JPH0211736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel supply system for an internal combustion engine that gasifies fuel using the heat of exhaust gas and introduces the gasified fuel into a combustion chamber through a path independent of intake air. Regarding the method.

Hereinafter, in this specification, "gasified fuel" refers to a fuel that is partially or completely vaporized, or a fuel that is partially or entirely converted into a reformed gas having a different composition through a chemical reaction.

In an internal combustion engine, in principle, several tens of percent of the thermal energy generated when fuel is combusted is wasted as heat in the exhaust gas. If heat from this exhaust gas can be recovered in some way and added to the engine's output, the engine's thermal efficiency will improve.

2. Description of the Related Art Conventionally, one method for recovering heat from exhaust gas is to vaporize fuel using the heat of exhaust gas and recover an amount of heat corresponding to the latent heat of vaporization of the fuel from the exhaust gas. Furthermore, by applying a reforming catalyst,
For example, when the fuel is methanol, heat from the exhaust gas is recovered by converting it into reformed gas fuel with a composition that has a higher calorific value than the original fuel through an endothermic reaction such as CH ₄ O → CO + 2H ₂ . There is also. If the heat of the exhaust gas is recovered in this way, the thermal efficiency of the engine will improve depending on the heat of vaporization of the fuel or the heat absorbed in an endothermic reaction.

However, when the fuel is gasified in this way, its volume increases compared to when it is liquid, so if you try to inhale it into the combustion chamber together with the intake air as in the past, the engine will not be able to intake it. Although the amount of air decreases and thermal efficiency improves, the output of the engine does not increase or sometimes decreases.

The present invention prevents the above-mentioned decrease in intake air amount by inhaling only air during intake and directly introducing gasified fuel into the combustion chamber through a path different from the air passage. The passive objective is to prevent a decrease in output.

An active object of the present invention is as set forth in claim 1.
As described in section 1, by introducing gasified fuel directly into the combustion chamber, the introduction timing is mainly in the latter half of the compression stroke, thereby improving both the engine's output and thermal efficiency.

The principle of the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of the reduction in the amount of intake air due to fuel gasification and its prevention effect, which is a negative objective of the present invention, and A represents the volume of gas that can be taken in by the engine. B is when liquid fuel is inhaled together with air, C is when gasified fuel is inhaled together with air, and D is when only air is inhaled, and then gasified fuel is directly introduced into the combustion chamber. The white area indicates the volume occupied by air, and the shaded area indicates the volume occupied by fuel. D' indicates the volume occupied by the air and gasified fuel in the combustion chamber after the gasified fuel is introduced in case D.

In case B, since the volume of liquid fuel is extremely small compared to the volume of air, the reduction in intake air amount due to intake of fuel together with air is negligible. In the case of C, the volume of gasified fuel ranges from several percent to several tens of percent of the volume of intake air, so the reduction in intake air amount by sucking fuel together with air is large, and therefore the engine's Output may be reduced. In particular, in the case of the above-mentioned methanol reformed gasified fuel, since the number of fuel molecules increases, the amount of intake air is drastically reduced by inhaling it together with air, and therefore the output is also significantly reduced. In case D, that is, in the fuel supply method according to the present invention, only air is taken in, so that the amount of intake air does not decrease due to gasified fuel.

FIG. 2 illustrates the positive objectives of the invention:
In the schematic cycle diagram, the horizontal axis represents the internal volume of the combustion chamber of the engine, and the vertical axis represents the pressure of air, air/fuel mixture, or combustion gas within the combustion chamber. The solid closed curve EFGHE is a normal cycle, that is, a cycle in which fuel is inhaled together with air.
EF is compression stroke, FG is pressure increase due to combustion, GH
indicates the expansion stroke, and HE indicates the pressure drop due to blowdown. The broken closed curve EJKLMNE is the cycle according to the invention.

In the cycle according to the invention, only air is compressed (E→J), and in the middle of the compression stroke, gasified fuel is introduced directly into the combustion chamber at a higher pressure than the air inside the combustion chamber. Then, since the amount of gas in the combustion chamber increases, its pressure increases (J→K). Furthermore, the mixture of air and gasified fuel is compressed to top dead center (K→
L) and then burn it. Pressure before combustion (L)
is higher than the pre-combustion pressure F in the normal cycle, so the post-combustion pressure M is higher than the post-combustion pressure G in the normal cycle.

Cycle work is a closed curve in a normal cycle
It corresponds to the area of EFGHE, and in the cycle of the present invention corresponds to the area of the closed curve EJKLMNE. In the cycle of the present invention, compared to the normal cycle, there is an increase in expansion work (corresponding to the area of closed curve HGMNH) and an increase in compression work (corresponding to the area of closed curve JFLKJ).
The cycle work increases by the amount less , and therefore the output of the engine increases. Furthermore, in order to reduce the amount of increase in compression work, it is desirable to introduce the gasified fuel into the combustion chamber (J in Figure 2) as close to the end of the compression stroke (F in Figure 2) as possible. This is the gist of the content stated in claim 1.

When water is added to the fuel and gasified, the total volume of the gasified fuel increases, so the pressure (K in Figure 2) when the gasified fuel is introduced into the combustion chamber increases, and the pressure after compression increases. The pressure after combustion (L in the same figure) and the pressure after combustion (M in the same figure) increase. Therefore, by adding water to the fuel and gasifying it, the cycle work of the present invention becomes greater. This is the gist of the content stated in claim 2 or 3.

Since Figure 2 is a schematic cycle diagram, it ignores the time required to introduce gasified fuel (J → K is vertical), but in an actual engine, it takes a finite amount of time to introduce fuel. Therefore, the timing for starting fuel introduction may be in the first half of the compression stroke or before the start of the compression stroke, and the timing for completing fuel introduction may be after the start of the expansion stroke.

In order to introduce gasified fuel into the combustion chamber, it is necessary to push the gasified fuel under a higher pressure than the air existing in the combustion chamber, and it is necessary to keep the gasified fuel under high pressure. Gasifying fuel and then compressing it to high pressure requires a large amount of energy. However, in the present invention, as will be described later in the explanation of the embodiments, pressure is applied to the fuel while it is in liquid form using a pump or compressed air, and the heat of the exhaust gas is used to release the fuel under pressure. Most of the energy to obtain high-pressure gasified fuel is supplied from the heat of the exhaust gas, so the energy that must be provided from pumps, etc. is only the energy required to pump the liquid fuel. However, the increase in cycle work is negligible compared to the increase in cycle work achieved by the present invention.

In order to gasify liquid fuel under pressure, it must be heated to a temperature where the vapor pressure of the fuel is higher than the pressure. FIG. 3 shows the relationship between temperature and vapor pressure when the fuel is methanol. For example, to vaporize methanol into gasified fuel under a pressure of 10 kg/cm ² , it is sufficient to heat it to approximately 140°C as shown at point P, and this temperature can be easily reached by the heat of the exhaust gas. This is the temperature that can be heated to .

When an endothermic reaction is caused in the fuel by the action of the catalyst and the heat of the exhaust gas, the fuel becomes a reformed gas fuel having a composition with a higher calorific value, thereby improving the thermal efficiency of the engine. For example, when the fuel is methanol, due to the endothermic reaction CH ₄ O → CO + 2H ₂ , the calorific value is approximately
Increase by 20%. However, when such a decomposition reaction occurs, the number of molecules of the fuel gas increases, so its volume increases, and the amount of intake air required to inhale the gasified fuel together with air becomes even more significant. Therefore, the method of the present invention, in which gasified fuel is directly introduced into the combustion chamber, is even more effective when attempting to improve the thermal efficiency of an engine by reforming and gasifying fuel through an endothermic decomposition reaction. do. This is the gist of the content stated in claim 4.

High temperatures are required to decompose fuel under high pressure. Figure 4 is a diagram showing the equilibrium relationship between temperature and pressure in which 98% of methanol is reformed into CO and H ₂ by the decomposition reaction described above.
For example, when the pressure is 10 kg/cm ² , the temperature is approximately 290° C., which can be sufficiently reached by heating with the heat of exhaust gas.

Furthermore, it is difficult to use a fuel with a _high self-ignition _temperature such as _methanol in a compression ignition engine _; By reforming methanol into fuel, it becomes possible to use it as a fuel for compression ignition engines. The content of claim 4 also includes this objective.

A specific implementation method of the present invention will be described with reference to FIG. 5, taking as an example the case where it is applied to a four-stroke reciprocating engine.

A gasified fuel introduction hole 3 is provided in a part of the wall of the combustion chamber of the engine 1, and a gasified fuel introduction valve 4 is provided at the opening of the gasified fuel introduction hole 3 to the combustion chamber 2.

