under a certain preset operating condition, the bed temperature T of the DOC is the preset bed temperature, and the volumetric flow rate V of the exhaust gas entering the DOC is the preset volumetric flow rate. Then, the engine operating conditions are adjusted to the preset operating conditions.

[0054] Optionally, step S2 includes the following steps:

[0055] S21, Adjust the engine operating conditions;

[0056] S22. Real-time acquisition of exhaust temperature T3 at the DOC inlet and exhaust temperature T4 at the DOC outlet;

[0057] By installing temperature sensors or other temperature detection devices at the DOC inlet and DOC outlet respectively, the exhaust temperature T3 at the DOC inlet and the exhaust temperature T4 at the DOC outlet can be obtained.

[0058] S23. Calculate the bed temperature T of the DOC and the volumetric flow rate V of the exhaust gas introduced into the DOC until T equals the preset bed temperature and V equals the preset volumetric flow rate, T = 20%T3 + 80%T4. Where m is the exhaust mass flow rate of the engine; R is the gas constant; and P is the exhaust pressure of the engine. The exhaust pressure P of the engine can be directly measured by pressure detection devices such as pressure sensors installed in the engine exhaust pipeline (such as the engine exhaust port, DOC inlet or DOC outlet).

[0059] S3. Perform a long-range injection test on the engine with a preset fuel injection quantity MF, and gradually increase the value of MF from zero until the exhaust temperature at the DOC outlet reaches the preset temperature or the THC concentration at the DOC outlet exceeds the preset concentration. For example, the preset temperature is 600°C and the preset concentration is 2000 ppm.

[0060] For example, in step S3, the initial preset fuel injection quantity MF of the engine is 0 kg / h, and then the preset fuel injection quantity MF is adjusted sequentially to 0.1 kg / h, 0.2 kg / h, 0.3 kg / h, etc. In other words, in this embodiment, the value of the preset fuel injection quantity MF increases gradually from zero, and the difference between two adjacent MF levels is 0.1. Of course, in other embodiments, other values ​​such as 0.2 can be set for the difference between two adjacent MF levels, which is not limited here.

[0061] For example, by installing a temperature sensor or other temperature detection device at the DOC outlet, the exhaust temperature at the DOC outlet can be obtained. By installing an emission meter or other THC concentration detection device at the DOC outlet, the THC concentration at the DOC outlet can be obtained.

[0062] It should be noted that, under the premise of S2, the engine is controlled to perform remote and rear injection tests with different preset fuel injection quantities in order to scan the efficiency of DOC, and thus the conversion efficiency of DOC corresponding to different fuel injection quantities can be accurately calculated.

[0063] Optionally, the engine's fuel consumption is obtained, and the obtained fuel consumption is the preset fuel injection quantity, with an accuracy of not less than 0.01 kg / h. For example, a fuel consumption meter can be installed on an engine test bench, with the meter's detection accuracy not less than 0.01 kg / h, to detect the engine's fuel consumption and use the measured fuel consumption as the preset fuel injection quantity, resulting in higher accuracy.

[0064] S4. For each value of MF, obtain the corresponding mass flow rate ME of the exhaust gas entering the DOC, the exhaust temperature T1 at the DOC inlet and the exhaust temperature T2 at the DOC outlet, the THC concentration EH1 at the DOC inlet and the THC concentration EH2 at the DOC outlet, the CO concentration EC11 and CO2 concentration EC12 at the DOC inlet, the CO2 concentration EC22 at the DOC outlet, the NO concentration EN11 and NO2 concentration EN12 at the DOC inlet, and the NO2 concentration EN22 at the DOC outlet.

[0065] For example, by setting temperature sensors or other temperature detection devices at the DOC inlet and DOC outlet respectively, the exhaust temperature at the DOC inlet and the exhaust temperature at the DOC outlet can be obtained in real time. Then, for each value of MF, the exhaust temperature T1 at the DOC inlet and the exhaust temperature T2 at the DOC outlet can be recorded respectively.

[0066] Furthermore, by installing exhaust pollutant concentration detectors such as emission meters at the DOC inlet and DOC outlet, the concentrations of THC, CO, and CO2 at the DOC inlet and outlet, respectively, can be obtained in real time. Then, for each value of MF, the concentrations of THC at the DOC inlet (EH1) and outlet (EH2), CO, CO2, and NO at the DOC outlet (EC11 and EC12), and NO2, EN11, EN12, and EN22 at the DOC outlet can be recorded.

[0067] Optionally, since the mass flow rate ME of the exhaust gas entering the DOC is equal to the sum of the engine's intake flow rate and the corresponding MF, the engine's intake flow rate can be detected in real time by installing a gas flow meter or other flow detection device at the engine inlet, and then the mass flow rate ME of the exhaust gas entering the DOC can be calculated.

[0068] If there is no location for THC concentration detection after the DOC, the THC concentration detector can be placed at the outlet of the after-processor assembly. Since the after-processor assembly includes not only the DOC but also other preset after-processing units such as DPF, SCR, and ASC, in order to prevent these other preset after-processing units from oxidizing THC, the DPF, SCR, ASC, and other preset after-processing units need to be replaced with empty containers. The THC concentration measured at the outlet of the after-processor assembly is then used as the aforementioned EH2.

[0069] S5. For each value of MF, calculate the corresponding conversion efficiency η of DOC and the conversion efficiency η of DOC to THC. H The conversion efficiency η of DOC to CO C The conversion efficiency η of DOC to NO N ,but Where Cp is the exhaust specific heat; in this embodiment, Cp equals 1.15 kJ / (kg*K); HV is the fuel calorific value; in this embodiment, HV equals 42600 kJ / kg.

[0070] In this embodiment, all temperatures are expressed in °C; all concentrations are expressed in PPM; exhaust mass flow rate is expressed in kg / h; and fuel consumption is expressed in kg / h.

[0071] S6. Change the preset bed temperature and preset volumetric flow rate, and repeat steps S3-S5.

[0072] It should be noted that changing the preset bed temperature and preset volumetric flow rate means changing the engine's operating conditions, so that the engine can be subjected to different operating conditions to fully verify the DOC efficiency.

[0073] Optionally, after step S6, the following steps are also included:

[0074] Create different preset bed temperatures and preset volumetric flow rates with η and / or η H and / or η N A chart showing the correspondence between them.

[0075] The method for verifying the conversion efficiency of DOC for engine exhaust pollutants in this embodiment is applicable to engine bench testing. It takes into account two main factors affecting DOC efficiency: the bed temperature of the DOC and the volumetric flow rate of the exhaust gas introduced into the DOC, making the DOC efficiency verification more accurate and comprehensive. It can not only verify the conversion efficiency of DOC for THC, but also the conversion efficiency of DOC for CO and NO, making the performance verification of DOC more comprehensive. It can be used for DOC selection and fine bench calibration.

[0076] This embodiment also provides an engine test bench for implementing the DOC verification method for engine exhaust pollutant conversion efficiency as described above. The engine test bench of this embodiment, by employing the aforementioned DOC verification method for engine exhaust pollutant conversion efficiency, has the same beneficial effects as the aforementioned method, and will not be elaborated further here.

[0077] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for verifying the conversion efficiency of engine exhaust pollutants using DOC, characterized in that, The process includes the following steps: S1. Start the engine and introduce the engine exhaust into the DOC; S2. Set the bed temperature T of the DOC to a preset bed temperature and the volumetric flow rate V of the exhaust into the DOC to a preset volumetric flow rate; S3. Perform a far-to-back injection test on the engine with a preset injection quantity MF, and gradually increase the value of MF from zero until the exhaust temperature at the DOC outlet reaches a preset temperature or the THC concentration at the DOC outlet exceeds a preset concentration; S4. For each value of MF, obtain the corresponding mass flow rate ME of the exhaust into the DOC and the mass flow rate V of the exhaust into the DOC. S5. For each value of MF, calculate the corresponding conversion efficiency η of the DOC and the conversion efficiency of the DOC to THC. The conversion efficiency of DOC to CO and the conversion efficiency of the DOC to NO ， Where Cp is the exhaust specific heat; HV is the fuel calorific value; ； ； Step S2 includes the following steps: S21, adjusting the engine's operating conditions; S22, acquiring the exhaust temperature T3 at the DOC inlet and the exhaust temperature T4 at the DOC outlet in real time; S23, calculating the bed temperature T of the DOC and the volumetric flow rate V of the exhaust gas introduced into the DOC, until T equals the preset bed temperature and V equals the preset volumetric flow rate. ， Where m is the exhaust mass flow rate of the engine; R is the gas constant; and P is the exhaust pressure of the engine.

2. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, After step S5, the following steps are also included: S6, changing the value of the preset bed temperature and the value of the preset volumetric flow rate, and repeating steps S3-S5.

3. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 2, characterized in that, Following step S6, the following steps are also included: preparing different preset bed temperatures and preset volumetric flow rates with respect to η and / or the and / or the aforementioned A chart showing the correspondence between them.

4. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, In step S1, both the engine and the DOC are mounted on an engine stand.

5. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, In step S3, the preset temperature is 600°C; in step S3, the preset concentration is 2000 ppm.

6. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, In step S4, the following steps are also included: when the DOC is located in the post-processor assembly and the post-processor also includes a preset post-processing unit, the preset post-processing unit is replaced with an empty barrel; the concentration of THC at the outlet of the post-processor assembly is obtained, and the obtained concentration of THC at the outlet of the post-processor assembly is the EH2.

7. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, In step S4, the following step is also included: obtaining the intake air flow rate of the engine, then ME is equal to the sum of the obtained intake air flow rate of the engine and the corresponding MF.

8. The method for verifying the conversion efficiency of engine exhaust pollutants using DOC according to claim 1, characterized in that, In step S3, the following steps are also included: obtaining the fuel consumption of the engine, wherein the obtained fuel consumption is the preset fuel injection quantity, and the accuracy of the obtained fuel consumption is not less than 0.01 kg / h.

9. An engine test bench, characterized in that, The engine bench is used to implement the method for verifying the conversion efficiency of engine exhaust pollutants by DOC as described in any one of claims 1-8.

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