WO2015078963A1

WO2015078963A1 - Injection system for compression-ignited diesel engines

Info

Publication number: WO2015078963A1
Application number: PCT/EP2014/075800
Authority: WO
Inventors: Christoph Mathey; Paolo Tremuli
Original assignee: Abb Turbo Systems Ag
Priority date: 2013-11-29
Filing date: 2014-11-27
Publication date: 2015-06-04

Abstract

The invention relates to are deductible in the computation of the profits of the payer of this income. According to the invention an injection nozzle (101) is arranged in addition to a conventional injection nozzles to reduce NOx. At a first injection time, a first fuel amount (121) is applied to a vaporization surface of a flame ring (119) by means of the additional injection nozzle such that a lean combustion mixture is produced. Furthermore, at a second injection time, a fuel amount is introduced in the combustion chamber such that a rich combustion mixture is produced.

Description

DESCRIPTION

Injection system for compression ignition diesel engines

T E C H N I S C H E S G E B I ET

The invention relates to the field of compression ignition diesel engines.

It relates to an injection system for compression-ignition diesel engines for the controlled injection of fuel by means of injection nozzles in a combustion chamber of a cylinder with controllable intake and exhaust valves, and a compression-ignition diesel engine with such an injection system.

Due to the high temperature of combustion in engines, NOx compounds form. The higher the combustion temperature, the higher the NOx emissions. In order to limit the formation of NOx, a homogeneous combustion is sought.

In the case of diesel combustion arise due to the heterogeneous mixture formation zones in which the combustion proceeds stoichiometrically (without excess air). For this reason, in a constant pressure combustion with excess air principally higher NOx emissions than in a continuous process with a homogeneous mixture formation.

In order to limit the formation of NOx in the case of diesel combustion, it is necessary to strive for as homogeneous a combustion as possible. At the same time, fuel in liquid form must continue to be supplied directly to the combustion chamber during combustion, in order to be able to further maintain the advantages of the diesel process. This is a conflicting goal in the current state of the art, as diesel fuel injection occurs very early in conventional injection systems for "diesel knock" combustion, which can lead to mechanical damage.

It is known in internal combustion engines wall locations, where particularly high heat consumption is expected to provide with separate, possibly interchangeable inserts to distribute the local heat stress on a larger area and to have the possibility of cheaper replacement for any heat cracks. Such inserts in the cylinder wall in the region of the cylinder head are known as flame rings. From DE 636 782 C1 a flame ring composed of juxtaposed rings is known, which is provided on the inside with radial, outwardly tapering, wedge-shaped cuts, whereby less heat to be dissipated in the water-cooled cylinder surfaces.

Furthermore, from DE 262 939 C1 also a flame ring is known, which is slotted to avoid undesirable pressure due to thermal expansion, with possibly more slots are provided, which may be formed both continuously and not entirely continuous.

KU RZ E D A R ST E L U N G D E R E R F I N D U N G

The object of the invention is to provide a generic injection system which allows a combination for creating a lean mixture with an evaporation of the injected diesel fuel to form a relatively homogeneous air-diesel mixture and ensures an ignition injection of diesel fuel to prevent the formation of NOx. Limit emission.

The solution of this object is achieved according to the invention in that an additional, independently controllable injection nozzle with an injection angle for a fuel supply to the hot surface of a arranged in the upper wall or boundary region of the combustion chamber, optionally with respect to the remaining, brennraumbegrenzenden cylinder wall thermally insulated, optionally from a Material with high heat capacity manufactured flame ring is arranged with a present component temperature above the boiling temperature of the fuel and via the additional injector by injecting onto the hot surface first, a formation of a homogeneous mixture below a Selbstentzündungsgrenze and after state change of temperature and pressure within the cylinder over the further injection nozzle a quantity of fuel as ignition injection can be introduced.

As a result of the contact of the diesel fuel with a hot evaporation surface, the fuel evaporates and thus forms a mixture with the air in the combustion chamber. This in turn causes the formation of a homogeneous mixture, which does not self-ignite due to the existing extreme excess air and the temperature level in the combustion chamber. Thus, the NOx levels can be reduced when burning. Furthermore, through which in the Combustion chamber located non-flammable homogeneous mixture, the temperature level can be reduced in the combustion chamber, with a subsequent necessary for ignition injection of diesel fuel is then carried out in a conventional manner.

In order to ensure optimized evaporation of the fuel, the evaporation surface of the flame ring at the first injection time, a temperature of between 200 ° C and 500 ° C, in particular between 200 ° C and 350 ° C, have.

In an embodiment of the invention is further provided that the additional injection nozzle has a variable spray angle and / or a variable Lochdurchmessser.

It is therefore proposed that the fuel supply via the one or more additional injector (s) after the closing of the intake valve and before the start of the main injection takes place.

