WO2018050789A1

WO2018050789A1 - Cylinder head

Info

Publication number: WO2018050789A1
Application number: PCT/EP2017/073214
Authority: WO
Inventors: Adam D. TURNOCK; E. James SMITH; Andrew G. STONE; Markus Schwarzl; Christof KNOLLMAYER; Andreas ZUK
Original assignee: Perkins Engines Company Limited
Priority date: 2016-09-15
Filing date: 2017-09-14
Publication date: 2018-03-22
Also published as: GB2553821B; GB201615742D0; GB2553821A

Abstract

The disclosure provides a cylinder head (10) for an internal combustion engine. The cylinder head (10) comprises an inlet port (12) comprising a main inlet passage (40) bifurcating into a first inlet passage (41 ) and a second inlet passage (42), the first inlet passage (41 ) terminating at a first inlet valve hole (43) and the second inlet passage (42) terminating at a second inlet valve hole (44). The first inlet passage (41) comprises a helical ramp portion (50) upstream of the first inlet valve hole (43), for inducing a helical flow of inlet gases into a cylinder associated with the cylinder head (10) and thereby imparting swirl thereto, The helical ramp portion (50) comprises a surface (51) that extends towards the first inlet valve hole (43), the surface (51 ) having an angle selected from a range of from 55° to 63° relative to a longitudinal axis through a centre-point of the first inlet valve hole (43). The second inlet passage (42) is substantially linear, for inducing a tangential flow of inlet gases into the cylinder and thereby imparting swirl thereto. The cylinder head (10) further comprises an exhaust port (14) comprising a main exhaust passage (71 ) bifurcating into a first exhaust passage (71 ) and a second exhaust passage (72), the first exhaust passage terminating at a first exhaust valve hole (73) and the second exhaust passage terminating at a second exhaust valve hole (74). The cylinder head (10) further comprises a threaded spark plug sleeve port (31 ) and first and second coolant jackets (80,90).

Description

CYLINDER HEAD

Technical Field This disclosure is directed to a cylinder head, and in particular to a cylinder head for internal combustion engines.

Background Internal combustion engines, such as natural gas engines, generally comprise a cylinder block housing one or more cylinders having a reciprocating piston therein. The volume contained by the cylinder and reciprocating piston forms a combustion chamber. A cylinder head is typically coupled to an open end of the cylinder, and contains at least one inlet port having an inlet valve for delivering a fuel/air mixture from an intake manifold of the engine into the cylinder. At least one exhaust port having an exhaust valve is provided for allowing combusted exhaust gases to discharge from the cylinder and pass to an exhaust manifold of the engine. A common arrangement is a dual intake inlet port having two inlet valves, and a dual exhaust port having two exhaust valves. The inlet and exhaust valves may be operated by rocker arms, which may be located together with one or more spark plugs in the cylinder head, or in a housing directly above the cylinder head. In the case of an overhead valve (OHV) design, the operation of the exhaust valves is initiated by a camshaft sited in the cylinder block, which effects movement of the rocker arms via pushrods. In the case of an overhead camshaft (OHC) design, the camshaft is sited in the cylinder head.

