Air-cooled engines reduce heat produced using air-flow. To facilitate this, the engines have fins that connect the internal parts which get heated, to the outside, so that air can flow over them keeping the insides cool.
The air used for this purpose is either directly got from the air in-flow while traveling, or a fan is used. Usually, engines which have forced air (using a fan) perform better due to the force. In cars, however this became mandatory due to unavailability of direct flow.
Types
Copper-cooled: Copper fins were used instead of steel or aluminum by Charles F Kettering of Delco Electronics in 1923. But since the engine overheated in high temperatures. The model never got incorporated into engines.
Steel or aluminum cooled: Engines having Steel and aluminum fins are the most common ones. There are engines that use a combination of both. For example, the aviation engine continental C85 has steel fins on the cylinder barrel and aluminum on the head cylinder.
Advantages
- Air-cooled engines require no separate cooling apparatus and thus they add little weight to the vehicle.
- Since they don’t involve fluids, maintaining them is easy.
Disadvantages
- Since air is not a good conductor of heat as water, the cooling is much slower as compared to that of a water cooled engine.
- They are expensive to construct. This is because, the fins are a complex network of metal plates, which has to be precisely arranged in a particular design, to receive the maximum airflow in an appropriate speed for maximum performance. It is expensive also because, the casting of the fins has to be such that they pass through the walls of the engine. This construction involves more work and thus becomes expensive.
- By including fins, they increase the area occupied by the engine. The decreasing the area of the fins, the cooling gets affected. So, the fins necessarily have to be large enough.
- In certain conditions, they tend to overheat.
Usage
Used mostly in air crafts and motorcycles, because in air crafts, it doesn’t add up much weight, whereas in motorcycles, the engine can be kept exposed to receive air-flow. Usage in cars was limited due to the need to use fans which again requires power. Some diesel engines that were produced by Deutz AG and Lister-Petter were air-cooled. Tatra produces a big Euro-5 truck air cooled engine.
Additional Resources:
centrifugal fans and blowers