Method for synchronously optimizing ammonia injection quantity and ammonia covering rate of diesel engine Urea-SCR system

Abstract

The invention provides a method for synchronously optimizing the ammonia injection quantity and the ammonia covering rate of a diesel engine Urea-SCR system. The method comprises the following steps that 1, a system tri-state nonlinear model is set up; 1-1, a system tri-state model is set up based on a main chemical reaction and rate equation; 1-2, NOx and NH3 concentration changes are taken as the quasi-stable state, only ammonia covering rate dynamic performance is taken as the unique state, and a one-state reduced-order model is set up; 2, a genetic algorithm is adopted in Matlab so that the error of the predicted values of NOx and NH3 concentrations in tail gas of an outlet of a catalyzer and actual measurement data can be minimum, and model parameters are obtained through recognition;3, the recognized model parameters are used for the optimization process of an NSGA-II algorithm, the best optimal solution is selected according to the limit value requirement, and the optimized urea feed rate and ammonia covering rate, the maximum NOx conversion efficiency and the ammonia storage quantity are obtained; and 4, simulation is carried out, and an engine full work condition optimization MAP is set up.

Description

technical field [0001] The invention belongs to the field of engines, and in particular relates to a synchronous optimization method for ammonia injection quantity and ammonia coverage rate of a diesel engine Urea-SCR system. technical background [0002] Severe air pollution problems and increasingly stringent emission regulations have forced people to pay more and more attention to advanced vehicle exhaust emission control technologies. Selective catalytic reduction (SCR) technology is widely used in medium and heavy-duty diesel vehicles due to its advantages of high efficiency, high selectivity, high economy and sulfur tolerance. x emission control. In June 2018, the latest "Heavy-duty Diesel Vehicle Emission Limits and Measurement Methods (China Phase VI)" (referred to as China VI) emission regulations require the adoption of a new test cycle - Worldwide Harmonized Steady Cycle (Worldwide Harmonized Steady Cycle) Cycle, WHSC) and World Harmonized Transient Cycle (WHTC)...

AI Technical Summary

Problems solved by technology

Some current researches use the NSGA-II algorithm to optimize the Urea-SCR system of diesel engines, and generally adopt data-based modeling methods, such as modeling methods using support vector machines and genetic algorithms. Since the ammonia coverage rate / ammonia storage capacity is not yet available. Measured directly by equipment or sensors, this data-based modeling approach cannot establish optimal ammonia coverage / ammonia storage to correlate engine operating conditions

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