CN102562237B - The control method of addition amount of reducing agent in diesel engine tail gas treatment device - Google Patents

Abstract

The present invention relates to the control method of a kind of addition amount of reducing agent in diesel engine tail gas treatment device, it is characterized in that: first according to corresponding relation between NOx residual volume in the concrete operating point addition amount of reducing agent of diesel engine and tail gas, and with rules and regulations NOx emission limit value for constraints, optimizing obtains this operating point the best addition amount of reducing agent. Target makes NOx discharge and ammonia amount of leakage in tail gas meet under the premise of laws and regulations requirement so that addition amount of reducing agent is minimum, improves the utilization rate of reducing agent. Then, using the addition amount of reducing agent after optimization as aim parameter under diesel engine limit, the three-dimensional MAP of diesel engine speed, oil mass and reducing agent optimum injected volume is set up. In actual applications, obtain diesel engine actual speed and oil mass data in real time, inquire about above-mentioned three-dimensional MAP, obtain the basic value of addition amount of reducing agent, and with actual catalyst converter for core, carry out transient state correction, it is thus achieved that the injected volume of final reducing agent.

Description

The control method of addition amount of reducing agent in diesel engine tail gas treatment device

Technical field

The present invention relates to the control method of a kind of addition amount of reducing agent in diesel engine tail gas treatment device, be especially the control method of a kind of reducing agent in diesel engine tail gas treatment device optimum injected volume.

Background technology

At present, motor vehicle emission problem is increasingly paid attention to by countries in the world government, and the formulation of the Abgasgesetz of increasingly stringent has promoted the development of Exhaust Control of Engine technology. It is generally believed that according to current present situation, diesel engine relies solely on Optimized Measures in machine can not meet the requirement of China's stage iv discharge standard, reaches stage iv discharge standard and must adopt exhaust gas processing device. Meanwhile, diesel engine optimization designs to improve efficiency of combustion, it is possible to increase fuel utilization ratio, reduces oil consumption, reduces the use cost of diesel engine. But optimize burning and result in the increase of NOx discharge in tail gas. Therefore, in conjunction with the practical situation of China, in numerous diesel engine vent gas after-treatment devices, SCR technology is generally considered China's diesel engine and realizes the best-of-breed technology route of stage iv discharge standard.

In existing exhaust gas processing device, the control method of addition amount of reducing agent mainly considers that ammonia is revealed and laws and regulations requirement, is determined by the method for great many of experiments debugging and engineering experience, which increases calibration cost, and have some limitations. Chinese patent CN101680345A discloses the emission-control equipment controlling device and control method and internal combustion engine of a kind of emission-control equipment, the method can when the lasting given time of catalyst temperature be divided a word with a hyphen at the end of a line to low temperature side with Shangdi, the actual adsorbance being prevented from ammonia reduces from saturated extent of adsorption curved transition, it is possible to prevent the reduction of reducing agent reduction efficiency. Chinese patent CN1804378A discloses the system of a kind of urea supply for controlling to SCR catalyst, this system gives control system for the reductant metering used in the selective catalytic reduction system operating of motor vehicles, its basis metering gives module and carries out the calculating to the reduction dosage injected before the SCR catalyst of SCR system based on NOx feedback, exports and signals occurs either periodically or continuously to supply reducing agent to reductant metering mechanism based on described calculating.Chinese patent CN101245727A discloses control practical in a kind of SCR system of diesel engine and adds the control method of blue injected volume and control device. Reducing agent flow is expressed as the function of rotating speed and torque by the method, by simply obtaining diesel engine speed and torque, it is judged that diesel engine condition point, controls reducing agent flow. In the control method patent of existing similar addition amount of reducing agent in diesel engine tail gas treatment device, reducing agent is thrown in control strategy research relatively more, do not relate to the optimum control of addition amount of reducing agent, optimum addition amount of reducing agent control method enables to NOx discharge and ammonia leakage amount in tail gas and meets under the premise of laws and regulations requirement, make addition amount of reducing agent minimum, improve the utilization rate of reducing agent.

Diesel engine actual operating mode is likely to cover all situations that external characteristic curve comprises, and when different operating mode is run, amount of fuel that its charge flow rate, every cylinder spray into, EGT etc. all exist a degree of difference. This results in the difference that exhaust gas processing device exists in efficiency when catalyzed conversion NOx. In GB17691-2005 " automobile-used compression-ignited, gas ignition formula electromotor and automobile exhaust pollutant discharge limit value and measuring method ", regulation ESC experiment condition point is 13 operating points including idling, under different operating modes there is larger difference in exhaust gas flow, EGT, causes that catalyst converter transformation efficiency has height to have low. And the weight of difference operating point in the end weighted sum also differs. Therefore, making carbamide spray total amount minimum when how last discharge index being met national regulation limit value is a very actual problem. Optimum urea injecting quantity can improve reducing agent utilization rate when ensureing to discharge qualified, reduces the use cost of user.