In addition, it is proposed that the fuel supply via the additional injector between 10 ° KW NUTP and

40 ° KW NUTP, in particular between 1 7 ° KW NUTP and 23 ° KW NUTP in conventional diesel engines, and between 80 ° KW VUTP and 40 ° KW NUTP in diesel engines with a Miller cycle or Atkinson cycle takes place and an ignition injection via the additional injection nozzle between 20 ° KW vOTP and 0 ° KW vOTP. For this purpose, provision is made in particular for the fuel supply to take place via the additional injection nozzle between 17 ° CA NUTP and 23 ° CA NUTP.

For "after bottom dead center" the abbreviation nUTP is used and accordingly the "v" for vUTP stands for "before". The abbreviation OTP stands for "top dead center" and the "n" for "after" and the "v" for "before". The unit "° KW" stands for degree crank angle. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, an embodiment of the invention is shown schematically. Show it:

1 is a sectional view of a cylinder with injection nozzles, wherein an additional injection nozzle is directed to an exhaust valve;

Figure 2 is a view like Figure 1 with an additional injector, which is alternatively directed to a flame ring.

3 shows a representation like FIG. 1 with an additional injection nozzle, which is alternatively directed to a piston surface

An illustration with an activated conventional injector after injection through an additional injector and

5 is a diagram of a theoretical diesel engine process at

Gleichvolumen-, Gleichdruckverbrennung with illustrated additional fuel injection.

WAY FOR CARRYING OUT THE INVENTION

The arrangement shown consists of the cylinder 115 of a single- or multi-cylinder internal combustion engine with a movable piston 113. In the interior of the cylinder 115 is formed between the overhead cylinder head 114 and the movable piston 113 of the combustion chamber 117 from. In the transition region between the cylinder and the cylinder head, a flame ring 119 is arranged. The cylinder optionally has a cooling device 116 operated by means of cooling water.

In the cylinder head 114 inlet opening 110 and outlet opening 109 are arranged, which are each closed by a controlled inlet valve 105 and an outlet valve 103. A conventional injection nozzle 107 is arranged in the cylinder head, by means of which a quantity of fuel into the free volume of the combustion chamber 117 as ignition injection 123 can be introduced.

In addition to the conventional injection nozzle 107, the arrangement shown according to the invention has an additional, optionally offset by about 90 degrees, injection nozzle 101, with which fuel can be injected at a different angle in the combustion chamber, as with the first injection nozzle. Optionally, the two nozzles in a common nozzle holder may be arranged, wherein the respective nozzle openings of the two nozzles allow different injection angles and can be controlled independently voneinender.

The flame ring is embedded in the wall of the cylinder 1 1 5. Optionally, a thermal insulation layer 120 is provided between the flame ring 19 and the wall of the cylinder 15. The flame ring is optionally made of a Mateiral with a high heat capacity, in particular a higher heat capacity than the heat capacity of the material surrounding the flame ring wall parts.

Due to the thermal insulation layer and / or the high heat capacity of the flame ring 1 19 retains a higher temperature than the surrounding water-cooled wall of the cylinder 1 15. The permanently higher temperature of the flame ring 1 19 is used according to the invention for the evaporation of the fuel.

According to the embodiment of FIG. 2, the additional injection nozzle 101 is oriented such that the spray jet 121 is directed to the hot surface of the flame ring 1 19. In the further alternative embodiment according to FIG. 3, the directed injection nozzle 1 01 is aligned such that the spray jet 122 is directed both to the surface of the flame ring 19 and to the surface of the outlet valve 103 facing the combustion chamber.

First, fuel is sprayed onto the flame ring 1 19, or the outlet valve 103 or the piston surface, via the additional injection nozzle 101. Due to a normally occurring temperature of 230 ° C on the wall of the flame ring 1 1 9 or on the exhaust valve 1 03 or on the piston surface of the sprayed diesel fuel evaporates completely, so that a lean combustion mixture with an air flow rate of about 3.2 times the minimal necessary amount of air arises, which does not ignite itself.

The piston position is about 20 ° KW NUTP. Via the injection nozzle 101, the fuel can be sprayed on the outlet valve 1 03, flame ring 1 19 and piston surface. It is of course also possible to spray on two or more parts.

At the following time, the fuel 1 23 is injected into the combustion chamber 1 1 7 via the injection nozzle 107 introduced in the cylinder head. In this case, the piston 1 1 3 a position between 20 ° KW vOTP and 0 ° KW vOTP on. As a result of the now injected fuel 1 23, the lean combustion mixture previously produced with the supplied fuel 123 mixes to form a rich combustion mixture with an air flow rate of approximately 1.3. With sufficient compression by reducing the combustion chamber volume then ignites the fuel-air mixture in the combustion chamber 1 17 and moves the piston 1 thirteenth

In addition, it is noted that a "lean burn" is generally present when the amount of air is greater than that which is minimally necessary to burn the fuel. In particular, there is a lean combustion mixture when the amount of air is about 1 .5 to 5 times the minimum necessary amount of air.

A "rich combustion mixture" is when the amount of air is less than that which is minimally necessary to burn the fuel. In particular, a rich combustion mixture is present when the amount of air is less than 1 .5 times the minimum necessary amount of air.

The necessary amount of air for diesel fuel combustion is approx. 14.2 kg air / kg fuel.

In the illustrated diagram of a theoretical diesel engine process in the case of equal-volume, constant-pressure combustion according to FIG. 5, it is additionally shown how an additional fuel injection 18 is assigned.

The injection system is controlled by an electronic control unit 108, which may be integrated in the engine control unit or may be configured as a separate control unit, which is optionally connected to the engine control unit. The control unit is connected to the injection nozzles 101 and 107 for controlling the injection via control lines. In addition, the control unit optionally sensors for detecting engine and / or environmental data. These data are then processed by a microprocessor in the electronic control unit to control the injection and optionally stored in a data memory integrated or associated with the control unit. NAME LIST

101 Second injection nozzle

103 exhaust valve

105 inlet valve

107 Injection nozzle located centrally above the combustion chamber

108 control unit with control lines and optional sensors

109 outlet opening

110 inlet opening

113 pistons

114 cylinder head

115 cylinders

116 (water) cooling of the cylinder

117 combustion chamber

118 Additional fuel injection

119 flame ring

120 Thermal insulation

121 Fuel supply on flame ring

122 fuel supply to exhaust valve

123 fuel supply (ignition injection)

124 fuel supply on piston surface

Claims

P AT EN TA NSPR O CHE

1 . Injection system for compression-ignition diesel engines for the controlled injection of fuel by means of injection nozzles into a combustion chamber of a cylinder with controllable intake and exhaust valves (105, 103), wherein a first injection nozzle (107) above the between an overhead cylinder head and a movable piston (1 13) extending combustion chamber is arranged, and wherein the combustion chamber in an upper wall region an embedded in the wall region of the combustion chamber flame ring (1 19), wherein the flame ring (1 19) has a component temperature above the boiling temperature of the fuel,

characterized in that

at least a second, independently controllable injection nozzle (1 01) for a fuel supply (121, 1 22) on the surface of the flame ring (1 19) is aligned and via the second injection nozzle (101) by the spraying of the fuel on the hot surface of the flame ring (1 19) first a formation of a homogeneous mixture below a Selbstentzündungsgrenze takes place and after state change of temperature and pressure within the cylinder via the first injection nozzle (107), a fuel amount as ignition injection (123) can be introduced.

2. Injection system according to claim 1, characterized in that at least one second injection nozzle (101) is directed with an injection angle for the supplied fuel in a region of the flame ring (1 19) and in the region of the exhaust valve (1 03).

3. Injection system according to claim 1, characterized in that the at least one second injection nozzle (101) is directed with an injection angle for the supplied fuel in a region of a flame ring (1 19), in the region of the exhaust valve (1 03) and the piston surface ,

4. Injection system according to one of claims 1 to 3, characterized in that the at least one second injection nozzle (101) has a variable spray angle and / or a variable hole diameter.

5. Injection system according to one of claims 1 to 4, characterized in that the fuel supply (121, 122) via the at least one second injection nozzle (1 01) after the closure of the inlet valve (105) and before the start of the ignition injection (123) ,

6. Injection system according to one of claims 1 to 5, characterized in that the fuel supply (121, 122) via the at least one second injection nozzle (1 01) between 10 ° KW NUTP and 40 ° KW NUTP in conventional diesel engines and between 80 ° KW vUTP and 40 ° CA nUTP for diesel engines with a Miller or Atkinson cycle and ignition injection (123) via the first injector (107) between 20 ° CA vOTP and 0 ° CA vOTP.

7. Injection system according to one of claims 1 to 6, characterized in that the fuel supply (121, 122) via the at least one second injection nozzle (01 01) takes place between 17 ° KW NUTP and 23 ° KW NUTP.

8. Injection system according to one of claims 1 to 7, comprising an electronic control unit (108) with a microprocessor and control lines for driving the injection nozzles (101, 107).

9. Injection system according to claim 8, wherein the electronic control unit (108) is connected to at least one sensor for detecting engine and / or ambient data, and comprises a data memory for storing the data detected by the sensor.

10. A compression-ignition diesel engine, comprising a plurality of cylinders with controllable intake and exhaust valves, characterized by an injection system according to one of claims 1 to 9, wherein each per cylinder, a first injection nozzle (1 07) and at least one second, independently controllable injection nozzle (101) present is.