Whatever the source of your fascination is in the world of aviation, you must have seen and heard of different kinds of engines, such as the propeller engines on small planes to the turbine engines on the big jets you see soaring across the sky. You must be wondering what are all the different kinds of aircraft engines, or how the engine on the aircraft matter to its performance.
There are two broad categories of engines that are used for providing mechanical thrust in aircraft: Shaft Engines and Reactive Engines.
Shaft Engines also known as reciprocating engines operate on the principles of internal combustion, converting chemical energy into mechanical energy through a series of small, controlled explosions. The thrust is produced by turning a shaft connected to a propeller, hence the name. They are typically found in smaller aircraft like the Cessna.
On the other hand, Reactive Engines, also known as jet engines suck in a large volume of air, compress it, mix it with fuel, and then ignite it. The resulting force of the hot gases rushing out of the back of the engine propels the aircraft forward. They are commonly seen on commercial airlines like the Boeing 737.
That is just an introduction to the top classification of engines used in aircraft to produce the thrust required to fly the machine. But let’s understand each of these two major categories of aircraft engines in depth.
Overview of Shaft Engines: What are shaft engines in Aircrafts?
Shaft engines, also known as piston engines or reciprocating engines, are a type of engine that utilizes one or more reciprocating pistons to convert pressure into a rotating motion. This process is achieved through four stages: intake, compression, combustion, and exhaust.
During the intake stage, the piston moves down the cylinder while the intake valve opens to allow a mixture of air and fuel into the cylinder. The compression stage sees the piston move upwards, compressing this mixture.
The spark plug ignites the compressed mixture in the combustion stage, causing it to expand and push the piston down, rotating the crankshaft and generating thrust. Finally, in the exhaust stage, the exhaust valve opens to expel the burned gases, and the cycle starts again.
Shaft engines can be further divided into three main types: Reciprocating (Piston) engines, Power turbine engines, and Electric power engines.
Reciprocating (Piston) Engines
Piston engines are the most traditional, utilizing a series of pistons to convert pressure into rotational motion, as described earlier. They are characterized by their simplicity, reliability, and cost-effectiveness. These are the engines that one commonly sees on a single-engine small aircraft like a Cessna 172.
Piston engines, fundamental to the field of aviation, come in various types each with their unique characteristics and applications.
- Horizontal Opposed Engines: These are widely used in general aviation aircraft due to their flat design which allows for improved aircraft stability, causing less drag. Both ends of the cylinder have pistons moving in opposite directions, hence the name.
- Radial Engines: Recognizable by their unique star-shaped configuration, radial engines were primarily used in aircraft before the end of World War II. They are known for their power and reliability, but their large frontal area increases drag.
- In-line Engines: As the name suggests, in-line engines have cylinders arranged in a line. These engines are easier to cool and can be more aerodynamic than radial engines, but they are often heavier.
- V-Type Engines: V-type engines, so named because of the arrangement of cylinders in a ‘V’ shape when viewed from the front, offer a good balance of power, weight, and compactness. They are commonly used in high-performance aircraft.
Each of these engines has played a significant role in the evolution of aviation, offering different advantages depending on the specific needs of the aircraft they are used in.
Power Turbine Engines,
Often referred to as turboprop engines, use a gas turbine to drive a propeller. While more complex and expensive than reciprocating engines, they offer superior performance, especially at higher altitudes and speeds. There are two main types of Power Turbine Engines: Turboprops and Turboshafts.
- Turboprops: Turboprops are the most common type of Power Turbine Engines used in commercial aviation. They use a gas turbine to drive a propeller, generating thrust for both takeoff and cruise flight. These engines can be found on larger aircraft such as turboprop regional airliners, such as the Bombardier Dash 8.
- Turboshafts: Turboshafts are similar to turboprops, except that instead of driving a propeller, they use the turbine’s energy to power an accessory gearbox (usually attached to the crankshaft) that can then be connected directly to the aircraft’s primary power system. This allows the turboshaft engine to be used for applications where more power is needed, such as powering helicopters or drones.
