JP2021148067A - Water jacket - Google Patents

Abstract

To provide a water jacket that can suppress knocking by performing efficient cooling and can prevent deterioration in a loss of a water pump.SOLUTION: A head inside cooling liquid passage 30 working as a water jacket comprises: a combustion chamber wall forming a combustion chamber 6 of a cylinder head 3; an intake port wall forming an intake port 7 continuing to the combustion chamber 6; an exhaust port wall forming an exhaust port 8a continuing to the combustion chamber 6; a main cooling liquid passage 31 that faces the combustion wall, intake port wall and exhaust port wall and works as a cooling liquid channel through which a cooling liquid flows; and a plurality of first ridges 101 and second ridges 103 extending in a direction orthogonal to a flowing direction of the cooling liquid that flows between the intake port wall and the exhaust port wall in the main cooling liquid passage 31. The first ridges 101 and the second ridges 103 are formed closer to the combustion chamber wall side than a boundary between the combustion chamber wall and at least one of the intake port wall and the exhaust port wall.SELECTED DRAWING: Figure 6

Description

The present invention relates to a water jacket that cools a cylinder head of an internal combustion engine.

Conventionally, the bottom wall of the water jacket of the cylinder head is provided with fins extending toward the center, and the wall portion on the lower surface side of the cylinder head defining the water jacket portion is curved toward the center of the cylinder from one side of the cylinder head. It is known that fins extending to the other side are bulged (see, for example, Patent Document 1). According to Patent Document 1, the heat dissipation effect can be enhanced by the fins, and the coolant can be brought to the center by the fins, so that the coolant can be prevented from stagnation at the edges.

Special Fair 7-103828 Gazette

The water jacket of the conventional cylinder head is set to have a uniform flow without stagnation in order to cool the cylinder head, and one of its roles is to improve the combustion efficiency by suppressing knocking. ing.

On the other hand, the shape of the water jacket has become complicated in recent years, and the coolant may partially stay and hinder the cooling.

As a countermeasure, by giving a protrusion shape like a fin to the wall surface in the flow path, the flow of the coolant is controlled to prevent retention, and the cooling performance is improved by expanding the contact area. If the optimum protrusion shape is not provided, the water pump efficiency will deteriorate due to the increase in pressure loss. Further, if the protrusion height is higher than necessary, the moldability of the water jacket core and the castability of the cylinder head are deteriorated, and the productivity is lowered.

In view of the above points, it is an object of the present invention to provide a water jacket capable of suppressing knocking by performing efficient cooling and preventing deterioration of loss of the water pump.

[1] In order to achieve the above object, the water jacket of the present invention can be used.
The combustion chamber wall that forms the combustion chamber of the cylinder head,
An intake port wall forming an intake port connected to the combustion chamber,
An exhaust port wall forming an exhaust port connected to the combustion chamber,
Facing the combustion chamber wall, intake port wall, and exhaust port wall, the coolant passage through which the coolant flows,
A plurality of ridges extending in a direction orthogonal to the flow direction of the coolant flowing between the intake port wall and the exhaust port wall in the coolant passage.
With
The ridge portion is characterized in that it is formed on the combustion chamber wall side of the boundary portion between the combustion chamber wall and at least one of the intake port wall and the exhaust port wall.

According to the present invention, the heat transfer efficiency can be improved by the ridge portion, and the cooling performance can be improved. Further, the wall rigidity is improved by the ridges formed on the wall surface, and the heat transfer efficiency can be further improved by thinning the wall surface.

[2] Further, in the present invention, the ridge portion is provided with a horizontal portion at the tip in the protruding direction, and a retaining portion recessed toward the proximal end side in the protruding direction is provided between the plurality of the ridge portions. Is preferable.

According to the present invention, the increase in pressure loss due to the formation of the ridge portion can be suppressed in the horizontal portion, and the heat transfer efficiency due to the coolant colliding with the ridge portion can be improved.

[3] Further, in the present invention, it is preferable that the ridge portion is formed on the combustion chamber wall between the intake port wall and the exhaust port wall.

According to the present invention, the rigidity around the combustion chamber can be improved by the ridge portion, and the wall of the combustion chamber can be made thin to improve the heat transfer efficiency.

