CN108488019B

CN108488019B - Double-spark-plug asynchronous ignition method based on optimized lean combustion

Info

Publication number: CN108488019B
Application number: CN201810225867.5A
Authority: CN
Inventors: 李洋涛
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-19
Filing date: 2018-03-19
Publication date: 2020-04-07
Anticipated expiration: 2038-03-19
Also published as: CN108488019A

Abstract

The invention discloses a double-spark-plug asynchronous ignition method based on optimized lean combustion, which comprises a gasoline engine body, wherein the gasoline engine body comprises at least one group of cylinder cover, two intake valves and two exhaust valves are arranged on the cylinder cover, a main spark plug is arranged at the top of the cylinder cover, and a pair of spark plugs is arranged between the two exhaust valves; the asynchronous ignition method comprises the following steps: 1) before the piston reaches the top dead center, the ignition time of the gasoline engine is delayed by 3-7 degrees compared with that of the gasoline engine with the ideal mixing ratio of 1, and a main spark plug is controlled to ignite firstly; 2) when the piston reaches the top dead center, the auxiliary spark plug is controlled to ignite. According to the invention, knocking combustion can be avoided through asynchronous ignition of the double spark plugs, so that the gasoline engine has better working stability and longer service life; meanwhile, the combustion can be more sufficient, the compression negative work and the nitrogen oxide emission are reduced, and the expansion work can effectively act on the piston, so that the efficiency and the power of the gasoline engine are obviously improved.

Description

Double-spark-plug asynchronous ignition method based on optimized lean combustion

Technical Field

The invention relates to the technical field of gasoline engines, in particular to a double-spark-plug asynchronous ignition method based on optimized lean combustion.

Background

The single-spark-plug ignition combustion of homogeneous and lean mixture mainly faces the problem of slow combustion speed, resulting in the reduction of the efficiency and power of the gasoline engine. In order to solve the problem, a method of increasing the ignition advance angle is generally adopted, so that the highest combustion pressure is about 10 degrees after the top dead center (the value is an empirical value of optimal combustion), however, knocking combustion is easy to occur in the method, the pressure before the top dead center is increased, negative work is increased, the highest combustion pressure and the highest temperature are increased, and harmful emission of nitrogen oxides is increased for lean combustion.

A small number of gasoline engines in the market adopt a scheme of simultaneously igniting by double spark plugs, so that the combustion rate can be greatly accelerated to ensure that the power of the gasoline engines is not reduced. But the method is easier to cause the rise of the highest pressure and temperature and the rise of the pressure rise rate, so that the thermal load, the mechanical load, the impact and the vibration of the gasoline engine are increased, and the emission of nitrogen oxides is increased; if ignition is retarded, the problem can be solved, but most of the fuel will burn after moving away from top dead center, resulting in insufficient expansion to optimize gasoline engine efficiency and power.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to solve the problems that the existing gasoline engine is easy to knock, the emission of nitrogen oxides is increased due to insufficient combustion, and the efficiency and the power of the gasoline engine are reduced due to insufficient expansion, and provides an optimized lean combustion-based double-spark-plug asynchronous ignition method, so that knocking combustion can be avoided through the double-spark-plug asynchronous ignition, the gasoline engine has better working stability and longer service life; meanwhile, the combustion can be more sufficient, the compression negative work and the nitrogen oxide emission are reduced, and the expansion work can effectively act on the piston, so that the efficiency and the power of the gasoline engine are obviously improved.

In order to solve the technical problem, the technical scheme adopted by the invention is as follows: a double-spark-plug asynchronous ignition method based on optimized lean combustion comprises a gasoline engine body, wherein the gasoline engine body comprises at least one group of cylinder covers, two intake valves and two exhaust valves are arranged on the cylinder covers, a main spark plug is arranged at the top of each cylinder cover, and the main spark plug is positioned at the central positions of the two intake valves and the two exhaust valves, and the method is characterized in that: a pair of spark plugs is arranged between the two exhaust valves; the asynchronous ignition method comprises the following steps:

1) before the piston reaches the top dead center, the ignition time of the gasoline engine is delayed by 3-7 degrees compared with that of the gasoline engine with the ideal mixing ratio of 1, and a main spark plug is controlled to ignite firstly;

2) when the piston reaches the top dead center, the auxiliary spark plug is controlled to ignite.