While there are many aircraft manufacturers, did you know that they do not manufacture their own engines? Check here to know why.
Electric Power Engines
Electric power engines represent cutting-edge advancements in aerospace technology. By converting electrical energy into mechanical energy, these engines promise significant reductions in noise and emissions, potentially revolutionizing the future of aviation. However, challenges related to energy storage capacity and weight remain to be solved.
Overview of Reactive Engines: What are Reactive Engines in Aircrafts?
Reactive engines, often referred to as jet engines, have been the backbone of commercial and military aviation for over half a century. Within a reactive engine, air is sucked in through the front of the engine, compressed and mixed with fuel, then ignited. The resulting explosion forces gas out of the back of the engine. This expulsion of gas provides the forward thrust that powers the aircraft.
The most popular kind of Reactive Engines are Jet Turbines which are primarily divided into two categories: Turbojet and Turbofan engines.
- Turbojet Engines: The granddaddy of all jet engines, turbojets were the first type of jet engine to be developed. They are simple in design, compact, and capable of operating at high altitudes and speeds, making them ideal for military aircraft.
- Turbofan Engines: Turbofan engines are a more modern type of jet engine and are commonly used in commercial airliners. They have a large fan at the front that sucks in more air than a turbojet engine. Part of this air bypasses the combustion chamber and is expelled directly out the back, providing additional thrust. This makes turbofan engines more fuel-efficient and quieter than turbojet engines.
Reactive engines have revolutionized air travel, making it faster and more efficient. However, they also have their downsides, including high noise levels and carbon emissions. As the aviation industry moves toward a greener future, new types of engines, like electric and hybrid, are being developed to meet these challenges.
There is always more research and development happening to make aircraft engines more efficient and powerful. Scientists also use biomimicry to mimic nature and make more efficient designs in many innovations. To understand how scientists use biomimicry to make better engineering decisions in the field of aviation check this article.
Some other frequently asked questions about aircraft engines:
What are the main aircraft engines?
The primary types of aircraft engines include Piston Engines, Turbojet Engines, Turbofan Engines, and Turboprop Engines.
- Piston Engines: These are the traditional types of engines that power smaller aircraft. They function similarly to car engines, with pistons driving a propeller to generate thrust.
- Turbojet Engines: Turbojet engines were the first type of jet engines developed. They are simple and compact, operating effectively at high altitudes and speeds.
- Turbofan Engines: These are a more modern type of jet engine, commonly used in commercial airliners. They are more fuel-efficient and quieter than turbojet engines.
- Turboprop Engines: These engines combine elements of jets and props. They have a turbine engine that drives a propeller, which is efficient for slower speeds and shorter distances.
Each type of engine has its own set of advantages and disadvantages, and the choice of engine depends on the specific requirements of the aircraft and its intended use.
What type of engines does Boeing use?
Boeing, one of the largest aircraft manufacturers in the world, utilizes a variety of engines depending on the specific model of the aircraft. For instance, the iconic Boeing 747 primarily uses high-bypass-ratio turbofan engines that are more efficient and quieter, such as the General Electric CF6, Pratt & Whitney JT9D and Rolls-Royce RB211.
Meanwhile, the newer Boeing 787 Dreamliner is powered by either Rolls-Royce Trent 1000 or General Electric GEnx-1B. These engines are designed to be fuel-efficient, reducing both operational costs and environmental impact. The choice of the engine is typically made by the airline placing the order, based on their specific needs and preferences.
What is better than a jet engine?
While jet engines are unmatched in terms of speed and altitude capabilities, electric propulsion is emerging as a promising alternative in the world of aviation. Electric motors, powered by rechargeable batteries, provide a cleaner, quieter, and more sustainable form of propulsion.
They are especially suited for small aircraft and short-haul flights, where their limited range is not a significant drawback. Downsides include the current limitations in battery technology, which restricts range and load capacity.
However, rapid advancements in this field indicate that electric propulsion is poised to play a significant role in the future of aviation, potentially outpacing traditional jet engines in terms of efficiency and environmental friendliness.