Low-pressure exhaust gas recirculation system for diesel engine

Abstract

The invention provides a low-pressure exhaust gas recirculation system for a diesel engine. In the system, exhaust gas is led out after a turbine unit and before post-treatment equipment, and is cooled through a cooler; the cooled exhaust gas is mixed with high-pressure fresh air flowing out after a gas compressor in a dedicated jet device; and mixed gas of the fresh air and the exhaust gas flows through an intercooler and enters a combustion chamber of an engine. Compared with the conventional high-pressure EGR ( Exhaust Gas Recirculation) system and low-pressure EGR system, the low-pressure exhaust gas recirculation system has the characteristics of more uniform EGR distribution, good transient (dynamic) character, reduced cooling requirement, damage prevention for the gas compressor, post-treatment burden reduction and service life prolonging of the post-treatment equipment.

Description

Technical field [0001] The invention relates to an engine air intake system, particularly a recirculation system in which diesel engine exhaust gas is added to high-pressure fresh air. Background technique [0002] The internal combustion engine implements exhaust gas recirculation (EGR) as a control diesel engine NO X Effective emission measures have been widely adopted. The implementation effect of EGR is often affected by the EGR system and EGR implementation mode, and the implementation effect of EGR directly affects NO X Emission control effect. [0003] The high-pressure EGR system commonly used in diesel engines has some problems, such as: 1. The high EGR temperature directly affects the charging efficiency and emissions of the diesel engine. In order to cool the EGR, a more complicated cooling system is required; 2. High pressure The maximum EGR rate of the EGR system is affected by the pressure difference between the upstream pressure of the turbine and the pressure downst...

AI Technical Summary

Problems solved by technology

[0003] There are some problems in the high-pressure EGR system commonly used on diesel engines, such as: 1. The high temperature of EGR directly affects the charging efficiency and emission of diesel engines. In order to cool the EGR, a more complicated cooling system is required; 2. High pressure The maximum EGR rate of the EGR system is affected by the pressure difference between the upstream of the turbine and the downstream of the compressor, and the EGR rate adjustment range is limited

[0004] Although there are some low-pressure EGR systems on the market that have solved some of the above-mentioned problems of the high-pressure EGR system, some new problems have also been produced correspondingly, such as the low-pressure EGR system proposed in the patent [200810196308.2] has the following problems: 1. Although the gas is drawn from the downstream of the after-treatment equipment, there are still water vapor, unburned hydrocarbons (HC), particulate matter (soot) and other combustion products in the exhaust, and these substances are bound to have adverse effects on the compressor , such as: the compressor blades are corroded, the particles in the exhaust have physical impact on the high-speed moving blades (the maximum speed of the compressor is above 100,000 rpm), etc.; The downstream of the after-processor is drawn, compared with the engine using the high-pressure EGR system, the exhaust gas flow through the engine after-treatment equipment is increased, which will inevitably increase the burden on the after-treatment equipment and increase the cost of the after-treatment equipment; 3. Since EGR is drawn out from the post-processing equipment, the route that EGR passes becomes longer, and the transient characteristics of EGR rate adjustment become worse.

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