JPS6149497B2 - - Google Patents

Description

[Detailed Description of the Invention] Numerous attempts have been made in basic research to use auxiliary fuels in conjunction with the main fuel in diesel engines, but further research is being pursued as applied research at the commercialization level. We are in a situation where we need to

In terms of basic research, one example is already well-known research in which an ordinary diesel engine is made to additionally inhale liquefied petroleum gas (LPG) as a gaseous auxiliary fuel to increase output and improve thermal efficiency. Since the main focus of these studies is to elucidate the fundamental phenomena caused by the combined use of LPG, there is a need for further research from the commercialization and development stage. For example, in an automobile diesel engine where the load and engine speed change frequently,
It is required to supply gaseous auxiliary fuel that is adapted to the operating conditions from time to time.

The present invention has been provided based on the above-mentioned viewpoint, and is not intended to add gaseous auxiliary fuel to a normal diesel engine, but to improve the maximum oil injection at the maximum load when operating with only main fuel. quantity 10-30
The basic idea is to supply an appropriate amount of gaseous auxiliary fuel obtained from liquefied petroleum gas in accordance with the range of fuel injection reduction, reducing exhaust black smoke, increasing output, and improving fuel efficiency. The aim is to obtain favorable results in various respects such as reduction of NOx and reduction of NOx.

Hereinafter, the present invention will be explained in detail with reference to the embodiments shown in the drawings. Figures 1 and 2 show the first to third
This embodiment corresponds to the invention, and 1 is a normal diesel engine, which includes an intake pipe 3 forming an intake passage 2, an air cleaner 4, an exhaust pipe 5, a fuel injection pump 6, and the like.

The gaseous auxiliary fuel in this embodiment is obtained from liquefied petroleum gas (LPG), and the LPG tank 7, vaporizer 8, pressure regulating valve 9, and electromagnetic shut-off valve 10
connected by the auxiliary fuel pipe 11 in the order of
The end of the pipe 11 opens into the intake passage 2. The acceleration device associated with the fuel injection pump 6 (the communication relationship is not shown) is illustrated in the form of an automobile accelerator pedal 12, and has a switch that closes when the amount of depression of the pedal 12 reaches a certain value. 13 are installed. An oil injection amount reducing means 14 is attached to the fuel injection pump 6 in order to reduce the maximum oil injection amount at maximum load by 10 to 30%. Connection 1
5, battery 16 electromagnetic on-off valve 10, switch 13
and oil injection amount reducing means 14 are connected in series.

The oil injection amount reducing means 14 is for reducing the maximum oil injection amount by 10 to 30% at maximum load, and may be any device that guarantees a normal oil injection amount outside of such a load range. An example is shown in Figure 2. An electromagnetic coil 20 is housed in a casing 19 fixed to a stationary member 18, and an iron core 21 penetrating the inside thereof protrudes outside the casing 19.
A stopper piece 22 is fixed to one end of the iron core 21, and a male screw 23 is provided at the other end to which a stopper disc 24 is screwed. The stopper disc 24 is fixed with a lock nut 25 after adjusting its position, and the stopper piece 2
A stopper flange 26 is also provided on the second side. Furthermore, a spring 2 installed inside the casing 19
7 sets the original position when not in operation. Reference numeral 28 denotes an oil injection amount control rack of the fuel injection pump 6, which is disposed coaxially with the iron core 21, with a stopper piece 22 facing an end surface of the rack 28.

Since the pedal 12 does not close the switch 13 in the range below the maximum load, the solenoid on-off valve 1
0 is not energized and the gaseous auxiliary fuel is cut off. Therefore, in this load band, the engine is operated only with diesel fuel, which is the main fuel, and normal oil injection amount control is performed.

When the pedal 12 is depressed enough to reach the maximum load range, the switch 13 is closed.
The electromagnetic on-off valve 10 and the electromagnetic coil 20 are energized, and gaseous auxiliary fuel is injected into the intake passage 2. When the iron core 21 is excited by the electromagnetic coil 20, the iron core 21
moves to the right while compressing the spring 27,
The amount of rightward movement of the iron core 21 is determined by the stopper disk 24 abutting against the casing 19. Due to this rightward movement, the position of the rack 28, which would normally reach point A, is suppressed to point B. In other words, the distance between a and b is an oil injection reduction stroke of 10 to 30%. Become. As is clear from the drawings, by adjusting the position of the stopper disk 24, the distance between a and b can be changed, and thereby the oil injection reduction rate can be set to an optimum value.

