Internal combustion engine

Abstract

An internal combustion engine with a cylinder head and at least one piston-cylinder unit, in which, in a cylinder, a piston can be moved between a bottom and a top dead center position, where, in the cylinder, between the piston and the cylinder head a main combustion chamber is formed, which communicates with a prechamber which has a prechamber gas valve, and where the intake and outlet valves of the main combustion chamber are actuated by an actuator, where the prechamber gas valve is connected to a source for a gas-air mixture and the prechamber charge consists of a gas-air mixture with a lambda higher than 1.2, preferably higher than 1.5 and particularly preferably higher than 1.7, and the actuator is configured such that the intake valve closes before the piston reaches the bottom dead center position, where the piston is designed as a flat piston.

Claims

1. An internal combustion engine comprising: a cylinder head and at least one piston-cylinder unit; a cylinder in the at least one piston-cylinder unit; a flat piston in the at least one piston-cylinder unit moveable between a bottom dead center position and a top dead center position; a main combustion chamber arranged in the cylinder between the piston and the cylinder head communicating with a prechamber having a prechamber gas valve; an actuator operable to actuate an intake valve and an outlet valve of the main combustion chamber such that the intake valve closes before the piston reaches the bottom dead center position; and an intake duct of the main combustion chamber is a source for a gas-air mixture for the prechamber gas valve connected via a connecting line, being a cavity in the cylinder head, provided between the intake duct and the prechamber gas valve; wherein a prechamber charge from the prechamber gas valve consists of the gas-air mixture with a lambda higher than 1.2.

2. The internal combustion engine according to claim 1, wherein a ratio of a volume of the prechamber to a compression volume of the main combustion chamber is in a range of 1% to 5%.

3. The internal combustion engine according to claim 1, further comprising a temperature control device provided for the connecting line, operable to keep the connecting line at a temperature preventing condensation of the gas-air mixture.

4. The internal combustion engine according to claim 1, wherein the internal combustion engine is a stationary gas engine coupled to a generator to generate a current.

5. The internal combustion engine according to claim 1, wherein the prechamber charge is the gas-air mixture with the lambda higher than 1.5.

6. The internal combustion engine according to claim 1, wherein the prechamber charge is the gas-air mixture with the lambda higher than 1.7.

7. The internal combustion engine according to claim 1, wherein a ratio of a volume of the prechamber to a compression volume of the main combustion chamber is in a range of 2% to 4%.

8. A method of operating an internal combustion engine comprising: providing an internal combustion engine with a prechamber and a main combustion chamber with a flat piston; charging via a connecting line being a cavity in a cylinder head, arranged between an intake duct of the main combustion chamber and a prechamber gas valve, the prechamber with a gas-air mixture from the prechamber gas valve with a lambda higher than 1.2; and operating an intake valve of the main combustion chamber connected to the prechamber, in an early Miller cycle.

9. The method according to claim 8, wherein charging the prechamber is with the gas-air mixture with the lambda higher than 1.5.

10. The method according to claim 8, wherein charging the prechamber is with the gas-air mixture with the lambda higher than 1.7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are explained in more detail with reference to the figures. The figures show the following:

(2) FIG. 1 A schematic representation of the parts of an internal combustion engine,

(3) FIG. 2 A graph representing a curve of pressure setting in the main combustion chamber and the charge-air pressure prevailing in the intake duct (upper diagram); Valve lift curves for different intake valve timings (middle diagram); Differential pressure between the pressure in the prechamber and the pressure in the intake duct, termed the prechamber differential pressure (lower diagram).

DETAILED DESCRIPTION

(4) In each diagram mentioned above, the crankshaft angle.

(5) FIG. 1 shows a cylinder 2 in which a piston 3 is arranged so as to be movable up and down, whereby a main combustion chamber 12 is formed between the piston 3 and the cylinder 2. At its top dead center, the piston 3 with the cylinder 2 forms the so-called compression volume.

