Method applied to diesel engine SCR after-treatment system for estimating ammonia coverage rate and input ammonia gas concentration
A technology of ammonia concentration and coverage, applied in chemical statistics, mechanical equipment, exhaust devices, etc., can solve problems such as increasing the cost of SCR system use
Inactive Publication Date: 2019-09-06
BEIHANG UNIV
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Problems solved by technology
In order to obtain the input ammonia concentration, an ammonia concentration sensor can usually be installed at the inlet of the SCR system, but the use of physical sensors will increase the cost of the SCR system; at the same time, compared with the input ammonia concentration, how to obtain accurate ammonia coverage is a problem. Difficult, because there is currently no commercial physical sensor that can accurately obtain this physical quantity
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[0101] Such as Figure 1-11 as shown, figure 1 It is a schematic diagram of the chemical reaction inside the SCR post-treatment system; figure 2 is a schematic diagram of ammonia coverage model values; image 3 is a schematic diagram of ammonia coverage estimates based on UKF; Figure 4 is a schematic diagram of EKF-based estimates of ammonia coverage; Figure 5 is a schematic diagram of the absolute estimation error between the UKF-based ammonia coverage estimate and the model value; Figure 6 is a schematic diagram of the absolute estimation error between the EKF-based ammonia coverage estimate and the model value; Figure 7 is a schematic diagram of inputting ammonia concentration model values; Figure 8 is a schematic diagram of input ammonia concentration estimates based on UKF; Figure 9 is a schematic diagram of the input ammonia concentration estimate based on EKF; Figure 10 is a schematic diagram of the absolute estimation error between the estimated value of...
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The invention discloses a method applied to a diesel engine SCR after-treatmetn system for estimating ammonia coverage rate and input ammonia gas concentration. The method comprises the steps of firstly, establishing a three-order state space model which can reflect the inner dynamics change of the SCR after-treatment system; and secondly, by means of the established three-order state space model,estimating the ammonia coverage rate and the input ammonia gas concentration in the SCR after-treatment system by means of a UKF algorithm. In the method, unscented Kalman filtering realizes a fact that the strong nonlinear system equation of the SCR after-treatment system is suitable for a Kalman filtering system through combination of unscented transformation (UT) and a standard Kalman filtering system. In unscented Kalman filtering, through approximating the probability density distribution of the nonlinear function, the nonlinear change can be simulated so that high integral estimating precision is realized. The method settles a problem of incapability of acquiring the ammonia coverage range by means of a physical sensor and lays a basis for controlling a urea injection closed-loop. The method can accurately estimate the input ammonia gas concentration of the SCR after-treatment system, thereby replacing an inlet ammonia gas concentration sensor and reducing use cost.
Description
technical field [0001] The invention relates to the technical field of automobile exhaust emissions, in particular to a method for estimating ammonia coverage and input ammonia concentration applied to an SCR post-treatment system of a diesel engine. Background technique [0002] In recent years, diesel engines have attracted more and more attention due to their high fuel efficiency and low greenhouse gas emissions. However, due to the high flame temperature of the diesel engine, the N 2 Oxidized to NOx, the emission of nitrogen oxides will lead to ozone depletion, acid rain and photochemical smog, causing harm to the natural environment and human health. Governments around the world have introduced a lot of diesel engine emission restriction regulations accordingly. In order to meet the increasingly stringent emission requirements, it is not enough to study the combustion control strategy alone. The automotive aftertreatment system is becoming more and more important to re...
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Login to View More IPC IPC(8): G16C20/10G16C20/70F01N3/20
CPCF01N3/2066G16C20/10G16C20/70Y02A50/20Y02T10/12
Inventor 杨世春冯松陈飞刘健张正杰
Owner BEIHANG UNIV