JPH0921362A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed a reformed gas sufficiently to the quenching layer of the combustion chamber of an internal combustion engine which uses a hydrocarbon as the fuel, by making the reformed gas collide directly with the inner wall of a cylinder, and distributing the main fuel at the center of the cylinder and the reformed gas around the center of the cylinder respectively. SOLUTION: Together with the starting of an engine, a control unit 10 opens a solenoid valve 83, delivers a fuel to the catalyst 71 of a reformer 7, and a heater 72 heats the catalyst 71. An air amount control unit 82 delivers a specific amount of air to the catalyst 71. A hydrocarbon fuel is reformed there by the function of the catalyst 71, so as to produce H2 and CO. A nozzle 6 is installed to direct in the advancing direction of a swirl, and to make the gas collide with the inner wall of a cylinder 1. The reformed gas such as H2 and CO reformed in the reformer 7 are made collide directly with the inner wall of the cylinder form the nozzle 6, and the main fuel is distributed to the center f the cylinder 1, while the reformed gas is distributed around the center of the cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrocarbon fueled internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine that uses hydrocarbon as a fuel, a quenching layer is formed near the inner wall of the cylinder. Most of the fuel in the quenching layer must be discharged as unburned fuel. This is because the flame disappears in the quenching layer. In order to avoid this, there is a method of injecting fuel into the cylinder. However, the mixture of air and fuel is insufficient and soot is easily generated. Therefore, a method has been adopted in which a catalyst is provided in the exhaust pipe to oxidize hydrocarbons. However, when the temperature of the catalyst at the time of starting is low, the reaction is not sufficient and hydrocarbons are released. To overcome this, a method of reforming the fuel and supplying the reformed gas has been proposed (JP-A-3-145558, JP-A-3-145559, JP-A-2-161163).
Issue). However, in order to reform a large amount of fuel, it is necessary to mount a large catalytic converter and the mechanism is complicated, so that there is a drawback that the weight of the vehicle increases and fuel consumption increases.

In addition, "catalyst engine ..." on pages 123-128 of the 8th Internal Combustion Engine Joint Symposium Proceedings ('90 -1-24, 25, Tokyo, Japan Society of Mechanical Engineers) ... To reduce pollution of diesel engines To a new concept for
A part of the fuel is reformed to generate a reformed gas containing hydrogen, the reformed gas is used to improve the diesel combustion process, and ammonia is synthesized from hydrogen in the reformed gas to produce an engine. There is disclosed a method of decomposing nitrogen oxides discharged from the plant by reduction treatment. However, it has the following drawbacks.

(1) Since the reformed gas is pressurized and then injected into the cylinder, energy loss due to compression is large.

(2) The reformed gas contains liquid exhaust such as water and undecomposed hydrocarbon, which deteriorates the durability of the in-cylinder injection valve.

(3) Carbon is contained in the reformed gas,
This deposits on the surface of the catalyst, burns, and the catalyst is thermally deteriorated. In order to avoid this, water is added, but it takes time and effort to separately install the water tank.

(4) Since the reformed gas is injected in the latter stage of light oil combustion, the injection system becomes double and becomes complicated.

(5) Ammonia released from the exhaust pipe increases during acceleration.

(6) About 5% of the fuel quantity is reformed,
Since the fuel is injected from the conventional fuel injection valve, the generation of soot cannot be eliminated.

[0010]

In the conventional system using the reformed gas, the reformed gas is supplied to the fuel before entering the cylinder, so that the reformed gas is not supplied to the portion of the quenching layer in the cylinder. There was a problem that it did not spread. An object of the present invention is to make it possible to sufficiently supply the reformed gas (eg, H ₂ , CO, etc.) to the quenching layer of the combustion chamber of an internal combustion engine that uses hydrocarbon as a fuel.

[0011]

The requirement of the present invention is to stably form a hydrocarbon-free gas layer on the cylinder inner wall and the piston wall surface.