The liquefied gas from the LPG tank 7 is vaporized by the vaporizer 8 and further pressure regulated by the pressure regulating valve 9.The pressure of the gaseous auxiliary fuel must be set to a value higher than that of the intake passage 2 for constant supply. It has been confirmed through experiments that it is favorable for In this case, since the pressure in the intake passage 2 is below atmospheric pressure, it is appropriate to set the pressure of the vaporized auxiliary fuel within the range of 0 to 0.5 kg/cm ² . In addition, when supplying a fixed amount, it is preferable to set the diameter of the supply nozzle to a predetermined value.
This supply nozzle is attached to the opening to the intake passage 2.

As will be described in detail in the experimental results below, a suitable weight ratio of the gaseous auxiliary fuel to the total fuel was 10 to 25%.
As considered from FIG. 6, this is a percentage that is judged to be appropriate in relation to the concentration of exhaust black smoke, fuel consumption rate, average effective pressure, etc.

The embodiment described above intentionally reduces the maximum oil injection amount at maximum load, supplies an appropriate amount of gaseous auxiliary fuel in correspondence with this reduction band, and pushes this supply into the intake air. This was proposed as a way to realize a constant supply amount regardless of the engine speed. However, even in the maximum load state, it has been found that it is functionally more preferable to supply the fuel in an increasing amount in correlation with the engine speed at that time, so this is positioned as the fourth invention.
FIG. 3 is a drawing of an embodiment in that case, and the same components as in the previous embodiment are given the same reference numerals and detailed explanations are omitted.

That is, a displacement correlated to the engine speed is applied to the flow control valve 29 installed in the pipe 11, and the governor 3 is used as a speed correlation means.
0 is used. The governor 30 is connected directly or indirectly to the output shaft of the engine, and as shown in the figure, the higher the engine speed, the greater the opening degree of the flow control valve 29.

Therefore, for example, when the maximum load is reached in the medium speed range, the amount of gaseous auxiliary fuel is set accordingly, and when the maximum load is reached in the high speed range, the amount of gaseous auxiliary fuel is set to match the maximum load in the medium speed range. Also, a large amount of gaseous auxiliary fuel will be supplied. Of course, as is clear from FIG. 3, the maximum oil injection amount at maximum load is reduced within the range of 10 to 30% by the oil injection amount lowering means 14.

Next, the experimental results are as follows. The test engine was a four-cylinder cycle swirl diesel engine with a cylinder volume of 2500 c.c.
The main fuel is commercially available light oil, and the gaseous secondary fuels are ethane and ethylene (2.7%) and propane (2.7%).
Household propane gas consisting of 68.5% propylene, 12.5% propylene, and 16.3% butane (by volume) was used.

In diesel engines, problems such as exhaust black smoke, output problems, fuel efficiency, NOx, etc. have a large impact in the high load range, especially during full load operation, and as in the first invention, the load range where problems occur. Since the main fuel is supplied in the low range and the gaseous auxiliary fuel is supplied in response to the problem, it is possible to reliably take measures against the problem range. Research has also been done to supply gaseous auxiliary fuel additionally to the main fuel even outside the high load range, but it is most effective to supply gaseous auxiliary fuel near the full load range in correlation with the amount of main fuel. It is determined that the

If the auxiliary fuel is supplied in the form of a liquid, the metering amount is relatively large, but if it is supplied in the form of a gas as in the present invention, sufficient consideration must be given to setting the supply amount. In the second invention, since the gaseous auxiliary fuel is supplied under a pressure condition higher than that of the intake passage, the expected supply amount can be ensured by selecting the supply pressure and the supply nozzle portion.

In the case of automobile diesel engines, the engine speed and maximum load appear in a complex interplay depending on the road and loading conditions, but diesel engines for power generation and winches do not have the same harsh conditions as automobiles. It is not a condition. Therefore, in the latter case, such as for power generation, it is sufficient to supply a fixed amount of gaseous auxiliary fuel regardless of the engine speed as in the third invention, and in the former case, the fourth invention may be used as needed. It is preferable to supply the fuel in increasing amounts in relation to the engine speed.

Each improvement item will be explained below in relation to the various experimental results shown in FIGS. 4 to 7.

