阅读说明：本技术 一种柴油微喷引燃天然气发动机的喷射方法 (Injection method for diesel micro-injection ignition natural gas engine ) 是由 周杨 徐敏 胡晶晶 张娜 龚远飞 赵晨瑞 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,且第二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 method for injecting natural gas by diesel micro-injection includes such steps as injecting diesel oil in two stages in the same piston cycle under the condition of constant total diesel oil injection quantity, injecting diesel oil in the first stage earlier than in the second stage, and injecting diesel oil in the second stage N times, where N is greater 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 diesel micro-injection ignition natural gas engine injection method is characterized in that:

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 second stage is carried out in N times, wherein N is more than or equal to 1.

2. the injection method of the diesel micro-injection pilot natural gas engine according to claim 1, characterized in that: the time of the first stage injection is any time when the piston moves to be within 15-5 degrees CA before the top dead center, the time of the ith injection in the second stage is any time when the piston moves to be within 90 degrees CA after the top dead center, and the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 or 2 … N.

3. the injection method of a diesel micro-injection pilot natural gas engine according to claim 2, characterized in that: in the second stage, the time of the ith injection is any time from the time when the piston moves to 2 degrees CA before the top dead center to the time when the piston moves to 90 degrees CA after the top dead center.

4. An 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 second 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 an injection method of a diesel micro-injection ignition natural gas engine, which is suitable for reducing the heat load of an oil nozzle, improving the reliability of an oil injector and prolonging the service life of the oil injector.

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:

an injection method for igniting a natural gas engine by diesel micro-injection 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 second stage is carried out in N times, wherein N is more than or equal to 1.

The time of the first stage injection is any time when the piston moves to be within 15-5 degrees CA before the top dead center, the time of the ith injection in the second stage is any time when the piston moves to be within 90 degrees CA after the top dead center, and the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 or 2 … N.

In the second stage, the time of the ith injection is any time from the time when the piston moves to 2 degrees CA before the top dead center to the time when the piston moves to 90 degrees CA after 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 second 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 an 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 second 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. in the injection method of the diesel micro-injection ignition natural gas engine, the ith injection time in the second stage is any time from the piston moving to 2 degrees CA before the top dead center to the piston moving to 90 degrees CA after the top dead center, along with the delay of the ith injection time, the ignition strength of the mixed gas 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 present invention reduces the emission of nitrogen oxides.

drawings

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

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.

Detailed Description

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

Referring to fig. 1, an injection method of a diesel micro-injection ignition natural gas engine is as follows: 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 second stage is carried out in N times, wherein N is more than or equal to 1.

The time of the first stage injection is any time when the piston moves to be within 15-5 degrees CA before the top dead center, the time of the ith injection in the second stage is any time when the piston moves to be within 90 degrees CA after the top dead center, and the time of the ith injection is earlier than the time of the (i + 1) th injection, wherein i is 1 or 2 … N.

In the second stage, the time of the ith injection is any time from the time when the piston moves to 2 degrees CA before the top dead center to the time when the piston moves to 90 degrees CA after 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 second 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 relates to an injection method of a diesel micro-injection ignition natural gas engine, which is an injection method for implementing late injection multiple 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.