GB1561638A - Liquidcooling system of internal combustion engines - Google Patents

Description

(54) IMPROVEMENTS IN THE LIQUID COOLING SYSTEM OF INTERNAL COMBUSTION ENGINES (71) We, SHELL INTERNATIONALE RE SEARCH MAATSCHAPPIJ B.V., a company organized under the laws of the Netherlands, of 30 Carel van Bylandtlaan, The Hague, the Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a liquid cooling system of internal combustion engines in which sea water used as a liquid coolant, is conducted through a cooling space in the engine surrounding a cylinder liner.

The invention particularly but not exclusively relates to diesel engines in marine vessels, such as seagoing fishing boats.

Diesel engines are usually designed so that the inner wall of the cylinder liners operates within the temperature range 150 to 180"C.

This is achieved by removing heat from the outer wall of the cast iron cylinder liners by means of circulating fresh water, confined by a water jacket, and normally at a temperature of 60 to 800C. The significance of the temperature of the inside of the liner is that it is approximately that of the dew point of the sulphuric acid which is generated by the combustion of the sulphur present in the fuel as an impurity. Diesel engine lubricants in medium speed engines incorporate alkaline additives to neutralise the acid so formed.

With the moderate amount of acid generated at these high temperatures, the depletion of alkalinity is such that the lubricating oil remains in good condition, for this factor, typically from 1000 hours to 20,000 hours depending upon the sulphur content of the fuel.

It is known that many marine diesel vessels at least in some parts of the world, for the reason of simplicity, and more particularly fishing boats, which operate over a large area, use sea water cooling, and their cooling water systems are thus limited to a temperature of about 45 deg. C to avoid massive deposition of salt in the system.

As a result of the low water temperature, the temperature of the inner surface of the cylinder liner is correspondingly reduced, to the range 100 to 130 0C. Since these temperatures are well below the dew point of sulphuric acid, much larger quantities of acid are produced, resulting in a rapid depletion of the alkalinity of the lubricating oil, and minimal protection of the cylinder liners against corrosive wear.

In normal conditions, this situation could be met by drastically reducing the oil change period, however due to the absence of fishing boats away from base for up to 1 year, this is not operationally acceptable. Consequently, the engines deteriorate much more rapidly than might normally be expected.

An alternative could be to use a lubricating oil of very much higher alkalinity level, but this has the drawback, apart from the higher cost, of shortening the exhaust valve and turbocharger overhaul lives due to the higher lubricating oil ash content which is an unavoidable consequence of higher alkalinity.

The object of the invention is to provide an improved cooling system which affords a degree of cooling of the cylinder wall which prevents the above indicated deterioration of the lubricating oil using sea water as the coolant and at the same time also prevents salt deposition in the system.

To this end, according to the invention, in a cooling system of internal combustion engines as defined above, a heat transfer retarder is provided comprising a thermal insulating sleeve arranged between the outside surface of the cylinder liner and the cooling space.

Such a thermal insulation may be achieved by fitting a rubber or plastics sleeve on the outside surface of the cylinder liners. This provision would have the virtue of being cheaply and conveniently applicable as a retro-fit to existing engines during annual overhaul.

The invention may be carried out in various ways and a specific embodiment of the invention will be described by way of ex ample with reference to the drawing accompanying the Provisional Specification in which: Figure 1 is a sectional elevation through part of an internal combustion engine incorporating one form of the invention, the section being taken along the line I-I in figure 1; and Figure 2 is a sectional plan taken along the line Il-Il of Figure 1.

In the engine shown in the drawing, a cylinder liner 1 is surrounded by a cooling chamber 2 which comprises a cooling space 4 situated near the combustion chamber 3 and around the lower part of the cylinder liner.

The cooling space 4 is bounded on the one side by the exterior of the cylinder liner and on the other side by the interior of the water jacket 8.

Further main parts of the engine, such as the crankcase 5 and the fuel injection means 6 will not be described in detail, as being not of relevance for a clear understanding of the invention.

According to the invention an insulating sleeve 7 is provided and fitted against the outer surface of the cylinder liner 1.

The sleeve also may consist of several parts of different heat conductive properties, which case the part having the lowest heat conductivity is fitted in the upper part of the cooling space 4 adjacent to the combustion chamber 3.

A coolant inlet fitting 9 is connected to the water jacket 8 and communicates with the cooling space 4. Coolant enters the fitting 9 through a pipe 10 and passes into the cooling space 4. After flowing through the annular cooling space 4 the coolant passes out through an outlet conduit 11 in the water jacket 8, through a connection 12 leading to the cooling space 13 of the cylinder head 14 and then out through a pipe 15.

WHAT WE CLAIM IS 1. Liquid cooling system of internal combustion engines in which sea water, is conducted as a liquid coolant through a cooling space in the engine surrounding a cylinder liner, wherein a heat transfer retarder is provided comprising a thermal insulating sleeve arranged between the outside surface of the cylinder liner and the cooling space.

2. Liquid cooling system according to claim 1, wherein the sleeve consists of several parts of different heat conductive properties, the part having the Iowest heat conductivity being fitted in the upper part of the cooling space adjacent to the combustion chamber.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. ample with reference to the drawing accompanying the Provisional Specification in which: Figure 1 is a sectional elevation through part of an internal combustion engine incorporating one form of the invention, the section being taken along the line I-I in figure 1; and Figure 2 is a sectional plan taken along the line Il-Il of Figure 1. In the engine shown in the drawing, a cylinder liner 1 is surrounded by a cooling chamber 2 which comprises a cooling space 4 situated near the combustion chamber 3 and around the lower part of the cylinder liner. The cooling space 4 is bounded on the one side by the exterior of the cylinder liner and on the other side by the interior of the water jacket 8. Further main parts of the engine, such as the crankcase 5 and the fuel injection means 6 will not be described in detail, as being not of relevance for a clear understanding of the invention. According to the invention an insulating sleeve 7 is provided and fitted against the outer surface of the cylinder liner 1. The sleeve also may consist of several parts of different heat conductive properties, which case the part having the lowest heat conductivity is fitted in the upper part of the cooling space 4 adjacent to the combustion chamber 3. A coolant inlet fitting 9 is connected to the water jacket 8 and communicates with the cooling space 4. Coolant enters the fitting 9 through a pipe 10 and passes into the cooling space 4. After flowing through the annular cooling space 4 the coolant passes out through an outlet conduit 11 in the water jacket 8, through a connection 12 leading to the cooling space 13 of the cylinder head 14 and then out through a pipe 15. WHAT WE CLAIM IS

1. Liquid cooling system of internal combustion engines in which sea water, is conducted as a liquid coolant through a cooling space in the engine surrounding a cylinder liner, wherein a heat transfer retarder is provided comprising a thermal insulating sleeve arranged between the outside surface of the cylinder liner and the cooling space.

2. Liquid cooling system according to claim 1, wherein the sleeve consists of several parts of different heat conductive properties, the part having the Iowest heat conductivity being fitted in the upper part of the cooling space adjacent to the combustion chamber.