JPS5844861B2 - methanol - Google Patents

Description

Detailed Description of the Invention The present invention aims to reduce harmful components in exhaust gas and improve fuel consumption rate, by converting methanol fuel into hydrogen-rich reformed gas and supplying it to the combustion chamber. The present invention relates to an internal combustion engine equipped with a methanol reformer that has been improved.

In recent years, as a measure against exhaust gas from internal combustion engines, it has been desired to improve the atomization and distribution of fuel between cylinders and to more effectively ignite and burn the air-fuel mixture.

For this reason, in the past, the engine intake system for supplying air-fuel mixture to an internal combustion engine with a sub-combustion chamber was improved to heat the air-fuel mixture of gasoline and air using engine exhaust gas heat or engine cooling water. A device for vaporizing gasoline has been devised.

However, this known device is still incomplete in reducing harmful components in exhaust gas, especially NOx, and achieving good combustion stability in all operating ranges of the engine.

For example, when an internal combustion engine with an auxiliary combustion chamber is operated under the following conditions, the inventors have obtained experimental results as shown by curves A and B in Figure 1 as the relationship between NOx in exhaust gas and shaft torque. It has gained.

Here, A is a case where a gasoline mixture with an air-fuel ratio of 4 is supplied to the auxiliary combustion chamber, and B is a case where a gasoline mixture with an air-fuel ratio of 18 is supplied to the auxiliary combustion chamber.

Here, the air ratio of the sub-intake system to the total intake air amount is assumed to be 4%.

The test engine had 4 cylinders, total displacement 1958cc, compression ratio 8.2, auxiliary combustion chamber volume 5.4cc, and torch hole 8mmφ.
, wedge-shaped combustion chamber, test conditions were 2000 rotations.
, the intake air amount is 18 pm P/sec, the average air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is 18, and the fuel supplied to the main combustion chamber is gasoline.

As is clear from the experimental results shown in Figure 1, NOx emissions are relatively small when operating with a homogeneous lean mixture as shown by curve B, but misfires begin when the ignition timing is advanced or delayed. Further, even when the ignition timing does not cause a misfire, there are many speed fluctuations due to ignition delay, and severe torque fluctuations cause problems.

On the other hand, as shown by curve A, operation using a stratified mixture has excellent combustion stability, but there is still a problem in that a large amount of NOx is emitted.

This is because conventional stratified charge combustion utilizes the normal two-layer distribution of air-fuel mixture, rich and thin. This is because it is impossible to maintain the air-fuel ratio in the sub-combustion chamber within the range of 9 to 14.

In other words, since the local rich mixture region in the auxiliary combustion chamber and the lean mixture region in the main combustion chamber coexist,
Between the essentially rich mixture region and the lean mixture region, NO
There is a mixture region with an air-fuel ratio of 15 to 16, which is inconvenient for reducing Compared to the case where it is burned reliably without burning, it becomes more.

Therefore, as described above, in the conventional system, it is still insufficient to achieve both stable combustion with little torque fluctuation and reduction of NOx.

The present invention has been made in view of the above-mentioned problems, and is aimed at converting a methanol mixture with an air-fuel ratio of 2 or less into reformed gas in an internal combustion engine with a sub-combustion chamber, and supplying this reformed gas to the sub-combustion chamber. The main combustion chamber is characterized by supplying a lean gasoline mixture to the main combustion chamber, and by setting the volume ratio of methanol supplied to the total supplied fuel to 5% to 30%. It is an object of the present invention to provide an internal combustion engine equipped with a methanol reformer that can effectively reduce NOx, achieve stable combustion with little torque fluctuation, and have low fuel consumption.

The present invention will be described below with reference to embodiments shown in the drawings.

In FIG. 2, numeral 10 denotes a methanol vaporizer that sprays and supplies methanol, which serves as methanol mixture supply means and forms a superrich mixture with an air-fuel ratio of 2 or less.

Reference numeral 11 denotes a spark plug installed downstream of the carburetor 10, and is located at a portion where the rich mixture of methanol from the carburetor 10 becomes relatively lean.

A flame extinguishing device 12 made of wire mesh, ceramics, etc. is installed between the carburetor 10 and the spark plug 11 to prevent flame from propagating to the carburetor 10 side.

This ignition plug 11 causes a partial oxidation reaction in a part of the air-fuel mixture especially when the internal combustion engine is cold started, and uses the reaction heat at that time to increase the temperature of a catalyst 14 (described later) to promote a decomposition reaction.
Further, after warming up the engine, vaporization of methanol is favorably promoted during transient times such as engine acceleration/deceleration, and responsiveness at that time is improved.

Note that an electric heater made of nichrome wire, tantalum wire, etc. can be used instead of this spark plug.

A reforming reactor 13 is provided downstream of the spark plug 11, and the inside thereof is filled with a catalyst 14 for a reforming reaction.

The outside of this reforming reactor 13 is covered with a heat insulating material 13a.

