Although fans have two primary purposes, which includes moving air to help make a room more comfortable and to improve ventilation, fans come in a wide range of types. Fans available on the market today are not just to help with air but they also provide lighting and decoration. The transformation of the fan is actually quite interesting, with a long history.
While non-electrical fans have been used since ancient Roman and Egyptian days, and even in Asia in the 6th century, it was not until the 16th century when the first mechanical fan was developed known as the Punkah fan and ceiling fans with motors were first introduced by a company called Diehl in the 19th century. Since that time, fan types have evolved where you can now find literally everything and anything you want.
As you are about to discover, fans come in all types. In addition to fans that help keep homes cool, fans are also used in car engines, airplane engines, and other similar applications.
With a table fan, you see basic elements to include a base, blade or blades, armature, motor, lead wires, blade guard, motor housing, oscillator shaft, and oscillator gearbox. With this type of fan, the oscillator is a special part of the fan that is designed to motion the fan from side to side. Then, on both ends of the motor is the axle, which attaches to the blade on one end and the oscillator gearbox on the other end. Table fans come in various sizes, styles, and blade numbers, perfect for office desks, nightstands, tables, and other flat surfaces.
Ceiling fans have become so popular that most homes in the United States have at least one. In this case, the fan is either flush mounted or hung with a downrod. Then, the motor within the motor housing is designed to rotate the blades, which then create movement of the air, thus causing temperatures to feel cooler on the skin. When the blades are reversed in the winter, warm air from close to the ceiling is pushed downward, thus making the room feel warmer. The benefits are incredible to include lower energy bills. Additionally, ceiling fans come with and without light fixtures.
In this case, an electric fan used for improving ventilation could be powered using solar panels rather than electricity. For people interested in cutting costs while still enjoying a more comfortable atmosphere, this is an excellent option. Although there is an initial investment for the solar system, the results are worth it.
For this type of fan, a low-pressure compressor located in a turbofan engine is also known as a fan. In most cases, these special fans help absorb literally thousands of horsepower, which is provided by hot combustion gases being expanded through the low-pressure turbine.
When you have several turbofans, you have an aft fan in which the rotor blades are mounted outward of the turbine rotor blades, which then dispenses along with the need for an LP shaft.
When gas turbine fans were first developed, they were made to rotate at subsonic tip speeds. The result was that the production of shockwaves in the airflow was avoided. Today, supersonic fans still rotate at supersonic tip speeds, which exploit the shockwaves. For some of the more advanced and innovative designs, pressure ratio of more than 2.2:1 is achieved in a single stage. However, the more common ratio would be 1.8:1.
While the supersonic fan is made to rotate at supersonic tip speeds, axial flow is subsonic. With some of beta devices, supersonic axial flow has been demonstrated. In this case, each of the speed lines on the fan map, are horizontal, which is different from conventional fans.
You will find that some ultra-high bypass radio turbofans are capable of dispensing with the fan nacelle. In addition, these fans have a fan rotor without a duct. With this design, the blades are shaped to be much more efficient while at flight speeds to around Mach 0.75.
You will find a good number of ultra-high bypass radio turbofan, demonstrator engines such as what you might find in a Rolls Royce, being incorporated with variable pitch fans. For this, the rotor blade pitch actually works to make low flight speed better.
With an overhung fan, the use is for turbofan engines in which the fan rotor is cantilevered forward, further than the front bearing. The result of this is the fan facilitating inlet guide, vane removal. In addition, the fan rotor blades are the first aerofoils that encounter airflow from the engine.
In some cases, fans on military turbofan engines will use variable geometry. Typically, this is confined to just the inlet guide vanes although there are times when the leading edge of the vane is static, helping to redirect airflow onto the first rotor.
Before wide chord fan blades were introduced, the blades were fitted to turbofan engines in which snubbers are featured. Snubbers on adjacent fan blades are designed to rest against each other, which then improves the vibration characteristics of the blade.
Because snubbers reduce aerodynamic efficiency of fan aerofoils, we have seen Rolls Royce pioneering a better solution known as wide chord fan blades. With an increased blade chord, vibration characteristics are enhanced.
For manufacturers of engines, swept fans blades are now being used to make aerodynamic efficiency better while reducing the level of noise.