|
Propfan
A propfan, also called an open rotor engine, open fan engine is an aircraft engine combining features of turbofans and turboprops. It uses advanced, curved propeller blades without a ducted fan, duct. Propfans aim to combine the speed capability of turbofans with the fuel efficiency of turboprops, especially at high subsonic speeds. It is sometimes called a "ultra-high-bypass (UHB) turbofan". Definition In the 1970s, Hamilton Standard described its propfan as "a small diameter, highly loaded multiple bladed variable pitch propulsor having swept blades with thin advanced airfoil sections, integrated with a nacelle contoured to retard the airflow through the blades thereby reducing compressibility losses and designed to operate with a turbine engine and using a single stage reduction gear resulting in high performance". In 1982, the weekly aviation magazine Flight International defined the propfan as a propeller with 8–10 highly swept blades that cruised at a speed of , a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
578-DX (on Testbed)
The Pratt & Whitney/Allison 578-DX was an experimental aircraft engine, a hybrid between a turbofan and a turboprop known as a propfan. The engine was designed in the 1980s to power proposed propfan aircraft such as the Boeing 7J7 and the MD-91 and MD-92 derivatives of the McDonnell Douglas MD-80. As of 2019, it is still one of only four different contra-rotating propfan engines to have flown in service or in flight testing. Development The Allison Engine Company, a division of automobile manufacturer General Motors (GM), unveiled its Model 578 contra-rotating propfan engine at the Paris Air Show in mid-1985. The engine represented Allison's attempt to re-enter the commercial airline engine market, because after turboprop aircraft were overtaken in civil aviation in the 1950s and 1960s, Allison was mostly confined to selling military aircraft engines. Targeted to power passenger airliners seating between 100 and 160 passengers, the engine would be based on the core of the Allison ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbofan
A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust. The ratio of the mass-flow of air bypassing the engine core to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together. Engines that use more Propel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contra-rotating Propeller
Aircraft equipped with contra-rotating propellers (CRP) coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single engine piston powered or turboprop engine to drive a pair of coaxial propellers in contra-rotation. Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission. Although contra-rotating propellers are also known as '' counter-rotating propellers'', the term is much more widely used when referring to airscrews on separate non-coaxial shafts turning in opposite directions. Operation When airspeed is low, the mass of the air flowing through the propeller disk (thrust) causes a significant amount of tangential or rotational air flow to be created by the spinning blades. The energy of this tangential air flow is wasted in a single-propeller design, and causes handling problems at low speed as the air strikes the vertical stabilizer, causing the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turboprop
A turboprop is a Gas turbine, gas turbine engine that drives an aircraft Propeller (aeronautics), propeller. A turboprop consists of an intake, reduction drive, reduction gearbox, gas compressor, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the Fuel mixture, fuel-air mixture then Combustion, combusts. The hot combustion gases expand through the turbine stages, generating power at the point of exhaust. Some of the power generated by the turbine is used to drive the compressor and electric generator. The gases are then exhausted from the turbine. In contrast to a turbojet or turbofan, the engine's exhaust gases do not provide enough power to create significant thrust, since almost all of the engine's power is used to drive the propeller. Technological aspects Exhaust thrust in a turboprop is sacrificed in favor of shaft power, which is obtaine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propeller (aircraft)
In aeronautics, an aircraft propeller, also called an airscrew,Beaumont, R.A.; ''Aeronautical Engineering'', Odhams, 1942, Chapter 13, "Airscrews". converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type. The propeller attaches to the power source's driveshaft either directly or through reduction gearing. Propellers can be made from wood, metal or composite materials. Propellers are most suitable for use at subsonic airspeeds generally below about , although supersonic speeds were achieved in the McDonnell XF-88B experimental propeller-equipped aircraft. Supersonic tip-speeds are used in some aircraft like the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerospace Engineer
Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is similar, but deals with the electronics side of aerospace engineering. "Aeronautical engineering" was the original term for the field. As flight technology advanced to include vehicles operating in outer space, the broader term "aerospace engineering" has come into use. Aerospace engineering, particularly the astronautics branch, is often colloquially referred to as "rocket science". Overview Flight vehicles are subjected to demanding conditions such as those caused by changes in atmospheric pressure and temperature, with structural loads applied upon vehicle components. Consequently, they are usually the products of various technological and engineering disciplines including aerodynamics, air propulsion, avionics, materials science, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bypass Ratio
