JPH0684746B2 - Insulated diesel internal combustion engine - Google Patents

Description

The present invention relates to an adiabatic diesel internal combustion engine that improves intake efficiency by water injection.

[Conventional technology]

For the cylinder head, piston crown, part of the cylinder, etc., ceramics are used to insulate the combustion chamber, and hot exhaust gas is supplied to the turbocharger to increase the output of the turbocharger. The adiabatic internal combustion engine that enhances the thermal efficiency of
Various things have already been proposed. However, if the combustion chamber is made adiabatic, the temperature of the combustion chamber becomes very high, so that there is a problem that the intake efficiency is lowered and the combustion state is rather deteriorated.

Therefore, in a conventional adiabatic engine, for example, the adiabatic engine disclosed in Japanese Utility Model Laid-Open No. 58-163634, water is injected into the combustion chamber at the end of fuel injection in order to lower the temperature of the combustion chamber, and It lowers the combustion temperature and reduces NO _X components in the exhaust.

However, in the above-described adiabatic engine, the temperature of the cylinder wall cannot be lowered to the intake stroke, only to suppress the increase of the combustion temperature. That is, the cylinder wall is reheated by the combustion gas in the exhaust stroke following the combustion stroke. The air sucked into the cylinder in the intake stroke is instantly heated and expanded on the cylinder wall portion, so that the intake efficiency is reduced. Further, the premixed fuel mixture is not accumulated at the time of heat generation, and is easily ignited at the high temperature cylinder wall portion, the equal volume combustion period is reduced, and the performance is deteriorated.

[Problems to be Solved by the Invention]

In view of the above problems, an object of the present invention is to provide an adiabatic diesel internal combustion engine that effectively cools the inside of the cylinder at the end of the exhaust stroke, suppresses the temperature rise of air in the subsequent intake stroke, and enhances intake efficiency. .

[Means for Solving the Problems]

In order to achieve the above object, the adiabatic diesel internal combustion engine of the present invention forms a wall portion of a combustion chamber by a heat insulating material, starts water injection into the combustion chamber near the end of the exhaust stroke, and sets after exhaust top dead center. The water injection nozzle for terminating the water injection is provided in the cylinder head together with the combustion injection nozzle immediately before the overlapping portion of the exhaust valve and the intake valve.

[Action]

Water injection is started in the combustion chamber near the end of the exhaust stroke, and the water injection is ended immediately before the overlap between the exhaust valve and the intake valve set after the exhaust top dead center. Therefore, the heat of the wall of the combustion chamber is absorbed by the water, and the water becomes a high-temperature steam, which is supplied to the exhaust turbine together with the combustion gas, and the heat energy is recovered. The walls of the combustion chamber are cooled effectively.

Since the wall surface of the combustion chamber shifts to the intake stroke while being cooled by water, the rise in intake air temperature is suppressed and intake efficiency is improved.

The wall surface of the combustion chamber is only temporarily cooled, and the air in the combustion chamber is heated by the heat of the wall portion of the combustion chamber from the end of the intake stroke to the compression stroke, so the combustion state is improved.

After the end of the intake stroke, the heat of the wall of the combustion chamber is used to heat the air in the combustion chamber, so that the heat dissipation from the wall of the combustion chamber to the outside is minimized.

Example of Invention

An embodiment of the adiabatic diesel internal combustion engine of the present invention will be described with reference to the drawings.

As shown in FIG. 1, in the adiabatic diesel internal combustion engine, a ceramic cylinder liner 31 is fitted to a cylindrical portion 8a of a cylinder body 8 made of cast iron, and a large-diameter cylindrical portion formed at the upper end portion of the cylinder body 8. An inverted cup-shaped ceramic headliner 6 is fitted to 8b via gaskets 12 and 13. The upper wall 6a of the head liner 6 is overlaid with the cylinder head 4 made of cast iron via the gasket 5, and is joined to the flange of the cylinder body 8 by a head bolt (not shown). In this way, an adiabatic air layer 7 is provided between the peripheral wall of the headliner 6 and the cylinder body 8, and an adiabatic air layer 23 is provided between the upper wall 6a of the headliner 6 and the cylinder head 4.
Are formed respectively. The lower end of the head liner 6 is butted against the upper end of the cylinder liner 31.

In order to prevent the exhaust temperature from decreasing, the cylinder head 4 is coated with ceramics, or an intake / exhaust passage 19 formed by integrally casting a double liner 22 forming an adiabatic air layer.
Is formed. The intake passage and the exhaust passage are shown as the intake / exhaust passage 19 for the sake of simplicity.

