JP2009185752A - Premixed compression ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a premixed compression ignition internal combustion engine efficiently properly using two kinds of fuels having different ignitability according to the remaining amount thereof. <P>SOLUTION: This premixed compression ignition internal combustion engine 1 includes: an intake port 4 guiding an air-fuel mixture to a combustion chamber 2; a first injector 6 injecting a first fuel to the intake port 4; and a second injector 7 directly injecting a second fuel having ignitability lower than that of the first fuel to the combustion chamber 2, and a fuel mixture containing fuel supplied from both the injectors 6, 7 is compressed and self-ignited. A control means 8 is provided so that when the remaining amount of the first fuel is smaller than the remaining amount of the second fuel, the supply rate of the second fuel is increased and also the injection timing of the second fuel is delayed, and when the remaining amount of the second fuel is smaller than the remaining amount of the first fuel, the supply rate of the second fuel is reduced and also the injection timing of the second fuel is advanced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a premixed compression ignition internal combustion engine.

  In recent years, an oxygen-containing gas such as air and a fuel such as gasoline are premixed at an intake port, and the obtained air-fuel mixture is introduced into a combustion chamber and compressed, whereby the fuel is self-ignited and premixed compression ignition internal combustion Institutions are being considered. In the premixed compression ignition internal combustion engine, since the lean air-fuel mixture is compressed at a high compression ratio and self-ignited and combusted, all the fuel supplied to the combustion chamber burns almost simultaneously. As a result, according to the premixed compression ignition internal combustion engine, fuel consumption per predetermined time can be reduced to achieve high thermal efficiency, while harmful substances in the exhaust gas can be reduced.

  However, since the premixed compression ignition internal combustion engine performs ignition of the air-fuel mixture by self-ignition, it is difficult to arbitrarily control the ignition timing, which causes abnormal combustion such as knocking or misfire. is there. In order to adjust the ignition timing, a control method for changing the intake air temperature or recirculating the exhaust gas after combustion to the intake air is known. In such a control method, the premixed compression ignition internal combustion engine There is a problem that it is difficult to cope with a sudden change in required load.

  In view of this, the first fuel having high ignitability and the second fuel having low ignitability are provided, and the supply amount of the first fuel and the second fuel is changed according to the required load. A mixed compression ignition internal combustion engine is known (see Patent Document 1).

  According to the premixed compression ignition internal combustion engine including the first fuel and the second fuel, by changing the supply amount of the first fuel and the supply amount of the second fuel according to the required load, It is considered that the ignition timing can be arbitrarily controlled, and that it is possible to easily cope with a sudden change in the required load of the internal combustion engine in a wide range.

However, in the premixed compression ignition internal combustion engine, the ratio between the first fuel supply amount and the second fuel supply amount is determined by the required load, and there is no means for avoiding this ratio. If either one of the fuel and the second fuel is supplied in a large amount and the remaining amount of either one is exhausted, the operation may not be continued.
JP 2004-28047 A JP 2007-187112 A

  In view of such circumstances, an object of the present invention is to provide a premixed compression ignition internal combustion engine that can efficiently use two types of fuels having different ignitability in accordance with their respective remaining amounts.

  The present invention provides an intake port for guiding an air-fuel mixture to a combustion chamber, a first injector for injecting a first fuel into the intake port, and a second fuel having a lower ignitability than the first fuel. This premise is a premixed compression ignition internal combustion engine that includes a second injector that directly injects into a combustion chamber and compresses and self-ignites a fuel mixture containing fuel supplied from both injectors. The applicant has already proposed such a premixed compression ignition internal combustion engine (see Patent Document 2).

  In the premixed compression ignition internal combustion engine, when the remaining amount of the first fuel is smaller than the remaining amount of the second fuel, the supply ratio of the second fuel is increased. At the same time, the injection timing of the second fuel is delayed, and when the remaining amount of the second fuel is smaller than the remaining amount of the first fuel, the supply ratio of the second fuel is decreased. And a control means for advancing the injection timing of the second fuel.

