Diesel cooling system. Ship repair from A to Z: internal combustion engine cooling system Fresh water cooling system

These heat exchangers designed for cooling heated liquids and gases ( drinking water, lubricating oil, outside air, etc.). Especially important For normal operation of the ship's power plant, they have oil coolers designed to cool the oil heated during the lubrication of the main engine, auxiliary mechanisms and individual shafting units.

In Fig. 32 shows the design of a tubular oil cooler, the most common in sea ​​vessels. The oil cooler consists of a steel cylindrical body 5, upper and lower covers 1, two tube plates 2, diaphragms 10, cooling tubes 4 and tie rods 12. Flanges are welded to the body at both ends, to which the covers are attached using studs. Brass tubes 4 are flared in the tube plates, through which cooling sea water flows. To allow thermal expansion of the tubes, the lower tube plate is made movable; together with the bottom 1, it can move in the gland 13. The oil to be cooled enters the oil cooler body through the upper pipe 6 and washes the tubes from the outside. To better wash the tubes with oil, diaphragms 10 are installed inside the housing, which force the oil flow to change direction several times. The cooled, less viscous oil for lubricating the bearings of the shaft line and turbines is discharged through the middle pipe 11, and the more viscous oil for lubricating the gearbox is discharged through the lower pipe 3.

Rice. 32. Oil cooler.

There is a partition in the cavity of the top cover, so the cooling water, having entered the receiving pipe 8 of the top cover, goes down through pipe 9, and then rises up through the cooling pipes and is discharged overboard through pipe 7 of the top cover.

To control oil pressure and temperature, the oil cooler is equipped with instruments and fittings.

Modern ships are equipped with air conditioning units, which include air coolers. The operating principle of an air cooler is similar to an oil cooler. In a welded steel body, usually rectangular section, insert tube sheets with tubes rolled into them, having ribs along outer surface to increase the cooling surface. Covers are attached to the body on both sides. Cooling water or other liquid (for example, brine) flows through the tubes, and air enters the body of the cooler and, after cooling, is directed into the room to be cooled. In the cold season, an air cooler can work as an air heater if hot rather than cold water is passed through the tubes.

In addition to those mentioned, there are coolers of other designs: oil coolers with telescopic tubes, water coolers and air coolers with tubes made in the form of coils.

Cooling systems power plant are used to remove heat from working bushings, covers, pistons of main and auxiliary diesel engines, to cool oil and air (in supercharged engines). In modern diesel installations there are four such systems:

1) fresh water cooling system for cylinder liners, covers and gas turbines;

2) fresh water or oil cooling systems for piston heads;

3) cooling system with fresh water, oil or fuel for injectors;

4) sea water cooling system fresh water and oils in cooling and lubrication systems and air cooling in the charging system.

Fundamental cooling system diagram depends on the type of liquid, cooling nozzles and pistons. Engines with pistons cooled by oil and injectors cooled by fuel have one fresh water circuit, which serves to cool the bushings, covers, cylinders and gas turbine heater housings; for cooling pistons; for cooling the injectors.

Each circuit is served by its own circulation pumps, heat exchangers and expansion tank. The main advantage of such a system is that the fresh water cooling the cylinders is not contaminated by oil entering the system from the surface of the pipes of the telescopic piston cooling device, and by fuel, which can enter the water through the injector connector plane.

The schematic diagram of the fresh water circuit (Fig. 3) for cooling cylinders and gas turbine compressors (GTC) includes circulation pumps 5, expansion tank 13, water coolers 4 connected in parallel, bypass valve 3 controlled by a temperature sensor, water collectors 7 and 1. The pumps supply water to manifold 7, from where it is supplied for cooling the cylinders and housings 8 of the GTK and exits into manifold 1. The water leaving the engine and housings of the GTK can be passed through water coolers or some of the water can be passed through bypass valve 3 into the receiving cavity of the pumps in addition to the water cooler, maintaining a given temperature in all engine operating modes. Pipe 10 connects the receiving cavities of the pumps with the expansion tank, providing the necessary pressure. Air and water vapor, together with water, are removed from the cooling cavities of the engine and gas turbine complex through pipes 15 into the expansion tank. Pipe 12 serves to replenish water in the system. Along pipe 11, which has a sight glass. In case of overflow, water from the expansion tank is poured into the double-bottom tank. Air and water vapor are removed from the system into the atmosphere through pipe 14. When preparing the main engine for start-up hot water, leaving the cooling system of diesel generators, enters manifold 7. When the main engine is running, diesel generators can be cooled with water, which is discharged through pipes 2,9 or 6.

Rice. 3 Schematic diagram of the fresh water circuit of the cooling system.

