JPH11246879A - Fuel, compressive ignition engine, and burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fuel causing no actuation failure of e.g. fuel injection valves due to abrasion and having considerable NOx-diminishing effect by mixing pressurized and liquefied dimethyl ether and a liquid hydrocarbon with each other in specified volume proportions. SOLUTION: This fuel is obtained by mixing (A) 30-60 vol.% of pressurized and liquefied dimethyl ether and (B) 70-40 vol.% of a liquid hydrocarbon with each other; wherein the component B may be a light oil or liquefied natural gas. Furthermore, when the dimethyl ether is incorporated with carbon dioxide previously, or CO2 -contg. crude dimethyl ether is used, the carbon dioxide is released when the dimethyl ether is depressurized and boils in air, thereby lowering the combustion temperature of this fuel, leading to suppressing NOx generation in its combustion, therefore being favorable. The 2nd objective compressive ignition engine is constructed in such a manner that this fuel is pressurized so as to liquefy the dimethyl ether and, in this state, is fed, from a fuel cylinder via a fuel feed pipe 14, to a fuel injection valve 16 and then injected into a fuel chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel containing dimethyl ether suitable for a compression ignition engine and the like, and a compression ignition engine and a burner using the same.

[0002]

2. Description of the Related Art Recently, dimethyl ether (hereinafter DME)
There has been proposed a diesel engine that uses gas oil instead of light oil.

[0003] This is because DME has a high cetane number, emits very little soot during combustion, and DME can be produced at low cost from coal, natural gas, biomass, waste plastics and the like. Not only that, it can be expected as a renewable fuel.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A diesel engine using as fuel can obtain almost the same output as when using diesel as fuel,
Unlike light oil, DME does not have lubricity, so that the movable part of the fuel injection valve wears out and becomes inoperable after a certain period of use.

[0005] As described above, DME has a high cetane number, so that it can be applied to conventional diesel engines without extensive remodeling of the engine excluding the fuel supply system, and has a C-C bond. Because it does not smoke,
While it is possible substantial reduction in particulate matter emissions, there is a problem that can not be reduced in NO _X.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a fuel, a compression ignition engine, and a burner, which do not cause inoperability of a fuel injection valve or the like due to wear. .

[0007] In addition, large DME fuel of the NO _X reduction effect,
It is an object of the present invention to provide a compression ignition engine and a burner using the same.

[0008]

According to the present invention, a fuel is formed by mixing 30-60% by volume of dimethyl ether liquefied by pressurization and 70-40% by volume of liquid hydrocarbon, The above object is achieved.

The liquid hydrocarbon may be gas oil or liquefied natural gas.

Further, carbon dioxide may be previously contained in the dimethyl ether, or the dimethyl ether containing carbon dioxide may be used as crude dimethyl ether before purification.

According to the invention relating to a compression ignition engine, the fuel is
A fuel supply pipe supplied by a fuel pump in a state where the dimethyl ether is pressurized to a pressure at which the dimethyl ether is liquefied, and a fuel injection valve for injecting the fuel in the fuel supply pipe into a combustion chamber, This achieves the above object.

Further, an accumulator for storing the fuel under a pressure at which the dimethyl ether is liquefied may be arranged at the fuel supply line and a fuel inlet to the fuel supply line.

Further, an additional fuel supply device for additionally supplying only the liquid hydrocarbon to the fuel supply line, and a supply amount of hydrocarbons from the additional fuel supply device to the fuel supply line after starting the engine. A control device that controls the amount of liquid hydrocarbons in the fuel injected into the combustion chamber to exceed 50% and to be 50% or less after the warm-up operation, at least when the engine is started, until the warm-up operation is completed. And may be provided.

Further, an exhaust gas recirculation device for circulating a part or all of the exhaust gas discharged from the combustion chamber to an intake system for the combustion chamber may be provided.

The invention relating to a burner achieves the above object by a burner which mixes and burns the fuel described above with air.

