JPS6329014A - Fuel feeding device for diesel engine - Google Patents

Abstract

PURPOSE:To improve the ignition performance of the jetted main fuel by gasifying the low cetane value fuel and allowing said gasified fuel gas to collide onto the heated surface of a heating body installed into a combustion chamber through a suction means and previously increasing the environmental temperature in the combustion chamber. CONSTITUTION:The low cetane value fuel 2 such as alcohol is sent into a gasifier 3 from a tank 1 by a pump 4, and gasified. The gasified fuel gas is sent into a suction port 13 through a passage 6. When an engine completes the suction cycle, a suction valve 14 is opened to imbibe the fuel gas into a combustion chamber 7, and the fuel gas is mixed with the inhaled air and allowed to collide with the heated surface of a glow plug 11 as heating body. Then, the suction valve 14 is closed, and the fuel gas is combusted, and the pressure in the combustion chamber 7 and the environmental temperature are increased. Then, main fuel is jetted into the combustion chamber 7 from a nozzle 12, and the main fuel 2 is easily ignited at the high environmental temperature.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a fuel supply device for a diesel engine using a low cetane number fuel such as alcohol as a fuel, and more particularly, it relates to a fuel supply device for a diesel engine using a low cetane number fuel such as alcohol. The present invention relates to a fuel supply system for a diesel engine using low cetane number fuel.

In prior art diesel engines, light oil is used as fuel, but since the amount of light oil that can be obtained from crude oil is limited, lower alcohols such as methanol and ethanol may be used as fuel for diesel engines as alternative fuels in the future. It has been proposed to do this, and research is being conducted on various aspects to put it into practical use. (For example, JP-A-60-125
762 etc. ) Problems to be Solved by the Invention However, when a low cetane number fuel such as a lower alcohol is used as a fuel for a diesel engine, it is extremely difficult to operate the diesel engine by compression ignition at a conventional compression ratio. Therefore, the inventors of the present invention conducted extensive research and found a way to enable compression ignition operation with the conventional compression ratio by installing a heating element such as a glow plug inside the combustion chamber.
They devised a way to ignite the fuel using that hot surface.

According to this method, it is possible to improve the ignition performance to a considerable extent, but even in a diesel engine in which a heating element such as a glow plug is installed in the combustion chamber, it is still possible to improve the ignition performance, especially when the temperature inside the combustion chamber is low. In the load operation range, there were problems such as poor ignitability, poor fuel efficiency, and increased hydrocarbon emissions.

In order to solve these problems, methods such as increasing the compression ratio even higher or insulating the combustion chamber can be considered, but increasing the compression ratio inevitably increases pumping loss and mechanical resistance. In addition, when trying to insulate,
A heat insulating member with sufficient mechanical strength has not been obtained,
In addition, a new problem of high costs has arisen, and the current situation is that satisfactory results have not been obtained.

OBJECT OF THE INVENTION The object of the present invention is to provide a fuel supply device for a diesel engine using low cetane number fuel, which has significantly improved ignitability and combustibility, and has low hydrocarbon emissions. .

Structure of the Invention This object of the present invention is achieved by providing a heating element within the combustion chamber and providing a fuel gas suction means at a position where the gasified fuel gas can be brought into contact with the heating surface of the heating element. Ru.

By configuring the fuel supply system for a diesel engine in this way, in the first half of the compression process, a small amount of fuel gas is sucked in so as to collide with the hot surface of the heating element, and is combusted, thereby creating an atmosphere inside the combustion chamber. can increase the temperature,
It becomes possible to significantly improve the ignitability of the main fuel that is injected later, thereby improving combustion efficiency and reducing the amount of hydrocarbons generated.

In the present invention, the heating element is not particularly limited and may be any known heating means such as a glow plug.

In the present invention, the method of gasifying the fuel is not particularly limited, and includes methods such as evaporation by heating, and methods of chemically decomposing the fuel and gasifying it.

If the fuel is to be evaporated or gasified by heating, a means for evaporating or gasifying the fuel such as an electric heater may be provided, or the heat of the exhaust gas may be used to gasify the fuel. A means for doing so may be provided.

EXAMPLES Hereinafter, examples of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is an overall schematic diagram of a fuel supply system for a diesel engine showing one embodiment of the present invention, and FIG. 2 is a detailed diagram of a combustion chamber.

In Figures 1 and 2, 1 is a fuel tank, 2 is a fuel tank,
3 is a fuel gasifier that gasifies the fuel; 4 is a fuel pump that pumps the fuel 2 to the fuel gasifier 3; and 5 is a fuel pump that pumps the fuel 2 when the pressure inside the fuel gasifier 3 reaches a predetermined pressure. A pressure regulating check valve 6 is a fuel gas passage that controls the flow of fuel gas into the fuel gasifier 3. Further, 7 is a combustion chamber, in which an intake valve 8 and an exhaust valve 9 are provided, and a cylinder 10 is provided inside the combustion chamber. 11 is a glow plug that is a heating element that ignites fuel gas, and 12 is a fuel injection nozzle that injects fuel into the combustion chamber 7. Also, 13
1 is a fuel gas suction boat that sucks fuel into the combustion chamber 7;
Reference numeral 4 denotes a fuel gas intake valve, which is provided at a position and in a direction such that it collides with the hot surface of the glow plug 11 when the fuel gas is sucked into the combustion chamber.

In FIG. 1, fuel 2 is pumped from a fuel tank 1 to a fuel gasifier 3 by a fuel pump 4.
Gasified inside. The gasified fuel gas passes through the fuel gas passage 6 and reaches the fuel gas intake port 13 due to its evaporation pressure. When the engine completes the intake stroke, first, the fuel gas intake valve 14 is opened and fuel gas is inhaled.
It collides with the hot surface of the glow plug 11 while mixing with the intake air. Thereafter, the fuel gas intake valve 14 closes, and the fuel gas that hits the hot surface of the glow plug 11 ignites and burns, increasing the pressure inside the combustion chamber 7. The temperature also rises. Next, the fuel injection nozzle 12
More fuel is injected into the combustion chamber 7, but at this point,
Since the atmospheric temperature within the combustion chamber 7 is high, the injected fuel is easily ignited. Thus, according to this embodiment, the ignitability of the fuel is improved, and therefore the thermal efficiency is also improved, and the amount of hydrocarbon generation is significantly reduced.

FIG. 3 shows an example of the timing of opening and closing of the intake valve 8, exhaust valve 9, and fuel gas intake valve 14 in this embodiment, where the horizontal axis shows the crank angle and the vertical axis shows the response time. It shows the amount of lift. In FIG. 3, A indicates the intake valve, B indicates the exhaust valve, and C indicates the opening and closing timings of the fuel gas intake valve, respectively. Also, the fourth
The figure shows the pressure inside the combustion chamber 7, the horizontal axis is the crank angle, the vertical axis is the pressure, the curved line is the pressure inside the combustion chamber 7 in this example, and the curve E is the conventional diesel engine. The pressure inside the combustion chamber 7 when using the fuel supply device shown in FIG. In FIG. 4, the curved line Fil indicates an increase in pressure due to combustion of fuel gas, and it can be seen that in this example, the pressure in the combustion chamber 7 increases before fuel injection.

FIG. 5 is an overall schematic diagram of a fuel supply system for a diesel engine showing another embodiment of the present invention, and FIG.
FIG. 3 is a schematic cross-sectional view of a fuel gas evaporator 3 used in the illustrated embodiment.

In FIGS. 5 and 6, a fuel gasifier 3 that utilizes the heat of exhaust gas is used to evaporate and gasify fuel. In FIG. 5, reference numeral 20 denotes an exhaust gas passage, which branches in the middle, and a part of the exhaust gas is guided to the fuel gasifier 3 through an exhaust gas branch pipe 21. In FIG. 6th
As shown in the figure, the fuel gasifier 3 has a fuel passage 23 in a container 22 through which exhaust gas flows in a meandering manner so as to increase the contact area with the exhaust gas in order to increase heat exchange efficiency. ,It is configured. When using the heat of exhaust gas as a heat source to evaporate and gasify fuel gas,
Since the temperature and flow rate of exhaust gas vary depending on the engine load and engine speed, in order to evaporate and gasify the desired amount of fuel gas in the fuel gasifier 3, the fuel gasifier 3
It is necessary to control the flow rate of exhaust gas supplied to the exhaust gas.

For this reason, in this embodiment, a butterfly valve 24 is provided in the exhaust gas branch pipe 21, and a valve control means (not shown) controls the temperature in the fuel gasifier 3.
Its opening degree is controlled.

