Supersonic Transports - Challenges of Supersonic Passenger Flight - Engines


Jet engine design shifts significantly between supersonic and subsonic aircraft. Jet engines, as a class, can supply increased fuel efficiency at supersonic speeds, even though their specific fuel consumption is greater at higher speeds. Because their speed over the ground is greater, this decrease in efficiency is less than proportional to speed until well above Mach 2, and the consumption per mile is lower.

When Concorde was being designed by Aérospatiale–BAC, high bypass jet engines ("turbofan" engines) had not yet been deployed on subsonic aircraft. Had Concorde competed against earlier designs like the Boeing 707 or de Havilland Comet, it would have been much more competitive. When these high bypass jet engines reached commercial service in the 1960s, subsonic jet engines immediately became much more efficient, closer to the efficiency of turbojets at supersonic speeds. One major advantage of the SST disappeared.

Turbofan engines improve efficiency by increasing the amount of cold low-pressure air they accelerate, using some of the energy normally used to accelerate hot air in the classic non-bypass turbojet. The ultimate expression of this design is the turboprop, where almost all of the jet thrust is used to power a very large fan – the propeller. The efficiency curve of the fan design means that the amount of bypass that maximizes overall engine efficiency is a function of forward speed, which decreases from propellers, to fans, to no bypass at all as speed increases. Additionally, the large frontal area taken up by the low-pressure fan at the front of the engine increases drag, especially at supersonic speeds, and means the bypass ratios are much more limited than on subsonic aircraft.

For example, the early Tu-144S was fitted with a low bypass turbofan engine which was much less efficient than Concorde's turbojets in supersonic flight. The later TU-144D featured turbojet engines with comparable efficiency. These limitations meant that SST designs were not able to take advantage of the dramatic improvements in fuel economy that high bypass engines brought to the subsonic market, but they were already more efficient than their subsonic turbofan counterparts.

Read more about this topic:  Supersonic Transports, Challenges of Supersonic Passenger Flight

Other articles related to "engine, engines":

... Zuula is a metasearch engine that provides search results from a number of different search engines ... Results are available from major search engines, such as Google, Yahoo, and Bing, and smaller engines, such as Gigablast and Mojeek ...
Opel Calibra - Engines
... (110 kW/150 bhp C20XE) four-cylinder redtop petrol engines ... In 1992 a turbocharged 2.0 litre engine (150 kW/204 bhp)(a C20LET, the turbocharged version of the C20XE) was added to the range. 1995 saw the introduction of the X20XEV Ecotec engine, a new version of the classic C20XE 16-valve or "red top" engine ...
Vickers VC.1 Viking - Variants
... Viking Prototypes with two 1,675 hp (1,250 kW) Bristol Hercules 130 engines, three built ... production version with geodetic wings and two 1,690 hp (1,261 kW) Bristol Hercules 630 engines ... stressed skin mainplanes and two 1,690 hp (1,261 kW) Bristol Hercules 634 engines ...
Ford Cortina - Other Cars Using Cortina Engines
... The Kent engines used in the Cortina (popularly known as the "Crossflow"), being lightweight, reliable and inexpensive, were popular with several low-volume sports car manufacturers ... The engines are also found in a number of British kit cars, and until recently was the basis of Formula Ford racing, until replaced by the "Zetec" engine ... The Kent engines were also used in several smaller Fords, most notably the Escort, lower end Capris and Fiesta ...
Volvo V70 - Second Generation (2000–2007) - Technical
... the previous generation was the use of five-cylinder, 20 valve inline transverse-mounted engines ... The range featured a naturally aspirated 2.4 litre engine and two turbocharged variants with either low- or high-pressure ... The V70 five cylinder turbo engines in the US market were the base V70 2.5 litre light-pressure turbo straight-five engine with 211 metric horsepower (155 kW 208 hp) at 5,000 rpm and ...

Famous quotes containing the word engines:

    America is like one of those old-fashioned six-cylinder truck engines that can be missing two sparkplugs and have a broken flywheel and have a crankshaft that’s 5000 millimeters off fitting properly, and two bad ball-bearings, and still runs. We’re in that kind of situation. We can have substantial parts of the population committing suicide, and still run and look fairly good.
    Thomas McGuane (b. 1939)