What is An Engine? – Different Types of Engines

An engine is a machine that burns fuel and converts it into mechanical power. Most modern vehicles use internal combustion engines (ICE), which ignite fuel and use the reaction to move mechanical parts.

ICE engines burn gasoline or diesel fuel to drive pistons up and down, turning the crankshaft and eventually moving the vehicle’s wheels. Technicians measure engines by the number of cylinders and the volume of those cylinders.

For instance, a 350 V8 is an engine with eight cylinders arranged in a V formation, displacing 350 cubic inches.

It’s not uncommon to hear someone refer to the engine in their electric car, but EVs do not have engines; they have motors. Motors are machines that convert electrical energy into motion.

What is An Engine?

An engine is a machine that burns fuel and converts it into mechanical power. Most modern vehicles use internal combustion engines (ICE) that ignite the fuel and use the reaction to move mechanical parts.

Engines – such as those used to power vehicles – can run on a variety of different fuels, particularly gasoline, and diesel in cars.

However, there are some alternative fuel types such as biofuels and natural gas. In thermodynamic terms, engines are commonly referred to as heat engines that produce macroscopic motion from heat.

The heat in this case comes from the combustion of fuel in the engine, which moves pistons.

Mechanical heat engines convert heat into work via various thermodynamic processes.

The internal combustion engine is perhaps the most common example of a mechanical heat engine, in which the heat from the combustion of fuel causes rapid pressurization of the gaseous products of combustion in the combustion chamber, causing them to expand and drive a piston that rotates a crankshaft.

Unlike internal combustion engines, a reaction engine generates thrust by expelling reaction mass according to Newton’s third law of motion.

Apart from heat engines, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy.

In biological systems, molecular motors, like myosins in muscles, use chemical energy to generate forces and ultimately motion (a chemical engine, but not a heat motor).

Chemical heat engines that use air as part of the fuel reaction are considered air-breathing engines, e.g., Rocket, deeply submerged submarines

How do Engines work?

In an internal combustion engine (ICE), the ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion to work.

The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels.

There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine.

Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

Spark-ignition gasoline and compression-ignition diesel engines differ in how they supply and ignite the fuel. 

In a spark ignition engine, the fuel is mixed with air and then inducted into the cylinder during the intake process. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion.

The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, only air is inducted into the engine and then compressed. Diesel engines then spray the fuel into the hot compressed air at a suitable, measured rate, causing it to ignite.

Combustion Cycle

There are thousands of controlled explosions occurring every minute the engine is running. Most internal combustion engines have a four-stroke combustion cycle:

• Intake: The air-fuel mixture gets drawn in through intake valves and sent to the cylinders.
• Compression: Both intake and exhaust valves are closed during the compression stroke. As pistons move up, the air and fuel mixture gets compressed toward the spark plugs.
• Combustion: The spark plugs ignite the air-fuel mixture with a spark, creating a small explosion. This causes the pistons to get pushed down forcefully.
• Exhaust: The final process in the cycle is the exhaust stroke. The exhaust valve opens, and gases created during combustion are expelled as the piston moves back up.

Diesel engines are also often four-stroke engines, but they’re different from gasoline-powered engines in how they complete the combustion process. Instead of using spark plugs to ignite the air-fuel mixture, they rely on high compression ratios.

Engineers measure engines by the number of cylinders and the volume of those cylinders. For example, a 350 V8 is an engine with eight cylinders arranged in a V formation and displacing 350 cubic inches.

In 2021, modern vehicle engines can be more easily understood once divided into their three primary categories, which include:

• Internal combustion engines
• Hybrid engine (Internal combustion engine + electric engine)
• Electric engine

So, let’s discuss different types of engines one by one.

Types Of Engines

Basically, engines are of two types, and these are external combustion engines and internal combustion engines.

#1. External Combustion Engine.

External combustion engines (EC engines) separate the fuel and exhaust products – they burn the fuel in a chamber and heat the working fluid inside the engine through a heat exchanger or the engine wall. The grandfather of the industrial revolution, the steam engine, falls into this category.

In some ways, EC engines work similarly to their IC counterparts – both require heat, which is obtained by burning matter. However, there are also some differences.

EC engines use fluids that undergo thermal dilation contraction or phase shifting, but whose chemical composition remains unchanged.

