CH717326B1 - Calibration method for a diesel engine SCR device. - Google Patents

Abstract

In the present invention, a calibration method for an SCR device of a diesel engine is described for determining an NH 3 demand at a point to be calibrated, with different combinations of reference points being selected depending on the type of diesel engine, with an NH 3 demand Q NH 3 on is calculated at each reference point in the reference point combinations, with an ammonia ratio factor ƒ of the SCR at each reference point depending on the speed of the diesel engine and the power of the diesel engine at each reference point, with an ammonia ratio factor ƒ calibration of the SCR at the point to be calibrated depending on the ammonia ratio factor ƒ is calculated at each reference point in the reference point combinations, and an NH 3 demand Q NH 3 calibration at the point to be calibrated based on a relationship between ƒ calibration , a limit of the amount of emissions at the point to be calibrated Q NO X calibration , a Dre number of the diesel engine at the point of average value of speed powers n m , a power at the point of average value of speed powers P em , a speed n calibration at the point to be calibrated and a power P ecalibration at the point to be calibrated. The present invention adapts to the calibration requirements of different types of diesel engines through various combinations of reference points and realizes rapid calibration by diesel engine manufacturers.

Description

TECHNICAL AREA

The present invention belongs to the technical field of calibration in the aftertreatment of diesel engines and relates in particular to a calibration method for an SCR device (SCR=Selective Catalytic Reduction) of a diesel engine.

STATE OF THE ART

Combustion products of a diesel engine mainly include CO, HC, CO2, NOX gas and particulates. Regarding the technical treatment of the NOX gas emitted by the diesel engine, the selective catalytic reduction SCR (Selective Catalytic Reduction) is used on the market in addition to the exhaust gas recirculation EGR (Exhaust Gas Recirculation). The SCR mainly reduces the NOX gas in the exhaust gas through the reduction reaction of NH3 with NOXin urea, and has the features of good treatment effect and high overall efficiency.

[0003] The injection amount of the aqueous ammonia solution into an SCR device is related to the treatment efficiency of pollutants. Here, too small an injection amount may cause some of the NOX gas to not be processed effectively, while an excessive injection amount may cause an unreacted ammonia to react with other combustion products in the exhaust pipe to generate secondary pollutants or release it directly into the atmosphere is emitted and thus has a negative impact on the atmosphere. As a result, national emission regulations stipulate that the ammonia content in the exhaust gas from diesel engines must not exceed 10 ppm.

[0004] With the updating of the emission regulations, the calibration of the injection amount of the aqueous ammonia solution is unavoidable in the calibration work. The current method of calibrating the injection amount of the aqueous ammonia solution is that, according to the measurement standards and methods of national emission regulations, on the diesel engine test bench, the original NOX emissions of the diesel engine are measured point by point, and by injecting the aqueous ammonia solution, a reduction reaction between NH3 and NOX occurs, measuring and determining whether the NOX emission is within a limit value by various sensors mounted downstream of the SCR device, where if the result is negative the injection rate of the aqueous ammonia solution is adjusted in order to achieve definitive compliance with the ensure regulations. In summary, the calibration work is an iterative process that takes time and effort. The diesel engine test bench calibration procedure generally implements the 13 operating mode procedure, in which the R49 cycle calibration is mainly carried out in the second stage, and the European ESC cycle calibration is mainly carried out in the third to fifth stages. The above two calibration methods need to collect different data on 13 operation mode points of the diesel engine, so the two calibration methods are under double pressure from regulations and market demand. The calibration of the injection quantity of the ammonia according to the 13 operation mode method requires an enormous amount of work. Therefore, diesel engine manufacturers urgently need a simple, accurate and fast calibration procedure.

CONTENT OF THE PRESENT INVENTION

In view of the shortcomings of the prior art, the present invention proposes a calibration method for an SCR device of a diesel engine according to claim 1. The further claims indicate preferred embodiments. In the calibration method of the present invention, the ammonia ratio factors in SCR for the NOX emission limit can be set according to various emission regulations and standards. By establishing the correlation between a reference point and a point to be calibrated, the aqueous ammonia injection amount at each operation mode set point of the diesel engine can be easily and accurately calculated and determined to reduce the calibration workload of the aqueous ammonia injection amount and the ammonia leakage.

