Sea water system

Sea water pipeline provides:

intake of water by electric pumps for cooling and a desalination plant from a bulkhead, where sea water is supplied from the bottom or side sea chests through filters;

pumping fresh water refrigerators, and automatically draining water overboard or into circulation;

water supply to the desalination plant.

Main technical data

Sea water cooling system

To receive sea water into the cooling system, the MKO is provided with bottom and side sea chest boxes, from which water enters the sea water intake box through filters. The system is serviced by two RVD-450E cooling pumps, one of which is standby. The backup pump turns on automatically when the water pressure in the system drops. The pump receives sea water from the sea water receiving box and delivers it through the temperature controller to the fresh water coolers.

This regulator, depending on the temperature of the sea water at the outlet of the pumps, directs water from the refrigerators overboard through the non-return shut-off valve and to the inlet to the cooling pumps through the valve and the non-return shut-off valve into the sea chest or into the intake line of the cooling pumps.

One of the main cooling pumps is connected to the MO emergency drainage line through a valve.

The air pipes from the kingston boxes are combined and brought to the open part of the airspace and ends with a gooseneck.

To release air from the refrigerators, pipes are provided that are connected to the air pipe from the kingston boxes.

Figure 20. Schematic diagram of the SPP sea water cooling

fresh water system

The fresh water cooling system includes:

fresh water cooling system of the main engine;

fresh water cooling system for diesel generators.

The fresh water cooling system is designed for:

cooling of the main engine and diesel generators;

warming up the idle main engine with a fresh water heater;

supply of heating water to water desalination plants;

General description and main technical data

fresh water cooling systems for the main engine

The system is filled with water by an electric pump for pumping fresh water from the boiler water reserve tank through valves and into the expansion tank. Water is also supplied to the additive tank through the valve, and from it through the valve and tap into the expansion tank.

From the expansion tank through the valve, the system is filled with water, as well as replenishment of leaks during system operation.

The main engine cooling system is serviced by two fresh water cooling electric pumps, one of which is a standby one. The backup pump turns on automatically when the water pressure in the system drops.

Water enters the main engine through the pump water temperature controller, regulates the amount of water passing through the refrigerators, providing the necessary temperature regime engine cooling.

Fresh water from the main engine enters the deaeration tank, where air and steam-air mixture are separated. On the fresh water main, after the cooling pumps of the main engine, heating water is taken for desalination plants.

To heat the idle main engine, the system provides a fresh water heater, to which steam is supplied from the heating system.

Cooling system for diesel generators with fresh water.

The system is filled with water by an electric pump for pumping fresh water from the boiler water reserve tank through valves.

Water is supplied to the expansion tank of diesel generators from there, through the valve, the system is filled, as well as replenishment of leaks during system operation.

The fresh water system of each diesel generator is serviced by its own centrifugal pump attached to the engine.

Water is supplied to the jackets of diesel generators through fresh water coolers and valves.

To maintain a constant fresh water temperature, a thermostatic valve is installed at the outlet of the cooling water from the engines.

An electric heater is provided in the fresh water system of the engine to put an idle diesel generator into a "hot" reserve.

Figure 21. Principal diagram of SPP cooling with fresh water

In case of damage to the fresh water cooling system, diesel generators can be cooled by sea water by removing the blind flanges separating the fresh water and sea water systems.

The steam-air mixture is removed from diesel generators to the expansion tank of diesel generators.

The piping of the system is painted to match the color of the room. Fresh water pipelines are marked with two wide green rings.

Control and measuring devices.

Manometers, local and remote thermometers, low level alarms, pressure and temperature alarms are provided to control the operation of the system.

System compressed air

Compressed air system medium and low pressure provides:

Filling with compressed air from electric compressors cylinders of starting air of the main engine and diesel generator, low-pressure filling of cylinders of CO apparatus;

supply of compressed air from cylinders to the starting devices of engines at startup;

blowing the oil filters of the main engine;

ship needs, pneumatic tools and pneumatic tanks.

Compressed air system high pressure provides:

Filling from the electric compressor of cylinders from the starting cylinders of the emergency diesel generator and diesel motor pump of pneumatic supply cylinders of the system and lifeboat cylinders.