The fluid used can be either gaseous (as in the Stirling engine), liquid (the organic Rankine cycle engine) or undergoing a phase change (as in the steam engine) – in internal combustion engines the fluid is almost always a liquid fuel, and air mixture, which burns (changes its chemical composition).

Finally, the engines can either drain the fluid after use, as internal combustion engines do (open-cycle engines), or continuously use the same fluid (closed-cycle engines).

#2. Internal Combustion Engine.

The internal combustion engine is an engine in which the combustion of fuel takes place in a confined space called the combustion chamber. This exothermic reaction of a fuel with an oxidizer produces high-temperature, high-pressure gases that can expand.

The defining characteristic of an internal combustion engine is that the expanding hot gases do useful work by acting directly to cause movement, such as by acting on pistons, and rotors, or even pushing and moving the entire engine itself.

Two types of internal combustion engines are currently manufactured: the spark-ignition gasoline engine and the compression-ignition diesel engine.

Most of these are four-stroke engines, meaning it takes four piston strokes to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.

Spark-ignition gasoline and compression-ignition diesel engines differ in how they deliver and ignite the fuel. In a gasoline engine, the fuel is mixed with air and then sucked into the cylinder during the intake process.

After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion.

The expansion of the combustion gases pushes the piston during the power stroke. In a diesel engine, only air is drawn into the engine and then compressed. Diesel engines then spray the fuel in a suitable, metered amount into the hot compressed air, causing it to ignite.

#3. Hybrid Engine.

Quite simply, a hybrid combines at least one electric motor with a petrol engine to move the car, and its system recovers energy through regenerative braking. Sometimes the electric motor does all the work, sometimes it’s the gas engine, and sometimes they work together.

The result is reduced gas mileage and therefore reduced fuel consumption. Adding electrical power can even increase performance in certain cases.

All draw power from a high-voltage battery (separate from the car’s conventional 12-volt battery), which is replenished by capturing energy from deceleration that is normally lost to the heat generated by the brakes in conventional cars. (This is done by the regenerative braking system.)

Hybrids also use the gas engine to charge and maintain the battery. Automakers use different hybrid designs to accomplish different tasks ranging from maximizing fuel savings to keeping vehicle costs as low as possible.

#4. Electric Engine.

Unlike a typical internal combustion engine (ICE) vehicle, which runs on gas, electric vehicles do not require explosive combustion from combusted fuel to generate the energy needed for locomotion.

Instead, they use the electrical energy stored in their batteries to power the electric motor(s) connected to the wheels and propel the car forward.

As a result, electric vehicles have fewer moving parts than gasoline vehicles and generally require less maintenance, although they currently have a higher initial cost.

Electric motors are devices that use electricity to generate mechanical power. They are commonly used to power a wide range of applications, including automobiles, trains, elevators, and appliances.

Electric motors work by using a coil of wire called a rotor, that is placed in a magnetic field. When an electric current is passed through the wire, it creates a magnetic field around the rotor.

The interaction between the magnetic field of the rotor and the magnetic field of the stator (a stationary component of the motor) causes the rotor to spin, generating mechanical power.

There are several types of electric motors, including dc motors, ac motors, and stepper motors. DC motors use direct current (DC) to power the rotor, while AC motors use alternating current (AC).

Stepper motors are a type of electric motor that can be precisely controlled and are commonly used in applications that require precise movements, such as printers and robots.

#5. Steam Engines.

Steam engines are engines that use steam to generate mechanical power. They were once widely used in trains, ships, and other applications, but are now mostly used for generating electricity in power plants.

Steam engines work by heating water to produce steam, which is then used to power a piston or turbine. The steam is created by burning a fuel, such as coal or natural gas, in a boiler.

The heat from the burning fuel is used to heat the water, which produces steam. The steam is then directed through a valve to a cylinder or turbine, where it pushes against a piston or rotor to generate power.

There are two main types of steam engines: reciprocating engines and turbine engines. Reciprocating engines use a piston to convert the steam’s pressure into linear motion, while turbine engines use a rotor to convert the steam’s energy into rotary motion.

#6. Gas Turbine Engines.

Gas turbine engines are engines that use the expansion of hot gases to generate power. They are commonly used in aircraft, power plants, and other applications that require a high power-to-weight ratio.

