JP4579077B2 - Diesel engine combustion method - Google Patents

Description

The present invention relates to a combustion how the diesel engine with water and mixed water mixed fuel oil fuel.

  Reduction of nitrogen oxides and particulate matter discharged from a diesel engine is desired from the viewpoint of reducing environmental impact. As one of the methods, it is known that water is mixed with fuel and used in a diesel engine. In this method, the soot generation in the particulate matter can be reduced by diluting the fuel with an inert substance, and the generation of nitrogen oxides is suppressed by lowering the combustion temperature.

  However, in a known method, if a large amount of water is mixed with fuel, combustion may become unstable or impossible, and depending on the compression ratio of the engine, etc., the mixing ratio of water to the fuel The effects were limited.

In addition, the conventional method has not been able to obtain a significant improvement in thermal efficiency. Therefore, this method is adopted until measures are taken for rust generation and return fuel processing by mixing water into the fuel in existing fuel injectors, special start-up measures, winter water freezing and corrosion measures. Less attractive, these measures can be used with stationary engines up to a water: fuel ratio of up to 1: 1, or in automobiles, a water: fuel ratio of around 20:80 can be used as an exhaust reduction device for in-use vehicles. The device is only partially manufactured and is not fully utilized.
JP-A-6-1983 JP 2001-329274 A JP 2002-201480 A JP 2002-248339 A

An object of the present invention is to provide a combustion method for a diesel engine in which nitrogen oxides and particulate matter in engine exhaust are reduced and thermal efficiency is improved in view of the above-described conventional points.

To solving means for achieving the above object, the combustion process of a diesel engine according to the present invention is characterized in the following <01> - <06>.
<01> the water and fuel the critical pressure or more pressurized water and the water was heated to over 250 ° C. or more, the water and fuel and water 50 to 90: water mixed in a ratio of fuel 50 to 10 A combustion method for a diesel engine, characterized in that the mixed fuel oil is injected into a diesel engine cylinder for self-ignition.
<02> a 250 ° C. or more heating water, the combustion process of a diesel engine according to the <01> performed by heating by heat exchange with the exhaust of the engine.
<03> The method for burning a diesel engine according to <01> or <02>, wherein the temperature of water is raised to a critical temperature of water or higher.
<04> the water and fuel the critical pressure or more pressurized water, water and fuel and water 50 to 90: is mixed at a ratio of fuel 50 to 10, was heated and the mixture of water and fuel on 250 ° C. or more A combustion method for a diesel engine, characterized in that water-mixed fuel oil is injected into a diesel engine cylinder for self-ignition.
<05> the water and the 250 ° C. or more heating of the mixture of fuel, combustion process of a diesel engine according to the <04> performed by heating by heat exchange with the exhaust of the engine.
<06> The combustion method for a diesel engine according to <04> or <05>, wherein the temperature of the mixture of water and fuel is raised to a critical temperature of water or higher.

  According to the present invention, it is possible to effectively reduce the oxides and particulate matter discharged from the diesel engine, improve the thermal efficiency of the engine, and improve the problems of the diesel engine with the conventional water-mixed fuel oil. Have.

  First, the background to the present invention will be described. In basic research using a diffusion flame conducted by the present inventor, if a sufficient amount of inert chemical species is mixed in the fuel, soot formation in the diffusion combustion field can be completely suppressed. It was possible to show that it could be controlled independently from both theoretical and experimental viewpoints. According to this theory, if the ratio of water: fuel is 50 to 90:50 to 50, preferably about 80:20, a sufficient soot generation suppressing effect can be obtained. This reveals the possibility of simultaneously reducing both nitrogen oxides and soot, which are highly dependent on the flame temperature and have been considered difficult to reduce simultaneously with soot.

  Furthermore, it has been found that by injecting water or a mixture of water and fuel above the critical temperature into the engine cylinder, the engine's thermal efficiency may be significantly surpassed. After that, when exhaust gas was measured using water / light oil mixed fuel, it was confirmed that drastic reduction of soot and nitrogen oxides was actually possible. Also, in premixed combustion, which is the most important combustion form after diffusion combustion in the combustion of diesel engines, the chemical reaction power calculation shows that the mixing of water and fuel is extremely effective for the simultaneous reduction of nitrogen oxides and soot. Indicated.

  However, if the pressure at which the fuel or water is preheated is below the critical pressure of water, vaporization will occur if it is preheated above the boiling point, and proper injection in the engine cylinder cannot be performed. We have obtained the prospect of effectively reducing nitrogen oxides and particulate matter discharged from diesel engines and improving the thermal efficiency of the engine, and completed the invention of the combustion method and combustion apparatus of the diesel engine It is.

