CN101387219B - Direct Injection Engines Using Ignition Chamber Combustion Systems - Google Patents

Abstract

The utility model relates to a direct-injection engine adopting an ignition chamber combustion system, which belongs to the field of engine fuel injection and combustion. The engine is provided with an ignition chamber equipped with a spark plug in the cylinder head, and the injection direction of a fuel nozzle installed in the ignition chamber points to the channel opening connecting the ignition chamber and the main combustion chamber; The injection quantity is equal to the sum of the ignition chamber concentration control quantity and the main injection quantity. In each working cycle, the fuel nozzle injects once or more at an appropriate time according to the working conditions of the engine to form a mixture that is easy to ignite with the spark plug and suitable for flame propagation. The disturbance of the flame injected into the main combustion chamber is beneficial to the rapid diffusion of combustion, so as to accelerate the combustion speed in the cylinder and improve the thermal efficiency of the engine. Reliable ignition and stable and rapid flame propagation can make the engine run smoothly at a lower idle speed, so that the vehicle can produce a more obvious energy-saving effect when running in urban conditions.

Description

Direct Injection Engines Using Ignition Chamber Combustion Systems

technical field

The invention relates to a direct-injection engine adopting an ignition chamber combustion system, which belongs to the fields of engine fuel injection, mixed gas formation and combustion.

Background technique

In-cylinder direct-injection spark ignition engines (such as direct-injection gasoline engines and direct-injection natural gas engines, etc.) using lean combustion strategies have become the current engine combustion field due to their good fuel economy, transient response and HC emissions during cold start. research hotspots. However, due to the use of a larger air-fuel ratio, it also brings problems such as poor ignition stability of the engine, slow flame propagation, and unstable operation. In order to solve the above problems, it is necessary to form a mixed gas with an appropriate concentration that is easy to ignite around the spark plug at the moment of ignition, and at the same time form a lean mixed gas in other areas of the combustion chamber, which is the so-called stratified combustion technology. However, it is very difficult for the existing combustion systems to ensure the formation of a stable stratified mixture under different operating conditions.

Contents of the invention

In order to ensure reliable ignition and improve the stability of flame propagation, further expand the lean combustion range of direct injection ignition engine, improve thermal efficiency, and reduce emissions, the present invention proposes a direct injection engine using an ignition chamber combustion system. Place the spark plug and fuel nozzle in an ignition chamber on the cylinder head. According to the principle that the airflow movement in the cylinder and the pressure in the cylinder have a great influence on the spray shape at different crank angles, the fuel injection is selected at a suitable time to ensure stable and reliable ignition and flame propagation, in order to further expand The lean combustion range of the engine and the acceleration of the combustion speed in the cylinder improve the thermal efficiency of the engine. Reliable ignition and stable and rapid flame propagation can make the engine run smoothly at a lower idle speed, so that the vehicle can produce a more obvious energy-saving effect when running in urban conditions.

The technical solution adopted by the present invention to solve the technical problem is: a direct-injection spark ignition engine adopting an ignition chamber combustion system, an ignition chamber equipped with a spark plug is arranged in the cylinder head, and a fuel nozzle installed in the ignition chamber The injection direction of the fuel nozzle points to the channel port connecting the ignition chamber and the main combustion chamber; the total fuel injection amount of the fuel nozzle in each working cycle is equal to the sum of the ignition chamber concentration control amount and the main injection amount. When the fuel nozzle uses one injection, the The secondary injection is the injection of the ignition chamber concentration control amount. When the fuel nozzle uses more than one injection of fuel, the ignition chamber concentration control amount is completed by one injection, and the main injection amount is completed by at least one injection; Lit liquid or gaseous fuel.

The ignition chamber concentration control volume is injected by the fuel nozzles late in the engine compression stroke. For a four-stroke engine, the main injection quantity is injected by the fuel nozzle in the early stage of the intake stroke or compression stroke after the exhaust valve of the engine is closed. For a two-stroke engine, the main injection quantity is injected by the fuel nozzle early in the compression stroke of the engine.

