JP2864526B2 - Dual fuel diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a diesel engine, and more particularly to a dual fuel diesel engine using a main fuel that does not self-ignite under compression and a sub-fuel excellent in self-ignition.

[Conventional technology]

From the viewpoint of reducing the pollution of diesel engines, double fuel supply using alcohol such as methanol or ethanol as the main fuel, light oil as the auxiliary fuel for ignition, and further injecting two fuels simultaneously from one fuel injection nozzle A double fuel diesel engine equipped with a device is already known (see Japanese Patent Application Laid-Open No. 58-206859).

[Problems to be solved by the invention]

However, the alcohol used in the diesel engine described above has a smaller calorific value per unit weight (or unit capacity) than that of light oil or gasoline (eg, methanol: 4800 Kcal / kg, light oil: 10280 Kcal / kg, gasoline:
10600 Kcal / kg), the same amount of work requires consuming more alcohol fuel than the fuel amount of a normal diesel engine that uses only light oil, and for vehicles with a limited fuel tank volume However, there is a problem that the burden on the driver is increased, for example, the cruising distance is shortened and the number of times of refueling is increased. In view of the above problems, the present invention has a larger work load in a dual fuel diesel engine that enables clean fuel than an engine that uses alcohol as a main fuel, and can reduce the burden on the driver as described above. The aim is to provide a diesel engine that can.

[Means for solving the problem]

A dual fuel diesel engine according to the present invention includes a main fuel nozzle for each cylinder, a fuel injection pump for pumping gasoline as main fuel to a main fuel injection nozzle of the cylinder at a fuel injection timing in the latter half of the compression stroke, and a main fuel nozzle. Pumping of each cylinder using the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder in order to make the injection nozzle wait for pumping light oil as the auxiliary fuel for ignition in advance of the fuel injection timing of the cylinder. And a sub-fuel injection nozzle that uses the main fuel pumping pressure of the fuel injection pump at the fuel injection timing of one of the cylinders to supply gasoline for forming a premixed mixture to the cylinder intake port. It is characterized by the following.

Further, another dual fuel diesel engine according to the present invention is a fuel injection method in which gasoline as main fuel is pumped to a main fuel injection nozzle of each cylinder at a fuel injection timing in the latter half of a compression stroke. In order to make the pump and the main fuel injection nozzle wait for pumping the light oil as the auxiliary fuel for ignition before the fuel injection timing of the cylinder in advance, the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder is used. In order to supply gasoline for forming a premixed gas mixture into the cylinder before the fuel is injected from the main fuel injection nozzle, the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder is provided. And a sub-fuel injection nozzle that uses a pumping pressure.

[Operation] In these two dual-fuel diesel engines, gasoline having a larger calorific value than alcohol is used as the main fuel, and in order to further increase the engine output, the intake pressure of the main fuel of the fuel injection pump is used to increase the intake pressure. Before the fuel is injected into the port or from the main fuel injection nozzle, gasoline is supplied into the cylinder, and before the fuel injection timing at which the main fuel and the auxiliary fuel are injected from the main fuel injection nozzle, air and air are introduced into the cylinder. A mixture with gasoline is formed.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. Note that the same components are denoted by the same reference numerals in common in each embodiment described later.

FIG. 1 shows a schematic configuration of a double fuel diesel engine according to the present invention, in which 1 is an engine main body, 2 is a fuel injection nozzle, and 3 is a distribution type fuel injection pump for supplying main fuel to the fuel injection nozzle 2. Numerals 4 and 4 denote pumps for discharging the auxiliary fuel by the injection pressure of the main fuel. These components are conventionally known in a diesel engine provided with a dual fuel supply device, and do not change at all in the present invention.

According to the present invention, in the diesel engine configured as described above, gasoline is used as the main fuel, and light oil is used as the auxiliary fuel. Therefore, gasoline is supplied from tank 5
The fuel is supplied to the injection pump 3 by the feed pump 6, and is driven by, for example, the injection pump 3 driven by a drive shaft (not shown) to the injection nozzle 2 of each cylinder (only one is shown in the figure) via the pressure feeder 4. Is discharged one after another.
Light oil is also supplied from the tank 7 to the pump 4 by the feed pump 8, and is further pumped to the injection nozzle 2 by the piston 9 in the pump 4 which is operated by the injection pressure of gasoline. The fuel supply to the injection nozzle 2 is configured such that the auxiliary fuel (light oil) is filled at the first injection timing and the main fuel is supplied at the next injection timing, as in the related art. Is supplied to the cylinder, the fuel is injected into the cylinder.

