Method to Decrease Black Smoke of Diesel

The present invention relates to a method to decrease black smoke of diesel engine by injecting combustible gas or non-combustible gas in the latter stage of diesel engine combustion.

In a diesel engine, it is essential to furnish the air-fuel mixture as completely and quickly as possible and to achieve complete combustion of as much fuel as possible by the air in the combustion chamber in order to convert the fuel energy efficiently into work. However, as far as diesel fuel oil is used as fuel, the unburnt products remain more or less, and these substances are emitted as black smoke.

From the viewpoint to eliminate black smoke, a diesel engine not discharging black smoke has already been attained in a methanol diesel engine using methanol as fuel because methanol is an oxygen-containing substance. However, methanol is not available at the filling stations, and the problems remain with regard to the supply and the cost of methanol.

It is an object of the present invention to decrease black smoke emitted by diesel fuel combustion by injecting the combustible gas or non-combustible gas in the latter stage of diesel fuel combustion.

Another object of this invention is to obtain the oxygen-containing combustible gas by reforming a part of diesel fuel by a fuel reforming apparatus.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

To attain these objects, the method to decrease black smoke of diesel engine according to this invention is characterized in that a fuel injection nozzle to inject the diesel fuel into cylinder and an auxiliary injection nozzle to inject the combustible gas or non-combustible gas are provided, and that said combustible gas or non-combustable gas is injected in the latter stage of the diesel fuel combustion. More concretely, a part of fuel is reformed to combustible and/or non-combustible gases by a fuel reforming apparatus and these gases are injected into cylinder, or the combustible gas or non-combustible gas is prepared in another gas cylinder and this gas is injected in the latter stage of the combustion.

In diesel engine, carbon is generated when diesel fuel injected from fuel injection nozzle is burnt within the cylinder, because the fuel and the air are not sufficiently mixed together. Whereas, according to this invention, in the latter stage of the diesel fuel combustion, the combustible gas containing preferably oxygen or non-combustible gas consisting preferably of a large molecular weight is injected from the auxiliary injection nozzle into the cylinder, and the mixing of the fuel with the air is further accelerated within the cylinder by the explosion energy or the kinetic energy induced by gas injection, which accelerate reburning of carbon generated at the former stage of the diesel fuel combustion.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

FIG. 1 is a schematical drawing of an embodiment of the method to decrease black smoke of diesel engine according to the present invention;

FIG. 2. is a diagram to explain the principle of the method according to this invention;

FIG. 3 is a diagram showing the results of the experiment, in which black smoke is decreased when each of the gases is injected.

In the following, the embodiment of the present invention will be described in connection with the drawings. In the drawings, 1 refers to a cylinder of an engine, 2a a cylinder head, 2b a piston, 3a fuel injection nozzle, 4 an auxiliary injection nozzle, 5 a fuel tank, 6 an air tank, and 7 a fuel reforming apparatus.

On the cylinder head 2 of the engine, a diesel fuel injection nozzle 3 and an auxiliary injection nozzle 4 are provided, and the fuel from a fuel tank 5 is injected from a fuel injection nozzle 3 into the cylinder 1. A part of the fuel from the fuel tank 5 and the air tank in the air tank 6 are sent to the fuel reforming apparatus 7, where the fuel is partially oxidized. The reformed gas mixture is injected from said auxiliary injection nozzle 4 into the cylinder 1 in the latter stage of the diesel fuel combustion.

In the fuel reforming device 7 as described above, diesel fuel is decomposed by partial oxidation reaction using a nickel catalyst. The reaction formula is as follows:

The combustible gases consisting of the carbon monoxide and the hydrogen thus generated are injected from the auxiliary injection nozzle 4 into the cylinder 1. FIG. 2 shows the condition of the combustion in the cylinder. When the diesel fuel injected from the fuel injection nozzle 3 is burnt in the cylinder, carbon is generated because the fuel and the air are not sufficiently mixed. In this embodiment, the combustible gas is injected from the auxiliary injection nozzle 4 into the cylinder 1 in the latter stage of the combustion. The mixing of the fuel with the air in the cylinder is further accelerated by the energy of the explosion induced by combustible gas combustion, and black smoke is decreased.

The present invention is naturally not limited to the above embodiment, and various modifications and variations can be conceived. For example, the quality of a part of the fuel may be improved to the combustible gas by a fuel reforming apparatus, or the combustible gas consisting of hydrogen or carbon monoxide may be prepared in another gas cylinder, and this gas may be injected in the latter stage of the combustion.

Or, the non-combustible gas such as oxygen (O.sub.2), helium (He), nitrogen (N.sub.2), argon (Ar), etc. may be injected in the latter stage of the combustion.

FIG. 3 shows how black smoke is decreased when the above 2 types of combustible gas or 4 types of non-combustible gas are injected. In the figure, the line Y represents the level of black smoke when gas is not injected.

Further, the gas injection may be controlled in such manner that gas is injected only when the engine is operated in high load condition.