Control system and control method for reducing NOx emissions of diesel engine under all working conditions

Abstract

The invention relates to a control system and a control method for reducing NOx emissions of a diesel engine under all working conditions. The control system comprises an engine, an air filter, an air compressor, a turbine coaxially connected with the air compressor, an intake intercooler, an intake manifold, an exhaust manifold, a gamma sensor and an intake tube pressure sensor which are arranged on the exhaust manifold, a coolant temperature sensor, a high-response torque sensor and a high-response rotational speed sensor which are arranged on the engine, an exhaust pipe pressure sensor arranged on the exhaust manifold, a single-chip microcomputer provided with an air-fuel ratio calculation program, an electronic control unit (ECU), a butterfly valve, two EGR valves and an EGR cooler. Corresponding signals are acquired through the sensors and transmitted to the electronic control unit, the electronic control unit judges a working condition according to the corresponding signals, and then the butterfly valve and the two EGR valves are controlled to change an air-fuel ratio. The control system disclosed by the invention is high in control accuracy; a high EGR rate can be realized on the basis of the system; and the purpose of reducing NOx emissions in a range of all working conditions can be achieved by taking the air-fuel ratio as a control object.

Description

technical field [0001] The invention belongs to the emission control technology of internal combustion engines, and in particular relates to a method of reducing the NOx of diesel engines in all working conditions by introducing EGR. x An emission control system, and a control method based on the system with the air-fuel ratio as the control target. Background technique [0002] When the internal combustion engine is working, the ratio of the air mass required for the complete combustion of a certain mass of fuel to the mass of the fuel is called the theoretical air-fuel ratio. The theoretical air-fuel ratio of a diesel engine is 14.3. The choice of air-fuel ratio directly affects the concentration of the mixture, and has a great impact on the performance of the diesel engine such as power, economy and emission. Due to the high viscosity and poor evaporation of diesel oil, the overall air-fuel ratio of the diesel engine is much greater than the theoretical air-fuel ratio. ...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to cause NO x Due to the problem of increased emissions and the inability to achieve a large EGR rate by using high-pressure EGR, a control system and control method for reducing NOx emissions from diesel engines under all operating conditions is proposed. To control the target, achieve a large EGR rate to reduce NO in the full operating range of the diesel engine x purpose of discharge

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