It will be described below with reference to best modes for carrying out the present invention with reference to the drawings. The water and fuel according to the first embodiment are pressurized to a critical pressure of water or higher, the water is heated to 250 ° C. or higher or the critical temperature of water, and the water and fuel are water 50 to 90: fuel 50 to The implementation of the combustion method of the diesel engine in which the water-mixed fuel oil mixed in the ratio of water 80: fuel 20 is injected into the diesel engine cylinder for self-ignition is performed by the apparatus shown in FIG.

  That is, in FIG. 1, 1 is a water tank and 2 is a fuel tank. Reference numeral 3 denotes a water pressurization supply pump that sucks water from the water tank 1 and pressurizes it to a pressure higher than the critical pressure of water and discharges it. Reference numeral 4 denotes a fuel pressurizing supply pump that sucks up fuel from the fuel tank 2 and pressurizes the fuel to a pressure higher than the critical pressure of water and discharges the fuel. In the water pressurization supply pump 3 and the fuel pressurization supply pump 4, the volume ratio of water to fuel at the discharge pressure is such that the ratio of water is 50 to 90:50 to 50, preferably 80 to 20. Designed. Therefore, the two systems of the water pressurizing supply pump 3 and the fuel pressurizing supply pump 4 are operated synchronously by the electric motors 5 and 6 so that the water and fuel are always discharged at a discharge pressure higher than the critical pressure of water. The ratio of the liquid feeding amount is 50-90: 50 to 10 fuel, preferably 80: 20 fuel.

  Reference numeral 7 denotes a water accumulating chamber which is pressurized and discharged from the water pressurizing supply pump 3 at a critical pressure or higher, and 8 is a fuel which is pressurized and discharged from the fuel pressurizing supply pump 4 at a critical pressure or higher. It is a pressure accumulation chamber. The water accumulating chamber 7 and the fuel accumulating chamber 8 are effective for eliminating fluctuations in the liquid supply pressure from the water pressurizing supply pump 3 and the fuel pressurizing supply pump 4 to the injector 14. The pressure accumulation chamber 7 and the fuel pressure accumulation chamber 8 need not be equipped. However, for the convenience of the drawings, an embodiment in which a water pressure accumulation chamber 7 and a fuel pressure accumulation chamber 8 are provided will be described.

  The water accumulated in the water accumulating chamber 7 pressurized and discharged from the water pressurizing supply pump 3 at a pressure equal to or higher than the critical pressure is raised to 250 ° C. or higher or the critical temperature of water by the heating means. The heating means has a structure in which a high-pressure pipe 11 of water extending from the water accumulator 7 is penetrated into the exhaust pipe 10 of the diesel engine 9. The high-pressure pipe 11 is preferably spirally wound in the exhaust pipe 10 in order to increase the contact area with the exhaust heat.

  A high-pressure pipe 11 of water penetrating into the exhaust pipe 10 and a high-pressure pipe 12 of fuel extending from the fuel accumulator 8 are joined together 13 a and connected to the injector 14. Therefore, water-mixed fuel oil in which water and fuel are mixed at a ratio of water 50 to 90: fuel 50 to 10, preferably water 80: fuel 20, is injected into the diesel engine cylinder and self-ignited. If the water pressure accumulating chamber 7 and the fuel pressure accumulating chamber 8 are provided, the injector 14 injects the water-mixed fuel oil into the diesel engine cylinder at a stable water critical pressure.

  The rotational speeds of the electric motors 5 and 6 are such that a required amount of water and fuel determined by the load and rotational speed of the diesel engine 9 are fed, so that the rotational speed sensor 15, the crank angle sensor 16 and the accelerator pedal of the diesel engine 9 are opened. The detection signal of the degree sensor 17 is input to the control circuit 18 and controlled by the control circuit 18.

Next, the water and fuel according to the second embodiment are pressurized to above the critical pressure of water, and the water and fuel are mixed at a ratio of water 50 to 90: fuel 50 to 10, preferably water 80: fuel 20, Implementation of a diesel engine combustion method in which a water-mixed fuel oil in which a mixture of water and fuel is heated to 250 ° C. or higher or higher than the critical temperature of water is injected into the diesel engine cylinder and self-ignited is performed by the apparatus shown in FIG. It is.

  In the apparatus shown in FIG. 2, the structure of the apparatus shown in FIG. 1 is the same as that of the apparatus shown in FIG. 1 except that the temperature of the water / fuel mixture is raised to 250 ° C. The same. In other words, the high-pressure pipe 11, which joins water and fuel at a confluence 13 b downstream of the water accumulator 7 and the fuel accumulator 8, penetrates into the exhaust pipe 10 of the diesel engine 9. The high-pressure pipe 11 is also preferably wound spirally in the exhaust pipe 10 in order to increase the contact area with the exhaust heat.