Furthermore, as shown in FIG. 7, the amount of fuel gas to be drawn into the combustion chamber 7 varies depending on the engine load. It has been found that in high load ranges, it is desirable to reduce the amount of fuel gas that evaporates and gasifies. Therefore, although not shown, it is desirable to further provide a control means for controlling the opening degree of the butterfly valve 24 by detecting the engine load based on the pressure inside the intake pipe or the like.

FIG. 8 is an overall schematic diagram of a fuel supply system for a diesel engine showing another embodiment of the present invention.

In Figure 8, the amount of fuel gas evaporated and gasified is
The amount of fuel fed under pressure to the fuel gasifier 3 is controlled in order to optimally control the engine operating state. That is, the engine operating state is detected by detecting the engine speed, intake pipe pressure, etc., and based on this,
A control means (not shown) calculates the amount of fuel to be pumped to the fuel gasifier 3 and outputs a control signal to the injector 25. The injector 25 adjusts the amount of fuel according to this control signal and pumps it to the fuel gasifier 3. Therefore, the butterfly valve 24 in the embodiment of FIG.
exclusively controls the amount of exhaust gas supplied so as to keep the temperature inside the fuel gasifier 3 constant.

FIG. 9 is an overall schematic diagram of a fuel supply system for a diesel engine showing another embodiment of the present invention.

In FIG. 9, a fuel gasifier 3 is provided which chemically decomposes the fuel and gasifies it using a fuel reforming catalyst instead of evaporating the fuel to gasify it. That is, when methanol is used as a fuel, it is decomposed by a known reforming catalyst as follows.

CH30H→2H2+CD The hydrogen gas and carbon monoxide gas thus obtained have approximately 20% higher energy than methanol, and do not liquefy even when compressed, and can be sucked into the combustion chamber 7 at the desired timing. This is desirable because it allows In FIG. 9, the fuel gas compressor 26 compresses the fuel gas and sends it to the combustion chamber 7. In FIG.

It goes without saying that the present invention is not limited to the above-mentioned examples, but can be modified in various ways within the scope of the invention described in the claims, and these are also included within the scope of the present invention. stomach.

For example, in the above embodiment, an example was given in which the heat of the exhaust gas is used as a heat source for evaporating and gasifying fuel gas. Needless to say, it's a good thing. .

Effects of the Invention According to the present invention, before the main fuel is injected, the fuel gas is sucked into the combustion chamber, ignited by the heating element, and combusted.
The atmospheric temperature inside the combustion chamber is raised in advance, so even when using low-cetane fuel that is difficult to ignite, ignitability is significantly improved, resulting in improved combustion efficiency and reduced hydrocarbon generation. It becomes possible to significantly reduce the amount.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of a fuel supply system for a diesel engine showing one embodiment of the present invention, and FIG. 2 is a detailed diagram of a combustion chamber. FIG. 3 is a graph showing an example of the timing of opening and closing of the intake valve, exhaust valve, and fuel gas intake valve in the embodiment of FIG. 1, and FIG. 4 is a graph showing the pressure inside the combustion chamber. It is. FIG. 5 is an overall schematic diagram of a fuel supply system for a diesel engine showing another embodiment of the present invention, and FIG. 6 is a schematic cross-sectional view of a fuel gas evaporator used in the embodiment of FIG. It is a diagram. FIG. 7 is a graph showing an example of the relationship between the amount of fuel gas to be drawn into the combustion chamber and the engine load. Figures 8 and 9
The figure is an overall schematic diagram of a fuel supply system for a diesel engine showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Fuel tank, 2... Fuel, 3... Fuel gasifier, 4... Fuel pump, 5... Pressure regulating check valve, 6... Fuel gas passage, 7...・Combustion chamber, 8
...Intake valve, 9...Exhaust valve, 10...Piston, 11...
Glow plug, 12... Fuel injection nozzle, 13... Fuel gas intake boat, 14... Fuel gas intake valve, 20... Exhaust gas passage, 21... Exhaust gas branch pipe, 23... Fuel passage, 24... Butterfly valve, 25... Injector, 26... Fuel gas compressor. Fig. 1 Fig. 2 Fig. 3 Crack angle e Fig. 4 Cla> Evening angle θ Fig. 6 Child Fig. 7 Enshin cargo

Claims (1)

[Claims] In a fuel supply system for a diesel engine using low cetane number fuel, a heating element is provided in the combustion chamber, and a fuel gas suction means is provided at a position where gasified fuel gas can be brought into equilibrium with the heat surface of the heating element. A fuel supply device for a diesel engine, characterized in that it is provided with.