Also, in the burner, a cylindrical outer nozzle having an outer nozzle opening at a front end, and a coaxially disposed inside the outer nozzle and having a front end concentric with the outer nozzle opening, And an inner nozzle having an inner nozzle opening that is opened at a position close to the inner side in the axial direction, a fuel supply device that supplies the fuel in a liquefied state to the inner nozzle, and a fuel supply device that is provided in the inner nozzle and is supplied. A pressure reducing device for boiling the fuel under reduced pressure, wherein the fuel at least partially vaporized by the reduced pressure boiling is ejected from the inner nozzle opening, and at least a part of the fuel and the air are discharged from the inner nozzle opening. The mixture may be mixed at a position between the outer nozzle opening and the outer nozzle opening.

In the present invention, since hydrocarbon is mixed with dimethyl ether, the fuel injection valve and the like are lubricated by the hydrocarbon, and malfunctions due to wear can be prevented.

In addition, carbon dioxide is preliminarily contained in dimethyl ether, or crude dimethyl ether containing carbon dioxide is released. When this is boiled under reduced pressure in air, carbon dioxide is released, and this release is an endothermic reaction. ,
The combustion temperature is lowered, it is possible to suppress the NO _X generation by combustion.

Further, by using dimethyl ether as crude dimethyl ether before purification, the production cost can be greatly reduced.

Further, in the compression ignition engine using the fuel composed of dimethyl ether, the lubricating action of the liquid hydrocarbon and the lowering of the combustion temperature can be expected as described above. The exhaust gas can be recirculated to the intake system.

When a fuel containing dimethyl ether as described above is used for a burner, when the liquefied dimethyl ether is mixed with air, the dimethyl ether is boiled under reduced pressure to form fine particles and can be efficiently and completely burned.

The liquid dimethyl ether is boiled under reduced pressure in advance, and is mixed with air in a state where at least a part thereof is in a gaseous state, so that the fuel can be mixed well with the air without using a conventional atomizer or the like. be able to.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a compression ignition engine according to the present invention will be described below with reference to the drawings. Here, the fuel will be described in detail together with the embodiment of the compression ignition engine.

As shown in FIG. 1, a compression ignition engine 10 according to an embodiment of the present invention has an engine body 12 having the same configuration as that of a normal diesel engine, and the engine body 12 has a fuel according to the present invention. Supply system 1 for supplying fuel
4 and a control device 18 for controlling the fuel injection valve 16 and the like in the fuel supply system 14.

The fuel supply system 14 includes a fuel cylinder 20 for pressurizing and containing a fuel containing DME so as to be in a liquefied state at room temperature, and one or more fuel injection valves 16 provided in the engine body 12. A common fuel supply path,
A common rail 22 also serves as an accumulator, a fuel pump 24 for circulating fuel from the fuel cylinder 20 to a circulation path 24A, and a plunger pump 26 for pressurizing the fuel in the circulation path 24A and injecting the fuel into the common rail 22. ing.

Reference numeral 27A in FIG. 1 denotes a pressure regulating valve, which returns a part or all of the fuel discharged from the plunger pump 26 to the circulation path 24A when the pressure in the common rail 22 exceeds a set value. Has been.

Reference numeral 28B in FIG. 1 denotes a relief valve that discharges fuel to the circulation path 24A when the pressure in the common rail 22 exceeds a set value, and
This is to maintain the pressure in the chamber below a certain value.

The fuel in the fuel cylinder 20 is prepared by mixing dimethyl ether in a pressurized and liquefied state with light oil in a volume ratio of about 50%.
It is a mixture of 50 pairs. In addition, dimethyl ether is crude dimethyl ether containing carbon dioxide before purification.

The control device 18 comprises, for example, a CPU so that the fuel injection valve 16 can optimally control the fuel injection amount and the fuel injection timing.

Here, the common rail 22 applies pressure to the fuel contained within the elastic limit of the metal constituting the common rail 22. The pressure value can maintain dimethyl ether in a liquefied state in an environment near the engine. Pressure. For example, when the thermal environment of the common rail 22 is in a normal temperature range, the pressure is set to 1.8 to 4 MPa. On the other hand, the nozzle opening pressure of the fuel injection valve 16 is 8 to 10 MPa, and the fuel injection timing of the fuel injection valve 16 is such that the injection start timing is such that the crank angle with respect to the top dead center is −17 ° to −5 ° (C
AbTDC) was optimal from the viewpoint of fuel consumption rate.

Compression ignition engine 1 using fuel as described above
At 0, since the supplied fuel contains light oil having lubricity, the fuel injection valve 16, the fuel pump 24,
The plunger pump 26 and the like are lubricated, and there is no occurrence of wear, inoperability or the like due to insufficient lubrication.

On the other hand, when the compression ignition engine 10 was operated with DME only (without addition of a lubricity improver, etc.) under substantially the same conditions as described above, the rotation speed and the output fluctuated after 30 minutes from the start. And the agency stopped. Thereafter, starting was disabled, and wear marks due to insufficient lubrication were observed on movable parts of the injection nozzle and the spray pump.

In the case of crude DME, carbon dioxide is usually contained, and when this is sprayed into the combustion chamber, carbon dioxide precipitates during boiling under reduced pressure.

This carbon dioxide deposition is an endothermic reaction,
The fuel injected into the combustion chamber is cooled in the spray,
Due to the high specific heat of carbon dioxide, the combustion temperature decreases,
NO _XWas suppressed.

Further, in the case of DME, as described above, the valve opening pressure of the fuel injection valve 16 is less than half of the nozzle opening pressure (normally about 20 Mpa) during light oil operation, and the fuel is pressurized. The pressure rise time is earlier than in the case of light oil operation. Therefore, compared to light oil, the actual injection start timing can be made earlier, and due to the good ignitability of the DME, the rate of pressure increase in the combustion chamber can be made smaller than in light oil operation and the maximum pressure can be made higher. it can. Further, by setting the fuel injection start timing to −5 ° CAbTDC, the maximum pressure in the combustion chamber can be reduced as compared with the case of light oil operation. Therefore, the weight of the engine body 12 can be reduced.

As described above, the fuel injection start timing is set to-
The heat consumption rate (SE
C) is a slight increase over -17 ° CAbTDC. Therefore, the optimal injection start timing from the viewpoint of the heat consumption rate is between -17 ° and -5 ° CAbTDC.

Further, the calorific value of DME contained in the fuel is about 70% of that of light oil, and about 50% of DME and light oil
In this case, the calorific value is about 85% of that of light oil.

Accordingly, in order to obtain an output equivalent to that of light oil, the fuel injection amount per injection is about 18% less than that of light oil.
Since the amount is increased and the nozzle valve opening pressure is about half of that in the case of light oil, the fuel injection time is about twice that in the case of light oil operation, but the combustion period is equal to or slightly shorter than in the light oil operation.

This is because the ignition temperature of the DME is as low as 235 ° C., the boiling point is as low as −25 ° C., and a longer injection period disturbs the combustion field and has an effect of increasing energy.

Since the DME contained in the above fuel has no CC bond, it has no smokeless combustion, that is, low smoke emission and particulate matter emission, and low PHC (unburned hydrocarbon).

In particular, even if the injection start timing is greatly changed, the emission of PHC is about half of that in the case of the light oil operation, and the HC which is also generated in a large amount of the methanol which smokelessly burns is also generated.
Low HO emissions.

As described above, when PHC, smoke, and particulate matter are small in the exhaust gas from the engine body 12, the compression ignition engine 10A according to the second embodiment of the present invention shown in FIG. An exhaust gas recirculation device (EGR device) 28 that supplies exhaust gas from the exhaust system to the intake system can be provided.

The EGR device 28 includes an EGR pipe 34 for allowing a part of the exhaust gas to recirculate from the exhaust pipe 30 to the intake pipe 32, and an EGR pipe 3.
4 and an EGR valve 36 for controlling the amount of exhaust gas recirculated to the intake system. The EGR valve 36 is controlled by the control device 18, but the details of the control are omitted.

Since the other structure is the same as that of the compression ignition engine 10 shown in FIG. 1, the description will be omitted by giving the same reference numerals to the same parts.

As shown in FIG. 2, by providing the EGR device 28, the exhaust gas can be recirculated to the intake system, and the combustion temperature in the engine body 12 can be further reduced. Therefore, NO _X contained in the exhaust gas can be significantly suppressed.

The fuel cylinder 2 in the example of the above embodiment
0 contains crude dimethyl ether and light oil at a rate of 50% each, but when starting the engine, it is preferable to increase the rate of light oil having a large calorific value and supply it to the engine.

In this case, for example, a light oil supply system 38 for independently supplying only light oil to the common rail 22 like a compression ignition engine 10B according to a third embodiment of the present invention shown in FIG. During the time from the start of the engine to the end of the warm-up operation, for example, light oil is additionally supplied from the light oil supply system 38 into the common rail 22 to increase the ratio of passing through the fuel to start the engine. It is preferable to perform the warm-up operation efficiently.

The light oil supply system 38 comprises a pump 38A and a light oil tank 38B, and the pump 38A is controlled by the controller 18.

At the end of the warm-up operation or after a lapse of a predetermined time from the start, the additional supply of light oil from the light oil supply system 38 is stopped, and fuel is supplied only from the fuel cylinder 20.

As described above, the fuel used in the compression ignition engine of the present invention is a mixture of DME and light oil at a ratio of 50%, but the present invention is not limited to this. The fuel to be mixed may be a liquid hydrocarbon having lubricity.

For example, a liquefied petroleum gas containing propane or butane, etc. may be used.
May be mixed.

Further, the DME is not limited to crude DME, but may be purified DME, purified DME with carbon dioxide absorbed, or the like.

The mixing ratio of DME and liquid hydrocarbon is 30-60% by volume and 70-70% by volume.
The range may be 40%.

Further, in the compression ignition engine, the fuel is supplied to the fuel injection valve via the common rail. However, the present invention is not limited to this, and the fuel is supplied to the fuel injection valve. In the meantime, any pressure that can maintain the pressure at which the fuel is liquefied may be used.

Therefore, the common rail (accumulator)
The present invention is not limited to this, and when used, an accumulator other than the common rail may be provided near the fuel injection valve.

Next, an embodiment of the burner shown in FIG. 4 will be described.

The burner 40 has a cylindrical outer nozzle 42 provided with an outer nozzle opening 42A at the tip, and is disposed coaxially inside the outer nozzle 42, and has a tip concentric with the outer nozzle opening 42A. And
An inner nozzle 44 provided with an inner nozzle opening 44A which is opened at a position close to the inner side in the axial direction, a fuel supply device 46 for supplying the fuel in a liquefied state toward the inner nozzle 44, and provided in the inner nozzle 44; A decompression device 52 for depressurizing and boiling the supplied fuel, wherein a part or all of the fuel vaporized by depressurization boiling is jetted from the inner nozzle opening 44A to form an annular ring between the outer nozzle 42 and the inner nozzle 44. The air is mixed with the air supplied to the space 43 and jetted from the outer nozzle opening 42A, and the jet flow is ignited and burned.

The reference numeral 48 in FIG.
5 shows an air pump for pressurizing and supplying air to an annular space 43 between the inner space 44 and the inner nozzle 44. In the fuel supply device 46, a fuel obtained by mixing DME and light oil by 50% is stored in a liquefied state, and this is supplied to the inner nozzle 4.
4 includes a fuel cylinder 50 and an on-off valve 51 for supplying to a base end opposite to the inner nozzle opening 44A.

The inner nozzle 44 includes a nozzle portion 45A having the inner nozzle opening 44A and a nozzle portion 4A.
An intermediate cylinder portion 45B to which the base end of 5A is screwed, and a fuel supply pipe 45 screwed to the base end side of the intermediate cylinder portion 45B
C, and the fuel passage 5 through these centers.
4 are formed.

The pressure reducing device 52 includes a fuel reservoir 56 formed in the middle of a fuel passage 54 and a fuel reservoir 56.
The fuel reservoir 56 is divided into the inner nozzle opening 44A side and the fuel cylinder 50 side, and is provided with a pressure reducing plate 58 which communicates these with a number of small holes 58A.

The fuel reservoir 56 is provided with the intermediate cylindrical portion 45B.
The pressure reducing plate 58 is formed between the base end of the fuel supply pipe 45C and the front end of the fuel supply pipe 45C. The pressure reducing plate 58 is screwed to the outside of the base end of the intermediate pipe part 45B.
The pressure reducing plate 58 is screwed to the outer periphery at the base end side.

As shown in an enlarged view in FIG. 5, the pressure reducing plate 58 has a truncated cone shape protruding in the base end direction of the inner nozzle 44, and is formed of a liquid supplied from the fuel cylinder 50 to the base end of the inner nozzle 44. When the fuel exits through the pores 58A in the direction of the inner nozzle opening 44A, the pressure is reduced to boil.

The reference numeral 60 in FIG.
The jet ring attached to the tip of the nozzle part 45A so as to form 4A is shown.

The outer nozzle 42 includes a nozzle portion 43A in which an outer nozzle opening 42A is formed, and a cylindrical portion 43B to which the base end of the nozzle portion 43A is screwed. Air supply pipe 49 for introducing air from air pump 48 through air joint 49A
B is screwed.

The reference numeral 62 in FIG.
7 shows centering attached and fixed between the nozzle portion 43A and the cylindrical portion 43B when they are screwed together. The centering 62 supports the vicinity of the tip of the intermediate cylindrical portion 45B of the inner nozzle 44 from the outside, and positions the inner nozzle 44 coaxially with the outer nozzle 42.

The centering 62 is connected to the intermediate cylinder 4
The mounting groove 63 extends in the axial direction from the tip of 5B and is bent at a right angle to the mounting groove 63 at an angle range of about 30 °.
Inserted in the axial direction and rotated in the circumferential direction, it is fitted in the intermediate cylindrical portion 45B.

The outer nozzle 42 having the inner nozzle 44 therein is disposed on the center axis of an outer air supply pipe 66 to which air from an air blower (not shown) is supplied.

In this burner 40, liquefied DME
When the fuel containing gas oil flows out of the pores 58A of the pressure reducing plate 58 in the fuel reservoir 56, the fuel boils under reduced pressure and becomes vaporized and fine particles, and is ejected from the jet ring 60 at the tip of the inner nozzle 44 with pressure. At this time, the air is satisfactorily mixed with the air fed from the air pump 48 and ignites and burns.

In this combustion, when the fuel and the DME gas lower the temperature of the spray due to the heat of vaporization, and when the DME is crude DME containing carbon dioxide before purification, the temperature is lowered by an endothermic reaction in which carbon dioxide is released. brought, whereby the combustion temperature is lowered, generation of the NO _X is suppressed.

The combustion flame ejected from the outer nozzle 42 is further burned by being mixed with the air from the outer air supply pipe 66.

The pressure reducing device 52 in the burner 40 for boiling the fuel under reduced pressure is composed of a pressure reducing plate 58 provided with fine holes 58A, but the present invention is not limited to this. Decompression means may be used.

For example, a pressure reducing device 68 having another structure as shown in FIG. 6 may be used.

The decompression device 68 includes an intermediate tube 45 shown in FIG. 4 and an intermediate portion 45D.
45F and an intermediate portion 45D and both ends 4
5E and 45F, a pair of swirling flow forming blades 70A and 70B for forming swirling flows in the opposite directions to the fuel flowing through the fuel passage 54 are arranged.

Each of the swirling flow forming blades 70A and 70B is the same as that shown in FIG.
As shown in the figure, 8 at equal angular intervals of 45 ° in the circumferential direction.
Of the fuel passage 5
4, when viewed from the axial direction, the phase in the circumferential direction is shifted by 22.5 °.