Air supply and exhaust systems

All cargo and slop tanks are equipped with a venting system, autonomous for each tank, designed to ensure gas exchange between the cargo tank and the atmosphere.

Each cargo and slop tank is equipped with a high speed gas bleeder and a vacuum valve with a flame arrester screen. The release of gas from the tanks through a high-speed gas outlet device is carried out at a speed of at least 30 m/s.

Figure 22. Schematic diagram of the SEU compressed air system

The cross-sectional area of ​​the pipes of the autonomous gas venting system ensures the removal of gases from one tank during cargo operations with a capacity of not more than 1100 m3/h.

Exhaust system for main and auxiliary engines

The gas exhaust system provides exhaust gases from the main engine through the utilization boiler, auxiliary diesel generators, emergency diesel generator and engine pump diesel through mufflers into the atmosphere. The recovery boiler and all mufflers are equipped with spark arresters.

Figure 23. Schematic diagram of the gas exhaust system of the power plant

The exhaust pipes are insulated and lined with a metal casing.

The gas exhaust system provides for permanent tar drainage and emergency discharge of water from the utilizing boiler.

The system includes:

Fresh water centrifugal pumps type KRZV-150/360 - two pieces, capacity - 30m 3 / h, pressure - 0.3 MPa;

Fresh water cooler type 524.15112/3253 with a cooling surface of 66.9 m 2 ;

Heater type 521.12089/625 with a heating surface of 11.89 m 2 ;

Pipelines, fittings, expansion tank;

Cooling water for the cylinders is supplied to the engine from the side opposite the clutch, through the main distribution manifold. Entering the cylinder block, the water rises, flowing around the cylinder bushings, and enters the cylinder covers, and from there into the prefabricated manifold located above the cylinder heads. Above it are the distribution and collection manifolds for cooling the exhaust valve cells. Water is supplied and discharged from each cell separately.

In order to prevent the phenomenon of corrosion in the cooling water cycle, an anti-corrosion agent is added to the cooling fresh water. Recommended "Arosta M" or ferroman 90 BF, 3 * K-0 or Rokor NB.

The amount of fresh water in the cycle is about 8.5 m 3 .

Sea water cooling system

The system includes:

Outboard water pump type KRZV150/360 - two pieces, capacity - 230 m 3 / h, at a pressure of 0.3 MPa;

Outboard water pumps type KRZIH200/315 - two pieces, capacity - 400 m 3 / h, at a pressure of 0.33 MPa;

Cooling Sea Water Pumps air compressors type WBJ32 / I-200 - two pieces, productivity - 5 m 3 / h;

Kingstons, pipelines, fittings, filters;

Connected to the system:

Coolers of fresh water GD;

DG oil coolers;

Fresh water coolers VDG;

Desalination plants;

Shafting bearing cooling;

Boiler plant condensate cooler;

Charge air coolers DG;

Air compressor coolers.

The cooling system is of a recuperative type, since there is a sea water tank and it is possible to regulate the temperature of the sea water.

Starting and control system

The launch of the main engine is carried out by three air cylinders for general consumption. Starting the main engine is also possible with a starting air cylinder.

One of the two air compressors operates as the main one, and the second one is in reserve. With the help of a working air compressor, all compressed air cylinders are filled. The air compressor is controlled automatically, depending on the air pressure in the cylinders, when the limit values ​​of the 2-position adjustment are reached. A further decrease in pressure below the limit value causes the connection of a backup air compressor. The protection circuit in the event of a lack of lubricating oil and cooling water pressure, as well as deviations from the normal values ​​​​of the intermediate pressure in the cylinders, causes the compressors to turn off. In the event of a power failure in empty air cylinders, it is possible to fill the air cylinder with a capacity of 40 liters with a manual compressor. This way you can start one of the VDGs.

Starting valves installed in the cylinder heads are opened pneumatically by the starting camshaft spools actuated by the camshaft starting cam and closed by spring force.

The control post is located on the side of the diesel engine, opposite the clutch. At the helm, using the flywheel, you can set the required fuel supply, along with the ability to set the supply on the speed controller.

Typical engine problems.

The main malfunctions are damage to the anti-friction alloy of the upper shells of the main bearings, coking of the turbine nozzle apparatus.

The analysis shows that when the engine is running, the frame necks make transverse oscillations, both in the vertical and horizontal planes. In this case, frame bearings perceive very significant loads, which lead to the destruction of the antifriction layer.

Operational measures that improve the hydrodynamic regime of lubrication of frame bearings are as follows: the values ​​of oil clearances when mounting frame and crank bearings should be set according to the minimum clearance values ​​recommended by the manufacturer's instructions. This will reduce the amplitude of transverse oscillations of the frame journals in the bearings and the dynamic loads on them. The lubricating oil pressure (LU) of the bearings should be maintained at the upper value recommended by the manufacturer's instructions.

During the operation of gas turbochargers (GTN) installed on engines 6 ChN 42/48, the following damage is observed: scuffing and scratches in the blades of the compressor impeller (KM), cracking in the impeller of the KM, coking of the turbine nozzle apparatus, deformation of the impeller blades and guides turbine nozzle blades.

The cause of these damages may be the contact of the blades of the turbine impeller and the guide vanes of the turbine nozzle apparatus, due to vibration of the rotor at the maximum wear of its bearings.

To prevent vibration of GTN parts, the rotor bearings should be replaced within the time recommended by the GTN manufacturer.

There are also failures of fuel equipment (TA): in high-pressure fuel pumps (high pressure fuel pump) - jamming of plunger pairs, loss of density of plunger pairs and loss of density of the discharge valve; at nozzles - hanging of the needle in the body, a decrease in the quality of the spray.

The main cause of TA failure is the corrosion of the surfaces of precision parts as a result of poor-quality fuel preparation. Operational experience has shown that where serious attention is paid to fuel preparation, cases of HE failures are very rare even when operating on heavy and sulphurous fuels.

Thus, we can conclude that for trouble-free operation of the engine, it is necessary to follow the rules technical operation(PTE) recommended by the manufacturer.

Ship power plant.

To provide electric power to electric consumers, the ship is equipped with two AC diesel generators, two AC shaft generators, and one emergency diesel generator.

AC shaft generator characteristic:

Type DGFSO 1421-6

Power, kW 1875

Voltage, V 390

Speed, min -1 986

Kind of current variable

Efficiency at rated load, % 96

The alternator type DGFSO 1421-6 is driven by the main engine. The generator rotor is driven through a gearbox by means of a disconnected flexible coupling. The generator is made on legs with two plain bearings mounted in shields. Bearings are lubricated from gearboxes. The slip rings and the initial excitation generator are located on the opposite side of the drive.

The generator is equipped with four electric heating elements with a total power of 600 W.

For remote temperature measurement, six thermal resistances are placed in the generator slots. Three thermal resistances are working, the rest are spare. One similar thermal resistance is installed in the flow of incoming and outgoing air. All thermal resistances are connected to the ratiometer through a switch. For remote signaling of extreme temperatures, the generator is equipped with two thermostats installed in the outlet air stream. One of the thermostats is reserved. The thermostats are set to operate at 70°C.

Bearing temperature limits are signaled using contact thermometers with a direct temperature indicator and a remote signaling contact that operates at a temperature of 80 ° C. Two special thermostats are provided for signaling the limit temperature of the windings.

Characteristics of diesel generator:

Number 2

Rated power, kW 950

Voltage, V 390

Rotational speed, s -1 (min -1) 16.6 (1000)

Kind of current variable

The drive motor of the S 450 LG alternator is an auxiliary motor. The generator rotor is driven through a gearbox by means of a disconnected flexible coupling. The generator is made on legs with two plain bearings mounted in shields. Bearings are lubricated from gearboxes. The slip rings and the initial excitation generator are located on the opposite side of the drive.

The generator is made with self-ventilation. Cooling air is taken from the engine room through special filters. The air outlet from the generator is carried out to the ship's ventilation system through a branch pipe.

The generator is designed for continuous operation with unbalanced load up to 25% between any phases. The voltage unbalance does not exceed 10% of the nominal value. The generator, operating in a steady thermal rated mode, allows the following overcurrents: 10% for one hour at a power factor of 0.8; 25% for 10 minutes at a power factor of 0.7; 50% for 5 minutes at a power factor of 0.6.