The cylinder head may also include integral ducts and passages through which a coolant may pass, to facilitate the transfer of heat away from the cylinder head. Optimisation of the design of the ports and ducts within the cylinder head may lead to greater efficiency of the engine. For example, the inlet port may be designed to impart swirl to inlet gases entering the cylinder, to create turbulence (known as 'charge motion') in the cylinder prior to, during, and after a spark event. Increased turbulence may result in faster ignition when a spark occurs, and thus a more rapid flame propagation, faster burn, and better combustion efficiency. However, increased turbulence may cause more heat to be lost to the combustion chamber walls, leading to lower thermal efficiency. By optimising the design of the inlet ports, these two effects may be balanced to improve the overall engine efficiency. Swirl generated by inlet ports is generally quantified via a steady flow test on a flow bench, typically using the paddlewheel method or the flow straightener method. In the flow straightener method, a smooth flow of air is inducted through the inlet ports of a cylinder head into a test cylinder, within which is a flow straightener comprising a honeycomb matrix normal to the longitudinal axis of the cylinder. As fluid passes through the flow straightener, swirl is arrested and all velocity components perpendicular to the longitudinal axis of the cylinder are revoked. The flow straightener is held in position by bearings, at which the related energy from the revoked velocity components can be detected directly and with high accuracy as reaction force. The reaction torque exerted by the swirling flow in the cylinder on the flow straightener as it passes therethrough is equal to the total angular momentum flux through the plane coinciding with the flow straightener's upstream face irrespective of axial or tangential velocity distributions. A swirl number (or swirl coefficient) may be defined, essentially comparing the flow's angular momentum with its axial momentum. The swirl coefficient can be expressed as

Ns = 8T/ (mvo B)

Where T is the swirl torque, 'm' is the air mass flow rate, 'vo' is a characteristic velocity derived from the pressure drop across the valve, and 'B' is the cylinder bore diameter. Summary

The present disclosure provides a cylinder head for an internal combustion engine, comprising:

an inlet port comprising:

a main inlet passage bifurcating into a first inlet passage and a second inlet passage, the first inlet passage terminating at a first inlet valve hole and the second inlet passage terminating at a second inlet valve hole; wherein

the first inlet passage comprises a helical ramp portion upstream of the first inlet valve hole for inducing a helical flow of inlet gases into a cylinder associated with the cylinder head and thereby imparting swirl thereto, the helical ramp portion comprising a surface that extends towards the first inlet valve hole, the surface having an angle selected from a range of from 55° to 63° relative to a longitudinal axis through a centre-point of the first inlet valve hole; and wherein

the second inlet passage is substantially linear for inducing a tangential flow of inlet gases into the cylinder and thereby imparting swirl thereto;

an exhaust port comprising a main exhaust passage bifurcating into a first exhaust passage and a second exhaust passage, the first exhaust passage terminating at a first exhaust valve hole and the second exhaust passage terminating at a second exhaust valve hole;

a threaded spark plug sleeve port; and

first and second coolant jackets.

By way of example only, an exemplary embodiment of a cylinder head is now described with reference to, and as shown in, the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a perspective view of a cylinder head according to the present disclosure in situ with further components of the engine;

Figure 2 is a perspective view of the cylinder head of Figure 1 , without the further components; Figure 3 is a further perspective view of the cylinder head of Figures 1 and 2;

Figure 4 is a cross-sectional plan view of the cylinder head of Figures 1 to 3, showing an inlet port and an exhaust port; Figures 5 to 7 are 3D perspectives of different aspects of the inlet port of Figure 4;

Figures 8 to 10 are 3D perspectives of different aspects of the exhaust port of Figure 4; Figure 1 1 is a cross-sectional plan view of the cylinder head of Figures 1 to 4, showing a first coolant jacket;

Figure 12 is a perspective view of the first coolant jacket of Figure 1 1 ;

Figure 13 is a further perspective view of the first coolant jacket of Figures 10 and

1 1 ;

Figure 14 is a cross-sectional plan view of the cylinder head of Figures 1 to 4, showing a second coolant jacket;

Figure 15 is a perspective view of the second coolant jacket of Figure 14; and

Figure 16 is a further perspective view of the second coolant jacket of Figures 14 and 15.

Detailed Description

Figures 1 to 3 illustrate a cylinder head 10 for a single cylinder of an internal combustion engine (not fully illustrated), such as a natural gas engine, having a plurality of cylinders (not shown) housed in a cylinder block. Each cylinder may be closed at one end by a reciprocating piston and at an opposing end by a first face 1 1 of the cylinder head 10, to form a combustion chamber (not shown). A respective cylinder head 10 may be provided for each cylinder.

The cylinder head 10 has a first end 13 and an opposing second end 15, connected by opposing first and second sides 21 ,22 and opposing first and second faces 1 1 ,23.

