Prepared and Demonstrated by Eng: HEMYAR NASSER SALEH ABDO AL-HARAZI. (Aeronautical Engineering ANNA UNIVERSITY: CHENNAI-600025- INDIA.)
First of all, the move an Airplane through the air, thrust is generated by some kind of propulsion system. Most modern airliners use turbofan engines due to their high thrust and good fuel efficiency. On this page, we will discuss some of the fundamentals of turbofan engines.
A turbofan engine is the most modern variation of the basic gas turbine engine. As with other gas turbines, there is a core engine, whose parts and operation are discussed on a separate page. In the turbofan engine, the core engine is surrounded by a fan in the front and an additional turbine at the rear. The fan and fan turbine are composed of many blades, like the core compressor and core turbine, and are connected to an additional shaft. All of this additional turbomachinery is colored green on the schematic. As with the core compressor and turbine, some of the fan blades turn with the shaft and some blades remain stationary. The fan shaft passes through the core shaft for mechanical reasons. This type of arrangement is called a two-spool engine (one “spool” for the fan, one “spool” for the core.) Some advanced engines have additional spools for even higher efficiency.
How does a turbofan engine work? The incoming air is captured by the engine inlet. Some of the incoming air passes through the fan and continues on into the core compressor and then the burner, where it is mixed with fuel and combustion occurs. The hot exhaust passes through the core and fan turbines and then out the nozzle, as in a basic turbojet. The rest of the incoming air passes through the fan and bypasses, or goes around the engine, just like the air through a propeller. The air that goes through the fan has a velocity that is slightly increased from the free stream. So a turbofan gets some of its thrust from the core and some of its thrust from the fan. The ratio of the air that goes around the engine to the air that goes through the core is called the bypass ratio.
Because the fuel flow rate for the core is changed only a small amount by the addition of the fan, a turbofan generates more thrust for nearly the same amount of fuel used by the core. This means that a turbofan is very fuel-efficient. In fact, high bypass ratio turbofans are nearly as fuel-efficient as turboprops. Because the fan is enclosed by the inlet and is composed of many blades, it can operate efficiently at higher speeds than a simple propeller. That is why turbofans are found on high-speed transports and propellers are used on low-speed transports. Low bypass ratio turbofans are still more fuel-efficient than basic turbojets. Many modern fighter planes actually use low bypass ratio turbofans equipped with afterburners. They can then cruise efficiently but still have high thrust when dogfighting. Even though the fighter plane can fly much faster than the speed of sound, the air going into the engine must travel less than the speed of sound for high efficiency. Therefore, the airplane inlet slows the air down from supersonic speeds.
The mathematics describing the thrust of a turbofan engine is given on a separate slide.
Here is the thrust equation for TURBOFAN Engine:
The main idea of this article is to simplify the working and principle of Turbofan Engine, as the turbofan engine is used intensively in Commercial Aircraft due to its fuel Efficiency budget( less consumption of fuel ) as well as its high thrust, BUT we all know that the engine still noisy and in this article, we are going to illustrate the most possible techniques which had been done by various Organizations specializing in the Aviation sector.
In order to reduce the noise of Turbofan Engine is by design one of the following nozzles :
1. BASELINE NOZZLE
2. NOTCHED NOZZLE
3. CHEVRON NOZZLE
LIST OF THE FIGURES WHICH HAS BEEN DESIGNED USING CATIA V5 SOFTWARE :
2. NOTCHED NOZZLE
2. CHEVRON NOZZLE USING ANSYS SOFTWARE FOR ANALYSING THE DESIGNING MODEL OF CHEVRON NOZZLE.
SPEED OF SOUND IN THE AVIATION SECTOR :
1. subsonic speed
2. transonic speed
3. hypersonic speed
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