Further, the compression ratio of the gasoline engine body is larger than 12.

Further, when the opening of the accelerator is more than 85% and the mixing ratio is 1.15-1.25, the ignition time of the main spark plug is delayed by 3-4 degrees compared with that of a gasoline engine with an ideal mixing ratio of 1;

when the mixing ratio is 1.05-1.15, the ignition time of the main spark plug is delayed by 5-7 degrees compared with that of a gasoline engine with an ideal mixing ratio of 1;

when the opening of the accelerator is less than 85 percent and the mixing ratio is 1.15-1.25, the ignition time of the main spark plug is delayed by 3-4 degrees compared with the ignition time of a gasoline engine with the ideal mixing ratio of 1.

Compared with the prior art, the invention has the following advantages:

1. the main spark plug is ignited first, can control the pressure rise rate and the highest combustion pressure and temperature in the early stage, works softly, and can reduce negative work and reduce the emission of nitrogen oxides.

2. The auxiliary spark plug ignites the tail end gas, so that knocking combustion cannot occur in the cylinder, the later combustion rate is accelerated, lean combustion is optimized, and HC and CO are reduced.

3. The main spark plug and the auxiliary spark plug are matched for use, so that the high efficiency of the lean combustion is realized, and the harmful emission is greatly reduced.

4. The combustion rate can be greatly accelerated to keep the power of the gasoline engine, so that the lean combustion process tends to be more perfect.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a graph comparing the effect of the present invention with the prior art.

In the figure: 1-inlet valve, 2-exhaust valve, 3-main spark plug, 4-auxiliary spark plug.

Detailed Description

The invention will be further explained with reference to the drawings and the embodiments.

Example (b): referring to fig. 1, a double-spark-plug asynchronous ignition method based on optimized lean combustion comprises a gasoline engine body. The gasoline engine body comprises at least one group of cylinder covers, wherein the cylinder covers are provided with two intake valves 1, two exhaust valves 2 and a piston, the top of each cylinder cover is provided with a main spark plug 3, and the main spark plug 3 is positioned at the central positions of the two intake valves 1 and the two exhaust valves 2; a pair of spark plugs 4 is also provided between the two exhaust valves 2.

The asynchronous ignition method comprises the following steps:

1) before the piston reaches the top dead center, the ignition time of the gasoline engine with the ideal mixing ratio of 1 is delayed by 3-7 degrees (crank angle), and the main spark plug 3 is controlled to ignite firstly. Specifically (compared with the ignition timing of a gasoline engine of the ideal mixture ratio 1, and therefore the rotation speed factor is not considered):

when the opening of the accelerator is more than 85% and the mixing ratio is 1.15-1.25, the ignition time of the main spark plug 3 is delayed by 3-4 degrees compared with the ignition time of a gasoline engine with an ideal mixing ratio of 1; (in this case, the ignition timing of the desired mixture ratio is not originally large, and the quasi-lean combustion mixture is relatively lean, so the retard amount is not necessarily too large).

When the mixing ratio is 1.05-1.15, the ignition time of the main spark plug 3 is delayed by 5-7 degrees compared with that of a gasoline engine with the ideal mixing ratio of 1;

when the opening degree of the accelerator is less than 85% and the mixing ratio is 1.15-1.25, the ignition time of the main spark plug 3 is delayed by 3-4 degrees compared with the ignition time of a gasoline engine with an ideal mixing ratio of 1; (in this case, the stoichiometric ratio is large in the ignition advance, but the quasi-lean combustion is leaner, so that the ignition delay is not so large).

