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Aviation Info

Discussion on the difference between turboprop and turbofan engines

  • Relese Date:2009-12-20
  • Source:NASC

The engine can be divided into an aspirating engine and a rocket engine, but we only need to know the aspirating engine. The engine must absorb air as a fuel oxidant (combustion agent) and cannot be used outside the atmosphere. A good aero engine should have: "Low fuel consumption" "Compared with air flow carrier", reducing air resistance "safe and reliable operation", "long life" and "easy maintenance". The types of aircraft engines can be divided into different types according to the way of generating thrust: "direct reaction engine" and "indirect reaction engine" are divided into "piston type", "gas turbine type" and "punching jet type" depending on the inhalation method. The "pulse-jet type" and gas-fired type can be further subdivided into: "propeller type" and "turboshaft type" turbo shaft type engine are helicopter engines.

Turboprop engines are gas turbine engines commonly used on aircraft. The driving principle of a turboprop engine is roughly the same as that of a conventional propeller aircraft using a piston engine as a power source, and the force generated by the rotation of the propeller is used as a propulsive force for the aircraft to advance.

The main difference between the piston propeller and the piston propeller is that the propeller of the turboprop engine usually runs at a constant rate, and the propeller of the propeller is different according to the engine speed. There is a change in the speed of the speed.

Although the combustion chamber of the turboprop engine is similar to the turbojet engine, in order to recover more power from the exhaust gas to drive the propeller, the turbine end of the turboprop engine has a higher number of blade stages.

Conversely, since the main propulsive force of the turbojet engine comes from the reaction force generated by the direct discharge of hot gas into the atmosphere, the smaller the blade pitch of the turbine end, the better, only enough recovery power is needed to drive the fan blade on the compression side can be.

In fact, turboprop engines are also more efficient than turbofan engines, but aircraft speeds using turboprop engines are typically lower than those of turbofan engines. The reason is that the bypass ratio of the turboprop engine is usually higher than that of the turbofan engine, but it also causes the blade end portion to have a high speed and the possibility of generating a shock wave.

In addition, because the turbine rotates very fast, there must be a shifting gear between the turbine and the propeller to reduce the propeller speed so that the tip of the blade does not exceed the speed of sound. Therefore, an airplane using a propeller engine will have the weight of multiple shifting gears.

Although turboprop engines are commonly used on smaller or lower speed subsonic aircraft, there are a few aircraft that use turboprops that can be very close to the speed of sound of 500 knots (about 926 km / h, or 575 mph) Airspeed cruising in the air.

Turbofan engine (also known as turbofan engine, turbofan engine) is a type of aero engine, developed by Turbojet.

Compared with turbojet, the main feature is that the area of the first stage compression fan is much larger. In addition to its use as compressed air, it also has the function of a propeller, which can push part of the inhaled air backwards through the periphery of the injection engine.

Turbofan engines (also commonly referred to as turbofan engines) are a type of aircraft engine developed from a turbojet engine (Turbojet). Compared with turbojet, the main feature is that the first-stage compressor has a much larger area and is used as an air propeller (fan) to push part of the sucked air back through the periphery of the jet engine. The part through which the air in the core of the engine passes is called the intrinsic track, and the outer part of the core machine through which only the fan air passes is called the outer duct. The turbofan engine is best suited for flight speeds of 400 to 1,000 km, so most aircraft engines now use turbofans as a source of power.

The Bypass ratio of the turbofan engine is the ratio of the mass of air that does not pass through the combustion chamber per unit time to the mass of air passing through the combustion chamber. A turbofan engine with a bypass ratio of zero is a turbojet engine.

Early turbofan engines and modern fighters used lower turbofan bypass ratios. For example, the world's first turbofan engine, Rolls-Royce Conway, has a bypass ratio of only 0.3.

The bypass ratio of most modern civil aircraft engines is usually above 5. The bypass-high turbine fan engine consumes less fuel, but the thrust is comparable to that of a turbojet engine and is much quieter when in operation.

Source: Intercepted from Wikipedia Reference URL