(6) An intake duct 10 can be closed by an intake valve 6 and an outlet duct 11 can be closed by an outlet valve 7 opposite the main combustion chamber 12.

(7) A prechamber 4 communicates with the main combustion chamber 12 via overflow holes 17 and has an ignition source 13 and a prechamber gas valve 5 in the form of a non-return valve, which is connected to a source for a gas-air mixture. In this exemplary embodiment, the intake duct 11 itself serves as this source, and a connecting line 9, which is formed as a cavity in the cylinder head 15, is provided for the prechamber gas valve 5. To regulate the quantity of gas-air mixture that can be fed into the prechamber 4, an adjustable throttle is arranged in the connecting line 9 in this exemplary embodiment.

(8) Furthermore, a temperature control device 15 is provided in the form of pre-heating by means of engine cooling water in order to keep the connecting line 9 at a temperature that prevents condensation of the gas-air mixture.

(9) FIG. 2 shows the cylinder pressure curve for different intake valve timings in the upper part of the diagram.

(10) The valve lift curves of the intake and outlet valves are shown below for different intake valve timings.

(11) The diagram below shows the curve of the differential pressure across the prechamber gas valve over the crank angle.

(12) The series of curves are distinguished as follows:

(13) Curves 1 denote the pressure curves for the earliest intake valve closing (early Miller)

(14) Curves 2 denote the pressure curves for a later intake valve closing than curves 1

(15) Curves 3 denote the pressure curves for a later intake valve closing than curves 2. This is the filling-optimized valve lift curve, characterized by the lowest charge-air pressure to be applied at the same engine power.

(16) Curves 4 denote the pressure curves for a later intake valve closing than curves 3 (late Miller).

(17) The different intake valve lift curves 1 to 4 are shown in mm in the valve lift curves. The sequence is 1, 2, 3, 4.

(18) The charge-air pressure is adapted to the intake valve timings. The adapted charge-air pressures are represented as charge-air pressures 1 to 4, of which the highest charge-air pressure is applied to the valve timings 1. This is followed by the second highest charge-air pressure for the valve timings 4. The next highest charge-air pressure is applied to the valve timings 2. The lowest charge-air pressure is applied to the valve timings 3. The sequence of the charge-air pressures from high to low is therefore 1, 4, 2, 3.

(19) The resulting cylinder pressure curves are again marked with the numbers 1 to 4.

(20) In the diagram below, the curves of the differential pressure between the charge-air pressure (i.e. the pressure in the intake duct 10) and the pressure in the prechamber 4 over the crank angle for the different valve timings 1 to 4 are shown and marked with the numbers 1 to 4.

(21) A positive differential pressure (above the zero line) means that the pressure in the intake duct 10 (charge-air pressure) is higher than the pressure in the prechamber 4, and thus the gas-air mixture can flow from the intake duct via the prechamber gas valve into the prechamber. The differential pressure must, of course, still exceed the spring force of the prechamber gas valve 5 which is designed as a non-return valve, and must be higher than zero accordingly.

(22) The area under the differential pressure curve (between the differential pressure curve and the zero line) is proportional to the quantity of the gas-air mixture streamed into the prechamber 4 in one working cycle.

(23) It can be seen that, with early intake valve closing times (early Miller), significantly more gas-air mixture flows into the prechamber 4 than with the late intake valve closing times (late Miller) that are usual for internal combustion engines of this type.

(24) This ensures that, even with the use of a lean gas-air mixture from the intake duct 10 of the internal combustion engine 1, the same chemical energy can be introduced into the prechamber 4 as is otherwise possible only with the use of a rich gas-air mixture for flushing the prechamber (i.e. with a gas-flushed prechamber).

(25) In addition, residual gas is flushed from the prechamber effectively before the next combustion cycle.

(26) In the connecting duct 9, an adjustable throttle may be provided in one variant, via which the supplied quantity can be regulated and reduced if necessary.

(27) This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.