[4] Further, in the present invention,
The cylinder head is assembled on the cylinder block, and the boundary portion between the mating surface of the cylinder head with the cylinder block and the bottom surface of the intake port wall and the boundary portion between the mating surface and the bottom surface of the exhaust port wall are formed. Prepare,
It is preferable that the ridge portion is formed at least at the boundary portion between the mating surface and the bottom surface of the exhaust port wall.

According to the present invention, the exhaust gas immediately downstream of the combustion chamber can be cooled, and the exhaust gas can be effectively cooled. In addition, the cylinder head around the valve seat can be effectively cooled.

[5] Further, in the present invention,
It is used in a multi-cylinder internal combustion engine having a cylinder head having a plurality of exhaust ports and an exhaust collecting portion for merging the exhaust ports.
A collecting part cooling liquid passage covering the exhaust collecting part is provided.
The cross-sectional area of the collecting portion cooling liquid passage is small and the surface area is large so that the cooling liquid flowing through the collecting portion cooling liquid passage has a higher flow velocity than the cooling liquid flowing through the cooling liquid passage. preferable.

According to the present invention, the exhaust heat can be reliably cooled by using the mainstream of the coolant as the exhaust collecting portion where the temperature becomes high. In addition, the combustion chamber can be reliably cooled by improving the heat transfer efficiency by the ridges. That is, the combustion chamber and the exhaust collecting portion can be appropriately cooled at a predetermined flow rate of the coolant.

FIG. 5 is a cross-sectional view of a main part of an internal combustion engine according to an embodiment of the present invention in a direction orthogonal to the cylinder row direction. A perspective view of the cylinder head as viewed from below. FIG. 3 is a cross-sectional view of the cylinder head shown along the line III-III in FIG. A perspective view of the cylinder head with the coolant passage extracted from diagonally above. A perspective view of the cylinder head with the coolant passage extracted from diagonally below. Explanatory drawing which shows the 1st ridge part of the main coolant passage. Explanatory drawing which shows the 2nd ridge part of the exhaust side coolant passage.

Hereinafter, embodiments in which the present invention is applied to an internal combustion engine for automobiles (hereinafter, simply referred to as engine E) will be described in detail with reference to the drawings. Hereinafter, the description will be made according to the vertical direction shown in FIG. 1 with reference to the state in which the engine E is mounted on the automobile.

As shown in FIGS. 1 and 2, the engine E is a SOHC 4-valve in-line 4-cylinder gasoline engine. As shown in FIG. 1, the engine E includes a cylinder block 2 in which four cylinders 1 in which pistons are housed are formed in a row, a box-shaped cylinder head 3 fastened to an upper portion of the cylinder block 2, and a cylinder head. A head cover 4 fastened to the upper part of the cylinder head 3 is provided, and the cylinder head 3 is mounted on an automobile in a posture of being arranged on the upper side in the vertical direction. The cylinder block 2 and the cylinder head 3 are cast from an aluminum alloy.

Each of the cylinders 1 extends substantially in the vertical direction and is formed in the cylinder block 2 in parallel with each other. Hereinafter, the arrangement direction of the plurality of cylinders 1 arranged in a row is referred to as a cylinder row direction. The upper end of each cylinder 1 opens to the upper end surface 2a of the cylinder block 2, and the lower end opens to a crank chamber (not shown) formed in the lower part of the cylinder block 2. On the side portion of the cylinder 1 of the cylinder block 2, an in-block coolant passage 5 (in-block water jacket) is formed so as to integrally surround the side peripheral portion of each cylinder 1. The in-block coolant passage 5 is curved along the side peripheral portion of each cylinder 1, and the upper end of the in-block coolant passage 5 is open to the upper end surface 2a of the cylinder block 2. The coolant passage 5 in the block is formed as a cavity by a sand mold or the like at the time of molding the cylinder block 2 in order to allow the cooling liquid such as cooling water, oil, and refrigerant to flow.

Combustion chamber recesses 3b, which are curved recesses, are formed on the joint surfaces of the cylinder head 3 with the cylinder block 2 (hereinafter, referred to as pair block joint surfaces 3a) facing each cylinder 1. Each combustion chamber recess 3b defines the combustion chamber 6 together with a portion above the piston of each cylinder 1. That is, the cylinder head 3 defines the upper edge of the combustion chamber 6.