  In the premixed compression ignition internal combustion engine of the present invention, delaying the timing of directly injecting the second fuel into the combustion chamber by the second injector increases the supply ratio of the first fuel. Has the same effect. Therefore, in the premixed compression ignition internal combustion engine of the present invention, when the remaining amount of the first fuel is smaller than the remaining amount of the second fuel, the supply ratio of the second fuel is increased. At the same time, by delaying the injection timing of the second fuel, it is possible to suppress the consumption of the first fuel while obtaining the same effect as the case of consuming the first fuel.

  Further, in the premixed compression ignition internal combustion engine of the present invention, by using the second injector to advance the timing of directly injecting the second fuel into the combustion chamber, the supply ratio of the second fuel is increased. Has the same effect as Therefore, in the premixed compression ignition internal combustion engine of the present invention, when the remaining amount of the second fuel is smaller than the remaining amount of the first fuel, the supply ratio of the second fuel is decreased. At the same time, by accelerating the injection timing of the second fuel, it is possible to suppress the consumption of the second fuel while obtaining the same effect as the case of consuming the second fuel.

  Therefore, according to the present invention, the first fuel having a relatively high ignitability and the second fuel having a relatively low ignitability can be efficiently used in accordance with the respective remaining amounts. .

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a system configuration diagram showing the main configuration of the premixed compression internal combustion engine of the present embodiment.

  As shown in FIG. 1, a premixed compression internal combustion engine 1 of this embodiment includes a cylinder 2 as a combustion chamber. The cylinder 2 includes a piston 3 therein and an intake valve provided at the top (cylinder head). An intake port 4 that communicates with the cylinder 2 via a not shown (not shown) and an exhaust port 5 that communicates with the cylinder 2 via an exhaust valve (not shown) provided at the top are provided. The intake port 4 is provided with a first injector 6 for injecting a first fuel, and a second injector 7 for injecting a second fuel is provided at the center of the top of the cylinder 2. The premixed compression internal combustion engine 1 includes a control device 8 that controls the supply amount and injection timing of each fuel by the injectors 6 and 7.

  In the premixed compression ignition internal combustion engine 1 of the present embodiment, the first fuel is a fuel having a relatively high ignitability, and for example, a fuel having a research octane number of 70 or less can be used. Examples of such a first fuel include heptane, dimethyl ether, diethyl ether and the like.

  The second fuel is a fuel having relatively low ignitability, and examples thereof include alcohols such as ethanol. As said ethanol, the bioethanol obtained by fermentation and distillation of plant substances, for example, agricultural products, such as sugarcane and corn, can be used. Since the plant substance as a raw material has already absorbed carbon dioxide, the amount of carbon dioxide emitted by the plant itself is the same even when ethanol obtained from the plant substance is burned. Equal to the amount of carbon dioxide absorbed. That is, it is possible to obtain a so-called carbon neutral effect in which the total amount of carbon dioxide emission is theoretically zero. Therefore, by using the bioethanol as fuel, it is possible to reduce carbon dioxide emissions and contribute to the prevention of global warming.

  In the premixed compression ignition internal combustion engine 1 of the present embodiment, heptane, for example, is injected as the first fuel into the intake port 4 by the first injector 6, and ethanol, for example, is used as the second fuel as the second injector 7. To directly inject into the cylinder 2. By doing so, an air-fuel mixture of the first fuel, the second fuel, and air is formed in the cylinder 2.

  The air-fuel mixture is self-ignited by being compressed by the piston 3 in the cylinder 2. At this time, the first fuel having a high ignitability has a low temperature oxidation reaction heat (cold flame), and promotes ignition by causing a temperature rise in the combustion chamber before the main combustion. On the other hand, the second fuel having low ignitability suppresses the low-temperature oxidation reaction.