According to the present invention, a turbocharger (turbocharge) 10 is provided to ensure the same or higher output of a diesel engine using light oil as fuel. The turbocharger 10 includes a compressor 13 interposed in an intake passage 12 extending from the air cleaner 11 to the engine main body 1 and an exhaust passage 15 connected to the compressor 13 via a rotating shaft 14 and extending from the engine main body 1. And an exhaust turbine 16 for supercharging intake air with exhaust energy of the engine. The turbocharge 10 is provided with a wastegate valve 17 to prevent the boost pressure from rising excessively, as in the conventional case. The pressure for operating the actuator 18 is guided from the intake passage 12 downstream of the compressor 13. This pressure is also guided to the actuator 19 of the fuel injection pump 3 described above, and the amount of fuel supplied from the injection pump 3 is increased or decreased by the supercharging pressure.

Downstream of the exhaust passage 15 even more exhaust turbine 16 according to the present invention NO _X reducing catalyst 20 for the purpose of reducing the NO _X (nitrogen oxides) is provided. The NO _X reducing catalyst 20, for example as a ceramic (zeolite) a base material constituted by those coated copper, etc. thereon.

Hereinafter, the operation of the turbocharger 10, and NO _X reduction catalyst 20 is a feature of the present invention with reference to Figure 2.

FIG. 2 shows the smoke generation concentration with respect to the engine load when each fuel of light oil, methanol, ethanol and gasoline is burned in a diesel engine. Note that methanol, ethanol, and gasoline that do not self-ignite are burned with ignition assistance. As is clear from this figure, light oil with a large amount of carbon in the molecule generates smoke over the entire load range, while alcohol such as methanol and ethanol hardly generates smoke, and Gasoline located between alcohol and light oil produces almost no smoke in low and medium load ranges, but in high load ranges, the smoke concentration increases with increasing load. Therefore, the load fuel that can be operated without generating smoke in a diesel engine using gasoline as a main fuel and light oil as an auxiliary fuel is limited to a region excluding a high load, and there is a problem that the output is reduced as it is. However, according to the present invention, the output is improved because the turbocharger 10 is provided, and the high-density air is supercharged even if the amount of fuel injected from the injection nozzle 2 increases with an increase in load. Therefore, the operating fuel for completely fueling the carbon in the gasoline, that is, the load region in which no smoke is generated is expanded as shown by the dotted line in FIG.

Meanwhile the main fuel serving gasoline of the present invention, because the theoretical ratio is greater than the alcohol (lean side), the amount of the NO _X tends to increase than the generation amount of the diesel engine using alcohol as a main fuel. However, according to the present invention, by providing the above-described NO _X reduction catalyst 20 in the exhaust system, a sufficient reducing action can be performed even in the exhaust of a mixer having a lean air-fuel ratio, and thus NO _X can be reduced.

FIG. 3 shows a second embodiment of the present invention. This embodiment is intended to further increase the output of the dual fuel diesel engine described above.

That is, according to the example of the present invention, in addition to the configuration of FIG. 1, a further pumping device 21 is provided corresponding to each cylinder. The pump 21 is provided with a gasoline branch to the fuel injection pump 3 to be guided. A solenoid valve 23 communicating with the pipe 22 is provided in the middle of the branched pipe 22 when the engine is under a high load. Is done. The solenoid valve 23 is a switch linked to a control rack 24 for adjusting the fuel injection amount of the injection pump 3.
Operated by 25.