The intake / exhaust passage 19 is connected to the intake / exhaust port of the upper wall 6a of the headliner 6. The intake / exhaust port is opened / closed by an intake / exhaust valve 25 slidably supported by a valve guide 26 of the cylinder head 4. The intake valve and the exhaust valve are similar to the intake / exhaust passage 19 for simplification of description.
Is shown as.

The piston 29 is composed of a piston body 9 made of metal and a piston crown portion 14 made of ceramics. piston ring
The piston main body 9 having the 11 mounted thereon has the piston crown portion 14 superposed on the protruding surface protruding conically from the upper surface, and the bolt 16
And nut 15 for connection. The connecting rod 33 is connected to the piston body 9 by the piston pin 10.

The fuel injection nozzle 24 has an intermediate portion supported by the cylinder head 4 and a tip portion supported by the upper wall 6 a of the head liner 6.
Similarly, the water injection nozzle 27 has an intermediate portion supported by the cylinder head 4 and a tip portion projected from the upper wall 6a into the combustion chamber. Fuel is injected from a known fuel injection pump 20 into a combustion chamber through an injection pipe 21 and a fuel injection nozzle 24. Water is jetted from the water feed pump 2 through the jet pipe 3 and the water jet nozzle 27 to the combustion chamber, particularly to the upper surface of the piston crown portion 14 and the lower surface of the upper wall 6a of the headliner 6.

Further, the valve timing characteristics of the intake / exhaust valve of the adiabatic diesel internal combustion engine, as is clear from the exhaust valve lift curve and the intake valve lift curve shown in FIG. It is set after the top dead center. In the exhaust stroke of the engine, the combustion gas (exhaust gas) in the cylinder is sufficiently discharged, and the intake valve is opened after the exhaust top dead center.

Further, the timing of water injection from the water injection nozzle 27 is, as shown in FIG. 6, near the end of the exhaust stroke, that is, the piston.
29 is started immediately before reaching the exhaust top dead center, and is ended immediately before the overlap portion of the exhaust valve and the intake valve set after the exhaust top dead center.

Next, the operation of the adiabatic diesel internal combustion engine according to the present invention will be described. The combustion of the fuel injected from the fuel injection nozzle 24 in the combustion process is performed in the combustion chamber surrounded by the ceramic headliner 6 and the ceramic piston crown 14, and the combustion heat is prevented from being released to the outside. The fuel injection timing is almost the same as that of a normal internal combustion engine.

As described above, water is injected from the injection nozzle 27 toward the wall surface of the combustion chamber near the end of the exhaust stroke of the engine, that is, immediately before the piston 29 reaches the top dead center, and at the end of the water injection, exhaust top dead It ends just before the overlap portion of the exhaust valve and the intake valve set after the point. After that, the intake valve begins to open.

The water whose walls have been heated becomes high-temperature, high-pressure steam, is guided to the exhaust turbine through the exhaust valve without flowing back to the intake valve, and is used for effective work. At the end of water injection, the injected water efficiently removes heat from the wall surface of the combustion chamber and cools the wall surface of the combustion chamber. However, the injected water cools only the wall surface portion of the heat insulating wall of the combustion chamber, and does not cool the entire wall portion (inside the wall). Therefore, since the wall surface of the combustion chamber is cooled by water injection at the end of the exhaust stroke, the intake air sucked into the cylinder in the subsequent intake stroke does not receive a large amount of heat from the wall portion of the cylinder, and thus NA An equivalent amount of air is introduced into the cylinder.

As shown in FIG. 7, specifically, when a small amount of water is injected onto the upper surface of the piston crown portion 14, the peripheral surface and the lower surface of the headliner 6, the temperature of the wall surface of the combustion chamber is instantly about 100 ° C. descend.

Water injection is performed at the end of the exhaust stroke, and is ended immediately before the overlap between the exhaust valve and the intake valve set after top dead center, so most of the exhaust gas remains hot and turbo-charged. Supplied to the feeder. Before the water is injected, the temperature distribution in the combustion chamber and the wall is as shown by the line a in FIG. 2, but when the water is injected, the wall surface of the combustion chamber (the surface of the headliner 6) The temperature inside the wall simply becomes lower as indicated by the line b in FIG. 3, and the temperature inside the wall becomes higher than the temperature at the wall surface. In this state, the intake stroke starts and air is sucked into the cylinder through the intake passage. At this time, headliner 6
Since the temperature of the wall surface of the cylinder is lowered, the temperature and expansion of the air sucked into the cylinder are suppressed, and a large amount of air having a high density is sucked. In the subsequent compression stroke, the temperature of the wall surface of the headliner 6 is recovered by the heat capacity of the headliner 6 as shown by the line c in FIG. 4, and the temperature of the air rises,
Helps compression work.