(b) A fuel gasification device 8 is provided in the middle of the exhaust gas passage 6, in which the exhaust gas and the fuel are separated by a heat exchange wall 7, and the heat of the exhaust gas is transferred to the fuel via the heat exchange wall 7.

(c) Liquid fuel is force-fed to the fuel inlet of the fuel gasifier 8 by the fuel pump 9, and the gasified fuel is guided to the gasified fuel introduction hole 3 through the gasified fuel conduit 5.

(d) Drive the gasified fuel inlet valve 4 using a cam, hydraulic pressure, electromagnetic force, etc. to open it at an appropriate time and for an appropriate amount of time depending on the rotational speed of the engine 1, the load, the pressure of the gasified fuel, etc. .

In the case of claim 3, water is mixed into the fuel in the middle of the route for supplying the liquid fuel to the fuel gasifier 8.

In the case of claim 4, the fuel passage of the fuel gasifier 8 is filled with a catalyst, or the catalyst is supported on the surface of the heat exchange wall 7 on the fuel passage side, or the heat exchange wall 7 is Makes itself a catalyst. Alternatively, such a fuel reformer and another device that merely vaporizes fuel may be connected in series.

It is also possible to use the heat transferred from the combustion gases to the combustion chamber walls for preheating the fuel or as an auxiliary heat source for gasification.

In the embodiment shown in FIG. 5, the case where the engine 1 is a reciprocating four-stroke engine is shown, but the present invention can be implemented in exactly the same way with a two-stroke engine or a rotary engine.

Although the gasified fuel introduction valve 4 is a mushroom valve in FIG. 5, it may also be a rotary valve, a sleeve valve, etc.
Other types of valves perform exactly the same function.

In the case of an engine having an auxiliary combustion chamber, the opening of the gasified fuel introduction hole 3 to the combustion chamber 2 may be either the main chamber or the auxiliary chamber.

It is also possible to realize stratified combustion by providing the opening of the gasified fuel introduction hole 3 and the ignition plug close to each other.

If a reservoir tank is provided in the middle of the gasified fuel conduit 5, the introduction of the gasified fuel into the combustion chamber can be stabilized. In the case of claim 4, a check valve is provided between the reservoir tank and the fuel gasifier 8, or at the inlet of the reservoir tank, or at the gasified fuel outlet of the fuel gasifier 8, and the reservoir tank If the reformed gasified fuel is stored inside the engine, operation using the reformed gasified fuel is possible even when the engine is started.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the effect of the present invention on preventing a decrease in intake air amount. FIG. 2 is a schematic cycle diagram showing the principle of improving output and thermal efficiency according to the present invention. Figure 3 is a temperature-vapor pressure diagram of methanol. Figure 4 is a 98% decomposition temperature-pressure equilibrium diagram of methanol.
FIG. 5 shows an embodiment of a reciprocating four-stroke engine according to the present invention. Closed curve EFGHE: normal cycle, closed curve
EJKLMNE: Cycle according to the invention, 1: Engine,
2: Combustion chamber, 3: Gasified fuel introduction hole, 4: Gasified fuel introduction valve, 5: Gasified fuel conduit, 6: Exhaust gas passage, 7: Heat exchange wall, 8: Fuel gasifier, 9:
Fuel pump.

Claims (1)

[Claims] 1. A fuel gasification device that gasifies all or part of liquid fuel using the heat of exhaust gas, and the fuel that has been gasified in whole or in part is independent of the intake air passage. A method for supplying gasified fuel to an internal combustion engine in which the fuel is directly introduced into a combustion chamber through a route in which liquid fuel is supplied under pressure to the fuel gasification device,
A method for supplying gasified fuel to an internal combustion engine, characterized in that the fuel gasified in whole or in part by the means is introduced into the combustion chamber in the latter half of the compression stroke. 2. The method for supplying gasified fuel to an internal combustion engine according to claim 1, wherein the liquid fuel is added with water in advance. 3. The method for supplying gasified fuel to an internal combustion engine according to claim 1, wherein water is added to the liquid fuel before it is gasified. 4. Applying a catalyst to the liquid fuel or the fuel that has been gasified in whole or in part to cause a chemical reaction in part or all of the fuel so that its composition differs from that of the original fuel. A method for supplying gasified fuel to an internal combustion engine according to any one of claims 1 to 3, characterized in that: