What is an internal combustion engine?
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some components of the engine.
Such engines derive their energy from the heat released during the combustion of the unreacted working fluid, a mixture of oxidant and fuel. This process takes place inside the engine and is part of the thermodynamic cycle of the device.
The useful work produced by an internal combustion (IC) engine comes from the hot gaseous products of combustion acting on the engine’s moving surfaces such as pistons, turbine blades, or nozzles.
The internal combustion engine is the most widely applied and widely used power generation device at present. For example, we can mention gasoline engines, diesel engines, gas turbine engines, and rocket propulsion systems.
Internal combustion engines are divided into two groups, continuous combustion engines, and intermittent combustion engines. Continuous combustion engines are characterized by a constant flow of fuel and oxidants to the engine.
Maintains a stable flame in an engine (such as a jet engine). Intermittent combustion engines are characterized by the periodic combustion of air and fuel and are commonly known as reciprocating engines. Separate volumes of air and fuel are processed cyclically. Gasoline piston engines and diesel engines are examples of this second group.
The most common internal combustion engines are four-stroke engines, gasoline engines, homogeneous charge, and spark ignition engines. This is due to its excellent performance as a driving force in the ground transportation industry.
Read More: What is an External Combustion Engine?
How does an internal combustion engine work?
When the fuel is ignited, it combusts and creates hot, expanding gases. These gases push against the piston, causing it to move. The movement of the piston is transmitted through the crankshaft and powertrain to the wheels of the vehicle, which drives the vehicle forward.
There are two main types of internal combustion engines: spark-ignition gasoline engines and compression-ignition diesel engines. Spark ignition engines use a spark plug to ignite the fuel-air mixture inside the cylinder.
The fuel is mixed with air and inducted into the cylinder during the intake process. The piston then compresses the fuel-air mixture, and the spark plug ignites it, causing the fuel to combust. The expanding gases from the combustion push against the piston, creating the power stroke.
Diesel engines, on the other hand, do not use a spark plug to ignite the fuel. Instead, they induct only air into the cylinder and compress it. Then, they inject a fine mist of fuel into the hot, compressed air. The heat of the compressed air causes the fuel to ignite, and the expanding gases from the combustion push against the piston, creating the power stroke.
Both types of internal combustion engines operate on a four-stroke cycle, which includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.
The four-stroke operation cycle is as follows.
- Intake strokes. The intake stroke opens the intake valve and the piston moves to the bottom of the cylinder and sucks in air. For spark-ignition engines, fuel is usually mixed with air.
- The compression strokes. The compression stroke closes both valves and the piston moves to the top of the cylinder. Ignition occurs when the piston approaches top dead center (TDC). For compression ignition engines, fuel is injected toward the end of the compression stroke.
- The combustion and power stroke. Combustion spreads through the charge, increasing pressure and temperature and pushing the piston down. At the end of the power stroke, the exhaust valves are opened and the irreversible expansion of the exhaust gases is called “blowdown”.
- On the exhaust stroke, the exhaust valve remains open and the remaining gas is expelled by the movement of the piston to the top of the cylinder. When the exhaust valve closes at the end of the exhaust stroke, exhaust gases remain. These will dilute the next charge.
A four-stroke cycle is sometimes summarized as ‘suck, squeeze, bang, and blow’ This cycle is only completed once every two revolutions, so the valve gear (and fuel injectors) must be driven by a mechanism that operates at half an engine revolution. Part of the force from the expansion stroke is stored in the flywheel to power the other three strokes.
Applications of internal combustion engines
Internal combustion engines are the most broadly applied and widely used power-generating devices currently in existence. Examples include gasoline engines, diesel engines, gas-turbine engines, and rocket-propulsion systems.
Internal combustion engines are used in a wide variety of applications, including:
- Transportation. Internal combustion engines are used to power automobiles, buses, trucks, motorcycles, boats, and airplanes.
- Electricity generation. Internal combustion engines can be used to generate electricity in power plants.
- Agriculture. Internal combustion engines are used to power tractors and other farm machinery.
- Construction. Internal combustion engines are used to power construction equipment such as bulldozers, excavators, and cranes.
- Military. Internal combustion engines are used to power tanks, military vehicles, and ships.
- Industrial. Internal combustion engines are used to power pumps, generators, and other industrial machinery.
- Recreational. Internal combustion engines are used to power a variety of recreational vehicles such as snowmobiles, jet skis, and all-terrain vehicles.
Advantages of internal combustion engines
There are several advantages of internal combustion engines:
- They are relatively simple and inexpensive to manufacture, especially when compared to electric motors.
- They can run on a wide range of fuels, including gasoline, diesel, and ethanol, which makes them very flexible.
- They are able to produce a high power-to-weight ratio, which makes them well-suited for use in vehicles and other applications where weight is a concern.
- They have a high energy density, which means that they can store a lot of energy in a small space.
- They are able to work in a variety of environments, including cold temperatures and high altitudes, where electric motors may not be as effective.
- They are relatively easy to maintain, with many parts being readily available and relatively inexpensive to replace.
Disadvantages of internal combustion engines
Internal combustion engines (ICEs) have several disadvantages, including:
- Pollution. ICEs emit harmful pollutants such as carbon dioxide, nitrogen oxides, and particulate matter, which contribute to air pollution and have negative impacts on human health and the environment.
- Limited fuel options. ICEs are primarily powered by fossil fuels, such as gasoline and diesel, which are non-renewable resources that contribute to climate change when burned.
- Noise. ICEs can be loud and produce significant amounts of noise, which can be a nuisance in residential areas and cause hearing damage to people who are exposed to the noise for prolonged periods of time.
- Maintenance. ICEs require regular maintenance, including oil changes, spark plug replacements, and other services, which can be costly and time-consuming.
- Inefficiency. ICEs are not very energy efficient, as they convert only a small percentage of the energy in fuel into useful work. This means that a large portion of the energy is wasted as heat and emissions.
- Limited lifespan. ICEs have a limited lifespan and will eventually wear out and need to be replaced, which can be costly.