Further, the reforming reactor 13 forms part of a flow path for high-temperature exhaust gas discharged from the exhaust manifold 15, and has an exhaust gas passage 13b formed therein.

In this way, the catalyst 14 is kept warm by the exhaust heat of the exhaust gas.

The catalyst 14 is useful for effectively promoting the reforming reaction, and in this embodiment, a Ni--Cu catalyst is used.

Any commonly used catalyst can be used as this catalyst, such as Pt, Pd, Ni, etc.
, Co, Fe1Cu, Cr, Au, etc., or their metal alloys and metal oxides, as well as Al2O
Any catalyst can be used as long as it contains a material that is partially used as a ceramic component, such as 3,5i02, MgO, Cab, and ZnO.

However, the composition and amount of reformed gas depend on the type of catalyst.
Alternatively, there are some differences in the decomposition reaction initiation temperature and the amount of soot precipitated.

Among these listed catalysts, PT-based, Ni-based, and Cu-based catalysts were effective.

If the reaction temperature is 250°C or higher, gas will start to be produced, but
Practically speaking, the temperature is preferably about 300 to 700°C.

16 is a sub-intake passage, and a cooling fin 17 for cooling the reformed gas from the reforming reactor 13 is provided in the middle.

Also, in this sub-intake passage 16, a sub-throttle valve 1 is connected to the accelerator pedal via a link mechanism (not shown).
8 is provided to adjust the amount of reformed gas supplied to the sub-combustion chamber 25.

Reference numeral 20 denotes a two-stage two-stage action main carburetor, which serves as a mixture supply means and sprays and supplies gasoline to form a lean mixture of gasoline and air.

Here, the mixture consisting of the lean mixture and the reformed gas is set to have an equivalence ratio of 0.78 or less as a whole.

Here, the equivalence ratio indicates the ratio of the amount of oxygen required to completely burn the combustible components in the reformed gas and the lean mixture to the total amount of oxygen contained in the supplied air.

21 is the main throttle valve and two butterfly valves 2
1a and 21b, and is interlocked with an accelerator pedal (not shown).

Here, the sub-throttle valve 18 and the main throttle valve 20 are interlocked by a cam mechanism or link mechanism (not shown), and the total amount of fuel supplied to the engine [(gasoline +
The amount of methanol supplied is 5% of the amount of methanol)
The operating opening degree is set to ~30% (tatami, volume ratio).

Reference numeral 22 denotes a main intake passage that guides the lean air-fuel mixture formed in the carburetor 20, and this main intake passage 22 communicates with the main combustion chamber 24 of the engine via a main intake valve 23.

Further, the main intake passage 22 is partially provided with fins, and is heated by the exhaust gas flowing through the exhaust manifold 15.

Reference numeral 25 denotes a sub-combustion chamber formed by a cup body, and the sub-combustion chamber 25 and the sub-intake passage 16 communicate with each other via a sub-intake valve 26.

Further, a torch hole 25a and an ignition hole 25b are opened in the cup body, and the auxiliary combustion chamber 25 and the main combustion chamber 24 are passed through the torch hole 25a.

Further, the ignition plug 27 is provided by the ignition hole 25b of the cup body.
Sparks are guided from the combustion chamber 25 to the sub-combustion chamber 25.

In the above configuration, a rich mixture of methanol formed in the methanol vaporizer 10 is heated and vaporized by the ignition plug 11, and a portion thereof is partially oxidized and introduced into the reforming reactor 13.

The catalyst 1 is effectively maintained at a high temperature by the engine exhaust gas heat.
4, it is converted into a reformed gas containing hydrogen, which is cooled to an appropriate temperature by cooling fins 17.

At this time, the reformed gas is supplied from the sub-intake passage 16 to the sub-combustion chamber 25 in a state containing a large amount of hydrogen.

In addition, this reformed gas is obtained by converting and reforming the methanol mixture by selecting methanol among the fuels, so the reforming reaction is faster than reforming other fuels such as gasoline. There is almost no soot generated during the process, and the reformed gas is of good quality.

On the other hand, a main carburetor 2 is installed in the main combustion chamber 24 during the intake stroke of the engine.
A lean mixture of gasoline from zero is mainly introduced, and a part of the reformed gas in the sub-combustion chamber 25 flows through the torch hole 25a.

The spark plug 2 is compressed during the compression stroke of the engine.
7, the lean air-fuel mixture in the sub-combustion chamber 25 is first combusted.

In this way, since the reformed gas containing hydrogen with good ignitability is introduced into the sub-combustion chamber 25, ignition is improved while the air-fuel ratio within the sub-combustion chamber 25 remains lean, and NOx The occurrence of this is suppressed and reduced, and due to the presence of the reformed gas, the lean mixture is stably combusted while combustion cycle fluctuations are suppressed.