Summary of the invention

Defect according to prior art and deficiency, the purpose of the present invention and task are to provide the control method of a kind of addition amount of reducing agent in diesel engine tail gas treatment device, specifically: first according to corresponding relation between NOx residual volume in the concrete operating point addition amount of reducing agent of diesel engine and tail gas, and with rules and regulations NOx emission limit value for constraints, optimizing obtains this operating point the best addition amount of reducing agent. Target makes NOx discharge and ammonia amount of leakage in tail gas meet under the premise of laws and regulations requirement so that addition amount of reducing agent is minimum, improves the utilization rate of reducing agent. Then, using the addition amount of reducing agent after optimization as aim parameter under diesel engine limit, the three-dimensional MAP of diesel engine speed, oil mass and reducing agent optimum injected volume is set up. In actual applications, obtain diesel engine actual speed and oil mass data in real time, inquire about above-mentioned three-dimensional MAP, obtain the basic value of addition amount of reducing agent, and with actual catalyst converter for core, carry out transient state correction, it is thus achieved that the injected volume of final reducing agent.

Technical solution of the present invention: the control method of addition amount of reducing agent in diesel engine tail gas treatment device, implements process as follows:

First, based on diesel engine speed and oil mass, the basic control point of reasonable selective reduction agent injected volume. Basic control point selection principle is: diesel engine speed is to divide for step-length less than or equal to 10% times of maximum (top) speed; Oil mass is to divide with 10% times of maximum oil mass for step-length; If basic control point is close to rules and regulations experiment condition point, then replace original basic point with rules and regulations experiment condition point. Target operating condition point selects in basic control point.In experimentation, it is determined that rotating speed in concrete basic control point, corresponding relation between oil mass and moment of torsion, charge flow rate, exhaust temperature, NOx concentration and other ambient parameters. Then, setting up the corresponding relation between NOx residual volume in addition amount of reducing agent and tail gas on target operating condition point, maximum addition amount of reducing agent is limited without departing from laws and regulations requirement with ammonia amount of leakage in tail gas. On the basis of above-mentioned experimental data, set up reducing agent optimum injected volume optimized mathematical model: addition amount of reducing agent is for object function on target operating condition point, the emission limit of rules and regulations tail gas NOx is constraints, carry out optimizing, meet NOx emission to reach to make addition amount of reducing agent minimum in limit value situation, obtain the conversion rate of NOx of correspondence simultaneously. Other base regime point addition amount of reducing agents are obtained by interpolation according to the optimal amount of above-mentioned target operating condition point. Here addition amount of reducing agent is diesel engine target injected volume under steady state conditions, diesel engine actual operating mode is in the majority with transient state, under transient condition point, catalyst temperature is bigger with difference under stable state, therefore, introduce the transient state correction being core with catalyst temperature, improve the reasonable employment rate of addition amount of reducing agent in diesel engine tail gas treatment device.

Compared with prior art the superiority of the present invention is mainly reflected in: the control method of the addition amount of reducing agent in diesel engine tail gas treatment device that the present invention proposes is with diesel engine speed, oil mass is basic control point, with corresponding relation between operating point reducing agent intake and tail gas NOx residual volume for foundation, in rules and regulations tail gas NOx limit value and for wherein ammonia amount of leakage limit value be constraint, set up Optimized model, mathematically reducing agent the best intake of each operating point is determined in optimizing, to reach to meet under the premise of emission request, improve the utilization rate of reducing agent, the use cost of user is reduced with this. simultaneously, it is contemplated that actual diesel engine is mostly in transient condition, the transient state correction being core with catalyst temperature is introduced so that final addition amount of reducing agent more conforms to the demand of actual diesel engine exhaust gas processing device.

Accompanying drawing explanation

Fig. 1 is diesel engine exhaust gas treatment device addition amount of reducing agent basic control principle figure.

Fig. 2 is certain model electromotor corresponding relation between certain three experiment condition point addition amount of reducing agents and tail gas NOx residual volume.

Fig. 3 is reducing agent in diesel engine tail gas treatment device optimum injected volume optimized mathematical model schematic diagram.

Fig. 4 is genetic algorithm optimizing ultimate principle figure.