The self-excitation system and AVR of the 2A201 type generator are made according to the principle of current compounding using a semiconductor voltage regulator. For reliable self-excitation, an initial excitation generator is introduced into the circuit.

Elements of the self-excitation system and AVR are located on the generator in a special removable cabinet. The AVR system ensures that the voltage at the generator terminals is constant with an error not exceeding ±2.5% at a power factor of 0.6 to 1. When a load is applied to the generator by 100% or a load is dumped corresponding to 50% of the rated current, with a power factor equal to 0.4%, instantaneous voltage change does not exceed 20% of the nominal value and is restored with an error of no more than ±2.5% in 1.5 s.

Protection of diesel generators from short circuit currents is carried out by maximum releases of selective automatic devices (the rated current of the automatic device is 750 A, the maximum release is 375 A, the response time is 0.38 s, the response current is 750 A). The AC shaft generator is protected by an automatic switch (the rated current of the machine is 1500 A, the rated current of the maximum release is 125 A, the operation time is 0.38 s, the operation current is 2500 A). Generators are undermined by the undermining relay.

Protection of diesel generators against overloads is carried out in two stages. At 95% load of the generator, the overload relay of the first stage is activated, respectively, with a time delay of 1 s and turns on the light and sound alarms. If the load on the diesel generator continues to increase and reaches 105%, another overload relay of the second stage is activated with a time delay of 2.5 s, an additional light alarm is turned on and power is simultaneously supplied to turn off the following consumers: heaters, cargo devices, refrigeration unit, ventilation, RMU, fish shop, galley equipment and some other irresponsible consumers. When the load reaches 110%, the generators are disconnected from the network.

Shaft generator protection is made in three stages.

Protection of feeders against short circuit current is provided circuit breakers AZ-100 and AK-50 series.

The ship is equipped with a three-phase electric power plant with a voltage of 380 V, a frequency of 50 Hz. To supply consumers with parameters that differ from the parameters of the ship's power plant, appropriate converters and transformers are provided.

For drives of electrified mechanisms, asynchronous squirrel-cage electric motors of three-phase alternating current with starting from magnetic stations or magnetic starters are installed.

All electrical equipment installed on open decks and fish processing shops is waterproof. Electrical equipment installed in special enclosures and cabinets has a protected design. Electric motors of the AOM series are used to drive the mechanisms of the fish shop.

The following types of lighting are provided on the ship: main lighting, searchlights and raft lights - 220 V; emergency lighting (from rechargeable batteries) - 24 V; portable lighting - 12 V; signal and distinguishing lights - 24V.

For 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 cylinder liners and covers and, in some engines, from the piston heads, to cool the circulating oil to cool the air during diesel supercharging. The nozzle cooling system is autonomous.

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

Fresh water systems themselves are divided into three main cooling subsystems:

Cylinders, covers and turbochargers;

Pistons (if they are water-cooled);

Nozzles (if they are cooled with water);

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

On the move of the vessel, cooling is carried out by the main pump, and in the parking lot - 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, and each diesel generator is equipped with an autonomous pump and a cooler common to all diesel engines;

Each diesel engine is equipped with an independent cooling system.

The most rational option 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 one in the standby one (the layout of the sea water pump is used), one parking (port) pump, one or two coolers, temperature controllers (regulation by fresh water bypass through the refrigerator), expansion tanks (compensation changes in the volume of fresh water in a closed system with 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 cooling system. Fresh water is supplied by the circulation pump II to the water cooler 8, after which it enters the cavities of the working bushings 19 and the cover 20. The heated water from the engine is supplied through the pipeline 14 to the pump II and again to the cooler 8. The highest located section of the pipeline 14 is connected by a pipe 7 with expansion tank 5, which communicates with the atmosphere. Expansion tank ensures filling with water circulation system engine cooling. At the same time, air is vented from this system through the expansion tank.

To reduce the corrosiveness of fresh water, a solution of chrompeak (potassium bichromate K2Cr2O7 and soda) is added to it in an amount of 2-5 g per liter of water. The solution is prepared in the solution barrel 6, and then lowered into the expansion tank 5. To control the temperature of the 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 with the main pump II.

