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Avgas (aviation gasoline), also known as aviation spirit in the UK, is an aviation fuel used in spark-ignited internal-combustion engines to propel aircraft. ''Avgas'' is distinguished from ''mogas'' (motor gasoline), which is the everyday gasoline used in motor vehicles and some light aircraft. Unlike mogas, which has been formulated since the 1970s to allow the use of platinum-content catalytic converters for pollution reduction, some grades of avgas still contain tetraethyllead (TEL), a toxic substance used to prevent engine knocking (detonation), with ongoing experiments aimed at eventually reducing or eliminating the use of TEL in aviation gasoline. Turbine and diesel engines are designed to use kerosene-based jet fuel. ==Properties== The main petroleum component used in blending avgas is alkylate, which is essentially a mixture of various isooctanes. Some refineries also use reformate. All grades of avgas that meet CAN 2-3, 25-M82 have a density of 6.01 lb/U.S. gal at 15 °C, or 0.721 kg/l. (6 lb/U.S. gal is commonly used for weight and balance computation.) Density increases to 6.41 lb/US gallon, or 0.769 kg/l, at -40 °C, and decreases by about 0.1% per 1C° (1.8F°) increase in temperature. 〔Nav Canada: ''Canada Flight Supplement'', page A40. Nav Canada, 23 November 2006〕 Avgas has an emission coefficient (or factor) of 18.355 pounds CO2 per U.S. gallon (2.1994 kg/l) or about 3.05 units of weight CO2 produced per unit weight of fuel used. Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock. The particular mixtures in use today are the same as when they were first developed in the 1940s, and were used in airline and military aero engines with high levels of supercharging; notably the Rolls-Royce Merlin engine used in the Spitfire and Hurricane fighters, Mosquito fighter-bomber and Lancaster heavy bomber (the Merlin II and later versions required 100-octane fuel), as well as US-made liquid-cooled Allison V-1710 engines, and numerous radial engines from Pratt & Whitney, Wright, and other manufacturers on both sides of the Atlantic. The high octane ratings are achieved by the addition of TEL, a highly toxic substance that was phased out of automotive use in most countries in the late 20th century. Avgas is currently available in several grades with differing maximum lead concentrations. Because TEL is an expensive and polluting ingredient, the minimum amount needed to bring the fuel to the required octane rating is used; actual concentrations are often lower than the permissible maximum. Historically, many post-WWII developed, low-powered 4- and 6-cylinder piston aircraft engines were designed to use leaded fuels; a suitable unleaded replacement fuel has not yet been developed and certified for most of these engines. , numerous certificated reciprocating-engine aircraft require high-octane (leaded) fuels. Teledyne-Continental Motors states: ''"Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead. The result can be remarkable, with cylinder performance deteriorating to unacceptable levels in under 10 hours."'' Lycoming has also provided a list of engines and fuels that are compatible with them. A number of their engines are not compatible with unleaded fuel according to their chart. Jet fuel is similar to kerosene and is used in turbine engines; it is not avgas. Confusion can be caused by the terms Avtur and AvJet being used for jet fuel. In Europe, environmental and cost considerations have led to increasing numbers of aircraft being fitted with fuel-efficient diesel engines that run on jet fuel. Civilian aircraft use Jet-A, Jet-A1, or in severely cold climates Jet-B. There are other classification systems for military turbine and diesel fuel. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「avgas」の詳細全文を読む スポンサード リンク
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