Fresh water system, like the sea water system, is serviced by the main fresh water pump while underway, and by a port fresh water pump when stationary. For ships with an unlimited navigation area, two water coolers are installed in the cooling system, each of which provides heat removal at a main engine load of 60%, auxiliary engines 100% and a seawater temperature of 30 0 C.

The water pressure in the cooling system for each type of installation is indicated in the instructions. It is 0.15-0.25 MPa, and the pressure in the fresh water system should be 0.03-0.05 MPa greater than in the sea water system. This is necessary so that if the density of the refrigerators is violated, sea water cannot enter the fresh water system.

The temperature of incoming and outgoing water is also indicated in the instructions. It should be within 50-60 0 C at the inlet and 60-70 0 C at the outlet. In high-speed trunk diesel engines, the water temperature at the outlet of the diesel engine is maintained within 75-90 0 C. The temperature of fresh water in the cooling system is regulated by bypassing the water leaving the diesel engine past the water cooler into the suction line of pump 5. The water bypass is carried out by a temperature regulator, which opens valve 3 or flap for bypassing water past the refrigerator.

Outboard system diagram water is shown in Fig. 4. Water from the onboard 10 or bottom 12 kingstons through filters 11 is supplied to the sea water pumps 9. The operating pump supplies it to water-water coolers 6, oil coolers 7 and air cooler 4. All heat exchangers are connected in parallel. Oil cooler 7 and air cooler 4 have bypass pipelines 5, which make it possible to regulate the temperature of the oil and purge air by bypassing some of the water past the coolers. Through clinkers 1 of the right and left sides, water goes overboard. Recirculation pipeline 2, when floating in ice, transfers part of the water into the sea chest, from where it, together with the water coming from the king stone, is directed into the receiving cavity of the pump. This prevents interruption of the water supply when the kingston is clogged. fine ice or when its receiving grid freezes. To pump all heat exchangers, a ballast pump 8 is used, which receives water from the bow tanks, supplies it through the sea water system, and then through pipe 3 it goes to the stern tank. Knowing the performance of the pump and the capacity of the tanks, they alternately pump water from bow to stern and back without stopping the pump. Through pipes 13, water is used to pump heat exchangers of diesel generators and compressors.

To ensure normal lubrication of engine cylinders, it is necessary that the temperature on the inner surface of their walls does not exceed 180-200°C. In this case, coking of the lubricating oil does not occur and friction losses are relatively small.

The main purpose of the cooling system is to remove heat from the liners and cylinder covers and, in some engines, from the piston heads, to cool the circulating oil and to cool the air during supercharging of diesel engines. The injector cooling system is autonomous.

Modern diesel units have a dual-circuit cooling system consisting of a closed fresh water system that cools the engines, and open system outboard, which, through heat exchangers, removes heat from fresh water, oil, charge air and directly from some elements of the installation (shaft bearings, etc.).

Freshwater systems themselves are divided into three main cooling subsystems:

Cylinders, covers and turbochargers;

Pistons (if they are cooled with water);

Nozzles (if they are cooled with water);

The cooling system for cylinders, covers and turbochargers can have three designs:

When the vessel is moving, cooling is carried out by the main pump, and when stationary - by the parking pump; Before starting, the main engine is warmed up with water from

diesel generators;

The main engine and diesel generators have separate systems, with each diesel generator equipped with an independent pump and a cooler common to all diesel engines;

Each of the diesel engines is equipped autonomous system cooling.

The most rational is the first version of the system, where high operational reliability and survivability are ensured by a minimum number of pumps, coolers, and pipelines. In the general case, the fresh water system includes two main pumps - the main pump, the backup one (the model uses a seawater pump), one parking (port) pump, one or two coolers, thermostats (regulation by bypassing fresh water through the refrigerator), expansion tanks (compensation changes in the volume of fresh water in a closed system when the temperature changes, replenishment of the amount of water in the system), deaerators

(removal of dissolved air), pipelines, vacuum desalination plants, instrumentation.

Figure 1 shows circuit diagram dual-circuit cooling system. Circulation pump II fresh water is supplied to the water cooler 8, after which it enters the cavities of the working bushings 19 and the cover 20. Heated water from the engine is supplied through pipeline 14 to pump II and again to cooler 8. The highest located section of pipeline 14 is connected by pipe 7 to the expansion tank 5, which communicates with the atmosphere. The expansion tank ensures that the circulating engine cooling system is filled with water. At the same time, air from this system is removed through the expansion tank.

