JP2002155809A - Operating method for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operating method for a diesel engine that uses gaseous fuel as fuel and results in extremely clean exhaust gas. SOLUTION: The operating method for a diesel engine mixes, in intake air of a diesel engine, the gaseous fuel to a heating value ratio of 50% or more to an operation using only diesel fuel, and ozone to a volumetric ratio of 100 ppm to 2% to the intake air. The gaseous fuel is natural gas, methane gas and propane gas. The gaseous fuel is a gas into which liquid fuel is gasified by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a diesel engine, and more particularly to an operation method using gaseous fuel as fuel and having extremely clean exhaust gas.

[0002]

2. Description of the Related Art A diesel engine is an internal combustion engine that is compression-ignited and is an economical engine, but emits a large amount of black smoke and nitrogen oxides during the combustion process, causing serious environmental problems. A large amount of black smoke and nitrogen oxides are generated when the spray amount is large, such as during acceleration, or when the spray amount increases rapidly. In order to reduce harmful exhaust gas from diesel engines, it is effective to reduce the amount of fuel injected. It has been proposed to compensate by mixing (referred to as a dual fuel engine). However, when the blending ratio of the gaseous fuel is high, compression ignition becomes difficult, rotation unevenness occurs, and efficiency decreases. Therefore, in order to smoothly carry out compression ignition, the mixing ratio is limited to a small amount, and it is difficult to clean the exhaust gas with such a mixing ratio. Therefore, at present, it is difficult for a diesel engine to have an operation method that can continue smooth combustion without lowering the efficiency and clean exhaust gas.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and it has been found that a large amount of gas fuel such as natural gas or methane gas is mixed into intake air and stable combustion can be obtained without lowering efficiency. Therefore, it is an object of the present invention to provide a new method of operating a diesel engine having extremely clean exhaust gas.

[0004]

Means for Solving the Problems The present inventor has studied on the above problems and has obtained the following findings. In other words, even if gaseous fuel is replaced by 50% or more (in the case of operation with diesel fuel only) in the intake of a diesel engine, 100% of the intake air is replaced by ozone by volume.
m ~ 2%, black smoke without lowering efficiency,
Diesel engine operation that can reduce particulate solids and nitrogen oxides can be obtained. For gaseous fuels, besides gaseous gases at room temperature, such as methane, natural gas, and propane gas, liquid fuels must be heated and vaporized before use. The above findings were obtained. The present invention has been made based on the above findings, and has the following structures of claims 1 to 3.

1. A case in which gaseous fuel is supplied to the intake of a diesel engine at a calorific value ratio and is operated only with diesel fuel.
0% or more, and ozone in a volume ratio of 100% of the intake air
A method for operating a diesel engine, characterized in that the mixture is in the range of ppm to 2%.

2. The operating method according to claim 1, wherein said gaseous fuel is natural gas, methane gas, or propane gas.

3. The operating method according to claim 1, wherein the gaseous fuel is a gas obtained by heating and vaporizing a liquid fuel.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a diesel engine, when a gas fuel such as natural gas is mixed with an intake gas, if the mixing ratio of the gas fuel is high, ignition delay occurs and it becomes difficult to obtain stable combustion. Injection promotes ignition, and compression ignition occurs even if the injection of light oil is stopped.

The gaseous fuel mixed with the intake air preferably has a calorific value ratio of 50% or more, and ozone preferably has a ratio of 100 ppm to 2%. If the amount of gaseous fuel is less than the lower limit, the injection amount of light oil is inevitably increased to supplement the necessary combustion heat, and a large amount of black smoke and nitrogen oxides are generated. That is, in order to minimize black smoke and nitrogen oxides, it is necessary to mix a gaseous fuel having at least a lower limit or more. On the other hand, the upper limit varies depending on the degree of load. At full load, diesel combustion can be performed by the effect of ozone even if the entire fuel is replaced with gaseous fuel. It becomes stable and the efficiency tends to decrease. (That is, the optimal effect can be obtained by adjusting the ratio of gaseous fuel depending on the load in the range of 100% to 50%.)

[0007] If ozone is less than the lower limit, the effect is poor and ignition delay or misfire occurs, which is not preferable. On the other hand, even if the injection exceeds the upper limit, the effect itself does not change, so that the injection beyond this is economically disadvantageous. Therefore, it is preferable to set the upper limit or less.

In the present invention, light oil is injected to assist compression ignition, and may not be required at all under full load operation due to the effect of ozone. In addition, if the purpose is only to improve the ignitability even at the time of low load operation, it is sufficient that the idling can be maintained. With such an injection amount, there is almost no emission of black smoke or nitrogen oxides. For the emission of black smoke and nitrogen oxides, the injection amount of light oil is 40% of the total fuel calorific value.
Is almost non-existent, and increases rapidly from over 70%.

According to the present invention, when the load is 2000 pp
When mixing ozone of m or more, compression ignition becomes possible without auxiliary injection of light oil.

As gaseous fuels, natural gas, methane gas,
All gaseous fuels such as propane gas can be used. Liquid fuel such as alcohol can also be used if it is heated and vaporized to form a gas.

As ozone, the inhaled air may be passed through an ozonizer to ozonize, or pure oxygen may be used in addition to air.

[0012]

The present invention will be described by way of examples. Example 1 Displacement 276cc, air-cooled 4-cycle single cylinder, compression ratio 2
Using a 4.5 direct injection diesel engine, the mixing ratio of gaseous fuel and ozone, the injection amount of light oil, and the status of exhaust gas (black smoke, nitrogen oxides) were tested. Natural gas and methane were used as gaseous fuels. Ozone uses pure oxygen,
This was passed through an ozonizer to ozonize. FIG. 1 is an explanatory diagram of the device used for the test. Table 1 shows test results
Shown in The ratio of gaseous fuel and ozone is the ratio to air 100. The injection amount of light oil is the ratio to the amount required for full load operation.

Example 2 Natural gas was used as gaseous fuel, and ozone was ozonized by passing air in the intake air through an ozonizer. The amount of ozone in the intake air was adjusted by adjusting the output of the ozonizer. To this, natural gas was added at the following ratio (air 100
), And tested for emission of black smoke and nitrogen oxides. The results are as shown in Table 2.

Example 3 Propane gas was used as a gaseous fuel and mixed with the intake air. The ozone was ozonized by passing the air in the intake air through an ozonizer. In half-load operation, light oil is used at 2% of the total calorific value.
A portion corresponding to 0% was injected. The amount of ozone in the intake is 160
0 ppm, propane was mixed with 80% of the total calorific value, and the emission of black smoke and nitrogen oxides was tested (by injecting 20% of diesel). There was no delay in ignition, uneven rotation, and no emission of black smoke and nitrogen oxides.

[0015]

As described above in detail, the present invention is a method for preventing the emission of black smoke and nitrogen oxides without causing a delay in ignition or uneven rotation in a diesel engine. It will make a great contribution to solving the problem of environmental pollution.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a test device for a diesel engine used in an embodiment of the present invention.

Claims (3)

[Claims] 1. A case in which gaseous fuel is supplied to the intake of a diesel engine at a calorific value ratio and is operated only with diesel fuel.
0% or more, and ozone in a volume ratio of 100% of the intake air
A method for operating a diesel engine, characterized in that the mixture is in the range of ppm to 2%. 2. The operating method according to claim 1, wherein said gaseous fuel is natural gas, methane gas, or propane gas. 3. The operating method according to claim 1, wherein the gaseous fuel is a gas obtained by heating and vaporizing a liquid fuel.