A possible technical embodiment of the present invention is as follows:

A calibration method for an SCR device of a diesel engine comprises the following steps:

S1. Choosing different combinations of reference points depending on the type of diesel engine, i.e. for vehicles, construction machinery and generator sets respectively; S2. Calculating an NH3 requirement QNH 3 at each reference point in the reference point combinations by specifying an NH3 requirement QNH 3 at the reference point depending on an original NOX emission amount QNO X originally at each reference point and a limit value QNO X limit of the NOX emission amount distributed at each reference point of the diesel engine, respectively is calculated using the following equations: QNH 3= QNO X reduction, QNO X reduction= QNO X original- QNO X limit; where QNO X reduction represents a NOX reduction amount at each reference point in mg/kWh; QNO X limit= ϕ QNO X total limit, where φ represents a NOX distribution rate at the reference point in % and QNO X total limit represents a total limit of the NOX emission amount of the diesel engine in mg/kWh; S3. Calculate an ammonia ratio factor ƒ of the SCR at each reference point in the reference point combinations by dividing the ammonia ratio factor of the SCR at each reference point by the equation depending on the NH3 demand QNH 3, the speed of the diesel engine at the point of average value of speed outputs nm(r/min), a power at the point of the average value of revolution powers Pem(kW), a limit value of the NOX emission amount QNO X limit, a revolution speed n of the diesel engine, and a power Pe of the diesel engine at each reference point; S4. Determining an ammonia ratio factor ƒCalibration of the SCR at a point to be calibrated depending on the ammonia ratio factor ƒ at each reference point in the reference point combinations, and determining an NH3 demand QNH 3 calibration at the point to be calibrated based on a relationship between ƒcalibration, a limit value of the NOx emission amount at QNO X calibration point, a speed of the diesel engine at the point of average value of speed powers nm, a power at the point of average value of speed powers Pem, a speed ncalibrationat the point to be calibrated and a power Pecalibrationat the point to be calibrated.

Furthermore, it is provided that the types of diesel engine are divided into a diesel engine for vehicles, a diesel engine for construction machinery and a diesel engine for generator sets.

Furthermore, it is provided that a selection rule of the reference point combinations is that in the diesel engine for vehicles the maximum torque point A, a calibration operating mode point B and a point C of the average value of speed performances are each selected as reference points, that in the diesel engine for construction machinery the maximum Torque point A and a calibration operation mode point B are selected as reference points, respectively, and that in the diesel engine for generator sets, a calibration operation mode point B is selected as a reference point.

It is further provided that a speed of the diesel engine at point C is the average value of speed power and a power at point C is the average value of speed power, where nA bzw. nB stands for a speed in r/min at the maximum torque point A and the calibration operating mode point B, respectively, and where PeA and PeB stands for a power at point A or at point B in kW.

It is further contemplated that in the vehicle diesel engine, the ammonia ratio factor of the SCR at the point to be calibrated is calculated by the following equations: where m is a percentage of speed at the point to be calibrated from a speed of a calibration mode of operation, n is a percentage of a load at the point to be calibrated point from a load of the calibration mode of operation, k1 represents an influence constant for the ammonia ratio factor of the SCR at the point to be calibrated, where k2, k3 and k4 represents a coupling influence constant for the ammonia ratio factor of the SCR at the maximum torque point A, the calibration operating mode point B, and the average value speed performance point C, respectively.

Furthermore, it is provided that the ammonia ratio factor of the SCR at the point to be calibrated is calculated by the following equations for diesel engines for construction machinery:

Furthermore, it is provided that in diesel engines for generator sets, the ammonia ratio factor of the SCR at the point to be calibrated is calculated using the following equations:

Beneficial effects of embodiments of the present invention can be: 1. Different combinations of reference points can be selected to adapt to calibration requirements of different types of diesel engines. Under the influence factors of different external environments and different pressurization modes, adjusting the influence constant and the coupling influence constant allows the calculations to better meet the technical requirements of the calibration works and the diesel engine manufacturers, and rapid calibration by the diesel engine manufacturers can be realized. 2. With calculation data of a small number of reference points, the need for the aqueous ammonia solution at the point to be calibrated is calculated, so that the workload of NOX calibration and the ammonia leakage are reduced. 3. After the calibration test is completed, the parameters of the injection quantity of the aqueous ammonia solution under different operating modes can correspond to technical parameters, such as diesel engine speed and power, and embedded in an electronic control unit, so that the diesel engine in the actual operating modes can call up relevant parameters and it allowing the aqueous ammonia solution to complete the reduction of NOX provided emission regulations are met.

