JPH0535248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a four-stroke adiabatic diesel engine that increases intake air charging efficiency.

[Prior Art] Adiabatic engines that use ceramic materials for the cylinder head, piston crown, part of the cylinder liner, etc. insulate the combustion chamber and supply high-temperature exhaust gas to the turbocharger. It is possible to increase the output of the supercharger and improve the thermal efficiency of the engine as a whole. However, since the ambient temperature of the combustion chamber becomes extremely high due to the insulation of the combustion chamber, there is a problem in that the intake air filling efficiency decreases and the combustion condition worsens.

For example, in the adiabatic engine disclosed in Japanese Utility Model Application Publication No. 58-163634, water is injected into the combustion chamber at the end of combustion injection to lower the maximum combustion temperature inside the cylinder, reduce NO _x components in the exhaust gas, and at the same time Efforts are being made to improve filling efficiency. However, water injection only increases the combustion temperature, and is not sufficient to continue to lower the temperature inside the cylinder until the intake stroke. In other words, in the exhaust stroke that follows the combustion stroke, the inside of the cylinder is reheated by the combustion gas, so
When the intake air is absorbed into the cylinder during the intake stroke, it is heated, reducing the intake air filling efficiency.

As mentioned above, in an adiabatic engine in which the combustion chamber is surrounded by heat insulating material, the heat inside the cylinder is not released to the outside during the compression stroke and combustion stroke, so the wall temperature of the combustion chamber increases, and the intake air flows inside the cylinder. As the engine heats up and expands, the intake air density decreases and the intake air filling efficiency decreases, and the fuel premixture is not accumulated when the engine starts, making it easier to ignite on high-temperature walls and reducing the isovolumic combustion period. , performance decreases.

[Problems to be Solved by the Invention] Therefore, in view of the above-mentioned problems, the purpose of the present invention is to cool the inside of the cylinder at the end of the exhaust stroke, so that the intake air temperature rises in the following intake stroke, and the intake air filling efficiency is improved. Our objective is to provide a 4-cycle insulated diesel engine that increases performance.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention is such that the head liner, cylinder liner, and piston crown that partition the combustion chamber are formed of ceramics, and water is poured into the combustion chamber at the end of the exhaust stroke. It is equipped with an injection nozzle and a water pump.

[Operation] When the piston crown approaches the cylinder head at the end of the exhaust stroke, that is, just before the intake stroke begins, water is injected into the combustion chamber, and the surface of the piston crown and the upper wall of the headliner that partitions the combustion chamber is injected into the combustion chamber. Since the temperature of the intake air decreases, a rise in the temperature of the intake air absorbed into the cylinder or a decrease in air density is suppressed. As a result, intake air filling efficiency is improved, fuel premixing is promoted, and combustion efficiency is improved.

[Embodiment of the Invention] As shown in FIG. 1, a cylinder liner 31, preferably made of ceramics, is fitted into the cylindrical portion 8a of a cylinder body 8 made of steel. Gasket on cylindrical part 8a
An inverted cup-shaped head liner 6 made of ceramics is fitted through 12 and 3. A cylinder head 4 made of steel is superimposed on the upper wall 6a of the head liner 6 via a gasket 5, and a cylinder body 8 is formed.
It is connected to the flange by the head bolt shown. In this way, a heat insulating air layer 7 is created between the peripheral wall of the head liner 6 and the cylinder body 8.
A heat insulating air layer 23 is formed between the upper wall 6a and the cylinder head 4, respectively. The lower end of the head liner 6 is butted against the cylinder liner 31.

In order to prevent a drop in exhaust temperature, the cylinder head 4 is coated with ceramics or has an exhaust passage 19 formed by integrally casting a double metal liner 22 with an insulating air layer. Exhaust passage 1
9 is an exhaust valve 2 provided on the upper wall 6a of the head liner 6.
It is connected to an exhaust port which is opened and closed by 5. The exhaust valve 25 is slidably supported by a valve guide 26 of the cylinder head 4. Although not shown, the intake passage and intake valve are also configured in the same manner.

The piston 29 is connected by a bolt 16 and a nut 15, with a ceramic piston crown 14 superimposed on a protruding surface projecting in an angular shape from the upper surface of a metal piston body 9 to which a piston ring 11 is mounted. The piston crown portion 14 is provided with a recess 17 constituting a main combustion chamber on its upper surface, while a cylindrical portion 32 is formed on its lower surface. The lower end surface of the cylindrical portion 32 is overlapped with the outer peripheral side upper surface of the piston body 9, and a heat insulating air layer 30 is formed between the piston body 9 and the piston crown portion 14. The piston body 9 is connected to a connecting rod 33 by a piston pin 10.

The fuel injection nozzle 24 is supported by the cylinder head 4, and the tip of the fuel injection nozzle 24 projects from the upper wall 6a of the head liner 6 into the combustion chamber. Similarly, the water injection nozzle 27 is supported on the cylinder head 4,
The tip of the water injection nozzle 27 projects from the upper wall 6a into the combustion chamber. Fuel is injected from a known fuel injection pump 20 into the combustion chamber through an injection pipe 21 and a fuel injection nozzle 24. Further, water is injected from the water pump 2 through the injection pipe 3 and the water injection nozzle 27 to the combustion chamber, particularly to the upper surface of the piston crown 14 and the lower surface of the upper wall 6a of the head liner 6.

Next, the operation of the four-cycle adiabatic diesel engine according to the present invention will be explained. Fuel injected from the fuel injection nozzle 24 during the combustion stroke is combusted in a combustion chamber surrounded by a ceramic head liner 6 and a ceramic piston crown 14, thereby preventing combustion heat from being released to the outside. The fuel injection timing is almost the same as a normal four-stroke engine.

According to the present invention, water is injected from the water injection nozzle 27 into the combustion chamber at the end of the exhaust stroke following the combustion stroke, that is, just before the piston 29 reaches top dead center. Therefore, water is injected onto the upper surface of the ceramic piston crown 14 and the lower surface and circumferential surface of the head liner 6, the injected water turns into steam, and the surface (inner wall surface) temperature drops by about 100°C. Thus, the injection of a small amount of water instantly lowers the surface temperature of the combustion chamber.

As shown by line b in FIG. 3, when looking at the head liner 6, only the surface temperature of the head liner 6 decreases, and the internal temperature of the wall portion becomes higher than the surface temperature. The intake stroke starts when the surface temperature of the head liner 6 is decreasing, and the temperature rise and expansion of the intake air drawn into the cylinder from the intake passage can be suppressed, so that a large amount of high-density intake air is drawn. Eventually, when the compression stroke begins, the heat inside the wall of the head liner 6 flows back to the surface, and the surface temperature recovers as shown by line c in FIG. 4.

As mentioned above, a larger amount of intake air is supplied to the cylinder than in the conventional example, and by the time fuel injection begins, the intake air temperature rises to almost the same temperature as in a conventional 4-cycle adiabatic engine, resulting in good combustion conditions. can get.
As a result, the water injection temporarily lowers the surface temperature of the head liner 6 and the piston crown 14, during which time the intake air is efficiently drawn in, and during the compression stroke the temperature of the intake air becomes lower than when water is not injected. It doesn't change much. During the exhaust stroke, the heat on the surfaces of the head liner 6 and piston crown 14 is absorbed by water vapor and is supplied to the turbocharger together with the exhaust gas.

To elaborate on this point, in the exhaust stroke, the surface temperature of the head liner 6 becomes very high as shown by line a in FIG. 2, so the intake air filling efficiency is low. When water is injected, the surface temperature of the head liner 6 is temporarily lowered, so that the intake air filling efficiency is improved. In the subsequent compression stroke, the surface temperature of the head liner 6 reaches the fourth level.
As shown by line c in the figure, the heat capacity of the head liner 6 recovers and the intake air temperature increases.

Therefore, water injection only temporarily lowers the surface temperature of the cylinder at the end of the exhaust stroke, and this heat is absorbed as water vapor. The amount of heat released to the outside through the wall of the head liner 6 is almost the same as when no water is injected. Furthermore, since water injection is performed at the end of the exhaust stroke, most of the exhaust gas is supplied to the turbocharger in a high temperature state.

In the diesel engine cycle shown by the solid line in Fig. 5, the intake air absorbs heat from the wall of the combustion chamber during the compression stroke, so the intake air temperature T becomes high, which is equivalent to adding a reheat cycle. , the amount of work increases and thermal efficiency improves.

[Effects of the Invention] As described above, the present invention injects water into the combustion chamber at the end of the exhaust stroke in a conventionally known four-cycle adiabatic diesel engine, so that the latent heat of vaporization of water causes combustion. The surface temperature of the chamber is suddenly and temporarily lowered, and the temperature rise of the intake air taken into the combustion chamber, that is, the decrease in the intake air density, is suppressed, and the intake air filling efficiency is improved.

In an adiabatic engine, it is not necessary to keep the cylinder wall temperature below a predetermined temperature, and in order to increase the intake air filling efficiency as in the present invention, water is injected into the combustion chamber at the end of the exhaust stroke, and the surface (wall surface) of the combustion chamber is Although the temperature decreases and the exhaust temperature also decreases somewhat, the amount of fluid (water vapor) supplied to the turbocharger increases. That is, the water injected into the combustion chamber absorbs the thermal energy of the wall surface, becomes water vapor, and is supplied to the turbocharger together with the exhaust gas, contributing to an increase in the output of the turbocharger.

Since the temperature of the combustion chamber is sufficiently low at the beginning of the intake stroke, the intake air charging efficiency increases, and at the end of the intake stroke, the intake air in the combustion chamber receives heat from the cylinder wall and becomes high temperature, and the fuel It has an effect on the combustion of. In other words, the temperature of the intake air increases as it receives heat from the walls of the combustion chamber during the compression stroke, increasing entropy, which increases the combustion speed of fuel due to the increase in temperature of the intake air, improving fuel efficiency and increasing engine output. can get.

The 4-cycle adiabatic diesel engine according to the present invention can control combustion conditions in all load ranges in the same way as conventional 4-cycle adiabatic diesel engines, and overall reduces combustion temperature, improves combustion efficiency, increases output, and reduces noise. It is possible to reduce the

[Brief explanation of the drawing]

Fig. 1 is a front sectional view of a four-cycle adiabatic diesel engine according to the present invention, Figs. 2 to 4 are explanatory diagrams showing the temperature distribution of the combustion chamber and headliner during the exhaust stroke, after water injection, and during the intake stroke, respectively. Fig. 5 is a T-s diagram of the same adiabatic diesel engine. 2: water pump, 4: cylinder head, 6: head liner, 8: cylinder body, 14: piston crown, 27: water injection nozzle, 31: cylinder liner.

Claims (1)

[Claims] The head liner, cylinder liner, and piston crown that partition the combustion chamber are made of ceramics,
A four-cycle adiabatic diesel engine characterized by being equipped with a water injection nozzle and a water pump that inject water into the combustion chamber at the end of the exhaust stroke.