Inside the cylinder head 3, the upstream end opens on one side surface (the left side surface in FIG. 1) along the cylinder row direction of the cylinder head 3, while the downstream end branched into two branches on the wall surface of each combustion chamber recess 3b. The four intake ports 7 that open and the upstream end open two on the wall surface of each combustion chamber recess 3b, while the downstream end opens on the other side surface (the right side surface in FIG. 1) along the cylinder row direction of the cylinder head 3. One exhaust collecting port 8 that opens is formed.

That is, the exhaust collecting port 8 has a plurality of (8) exhaust ports 8a that open in each combustion chamber recess 3b, and an exhaust collecting portion 8b that collects all the exhaust ports 8a inside the cylinder head 3. The exhaust collecting portion 8b forms a single exhaust outlet 8c on the other side surface of the cylinder head 3. With reference to the combustion chamber recess 3b, the side provided with the intake port 7 is the intake side, and the side provided with the exhaust collecting port 8 is the exhaust side.

In the cylinder head 3, an intake valve 9 that opens and closes each connection portion of the intake port 7 with the combustion chamber 6 and an exhaust valve 10 that opens and closes each connection portion of the exhaust collecting port 8 with the combustion chamber 6 are slidable. It is provided in. A valve operating chamber 11 is defined between the cylinder head 3 and the head cover 4, and the valve operating chamber 11 accommodates a valve operating mechanism 12 for opening and driving the intake valve 9 and the exhaust valve 10. .. The valve operating mechanism 12 includes a cam shaft 13 rotatably attached to the cylinder head 3, a rocker shaft 14 arranged above the cam shaft 13, an intake rocker arm 15 rotatably supported by the rocker shaft 14, and an exhaust rocker arm 16. Etc. The camshaft 13 is formed with four valve cams 13a for driving a pair of intake valves 9 and an exhaust valve 10 for each cylinder 1.

As shown in FIG. 2, the exhaust outlet 8c is formed at an intermediate position in the longitudinal direction on the exhaust side side surface 3c of the cylinder head 3. Further, in the center of the four intake ports 7 and the exhaust collecting port 8 on the wall surface of the combustion chamber recess 3b, a spark plug insertion hole 17 for inserting an ignition plug (not shown) penetrates the upper surface of the cylinder head 3. Is formed in.

As shown in FIGS. 1 and 2, the exhaust collecting portion 8b is formed on the exhaust side of the cylinder head 3 with respect to the block joint surface 3a. More specifically, the exhaust outlet 8c is defined by a tubular exhaust outlet tubular portion 18 projecting on the exhaust side side surface 3c of the cylinder head 3, and the exhaust outlet tubular portion 18 of the cylinder head 3 and its vicinity are formed in the cylinder block 2. On the other hand, the bulging portion 19 that bulges sideways to form the exhaust collecting portion 8b is formed.

The tip surface of the exhaust outlet tubular portion 18 forms a joint surface 18a of a downstream side exhaust passage member 20 such as a turbine of a supercharger (turbocharger) or an exhaust purification device (not shown). At the tip of the exhaust outlet tubular portion 18, a plurality of fastening bosses 21 for fastening the downstream exhaust passage member 20 with bolts are formed so as to surround the exhaust outlet 8c (four in the illustrated example). On the other hand, two ribs 22 are formed on the lower surface of the bulging portion 19 so as to reach the fastening boss 21 from the peripheral edge of the anti-block joint surface 3a. These ribs 22 extend in the front-rear direction, which is a direction in which they are close to each other and separate from the cylinder row, and have a C-shape that opens from the fastening boss 21 toward the block joint surface 3a.

As described above, downstream exhaust passage members 20 such as a supercharger and an exhaust purification device are arranged in front of the cylinder block 2 and the cylinder head 3, and these become high temperatures after the engine E is started. Therefore, the bulging portion 19 of the cylinder head 3 that bulges sideways with respect to the cylinder block 2 is likely to transfer heat from the supercharger or the exhaust purification device by heat conduction, radiation, and convection, and the lower surface thereof becomes particularly hot. Prone. When the lower surface of the bulging portion 19 becomes hot, the sealing property between the cylinder head 3 and the downstream exhaust passage member 20 tends to decrease due to deformation due to thermal expansion, but in the present embodiment, the lower surface of the bulging portion 19 tends to deteriorate. By forming the ribs 22 extending in the direction of proximity and separation from the cylinder row, the deformation of the bulging portion 19 is suppressed.