Outboard water for cooling is taken through the onboard or bottom kingston 1. From the kingston, water through filters 18 that trap particles of silt, sand and dirt, enters the outboard 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 to the bypass pipeline 13, water can be passed past the oil cooler. The heated water after the water cooler 8 is discharged overboard through the outflow outboard valve 4. broken ice in the receiving kingstones, part of the heated water through pipeline 2 can be passed into the suction line. The flow of heated water is controlled 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.

Particularly active in terms of corrosion is sea water containing chloride, sulfate and nitrate salts. The corrosive activity of sea water is 20-50 times higher than that of fresh water. On ships, seawater cooling system piping is sometimes made from non-ferrous metals. To reduce the corrosive effect of sea water, the inner surface steel pipes cover

Rice. I Cooling system diagram

zinc, bakelite and other coatings. The temperature in seawater systems should not be allowed to exceed 50-550C, as salt precipitation occurs at higher temperatures. Sea water system pressure, created by pumps, is in the range of 0.15-0.2 MPa, and in the fresh water system 0.2-0.3 MPa.

The seawater temperature at the inlet to the system depends on the temperature of the water in the basin where the vessel is sailing. The calculated temperature is 28-30°C. The temperature of fresh water at the inlet from the engine is taken within 65-90 ° C, and lower limit refers to low-speed engines, and the upper one - to high-speed ones. The temperature difference between the temperature at the outlet and inlet to the engine is taken Δt=8-100C.

To create a static head, 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 standby. The same requirement applies to the nozzle 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 household needs. Evaporation plants must be carried out as a single unit, have automation and must be operated without a special watch.

The outboard cooling water system, including the 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 of engine and boiler rooms (compressors, steam condensers, evaporators, refrigeration units), propeller shaft bearings, deadwood, etc. This system can be implemented according to the scheme with a serial and parallel arrangement of heat exchangers.

The requirements of the USSR Register Rules for the outboard cooling water system with regard to the redundancy of the units are similar to the requirements for the fresh water system.

Questions for self-examination

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 can the cooling system of cylinders, covers and turbochargers have?

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

5. Same for the sea cooling water system?

6. What are the functions of the expansion tank?

7. How is the temperature of fresh water regulated?

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

9. What are the fresh and sea water parameters 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 outboard water systems.

12. Why is a two-circuit scheme used for engine cooling?

But she is not the only one. The marine diesel internal combustion engine needs to be moderately warmed up. First of all, effective work the engine is provided with temperature gaps of its parts, calculated for the hot state. Secondly, heated lubricating oil becomes more fluid and performs better. Of course, we are talking only about the operating temperature range of a marine diesel engine, which must be maintained by the correct operation of the cooling system. Overheating of the engine can lead to serious consequences in yachting. There is nothing surprising in the fact that yacht motors are cooled by outboard water.

Marine engine cooling system.

In rare cases, this water is fed directly into the cylinder block, after which it is dumped overboard. Such a cooling system is called single-circuit, its simplicity has its positive and negative sides.

Almost all modern marine diesel engines on sailing and motor yachts are equipped with a dual-circuit cooling system.

Through the valve (1), sea water enters the filter (2). Outboard water is pumped by a pump (3), which supplies this water to the heat exchanger (5), after which it is discharged into the exhaust pipe of the marine diesel engine (7). The internal circuit pump (4) pumps through the heat exchanger the antifreeze circulating inside the cylinder block in order to directly cool them. If the engine exhaust manifold is located below the waterline, a siphon valve (6) is installed on the seawater discharge pipe to prevent seawater from entering it through the exhaust pipe of a stopped engine.

This is a schematic diagram of a marine diesel engine cooling system. In practice, it is supplemented by the necessary elements, which may include:

Temperature sensor of the internal cooling circuit, which provides readings of the pointer device and includes sound and light alarms in case of overheating;

A thermostat that switches on the circulation of sea water in the heat exchanger only after the temperature of the internal circuit reaches the operating parameters;

In some cases, it is a signaling device for exceeding the temperature of the exhaust gases, which should first of all warn of a malfunction in the seawater supply system for cooling the marine diesel engine.

