Gas Turbine Engine vs Reciprocating Engine (Piston Engine)
Like all the other machinery, aircraft needs a power source to operate, especially to generate thrust which is required to move the aircraft forward. From the earliest attempts reciprocating engines working on petrol were used for powered flight.
The world’s first heavier than air powered flight was made by the Wright Flyer I, and it was powered with a single 4- cylinder water-cooled piston engine which produced 12 horse power at maximum. Until the WWII, every plane was powered with reciprocating / piston engines.
At the latter stages of the WWII, Germans used the jet engine to power aircrafts, and other countries soon followed. Even though the concept and design have been developed since 1930’s, the successful implementation of the jet engine came only after the end of WWII.
Since then due to their multitude of advantages over reciprocating engines the jet engine and it variants have become the predominant form of power plant for aircrafts.
More about Reciprocating Engine (Piston Engine)
A reciprocating engine, also known as a piston engine is a machine with reciprocating pistons, which converts the thermal energy from a combustion process into mechanical work, such as shaft work. The main engine type used in the aircrafts are based on fossil fuel combustion and called internal combustion engines.
Mechanics of the engine is to move a shaft connected to a piston cylinder mechanism by creating large pressure inside the cylinder. Depending on the way cylinders are arranged around the shaft they are categorized into Straight (vertical), rotary, radial, V-type, and horizontally opposed categories.
The engine types mentioned above operate on Otto cycle, and they were used in most of the aircraft in the early 20th century. Usually they are used to drive a propeller, which generate the thrust. Any aircraft operating on piston engines has relatively low maximum speeds, and the power produced by the engines is comparatively less than jet engines. The reason is that the powers to weight ratio of the piston engines are very low and, if more power is required, the engine size has to be increased and that increases the overall weight of the aircraft, which is not desirable for aircrafts. The design and production of the piston engines are less complex and requires lesser maintenance and the cost f the piston engines are also low.
More about Gas Turbine Engine
Gas turbine engine or simply a gas turbine is an internal combustion engine, using gases such as air as the working fluid. Thermodynamic aspect of the operation of the gas turbine is ideally modelled by the Brayton cycle. Gas turbine engines work based on rotary components and, therefore, has a working fluid flowing continuously through the engine in either radial or axial directions. They are the underlying principal component of the jet engine.
The main components of the gas turbine engine are the compressor, combustion chamber, and the turbine, and sometimes, a nozzle. They operate by bringing the working fluid into different thermodynamic states and extracting shaft work or thrust at the exhaust. If the thrust generated from the exhaust is used, it is known as a turbo jet engine; if the turbine extracts some portion of the work and drives a fan, it is known as a turbofan engine. The engine type that extracts almost all the work as the shaft work of the turbine is known as a turboshaft engine; if a propeller is driven by the shaft, it is known as a turbo prop engine.
Many variants of the gas turbines exist, designed for specific tasks. They are preferred over other engines (mainly reciprocating engines) due to their high power to weight ratio, less vibration, high operation speeds and reliability.
What is the difference between Gas Turbine and Reciprocating Engine (Piston Engine)?
• Piston engines have reciprocating mechanisms (to and from motion) while gas turbine engines have rotary mechanisms.
• Both use the air as the working fluid, but the flow in gas turbines is continuous while reciprocating engines have an intermittent flow.
• Power to weight ratio of the gas turbine engines is much higher than that of reciprocating engines.
• Gas turbines are sophisticated in design and manufacture, while reciprocating engines are simpler in design and easier to manufacture.
• Maintenance of the reciprocating engines are simpler and has to be performed frequently, while maintenance of the gas turbine engines is complex, but the inspection and maintenance occurs at longer intervals.
• Gas turbine engines or its variants are expensive, while reciprocating engines are relatively inexpensive.
• Gas turbine engines power large and powerful aircrafts such as military jet fighters or commercial airliner, but piston engine are being used in smaller and short ranged aircraft.