The characteristics of shaft torque and NOx emissions at this time, as shown in curve C in Figure 1, for example, combine the excellent characteristics of both the conventional stratified charge combustion operation and the uniform lean combustion operation described above. Combustion stability and low NOx can be achieved at the same time, and M, B, T, (Minimum
5paric advice forBest
Torgue), the shaft torque is large and the thermal efficiency is also improved.

In this case, the combined equivalent ratio of methanol and gasoline is 0.82, and the volume ratio of the amount of methanol supplied to the total fuel supplied is 10%.

As described above, by introducing reformed methanol gas into the auxiliary combustion chamber, it is possible to significantly improve the exhaust gas components, fuel efficiency, and combustion stability of an internal combustion engine. Since methanol plays a role as a source, the amount of methanol supplied for generating reformed gas has great significance.

In other words, in order to ensure sufficient ignitability, the minimum amount of reformed gas is required to sufficiently scavenge the residual gas in the auxiliary combustion chamber 25 during the intake stroke of the engine, and The proportion of the volume of the sub-combustion chamber 25 in the volume is usually about 1%, and the inventors have found that the amount of reformed gas is greatly affected by this proportion.

Therefore, the present inventors have determined that the amount of reformed gas necessary to sufficiently scavenge the sub-combustion chamber and obtain good ignitability is determined by the reforming reaction under conditions where the air-fuel ratio of methanol and air is 2 or less. It has been found from extensive experimental results that the volumetric proportion of methanol in the total fuel supplied to the engine, λf, can be obtained by taking into account the volume increase due to .

In addition, if the amount of reformed gas supplied is greater than necessary, not only will methanol be used in excess of the required amount, which will result in a waste of relatively expensive methanol, but since the reformed gas is a gas, reforming It was found that an increase in the volume of gas causes a decrease in the suction efficiency of the internal combustion engine, resulting in a decrease in output, and the present inventors determined that the methanol volume fraction λf
It was concluded that it is preferable to

Therefore, if the above-mentioned λf is set, good results can be obtained in terms of practical use or driving performance.

For example, the present inventors have experimentally determined that when the air-fuel ratio of methanol and air is 0.65 and the volume ratio of methanol to the total fuel supply is 10%, the components shown in Table 1,
In particular, it has been confirmed that an appropriate amount of reformed gas with a hydrogen concentration of about 50% can be obtained.

In this way, the engine effectively performs lean combustion with an appropriate amount of reformed gas containing a high concentration of hydrogen, and fully exhibits its functions.

As described above, in the present invention, methanol and air are mixed in an internal combustion engine consisting of a main combustion chamber in which the combustion chambers communicate with each other and a sub-combustion chamber in which a spark plug is installed, and the air-fuel ratio is 2 or less. a reforming reactor that is supplied with a mixture from the methanol mixture supply means and converts the mixture into a hydrogen-rich reformed gas; comprising a sub-intake passage for supplying the sub-combustion chamber, a mixture supply means for forming a lean mixture of gasoline and air, and a main intake passage for supplying the lean mixture to the main combustion chamber; The volume ratio of the methanol supplied to the total supplied fuel is 5% to 3.
Since it is 0%, (1) good combustion stability can be obtained and torque fluctuations are small.

(2) It becomes possible to effectively burn a lean air-fuel mixture with a high air-fuel ratio that cannot be ignited and combusted in a conventional internal combustion engine with a sub-combustion chamber, and NOx can be significantly reduced, resulting in low fuel consumption.

(3) Furthermore, normal internal combustion engines require fuel with a high octane rating and are mixed with additives such as lead compounds, but the octane rating of reformed gas is sufficiently high that there is no need to mix in harmful additives. .

It has this excellent effect.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between engine shaft torque and NOx emissions, and FIG. 2 is a cross-sectional configuration diagram showing an embodiment of the present invention. 10... Methanol vaporizer, 11...
・Spark plug, 13... Reforming reactor, 14...
...Catalyst, 15...Exhaust manifold, 1
6...Sub-intake passage, 18...Sub-slot 7
) Le valve, 20... Main carburetor, 21...
... Main throttle valve, 22 ... Main intake passage, 24 ... Main combustion chamber, 25 ... Sub-combustion chamber, 27 ... Spark plug.

Claims (1)

[Claims] 1 Methanol mixing in which methanol and air are mixed to form a mixture with an air-fuel ratio of 2 or less in an internal combustion engine consisting of a main combustion chamber and an auxiliary combustion chamber in which a spark plug is installed, in which the combustion chambers communicate with each other. a reforming reactor to which a mixture is supplied from the methanol mixture supply means and converts the mixture into hydrogen-rich reformed gas; and a reforming reactor for supplying the reformed gas to the sub-combustion chamber. a width intake passage, a mixture supply means for forming a lean mixture of gasoline and air, and a main intake passage for supplying the lean mixture to the main combustion chamber, and the main intake passage has a width of An internal combustion engine equipped with a methanol reformer, characterized in that the volume ratio of the methanol is 5% to 30%.