Despite the relative complexity of the design, this system has significant advantages: it is not sea water that circulates in the marine diesel engine, which is aggressive with respect to structural materials, but a special coolant - a mixture of fresh water and refrigerant, which does not cause metal corrosion and clogging with precipitation and scale of very thin channels of the cooling system. In addition, the coolant does not freeze at sub-zero temperatures, which also increases the service life and reliability of the marine engine.

Marine engine air intake and exhaust systems.

If the opening of the entrance to the engine compartment is accompanied by an increase in the speed of the ship's engine (and this happens!) - it does not have enough air. The free flow of air from the passenger compartment to the motor even contributes to accelerated ventilation of the premises, because. a running marine engine in this case plays the role of a powerful exhaust.

Sterility sea ​​air not only good for health, but also allows not to complicate the air intake and cleaning systems at the inlet to the diesel engine. The air filter (1) is usually made of foam rubber, which is simply washed and dried periodically.

Through the intake manifold (2), air enters the intake valves of the cylinders (3), ensuring the combustion of fuel.
Exhaust gases through the exhaust valves (4) and the exhaust manifold, mixed with the water of the external cooling circuit, through the exhaust pipe (5) are discharged into the water lock / muffler (6) and through the gooseneck (7) are discharged overboard.

Marine diesel engine electrical system.

On all yachts, the marine diesel engine is started by electric power from a battery (1) designed exclusively for this purpose, without allowing it to be discharged by any other consumers. When the marine engine is not running, the circuit breaker (2) cuts off accidental leakage currents. The starter motor relay is energized by turning the key in the ignition switch (4) and drives the starter (3). A working marine engine rotates a generator (5) attached to it, which charges the starter battery and household batteries through the outlet (6) to the electrical system of the yacht itself.

To improve reliability in the on-board system direct current it is possible to connect batteries of household consumers to the engine start mode, in case a trouble occurs with the starter battery. All modern motors are equipped with instruments for monitoring operating parameters: speed, temperature, pressure. Sometimes the marine diesel engine is also controlled electronically.

This concludes the review of marine diesel engine systems. And in the next article we will talk about another integral element of a modern yacht.

The cooling system provides heat removal from various mechanisms, devices, devices and working media in heat exchangers. Water-cooled systems are common in marine power plants due to a number of advantages. These include high efficiency (the thermal conductivity of water is 20-25 times higher than that of air), less influence of the external environment, more reliable start-up, and the possibility of using the heat removed.

In diesel installations the cooling system is used to cool the working cylinders of the main and auxiliary engines, the gas exhaust manifold, charge air, oil of the circulating lubrication system and the air coolers of the starting air compressors.

Cooling system in steam turbine plants designed to remove heat from condensers, oil coolers and other heat exchangers.

Cooling system for gas turbine plants used for intercooling of air at multistage compression, cooling of oil coolers, parts of gas turbines.

In addition, in installations of any type, the system is used to cool the thrust and thrust bearings of the shafting, to pump stern tubes, and is used as a reserve for the fire-fighting system. Marine cooling systems use outboard and fresh water, oil and air as the working fluid. The choice of coolant depends on the temperatures of the heat sink, design features and sizes of cooling units and apparatuses. Most wide application as a coolant finds fresh and outboard water. Oil is rarely used in cooling systems, for example, for cooling pistons of internal combustion engines. This is due to its significant disadvantages compared to water (high cost, low heat capacity). At the same time, oil as a coolant has valuable properties, a high boiling point at atmospheric pressure, low pour point, low corrosivity.

Air is used as a cooling medium in gas turbines. To cool GTU parts, air of the required pressure is taken from the pressure pipelines of the compressors.

Cooling systems are divided into flow and circulation. In flow systems, the cooling working fluid is discarded at the outlet of the system.

In circulating cooling systems, a constant amount of coolant repeatedly passes through a closed loop, and the heat from it is removed to the cooling working fluid of the flow system. In this case, two flows take part in the cooling, and the systems are called double-circuit.

Centrifugal pumps are used as circulation pumps for fresh and sea water.

