Compression ignition engine and method for realizing low-temperature combustion mode thereof

Abstract

The invention relates to a compression ignition engine and a method for realizing a low-temperature combustion mode thereof. The method comprises the steps of (A) acquiring a first pressure differencebetween a front exhaust pipeline of a pressurization unit and a back air inlet pipeline of the pressurization unit, and a second pressure difference between a back exhaust pipeline of the pressurization unit and a front air inlet pipeline of the pressurization unit; (B) if judging that the first pressure difference is positive, using a high-pressure exhaust gas recirculation mode for introducingan exhaust gas into intake air until low-temperature combustion is realized, and carrying out one of steps C1 or C2 if low-temperature combustion is unrealized when the first pressure difference is reduced to be zero; and if judging that the first pressure difference is negative, directly carrying out one of the steps C1 or C2; (C1) using a low-pressure exhaust gas recirculation mode for introducing the exhaust gas into the intake air until low-temperature combustion is realized, intruding water into the intake air if low-temperature combustion is unrealized when the second pressure differenceis reduced to be zero, and gradually increasing the water introducing amount until low-temperature combustion is realized; and (C2) introducing water into the intake air, and gradually increasing thewater introducing amount until low-temperature combustion is realized.

Description

technical field [0001] The invention relates to the field of internal combustion engines, in particular to a compression ignition engine and a method for realizing a low-temperature combustion mode. Background technique [0002] Traditional diesel engine combustion belongs to the diffusion combustion of spray combustion, relying on the high temperature when the engine piston is compressed to the end to make the mixture spontaneously ignite. Due to the short mixing time of spray and air, the mixture of fuel and air is seriously uneven, and the mixture is divided into a high-temperature over-rich zone and a high-temperature flame zone during combustion. In the high-temperature and over-concentrated area, a large amount of soot will be generated due to lack of oxygen, and part of the soot will be oxidized in the subsequent process. Oxygen is sufficient in the high-temperature flame zone and the temperature can reach 2200K, which eventually leads to a large amount of NO x gene...

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Problems solved by technology

[0005] 2. The operating load of the low temperature combustion mode is limited

[0006] There are two reasons why the low-temperature combustion mode is difficult to expand the operating load on the actual engine: (1) With the increase of the load, on the one hand, the fuel entering the cylinder increases. In order to ensure the combustion efficiency, too much exhaust gas is theoretically not allowed to enter the cylinder On the other hand, the pressure of the engine exhaust pipe and the pressure of the intake pipe gradually decrease, and the high-pressure exhaust gas recirculation gradually fails to introduce exhaust gas, while the simple use of low-pressure exhaust gas recirculation will cause the exhaust back pressure to rise, and the engine fuel The economy is reduced, so a large proportion of EGR cannot be introduced; (2) As the engine load increases, the energy entering the cylinder increases, the temperature in the cylinder continues to rise, and the combustion boundary temperature rises, and at the same time, it is impossible to introduce sufficient exhaust gas dilution The ignition delay period of air and diesel is too short, and the fuel is not enough to mix with fresh air. The relatively high equivalent in the combustion process will pass through the soot generation area, and it is easier to reach NO x generation area, it is difficult to achieve soot and NO x low emissions

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