Gas turbine engines work by compressing air and mixing it with fuel, which is then burned to produce hot gases. The hot gases are then expanded through a turbine, which rotates a shaft and generates power.

The power generated by the turbine is used to drive a compressor, which forces more air into the engine, and a load, such as a generator or an aircraft’s propeller.

There are two main types of gas turbine engines: simple cycle and combined cycle. Simple cycle gas turbine engines are the most basic type and only use a turbine to generate power.

They are efficient at producing high power outputs but have a lower overall efficiency due to the energy that is lost in the exhaust gases.

Combined cycle gas turbine engines are more complex and use two or more thermodynamic cycles to generate power. They typically consist of a gas turbine, a steam turbine, and a heat recovery steam generator (HRSG).

The gas turbine generates power by expanding the hot gases produced by burning fuel. The exhaust gases from the gas turbine are then used to heat water in the HRSG, producing steam. The steam is then expanded through the steam turbine to generate additional power.

Combined cycle gas turbine engines are more efficient than simple cycle gas turbine engines because they can capture more of the energy from the fuel.

#7. Rocket Engines.

Rocket engines are engines that use the principle of action and reaction to generate thrust and propel a vehicle through the air or space. They are used in rockets, missiles, and other spacecraft.

Rocket engines work by burning fuel and an oxidizer, which creates hot gases that are expelled through a nozzle. The hot gases are expelled at high speed, creating a force that pushes against the rocket and propels it forward. This force is known as thrust.

There are several types of rocket engines, including solid rocket engines, liquid rocket engines, and hybrid rocket engines.

Solid rocket engines use solid fuel and an oxidizer that are mixed together and burned to create thrust. They are simple and reliable, but cannot be easily shut off or controlled once they are ignited.

Liquid rocket engines use separate tanks to store the fuel and the oxidizer, which are pumped into the engine and burned to create thrust. They are more complex and require more maintenance, but they can be easily shut off and restarted, making them more flexible and easier to control.

Hybrid rocket engines use a combination of solid fuel and a liquid or gaseous oxidizer. They offer some of the benefits of both solid and liquid rocket engines but are less common due to their lower performance and reliability.

#8. Stirling Engines.

Stirling engines are engines that use a sealed cylinder with a fixed volume to generate power. They can run on a variety of fuels, including solar energy, and are known for their high efficiency and low emissions.

Stirling engines work by using a working fluid, such as air or hydrogen, that is heated and cooled in a sealed cylinder to produce power. The working fluid is heated by an external heat source, such as fuel or solar energy, and then expands as it is heated.

The expansion of the working fluid pushes against a piston or a rotor, generating power. The working fluid is then cooled and contracts and the process is repeated.

Stirling engines are often used in small-scale applications, such as portable generators and refrigeration units, due to their low size and weight. They are also used in some larger applications, such as power plants and ships, due to their high efficiency and low emissions.

#9. Wankel Engines.

Wankel engines are engines that use a rotary design to convert fuel energy into motion. They are named after their inventor, Felix Wankel, and are known for their compact size and high power-to-weight ratio.

Wankel engines work by using a triangular rotor that rotates inside an oval-shaped chamber. The rotor is powered by the expansion of a fuel-air mixture, which pushes against the sides of the chamber and causes the rotor to spin.

The spinning of the rotor generates power, which can be used to drive a load, such as a car or a generator.

Wankel engines are typically smaller and lighter than other types of engines, making them well-suited for use in small, portable applications.

They are also relatively simple and have few moving parts, which makes them easy to maintain. However, they are not as efficient as some other types of engines and are not as widely used.

#10. Pneumatic Engines.

Pneumatic engines are engines that use compressed air to generate power. They are commonly used in industrial applications, such as pneumatic tools and control systems.

Pneumatic engines work by using a compressor to compress air, which is then stored in a tank. The compressed air is then released through a valve, which pushes against a piston or a rotor to generate power.

The power generated by the pneumatic engine can be used to drive a load, such as a tool or a machine.

Pneumatic engines are known for their simplicity, low cost, and ease of maintenance. They are also relatively safe to use, as they do not produce any harmful emissions.

However, they are not as efficient as some other types of engines and are limited by the amount of air that can be stored in the tank.

