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How Does The Air-Cooled System Work in Diesel Generator Set

Nov. 20, 2018


What are the layouts of the genset air-cooled cooling system?


The genset air-cooled cooling system uses air as the cooling medium. The high-speed moving air generated by the fan directly removes the heat of the high-temperature parts, allowing the diesel engine to operate at the optimum temperature. Heat sinks are arranged on the outer wall of the cylinder and the cylinder head to increase the heat dissipation area, and an air hood and a baffle are arranged to properly distribute the cooling air and improve the air utilization rate, so that the cooling effect is more effective and uniform. The air cooling system is mainly composed of a heat sink, a fan, an air hood and a deflector. Compared with the water cooling system, the air cooling system has the advantages of few parts, simple structure, light weight of the whole machine, convenient use and maintenance, and good adaptability to regional environmental changes. However, the air cooling system also has large noise and high heat load. The fan consumes a large amount of power and has a low aeration coefficient.

The Difference Between Air-cooled and Water-cooled Generator Set.jpg


According to the arrangement of diesel cylinders, fan type and installation position, the air cooling system is often arranged in the following types:


The diesel engine cooling system using a centrifugal fan is shown in Figure 1. The centrifugal fan of a single-cylinder diesel engine is often cast together with a flywheel, placed at the rear end of the diesel engine, and directly driven by the crankshaft. Air is drawn axially from the air inlet, and the airflow from the fan volute is directed by the air hood to the cylinder and cylinder head for cooling. The arrangement is simple and compact, and there is no special fan driving mechanism, the cooling airflow has less turning, the flow resistance is small, and the small air-cooled diesel engine is mostly used.


  Figure 1.jpg

Figure 1. Air cooling with centrifugal fan

Schematic diagram of single cylinder cooling system


1. Air inlet

2. Centrifugal fan

3. Flywheel

4. Air hood

5. Cylinder

6. Cylinder head

7. Fan volute



The cooling system of an in-line multi-cylinder diesel engine using an axial fan is shown in Figure 2. The axial fan is driven by the crankshaft through the V-belt and the fan is placed at the front end of the diesel engine. The air flows axially, is sucked by the fan and pressed into the air chamber composed of the air hood, and each cylinder is cooled and then flows out though the splitter plate. The spitter plate is arranged to reasonably organize the flow of air to achieve the


Figure 2.jpg

Figure 2. Inline four-cylinder air cooling with axial fan

Engine cooling system schematic

1. Axial fan

2. Air hood

3. Heat sink

4. Cylinder shroud

5. Diverter

6.V belt


The cooling system of a V-type diesel engine using an axial fan is shown in Figure 3. the axial flow fan is arranged in the middle of the two rows of cylinder angles at the front end of the engine and is driven by the crankshaft through the V belt. The cooled air is discharged from the lower side of the two rows of cylinders, respectively.



Figure 3.jpg


Figure 3. V-type with axial fan

Air-cooled engine cooling system


1.V belt

2. Windshield

3. Axial fan

4. Air hood



The difference between air-cooled generator set and water-cooled generator set


Diesel generator sets generate a lot of heat during normal operation. Excessive heat will cause the unit temperature to rise, which will affect the working efficiency. Therefore, the cooling system should be equipped in the unit to reduce the temperature of the unit. Common genset cooling systems are water-cooled and air-cooled.


Air-cooled generator set: use one or more large fans to force the exhaust air to dissipate heat from the generator body. Its advantages are simple structure, good maintenance, no freezing cracks or hot boiling danger. The generator set is limited by thermal load and mechanical load, the power is generally small, and the power conversion rate of the generator set is relatively low, which is not energy-saving. The air-cooled machine must be installed in an open cabin, which requires high environmental requirements and high noise. It needs to be treated in the room for noise reduction. The air cooling method is more applied to small gasoline generators and low power diesel generator sets.


Water-cooled generator set: The water circulation inside and outside the body, taking away the heat generated inside the body through the heat-dissipating water tank and the fan. Both functions are to dissipate heat in the air, and there is not much difference in the use. The advantage of the water-cooled unit is that the cooling effect is ideal, the cooling is rapid and stable, and the power conversion rate of the unit itself is high. The installation site of the water-cooled unit has small limitations, low environmental requirements, low noise, and a remote cooling system. Water cooling methods are generally applied to small diesel generators and high power diesel generator sets. The common diesel generator brands on the market, Cummins, Perkins, MTU (Mercedes-Benz), Volvo Shangchai, and Weichai are generally water-cooled generator sets.


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