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. 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. Turbofan engines are usually described in terms of BPR, which together with engine pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition, BPR is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR is also quoted for lift fan installations where the fan airflow is remote from the engine and doesn't physically touch the engine core. Bypass provides a lower fuel consumption ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mach Number
The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It is named after the Austrian physicist and philosopher Ernst Mach. \mathrm = \frac, where: * is the local Mach number, * is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and * is the speed of sound in the medium, which in air varies with the square root of the thermodynamic temperature. By definition, at Mach1, the local flow velocity is equal to the speed of sound. At Mach0.65, is 65% of the speed of sound (subsonic), and, at Mach1.35, is 35% faster than the speed of sound (supersonic). The local speed of sound, and hence the Mach number, depends on the temperature of the surrounding gas. The Mach number is primarily used to determine the approximation with which a flow can be treated as an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cruise Altitude
Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term ''altitude'' is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage. In aviation, altitude is typically measured relative to mean sea level or above ground level to ensure safe navigation and flight operations. In geometry and geographical surveys, altitude helps create accurate topographic maps and understand the terrain's elevation. For high-altitude trekking and sports, knowing and adapting to altitude is vital for performance and safety. Higher altitudes mean reduced oxygen levels, which can lead to altitude sickness if proper acclimatization measures are not taken. Vertical distance measurements in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maquette UDF - Musée Safran (cropped)
A ''maquette'' is a scale model or rough draft of an unfinished sculpture or work of architecture. The term is a loanword from French. An equivalent term is ''bozzetto'', a diminutive of the Italian word for a sketch. Sculpture A maquette is used to visualize and test forms and ideas without incurring the expense and effort of producing a full-scale piece. It is the analogue of the painter's cartoon, ''modello'', oil sketch, or drawn sketch. For commissioned works, especially monumental public sculptures, a maquette may be used to show the client how the finished work will relate to its proposed site. The term may also refer to a prototype for a video game, film, or other media. ''Modello'', unlike the other terms, is also used for sketches for two-dimensional works such as paintings. Like oil sketches, these models by highly regarded artists can become as desirable as their completed works, as they show the process of developing an idea. For example, eleven bozzetti by Gia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swept Wing
A swept wing is a wing angled either backward or occasionally forward from its root rather than perpendicular to the fuselage. Swept wings have been flown since the pioneer days of aviation. Wing sweep at high speeds was first investigated in Germany as early as 1935 by Albert Betz and Adolph Busemann, finding application just before the end of the Second World War. It has the effect of delaying the shock waves and accompanying aerodynamic drag rise caused by fluid compressibility near the speed of sound, improving performance. Swept wings are therefore almost always used on jet aircraft designed to fly at these speeds. The term "swept wing" is normally used to mean "swept back", but variants include forward sweep, variable sweep wings and oblique wings in which one side sweeps forward and the other back. The delta wing is also aerodynamically a form of swept wing. Reasons for sweep There are three main reasons for sweeping a wing: 1. to arrange the center of gravity o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Turbine
A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the direction of flow: * a rotating gas compressor * a combustor * a compressor-driving turbine. Additional components have to be added to the gas generator to suit its application. Common to all is an air inlet but with different configurations to suit the requirements of marine use, land use or flight at speeds varying from stationary to supersonic. A propelling nozzle is added to produce thrust for flight. An extra turbine is added to drive a propeller (turboprop) or ducted fan (turbofan) to reduce fuel consumption (by increasing propulsive efficiency) at subsonic flight speeds. An extra turbine is also required to drive a helicopter rotor or land-vehicle transmission (turboshaft), marine propeller or electric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