Fig. 5 is that the lower addition amount of reducing agent of ESC experiment optimizes process schematic.

Detailed description of the invention

Below in conjunction with accompanying drawing, describe control mode and the preferred embodiment of reducing agent in diesel engine tail gas treatment device optimum injected volume of the present invention in detail.

Accompanying drawing 1 is addition amount of reducing agent in diesel engine tail gas treatment device basic control principle figure. In control process, obtaining diesel engine speed and oil mass in real time, inquiry is demarcated MAP table and is obtained addition amount of reducing agent basic value, then carries out transient state correction according to parameters such as catalyst temperatures. Addition amount of reducing agent is too many, can cause that in tail gas, ammonia leakage amount exceedes laws and regulations requirement, causes secondary pollution. Addition amount of reducing agent is very few, then can cause that in tail gas, NOx discharge exceeds standard. Therefore, how addition amount of reducing agent is rationally demarcated most important. In usual control method, the control method of addition amount of reducing agent is under meeting ammonia sliding mistake requirement condition, it is ensured that in tail gas, NOx discharge is less than prescribed limits.For obtaining the addition amount of reducing agent meeting requirement, it usually needs do and take turns experiment more, by the experience of calibration engineer, groped by the method for " gathering in both sides ", there is certain blindness. Mathematically search for, it is demonstrated experimentally that provided by the invention, the global optimum's addition amount of reducing agent satisfied condition, reliably effectively, it is possible to increase carbamide service efficiency, reduce customer using cost.

Diesel engine is under different operating modes, and exhaust gas flow, EGT etc. all exist a degree of difference, causes that NOx conversion efficiency is also not quite similar by exhaust gas processing device under different operating modes. It is demonstrated experimentally that in diesel engine exhaust gas treatment device the transformation efficiency of catalyst converter between 30%��90% not etc. Fig. 2 shows certain model diesel engine corresponding relation between remaining NOx concentration in reducing agent intake and tail gas under basic, normal, high three place's rotating speeds and different load. Abscissa is addition amount of reducing agent, and vertical coordinate is NOx residual volume in tail gas. Can also being clear that from figure operating mode is different residing for diesel engine, there is larger difference in the former machine discharge capacity of NOx, reducing agent intake is very big to the conversion ratio also difference of NOx. It addition, diesel engine is under stationary conditions, between reducing agent intake and NOx reduction amount neither simple linear relationship, but be similar to piecewise linearity. Therefore, when determining reducing agent intake, it is impossible to obtained by theory analysis simple computation, it should prove by experiment. In experimentation, first stablize operating mode residing for diesel engine, till waiting until that exhaust temperature does not fluctuate at short notice, record the former machine NOx emission of now diesel engine. Subsequently, spraying into reducing agent with given pace in tail gas, record is remaining NOx amount now. It is stepped up reducing agent intake, records the corresponding relation between remaining NOx concentration and reducing agent intake in tail gas. Meanwhile, the amount of leakage of monitoring ammonia, when ammonia amount of leakage exceedes prescribed limits, reducing agent intake now is the maximum intake of reducing agent under this operating mode, i.e. reducing agent intake higher limit. By above-mentioned experiment, it is thus achieved that the corresponding relation between reducing agent intake and NOx reduction amount, it it is the experiment basis of reducing agent optimum injected volume.

Fig. 3 is reducing agent in diesel engine tail gas treatment device optimum injected volume optimized mathematical model schematic diagram. Specify that experiment condition describes modeling process in detail below by ESC. In model, object function is to ask 13 operating point reducing agents to take in total amount minima, i.e. n=13, constraints be NOx emission limit value within rules and regulations scope, simultaneously reducing agent intake is less than above-mentioned higher limit. That is: minf (x) s.t.Wherein, x is the vector of 13 row 1 row, and each element represents the reducing agent intake of 13 operating points; F (x) is object function, i.e. reducing agent intake summation; S.t. writing a Chinese character in simplified form for subjectto, represents constraints; Ub is the vector of 13 row 1 row, and each component represents reducing agent under corresponding operating mode and takes in higher limit, and this value requires to determine less than rules and regulations by NH3 amount of leakage; G (x) is the difference of NOx emission value in tail gas Yu rules and regulations limit value. After constraints ensure that optimization, the amount of leakage of NH3 and NOx discharge are satisfied by rules and regulations.