As a means for forming a stable gas layer on the quenching layer in the cylinder, it is effective to swirl the air-fuel mixture in the radial direction and press the gas layer against the wall surface by utilizing centrifugal force. The diffusion of the gas layer due to a large-scale turbulent flow in the cylinder is prevented, and the generation of turbulence due to the scushing generated in the gap between the cylinder head and the piston is prevented. Therefore, the shape of the combustion chamber is close to the pancake, and the swirl device is attached to the intake. As for the swirl device, there are a method of providing a shroud on the intake valve, a method of twisting the intake passage, a method of providing a swirl control valve, and a method of providing an auxiliary nozzle. The direction of the auxiliary nozzle that supplies the reformed gas to the cylinder is directed toward the wall surface of the cylinder, and the inclination from the center axis of the cylinder is 45 degrees or more so that the reformed gas directly collides with the cylinder when the intake valve opens. This forms a thin film of reformed gas on the cylinder wall. When the tilt angle is small, the collision of the reformed gas from the auxiliary nozzle is weakened and a stable film cannot be formed. Further, the gas flows too much toward the piston, and the gas film on the cylinder head becomes thin.

The reformed gas is produced by producing hydrogen from a hydrocarbon fuel (reference document, catalytic engine ...
… New concept for low pollution of diesel engine, Proc. Of the 8th Joint Symposium on Internal Combustion Engine, 90
-1-24, 25, Tokyo, Japan Society of Mechanical Engineers) and exhaust gas reforming (references MR Jones, Thermodynamic feasibility st
udies of the exhaustgas reforming of fuels, IMechE
1990, C394 / 014). At this time, in order to effectively produce gas, it is necessary to accurately control the amount of fuel and the amount of air, or the amount of exhaust gas.

[0014]

According to the present invention, the reformed fuel is supplied only to the quenching layer of the combustion chamber without mounting a large-sized catalytic converter, and the unburned hydrocarbon content is reduced with a small amount of reformed gas. The gas in the quenching layer is hydrogen or carbon monoxide, and the hydrocarbons surrounded by the gas layer burn completely. The gas layer having a thickness within several millimeters is stably held by the action of centrifugal force by swirling the air-fuel mixture.

It is sufficient to reform 3.5% of fuel during the operation of 600 rpm. Since the electrode of the spark plug is inside the reformed gas layer, the ignition is improved as compared with the conventional case. It is also possible to prevent the lubricating oil from being diluted with the hydrocarbon fuel.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a cylinder 1 has a normal cylindrical shape, and a flat head 2 and a flat piston 3 which do not cause scush are arranged. A known fuel injection valve 4 is provided near the intake valve 5. A gas nozzle 6 is provided near the intake valve 5 of each cylinder. The nozzle 6 faces the swirl advancing direction. Further, the nozzle 6 is attached so that the gas collides with the cylinder wall surface. The fuel reformer 7 is attached upstream of the branch portion 61 upstream of the nozzle 6. A fuel-air amount control device 8 is provided upstream of the reformer 7. The reformer 7 is composed of a catalyst 71 and a heater 72.

The controller 8 comprises a fuel amount controller 81 and an air amount controller 82. The controller 81 is a solenoid valve 83
including. The amount of fuel is controlled by changing the on / off time of the valve 83. Fuel is sent from the fuel pump 9 to the controller. The solenoid valve is controlled by the control unit 10. The fuel pressure is 300 kPa. Increasing the on-time of the valve 83 increases the fuel amount.

When the engine start switch is turned on, the unit 10 opens the valve 83 and sends fuel to the catalyst 71 of the reformer 7. On the other hand, the current of the heater 72 flows to heat the catalyst. The air amount controller 82 operates to send predetermined air to the catalyst 71.
As a result, the action of the catalyst 71 reforms the hydrocarbon fuel to produce hydrogen and carbon monoxide. These gases are supplied to each nozzle 6
Distributed to A known partial oxidation method is used for the reformer 7,
FIG. 6 shows the details. Since this reaction is an exothermic reaction, it is not necessary to apply a large amount of heat from the outside. Hydrocarbon C _n H _2n and oxygen O ₂ react,

[0019]

Embedded image C _n H _2n + n / 2O ₂ → nCO + nH ₂ (Formula 1) CO and H ₂ are generated.