The water jet absorbs the heat of the wall surface of the cylinder as water vapor, and the temperature of the wall surface of the cylinder only temporarily drops.
The amount of heat released to the outside through the wall portion of the headliner 6 is smaller than that in the case where water is not jetted.

Therefore, in the cycle of the internal combustion engine shown by the solid line in FIG. 5, the temperature T of the air increases by the amount of heat absorbed from the wall surface of the combustion chamber in the compression stroke, the entropy increases, and the combustion speed of the fuel increases, The fuel efficiency of the engine is improved and the output is increased. That is, the engine cycle is equivalent to the reheat cycle added, the work amount increases, and the thermal efficiency improves. If the injection of water is stopped when the engine is started, the temperature of the combustion chamber rises rapidly, the startability is improved, and the warm-up operation time is shortened.

〔The invention's effect〕

As described above, the adiabatic diesel internal combustion engine of the present invention forms the wall of the combustion chamber by the heat insulating material, starts water injection into the combustion chamber near the end of the exhaust stroke, and sets the exhaust gas set after the exhaust top dead center. Since the water injection nozzle for terminating the water injection is provided in the cylinder head together with the fuel injection nozzle immediately before the overlapping portion of the valve and the intake valve, by the water injection near the end of the exhaust stroke, Since the temperature of the wall of the combustion chamber during the intake stroke has dropped, intake efficiency has improved,
In addition, since the heat energy that should be dissipated to the outside through the wall of the combustion chamber is absorbed as water vapor, the heat dissipation from the combustion chamber can be suppressed, and it can be effectively recovered by the exhaust turbine. To be

(A) Since water is injected toward the wall surface of the combustion chamber immediately before the exhaust valve and the intake valve overlap set after the exhaust top dead center, that is, before the intake valve opens, The walls are effectively absorbed by the water, which turns into hot steam that is supplied to the exhaust turbine along with the combustion gases to recover thermal energy.

(B) Since the wall surface of the combustion chamber is shifted to the intake stroke while being cooled by water, the rise in intake air temperature is suppressed and intake efficiency is improved.

(C) Since the wall of the combustion chamber is only temporarily cooled, the air in the combustion chamber is heated by the heat that flows backward in the wall of the combustion chamber from the end of the intake stroke to the compression stroke, so the combustion state is improved. To be done.

(D) After the end of the intake stroke, the heat of the wall of the combustion chamber is used to heat the air in the combustion chamber, so that the heat dissipation from the wall of the combustion chamber to the outside can be minimized.

(E) If the water injection amount is adjusted according to the operating conditions of the engine,
Combustion state is improved, output is increased, fuel efficiency is improved, and noise is reduced.

[Brief description of drawings]

FIG. 1 is a front sectional view of an adiabatic diesel internal combustion engine according to the present invention, and FIGS. 2 to 4 are explanatory views showing temperature distributions of a combustion chamber and a wall portion in an exhaust stroke of the engine, after water injection and in an intake stroke, respectively. FIG. 5 is a Ts diagram of the diesel cycle of the engine, FIG. 6 is a diagram showing water injection timing, and FIG. 7 is a diagram showing changes in wall temperature and intake efficiency due to water injection. 2 ... Water pump, 4 ... Cylinder head, 6 ... Headliner, 8 ... Cylinder body, 14 ... Piston crown, 19 ... Suction / exhaust passage, 24 ... Fuel injection nozzle, 25 ... Suction・ Exhaust valve, 27 …… Water injection nozzle, 31 …… Cylinder liner.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shinji Hara 8 Fujisawa, Fujisawa, Kanagawa Kanagawa Prefecture Fujisawa Plant (56) References JP-A-52-66125 (JP, A) JP-A-56-148641 (JP, A)

Claims (1)

[Claims] 1. A wall of a combustion chamber is formed by a heat insulating material, water injection is started into the combustion chamber near the end of the exhaust stroke, and immediately before an overlap portion of an exhaust valve and an intake valve set after exhaust top dead center. An adiabatic diesel internal combustion engine, characterized in that a water injection nozzle for terminating the water injection is provided in a cylinder head together with a fuel injection nozzle.