The pump 21 has the same structure as the pump 4 for discharging light oil by the injection pressure of gasoline.
Gasoline is discharged by the injection pressure of gasoline branched from the gasoline supply path to the fuel injection nozzle 3. The gasoline thus discharged from the pump 21 is injected into the intake passage 12 by one gasoline phosphorus injection valve 27 provided by a manifold 26 of the engine.
Therefore, in the illustrated four-cylinder diesel engine, the order of injection from the fuel injection nozzle 3 is assumed to be cylinder # 1 → # 3 → # 4
→ If # 2, fuel injected from gasoline injector 27
0 ° To cylinders with different crank angle phases (for example, cylinder # 1
(When the nozzle 3 is injected to the cylinder # 4), the air is sucked in advance at the same time as the intake air. As described above, the mixture of air and gasoline is supplied into the cylinder in advance, and the fuel is ignited and burned at the timing of fuel injection from the fuel injection nozzle 2, so that the ratio of air contributing to fuel in the diesel engine is obtained. That is, the air utilization is improved as compared with the previous embodiment, and the engine output is increased. This gasoline injection valve 27
Is performed only when the engine is under a high load by the opening and closing operation of the solenoid valve 23 described above.

FIG. 4 is a view similar to the above-described second embodiment, in which a gasoline injection valve 27 is provided for each cylinder, one for each cylinder.
FIG. 28 shows a third embodiment provided in 28, and the intention is to mix gasoline with the intake air in advance, as in the second embodiment.
It increases the air utilization rate during fueling. FIG. 5 shows the fourth
It shows the injection timing of the injection nozzle 2 and the gasoline injection valve 27 in the embodiment of the figure, and as is apparent from the figure,
Although the injection timing of both cylinders is executed in synchronization with each other, when the gasoline injection valve 27 injects gasoline, the intake valve of the corresponding cylinder is closed. Is waiting,
During this time, premixing of air and gasoline is performed. When the gasoline injection valves 27 are provided in each of the intake ports 28 in this manner, the variation in the amount of gasoline taken into each cylinder is reduced as compared with the second embodiment, so that the combustion state between the cylinders is more stabilized. Further, the gasification of the gasoline progresses due to the above waiting period, so that a more uniform preliminary mixture can be generated.

FIG. 6 differs from the second and third embodiments in that gasoline is directly injected into a cylinder (cylinder) so that air in the cylinder and gasoline are injected prior to injection of a double fuel (gasoline, light oil) from an injection nozzle. To increase the air utilization rate in the case of fuel.

That is, according to the present embodiment, as shown, gasoline branched from a gasoline supply path to an injection nozzle 2 provided in a different cylinder (eg, cylinder # 2) is directly injected into the cylinder (eg, cylinder # 1). One sub fuel nozzle 29 is provided for each cylinder. This sub injection nozzle 29
In FIG. 7, the valve opening pressure is set higher than that of the injection nozzle (main injection nozzle) 2 as shown in FIG. 7 due to the initial set load and the spring constant of the installed spring (not shown). The sub-injection nozzle 29 opens only at the time of high engine load with a large gasoline injection amount and high injection pressure from 3 to premix gasoline in the cylinder air. FIG. 8 shows the injection timing of each of the main injection nozzles 2 and the sub-injection nozzles 29 in the four-cylinder diesel engine.
This shows the timing when the operations are performed in the order of # 3 → # 4 → # 2. As is apparent from FIG. 8, the injection by the sub-injection nozzle 29 is performed in the latter half of the intake stroke of the installed cylinder and near the piston bottom dead center,
Until the injection timing of the double fuel (gasoline + light oil) executed after the elapse of about 180 ° crank angle, the air is mixed with the air in the cylinder to generate a premixed air. In this embodiment, since the sub injection nozzle 29 uses a part of the gasoline to the main injection nozzle 2 provided in the other cylinder, the supply amount of the fuel injection pump 3 is not changed as a whole. Not
There is no need to provide a mechanism (such as a pump) for gasoline supply and metering to the sub-injection nozzle 29, and the structure can be simpler than in the previous embodiment. Further, since the gasoline waiting time (premixing) time until ignition and fuel is relatively short, the degree of premixing does not progress so much, and the occurrence of knocking due to self-ignition of end gas can be suppressed.

In each of the above-described embodiments of the premixing, the gasoline injection may be electrically controlled.