To reduce the corrosiveness of fresh water, a solution of chromium (potassium dichromate K2Cr2O7 and soda) is added to it in an amount of 2-5 g per liter of water. The solution is prepared in a mortar barrel 6, and then lowered into the expansion tank 5. To regulate the temperature of fresh water supplied to the engine, a thermostat 9 is used, which bypasses water in addition to the water cooler.

The fresh water circulation system has a backup pump 10 connected in parallel to the main pump II.

Sea water for cooling is received through the side or bottom seawall 1. From the seawater, through filters 18 that retain particles of silt, sand and dirt, it flows to the sea cooling water pump 16, which supplies it to the oil cooler 12 and water cooler 8, as well as through pipe 15 for cooling compressors, shafting bearings and other needs. But bypass pipeline 13 can allow water to pass past the oil cooler. The heated water after the water cooler 8 is discharged overboard through the outflow sea valve 4. If the temperature of the sea water is excessively low and if broken ice In the receiving seawalls, part of the heated water through pipeline 2 can be transferred into the suction line. The flow of heated water is regulated by valve 3.

The seawater cooling system has a backup pump 17 connected in parallel to the main pump 16. In some cases, one backup pump is installed for seawater and fresh water.

Sea water containing chloride, sulfate and nitrate salts is especially corrosive. Corrosivity sea ​​water 20-50 times higher than fresh water. On ships, seawater cooling system pipelines are sometimes made of non-ferrous metals. To reduce the corrosive effects of sea water inner surface steel pipes cover

Rice. I Cooling system diagram

zinc, bakelite and other coatings. The temperature in sea water systems should not be allowed above 50-550C, since with more high temperature salt precipitation occurs. The pressure in the sea water system created by the pumps is in the range of 0.15-0.2 MPa, and in the fresh water system 0.2-0.3 MPa.

The temperature of the sea water at the entrance to the system depends on the temperature of the water in the pool where the ship floats. The calculated temperature is 28-30°C. The fresh water temperature at the engine inlet is taken to be in the range of 65-90°C, with the lower limit referring to low-speed engines and the upper limit to high-speed engines. The temperature difference between the temperature at the outlet and inlet to the engine is taken Δt=8-100C.

To create static pressure, the expansion tank is installed above the engine. The cooling system is filled from the ship's general fresh water system.

The USSR Register rules for fresh water cooling systems allow the installation of a common expansion tank for a group of engines. The piston cooling system must be serviced by two pumps of equal capacity, one of which is a reserve one. The same requirement applies to the injector cooling system.

If a vacuum desalination plant is included in the system, disinfection devices should be provided. The resulting distillate can be used for technical, sanitary and domestic needs. Evaporation installations must be made as a single unit, have automation and must be operated without a special watch.

The sea cooling water system, which includes a second circuit of the engine cooling system, is designed to reduce the temperature of fresh water, oil and charge air of the main engine and diesel generators, auxiliary equipment machine and boiler rooms (compressors, steam condensers, evaporators, refrigeration units), propeller shaft bearings, deadwood, etc. This system can be implemented according to a scheme with a serial or parallel arrangement of heat exchangers.

The requirements of the USSR Register Rules for the sea cooling water system regarding the redundancy of units are similar to the requirements for the fresh water system.