Cooling systems for diesel power plants almost always double-circuit: the engines are cooled by closed-circuit fresh water, which, in turn, is cooled by sea water in a special refrigerator. If the engine is cooled by a flow system, cold outboard water will be supplied to it, the heating temperature of which should not be higher than 50 - 55 ° C. At these temperatures, salts dissolved in it can be released from the water. As a result of salt deposits, the transfer of heat from the engine to water is difficult. In addition, the cooling of engine parts cold water leads to increased thermal stresses and a decrease in diesel efficiency. Closed-loop cooling systems used in diesel engines make it possible to have clean cooling cavities and easily maintain the most favorable water cooling temperature, adjusting it in accordance with the engine operating mode.

Each engine room, in accordance with the requirements of the Maritime Register of Shipping, must have at least two sea chests, which ensure the intake of outboard water in any operating conditions.

Sea water intakes are recommended to be placed in the bow of the engine rooms, as far as possible from propellers. This is done to reduce the likelihood of air entering the seawater intake pipes when the propeller is in reverse gear.

The design seawater temperature for ships with an unrestricted navigation area is 32°C, and for icebreakers 10°C. The largest number heat is removed by outboard water in the cooling system of the STP, which is 55 - 65% of all fuel released during combustion. In these plants, heat is mainly removed by steam condensation in the main condensers.

Diesel cooling mode is determined by the temperature difference of fresh water at the inlet to the engine and at the outlet of it. In the main slow-speed engines, the temperature at the inlet to the engine is at the level of 55°C, and at the outlet 60 - 70°C. In the main medium-speed and auxiliary diesel engines, this temperature is 80 - 90°C. Below these values, the temperature is not lowered for reasons of increasing thermal stresses and reducing the efficiency of the working process, and an increase in cooling temperatures, despite the improvement in diesel performance, significantly complicates the engine itself, the cooling system and operation.

The water pressure of the internal cooling circuit of diesel engines must be slightly higher than the sea water pressure in order to prevent the sea water from entering the fresh water in the event of a leak in the cooler pipes.

On fig. 25 is a schematic diagram of the double-loop cooling system of the DEU. The bushings of the working cylinders 21 and covers 20 are cooled with fresh water, which is supplied by the circulation pump 11 through the water cooler 8. The water heated in the engine is supplied through the pipeline 14 to the pump 77.

From the highest point of this circuit, a pipe 7 departs to an expansion tank 5 connected to the atmosphere. The expansion tank serves to replenish the circulation cooling system with water and to remove air from it. In addition, if necessary, a reagent can be supplied from tank 6 to the expansion tank, which reduces the corrosive properties of water. The temperature of fresh water supplied to the engine is controlled automatically by thermostat 9, which bypasses more or less water in addition to the refrigerator. The temperature of fresh water leaving the engine is maintained by a thermostat at the level of 60...70°C for low-speed diesel engines and 8O...9O°C for medium- and high-speed ones. Parallel to the main fresh water circulation pump 11, a standby pump 10 of the same type is connected.

Outboard water is received by the centrifugal pump 17 through the onboard or bottom kingstones 7, through the filters 19, which partially clean the water coolers from silt, sand and dirt. In parallel with the main sea water pump 77, the system has a standby pump 18. After the pump, sea water is supplied to pump oil cooler 12, fresh water cooler 8.

In addition, part of the water through the pipeline 16 is sent to cool the charge air of the engine, air compressors, shafting bearings and other needs. If it is planned to cool the pistons of the main diesel engine with fresh water or oil, then, in addition to the above, the sea water also cools the heat-removing medium of the pistons.

Rice. 25.

The outboard water line at the oil cooler 12 has a bypass (bypass) pipeline 13 with a thermostat 75 to maintain a certain temperature of the lubricating oil by bypassing the outboard water in addition to the cooler.

The heated water after the water cooler 8 is discharged overboard through the drain valve 4. In cases where the temperature of the sea water is too low and ice sludge enters the kingstones, the system provides for an increase in the temperature of the sea water in the intake pipeline due to the recirculation of heated water through pipe 2. The amount of water returned to the system is regulated valve 3.