Different Types Of Internal Combustion Engines

The classification of the engines depends on the types of fuel used, the work cycle, the number of strokes, the type of ignition, the number of cylinders, the arrangement of the cylinders, the arrangement of the valves, the types of cooling, etc.

These engines are used in various areas such as the automotive industry, aircraft industry, shipping industry, etc. depending on their suitability in different areas. So let’s discuss the different engine types one by one.

#1. V Style Engines.

This used to be the most common car engine on the market and is still heavily used by car manufacturers today.

V-engines, one of the most common engine types, have their cylinders arranged in a V-shape and always have an even number of cylinders – the same number on either side of the V.

These engines are usually arranged at a 90-degree angle and are typically found in 6, 8, 10 or 12 cylinders.

V Engines Pros and Cons:

• V-type engines usually boast of high-quality engine displacement and a rigid design.
• They are expensive to maintain and complex for people to understand.
• Compact and allows for more cabin space.
• Ideal for larger family vehicles, trucks, and other automobiles where greater power and towing capacity are required.

Examples of vehicles commonly found in our inventory section with V-style engines include:

• Ford Expedition
• Honda Ridgeline
• Ford F-150
• Honda Odyssey

#2. Inline Engines.

In-line (or “straight”) engines have all the cylinders in a row, meaning they tend to be longer than the V configuration. For this reason, in-line engines are usually found in 3-, 4-, 5- and 6-cylinder variants, as 8 cylinders in a row would be too long to fit in most engine compartments.

BMW is famous for its powerful “line sixes” (in-line 6-cylinder engines). In-line four-cylinder engines have been extremely popular in recent years due to their affordability, fuel economy, and reduced emissions.

Some examples of great, quality used vehicles that have inline engines are:

• Mitsubishi Mirage
• Honda Accord
• Buick Regal
• Chevrolet Cruze

Pros and Cons of an Inline Engine

• These engines are compact and lightweight.
• They are easy to fix.
• They are rather delicate engines.

When shopping for a used sedan, compact, or fuel-efficient vehicle, you should expect to find one with a 4-cylinder inline engine. Their compact size, lightweight materials, and good fuel efficiency make them ideal for powering smaller-sized passenger vehicles.

#3. Flat Engines.

Flat engines (also known as “boxer” engines) are arranged with the cylinders aligned horizontally so that when they fire, they face each other (as if boxing each other). A boxer engine is essentially a V-style engine where the V is opened to lie flat. Boxer engines are known to be used in Porsches and some Subaru models.

Motorcycles, such as the ones made by BMW in 2021, largely rely on two-cylinder flat engines.

High-performance vehicles with flat engines have included the JaguarXK6,

Pros and Cons of Flat Engines

• Vehicles with flat engines are well-balanced and easy to handle.
• They can be huge engines and rather complex to understand.

#4. Rotary Engines.

A rotary engine is an internal combustion engine, like the engine in your car, but it works very differently from the traditional piston engine.

In a piston engine, the same volume of space (the cylinder) alternately performs four different tasks – intake, compression, combustion and exhaust. A rotary motor does the same four jobs, but each happens in its own part of the case.

It’s like having a separate cylinder for each of the four jobs, with the piston continuously moving from one to the next.

Pros and Cons of Rotary Engines

• These engines are simple to understand.
• They are durable engines.
• Very hard to find skilled mechanics in case of failure.

Cylinder Configurations

The number of cylinders a vehicle has helps determine the amount of power an engine can produce. Items like turbochargers allow for extra compression in the combustion chamber, meaning engine power can be increased without adding more cylinders.

The smallest engine configuration is a twin-cylinder, but these don’t offer much power or capacity. However, they are sometimes found on smaller eco-friendly engines.

Three-cylinder engines typically are arranged in a straight-engine layout and can sometimes be found on smaller vehicles or hatchbacks. This compact design provides good fuel economy, and cars can still have a decent amount of power with the addition of a turbocharger.

The most common engine configuration is the four-cylinder, which is found on a variety of vehicles from small to midrange. A four-cylinder engine is set up in an inline design and offers a good amount of engine output.

The number of cylinders in an engine can continue to increase, like six-cylinder engines that are found on high-end performance and sports cars.

FAQs.