The guiding ideology of the above-mentioned technical solution is: the pressure in the cylinder and the movement of air flow in the cylinder have a direct impact on the shape and penetration distance of the spray. When the pressure in the cylinder is relatively low (for a general four-stroke engine, the intake stroke and the initial stage of the compression stroke after the exhaust valve is closed; Initially), the spray will have a longer penetration distance. When the pressure in the cylinder is high and there is a strong squeeze flow (related to the volume ratio of the ignition chamber and the main chamber) rushing to the ignition chamber (at the end of the compression stroke), the spray will have a relatively short penetration distance. Based on the above facts, set an ignition chamber on the cylinder head, place the spark plug and fuel nozzle in it, the ignition chamber and the main combustion chamber are connected by a passage; injection. According to the different effects of each injection, it is divided into ignition chamber concentration control injection and main injection. The concentration control injection in the ignition chamber is only performed once per cycle, and the main injection can be performed once or several times according to the needs, and the main injection may not be performed in the idling condition. The main injection quantity changes according to the working conditions, and its function is to meet the load requirements of the working conditions; the concentration control quantity of the ignition chamber is determined according to the amount of fuel in the mixture gas pressed into the ignition chamber, so as to ensure that the fuel injected into the ignition chamber under different working conditions can be The mixed gas that is pressed into the ignition chamber is diffused and atomized to form a mixed gas that is suitable for ignition. After the mixed gas in the ignition chamber is ignited by the spark plug, it is sprayed into the main combustion chamber at a high speed, which has a certain disturbing effect on the mixed gas in the main combustion chamber, which is beneficial to the spread of the flame and accelerated combustion speed, thereby improving thermal efficiency.

From the closing of the exhaust valve to the top dead center of the compression stroke, the fuel is divided into several injections. The main injection is performed when the pressure in the cylinder is low and the airflow in the ignition chamber passage is relatively weak. Because the airflow has little influence on the spray, the fuel enters the main combustion chamber. When the pressure in the cylinder is high and the air flow at the ignition chamber passage is relatively strong, the ignition chamber concentration control quantity injection is carried out. Because the air flow has a great influence on the spray, and the direction of squeeze flow at the passage is opposite to the injection direction, the fuel cannot be ejected from the ignition chamber. By optimizing parameters such as main injection amount, concentration control amount, main injection time, concentration control amount injection time and other parameters to meet the requirements of working conditions, and to keep the concentration of the mixed gas inside the ignition chamber within the range that is easy to ignite. Since the concentration of the mixture in the ignition chamber is in the range of easy ignition, it is easy to form a stable fire nucleus when the spark plug is ignited, thus ensuring the reliable ignition of the engine. During the flame propagation process of the engine, due to the small flow area between the ignition chamber and the main combustion chamber, the flame inside the ignition chamber rushes into the main combustion chamber at a relatively high speed, and ignites the main combustion chamber with a large flame front. The mixed gas speeds up its combustion speed, making the combustion closer to constant volume heat release and improving thermal efficiency.

The beneficial effect of the present invention is: because this direct-injection engine adopts one or more than one fuel injection mode, the total amount of fuel injected in each working cycle is the ignition chamber concentration control amount or plus one or several main injections To ensure that the air-fuel ratio of the mixture in the ignition chamber is within the range that is easy to ignite, so that the ignition is stable and reliable, and the flame spreads quickly and stably. Using the combustion system of the ignition chamber and the fuel injection method matched with it, the design of the main combustion chamber only needs to consider the distribution of the mixture in the main combustion chamber, which reduces the consideration of the concentration of the mixture near the spark plug and reduces the complexity of the design of the main combustion chamber. The degree lays the foundation for a more reasonable combustion of the organization. After the mixed gas in the ignition chamber is ignited, it is sprayed into the main combustion chamber at a high speed, and its disturbing effect is conducive to the rapid diffusion of combustion, which is conducive to further expanding the lean combustion range of the engine, accelerating the combustion speed in the cylinder, and improving the thermal efficiency of the engine. Reliable ignition and stable and rapid flame propagation can make the engine run smoothly at a lower idle speed, so that the vehicle can produce a more obvious energy-saving effect when running in urban conditions.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Figure 1 is a schematic diagram of the basic structure of the engine combustion system.

Figure 2 is a schematic diagram of the main injection at the end of the intake stroke.

Figure 3 is a schematic diagram of the main injection at the beginning of the compression stroke.

Fig. 4 is a schematic diagram of the injection of the concentration control amount in the ignition chamber at the later stage of the compression stroke.

Among the figure: 1, ignition chamber, 2, fuel nozzle, 3, spark plug, 4, main combustion chamber, 5, piston, 6, main jet, 7, concentration control jet of ignition chamber, 8, air flow.