As shown in FIGS. 1 and 3 to 5, the inside of the cylinder head 3 is a recess in the combustion chamber in order to suppress a temperature rise due to heat propagation from the combustion gas in the combustion chamber 6 and the exhaust collecting port 8. In-head coolant passages 30 (31-39, in-head water jacket) are formed around 3b, the intake port 7 and the exhaust collecting port 8. The coolant passage 30 in the head is also formed as a cavity by a sand mold or the like when the cylinder head 3 is molded in order to allow the coolant such as cooling water, oil, and refrigerant to flow. However, in FIGS. 4 and 5, the cylinder head 3 is formed. The coolant passage 30 in the head, which is a space portion, is substantially shown.

The in-head coolant passage 30 includes a main coolant passage 31, an upper exhaust side coolant passage 32, a lower exhaust side coolant passage 33, an exhaust side connecting passage 34, an intake side coolant passage 35, an intake side connecting passage 36, and the like. Is the main element. The main coolant passage 31 extends in the cylinder row direction (longitudinal direction) of the cylinder head 3 so as to pass above and near the plurality of combustion chamber recesses 3b. The upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 are arranged so as to sandwich the exhaust collecting portion 8b from above and below, and extend in the longitudinal direction of the cylinder head 3, respectively. The exhaust side connecting passage 34 communicates the main coolant passage 31, the upper exhaust side coolant passage 32, and the lower exhaust side coolant passage 33. The intake side coolant passage 35 is arranged below the intake port 7 and extends in the longitudinal direction of the cylinder head 3. The intake side connecting passage 36 communicates the main coolant passage 31 with the intake side coolant passage 35.

The broken line in FIG. 2 indicates a portion where the upper end of the coolant passage 5 in the block contacts when the cylinder block 2 and the cylinder head 3 are fastened. In the coolant passage 5 in the block, the coolant flows as shown by the white arrows. At one end in the cylinder row direction, the upper end of the in-block coolant passage 5 is in contact with the block joint surface 3a, and extends upward from the in-block joint surface 3a in the cylinder head 3 to communicate with the in-head coolant passage 30. Two cooling liquid inflow passages 37 are formed. The two coolant inflow passages 37 communicate with the exhaust side connecting passage 34 and the intake side connecting passage 36 arranged on one end side of the cooling liquid passage 30 in the head in the cylinder row direction, respectively, and the coolant passage 5 in the block 5 Inflow of coolant from.

Further, of the broken line portion where the upper end of the coolant passage 5 in the block is in contact with the joint surface 3a against the block, the other end side in the cylinder row direction from the coolant inflow passage 37 is inside the cylinder head 3 from the joint surface 3a against the block. A bypass passage 38 is formed at an appropriate position so as to extend upward and communicate with the coolant passage 30 in the head. The bypass passage 38 communicates with the exhaust side connecting passage 34, the lower exhaust side coolant passage 33, the intake side connecting passage 36, or the intake side coolant passage 35 of the in-head coolant passage 30. Each bypass passage 38 is formed to have a smaller flow path cross-sectional area than the coolant inflow passage 37.

As shown in FIGS. 4 and 5, a coolant is applied to the other end of the upper exhaust side coolant passage 32 in the cylinder row direction (the end different from the side where the coolant inflow passage 37 is provided). A coolant outflow passage 39 for discharging from the passage 30 is formed. The outer end of the coolant outflow passage 39 communicates with a radiator (not shown) via a pipe, a hose, or the like. In the main coolant passage 31, the upper exhaust side coolant passage 32, the lower exhaust side coolant passage 33, and the intake side coolant passage 35, the coolant flows in the cylinder row direction as shown by the black arrows in FIG.

As shown in FIG. 6, a main coolant passage facing the combustion chamber wall defining the combustion chamber 6, the intake port wall defining the intake port 7, and the exhaust port wall defining the exhaust port 8a, and through which the coolant flows. 31 is located on the combustion chamber wall between the intake port wall and the exhaust port wall, and is in a direction orthogonal to the flow direction of the coolant flowing between the intake port wall and the exhaust port wall in the main coolant passage 31. A plurality of first ridges 101 extending to the surface are provided.

As shown in FIG. 7, a plurality of second ridges 103 are provided between the adjacent exhaust side connecting passages 34 and / or between the adjacent intake side connecting passages 36.

The first ridge portion 101 and the second ridge portion 103 are provided with horizontal portions 101a and 103a at the tip in the protruding direction. Further, between the adjacent first ridges 101 and the adjacent second ridges 103, retention portions 101b and 103b recessed toward the base end side in the protruding direction are provided.

In the present embodiment, the first ridge portion 101 and the second ridge portion 103 are set to have a protruding height of 0.25 mm, a width of 0.5 mm to 2.0 mm, and an interval of 2.5 mm to 7.5 mm. The ridge portion of the present invention is not limited to this numerical value, and is preferably set as appropriate according to the type and specifications of the engine E, the shape of the water jacket, and the like.

Further, the in-head coolant passage 30 as the water jacket of the present embodiment includes an upper exhaust side coolant passage 32 and a lower exhaust side coolant passage 33 as a collecting portion cooling liquid passage covering the exhaust collecting portion. ..

The coolant flowing through the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 as the collecting portion coolant passage is higher (faster) than the flow velocity of the coolant flowing through the main coolant passage 31 as the coolant passage. As a result, the cross-sectional area of the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 is small, and the surface area is large.

According to the in-head coolant passage 30 as the water jacket of the present embodiment, the heat transfer efficiency can be improved by the first ridge portion 101 and the second ridge portion 103, and the cooling performance can be improved. Further, the wall rigidity is improved by the first ridge portion 101 and the second ridge portion 103 formed on the wall surface of the in-head coolant passage 30, and heat transfer is performed by thinning the wall defining the in-head coolant passage 30. Efficiency can also be improved.

Further, according to the present embodiment, by forming the first ridge portion 101 and the second ridge portion 103, the increase in pressure loss can be suppressed by the horizontal portions 101a and 103a at the tip in the protruding direction, and the water The heat transfer efficiency can be improved by causing the coolant flowing in the cooling liquid passage 30 in the head as a jacket to collide with the side surfaces of the first ridge portion 101 and the second ridge portion 103.

Further, the coolant flowing in the cooling liquid passage 30 in the head flows to the retention portions 101b and 103b after passing over the first ridge portion 101 and the second ridge portion 103.

Further, in the present embodiment, the first ridge portion 101 is formed on the combustion chamber wall defining the combustion chamber 6 between the intake port wall defining the intake port 7 and the exhaust port wall defining the exhaust port 8a. There is. The first ridge portion 101 can improve the rigidity of the combustion chamber wall around the combustion chamber 6, and can improve the heat transfer efficiency by making the combustion chamber wall thin.

Further, in the present embodiment, the cylinder head 3 is assembled on the cylinder block 2, and the cylinder head 3 is the boundary portion between the mating surface with the cylinder block 2 and the bottom surface of the intake port wall, and the cylinder. It is provided with a boundary portion between the mating surface with the block 2 and the bottom surface of the exhaust port wall.

As shown in FIG. 7, the second ridge portion 103 is provided at a boundary portion between the mating surface with the cylinder block 2 and the bottom surface of the intake port wall, and a boundary portion between the mating surface with the cylinder block 2 and the bottom surface of the exhaust port wall. It is formed. As a result, according to the present embodiment, the exhaust gas directly below the exhaust port 8 facing the combustion chamber 6 can be cooled, and the exhaust gas can be effectively cooled. Further, the area around the valve seat facing the combustion chamber 8 can be effectively cooled. The second ridge portion of the present invention may be formed at least at the boundary between the mating surface with the cylinder block 2 and the bottom surface of the exhaust port wall, and the mating surface with the cylinder block 2 and the intake port wall are not necessarily formed. It is not necessary to provide the second ridge portion at the boundary portion with the bottom surface.

Further, the in-head coolant passage 30 as the water jacket of the present embodiment is a multi-cylinder internal combustion engine including a cylinder head 3 having a plurality of exhaust ports 8a and an exhaust collecting portion 8b for merging the exhaust ports 8a. It is used for the engine E as a.

The in-head coolant passage 30 includes an upper exhaust side coolant passage 32 and a lower exhaust side coolant passage 33 as a collecting portion cooling liquid passage covering the exhaust collecting portion 8b.

The coolant flowing through the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 as the collecting portion coolant passage is higher (faster) than the flow velocity of the coolant flowing through the main coolant passage 31 as the coolant passage. As a result, the cross-sectional area of the upper exhaust side coolant passage 32 and the lower exhaust side coolant passage 33 is small, and the surface area is large.

According to this embodiment, the exhaust heat can be reliably cooled by using the exhaust collecting portion 8b, which has a high temperature, as the main flow of the coolant. Further, the combustion chamber 6 can be reliably cooled even with a small flow rate by improving the heat transfer efficiency by the first ridge portion 101 and the second ridge portion 103. That is, the combustion chamber 6 and the exhaust collecting portion 8b can be appropriately cooled with a predetermined flow rate of the coolant.

Although the description of the specific embodiment is completed above, the present invention can be widely modified without being limited to the above embodiment. For example, in the above embodiment, the present invention is applied to a 4-valve in-line 4-cylinder gasoline engine for automobiles, but it may be applied to a different type of internal combustion engine used for other purposes. Further, in the above embodiment, only one exhaust outlet 8c is formed, but two exhaust outlets 8c are formed for each of two cylinders adjacent to each other, and a plurality of exhaust collecting portions 8b are formed in the cylinder head 3. You may. In addition, the specific configuration, arrangement, quantity, angle, and the like of each member and portion can be appropriately changed as long as they do not deviate from the gist of the present invention. On the other hand, not all of the components of the cylinder head 3 according to the present invention shown in the above embodiment are indispensable, and may be appropriately selected.

1 Cylinder 2 Cylinder block 3 Cylinder head 3S Side wall 6 Combustion chamber 7 Intake port 8 Exhaust collection port 8a Exhaust port 8b Exhaust collection part 8c Exhaust outlet 11 Valve chamber 18 Exhaust outlet Tubular part (the part that defines the exhaust outlet)
19 Swelling part 30 Coolant passage in the head 32 Upper exhaust side coolant passage 33 Lower exhaust side coolant passage 101 1st ridge 101a Horizontal part 101b Retention part 103 2nd ridge 103a Horizontal part 103b Retention part E engine

Claims (5)

The combustion chamber wall that forms the combustion chamber of the cylinder head,
An intake port wall forming an intake port connected to the combustion chamber,
An exhaust port wall forming an exhaust port connected to the combustion chamber,
Facing the combustion chamber wall, intake port wall, and exhaust port wall, the coolant passage through which the coolant flows,
A plurality of ridges extending in a direction orthogonal to the flow direction of the coolant flowing between the intake port wall and the exhaust port wall in the coolant passage.
With
The water jacket is characterized in that the ridge portion is formed on the combustion chamber wall side of the boundary portion between the combustion chamber wall and at least one of the intake port wall and the exhaust port wall. The water jacket according to claim 1.
The water jacket is characterized in that the ridge portion is provided with a horizontal portion at the tip in the protruding direction, and a retaining portion recessed toward the proximal end side in the protruding direction is provided between the plurality of ridge portions. In the water jacket according to claim 2.
A water jacket characterized in that the ridge portion is formed on a combustion chamber wall between an intake port wall and an exhaust port wall. In the water jacket according to claim 2 or 3.
The cylinder head is assembled on the cylinder block, and the boundary portion between the mating surface of the cylinder head with the cylinder block and the bottom surface of the intake port wall and the boundary portion between the mating surface and the bottom surface of the exhaust port wall are formed. Prepare,
The water jacket is characterized in that the ridge portion is formed at least at a boundary portion between the mating surface and the bottom surface of the exhaust port wall. In the water jacket according to claim 3,
It is used in a multi-cylinder internal combustion engine having a cylinder head having a plurality of exhaust ports and an exhaust collecting portion for merging the exhaust ports.
A collecting part cooling liquid passage covering the exhaust collecting part is provided.
The cross-sectional area of the collecting portion cooling liquid passage is small and the surface area is large so that the cooling liquid flowing through the collecting portion cooling liquid passage has a higher flow velocity than the cooling liquid flowing through the cooling liquid passage. The characteristic water jacket.

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