BRIEF DESCRIPTION OF THE DRAWING

[0016] FIG. 1 shows a schematic view of a test on a diesel engine test bench; Figure 2 shows a schematic view of the selection of operating mode points and the calculation of ratio factors; FIG. 3 shows a schematic view of a method for calculating and calibrating an injection quantity of an aqueous ammonia solution.

Reference list:

01. Diesel engine, 02. Dynamometer, 03. Exhaust gas analyzer, 04. Fuel tank, 05. SCR device, 06. Urea tank, 07. Urea pump, 08. Flow regulator, 09. Nozzle, 10. Exhaust pipe before SCR device, 11. Exhaust pipe after SCR device.

DETAILED DESCRIPTION

In order to make the objects, technical features and advantages of the present invention clearer, the present invention will be described in detail with reference to the accompanying drawings and working examples. It should be understood that the specific embodiments described herein are intended to illustrate the present invention, not to limit the present invention.

As shown in Figure 1, the rapid calibration method for an ammonia ratio factor of an SCR of a diesel engine comprises the following steps:

S1. Selecting different combinations of reference points for different types of diesel engines, in the diesel engine for vehicles, the maximum torque point A, a calibration operation mode point B and a point C of the average value of speed performances are respectively selected as reference points, with a speed of the diesel engine at the point C of the average value of speed performances is and a power at point C is the average value of speed powers, where nAresp. nB stands for a speed in r/min at the maximum torque point A and the calibration mode of operation point B, respectively, and where PeA and PeB stands for a power at the maximum torque point A and at the calibration mode point B in kW, respectively, with the maximum torque point A and a calibration mode point B being respectively selected as reference points for the diesel engine for construction machinery, and for the diesel engine for gensets a calibration mode point B as reference point is selected (To simplify the description, the maximum torque point A, the calibration operation mode point B and the point C of the average value of speed performances are briefly described below as reference points A, B and C). S2. Calculate an NH3 requirement QNH 3 at point A, B and C using the example of the diesel engine for vehicles, the calculation process is as follows: S2.1. Recording of the respective speeds (nA, nBund nm) at reference points A, B and C, the respective powers (PeA, PeBund Pem) at reference points A, B and C as well as the respective original NOX emissions (QNO X originalA, QNO X originalBund QNO X originally C) at reference points A, B and C, the speed of the diesel engine at the point of average value of speed powers nm, the power at the point of average value of speed powers Pem, by testing under different operating modes of the selected diesel engine for vehicles; S2.2. Determination of the total limit value QNO X total limit of the NOX emission for the diesel engine for vehicles according to the national emission regulations, depending on the NOX distribution rate at each reference point, the limit values of the NOX emission quantity at the reference points A, B and C can be calculated, e.g. : where QNO X total limit represents the NOX limit value for the diesel engine for vehicles in mg/kWh set by the national emission regulations, where ϕ1, ϕ2respectively ϕ3 represents the NOX removal rate at reference point A, B or C in %, where depending on the emission regulations and standards, different diesel engine types and models, the NOX removal rate at different operating mode points varies, for example, the NOX removal rate at point A is about 10% to 20%, the value of the distribution rate can be measured by experiments or its range can be estimated based on an empirical formula; S2.3. Determination of the respective NH3 requirement QNH 3 at reference points A, B and C, e.g.:

S3. Calculate an ammonia ratio factor of the SCR at each reference point depending on the NH3 demand QNH 3, the speed of the diesel engine at the point of average value of speed powers nm, the power at the point of average value of speed powers Pem, the limit value QNO X limit of NOX emission, the speed n of the diesel engine and the power of the diesel engine at the reference points A, B and C, e.g.:

S4. determining an ammonia ratio factor of the SCR at a point to be calibrated depending on the ammonia ratio factor ƒ at each reference point in the reference point combinations, and determining an NH3 demand QNH 3 calibration at a point to be calibrated based on a relationship between ƒcalibration, a limit value of the NOx emission amount am point to be calibrated QNO X calibration, a speed of the diesel engine at the point of average value of speed powers nm, a power at the point of average value of speed powers Pem, a speed ncalibration at the point to be calibrated and a power Pecalibration at the point to be calibrated, as indicated by point D in figure 2, wherein the calculation process is: where m is a percentage of speed at the point to be calibrated to a speed of a calibration mode of operation, n is a percentage of a load at the point to be calibrated to a load of the calibration mode of operation, k1a comp assuming influence constant for the ammonia ratio factor of the SCR at the calibration point, where k2, k3 and k4 represents a coupling influence constant for the ammonia ratio factor of the SCR at point A, point B and point C, respectively. When the diesel engine is a construction machinery diesel engine, it is only necessary to obtain the ammonia ratio factors of the SCR at the reference points A and B as shown by point E in Figure 2, the ammonia ratio factor of the SCR at the calibration point being calculated by the following equations:

If the diesel engine is a genset diesel engine, only the ammonia ratio factor of the SCR at the reference point B needs to be determined, as shown by point F in Figure 2, the ammonia ratio factor of the SCR at the calibration point being calculated by the following equations:

In order to realize a fast calibration method for an ammonia ratio factor of a diesel engine SCR, the present application is based on a fast calibration system for an ammonia ratio factor of a diesel engine SCR, as shown in FIG. The calibration system comprises a diesel engine 01, the diesel engine 01 being connected to the dynamometer 02, the exhaust gas analyzer 03 and the fuel tank 04, respectively, the diesel engine 01 being connected to the SCR device 05 through an exhaust pipe 10, the exhaust pipe 10 having a nozzle 09 is mounted, the nozzle 09 being sequentially connected to the urea pump 07 and the urea tank 06 by piping, with a flow regulator 08 mounted in the connecting piping. Another exhaust pipe 11 is connected behind the SCR device 05 . The dynamometer 02 is rigidly connected to the diesel engine 01 to measure the speed and power of the diesel engine 01 under different operating modes. The exhaust gas analyzer communicates with an exhaust manifold of the diesel engine 01 and mainly measures the original NOX emissions of the diesel engine 01 under different operation modes. The SCR device 05 mainly provides catalysts and carriers for the reduction reaction of NH3 and NOx. The nozzle 09 sprays urea with a standard concentration of 32.5% to provide the ammonia as a raw material for the reduction reaction.

The above embodiments only serve to illustrate the design ideas and features of the present invention and aim to enable those skilled in the art to understand the gist of the present invention and implement it accordingly. The scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made within the scope of the claims based on the principles and design ideas disclosed in the present invention fall within the scope of the present invention.

Claims (9)