  A high-pressure pipe 11 penetrating into the exhaust pipe 10 is connected to an injector 14. Accordingly, a water-mixed fuel oil in which water and fuel are mixed at a ratio of water 50 to 90: fuel 50 to 10, preferably water 80: fuel 20 and heated to 250 ° C. or higher or the critical temperature of water is diesel engine. It is injected into the cylinder and self-ignited.

  The heating means for raising the temperature of water or a mixture of water and fuel to 250 ° C. or higher or the critical temperature of water is not shown in addition to using the inside of the exhaust pipe 10 of the diesel engine 9, but an electric heater is used. It is also possible.

  Since the present invention is as described above, the elemental oxide and particulate matter discharged from the diesel engine are effectively reduced and the thermal efficiency of the engine is improved as in the explanation of the process leading to the present invention. The problem was solved. In order to prove this, the experimental results are shown in the figure.

  FIG. 3 is a diagram showing the influence of the water mixing ratio on the fuel on the emissions. As shown in FIG. 3, nitrogen oxides N and soot S exhausted from the engine were greatly reduced.

  FIG. 4 is a diagram showing an improvement in the trade-off relationship between nitrogen oxides (NOx) and particulate matter (PM). In FIG. 4, D2- indicates data of JIS No. 2 gas oil, and the number following D2- is the percentage of water in the water / light oil mixture.

  FIG. 5 is a map of soot and nitrogen oxide formation (chemical reaction kinetics calculation of a homogeneous mixture), where the vertical axis is the equivalence ratio and the horizontal axis is the temperature. As shown in FIG. 5, by dilution of the fuel, soot formation is greatly reduced even in the fuel rich region, and nitrogen oxide is reduced in the region near the theoretical mixing ratio where nitrogen oxide in diesel combustion becomes a problem. It is reduced to 1/5.

FIG. 6 is a diagram illustrating an analysis of a mechanism for suppressing soot formation.
The vertical axis is the molar fraction of gas species (Molar fraction of gas-phase specis), and the horizontal axis is time. As shown in FIG. 6, the production of C2-C4 unsaturated hydrocarbons and aromatic hydrocarbons, which are soot precursors, in the thermal decomposition process of the fuel is suppressed by the dilution of the fuel.

  FIG. 7 is a diagram showing the results of thermal efficiency investigation (numerical calculation). As shown in this method with the conventional diesel in FIG. 6, water / light oil mixed fuel is preheated by exchanging heat with exhaust waste heat. As a result, a part of the heat that has been thrown away from the exhaust pipe in the past is recovered as power that pushes up the piston in the engine combustion chamber with water vapor, thereby improving the thermal efficiency.

The block diagram which shows an example of the apparatus used for implementation of the method of this invention The block diagram which shows another example of the apparatus used for implementation of the method of this invention Diagram showing the effect of water mixing ratio on fuel on emissions Diagram showing improvement in trade-off relationship between nitrogen oxide (NOx) and particulate matter (PM) Soot and nitrogen oxide generation map Diagram showing analysis of suppression mechanism of soot formation The figure which shows the examination result (numerical calculation) of thermal efficiency

DESCRIPTION OF SYMBOLS 1 Water tank 2 Fuel tank 3 Supply pump for water pressurization 4 Supply pump for fuel pressurization 5 Electric motor 6 Electric motor 7 Water pressure accumulation chamber 8 Fuel pressure accumulation chamber 9 Diesel engine 10 Exhaust pipe 11 High pressure pipe 12 High pressure pipe 13a Merge 13b Merge 14 Injector 15 Rotational speed sensor 16 Crank angle sensor 17 Accelerator pedal opening sensor 18 Control circuit

Claims (6)

Water and fuel the critical pressure or more pressurized water, and water was heated on a 250 ° C. or more, the water and the fuel water 50-90: water mixture fuel oil were mixed at a ratio of fuel 50 to 10 Is injected into a diesel engine cylinder and self-ignited to burn the diesel engine. The 250 ° C. or more heating water, the combustion process of a diesel engine according to claim 1 carried out at heating by heat exchange with the exhaust of the engine. The diesel engine combustion method according to claim 1 or 2, wherein the temperature of water is raised to a critical temperature of water or higher. Water and fuel the critical pressure or more pressurized water, water and fuel and water 50 to 90: is mixed at a ratio of fuel 50 to 10, water mixed fuel heated the mixture onto 250 ° C. or more for the water and fuel A combustion method for a diesel engine, characterized in that oil is injected into a diesel engine cylinder for self-ignition. The Atsushi Nobori 250 ° C. or more mixture of water and fuel, the combustion method of the diesel engine according to claim 4 for the heating by heat exchange with the exhaust of the engine. 6. The diesel engine combustion method according to claim 4 or 5 , wherein the temperature of the mixture of water and fuel is raised to a critical temperature of water or higher .

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