〔The invention's effect〕

As described above, according to the present invention, since gasoline is used as the main fuel, the amount of work increases and the cruising distance of the vehicle increases as compared with the alcohol-mixed diesel engine. Additionally smoke generation and accompanying gasoline use, even for output reduction due to the limited load range operation, can be avoided by providing a supercharger, NO _X generated also suppressed by the installation of _the NO _x reduction catalyst can do. Further, the present invention uses light oil having ignition energy far greater than that of a spark plug as an ignition source, and uses gasoline having a higher cetane number (compression ignition index) than alcohol as a main fuel. Irrespective of the operating conditions of, stable ignition and combustion are always possible. Therefore, it is possible to operate with much better fuel efficiency than an engine having a spark plug.

Further, in the dual fuel diesel engine according to the present invention, before the fuel is injected from the auxiliary fuel injection nozzle or the main fuel injection nozzle that supplies the gasoline for forming the premixed mixture to the intake port of the cylinder, the fuel is injected into the cylinder. Before the fuel injection timing of each cylinder in which the fuel is injected from the main fuel injection nozzle, the main fuel and the auxiliary fuel injection nozzle for supplying the mixture forming gasoline are provided. An air-fuel mixture with the gasoline supplied from the auxiliary fuel injection nozzle is formed, so that the air utilization rate during combustion is improved and the engine output can be increased. The auxiliary fuel injection nozzle uses the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of one of the cylinders, or uses the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder. Therefore, gasoline supply for forming a premixed gas mixture can be realized by a single fuel injection pump, and the structure of the fuel injection system is not complicated.

[Brief description of the drawings]

FIG. 1 is a diagram showing an engine configuration showing a first embodiment of the present invention; FIG. 2 is a diagram showing the degree of smoke generation of various fuels; FIG. 3 is a diagram showing an engine configuration showing a second embodiment of the present invention; FIG. 5 is a diagram showing an engine configuration showing the third embodiment; FIG. 5 is a diagram showing fuel injection timing of the engine shown in FIG. 4; FIG. 6 is an engine configuration diagram showing a fourth embodiment of the present invention; The figure shows the relationship between the valve opening pressure and the load of the main and auxiliary injection nozzles of the engine shown in FIG. 6; FIG. 8 shows the fuel injection timing of the engine shown in FIG. 2 ...... fuel injection nozzle, 3 ...... fuel injection pump, 4 ...... pumping unit, 10 ...... supercharger (turbocharger), 20 ...... NO _X reduction catalyst.

Continuation of front page (56) References JP-A-58-206859 (JP, A) JP-A-59-131571 (JP, U) JP-A-61-32544 (JP, U) JP-A-58-8752 (JP) , U) Fully open sho 64-3032 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02M 43/00-43/02 F02M 63/00 F02M 45/00, 45/02 , 45 / 04,45 / 08 F02D 19 / 06,19 / 08 F02B 3/06

Claims (2)

(57) [Claims] 1. A main fuel injection nozzle for each cylinder, a fuel injection pump for pumping gasoline as main fuel to the main fuel injection nozzle of the cylinder at a fuel injection timing in a latter half of a compression stroke, and the main fuel injection nozzle. In order to cause the light oil serving as the auxiliary fuel for ignition to be pumped in advance before the fuel injection timing of the corresponding cylinder, the pumping of each cylinder using the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder is performed. And a sub-fuel injection nozzle that uses the main fuel pumping pressure of the fuel injection pump at a fuel injection timing of any one of the cylinders to supply gasoline for forming a premixed gas mixture to the cylinder intake port. A dual fuel diesel engine, comprising: 2. A main fuel injection nozzle for each cylinder, a fuel injection pump for pumping gasoline as main fuel to the main fuel injection nozzle of the cylinder at a fuel injection timing in a latter half of a compression stroke, and the main fuel injection nozzle. In order to cause the light oil serving as the auxiliary fuel for ignition to be pumped in advance before the fuel injection timing of the corresponding cylinder, the pumping of each cylinder using the pumping pressure of the main fuel of the fuel injection pump at the fuel injection timing of the other cylinder is performed. And a pumping pressure of the main fuel of the fuel injection pump at a fuel injection timing of another cylinder to supply gasoline for forming a premixed mixture into the cylinder before fuel is injected from the main fuel injection nozzle. A dual fuel diesel engine comprising: