GB2545479A

GB2545479A - Pre-combustion chamber

Info

Publication number: GB2545479A
Application number: GB1522343.1A
Authority: GB
Inventors: Maier Thomas; Schaefer Friedrich; Schelle Jorg
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2015-12-18
Filing date: 2015-12-18
Publication date: 2017-06-21
Anticipated expiration: 2035-12-18
Also published as: GB201522343D0; GB2545479B

Abstract

Prechamber tip for an internal combustion engine featuring a dome-like shaped wall structure with a centre axis. A first 190 and a second group 290 of orifices extend through the wall and comprises inlets 192, 292 arranged at the inside of the wall and outlets 191, 291 arranged at the outside of the wall. The first group of ports 191 are rotated at an angle α with respect to a line normal to the centre axis 198 such that the inlets 192 and outlets 191 are not circumferentially aligned. The second group of ports 290 are rotated at an angle β with respect to a line normal to the centre axis 198 such that the inlets 292 and outlets 291 are not circumferentially aligned, the rotation being in an opposite direction to that of the first orifices. Each group of orifices may be arranged on a respective plane and may be inclined towards the prechamber tip.

Description

PRE-COMBUSTION CHAMBER

Technical Field [0001] The present disclosure generally relates to a pre-combustion chamber tip of a pre-combustion chamber assembly for an internal combustion engine. More specifically, the present disclosure relates to a pre-combustion chamber tip of a gaseous fuel internal combustion engine, wherein the pre-combustion chamber tip includes a first group of orifices and the second group of orifices.

Background [0002] It is known to use a pre-combustion chamber in internal combustion engine applications, such as gases fuel applications. Typically, the precombustion chamber is a relatively small gas accumulating chamber located at least partially in the engine cylinder head. The pre-combustion chamber is in fluid communication with a main combustion chamber of the engine via a number of orifices. During operation, fuel and/or air enters the pre-combustion chamber from the main combustion chamber through the orifices. This fuel air mixture may be enriched with fuel added to the fuel air mixture. Ignition means like a spark plug ignite the gaseous fuel within the pre-combustion chamber. Ignition of the gaseous fuel in the pre-combustion chamber creates a front of burning fuel which is jetted or otherwise advanced through the orifices and into the main combustion chamber thereby igniting some mixture of gases fuel and air therein.

[0003] To improve the ignitability of the gaseous fuel inside the pre-combustion chamber, a homogenous mixture of gaseous fuel with air, a high turbulent movement of the gaseous fuel air mixture and a homogenous distribution of residual gas created by the preceding combustion is desired.

[0004] US 2013/0055986 discloses a pre-chamber spark plug with one or more holes in connection with the main combustion chamber to achieve particular combustion performance characteristics. The aspect ratio and hole pattern may induce a rotational flow of fuel-air in-filling streams inside the pre-chamber volume. The rotational flow of the fuel air mixture may include both radial flow and axial flow characteristics based on the aspect ratio and hole pattern. Axial flow characteristics can include a first axial direction proximate the periphery of the rotational flow and a counter second axial direction approaching the center of the rotational flow. The radial and axial flow characteristics may further include radial air fuel ratio stratification and/or axial air fuel ratio stratification.

[0005] The hole pattern US 2013/0055986 discloses results in a high axial velocity of the fuel- air mixture, which affects adversely the ignitability of the fuel air mixture.

Summary of the Disclosure [0006] According to one aspect of the present disclosure an internal combustion engine has the pre-combustion chamber assembly with a pre-combustion chamber tip. The pre-combustion chamber tip has a dome-like shaped wall structure forming at least a portion of a pre-combustion chamber and having a center axis. Additionally the pre-combustion chamber tip has a first and a second group of orifices extending through the wall structure with inlets arranged at the inside of the wall structure and outlets arranged at the outside of the wall structure. Projections of the orifices of the first group onto a plane normal to the center axis define with lines arranged in the plane and normal to the center axis first angles. Projections of the orifices of the second group onto a plane normal to the center axis define with lines arranged in the plane and normal to the center axis second angles. The first angles exhibit an opposite orientation to the second angles.

Brief Description of the Drawings [0007] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings: [0008] FIG. 1 shows a cross sectional view of an internal combustion engine; [0009] FIG. 2 shows a cross sectional view of a pre combustion chamber; [0010] FIG. 3 shows a cross sectional view of the pre combustion chamber tip from the top; [0011] FIG. 4 shows a cross sectional view of the pre chamber tip from the side with the flows of the fuel air mixture.

Detailed Description [0012] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described herein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling ones of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different application. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the claims.

[0013] An exemplary embodiment of an internal combustion engine 10 is illustrated in Fig. 1. The internal combustion engine 10 may include features not shown, such as fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, etc. For the purposes of the present disclosure, the internal combustion engine 10 is considered a four stroke gaseous fuel internal combustion engine. One skilled in the art will recognize, however, that the gaseous fuel internal combustion engine 10 may be any type of engine (turbine, gas-, diesel-, natural gas-, propane- engine, etc.) that utilize a pre-combustion chamber. Furthermore, the internal combustion engine 10 may be of any size, with any number of cylinders, and in any configuration (“V”, in-line, radial, etc ). The internal combustion engine 10 may be used to power any machine or other device, including locomotive applications, on highway trucks or vehicles, off-highway trucks or machines, earthmoving equipment, generators, aerospace applications, marine applications, pumps, stationary equipment, or other engine powered applications.

[0014] The internal combustion engine 10 may include an engine block 12 having a plurality of cylinders 14 (one of which is illustrated in Fig. 1). A piston 16 may be slidably disposed within the cylinder 14 to reciprocate between the top dead center position and a bottom dead center position. A connecting rod 18 may connect the piston 16 to an eccentric crank pin 20 of a crankshaft 22 such that reciprocating motion of the piston may result in rotation of the crankshaft 22.

[0015] The internal combustion engine 10 may also include a cylinder head 24 engaged with the engine block 12 to cover the cylinder 14, thereby defining a main combustion chamber 26. The cylinder head 24 may define intake and exhaust openings 28 that may allow intake gases into the main combustion chamber 26 and exhaust gases out of the main combustion chamber 26, respectively. Engine valves 30 may be positioned to selectively open and close the intake and exhaust openings 28. Each cylinder 14 may include multiple intake and exhaust openings 28.

[0016] The internal combustion engine 10 may include a series of valve actuation assemblies 40 (one of which is illustrated in Fig. 1). Multiple valve actuation assemblies 40 may be provided per cylinder 14. For example, one valve actuation assembly may be used to open and close the intake valves and another valve activation assembly may be provided to open and close the exhaust valves [0017] The valve actuation assembly 40 may include a rocker arm 46. The rocker arm 46 may be pivotally mounted in the cylinder head 24 and may be attached to the engine valve 30 at one end and may be attached to a push rod 48 at the other end. Oscillation of rocker arm 46 about its pivot point 50 may cause the engine valves 30 to move between an open position and a closed position. The valve actuation assembly 40 may also include valve springs 52 that may bias the engine valves 30 towards a closed position (i.e. closing the intake and exhaust openings 28).

[0018] The other end of the push rod 48 may engage a lifter 54 which may engage a camshaft 56. The camshaft 56 may operatively engage the crankshaft 22. The camshaft 56 may be connected with the crankshaft 22 in any manner readily apparent to one skilled in the art where rotation of the crankshaft 22 may result in rotation of the camshaft 56. For example, camshaft 56 may be connected to a crankshaft 22 through a gear train (not shown).

[0019] As shown in Fig. 1, a first cam lobe 58 may be disposed on the camshaft 56 to engage the lifter 54. One skilled in the art may recognize that the camshaft 56 may include additional cam lobes to engage with other lifters in order to activate additional engine valves.

[0020] The internal combustion engine 10 may also include a pre-combustion chamber assembly 60, which may be positioned within the cylinder head 24 between the engine valves 30. The pre-combustion chamber assembly 60 may be configured in a variety of ways. Any assembly capable of being positioned in the cylinder head 24 to support a combustion event outside of the main combustion chamber 26 and to direct the combustion into the main combustion chamber 26 may be used.

[0021] The pre-combustion chamber assembly may be formed by a precombustion chamber upper part 70, which is attached to the cylinder head 24 and a pre-combustion chamber lower part 74 connected to the pre-combustion chamber upper part 70.

[0022] Referring to Fig. 2, a detailed partial cut view of the pre-combustion chamber lower part 74 is illustrated. The pre-combustion chamber lower part 74 may comprise a pre-combustion chamber tip 76 and the spark plug mounting section 78. The pre-combustion chamber tip 76 may be generally cylindrical and may be connectable to the spark plug mounting section 78 by any suitable means, such as a brazing or welding. For example the spark plug mounting section 78 may be made of a stainless steel material capable of withstanding the relatively high temperatures.

[0023] The pre-combustion chamber tip 76 may comprise a domelike shaped wall structure 118 having a base portion 104, a first portion 106 connect to the base portion 104, a second portion 108. First portion 106 may be connected to the second portion 108. The base portion 104 may be a substantially cylindrical portion, the first portion 106 may also be cylindrical and the second portion 108 may be a generally cylindrical spherical dome configured to close the domelike shaped wall structure 118 at second portion 108 facing towards the main combustion chamber 26. The second portion 108 and at least a part of the first portion 106 may extend into the main combustion chamber 26. The base portion 104, the first portion 106 and the second portion 108 may be disposed about a center axis 112 of the pre-combustion chamber tip 76.

[0024] The domelike shaped wall structure 118 may have a pre-combustion chamber 122 disposed therein. The pre-combustion chamber 122 may open at the first portion 106 of the pre-combustion chamber tip 76 to receive an electrode end of the spark plug 88. Those, the spark plug mounting section 78 may form at least a portion of the pre-combustion chamber 122.

[0025] The pre-combustion chamber tip 76 may include a plurality of spaced apart, secantially orientated orifices 190 and 290 disposed at the connecting portion 110. “Secantially” may mean in this description “like a secant”, i. e. subtend a circle but not the center of the circle. The plurality of orifices 190, 290 may extend through the domelike shaped wall structure 118 and may comprise inlets at the inside of the domelike shaped wall structure 118 and outlets 191, 291 at the outside of the domelike shaped wall structure 118. The outlets 191, 291 of both pluralities of orifices 190, 290 may be arranged different planes 194, 294 as shown in Fig 2. The planes 194, 294 may be normal to the center axis 112. One or both planes 194, 294 may also be inclined to the center axis 112. Alternatively the outlets 191,291 may be arranged in the same plane 194, 294.

[0026] The inlets of the pluralities of orifices 190, 290 may be arranged in the same or separate planes 194, 294. One or both planes 194, 294 may be normal or inclined to the center axis 112.

[0027] The orifices 190, 290 may be arranged in a plane normal to the main axis or in a plane inclined to the center axis 112.

[0028] The plurality of orifices 190, 290 may fluidly connect the pre-combustion chamber 122 with the main combustion chamber 26. The plurality of orifices 190 and 290 may be configured to direct expanding gases, like burning fuel for example, from the pre-combustion chamber 122 in a predetermined pattern into the main combustion chamber 26.

[0029] Two to twenty orifices 190, 290 may be arranged at the pre-combustion chamber tip 76. The orifices 190, 290 may have an identical diameter or the orifices 190 of the first group may have a different diameter than the orifices 290 of the second group. The orifices 190 of the first group may have different diameters among each other and/or the orifices 290 of the second group may have different diameters among each other. The orifices 190, 290 may have a straight shape, for example are cylindrical, or may be curved. If the orifices may be curved it will be understood that the direction of the fuel air mixture jetted out of the orifices into the pre combustion chamber is defined as the main axis of the orifice 190, 290, which define an angle α, β with the radial lines 198, 298.

[0030] The pre-combustion chamber tip 76 may be made from a high temperature material for example a high temperature temporally stable and environmentally resistant alloy.

[0031] As shown in Fig. 3 the plurality of orifices 190 are arranged in a plane normal to the center axis 112 separate to a plane normal to the center axis 112 wherein the plurality of orifices 290 is arranged. The orifices 190 have a main axis 196 which defines an angle a with a line 198 normal to the center axis 112. The angle a has an orientation a.

[0032] The orifices 290 have a main axis 296 which defines an angle β with a line 298 normal to the center axis 112. The angle β has an orientation b, which is opposite to the orientation a.

[0033] Referring to FIG. 4 a second embodiment of a pre-combustion chamber tip 76 is shown. Through the pre-combustion chamber tip 76 extend a first group of orifices 190 and a second group of orifices 290. The orifices 190, 290 are displaced to each other, The orifices 190, 290 are inclined in respect to a plane 194, 294 normal to the central axis 112 of the pre-combustion chamber tip 76. As shown in FIG. 4 the orifices 190, 290 may be inclined in the direction to the open end of the pre-combustion chamber tip. Alternatively the orifices 190,290 may be inclined in the direction toward the closed end of the pre-combustion chamber tip or the orifices 190 of the first group may be directed to the orifices 290 of the second group.

[0034] The inclination angle γ of the orificesl90 of the first group may be identical with the inclination angle γ’ of the orifices 290 of the second group or the orifices 190 of the first group define a smaller inclination angle γ with the plane 194 normal to the central axis 112 as the orifices 290 of the second group.

[0035] As shown in FIG. 4 a projection 390 of the orifices 190 of the first group onto a plane 391 normal to the central axis 122 defines an angle a with a radial line 396. The angle a has the orientation a.

[0036] A projection 394 of the orifices 290 of the second group on a plane 392 normal to the central axis 112 defines an angle β with a radial line 398. The angle β has the orientation b. The orientation a of the angle a is opposite to the orientation b of the angle β.

Industrial application

Fig. 4 shows the movement of the fuel air mixture in the pre-combustion chamber tip 76 during the compression stroke of the internal combustion engine 10.

During the compression stroke the fuel air mixture from the combustion chamber is pushed through the orifices 190, 290 into the pre-combustion chamber tip 76 The orifices 190 may be arranged secantially, i. e. are inclined to the radius of the pre-combustion chamber tip 76, which is arranged in the same plane as the orifices 190. Due to the orientation of the orifices 190 a first swirl 300 is created with a rotational component normal to the center axis 112.

The orifices 290 are also arranged secantially in the pre-combustion chamber lower part 74 in a zone below the orifices 190 and have an opposite orientation. As the fuel air mixture is driven through the orifices 290,a second swirl 301 is created, which may be displaced to the first swirl 300. As the second swirl 301 has a rotational component in an opposite direction, the rotational component of both swirls may get canceled or diminished resulting in a small directed velocity of the fuel air mixture and a high turbulent energy of the fuel air mixture

Claims

1. A pre-combustion chamber tip (76) of a pre-combustion chamber assembly (60) of an internal combustion engine (10), the pre-combustion chamber tip (76) comprising: a domelike shaped wall structure (118) forming at least a portion of a precombustion chamber tip (76) and having a center axis (112); and a first and a second group of orifices (190, 290) extending through the domelike shaped wall structure (118) and comprising: inlets (192, 292) arranged at the inside of the domelike shaped wall structure (118); outlets (191, 291) arranged at the outside of the domelike shaped wall structure (118); projections (390) of the orifices (190) of the first group onto a plane normal (391) to the center axis (112) that defines first angles (a) with a line (396) normal to the center axis (112); and projections (394) of the orifices (290) of the second group onto a plane (392) normal to the center axis (112) define a second angle (β) with lines (398) normal to the center axis (112) wherein the first angles (a) and the second angles (β) have different orientations (a, b).

2. The pre-combustion chamber tip (76) according to claim 1, wherein the orifices (190) of the first group are arranged in a first plane (194) and the orifices (290) of the second group are arranged in a second plane (294) different to the first plane (194).

3. The pre-combustion chamber tip (76) according to the claim 2, wherein the first plane (194) is parallel to the second plane (294).

4. The pre-combustion chamber tip (76) according to any one of the claims 2 and 3, wherein the first plane (194) and/or the second plane (294) is normal to the center axis (112).

5. The pre-combustion chamber tip (76) according to any one of the claims 2 to 4, whereby the pre-combustion chamber tip (76) has a maximal radius (302) normal to the central axis and the distance between the first plane (194) and the second plane (294) is smaller than the maximal radius (302).

6. The pre-combustion chamber tip (76) of claim 1, wherein the orifices (190) of the first group are inclined in respect to the first plane (194).

7. The pre-combustion chamber tip (76) of claim 1 or 6, wherein the orifices (290) of the second group are inclined in respect to the first plane (194).

8. The pre-combustion chamber tip (76) according to any one of the preceding claims, wherein the first angles (a) and the second angles (β) have the same absolute value.

9. A pre-combustion chamber lower part (74) for attaching to a pre-combustion upper part (70) of an internal combustion engine (10), the pre-combustion chamber lower (74) part comprising: a spark plug mounting section (78) for mounting at least one spark plug (88); and a pre-combustion chamber tip (76) according to any one of the preceding claims attached to the spark plug mounting section (78).

10. An internal combustion engine (10) comprising a main combustion chamber (9); a cylinder head (24) configured to form at least a portion of the main combustion chamber (9); and a pre-combustion chamber assembly (60) for attaching to the cylinder head (24) and comprising a pre-combustion chamber upper part (70) and a pre-combustion chamber lower part (74) according to claim 9, wherein the pre-combustion lower part (74) and the pre-combustion upper part (70) define a pre-combustion chamber (122) and the pre-combustion chamber tip (76) at least partially extends into the main combustion chamber (9) and the pre combustion chamber (122) is in fluid communication with the main combustion chamber (26) via the orifices.