Model-based NOX emission monitoring method

Abstract

The invention relates to the technical field of aftertreatment of tail gas of automobiles, in particular to a model-based NOX emission monitoring method. The model-based NOX emission monitoring method comprises the following steps: respectively integrating an SCR downstream NOx mass flow rate model calculating value, an SCR downstream NOx actual mass flow rate and an SCR upstream NOx actual mass flow rate by using running time as an integrating range under the circumstance that an engine meets a monitoring enabling condition, wherein the SCR downstream NOx mass flow rate model calculating value can be obtained according to an SCR downstream NOx concentration model calculating value which is obtained by calculating through an SCR chemical reaction kinetic model, the SCR downstream NOx actual mass flow rate is obtained according to an SCR downstream NOx actual concentration value, and the SCR upstream NOx actual mass flow rate is obtained according to an SCR upstream NOx actual concentration value; after integrating for a period of time, calculating conversion efficiency deviation, and judging whether the conversion efficiency deviation is greater than a deviation limiting value or not; and if the conversion efficiency deviation is greater than the deviation limiting value, carrying out excessive emission fault alarming by using an OBD. Stability of NOx emission monitoring is improved, and false errors are reduced.

Description

technical field [0001] The invention relates to the technical field of automobile tail gas treatment, in particular to a model-based NOx emission monitoring method. Background technique [0002] As the problem of air pollution becomes increasingly prominent, developed countries represented by Europe and the United States have enacted stricter and stricter regulations on motor vehicle emission pollution restrictions, effectively limiting the emission of pollutants to the atmosphere. With the upgrading of emission regulations, the accompanying On-Board Diagnostic (OBD) requirements are more comprehensive, and the OBD limits are becoming more and more stringent. The current regulations have clear limits on engine NOx emissions. Selective Catalytic Reduction (SCR for short) technology is commonly used in diesel engine NOx emission control at present to achieve the purpose of reducing NOx emission. The NOx emission of the engine is monitored in real time through the OBD system....

AI Technical Summary

Problems solved by technology

However, with the gradual upgrading of emission regulations, when the original engine emissions are high, the interval between the emission limit value downstream of the SCR box and the conversion efficiency corresponding to the OBD limit value is getting smaller and smaller, which is prone to false alarms.

In addition, due to changes in engine operating conditions, external environment and other factors, the conversion efficiency deviation of the SCR box fluctuates greatly, which is prone to false alarms.

Images