The fuel in the fuel tank 76 is pressurized to 20 to 30 kPa by the pump 25 and sent to the evaporator 13. The evaporator 13 is heated to about 300 ° C. by an electric heater. The air is heated by the starting auxiliary heater 14, heated to 300 ° C., and mixed with the fuel in the mixing chamber 15. The air-fuel mixture is reformed in the catalytic converter 16, passes through the heat exchanger 17, and reaches the reformer outlet 18. Converter 1
6 is filled with 100 cc of nickel-based catalyst. The air is pressurized by the air pump 19, heated by the heat exchanger 17, and supplied to the mixing chamber 15.

At the time of start-up, the air-fuel ratio in the mixing chamber 15 is set to 15, the reaction is started by the claw plug 20, and when the temperature at the outlet of the converter 16 reaches 600 ° C., the air-fuel ratio is set to around 5 and H ₂ Increase the yield. When the converter 16 is sufficiently heated, the fuel valve 22 is opened, the fuel is heated by the heat of the converter 16, and the current of the heater of the evaporator 13 is cut off.

The reformed gas contains 20% of H _{2 and} 20% of CO.
%, CO ₂ 4%, O ₂ 0.2%, N ₂ 56%.

In FIG. 1, a normal injection valve 4 is attached to the intake pipe 41. The pressure of the fuel acting on the valve 4 is controlled by the regulator 91. Fuel proportional to the amount of air is also supplied to the cylinder 1 from the injection valve 4. Since the jet flow of the injection valve 4 is directed toward the spark plug 11 of the intake valve 5 as shown by A in FIG. 1, it is supplied to the central portion of the cylinder 1. On the other hand, the hydrogen gas ejected from the gas nozzle 6 is supplied along the wall surface of the cylinder 1 like B. Therefore, the surfaces of the cylinder 1, head 2, and piston 3 are covered with a thin film of hydrogen gas.

The thickness of the quenching layer on the wall surface is about 1 mm. If the bore diameter of the cylinder 1 is 70 mm and the stroke is 70 mm, the volume of the cylinder 1 is 267 cm ³ . On the other hand, the volume of the quenching layer is 23 cm ³ .

Now, assuming that the fuel is C ₈ H ₁₆ , 8 mol of hydrogen is produced from 1 mol of fuel. 1 mol of fuel weighs 1
It is 12 g. Air is 10 times as much, so 1120g
Becomes This will be about 40 moles. In FIG. 2, the volume of the quenching layer 12 is 8.6%. Therefore 8.6 out of fuel
If% is converted to hydrogen and supplied to the quenching layer 12, a uniform air-fuel mixture is formed in the cylinder 1. As mentioned above, hydrogen has a larger molar amount than gasoline. That is, when hydrogen generated in the quenching layer is supplied, the volume of the air-fuel mixture increases, so that the quenching layer 12 can actually be formed with less fuel. Further, since hydrogen has a wider heatable range than gasoline, the proportion of fuel can be reduced.

The proportion of gas in the bulk 28 in the cylinder 1 is 1 mol of gasoline to 40 mol of air. Therefore,
The volume for gasoline 1 is 41. On the other hand, the volume of the quenching layer 12 with respect to gasoline 1, that is, hydrogen 8, is 4
It becomes 8. That is, the volume increases by about 20%. If the thickness of the quenching layer 12 is the same, the fuel in the quenching layer 12 is reduced by about 20%. Since the ratio of the quenching layer 12 is 8.6%, 1.72% of fuel can be reduced. Further, since hydrogen has a wide heatable range, it is possible to reduce the concentration of fuel in the quenching layer 12. There is 6.9% of fuel in the quenching layer 12, but it is within the flammable range even if it is halved. Therefore, the fuel of 3.5% can be further reduced.

Since gasoline is supplied to the bulk 28, it is sufficient to supply 3.5% of fuel to the quenching layer 12. Moreover, since the thickness of the flame-extinguishing layer 12 decreases in inverse proportion to the rotation speed during high-speed operation, the amount of hydrogen may be small. If the fuel at 600 rpm is 1, the hydrogen at that time is 0.035 as shown in FIG. At 600 rpm, the fuel becomes 10, but hydrogen is 3.5%, not 0.35, and the thickness of the quenching layer is 1
Since it is / 10, it is 0.034. Therefore, it is sufficient to always supply the fuel from the reformer 7 at a rate of 0.035 regardless of the operating state. The flame-extinguishing layer 12 becomes thicker at the time of starting when the rotation speed is lower than 600 rpm to completely prevent the hydrocarbon fuel from remaining.

