Heat engines are found everywhere you go. There is a heat engine present in a refrigerator that helps to cool your food items. You can also find heat engines in your car. They are also present in all kinds of air-conditioning units. The primary importance of a heat engine is to produce mechanical energy with the help of heat energy. There are two primary classifications of heat engines based on the combustion process. The two types of heat engines are internal combustion engines and external combustion engines. Before we look into the classification of heat engines, let us understand what exactly a heat engine is.
What is a Heat Engine?
We know that a heat engine is used to produce mechanical energy by using heat energy as a source. To be precise, it uses fuel such as petrol or diesel and converts its chemical energy into thermal energy by burning it. This thermal energy is then used to move mechanical parts, thus producing mechanical energy. By definition, it is considered a thermodynamic system.
Let’s consider a heat engine system, as depicted in the image. For a heat engine to work, we need three essential components. Those components are the engine that produces work, a source that provides heat energy at a higher temperature reading, and a sink used to cool down the engine to protect the engine from overheating. Now that you know how a heat engine works, we will look at the different types of heat engines.
1. Internal Combustion Engine
As the name suggests, the burning of fuel, commonly known as combustion, occurs inside the system. It is commonly known as IC engines. An IC engine is a type of heat engine that uses working fuel such as petrol and diesel as a heat energy source. The working principle is that it produces work by burning fuel and creating a high-pressure environment. This high pressure is then used to run a turbine or a piston, which converts the heat energy to mechanical energy.
The internal combustion engine is classified into three major types, and they are as follows.
The Advantages of IC Engines
The Disadvantage of IC Engines
2. External Combustion Engine
As the name suggests, the burning of fuel, or commonly known as combustion, takes place outside the system. It is commonly known as EC engines. In this engine, heat from the burnt fuel is transferred to a secondary liquid, which acts as fuel for the engine.
Examples: In the steam engine, the heat of combustion is employed to generate steam, which is used in a reciprocating engine to produce useful work.
In a closed cycle gas turbine, the heat of combustion in an external furnace is transferred to gas, usually air, which is the working fluid of the cycle.
The Advantage of EC Engines
The Disadvantage of EC Engines
Fun Facts
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Did you know that there is a toy that tends to utilise a heat engine? It is called “the drinking bird” and it works according to a thermodynamic cycle, just like all the other types of heat engines.