air cooled diesel engines

Working Of Air-Cooled Diesel Engine

The air-cooled cooling system uses air as the cooling medium. The high-speed moving air generated by the fan removes the heat of the high-temperature parts, permitting the air cooled diesel engines to operate at the optimum temperature.

Makers arrange heat sinks on the outer wall of the cylinder and the cylinder head to increase the heat dissipation area. We also arrange an air hood and a baffle to properly distribute the cooling air and improve the air utilization rate. The cooling effect is more effective and uniform.

Air-cooled diesel engine

The air-cooling system comprises 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, the lightweight of the whole machine, convenient use and maintenance, and good adaptability to regional environmental changes.

However, the air cooled diesel engines also has large noise and a high heat load. The fan consumes a large amount of power and has a low aeration coefficient.

Parts of cooled diesel engine

The diesel engine cooling system works using a centrifugal fan. The centrifugal fan of a cooled air diesel engine is often cast together with a flywheel, placed at the rear end of the diesel engine, and drives through the crankshaft.

Air is drawn axially from the air inlet and the airflow from the fan volute directly 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, and the flow resistance is small.

The axial fan drives through the crankshaft through the V-belt at the front end of the diesel engine. The air flows axially, sucked by the fan, and pressed into the air chamber composed of the air hood, and each cylinder cools, and then the air flows out through the splitter plate.

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 needs equipping to reduce the temperature. Common cooling systems are water-cooled and air-cooled.

An air-cooled diesel engines uses 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 limit by thermal 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 needs installation in an open cabin, which requires high environmental requirements and high noise. It needs treatment in the room for noise reduction. The air-cooling method is more applicable to small gasoline generators and low-power diesel generator sets.

In a water-cooled generator set, the water circulates inside and outside the body, taking away the heat generated inside the body through the heat-dissipating water tank and the fan. Both functions dissipate heat in the air, and there is not much difference in the use.

The advantage of the water-cooled is that the cooling effect is ideal, the cooling is rapid and stable, and the power conversion rate is high.

The installation site of the water-cooled system has small limitations, low environmental requirements, low noise, and a remote cooling system. Water cooling methods apply to small diesel generators and high-power diesel generator sets. The common diesel generator brands on the market are Cummins, Perkins, MTU (Mercedes-Benz), Volvo Shangchai, and Weichai.

Diesel generators in UAE make use of air circulation to cool the system. With air-cooled systems, the engine takes in cooler air from the atmosphere, blowing it internally across the generator set, keeping the generator from overheating.

Typically, air-cooled engines are for portable generators and standby generators with a capacity of up to 22 kilowatts.

With air-cooled systems, you have two options:

  • Open ventilated systems
  • Completely enclosed

Open ventilation systems use atmospheric air and release the exhaust is into the atmosphere. On the other hand, enclosed ventilation systems keep re-circulating the air to cool the internal generator parts.

Limitations of air-cooled diesel engine

Air-cooled engines have some limitations:

  • They can overheat if used for a long duration in excessive heat, so we recommend being aware of the ambient temperature and duration of use.
  • When air-cooled engines fail, there is the potential for needing significant repairs. The preventative maintenance and repair tasks require a more attentive approach compared with liquid-cooled systems.

Air-cooled engines are slightly less robust as oil breaks down quickly in hotter conditions, leading to damage occurring without any warning.

Liquid Cooled Generator Systems

Liquid-cooled systems use several types of oil/coolant to cool the internal generator parts. Liquid-cooled systems offer much better cooling than air-cooling systems, which is why liquid-cooled KOHLER® generators price higher than air-cooled units. Essentially, liquid-cooled engines are comparable to small car engines.

Liquid-cooling systems include a radiator and water pump. The pump distributes the liquid coolant to the engine block through hoses—the heat transfers to the coolant, which directs through the radiator where the air cools.

Generally, modern generators above 22 kW utilize liquid-cooling, with air-cooled engines dominating portable generators.

Liquid-cooling systems are more expensive to produce than air-cooled diesel engines; they require additional design consideration and parts, including a radiator.

They are more durable and powerful than air-cooled diesel engine counterparts. Since these generator sets are more expensive, in use for commercial and industrial purposes where the cooling demand is larger than small residential and portable units.

Which System Do You Need?

Every system comes with pros and cons. Air-cooled systems are simpler and less expensive than liquid-cooled systems. Liquid-cooled systems are more robust and effective. The cooling system you choose should be sufficient for your needs. Air-cooled systems are capable of the range of their utilization. Unless the ambient temperature is exceedingly hot, most residential generators will have no problem cooling via air.


The article is all about the mechanism of an air-cooled diesel engines. We have established a comparison between liquid-cooled diesel and air-cooled diesel engines to understand better the context, which will help you make the best choice.

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