2) When the piston reaches the top dead center, the sub-ignition plug 4 is controlled to ignite.

Currently, all conventional gasoline engines are low in compression ratio, use a stoichiometric mixture ratio of 1, ignite with a single spark plug, and similarly, increase in accelerator opening at the same rotation speed decreases the ignition advance angle, and increase in ignition advance angle when the mixture becomes lean because the combustion rate at a high load is fast, and increase in post-combustion easily occurs at a lean mixture ratio, and advance ignition can reduce post-combustion but increases negative compression work, and finally decreases the thermal efficiency. However, the present invention has two ignition sources, and no matter what kind of mixture is used, the negative compression work can be reduced by reducing the ignition time of the main spark plug 3 and the highest combustion temperature and pressure can be controlled, so that the generation of harmful gas nitrogen oxides can be inhibited, sufficient oxygen exists when the lean mixture is used, the emission HC and CO are reduced, the later combustion rate can be completely improved by matching the auxiliary spark plug 4, the post-combustion of fuel is reduced, and the heat efficiency is improved and the emission is reduced.

Specifically, the invention adopts double-spark-plug asynchronous ignition, firstly, the main spark plug 3 at the center of a combustion chamber is used for ignition, the pressure rise rate and the highest combustion pressure and temperature at the early stage can be controlled, and the auxiliary spark plug 4 arranged between two exhaust valves 2 is used for ignition when the piston reaches the top dead center or so, so that on one hand, the tail end gas is quickly ignited to ensure that the gasoline engine does not generate knocking combustion, and on the other hand, because the ignition has a certain ignition delay period, the highest combustion pressure can still be controlled to be about 10 degrees after the top dead center, and the negative combustion power is not increased. Then, due to the simultaneous propulsion of the two flames, the later combustion is greatly accelerated, so that most of fuel is combusted close to a top dead center, and high thermal efficiency is obtained due to the full expansion of the fuel. At the moment, the piston is in a descending acceleration period, so that the pressure in the cylinder does not rise sharply, the process is closer to the isobaric process, and the torque of the gasoline engine is improved.

Referring to fig. 2, a main spark plug 3 is arranged in the center of a combustion chamber, an auxiliary spark plug 4 is arranged between two rows of air valves 2, and ignition of the main spark plug 3 is delayed by 3-7 degrees compared with that of a single spark plug. The pressure of the asynchronous ignition of the double spark plugs is slowly increased in the period before the top dead center of the auxiliary spark plug 4 which is not ignited, so that the negative power area is reduced, the auxiliary spark plug 4 is ignited when the crank angle is at the top dead center, the heat release of the piston after passing the top dead center accelerates the increase of the pressure, but the increase of the highest pressure is not larger than that of the single spark plug when the ignition is performed too early, and the highest pressure and the temperature are not too high.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims

1. A double-spark-plug asynchronous ignition method based on optimized lean combustion comprises a gasoline engine body, wherein the gasoline engine body comprises at least one group of cylinder covers, two intake valves and two exhaust valves are arranged on the cylinder covers, a main spark plug is arranged at the top of each cylinder cover, and the main spark plug is positioned at the central positions of the two intake valves and the two exhaust valves, and the method is characterized in that: a pair of spark plugs is arranged between the two exhaust valves; the asynchronous ignition method comprises the following steps:

2. The double-spark-plug asynchronous ignition method based on the optimized lean combustion as claimed in claim 1, characterized in that: the compression ratio of the gasoline engine body is larger than 12.

3. The double-spark-plug asynchronous ignition method based on the optimized lean combustion as claimed in claim 1, characterized in that:

when the opening of the accelerator is more than 85% and the mixing ratio is 1.15-1.25, the ignition time of the main spark plug is delayed by 3-4 degrees compared with the ignition time of a gasoline engine with an ideal mixing ratio of 1;