An inlet port 12 may extend from the first end 13 of the cylinder head 10 to the first face 1 1 , for delivering inlet gases comprising air or a fuel/air mixture from an intake manifold of the engine into the cylinder. An exhaust port 14 may extend from the first face 1 1 of the cylinder head 10 to the second end 15, for delivering combusted exhaust gases from the cylinder to an exhaust manifold of the engine. One or more coolant inlet ports (not shown) may be provided in the first face 1 1 of the cylinder head 10, for routing coolant from the cylinder block (not shown) into the cylinder head 10. Preferably, four coolant inlet ports may be provided. A coolant outlet port 81 may be provided in the second face 23 of the cylinder head 10, for routing coolant from the cylinder head 10 to a coolant rail (not shown). A plurality of side ports 20 may be provided on the first side 21 and the second side 22 of the cylinder head 10, which may be plugged following manufacture of the cylinder head 10.

The cylinder head 10 may be mechanically connected to a rocker box 24 at the second face 23 of the cylinder head 10. The rocker box 24 may house a plurality of rocker arms (not shown) for actuating inlet and exhaust valves (not shown) provided respectively in the inlet port 12 and exhaust port 14. The inlet and exhaust valves may comprise poppet valves, having a valve base mounted on a valve stem, upon which a rocker arm may act. A rocker cover 25 may be mechanically connected to the rocker box 24.

A plurality of valve stem guides 30 may extend into the cylinder head 10 from a plurality of apertures in the first face 1 1 of the cylinder head. The arrangement of the valve stem guides 30 in the cylinder head 10 may correspond to the arrangement of the inlet and exhaust valves, which may be at diametrically opposed positions at four points, forming a diamond shape (see Figures 2 and 3).

A spark plug sleeve port 31 may also be provided in the first face of the cylinder head 10, through which a spark plug lead 32 may pass. The spark plug sleeve port 31 may be threaded. The spark plug sleeve port 31 may receive a pre-chamber spark plug (not shown), such as is available from Multitorch GmbH.

Figure 4 illustrates the shape of the inlet port 12 and the exhaust port 14. Further views illustrating the inlet port 12 are shown in Figures 5 to 7 and further views illustrating the exhaust port 14 are shown in Figures 8 to 10. It should be noted that the inlet and exhaust ports 12, 14 are in fact cavities in an otherwise solid mass of material, namely the cylinder head 10.

The inlet port 12 may comprise a main inlet passage 40, which may extend into the cylinder head 10 from the first end 13 of the cylinder head 10 generally towards the second end 15 of the cylinder head 10. The main inlet passage 40 may have a substantially square or rectangular cross-section (Figures 1 and 2), with rounded corners. At a point distal from the first end 13 of the cylinder head 10, the main inlet passage 40 may bifurcate into a first inlet passage 41 and a second inlet passage 42. The first and second inlet passages 41 ,42 may extend to the first face 1 1 of the cylinder head 10, where they may respectively terminate at first and second inlet valve holes 43,44. The first inlet passage 41 may be shorter than the second inlet passage 42 due to the relative positions of the first and second inlet valve holes 43,44. The cross-sectional area, and therefore the flow capacity, of the main inlet passage 40 may be greater than the cross-sectional area of both the first and second inlet passages 41 ,42, such that the main inlet passage 40 may not choke the flow of inlet gases. The cross sectional area, and therefore the flow capacities, of the first and second inlet passages 41 ,42 may not be equal to each other.