Detailed ways

As shown in Fig. 1, an ignition chamber 1 is arranged on the cylinder head of a direct injection ignition engine, and a spark plug 3 and a fuel nozzle (porous nozzle or swirl nozzle) 2 are placed therein, and the injection direction points to the passage opening of the ignition chamber 1. Combined with the airflow movement in the engine cylinder, one or more injections are performed during the period from the closing of the exhaust valve of the engine to the compression top dead center. By selecting the appropriate injection timing, the injection is performed when the pressure in the cylinder is high and the airflow at the passage of the ignition chamber is relatively strong. The concentration-controlled quantity injection of the ignition chamber makes the fuel stay in the ignition chamber under the action of the airflow, and does not enter the main combustion chamber. When the pressure in the cylinder is low and the air flow at the passage of the ignition chamber is relatively weak, one or more main injections are carried out, and the fuel directly enters the main combustion chamber due to the small effect of the air flow on the jet. In this way, by controlling the amount of fuel injected into the ignition chamber, the concentration of the mixture in the ignition chamber will not change with the change of working conditions, thereby ensuring the stability of ignition.

The main injection is performed when the pressure in the cylinder is low and the airflow from the injection hole to the channel 1 of the ignition chamber is relatively weak, generally in the early stage of the intake stroke and the compression stroke after the exhaust valve of the engine is closed. As shown in Figure 2, when the engine is in the intake stroke, because the pressure in the cylinder is low, the density is low, and the velocity at the passage of the ignition chamber is low, the airflow at the passage of the ignition chamber and inside the ignition chamber is weak, and the main injection is performed at this time The main spray jet 6 is less affected by the air flow and is directly sprayed into the main combustion chamber. Similarly, at the initial stage of compression, the main injection 6 of the main injection can also be directly injected into the main combustion chamber, as shown in FIG. 3 .

When the pressure in the cylinder is high and the air flow at the passage of the ignition chamber is relatively strong, the injection of the concentration control amount in the ignition chamber is carried out, generally at the end of the engine compression stroke. As shown in Figure 4: at the end of the compression stroke, because of the high pressure and density in the cylinder, and the high airflow (squeeze flow) velocity at the passage of the ignition chamber and inside the ignition chamber, the airflow intensity is relatively high. At this time, the injected ignition chamber Concentration control jet 7 is affected by air flow 8, so it cannot be sprayed into the main combustion chamber, but into the ignition chamber, and is rapidly diffused to the entire ignition chamber due to the strong squeeze flow.

According to the requirements of different working conditions, fuel injection can be flexibly organized. The specific injection method used may be one ignition chamber concentration control amount injection, or one ignition chamber concentration control amount injection and at least one main injection.

Figures 1 to 4 take a four-stroke ignition engine as an example. For engines with different valve numbers and two-stroke engines, the above fuel injection method is also applicable, but the ignition chamber, spark plug, and fuel nozzle need to be properly arranged at the cylinder head.

The above-mentioned engine is suitable for burning various fuels, including liquid fuels (such as gasoline, ethanol) and gaseous fuels (such as compressed or liquefied natural gas, liquefied petroleum gas). For different fuels, it is only necessary to make appropriate adjustments to the injection method according to the physical and chemical characteristics of the fuel itself.

Claims (4)

1. direct injection ic engine that adopts ignition chamber burning system, be provided with an igniting chamber (1) that spark plug (3) are housed in cylinder head, an injection direction that is installed on the fuel nozzle (2) in the igniting chamber (1) points to the passway that igniting chamber (1) is connected with main combustion chamber (4); Fuel nozzle (2) equals igniting chamber concentration control amount and main injection amount sum in the total emitted dose of the fuel of each work cycle; Fuel nozzle (2) sprays is to be easy to liquid fuel or the gaseous fuel lighted by spark plug (3); It is characterized in that: when fuel nozzle (2) employing is once sprayed, this time sprayed and is igniting chamber concentration control amount injection (7), when fuel nozzle (2) adopts more than a burner oil, igniting chamber concentration control amount (7) adopts once to spray and finishes, and main injection amount (6) adopts at least once to spray and finishes.

2. according to the direct injection ic engine of the described employing ignition chamber burning system of claim 1, it is characterized in that: described igniting chamber concentration control amount is sprayed in the later stage of engine compresses stroke by fuel nozzle (2).

3. according to the direct injection ic engine of the described employing ignition chamber burning system of claim 1, it is characterized in that: for four stroke engine, described main injection amount (6) is by the aspirating stroke of fuel nozzle (2) after engine exhaust valve is closed or the injection in early stage of compression stroke.

4. according to the direct injection ic engine of the described employing ignition chamber burning system of claim 1, it is characterized in that: for two stroke engine, described main injection amount is sprayed in the early stage of engine compresses stroke by fuel nozzle (2).

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