阅读说明：本技术 一种柴油微喷引燃天然气发动机的多段喷射方法 (multi-stage injection method for diesel micro-injection ignition natural gas engine ) 是由 胡晶晶 徐敏 周杨 张娜 赵晨瑞 龚远飞 于 2019-07-25 设计创作，主要内容包括：一种柴油微喷引燃天然气发动机的多段喷射方法为进行柴油微喷引燃天然气时,在总喷射柴油量不变的条件下,同一活塞工作循环内分两阶段喷射柴油,第一阶段喷射的时刻早于第二阶段喷射的时刻,且第一阶段中的柴油喷射分N次进行,其中,N≥1。该方法降低了喷油嘴的热负荷,提高了喷油器的可靠性和使用寿命。(a multi-stage injection method of a diesel micro-injection ignition natural gas engine is characterized in that when diesel micro-injection ignition natural gas is carried out, under the condition that the total injection diesel quantity is not changed, diesel is injected in two stages in the same piston working cycle, the injection time of the first stage is earlier than that of the second stage, and the diesel injection in the first stage is carried out in N times, wherein N is more than or equal to 1. The method reduces the heat load of the oil nozzle, improves the reliability of the oil injector and prolongs the service life of the oil injector.)

1. A multi-stage injection method for a diesel micro-injection ignition natural gas engine is characterized by comprising the following steps:

The spraying method comprises the following steps: when the diesel micro-injection is carried out to ignite the natural gas, under the condition that the total injection diesel quantity is not changed, the diesel is injected in two stages in the same piston working cycle, the injection time of the first stage is earlier than that of the second stage, and the diesel injection in the first stage is carried out for N times, wherein N is more than or equal to 1.

2. the multi-stage injection method of the diesel micro-injection pilot natural gas engine according to claim 1, characterized in that: in the first stage, the time of the ith injection is any time from the movement of the piston to the temperature within 100-20 ℃ A before the top dead center, the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 and 2 … N, and the time of the second stage injection is any time from the movement of the piston to the temperature within 15-5 ℃ A before the top dead center.

3. the multi-stage injection method of the diesel micro-injection pilot natural gas engine according to claim 2, characterized in that: in the first stage, the ith injection time is any time within 100-60 ℃ A before the piston moves to the top dead center.

4. A multi-stage injection method of a diesel micro-injection pilot natural gas engine according to any one of claims 1-3, characterized in that: the total diesel injection amount in the first stage is equal to the total diesel injection amount in the second stage, and the ith diesel injection amount in the first stage is equal to the (i + 1) th diesel injection amount.

Technical Field

the invention belongs to the technical field of automobile engines, and particularly relates to a multi-stage injection method for a diesel micro-injection ignition natural gas engine, which is suitable for reducing the heat load of an oil nozzle.

background

In order to solve the problem, the pilot oil quantity needs to be greatly reduced, even a micro-injection ignition method is adopted, the ignition strength of gas mixture in a cylinder is reduced, the combustion in the cylinder is slowed down, and the emission of products is reduced.

chinese patent: the invention of application publication No. CN109209656A, application publication No. 2019, 01.15.A method for organizing combustion of a natural gas engine with multiple injection, low-pressure gas supply of a precombustion chamber and diesel oil micro-injection ignition is disclosed, in which a one-way gas supply valve injects natural gas into the precombustion chamber in an intake stroke, a high-pressure natural gas injection valve directly injects natural gas into the cylinder for multiple times, mixed gas stratification with different concentration gradients is formed in the cylinder under different engine loads, the precombustion chamber is positioned in the middle of a cylinder cover, an oil injector injects a small amount of diesel oil into the precombustion chamber near a compression top dead center, the diesel oil self-ignites and ignites the mixed gas in the precombustion chamber, and high-temperature fuel gas is sprayed from the precombustion chamber to ignite the mixed gas in the cylinder, so that the natural gas engine under different working conditions can reliably ignite, has high efficiency and low emission combustion, although the method, however, in the method, the micro-injection diesel oil has poor cooling effect on the oil nozzle, so that the heat load of the oil nozzle is higher, the reliability of the oil injector is reduced, and the service life of the oil injector is prolonged. Therefore, there is a problem that the thermal load of the oil jet is high.