The first inlet passage 41 may comprise a helical inlet port, in which a throat portion immediately upstream of the first inlet valve hole 43 may comprise a helical ramp portion 50 surrounding the valve stem guide 30. The helical ramp portion 50 may comprise a top surface 51 , from which an outer wall 52 and an inner wall 53 may extend in a downwards direction. The outer wall 52 and the inner wall 53 may curve around the valve stem guide 30, such that the flow direction of gases passing through the helical ramp portion 50 may turn by more than 180°. The top surface 51 may have a width, which may decrease as the helical ramp portion 50 extends downstream towards the first inlet valve hole 43. The top surface 51 may generally have a width of from 7 mm to 13 mm. The outer and inner walls 52,53 may have a height, which may also decrease as the helical ramp portion extends downstream towards the first inlet valve hole 43. Due to the decreasing height of the outer and inner walls 52,53, the top surface 51 may slope downwards as the helical ramp portion 50 extends downstream, at an angle of from 55° to 63°, more preferably from 57.5° to 59.5°, and more preferably 58.4° relative to a longitudinal axis (not shown) through the centre of the first inlet valve hole 43. The number of turns of the helical ramp portion 50 may be substantially less than or equal to one full turn, wherein a full turn is a 360° revolution of the helical ramp portion 50 about a longitudinal axis of the helical ramp portion 50, wherein the longitudinal axis of the helical ramp portion 50 is the axis about which the helical ramp portion 50 turns. The inner wall 53 may merge with the valve stem guide 30 part-way along the helical ramp portion 50.

The second inlet passage 42 may be a substantially straight port, in which a throat portion 60 immediately upstream of the second inlet valve hole 44 may extend into a substantially linear portion 65. The second inlet passage 42 may be offset from the main inlet passage 40, with an elbow portion 61 connecting the substantially linear portion 65 with the main inlet passage 40. The elbow portion 61 may generally have a width of from 24 mm to 25 mm and a height of substantially 50 mm. The throat portion 60 may surround the valve stem guide 30. The throat portion 60 may comprise a swirl generating section 63, whereby a centre-point (not shown) of the throat portion 60 may be offset from a longitudinal axis (not shown) through the centre of the second inlet valve hole 44. A top surface 61 of the throat portion 60 may slope in a downwards direction as the throat portion 60 extends downstream towards the second inlet valve hole 44.

The exhaust port 14 may comprise a main exhaust passage 70, which may extend into the cylinder head 10 from the second end 15 of the cylinder head 10. The main exhaust passage 70 may have a substantially square or rectangular cross-section (Figure 3), with rounded corners. At a point distal from the second end 15 of the cylinder head 1 , the main exhaust passage 70 may bifurcate into a first exhaust passage 71 and a second exhaust passage 72. The first and second exhaust passages 71 ,72 may extend to the first face 1 1 of the cylinder head 10, where they may respectively form first and second exhaust valve holes 73,74. The first exhaust passage 71 may be shorter than the second exhaust passage 72 due to the relative positions of the first and second exhaust valve holes 73,74. The cross-sectional area, and therefore the flow capacity, of the main exhaust passage 70 may be greater than the cross-sectional area of both the first and second exhaust passages 71 ,72. Each of the first and second exhaust passages 71 ,72 may comprise a throat portion 75 immediately upstream of the first and second exhaust valve holes 73,74. As shown in Figures 1 1 to 13, a first coolant jacket 80 may be provided above the main inlet and exhaust passages 40,70, between the main inlet and exhaust passages 40,70 and the second face 23 of the cylinder head 10. The first coolant jacket 80 may be fluidly connected to the coolant outlet port 81 in the second face 23 of the cylinder head 10. A plurality of side ports 20 may be provided, which may be plugged following manufacture of the cylinder head 10. The first coolant jacket 80 may be shaped to fit around the valve stem guides 30 and the spark plug sleeve port 31 .

