Gas-turbine engine

A gas-turbine engine is a type of continuous flow internal combustion engine.

Unlike engines that use pistons moving up and down, a gas turbine operates in a steady stream. These engines are vital for modern life because they provide massive amounts of power. They drive aircraft through the sky and propel large ships across oceans. They also power industrial equipment like pumps and gas compressors. In many cases, they are even used to generate electricity for entire cities.

The engine operates using a thermodynamic process known as the Brayton cycle.

This cycle involves several specific steps to turn air into energy. First, atmospheric air enters a compressor, which can be a centrifugal or axial design. This compressor increases the pressure of the air significantly. Next, the high-pressure air enters the combustor section. In this section, fuel is sprayed into the air and ignited. This combustion creates a high-temperature, high-velocity flow of gas. This gas then strikes the blades of a turbine, causing it to spin. This spinning motion creates shaft work, which is the mechanical energy used for tasks.

In a real engine, the energy produced is split between different tasks.

Approximately 60% to 70% of the power produced is used immediately to run the gas generator itself. This means the turbine must produce enough energy to keep the compressor spinning. The remaining energy is used for the engine's specific job. For example, in a turbojet, the remaining high-pressure gases are accelerated through a nozzle to produce thrust. In other designs, the energy might be used to turn a fan or a propeller.

Engineers design different configurations based on how the engine will be used. A turbojet is a basic version that uses exhaust gases for direct thrust. A turbofan uses an extra turbine to drive a large ducted fan, which is more efficient for subsonic flight. A turboprop uses an extra turbine to turn a propeller. For helicopters or land vehicles, a turboshaft engine is used to drive a rotor or a transmission. There is also a power turbine, which is an independent turbine used to drive an electrical generator.

Some engines even use an afterburner to achieve a higher thrust-to-weight ratio for flight.

The history of the gas turbine spans many centuries of discovery.

Early curiosities like Hero's engine demonstrated the basic principles of physics. In 1791, John Barber patented the first true gas turbine design for a horseless carriage. Later, in 1894, Sir Charles Parsons used a steam turbine to propel a very fast ship called the Turbinia. In 1903, Ægidius Elling built the first gas turbine capable of producing more power than it needed to run. By the 1930s, pioneers like Frank Whittle and Hans von Ohain developed the jet engines that would change aviation forever.

Modern technology has allowed these engines to become incredibly powerful and efficient.

One major advancement is the use of single crystal turbine blade technology. This allows engines to operate at much higher temperatures, which increases efficiency. We also see massive differences in scale among these machines. Large jet engines typically operate at rotation speeds between 10,000 and 25,000 rpm. In contrast, tiny micro turbines can spin at speeds as high as 500,000 rpm. This high speed is necessary to maintain the required blade-tip speed for smaller diameters.

Today, gas turbines are connected to many different global systems. They are used in combined-cycle power plants to generate electricity very efficiently.

They also power heavy machinery, such as the AGT1500 engine used in the M1 tank.

From the smallest micro turbine to the largest industrial generator, the Brayton cycle remains the heart of the machine. These engines continue to evolve, pushing the limits of how much work we can extract from a single stream of air.