  Therefore, in the premixed compression ignition internal combustion engine 1, the control device 8 can control the supply amount of the first fuel and the second fuel to cope with a change in the required load. Specifically, the control by the control device 8 increases the supply amount of the first fuel when the load is low, and increases the supply amount of the second fuel when the load is high.

  Further, the control by the control device 8 may use only the first fuel at a low load, and increase the usage ratio of the second fuel as the load increases. By doing so, the control device 8 responds to a change in the required load by a simple control that only changes the supply ratio of the second fuel without changing the supply amount of the first fuel. be able to.

  By the way, in the premixed compression ignition internal combustion engine 1, the first fuel is preliminarily mixed with air in the intake port 4 and then guided into the cylinder 2, so that it is uniformly distributed in the cylinder 2. On the other hand, since the second fuel is directly injected into the cylinder 2, a distribution is formed such that the concentration increases toward the center along the axis of the cylinder 2 and decreases toward the peripheral edge from the axis. The extent to which the second fuel diffuses from the axis of the cylinder 2 toward the peripheral edge is related to the injection timing of the second fuel. The earlier the injection timing, the farther the diffusion, and the slower the injection timing, the less the diffusion. Become.

  As a result, when the air-fuel mixture is compressed by the piston 3 in the cylinder 2 and self-ignited, the portion where the concentration of the second fuel is leaner becomes higher, and the portion with the highest temperature is ignited first. To do. And after that, it ignites in order from a part with high temperature.

  Therefore, in the premixed compression ignition internal combustion engine 1, the control device 8 controls the injection timing of the second fuel to delay the injection timing, thereby increasing the supply ratio of the first fuel. The effect of can be obtained. Further, in the premixed compression ignition internal combustion engine 1, the control device 8 controls the injection timing of the second fuel to advance the injection timing, thereby increasing the supply ratio of the second fuel. The effect of can be obtained.

  In the premixed compression ignition internal combustion engine 1, the control device 8 controls the injection timing of the second fuel as described above to selectively use the first fuel and the second fuel. Next, the proper use of the first fuel and the second fuel will be described.

  First, in the premixed compression ignition internal combustion engine 1, when the remaining amount of the first fuel is smaller than the remaining amount of the second fuel, the control device 8 supplies the second fuel. Is increased, and the injection timing of the second fuel is delayed. If it does in this way, while the supply amount of the said 2nd fuel will increase, while obtaining the same effect as the case where the said 1st fuel is consumed, consumption of this 1st fuel can be suppressed.

  Further, in the premixed compression ignition internal combustion engine 1, when the remaining amount of the second fuel is smaller than the remaining amount of the first fuel, the control device 8 supplies the second fuel. , And the second fuel injection timing is advanced. In this way, it is possible to obtain the same effect as the case where the second fuel is consumed despite the decrease in the supply amount of the second fuel, and to suppress the consumption of the second fuel. it can.

1 is a system configuration diagram showing a main configuration in a configuration example of a premixed compression internal combustion engine of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Premixed compression ignition internal combustion engine, 2 ... Combustion chamber, 4 ... Intake port, 6 ... 1st injector, 7 ... 2nd injector, 8 ... Control means.

Claims (1)

An intake port that guides the air-fuel mixture to the combustion chamber, a first injector that injects the first fuel into the intake port, and a second fuel that is less ignitable than the first fuel is directly supplied to the combustion chamber. A premixed compression ignition internal combustion engine comprising a second injector for injection, and compressing and self-igniting a fuel mixture containing fuel supplied from both injectors;
When the remaining amount of the first fuel is smaller than the remaining amount of the second fuel, the supply ratio of the second fuel is increased and the injection timing of the second fuel is delayed, When the remaining amount of the second fuel is smaller than the remaining amount of the first fuel, the control to reduce the supply ratio of the second fuel and advance the injection timing of the second fuel A premixed compression ignition internal combustion engine comprising means.

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