As shown in Figures 14 to 16, a second coolant jacket 90 may be provided below the main inlet and exhaust passages 40,70, between the main inlet and exhaust passages 40,70 and the first face 1 1 of the cylinder head 10. The second coolant jacket 90 may be fluidly connected to the one or more (preferably four) coolant inlet ports in the first face 1 1 of the cylinder head 10. A plurality of transfer apertures (not shown) may be provided between the second coolant jacket 90 and the first coolant jacket 80, such that coolant may pass from the second coolant jacket 90 to the first coolant jacket 80. A plurality of side ports 20 may be provided, which may be plugged following manufacture of the cylinder head 10. The second coolant jacket 90 may be shaped to fit around the throat portions 45,60,75 of the first and second inlet ports 41 ,42 and the first and second outlet ports 71 ,72 and the spark plug sleeve port 31 . Industrial Applicability

The cylinder head 10 has industrial applicability in the field of internal combustion engines, and particularly in the field of natural gas internal combustion engines. In use, inlet gases may pass from the intake manifold of the engine to the main inlet passage 40, and be divided between the first and second inlet passages 41 ,42. Inlet gases passing along the first inlet passage 41 may be caused to spiral down the helical ramp portion 50 towards the first inlet valve hole 43, such that a first swirl may be imparted to the inlet gases as they enter the cylinder. Inlet gases passing along the second inlet passage 42 may be provided with a degree of swirl due to the swirl generating section 63, and may additionally enter the cylinder in a direction tangential to an inner periphery of the cylinder, such that a second swirl may be imparted to the inlet gases as they enter the cylinder. The inlet gases entering the cylinder from the second inlet passage 42 may swirl around the inlet gases entering the cylinder from the first inlet passage 41.

The swirl number imparted to the inlet gases by the inlet port 12 may be

substantially 1.1 to 1 .3, preferably 1.2. As discussed above, swirl number assessment is well known in the art. Preferably, the swirl number is measured by the flow straightener method. Various companies can provide reproducible and comparable swirl data. The example provided herein was measured accordingly by AVL Tippelmann GmbH of

Neuenstadt am Kocher, Germany. The swirl imparted to the inlet gases in the cylinder by the first and second inlet ports 41 ,42 may generate an optimal level of turbulence within the cylinder. Following combustion of the inlet gases in the cylinder, the resulting exhaust gases may pass out of the cylinder via the first and second exhaust valve holes 73,74 respectively into the first and second exhaust passages 71 ,72, after which they may combine in the main exhaust passage 70, through which they may be directed out of the cylinder head 10 to the exhaust manifold of the engine. The flow coefficient of the outlet port may be 0.398 to 0.419.

Claims

CLAIMS;

1. A cylinder head for an infernal combustion engine, comprising;

an inlet port comprising:

a threaded spark plug sleeve port; and

first and second coolant jackets.

2. A cylinder head according to claim 1 , wherein the angle is selected from a range of from 57.5° to 59.5°.

3. A cylinder head according to claim 1 or claim 2, wherein the angle is 58.4°.

4. A cylinder head according to any one of the preceding claims, wherein a width of the surface decreases as the helical ramp portion extends downstream towards the first inlet valve hole.

5. A cylinder head according to any one of the preceding claims, wherein an outer wall and an inner wall extend from the surface in a direction towards the first inlet valve hole, the outer wall and the inner wall each having a height which decreases as the helical ramp portion extends downstream towards the first inlet valve hole.

6, A cylinder head according to any one of the preceding claims, wherein the helical ramp portion extends over less than one full turn.

7. A cylinder head according to any one of the preceding claims, wherein the second inlet passage further comprises a swirl generating section upstream of the second inlet valve hole.

8. A cylinder head according to any one of the preceding claims, wherein the second inlet passage is offset from the main inlet passage, and is connected thereto via an elbow portion.

9. A cylinder head according to any one of the preceding claims, wherein the inlet port has a swirl number selected from a range of 1.1 to 1.3.

10. A cylinder head according to any one of the preceding claims, wherein the inlet port has a swirl number of 1.2.

11. A cylinder head according to any one of the preceding claims, wherein the outlet port has a flow coefficient of from 0.398 to 0.419.

12. An internal combustion engine comprising a plurality of cylinders, each cylinder being associated with a respective cylinder head according to any one of claims 1 to 1 1.

13. An internal combustion engine according to claim 12, wherein the engine is a natural gas engine.