A method for analyzing the interaction between catalytic reactors and coupled aftertreatment systems under transient conditions of diesel engines

Abstract

The present invention relates to the technical field of diesel engine energy conservation and emission reduction, and discloses a method for analyzing the interaction between each catalytic reactor and a coupled post-processing system under transient working conditions of a diesel engine. A bench test is carried out on the diesel engine under transient working conditions, a diesel engine performance simulation model is built, a post-processing system simulation model is built, and the surface chemical reaction mechanism is simplified. The diesel engine post-processing conversion efficiency, the influence characteristics of each catalyst on each component, the interaction between the catalyst and the coupled post-processing system, and the capture rate of carbon smoke emissions are obtained by simulating the post-processing system simulation model. The method simplifies the surface chemical reaction mechanism of each catalyst, and uses the output of some original exhaust components of the accurately verified engine model and other components measured by bench experiments as the inlet boundary conditions of the post-processing system, so as to effectively study the conversion efficiency of the diesel engine post-processing system for exhaust pollutants and the interaction between each catalytic reactor and the coupled post-processing system.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine energy conservation and emission reduction, and in particular to a method for analyzing the interaction between various catalytic reactors and a coupled post-processing system under transient working conditions of a diesel engine. Background Art

[0002] The aftertreatment system can effectively reduce the emission pollutants of diesel engines and is an essential solution for diesel engines to meet relevant emission regulations. The catalysts in the diesel engine aftertreatment system affect each other. The interaction between the catalysts in the coupled state is particularly important for the conversion efficiency of emission pollutants, especially under transient conditions.

[0003] Currently, it is difficult to measure the interaction between the catalysts in the coupled state of the aftertreatment system only through experimental methods. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides an analysis method for the interaction between each catalytic reactor and the coupled after-treatment system under transient conditions of a diesel engine, which has the advantages of effectively studying the interaction between each catalytic reactor and the coupled after-treatment system, and solves the above-mentioned technical problems.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a method for analyzing the interaction between each catalytic reactor and a coupled post-treatment system under transient conditions of a diesel engine, comprising the following steps:

[0008] S1. Data acquisition: Conduct bench tests on diesel engines under transient conditions, and record engine performance, fuel consumption, control parameters, operating parameters, original exhaust, tail exhaust, intake and exhaust pressure and temperature data in real time;

[0009] S2. Build a diesel engine performance simulation model and verify the diesel engine performance simulation model. Then, perform simulation calculations under transient conditions through the diesel engine performance simulation model to obtain the components of water vapor and hydrogen in the original exhaust gas of the diesel engine, including the following steps:

[0010] S2.1. Use the Power module of GT suite software to build a diesel engine performance simulation model including the intake system, exhaust system, intercooler system, cylinder and crankcase transmission system, turbocharger system, and fuel injection system;

[0011] S2.2, setting the parameters of each system in the diesel engine performance simulation model established in step S2.1;

[0012] S2.3, using the data from the bench test in step S1 to set the boundary conditions of the system;

[0013] S2.4, using the data from the bench test in step S1, verify the diesel engine power, economy and emission characteristics calculated and analyzed by the diesel engine performance simulation model established by GT suite software;

[0014] S2.5, using the diesel engine performance simulation model verified in step S2.4 to perform simulation calculations under transient conditions, and obtain the components of water vapor and hydrogen in the original exhaust gas of the diesel engine;

[0015] S3. Build a simulation model of the post-treatment system, including a diesel oxidation catalytic reactor, a diesel particulate filter, a selective catalytic reduction device, and an ammonia purification catalyst;

[0016] S4, simplifying the surface chemical reaction mechanism in the post-treatment system simulation model in step S3, including simplifying the surface chemical reaction mechanism of the diesel oxidation catalytic reactor, simplifying the surface chemical reaction mechanism of the diesel particulate filter, simplifying the surface chemical reaction mechanism of the selective catalytic reduction device, and simplifying the surface chemical reaction mechanism of the ammonia purification catalyst;

[0017] S5. Setting boundary conditions of the post-processing system simulation model. The boundary conditions of the post-processing system simulation model are set by setting the exhaust temperature, pressure, total flow rate, and emission components of the original diesel engine exhaust under transient conditions obtained in the test, and the components of water vapor and hydrogen in the original diesel engine exhaust under transient conditions in step S2.5;

[0018] S6. The after-treatment system simulation model is used to perform simulation calculations to obtain the diesel engine after-treatment conversion efficiency, the influence characteristics of each catalyst on each component, the interaction between the catalyst and the coupled after-treatment system, and the capture rate of carbon smoke emissions.

[0019] As a preferred technical solution of the present invention, the expression of the combustion model of the cylinder in step S2 is as follows:

[0020]

[0021] Among them, Q B is the heat released by diesel fuel, in joules, H u is the lower calorific value of diesel, in joules / kilogram, g f is the cycle injection amount in milligrams, m is the diesel combustion quality index, is the combustion starting angle, is the combustion duration angle, e represents the natural logarithm, represents the crankshaft angle, Indicates the burning rate;

[0022] The heat transfer model expression of the cylinder in step S2 is as follows:

[0023]

[0024] Among them, Q W Q is the heat exchange between the mixed gas in the cylinder and the combustion chamber wall, in joules. Wi is the heat exchange of the ith region, in joules, is the heat exchange rate between the mixed gas in the cylinder and the combustion chamber wall, expressed in joules / crankshaft angle, a g is the average heat transfer coefficient in the cylinder, A i is the heat transfer area of ​​the ith region, in square millimeters. A1, A2, and A3 represent the heat transfer areas of the piston top surface, cylinder liner surface, and cylinder bottom surface, respectively. T is the temperature of the mixed gas in the cylinder, in Kelvin. T Wi is the wall temperature of the ith combustion chamber in Kelvin, T W1 、T W2 、T W3 They represent the wall temperatures of the piston top surface, cylinder liner surface and cylinder bottom surface respectively.

[0025] As a preferred technical solution of the present invention, the surface chemical reaction mechanism in step S4 satisfies the following expression:

[0026]

[0027] Among them, R is the chemical reaction rate, K is the pre-exponential factor, T is the temperature of the mixed gas in the cylinder, T b It represents the temperature T of the gas in the cylinder to the power of b, the superscript b is the temperature index, E a is the activation energy independent of temperature, {conc} is the expression for the reactant concentration, G(j) is the expression for the inhibition equation for different emission components, and θ(j) is the expression for the coverage of different emission components.

[0028] As a preferred technical solution of the present invention, the emission components originally discharged from the diesel engine in step S5 include hydrocarbons HC, carbon monoxide CO, nitrogen monoxide NO, nitrogen dioxide NO2, soot PM, carbon dioxide CO2 and oxygen O2.

[0029] Compared with the prior art, the present invention provides a method for analyzing the interaction between each catalytic reactor and the coupled post-treatment system under transient conditions of a diesel engine, which has the following beneficial effects:

[0030] The present invention simplifies the chemical reaction mechanism on the surface of each catalyst, and uses part of the original exhaust component output of the accurately calibrated engine model and other components measured in bench experiments as the inlet boundary conditions of the after-treatment system, so as to effectively study the conversion efficiency of the diesel engine after-treatment system for exhaust pollutants and the interaction between each catalytic reactor and the coupled after-treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the flow curve of H2 at the inlet of the post-treatment system model obtained by performance simulation of the present invention;

[0032] Figure 2 This is a schematic diagram of an air intake flow input data curve of the present invention;

[0033] Figure 3 It is a schematic diagram of a simulation curve of the filtering effect of the post-treatment system and DPF on PM of the present invention;

[0034] Figure 4 This is a schematic diagram showing the effect of the inlet temperature of the post-treatment system of the present invention on the reaction rate of NO in DOC;