1. Calibration method for an SCR device (05) of a diesel engine (01) for determining an NH3 requirement at a point to be calibrated, characterized in that it comprises the following steps: S1. Choosing different combinations of reference points depending on the type of diesel engine; S2. Calculating an NH3 requirement QNH 3 at each reference point in the reference point combinations using NOX emission quantities measured at the respective reference point and limit values of the NOX emission quantity determined at the respective reference point; S3. From the NH3 requirement calculated in step S2, calculation of an ammonia ratio factor ƒ of the SCR at each reference point in the reference point combinations as a function of the speed and the power of the diesel engine at the respective reference point; S4. calculating an ammonia ratio factor ƒCalibration of the SCR at the point to be calibrated depending on the ammonia ratio factor ƒ at each reference point in the reference point combinations, and calculating the NH3 demand QNH 3 calibration at the point to be calibrated based on a relationship between ƒcalibration, a limit of the emission amount at the to be calibrated QNO X calibration point, a speed of the diesel engine at the point of average value of speed powers nm, a power at the point of average value of speed powers Pem, a speed ncalibrationat the point to be calibrated and a power Pecalibrationat the point to be calibrated. 2. Calibration method according to claim 1, characterized in that the type of diesel engine (01) is one of the following: a diesel engine for vehicles, a diesel engine for construction machines, and a diesel engine for generator sets. 3. Calibration method according to claim 2, characterized in that a selection rule of the reference point combinations is that in the case of the diesel engine (01) for vehicles, the maximum torque point A, a calibration operating mode point B and a point C of the average value of speed performances are each selected as reference points, that in the diesel engine (01) for construction machinery, the maximum torque point A and a calibration operation mode point B are respectively selected as reference points; and in the diesel engine (01) for generator sets, a calibration operation mode point B is selected as the reference point. 4. Calibration method according to claim 3, characterized in that a speed of the diesel engine (01) at point C is the average value of speed powers and a power at point C is the average value of speed powers Pem=, where nA, respectively. nB stands for a speed in r/min at the maximum torque point A and the calibration mode of operation point B, respectively, and where PeA and PeB stands for a power at the maximum torque point A and a power at the calibration operating mode point B in kW, respectively. 5. Calibration method according to claim 3, characterized in that in the diesel engine (01) for vehicles, the ammonia ratio factor of the SCR at the point to be calibrated is calculated by the following equations: where m is a percentage of the speed at the point to be calibrated from a speed of a calibration operating mode, n is a Percentage of a load at the point to be calibrated from a load of the calibration operation mode and k1 represents an influence constant for the ammonia ratio factor of the SCR at the point to be calibrated, where k2, k3 and k4 represents a coupling influence constant for the ammonia ratio factor of the SCR at the maximum torque point A, the calibration operating mode point B, and the average value speed performance point C, respectively, and where ƒA, ƒB, and ƒCrepresents the ammonia ratio factor of the SCR at the maximum torque point A, at the calibration operating mode point B, and at the average value speed performance point C, respectively. 6. Calibration method according to claim 3, characterized in that in the diesel engine (01) for construction machinery, the ammonia ratio factor of the SCR at the point to be calibrated is calculated by the following equations: where m is a percentage of the speed at the point to be calibrated from a speed of a calibration operating mode, n is a Percentage of a load at the point to be calibrated from a load of the calibration operation mode and k1 represents an influence constant for the ammonia ratio factor of the SCR at the point to be calibrated, where k2 and k3 represents a coupling influence constant for the SCR ammonia ratio factor at maximum torque point A and calibration mode point B, respectively, and where fA and ƒB represent the ammonia ratio factor of the SCR at maximum torque point A and calibration mode point B, respectively. 7. Calibration method according to claim 3, characterized in that in the diesel engine (01) for gensets, the ammonia ratio factor of the SCR at the point to be calibrated is calculated by the following equations: where m is a percentage of the speed at the point to be calibrated from a speed of a calibration operating mode, n is a Percentage of a load at the point to be calibrated from a load of the calibration mode of operation, and k1 represents an influence constant for the ammonia ratio factor of the SCR at the point to be calibrated, where k3 represents a coupling influence constant for the ammonia ratio factor of the SCR at the calibration mode of operation point B, and where ƒB represents the ammonia ratio factor of the SCR at the calibration mode of operation Point B represented. 8. Calibration method according to claim 1, characterized in that the NH3 requirement QNH3 is calculated by the following equations: QNH 3= QNO X reduction, QNO X reduction= QNO X original- QNO X limit; where QNO X —reduction is a NOX reduction amount at each reference point in mg/kWh, QNO X original is a measured NOX emission amount at each reference point in mg/kWh and QNO X limit is a limit of the distributed NOX emission amount of the diesel engine (01) at each reference point in mg /kWh represents; QNO X limit= ϕ QNO X total limit, where ϕ represents a NOX distribution rate at the reference point in % and QNO X total limit represents a total limit of the NOX emission quantity of the diesel engine (01) in mg/kWh. 9. Calibration method according to claim 8, characterized in that the ammonia ratio factor is the SCR at each reference point, where n represents a speed of the diesel engine (01) at the reference point in r/min and Pe represents a power output of the diesel engine (01) at the reference point in kW.