After model establishes, concrete optimization method is varied, and Newton's algorithm, genetic algorithm, gradient search procedure etc. can both realize concrete iterative process, it is thus achieved that optimal solution. Fig. 4, for genetic algorithm, describes concrete searching process. When genetic algorithm starts, always random generation some individual (initial solutions), according to predetermined object function, each individuality is evaluated, provides a fitness value.Select individual replicate of future generation according to fitness value. Selecting operation to embody the principle of " survival of the fittest ", the individuality that fitness value is high is selected to replicate, and the individuality that fitness value is low is then eliminated. Then the individuality chosen carries out recombinant through crossover operator and mutation operator and generates a new generation. The new colony of this generation inherits some merits of previous generation colony, thus is better than previous generation. Thus evolve towards the direction of more excellent solution.

Fig. 5 is that under ESC experiment condition, addition amount of reducing agent optimizes process. Optimization process iteration altogether 82 times, when iterating to about 40 times, addition amount of reducing agent is close to optimal solution. Iteration initial point is certain company original ESC operating point reducing agent total input, and for 962mL, now outlet NOx discharge is 3.14g/kwh; Addition amount of reducing agent after optimization is 848.88mL, and final outlet NOx discharge is 3.12g/kwh. Before and after optimizing, addition amount of reducing agent reduces by 11.7%, and NOx emission value is basically unchanged. As can be seen here, the present invention under keeping the NOx premise meeting emission regulation demands, can reduce addition amount of reducing agent, improve the service efficiency of reducing agent, reduce the use cost of user.

Above-described detailed description of the invention, including cited optimization method schematic diagram, can have multiple modification and change in the scope that present invention and claim cover. Therefore, described embodiment is not intended that the restriction to the claims in the present invention protection domain.

Claims (3)

1. the control method of an addition amount of reducing agent in diesel engine tail gas treatment device, it is characterized in that: first obtain under steady state condition the corresponding relation between NOx residual volume in addition amount of reducing agent and tail gas, wherein the maximum injected volume of operating point reducing agent determines that principle is ensure that under this operating mode, the leakage rate of ammonia is less than the limit value of rules and regulations, on this basis with the addition amount of reducing agent of target operating condition point, NOx residual volume and rules and regulations NOx emission limit value set up optimized mathematical model, optimizing obtains the optimal value of addition amount of reducing agent, target makes NOx discharge and ammonia leakage amount in tail gas meet under the premise of laws and regulations requirement, make addition amount of reducing agent minimum, improve the utilization rate of reducing agent, then, target operating condition point reducing agent optimum injected volume is obtained according to optimized mathematical model, the addition amount of reducing agent of other operating points is then obtained by above-mentioned optimal value interpolation, thus setting up diesel engine speed within the scope of diesel engine steady state condition, oil mass and reducing agent optimum injected volume three-dimensional MAP, in actual applications, obtain diesel engine actual speed and oil mass data in real time, inquire about above-mentioned three-dimensional MAP, obtain the basic value of addition amount of reducing agent, and with actual catalyst converter for core, carry out transient state correction, it is thus achieved that final addition amount of reducing agent.

2. the control method of addition amount of reducing agent in diesel engine tail gas treatment device according to claim 1, it is characterized in that: total amount taken in by the reducing agent that the wherein said object function in optimized mathematical model is target operating condition point, constraints be NOx emission value in the scope of rules and regulations, and under each operating point reducing agent intake less than above-mentioned higher limit; That is: $\begin{array}{cccc}\min & f\left(x\right)& s.t.& \left\{\begin{array}{c}0\≤x\≤ub\\ g\left(x\right)\≤0\end{array}\right.\end{array},$ Wherein, x is the vector of n row 1 row, and each element represents the reducing agent intake of certain target operating condition point; F (x) is object function, i.e. target operating condition point reducing agent intake summation; S.t. writing a Chinese character in simplified form for subjectto, represents constraints; Ub is the vector of n row 1 row, and each component represents reducing agent under corresponding operating mode and takes in higher limit;G (x) is the difference of NOx emission value in tail gas Yu rules and regulations limit value; After constraints ensure that optimization, the amount of leakage of ammonia and NOx discharge are satisfied by rules and regulations.

3. the control method of addition amount of reducing agent in diesel engine tail gas treatment device according to claim 1, it is characterized in that: obtain actual speed and the oil mass data of diesel engine in real time according to diesel engine exhaust gas treatment device, inquiry addition amount of reducing agent optimum MAP, it is thus achieved that the optimal value of addition amount of reducing agent under steady state condition; And with current catalyst temperature for core, carry out transient state correction, it is thus achieved that the final injected volume of reducing agent in diesel engine tail gas treatment device under this transient condition.