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The high-bypass turbofan engines used on many modern airliners is an example of a very successful and popular use of ducted fan design. The duct increases thrust efficiency by up to 90% in most cases [citation needed], in comparison to a similar-sized propeller in free air. Ducted fans are quieter, and offer good opportunities for thrust vectoring.
An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the ...
The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. [1] A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.
A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter.
A propfan, also called an open rotor engine, open fan engine [1] [2] or unducted fan (as opposed to a ducted fan), is a type of aircraft engine related in concept to both the turboprop and turbofan, but distinct from both. The design is intended to offer the speed and performance of a turbofan, with the fuel economy of a turboprop.
A turbofan achieves this by using an additional turbine to drive a ducted fan to blow air that bypasses the high speed core. With a lower core thrust, most of the thrust now comes from the large mass of low speed bypass air, providing the same thrust with a reduced fuel burn. The other penalty is that combustion is less efficient at lower speeds.
Unlike ducted engines, rockets give thrust even when the two speeds are equal. In 1903, Konstantin Tsiolkovsky discussed the average propulsive efficiency of a rocket, which he called the utilization ( utilizatsiya ), the "portion of the total work of the explosive material transferred to the rocket" as opposed to the exhaust gas.
Aircraft whose primary form of thrust is derived from a piston engine, rotary engine or turboshaft driving a ducted fan. Subcategories This category has the following 2 subcategories, out of 2 total.