Self-test questions

1. From what parts and assemblies is the heat of the diesel cooling system removed?

2. How are fresh cooling water systems classified?

3. What options does the cooling system have for cylinders, covers and turbochargers?

4. What units and devices are included in the fresh cooling water system?

5. The same for the sea cooling water system?

6. What functions does the expansion tank perform?

7. How is the temperature of fresh water regulated?

8. Which units in the cooling system must be backed up?

9. What are the parameters of fresh and sea water of the cooling system?

10. For what purposes is the distillate obtained in a vacuum desalination plant used?

11. What are the requirements of the USSR Register Rules for fresh and sea water systems.

12. Why is a dual-circuit circuit used to cool the engine?

Cooling system designed to remove heat from engine parts subject to heating by hot gases and to maintain permissible temperatures, determined by the heat resistance of materials, the thermal stability of oil and optimal conditions progress of the work process. Depending on the design of the internal combustion engine, the amount of heat dissipated into the coolant is 15-35% of the heat released during fuel combustion in the cylinders.
Fresh and sea water, oil and diesel fuel are used as coolant.
For marine internal combustion engines, flow and closed cooling systems are used. At flow system The engine is cooled by sea water pumped by a pump. The sea water system includes the following main elements: sea chests with sea water, filters, pumps, pipelines, fittings and control, alarm and monitoring devices. According to the USSR Register Rules, the system must have one bottom and one or two side seams. The sea water system may have two pumps, one of which is a backup pump for both fresh and sea water. Emergency cooling of engines can be provided from refrigeration pumps or fire system vessel.
The flow cooling system is simple in design and requires small amount pumps, but the engine is cooled by relatively cold sea water (no more than 50-55 C). The temperature cannot be maintained higher, since already at 45 C intensive deposition of salts begins on the cooling surface. In addition, all cavities of the system in which cooling seawater flows become heavily contaminated with sludge. Deposits of salts and sludge significantly impair heat transfer and disrupt normal engine cooling. The washed surfaces are subject to significant corrosion.
Modern marine internal combustion engines usually have closed (double-circuit) system cooling, in which fresh sea water circulates in the engine, cooled in special water coolers. Water coolers are pumped with sea water.
One of the main advantages of this system is the ability to keep the cooled cavities in a cleaner state, since the system is filled with fresh or specially purified water. This in turn makes it easy to maintain the most favorable cooling water temperature depending on the engine operating mode. The temperature of fresh water leaving the engine is maintained as follows: for low-speed internal combustion engines 65-70 C, for high-speed engines - 80-90 C. A closed cooling system is more complex than a flow one and requires increased energy consumption to operate the pumps.
To protect the surfaces of bushings and blocks on the cooling side from corrosion-cavitation destruction and scale formation, anti-corrosion emulsion oils VNIINP-117/119, Shell Dromus Oil B and others are used. These oils have almost identical physical and chemical properties and methods of application. They are non-toxic and are stored in metal containers at a temperature not lower than minus 30 C.
Anti-corrosion oils form a stable, opaque emulsion with fresh water milky. The durability of the emulsion also depends on the hardness of the water. A thin film of anti-corrosion oil, covering the cooling surface of the internal combustion engine, protects it from corrosion, cavitation destruction and scale deposits. To maintain this film on the engine cooling surface, it is necessary to constantly maintain a working oil concentration in the cooling water of about 0.5% and use water of a certain quality.
Anti-corrosion emulsion oils are widely used in internal combustion engine cooling systems used on fishing vessels. Methods for treating fresh cooling water are given in the engine operating instructions.
Cooling systems use electrically driven centrifugal pumps. Sometimes there are piston pumps that are driven by the internal combustion engine itself. Cooling pumps create a pressure of 0.1-0.3 MPa. Cooling of modern medium-speed internal combustion engines is carried out mainly using mounted centrifugal pumps for sea and fresh water.
A schematic diagram of a closed engine cooling system is shown in the figure:

A closed internal circuit is used to cool the engine, and a flow external circuit is used to cool fresh water and oil refrigerators.
Water circulation in a closed circuit is carried out using centrifugal pump 8 , supplying water to the discharge pipeline 10 , from which it is supplied through separate pipes to the bottom of the engine block to cool each cylinder. From the top of the block, water flows through the overflow pipes into the cylinder covers, and from them through the outlet pipeline it is sent to the water cooler 4 and then into the pump suction line 8 . The engine cooling system has a thermostat 3 with thermal cylinder 2 , which automatically maintains the required water temperature by bypassing part of it past the water cooler 4 . Initial filling with water internal contour produced through expansion tank 1 . The steam-air mixture from the engine exhaust pipe is also sent there.
Water is supplied to the external circuit by an autonomous centrifugal electric pump 7 , which takes water from the kingston through a paired mesh filter 9 With shut-off valves and supplies it sequentially to the oil 5 and water 4 refrigerators. The water from the water cooler is drained overboard. A thermostat is installed in front of the oil cooler 6 , which, depending on the oil temperature, regulates the amount of water passing through the refrigerator. The temperature and pressure of water in the cooling system is controlled by local and remote control devices and an alarm system.

Refrigerating machines on ships serve different purposes - air conditioning cabins, cooling holds, freezing when fishing. The functions assigned to the machine depend entirely on the purpose and type of vessel. For example, passenger ships need constant high-quality ventilation to make passengers feel comfortable. It is also necessary to provide holds for storing food supplies for the entire duration of the voyage. Refrigeration machines on fishing ships usually have a richer set of equipment. It is necessary for the rapid cooling of freshly caught fish, its freezing and long-term storage. It is very important to keep the product fresh until it is delivered to fish processing plants and warehouses.

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That is, within the framework of ongoing technological processes installations must solve the following problems:

Cool freshly caught fish to the required temperature. Generate ice suitable for cooling products. Provide quick freezing followed by storage. Create the required temperature range for salted and canned fish.

Made from more durable materials that resist corrosion, negative impact salt water and atmospheric phenomena. They are distinguished by more compact dimensions and low weight. They have an increased level of reliability, as they are operated in more harsh conditions- with constant vibration and pitching.