Gas Turbine Fans
Many times, a low-pressure compressor as a part of a turbofan is called a fan. In most cases, these special fans are capable of absorbing literally thousands of horsepower. This horsepower is what is provided as hot combustion gasses going through the low-pressure turbine expand. When referring to an aircraft, the gas turbine is the output of the turbine, which is used to turn the compressor. As the hot air passes from the turbine, it is then accelerated into the atmosphere through an exhaust nozzle.
Now, if you were to look at a standard jet engine, it would provide anywhere from 100 to 100,000 pounds of thrust, coupled with weights from 30 to 20,000 pounds. A turbofan engine is designed with a large compressor mounted fan. In this case, the thrust is produced by air that passes through this fan, as well as the actual gas generator. From there, the turbofan creates peak thrust at low speeds such as takeoff, which keeps the aircraft stable.
When you look at a turbojet, the difference is that this aircraft has no fan. Instead, all of the thrust is generated from air passing through the gas generator alone. The frontal area of a turbojet is much smaller than a traditional jet, which means peak thrusts can be generated at high speeds. Then, if you were to look at the non-aviation gas turbines, you would find that a portion of the power goes to driving the compressor.
With a gas turbine, you see a number of benefits. For instance, this is capable of producing greater amounts of useful power, especially for smaller size and weight. Another advantage is that with the major components having pure rotation, the mechanical life is much longer and cost of maintenance considerably lower. Then, while gas turbine has to be started by an external means, it can be brought to peak output within minutes. In addition, in this case, several different types of fuel can be used with the most common being natural gas.
On the inside of a turbo fan is a gas turbine engine. In the final stage, a shaft works its way to the front of the engine to power the fan. When it comes to gas turbines, this multiple concentric shaft approach is actually considered standard. In many of the larger turbofans, you might find two distinct compression stages, which are driven by different turbines, as well as the fan turbine. With the fan, the increase for air moving through the engine is greatly increased, which also increases the engine thrust.