JP2008057546A - Cooling mechanism for cylinder jacket of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling mechanism where a cylinder sleeve coolant is partially adjusted in temperature in an upper part of a cylinder sleeve, and supplied at a temperature in a predetermined range in this type of cooling mechanism. <P>SOLUTION: In a cylinder cooling mechanism particularly for a large diesel engine, the coolant first passes through cylinder covers 5 and 7 and is preheated. The preheated coolant may then flows at a predetermined temperature to a plurality of coolant passages 11 and a gap chamber 12 of a cylinder sleeve 1. The preheating within the preset temperature range may be achieved with heat which is at least partially generated in the cylinder sleeve 1. By supplying the coolant adjusted in temperature, the inner wall 25 of the cylinder sleeve 1 is prevented from being cooled up to a temperature at which a highly-corrosive combustion product such as sulfurous acid is condensed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling mechanism for a cylinder of an internal combustion engine, and more particularly to a liquid cooling mechanism for a cylinder sleeve of a large diesel engine.

  Large diesel engines typically include multiple upright cylinders, for example. In known cooling mechanisms in large diesel engines, the coolant is designed specifically to flow from below to above. The relatively cool coolant immediately after the start of flow cools the cylinder wall first. The coolant then flows in the direction of the upper end of the cylinder sleeve or lining and then reaches the cylinder cover. Therefore, the coolant basically flows from the bottom to the top, except for a short path through which the coolant flows downward.

  This design has been made with particular consideration of the effect that the cooling liquid is heated by the cooling mechanism and the heated cooling liquid naturally flows upward. Natural convection caused by temperature and concentration differences assists the circulation of the coolant.

However, the cooling of the inner wall of the cylinder sleeve, in particular, is not done without any control. For example, in the combustion of fuels that contain a substantial amount of sulfur in addition to other combustion materials, sulfurous acid (H ₂ SO ₃ ) is produced.
Sulfurous acid has a dew point of 130 to 140 ° C., and at such a temperature, sulfurous acid liquefies. If the cylinder sleeve is overcooled, sulfurous acid will condense at the bottom of the cylinder sleeve. In this state, when a relatively low temperature coolant is introduced into the lower portion of the cylinder jacket, the temperature of the inner wall of the cylinder sleeve, which is already too low, tends to further decrease.

  The coolant flowing upward is further heated, while the coolant passes through the upper part of the cylinder sleeve and reaches the cylinder cover located further upward. The inner wall of the cylinder sleeve in the vicinity of the cylinder cover is substantially hot and there is virtually no risk of liquefying the corrosive combustion products. Therefore, it is precisely the upper part of the cylinder sleeve that requires particularly intensive cooling, i.e. strong cooling action. Conversely, it is desirable to limit the cooling at the middle and lower part of the cylinder sleeve, resulting in excessive cooling, resulting in a temperature drop that causes, for example, corrosive combustion products to condense on the cylinder surface. Should be avoided.

  It is an object of the present invention to provide an improved cooling mechanism, for example, in a cylinder sleeve of a large diesel engine. According to the present invention, the temperature of the cylinder sleeve coolant is partially adjusted at the upper part of the cylinder sleeve, while being supplied at a temperature within a predetermined range in this type of cooling mechanism. Further advantageous effects of the cooling mechanism which is a preferred embodiment are described in the dependent claims.

In order to solve the above problems, in the cooling mechanism of the present invention, the cooling liquid first passes through the cylinder cover and / or the upper part of the cylinder sleeve to cool them, whereby the cooling liquid itself is heated. At this time, the cylinder cover and the upper part of the cylinder sleeve, which are areas to be particularly strongly cooled, are already more intensively cooled because of the large temperature difference between the low-temperature coolant and the area. Next, the preheated coolant as described above is supplied to the middle and lower portions of the cylinder sleeve that need to be heated rather than cooled, for example, to prevent condensation of highly corrosive combustion products. Although heat exchange has already occurred by the preheated coolant, heat exchange is further performed by changing the flow conditions of the coolant, that is, the flow rate and the flow rate.

A cylinder sleeve cooling system according to an embodiment of the present invention, particularly its function, will be described below with reference to the drawings.
A cooling circuit for a cylinder sleeve 1 in a two-stroke large diesel engine will be described below with reference to FIG. The coolant is sent out by the circulation pump 2 at a constant flow rate, that is, a flow rate, passes through the inlet flow path 3 and the distributor ring 4 and reaches the cylinder cover, that is, the head 5. The coolant passes through a plurality of coolant flow paths (not shown) provided in the cylinder cover 5. The coolant inlet is disposed in the distributor ring 4 located at the lower edge of the cylinder cover 5. The coolant outlet 6 is disposed at the uppermost end of a valve basket or housing 7 provided so as to protrude from the cylinder cover 5.

  The coolant heated by the cylinder cover 5 and the valve basket 7 passes through the flow passages 8 and 9 and then through the distributor ring 10, and then passes through a plurality of coolant flow passages 11 located at the top of the cylinder sleeve 1. . During this time, the coolant is further heated. The coolant passes through a plurality of cooling holes provided in the sleeve 1, that is, a plurality of coolant flow paths 11, and further reaches a gap chamber 12 positioned below.

  The size of the gap chamber 12 formed in an annular shape between the sleeve 1 and the support ring 17 surrounding the sleeve 1 is set so that, for example, the flow rate of the coolant does not fall below a predetermined value that ensures the minimum possible flow rate. Is done. In view of the flow rates specified to date in known two-stroke large diesel engines, the cooling system according to the invention includes, for example, a gap chamber 12 having a distance in the range of up to 3 mm between the sleeve 1 and the support ring 17. is required.

In the embodiment shown in FIG. 1, the cooling liquid flows out of the gap chamber 12 through the radial outlet at the lower end of the support ring 17, and then introduced into the return channel 19 through the recovery ring 18.
A control throttle valve 13 for the coolant of the cylinder sleeve 1 is disposed between the inlet channel 9 and the outlet channel 19. The throttle valve 13 is controlled or regulated based on the temperature reference value of the inner wall 25 of the cylinder sleeve 1. When the throttle valve 13 is closed, all the coolant flows in the plurality of cooling holes 11 and the gap chamber 12 in the cylinder sleeve 1. Therefore, the heat exchange between the upper part of the cylinder sleeve 1 and the gap chamber 12 located below the cylinder sleeve 1 is most concentrated.

When the throttle valve 13 is open, only a part of the coolant flows in the cooling hole 11 of the cylinder sleeve 1 and the gap chamber 12 positioned below the cooling hole 11. Accordingly, the degree of heat exchange in the sleeve 1 decreases. When the throttle valve 13 is fully open, the minimum amount of coolant flowing through the cylinder sleeve 1 is determined by the size of the opening 14 disposed behind the throttle valve 13. A part of the coolant passes through the control throttle valve 13, the opening 14 and the temperature control valve 15 and flows into the cooler 16, and the correction amount (bypass)
Amount) is mixed with the coolant and collected in the circulation pump 2.

  The coolant is controlled so that the coolant temperature at the outlet 6 of the valve basket 7 is kept constant. The temperature difference between the inlet channel 3 and the outlet channel 8 varies depending on the total amount of heat to be removed from the cylinder cover 5, the valve basket 7 and the cylinder sleeve 1. The coolant inflow temperature in the cylinder cover 5 is lowest at the rated load of the engine and increases as the engine output decreases.

  The coolant temperature at the inlet to the cylinder sleeve 1, the flow path 9 and the distributor ring 4 is the same as the coolant temperature at the outlet 6 of the valve basket 7 (flow path 8). Therefore, the temperature in these regions is almost constant.

  The degree of heat exchange in the cylinder sleeve 1 is determined by the geometric characteristics of the holes 11 provided in the upper collar portion and the coolant flow rate in the gap chamber 12. The temperature of the inner wall 25 of the cylinder sleeve 1 and the temperature reference value for controlling the opening / closing of the throttle valve 13, that is, the flow rate of the coolant, are respectively the above-described design, that is, the dimension setting and arrangement method of the plurality of cooling holes 11, and It changes according to the dimension setting of the gap chamber 12 for circulating the coolant.

  The temperature control system (feedback control system) for the inner wall 25 of the cylinder sleeve 1 may be common to all cylinders or sets arranged in the engine, or an individual system may be provided for each cylinder. Only a single throttle valve 13 (shown in FIGS. 1 and 2) needs to be installed to control the temperature of each inner wall 25 in each cylinder of the engine. In principle, one throttle valve 13 is required for each cylinder in order to control the temperature in the inner wall 25 of each cylinder. In the temperature control of the cylinder inner wall 25 performed for each group, it is advantageous to provide one throttle valve 13 for each group.

  However, a method of setting the amount of the coolant flowing through each cylinder sleeve 13 only by setting the size of the opening 14 without using the throttle valve 13 to control the flow rate of the coolant flowing through each cylinder sleeve 1. Is also possible. Such a method can be employed when the temperature difference of the inner wall 25 of the cylinder sleeve 1 is very small over the entire usable temperature range, and control is not necessary. It is also conceivable to adjust the flow rate and cooling power of the cooling liquid to each requirement by regulating the discharge amount of the cooling liquid pump 2.

  In the cooling system according to the invention for a known large diesel engine, the structural design of the cylinder cover 5 is substantially the same as in the prior art. The difference is that the distributor ring 4 is provided at the entrance of the cylinder cover 5 and the distributor ring 10 is provided at the upper end of the cylinder sleeve 1.

  The structural design or sizing of the gap chamber 12 is based on adapting the inner diameter of the support ring 17 to the thickness of the inner wall 25 of the cylinder sleeve 1. The outer diameter of the support ring 17 need not be changed from the prior art dimensions.

  In an engine having a very long stroke, as shown in FIG. 2, the coolant is introduced into the lower portion of the support ring 17 and reaches the upper portion of the exhaust slit 20 provided in the extension gap chamber 12a located below.

In general, large diesel engines are said to have a long stroke when the ratio of piston stroke to cylinder bore length is greater than or equal to 1: 2 (stroke / bore ≧ 2).
When the minimum flow rate of the cooling liquid is reliably maintained in the entire space in which the cooling liquid flows, the sensitivity of the cooling system to the enclosed gas, air, and particularly bubbles is low. Also, the size of the cooling holes and gap chambers can be set so that the air, steam and bubbles that can be generated can move with the coolant.

A cyclone separator may be provided for effective ventilation and gas removal in the coolant. However, it is also possible to exhaust the gas from the cooling system via a ventilator 21 that operates automatically. The coolant consumed in the cooling system can be replenished from the coolant tank 22 by the supply pump 23. The cooling system of the present invention is equally suitable for both operation using an elevated tank and operation using a closed pressure chamber 24. In the elevated tank opened to the atmosphere with respect to the closed pressure chamber where the boiling point of the cooling liquid becomes higher under pressure, the temperature of the cooling liquid is regulated by the boiling point of the cooling liquid.

  In the known cooling system, the temperature of the coolant at the outlet 6 of the valve basket 7 is 80-90 ° C. For example, in known large diesel engines, a difference of 10-30 ° C. in the inflow and outflow temperatures of the cylinder coolant is standard. Therefore, in this embodiment, the temperature of the coolant is about 70 ° C. at the entrance of the cylinder jacket, and flows into the middle portion of the cylinder sleeve 1 at a relatively low temperature. As a result, the temperature of the inner wall 25 of the cylinder sleeve 1 becomes excessively low, so that the combustion material condenses on the inner wall 25 of the cylinder sleeve 1 and the above-described corrosion conditions that may cause engine damage occur.

  In the cooling system as described above, the coolant first flows through the cylinder cover 5 and the valve basket 7 and is preheated, that is, temperature-adjusted at this time, so that the temperature of the coolant when flowing into the cylinder sleeve 1 is changed. Will be higher. Therefore, when the coolant is discharged from the valve basket 7, the temperature of the coolant is, for example, 85 ° C. When flowing through the plurality of cooling holes 11 provided in the upper collar of the cylinder sleeve 1, the cooling liquid is further heated, and the temperature rises by, for example, 3 to 7 ° C. Accordingly, the intermediate portion of the cylinder sleeve 1 is cooled by a coolant having a temperature of 88 to 92 ° C., for example. This temperature is about 20 ° C. higher than in known cooling systems. Through cooling with a higher temperature coolant, the temperature of the inner wall 25 of the cylinder sleeve 1 can be made sufficiently high to keep it above the dew point where damaging corrosive combustion products are produced.

  In particular, the coolant is water in the aforementioned embodiment. In addition, additives for protecting against corrosion may be mixed in water. However, it is also possible to use an oil such as an engine lubricating oil or a separate cooling oil used in a circulation circuit separate from the lubricating oil as the cooling liquid. Since the specific heat varies depending on the type of coolant, it may be necessary to adapt the coolant flow path and / or the coolant flow rate. In order to facilitate the lubrication of the piston 1 ′ in the cylinder sleeve 1, it is appropriate to maintain the temperature of the inner wall 25 of the cylinder sleeve 1 relatively high. In this case, temperatures around 200 ° C. and higher are conceivable.

  However, for example, an area such as the cylinder cover 5 is cooled by the first coolant such as water, and another area such as the cylinder sleeves 1, 11, and 12 is cooled by the second coolant such as oil. A configured cooling system is also conceivable. In order to conduct heat and cool to a desired temperature, it is also possible to arrange a heat exchanger between the two sub-cooling systems.

  In the cooling liquid, that is, the cooling system of the present invention, the cooling liquid is heated by a part of the engine, in particular, the cylinder sleeve 1 by the cooling liquid.

  In the above-described embodiment, the “upper end / upper portion” in the cylinder space refers to a region near the top dead center and separated from the crankshaft. Similarly, “lower end / lower portion” in the cylinder bore refers to a region near the bottom dead center and close to the crankshaft. Therefore, the expressions “top”, “top”, “bottom”, and “bottom” are independent of the cylinder position. In addition, the expression “cylinder sleeve” refers to a general cylinder jacket regardless of whether the cylinder is actually provided with a cylinder sleeve or a cylinder having a different structure.

Particularly in the cooling of the cylinder sleeve 1 in a large diesel engine, the coolant is first introduced into the cylinder cover 5 and preheated. Next, the preheated coolant is introduced into the coolant flow path 11 and the gap chamber 12 of the cylinder sleeve 1 at a predetermined temperature. Heating up to a predetermined temperature range is performed through heat generated at least partially in a certain portion (coolant flow path 11) in the cylinder sleeve 1. By supplying the temperature-adjusted coolant, it is possible to prevent the temperature of the inner wall 25 of the cylinder sleeve 1 from reaching a temperature at which a highly corrosive combustion product such as sulfurous acid is condensed.

  As described above, according to the present invention, an improved cooling system in a cylinder sleeve of a large diesel engine, for example, can be provided. According to the present invention, the temperature of the cylinder sleeve coolant is partially adjusted at the top of the cylinder sleeve, while being supplied at a temperature within a predetermined temperature range in this type of cooling system.

The fluid circuit diagram which shows the cooling mechanism in which a cooling fluid flows only around the longitudinal direction upper part periphery of a cylinder sleeve. FIG. 2 is a fluid circuit diagram showing a state in which the coolant flows in most of the longitudinal direction of the cylinder sleeve until it reaches an exhaust slit provided for exhausting the cylinder in the cooling mechanism of FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cylinder sleeve, 1 '... Piston, 5, 7 ... Cylinder cover, 11 ... Coolant flow path.

Claims (10)

In a cooling mechanism for a cylinder of an internal combustion engine, in particular a cooling mechanism using a coolant for a cylinder sleeve (1) of a large diesel engine,
The first coolant is supplied to the cylinder cover (5), preheated to a predetermined temperature, and guided to the outside from the valve basket (7) of the cylinder cover (5).
The second coolant is supplied from the sub-cooling system to the cylinder sleeve (1),
The second coolant in the sub-cooling system is heated to a temperature within a predetermined temperature range in the heat exchanger by the preheated first coolant from the outlet (6) of the valve basket (7). Features a cooling mechanism.   The heat for preheating the second coolant for cooling the intermediate or lower portion of the cylinder sleeve (1) to a temperature within a predetermined range is generated by the cylinder cover (5, 7) or the cylinder sleeve (1). 2. The cooling mechanism according to claim 1, wherein the cooling mechanism is generated in a plurality of coolant flow paths (11) provided in an upper part.   The first coolant flows through the coolant channel (11) located in the top dead center region of the cylinder cover (5, 7) or the piston (1 ′) in the cylinder sleeve (1). The cooling mechanism according to claim 1, wherein the cooling mechanism is preheated there.   The second coolant in the cylinder sleeve (1) generally flows from the top dead center region of the piston (1 ′) to the bottom dead center region of the piston (1 ′). The cooling mechanism of any one of Claims 1-3.   The preselected temperatures of the first and second coolants are such that the temperature of the inner wall (25) of the cylinder sleeve (1) is above the dew point of the corrosive combustion products or exhaust in the cylinder combustion chamber. It is set, The cooling mechanism of any one of Claims 1-4 characterized by the above-mentioned.   The temperature of the first and second coolants is selected so that the temperature of the inner wall (25) is at least 130 ° C., preferably 135 ° C. or more, at least in the middle of the cylinder sleeve (1) in the combustion chamber. The cooling mechanism according to claim 5, wherein:   The cooling mechanism according to any one of claims 1 to 6, wherein the second coolant flows as a turbulent flow in at least a part of the cylinder sleeve (1).   The cylinder sleeve (1) is cooled by the cooling mechanism according to any one of claims 1 to 7, and the first and second coolant supply to each cylinder are individually or in groups. Or a large diesel engine commonly used for all cylinders.   9. The large diesel engine according to claim 8, wherein the first and second coolant supply operations performed in common for all cylinders, individually for each cylinder, or commonly for each set are automatically controlled.   The large diesel engine according to claim 8 or 9, wherein the cylinder is arranged upright.

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