(1) Exhaust black smoke concentration The black smoke concentration becomes significantly thicker in the high load range, especially near full load, but by reducing the amount of main fuel injection in that range by 10 to 30%, , has been sufficiently improved. The black smoke density in each figure is expressed in terms of reflectance, and when looked at in relation to the load, the density values are almost the same as those in the light and medium load ranges, as shown in Figure 4.
In addition, when looking at the relationship with the injection start time, as shown in Figure 5, the black smoke concentration decreases as the start time becomes later, and this point has good meaning in relation to the NOx low range described later. ing. At the same time, a considerable decrease in concentration is observed compared to when only the main fuel is used. Furthermore, in relation to the supply amount of gaseous auxiliary fuel shown in FIG. 6, a value of 10% or more is good.

(2) Regarding output improvement When observed from the perspective of average effective pressure, it has been improved as shown in Figures 5 and 6. As is clear from the indicator diagram in Figure 7, when using only the main fuel, the ignition delay appears to be quite large, but when combined with the gaseous auxiliary fuel, the ignition delay becomes significantly large. This is considered to be due to the fact that the combustion time is shortened, thereby prolonging effective combustion.

(3) Regarding fuel consumption rate The fuel consumption rate is 10 to 20% in the high load range, when the injection start time is around 20° to 10° before top dead center, and when using gaseous auxiliary fuel.
Improvements have been made in the vicinity. This is judged to be an effective factor in reducing the maximum amount of oil injected at maximum load by 10 to 30% and using excess air for combustion of gaseous auxiliary fuel. The degree of air utilization when only the main fuel is used is generally low, and it is normal for 10 to 20% of the intake air to be exhausted unused. As a result, the combined main and sub fuel efficiency improves. In addition, by shortening the ignition delay, the effective amount of work increases, which helps improve fuel efficiency.

(4) Regarding NOx NOx in diesel engines is generally dealt with mainly by delaying the start of injection. However, if this delay is excessive
Even if it is favorable for NOx low range,
This becomes impractical because the ignition delay increases, resulting in a decrease in effective average pressure, increase in knocking and noise, generation of black smoke, and deterioration in fuel efficiency. If the ignition delay is significantly shortened by supplying a gaseous auxiliary fuel as in the present invention, it will be possible to delay the injection start timing beyond the conventional value, promoting the reduction of NOx and reducing the side effects associated with it. It can be supplemented.

To summarize the points mentioned above,
When a gaseous secondary fuel such as LPG is supplied to the engine together with intake air, it produces intermediate reactants such as aldehydes during the compression stroke, which accelerates the ignition combustion of the main fuel and eliminates excess air oxygen in the diesel engine. This can be reflected in the output improvement aspect. At the same time, it can improve combustion conditions, prevent the generation of large amounts of black smoke, and optimally adjust the injection timing of the main fuel, which can contribute to reducing NOx and improving thermal efficiency.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional side view of the oil injection amount reducing means, Fig. 3 is a schematic diagram showing another embodiment, and Figs. 4 to 7 are experiments. It is various line diagrams which show a result.

Claims (1)

[Claims] 1. The maximum amount of oil injected at maximum load when operating only with main fuel is reduced by 10 to 30%, and a gaseous sub-fuel obtained from liquefied petroleum gas, for example, is A fuel supply method for a diesel engine that uses a gaseous auxiliary fuel, characterized by supplying an appropriate amount of fuel. 2. Reduce the maximum amount of oil injection at maximum load by 10 to 30% when operating with only main fuel, and supply an appropriate amount of gaseous auxiliary fuel obtained from liquefied petroleum gas, for example, in response to the oil injection reduction band. 1. A method for supplying fuel to a diesel engine in combination with a gaseous auxiliary fuel, characterized in that the gaseous auxiliary fuel is supplied into the intake air under conditions of a higher pressure than the pressure in the engine intake passage. 3. Reduce the maximum amount of oil injection at maximum load by 10 to 30% when operating with only main fuel, and supply an appropriate amount of gaseous auxiliary fuel obtained from liquefied petroleum gas, for example, in response to the oil injection reduction band. 1. A method for supplying fuel to a diesel engine using a gas auxiliary fuel, characterized in that the method supplies a constant amount of the gas auxiliary fuel regardless of engine speed. 4. Reduce the maximum amount of oil injection at maximum load by 10 to 30% when operating with only main fuel, and supply an appropriate amount of gaseous auxiliary fuel obtained from liquefied petroleum gas, for example, in response to the oil injection reduction band. 1. A method for supplying fuel to a diesel engine in combination with a gaseous auxiliary fuel, characterized in that the gaseous auxiliary fuel is supplied in increasing amounts in correlation to engine speed.