[0035] Figure 5 It is a schematic diagram of the simulation characteristic curve of the SCR oxidation of NO and NO2 of the present invention;

[0036] Figure 6 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1-Figure 6 The present invention provides the following technical solution: a method for analyzing the interaction between each catalytic reactor and the coupled post-treatment system under transient conditions of a diesel engine, comprising the following steps:

[0039] S1. Data acquisition: Conduct bench tests on diesel engines under transient conditions, and record engine performance, fuel consumption, control parameters, operating parameters, original exhaust, tail exhaust, intake and exhaust pressure and temperature data in real time;

[0040] S2. Build a diesel engine performance simulation model and verify the diesel engine performance simulation model. Then, perform simulation calculations under transient conditions through the diesel engine performance simulation model to obtain the components of water vapor and hydrogen in the original exhaust gas of the diesel engine, including the following steps:

[0041] S2.1. Use the Power module of GTsuite software to build a diesel engine performance simulation model including the intake system, exhaust system, valve train, intercooler system, cylinder and crankcase transmission system, turbocharger system, and fuel injection system;

[0042] S2.2, setting the parameters of each system in the diesel engine performance simulation model established in step S2.1;

[0043] Specifically include:

[0044] Input the structural parameters of each component in the intake and exhaust pipes, intake and exhaust ducts, and intake and exhaust valves in the intake and exhaust systems, such as length, volume, diameter, etc.;

[0045] In the cylinder, the combustion model and heat transfer model are selected and set. The basic combustion model in the cylinder adopts the Weber combustion model, which is mainly based on chemical reaction kinetics combined with a large number of experimental summaries, as shown in the following formula:

[0046]

[0047] Among them, Q B is the heat released by diesel fuel, in joules, H u is the lower calorific value of diesel, in joules / kilogram, g f is the cycle injection amount in milligrams, m is the diesel combustion quality index, is the combustion starting angle, is the combustion duration angle, e represents the natural logarithm, represents the crankshaft angle, Indicates the burning rate;

[0048] The heat transfer model of the cylinder is the WoschniGT heat transfer model, as shown in the following formula:

[0049]

[0050] Among them, Q W Q is the heat exchange between the mixed gas in the cylinder and the combustion chamber wall, in joules. W Q is the heat exchange between the mixed gas in the cylinder and the combustion chamber wall, in joules. Wi is the heat exchange of the ith region, in joules, is the heat exchange rate between the mixed gas in the cylinder and the combustion chamber wall, expressed in joules / crankshaft angle, a g is the average heat transfer coefficient in the cylinder, A iis the heat transfer area of ​​the ith region, in square millimeters. A1, A2, and A3 represent the heat transfer areas of the piston top surface, cylinder liner surface, and cylinder bottom surface, respectively. T is the temperature of the mixed gas in the cylinder, in Kelvin. T Wi is the wall temperature of the ith combustion chamber in Kelvin, T W1 , T W2 , T W3 Respectively represent the wall temperature of the piston top surface, cylinder liner surface and cylinder bottom surface; in the valve train module, relevant parameters such as intake and exhaust valve lift curve, valve timing, intake and exhaust valve flow coefficient need to be input;

[0051] In addition to the diesel engine cylinder diameter and stroke, the crankcase drive system also requires the input of connecting rod length, compression ratio, ignition sequence, maximum speed, etc.

[0052] The turbocharger system needs to input the reference temperature, reference pressure, speed characteristics, flow characteristics, pressure ratio and efficiency of the compressor and turbine;

[0053] In the fuel injection system, it is necessary to input parameters such as injection amount, injection timing, injection temperature, number of nozzles, and nozzle diameter. In this model, the speed control mode is selected for the transient working condition, and the load is controlled by the injection amount of the injector, thereby realizing the joint control of speed and load. The relevant parameters of load and injector injection amount can be obtained by bench test in S1;

[0054] S2.3, using the data from the bench test in step S1 to set the boundary conditions of the system;

[0055] S2.4, using the data from the bench test in step S1, verify the diesel engine power, economy and emission characteristics obtained by the diesel engine performance simulation model established by GTsuite software;

[0056] S2.5, using the diesel engine performance simulation model verified in step S2.4 to perform simulation calculations under transient conditions, and obtain the components of water vapor H2O and hydrogen H2 in the original exhaust gas of the diesel engine;

[0057] S3. Use the post-treatment system module of GTsuite software to build a post-treatment system structure model including a diesel oxidation catalyst reactor (DOC), a diesel particulate filter (DPF), a selective catalytic reducer (SCR) and an ammonia purification catalyst (ASC). At the same time, input the main structural parameters and material characteristic parameters, such as diameter, length, volume, mesh number, carrier, catalyst distribution, etc., into each catalyst structure module;

[0058] S4, simplifying the surface chemical reaction mechanism in the post-treatment system simulation model in step S3, including simplifying the surface chemical reaction mechanism of the diesel oxidation catalytic reactor, simplifying the surface chemical reaction mechanism of the diesel particulate filter, simplifying the surface chemical reaction mechanism of the selective catalytic reduction device, and simplifying the surface chemical reaction mechanism of the ammonia purification catalyst;

[0059] The surface chemical reaction mechanism in step S4 satisfies the following expression:

[0060]

[0061] Among them, R is the chemical reaction rate, K is the pre-exponential factor, T is the temperature of the mixed gas in the cylinder, T b It represents the temperature T of the gas in the cylinder to the power of b, the superscript b is the temperature index, E a is the activation energy independent of temperature, {conc} is the expression for the reactant concentration, G(j) is the expression for the inhibition equation for different emission components, and θ(j) is the expression for the coverage of different emission components;

[0062] Simplified chemical reaction mechanism on the surface of diesel engine oxidation catalytic reactor:

[0063] The surface chemical reactions of the oxidation catalytic reactor mainly select the following three reaction equations:

[0064]

[0065] The main parameters of the simplified chemical reaction mechanism of the oxidation catalytic reactor surface are shown in the following table. The pre-exponential factor and activation energy are accurate values ​​after simplification. In the following table, G(1) is the inhibition equation of CO, G(2) is the inhibition equation of NO, G(3) is the inhibition equation of HC, G(4) is the NO oxidation conversion coefficient, and G(5) is the NO oxidation equilibrium constant:

[0066]

[0067]

[0068] Wherein, T is the temperature of the mixed gas in the cylinder, {CO} is the CO concentration, {NO} is the NO concentration, {DF1} is the concentration of diesel in liquid state, and {DF2} is the concentration of diesel in gaseous state;

[0069]

[0070] Simplified chemical reaction mechanism on the surface of diesel particulate filter:

[0071] The chemical reaction on the surface of diesel particulate filter mainly selects the following reaction equations:

[0072] C+NO2→NO+CO(R-4)

[0073] The passive continuous regeneration of diesel particulate filter belongs to solid-gas reaction, and the pre-exponential factor and activation energy of this reaction are 5.6×10 6 and 66.52 kJ / mol;

[0074] Simplified chemical reaction mechanism on the surface of selective catalytic reduction:

[0075] The surface chemical reaction of the selective catalytic reduction device mainly selects the following three reaction equations:

[0076] 4NO+4NH3+O2→4N2+6H2O(R-5)

[0077] 2NH3+NO+NO2→2N2+3H2O(R-6)

[0078] 6NO2+8NH3→7N2+12H2O(R-7)

[0079] The main parameters of the simplified chemical reaction mechanism on the surface of the selective catalytic reducer are shown in the following table. The pre-exponential factor and activation energy are accurate values ​​after simplification.

[0080]

[0081] Simplified chemical reaction mechanism on the surface of ammonia purification catalyst:

[0082] The chemical reactions on the surface of ammonia purification catalyst mainly include the following five reaction equations:

[0083] urea→NH3+HNCO(R-8)

[0084] HNCO+H2O→NH3+CO2(R-9)

[0085]

[0086] The main parameters of the simplified chemical reaction mechanism on the surface of the ammonia purification catalyst are shown in the following table. The pre-exponential factor and activation energy are accurate values ​​after simplification.

[0087]

[0088] The simplified chemical equations and main parameters are input into the chemical reaction mechanism solver in GTSuite software to simplify the chemical reaction mechanism on the surface of each catalyst;

[0089] S5. Setting the boundary conditions of the post-processing system simulation model. The boundary conditions of the post-processing system simulation model are set by setting the exhaust temperature, pressure, total flow rate, and original exhaust emission components of the diesel engine under transient conditions obtained in the test, and the components of water vapor and hydrogen in the original exhaust of the diesel engine under transient conditions in step S2.5. The original exhaust emission components of the diesel engine include hydrocarbons HC, carbon monoxide CO, nitric oxide NO, nitrogen dioxide NO2, soot PM, carbon dioxide CO2, and oxygen O2;

[0090] S6. The after-treatment system simulation model is used to perform simulation calculations to obtain the diesel engine after-treatment conversion efficiency, the influence characteristics of each catalyst on each component, the interaction between the catalyst and the coupled after-treatment system, and the capture rate of carbon smoke emissions;

[0091] Through GTsuite post-treatment system simulation calculation, the tail exhaust of each diesel engine can be obtained, and the conversion efficiency of each exhaust pollutant by the diesel engine post-treatment system can be obtained by (original exhaust-tail exhaust) / original exhaust.

[0092] Through GTsuite post-treatment system simulation calculation, the emission pollutant components at the outlet of each catalyst in the post-treatment system and the components of the intermediate products produced can be obtained, and then the influence characteristics of each catalyst on each component and the interaction between the catalyst and the coupled post-treatment system can be obtained;

[0093] For PM emissions, through GTsuite post-treatment system simulation calculation, we can use the (R-4) reaction in S4 to analyze the changing characteristics of NO2 in the diesel particulate filter (DPF) to obtain the PM passive regeneration characteristics, and then combine the overall PM conversion efficiency in S6 to obtain the PM capture rate in the diesel particulate filter (DPF);

[0094] During the simulation analysis of the conversion efficiency of diesel engine aftertreatment system for various pollutants, due to the limitations of test conditions and instruments, only partial boundary conditions can be obtained from experimental tests, and the chemical reaction mechanism of each catalyst is complex. By simplifying the chemical reaction mechanism on the surface of each catalyst, and using some original exhaust component outputs of the accurately calibrated engine model and other components measured in bench experiments as the inlet boundary conditions of the aftertreatment system, the conversion efficiency of the diesel engine aftertreatment system for exhaust pollutants and the interaction between each catalytic reactor and the coupled aftertreatment system are effectively studied.

[0095] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for analyzing the interaction between each catalytic reactor and a coupled post-treatment system under transient conditions of a diesel engine, characterized in that: The following steps are involved: S1. Data acquisition: Conduct bench tests on diesel engines under transient conditions, and record engine performance, fuel consumption, control parameters, operating parameters, original exhaust, tail exhaust, intake and exhaust pressure and temperature data in real time; S2. Build a diesel engine performance simulation model and verify the diesel engine performance simulation model. Then, perform simulation calculations under transient conditions through the diesel engine performance simulation model to obtain the components of water vapor and hydrogen in the original exhaust gas of the diesel engine, including the following steps: S2.

1. Use the Power module of GT suite software to build a diesel engine performance simulation model including the intake system, exhaust system, intercooler system, cylinder and crankcase transmission system, turbocharger system, and fuel injection system; S2.2, setting the parameters of each system in the diesel engine performance simulation model established in step S2.1; S2.3, using the data from the bench test in step S1 to set the boundary conditions of the system; S2.4, using the data from the bench test in step S1, verify the diesel engine power, economy and emission characteristics calculated and analyzed by the diesel engine performance simulation model established by GT suite software; S2.5, using the diesel engine performance simulation model verified in step S2.4 to perform simulation calculations under transient conditions, and obtain the components of water vapor and hydrogen in the original exhaust gas of the diesel engine; S3. Build a simulation model of the post-treatment system, including a diesel oxidation catalytic reactor, a diesel particulate filter, a selective catalytic reduction device, and an ammonia purification catalyst; S4, simplifying the surface chemical reaction mechanism in the post-treatment system simulation model in step S3, including simplifying the surface chemical reaction mechanism of the diesel oxidation catalytic reactor, simplifying the surface chemical reaction mechanism of the diesel particulate filter, simplifying the surface chemical reaction mechanism of the selective catalytic reduction device, and simplifying the surface chemical reaction mechanism of the ammonia purification catalyst; S5. Setting boundary conditions of the post-processing system simulation model. The boundary conditions of the post-processing system simulation model are set by setting the exhaust temperature, pressure, total flow rate, and emission components of the original diesel engine exhaust under transient conditions obtained in the test, and the components of water vapor and hydrogen in the original diesel engine exhaust under transient conditions in step S2.5; S6. The after-treatment system simulation model is used to perform simulation calculations to obtain the diesel engine after-treatment conversion efficiency, the influence characteristics of each catalyst on each component, the interaction between the catalyst and the coupled after-treatment system, and the capture rate of carbon smoke emissions.

2. The method for analyzing the interaction between each catalytic reactor and the coupled post-treatment system under transient conditions of a diesel engine according to claim 1, characterized in that: The expression of the combustion model of the cylinder in step S2 is as follows: Among them, Q B is the heat released by diesel fuel, in joules, H u is the lower calorific value of diesel, in joules / kilogram, g f is the cycle injection amount in milligrams, m is the diesel combustion quality index, is the combustion starting angle, is the combustion duration angle, e represents the natural logarithm, represents the crankshaft angle, Indicates the burning rate; The heat transfer model expression of the cylinder in step S2 is as follows: Among them, Q W Q is the heat exchange between the mixed gas in the cylinder and the combustion chamber wall, in joules. Wi is the heat exchange of the ith region, in joules, is the heat exchange rate between the mixed gas in the cylinder and the combustion chamber wall, expressed in joules / crankshaft angle, a g is the average heat transfer coefficient in the cylinder, A i is the heat transfer area of ​​the ith region, in square millimeters. A1, A2, and A3 represent the heat transfer areas of the piston top surface, cylinder liner surface, and cylinder bottom surface, respectively. T is the temperature of the mixed gas in the cylinder, in Kelvin. T Wi is the wall temperature of the ith combustion chamber in Kelvin, T W1 , T W2 , T W3 They represent the wall temperatures of the piston top surface, cylinder liner surface and cylinder bottom surface respectively.

3. The method for analyzing the interaction between each catalytic reactor and the coupled post-treatment system under transient conditions of a diesel engine according to claim 1, characterized in that: The surface chemical reaction mechanism in step S4 satisfies the following expression: Among them, R is the chemical reaction rate, K is the pre-exponential factor, T is the temperature of the mixed gas in the cylinder, T b It represents the temperature T of the gas in the cylinder to the power of b, the superscript b is the temperature index, E a is the activation energy independent of temperature, {conc} is the expression for the reactant concentration, G(j) is the expression for the inhibition equation for different emission components, and θ(j) is the expression for the coverage of different emission components.

4. The method for analyzing the interaction between each catalytic reactor and the coupled post-treatment system under transient conditions of a diesel engine according to claim 3, characterized in that: The components of the original exhaust gas from the diesel engine in step S5 include hydrocarbons HC, carbon monoxide CO, nitrogen monoxide NO, nitrogen dioxide NO2, soot PM, carbon dioxide CO2 and oxygen O2.

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