A closed-loop control system of internal combustion engine nitrogen oxide emission based on in-cylinder ion current and urea injection

Abstract

The invention discloses an in-cylinder ion current and urea injection type closed-loop control system for nitrogen oxide emission of an internal combustion engine. The in-cylinder ion current and ureainjection type closed-loop control system comprises a urea box, a high-temperature water pipe, a heating control valve, a liquid level and temperature sensor, a high-pressure urea pump, a high-pressure urea common rail, a urea direct injection spraying nozzle, a machine body of the internal combustion engine, an air intake manifold, an exhaust manifold, a nitrogen oxide sensor, an ion current sensor, an ion current signal processing device and a closed-loop controller. According to the in-cylinder ion current and urea injection type closed-loop control system disclosed by the invention, the capability of an emission property of the internal combustion engine is remarkably improved and a crystallization phenomenon is effectively avoided in a urea injection process; and the injection amountof urea is accurately optimized so that extremely high inhibition on the nitrogen oxide emission is realized.

Description

technical field [0001] The invention belongs to the technical field of internal combustion engines, and relates to the related field of realizing the emission control of nitrogen oxides of internal combustion engines by using urea injection, in particular to a closed-loop control system of nitrogen oxides emission of internal combustion engines using in-cylinder ion current and urea injection. Background technique [0002] The problem of air pollution is a major problem in my country at present. Vehicle exhaust emissions are one of the important causes of air pollution. According to the proportion data of various pollution sources released by the Ministry of Environmental Protection of China, vehicle exhaust emissions account for 22% of the total emissions. Based on the above background, the Chinese government has continued to formulate increasingly stringent vehicle exhaust emission standards to further control pollutant emissions. Among the pollutants emitted by motor vehi...

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Problems solved by technology

At present, the urea nozzle is mainly arranged in the exhaust main pipe in the automobile industry. This method has many shortcomings: 1. The temperature in the exhaust pipe under cold start or frequent start and stop conditions is insufficient, which cannot provide sufficient heat for the pyrolysis of urea solution and ammonia reduction reaction. Sufficient heat will lead to a serious decline in the ability to control nitrogen oxide emissions. The emission of nitrogen oxides can exceed the legal standard by several times, and the unpyrolyzed and oxidized urea and ammonia will escape to the atmosphere through the exhaust pipe, causing serious secondary pollution. Pollution; 2. The overall pipeline layout is too long, resulting in frequent crystallization of urea solution during use, which seriously affects the satisfaction of vehicle users, causing them to give up filling urea solution and use other liquids to avoid on-board diagnostic systems 3. Insufficient control accuracy, the injection volume of urea solution cannot meet the requirements of nitrogen oxide emission control, and it is usually necessary to install an oxidizer at the rear end of the exhaust pipe to reduce subsequent unconventional emissions , greatly increasing the cost of system production and use; 4. The control of urea injection volume depends on the nitrogen oxide generation model, which lacks a direct feedback signal for the concentration of nitrogen oxides in the cylinder, and the accuracy of urea injection volume control is poor; 5. The urea solution injection process is far from The place where nitrogen oxides are generated (combustion chamber), resulting in obvious hysteresis in the control process, the control performance of nitrogen oxides is reduced, and the transient regulation ability is very poor, and the reduction rate of nitrogen oxides is usually only about 70%

[0004] Although most of the diesel engines used in commercial vehicles need to use catalytic reduction (SCR) technology, due to the high cost of using this technology, large installation volume, and frequent crystallization and blockage problems, the utilization rate in the actual work process has been insufficient for a long time. In 2018, the environmental protection According to the pass rate of vehicle urea sampling inspection announced by the Ministry of National Defense, nearly 70% of the vehicle urea is unqualified, and the compliance rate is only 31.25%. From the statistics of pollutant emissions by vehicle type, diesel vehicles emit nitrogen oxides. 70% of total NOx emissions

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