In FIG. 4, the gas nozzle 6 is mounted at an inclination of E with respect to the central axis C of the cylinder 1. Therefore, the gas flow B collides with D of the cylinder 1 and spreads vertically and horizontally as a film.
As shown in FIG. 4, D is near the point where the intake flow G passing through the intake valve 5 and entering the cylinder 1 branches up and down. E is 45 degrees or more. If it is smaller than this, the amount of gas directed upward is small, and the quenching layer 12 of the cylinder head becomes thin. FIG. 5 shows the configuration of the cylinder 1 viewed from above. The gas flow B of the nozzle 6 collides with the wall surface D and is swept along the wall surface by the swirl F.

In FIG. 5, another intake valve 51 is attached to the cylinder 1.
In order to prevent the swirl of the intake valve 5 from becoming weak, the operation of the intake valve 51 is stopped during low speed operation.

Since the amount of fuel supplied to the reformer 7 is constant regardless of the operating state, it is possible to always produce a stable gas. When the pressure of the reformer 7 is set to 200 kPa, when the pressure of the intake pipe 41 changes depending on the operating state, the nozzle 6
The flow rate from changes. At high load, the pressure in the intake pipe 41 increases and the flow rate decreases. However, at this time, combustion is accelerated and the thickness of the extinction layer is thin, which is convenient. FIG.
The pressure regulator 62 is provided downstream of the reformer 7 at the intake pipe 4
The pressure of the reformer 7 is maintained constant regardless of the fluctuation of the pressure of 1. At this time, the air amount controller 82 and the fuel amount controller 81 maintain a constant air amount / fuel amount ratio in the reformer. This ratio is about 5. At this time, the temperature of the reformer 7 changes somewhat, so that the heater 72 maintains a constant temperature.

In order to make the amount of reformed gas constant, the flow rate control valve 63 is controlled according to the fluctuation of the pressure in the intake pipe 41 to make the flow rate constant. At this time, if the amount of air and the amount of fuel supplied from the air amount controller 82 and the fuel amount controller 81 are constant, the pressure and temperature of the reformer 7 are maintained constant. Pressure of the reformer 7,
Since the temperature does not change depending on the operating state, a constant reforming gas is supplied to the cylinder 1 without delay regardless of the operating state. However, since the main fuel is generally delayed with respect to the change in the air amount, the closed-loop control is performed so that the exhaust gas concentration of the catalyst attached to the exhaust pipe becomes the theoretical mixing ratio. When the exhaust catalyst is a three-way catalyst, the theoretical mixing ratio is controlled, but it may be controlled to a predetermined mixing ratio other than that. In the lean air-fuel mixture operation, the air-fuel ratio is about 22 to 25 and the closed loop control is performed.

FIG. 7 shows an embodiment in which another reformer 30 is attached to the engine. A known fuel reforming method is used for the reformer 30. This obtains water H ₂ O and heat necessary for the reaction from the exhaust gas, and causes the reforming catalyst 36 to carry out the reaction. Hydrocarbon C _n H _2n and water H ₂ O react,

[0033]

Embedded image C _n H _2n + nH ₂ O → 2nH ₂ + nCO (Chemical formula 2) Hydrogen H ₂ and carbon monoxide CO are produced.