Disclosure of Invention

The invention aims to solve the problem of high thermal load of an oil nozzle in the prior art, and provides an injection method of a diesel micro-injection ignition natural gas engine, which can reduce the thermal load of the oil nozzle.

in order to achieve the above purpose, the invention provides the following technical scheme:

a multi-stage injection method for a diesel micro-injection ignition natural gas engine comprises the following steps: when the diesel micro-injection is carried out to ignite the natural gas, under the condition that the total injection diesel quantity is not changed, the diesel is injected in two stages in the same piston working cycle, the injection time of the first stage is earlier than that of the second stage, and the diesel injection in the first stage is carried out for N times, wherein N is more than or equal to 1.

In the first stage, the time of the ith injection is any time from the movement of the piston to the position within 100-20 CA degrees before the top dead center, the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 and 2 … N, and the time of the second stage injection is any time from the movement of the piston to the position within 15-5 CA degrees before the top dead center.

In the first stage, the ith injection is performed at any time within a range of 100-60 CA before the piston moves to the top dead center.

the total diesel injection amount in the first stage is equal to the total diesel injection amount in the second stage, and the ith diesel injection amount in the first stage is equal to the (i + 1) th diesel injection amount.

compared with the prior art, the invention has the beneficial effects that:

1. the invention relates to a multi-stage injection method of a diesel micro-injection ignition natural gas engine, which is characterized in that when diesel micro-injection ignition natural gas is carried out, diesel is injected in two stages in the same piston working cycle under the condition that the total injection diesel quantity is not changed, the injection time of the first stage is earlier than that of the second stage, and the diesel injection in the first stage is carried out for N times, wherein N is more than or equal to 1, and the diesel is injected for multiple times to cool an oil nozzle, so that the heat load of the oil nozzle is reduced, the reliability of an oil injector is improved, and the service life of the oil injector is prolonged. Therefore, the invention reduces the heat load of the oil nozzle, improves the reliability of the oil injector and prolongs the service life of the oil injector.

2. according to the multi-stage injection method of the diesel micro-injection ignition natural gas engine, the ith injection time in the first stage is any time when the piston moves to 100-60 CA degrees before the top dead center, along with the advance of the ith injection time, the ignition strength of the gas mixture in the cylinder is reduced, the combustion rate is slowed down, and the highest combustion temperature in the cylinder is reduced, so that the emission of nitrogen oxides is reduced. Therefore, the invention reduces the emission of nitrogen oxides.

drawings

FIG. 1 is a schematic diagram of a multi-stage injection method of a diesel micro-injection pilot natural gas engine.

fig. 2 shows the nox emission for different engine loads as a function of the i-th injection time.

Fig. 3 shows the variation of the amount of hydrocarbons discharged with the i-th injection timing for different engine loads.

Fig. 4 shows the amount of carbon oxides emitted as a function of the i-th injection timing for different engine loads.

Detailed Description

The present invention will be further described with reference to the following embodiments.

Referring to fig. 1, a multi-stage injection method of a diesel micro-injection ignition natural gas engine comprises the following steps: when the diesel micro-injection is carried out to ignite the natural gas, under the condition that the total injection diesel quantity is not changed, the diesel is injected in two stages in the same piston working cycle, the injection time of the first stage is earlier than that of the second stage, and the diesel injection in the first stage is carried out for N times, wherein N is more than or equal to 1.

In the first stage, the time of the ith injection is any time from the movement of the piston to the position within 100-20 CA degrees before the top dead center, the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 and 2 … N, and the time of the second stage injection is any time from the movement of the piston to the position within 15-5 CA degrees before the top dead center.

in the first stage, the ith injection is performed at any time within a range of 100-60 CA before the piston moves to the top dead center.

The total diesel injection amount in the first stage is equal to the total diesel injection amount in the second stage, and the ith diesel injection amount in the first stage is equal to the (i + 1) th diesel injection amount.

the principle of the invention is illustrated as follows:

The method mainly aims to directly increase the fuel injection quantity, strengthen the cooling effect on the fuel injector and reduce the heat load of the fuel injector at present, but the method sacrifices the advantages of flexible combustion in a micro-injection ignition mode and reduction of product emission, and brings adverse effects on the reliability and aftertreatment of an engine.

The invention discloses a multi-stage injection method of a diesel micro-injection ignition natural gas engine, which is an injection method for implementing early injection and multi-injection aiming at fuel oil.

Injection timing: the injection time is determined according to the working condition of the engine and is expressed by the crank angle of the engine.

Top dead center: the top dead center is the position of the piston when the piston moves to the maximum distance from the center of the crankshaft.