[0075]

According to the present invention, as described above, when the fuel is used for a compression ignition engine, wear of movable parts such as fuel injection valves can be suppressed, stable operation can be maintained, and smokeless combustion can be maintained. , has an excellent effect that it is possible to lower NO _X combustion.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a compression ignition engine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a second example of the embodiment of the compression ignition engine.

FIG. 3 is a block diagram showing a third example of the embodiment.

FIG. 4 is an enlarged cross-sectional view including a partial block diagram showing a burner according to an embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view showing the main part.

FIG. 6 is a sectional view showing a second example of the embodiment.

FIG. 7 is an enlarged side view showing the main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Compression ignition engine 12 ... Engine main body 14 ... Fuel supply system 16 ... Fuel injection valve 18 ... Control device 20 ... Fuel cylinder 22 ... Common rail 24 ... Fuel pump 26 ... Plunger pump 28 ... EGR device 38 ... Light oil supply system 40 ... Burner 42 ... outer nozzle 42A ... outer nozzle opening 44 ... inner nozzle 44A ... inner nozzle opening 46 ... fuel supply device 48 ... air pump 50 ... fuel cylinder 52, 68 ... pressure reducing device

Claims (11)

[Claims] 1. A pressure-liquefied dimethyl ether of 30 to 60% by volume and a liquid hydrocarbon of 70 to 4% by volume.
0% mixed fuel. 2. The fuel according to claim 1, wherein the liquid hydrocarbon is light oil. 3. The fuel according to claim 1, wherein the liquid hydrocarbon is liquefied natural gas. 4. The fuel according to claim 1, wherein the dimethyl ether contains carbon dioxide in advance. 5. The fuel according to claim 4, wherein the dimethyl ether containing carbon dioxide is crude dimethyl ether before purification. 6. The fuel according to claim 1, wherein the fuel is pressurized to a pressure at which the dimethyl ether is liquefied.
A fuel supply line supplied by a fuel pump, a fuel injection valve for injecting the fuel in the fuel supply line into a combustion chamber,
A compression ignition engine comprising: 7. The fuel supply system according to claim 4, wherein the fuel is supplied to one of the fuel supply line and a fuel inlet to the fuel supply line.
A compression ignition engine, comprising an accumulator for storing the dimethyl ether under a pressure at which the dimethyl ether is liquefied. 8. The fuel supply system according to claim 6, wherein an additional fuel supply device for additionally supplying only the liquid hydrocarbon to the fuel supply line, and a hydrocarbon supply from the additional fuel supply device to the fuel supply line. The amount of liquid hydrocarbons in the fuel injected into the combustion chamber is at least 50% between the time of engine start and the end of warm-up operation, at least at the time of engine start, and is 50% or less after warm-up operation. And a control device for controlling the compression ignition engine. 9. The exhaust gas recirculation device according to claim 6, 7 or 8, wherein a part or all of the exhaust gas discharged from the combustion chamber is circulated to an intake system to the combustion chamber. Characteristic compression ignition engine. 10. A burner characterized in that air is mixed with the fuel of claim 1 to 5 and burned. 11. The outer nozzle according to claim 10, wherein the outer nozzle has a cylindrical outer nozzle at a tip thereof, and is disposed coaxially inside the outer nozzle and concentric with the outer nozzle opening at the tip. And an inner nozzle having an inner nozzle opening that is opened at a position close to the inner side in the axial direction, a fuel supply device that supplies the fuel in a liquefied state to the inner nozzle, and a fuel supply device that is provided in the inner nozzle and is supplied with the fuel. And a decompression device for decompressing and boiling the fuel, wherein the fuel at least partially vaporized by the decompression boiling is ejected from the inner nozzle opening, and at least a portion of the fuel and air are discharged from the inner nozzle. A burner characterized in that mixing is performed at a position between the opening and the outer nozzle opening, and the mixture is ejected from the outer nozzle opening.