Introductory pipes 32, 3 provided on the exhaust pipe 31 side
3 introduces the exhaust gas into the reformer 30 by the exhaust gas pressure. The exhaust gas introduced through the introduction pipe 32 is sent to the pipe 101 in a fixed amount by the flow control valve 34. The fuel in the fuel tank 113 is pressurized by the pump 93, a fixed amount is sent to the fuel heating pipe 39 by the flow control valve 105, becomes a mixture in the pipe 101, and is sent to the heat conduction pipe 106. On the other hand, the exhaust gas introduced through the introduction pipe 33 is the heat conduction pipe 10
6 and the fuel heating pipe 39 are heated and discharged from the discharge pipe 38. The reforming catalyst 36 installed in the heat conducting tube 106 receives heat from the heat conducting tube 106 and activates it to reform the air-fuel mixture and generate hydrogen and carbon monoxide. When the temperature of the reforming catalyst 36 including the start-up is not in a temperature zone sufficient to cause the reforming reaction, the heaters 37a and 37b and the flow control valve 35 are activated, and the temperature is controlled by the control unit 50. To do. The generated reformed gas is sent to the branch section 61.
Similarly, it is supplied from the nozzle 6 to the cylinder 1. The pipe 38 joins the exhaust pipe 31 at a position apart from the introduction pipe 33. Further, by forming the confluence portion 53 into a Venturi structure, the exhaust gas used for heating can be effectively returned from the pipe 38 to the exhaust pipe 31.

An embodiment for claim 8 will be described. In the intake process of the internal combustion engine as shown in FIG. 1, if the opening degree of the intake valve 5 is small as shown in FIG. 8 (a), the flow velocity of the intake air is large, and as shown in FIG. 8 (b), it is opened. If the degree is high, the flow velocity of the intake air is low. Therefore, as shown in FIG. 9, in the initial stage 66a of opening the intake valve, the degree of opening of the intake valve is made small, a high-speed intake air flow is induced, and a strong swirl is generated in the cylinder. Immediately after this, much of the main fuel is injected to accelerate atomization of the main fuel by the high-speed flow and reduce the invasion of the main fuel into the quenching layer. In the latter stage 66b of opening the intake valve, the degree of opening of the intake valve is increased to secure the required air flow rate. FIG. 10 shows an apparatus for implementing the above. To change the opening degree of the intake valve 5, a cam 125 that activates the intake valve is used.
The shape may be changed from the conventional cam sectional shape 120 to the stepped cam sectional shape 121. The shape of the cam is changed by sliding the cam mounting shaft 124 in the direction perpendicular to the rotation direction of the cam, and the shape of the cross section is continuously changed to the required cross-sectional shape. The number of steps may be two or more.

FIG. 11 shows an embodiment for claim 6. The cylinder 1 has a normal cylindrical shape and has a flat head 2 and a flat piston 3 which do not cause scush.
A known fuel injection valve 4 is provided near the intake valve 5. The reforming gas is directly incident on the wall surface of the cylinder 1 at an angle of 45 degrees or more and collides with the upper wall of each cylinder.
40 is attached, and the check valve 141, the flow rate control valve 142, and the fuel reformer 7 are provided upstream thereof. The flow rate control valve 142 operates in synchronization with the fuel injection valve 4. Further, the check valve 141 prevents a backflow from the inside of the cylinder. The reformed gas injected from the gas nozzle 140 collides with the cylinder 1, is supplied along the wall surfaces of the cylinder 1, the head 2 and the piston 3, and is covered with a thin layer of the reformed gas. The fuel reformer 7 may be the reformer 30. The nozzle 140 may be one that imparts a swirl parallel to the cylinder head as shown in FIG. Further, there may be a plurality of nozzles.

An embodiment for claims 9, 10 and 11 will be described. In the intake process of the internal combustion engine as shown in FIG.
As shown in FIG. 3 (a), the reformed gas is supplied throughout the intake process, so that the reformed gas layer 145 can be formed in the entire quenching layer in the cylinder and the main fuel layer can be formed inside the reformed gas layer 145. As shown in FIG. 13B, the reforming gas is supplied in the first half of the intake process, so that the piston 3 of the quenching layer in the cylinder is
The reformed gas layer 145 can be generated in the vicinity. FIG.
As shown in FIG. 3 (c), a reformed gas layer 145 can be generated near the cylinder wall of the quenching layer in the cylinder by performing reformed gas in the middle of the intake process. FIG. 13 (d)
As shown in FIG. 3, by performing reformed gas in the latter half of the intake process, the reformed gas layer 1 is formed near the head 2 of the quenching layer in the cylinder.
45 can be generated. Producing the reformed gas layer in the vicinity of the spark plug 11 can improve the ignitability when the ignitability of the main fuel is poor such as at the time of starting. FIG.
As shown in (e), the reformed gas is divided into the first half and the second half of the intake process, so that the reformed gas layer 145 can be generated near the head 2 and the piston 3 of the quenching layer in the cylinder. FIG. 14 shows a circuit diagram. The fuel injection valve and the reformed gas injection valve are controlled and controlled by the CPU according to the operating conditions.

[0038]

EFFECTS OF THE INVENTION According to the present invention, in an internal combustion engine, the emission of hydrocarbons can be stably reduced with a small amount of reformed gas without mounting a large catalytic converter.

[Brief description of drawings]

FIG. 1 is a system diagram of one embodiment.

FIG. 2 is a sectional view of the inside of a cylinder.

FIG. 3 is an explanatory diagram of a relationship between a rotational speed, a thickness of a quenching layer and a fuel amount.

FIG. 4 is a sectional view of a cylinder.

FIG. 5 is a horizontal sectional view of a cylinder.

FIG. 6 is a sectional view of a fuel reformer.

FIG. 7 is a system diagram of a second embodiment.

FIG. 8 is a cross-sectional view near the intake valve.

FIG. 9 is an explanatory diagram of an intake valve opening degree.

FIG. 10 is an explanatory diagram of the shape of an intake valve starting cam.

FIG. 11 is a sectional view of a cylinder.

FIG. 12 is a horizontal sectional view of a cylinder.

FIG. 13 is an explanatory diagram of a reformed fuel injection timing.

FIG. 14 is an explanatory diagram of a reformed fuel injection timing.

FIG. 15 is a block diagram of a circuit.

[Explanation of symbols]

1 ... Cylinder, 2 ... Head, 3 ... Piston, 4 ... Fuel injection valve, 5 ... Intake valve, 6 ... Gas nozzle, 7 ... Fuel reformer,
8 ... Fuel-air amount control device, 9 ... Fuel pump, 10 ... Control unit, 11 ... Spark plug, 41 ... Intake pipe, 61 ... Branch part, 62 ... Pressure regulator, 71 ... Catalyst, 7
2 ... Heater, 81 ... Fuel controller, 82 ... Air quantity controller,
83 ... Solenoid valve, 91 ... Regulator.

Claims (11)

[Claims] 1. An internal combustion engine having an injection valve for supplying main fuel to an engine, a reformer for generating reformed gas, and means for supplying the reformed gas to the engine, wherein the reformed gas is an inner wall of a cylinder. The internal combustion engine is characterized in that the main fuel is distributed to the center of the cylinder and the reformed gas is distributed around the main fuel so as to directly collide with the fuel. 2. The internal combustion engine according to claim 1, comprising means for electrically controlling the amount of fuel and air in the reformer, and means for uniformly controlling the flow rate of the reformed gas regardless of operating conditions. organ. 3. The internal combustion engine according to claim 1, further comprising a nozzle for supplying the reformed gas to the engine. 4. The internal combustion engine according to claim 3, wherein the inclination of the nozzle is 45 degrees or more from the central axis of the cylinder. 5. The internal combustion engine according to claim 3, wherein a nozzle for ejecting the reformed gas is provided near an intake valve. 6. The internal combustion engine according to claim 3, wherein the opening of the nozzle is provided in an upper wall of the cylinder. 7. The cylinder according to claim 5, wherein two intake valves are provided in the cylinder, and a nozzle for ejecting reformed gas is provided near one of the intake valves, and the other intake valve is provided in order to give a swirl flow to the intake air. Internal combustion engine that stops the operation in the intake stroke. 8. The internal combustion engine according to claim 3, comprising an intake valve actuating cam shaped to open and close the intake valve stepwise in order to impart a swirl flow to the intake air. 9. The internal combustion engine according to claim 1, wherein the supply timing of the reformed gas to the cylinder is variable. 10. The internal combustion engine according to claim 9, wherein the timing of supplying the reformed gas to the cylinder is variable in synchronization with the engine speed. 11. The internal combustion engine according to claim 10, wherein the timing of supplying the reformed gas to the cylinder is variable according to changes in the environment.