However, when weight and size are not an issue, the cycle's potential for high thermodynamic efficiency makes it ideal for diesel compression ignition engines operating in large, weight-insensitive applications, such as marine propulsion, railway locomotives, and electricity generation.
#Valve timing diagram of 2 stroke engine pdf portable#
Two-stroke gasoline engines with electrical spark ignition are particularly useful in lightweight or portable applications such as chainsaws and motorcycles.
The first truly practical two-stroke engine is attributed to Yorkshireman Alfred Angas Scott, who started producing twin-cylinder water-cooled motorcycles in 1908. On 31 December 1879, German inventor Karl Benz produced a two-stroke gas engine, for which he received a patent in 1880 in Germany. The crankcase-scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day. However, unlike most later two-stroke engines, his had a separate charging cylinder. The first commercial two-stroke engine involving cylinder compression is attributed to Scottish engineer Dugald Clerk, who patented his design in 1881. In regions where regulations are less stringent, or non-existent, small displacement two-stroke engines remain popular in mopeds and motorcycles. In countries and regions with stringent emmissions regulation, two-stroke engines have been phased out in automotive and motorcycle uses. Two-stroke engines have fewer moving parts than four-stroke engines, and thus are cheaper to manufacture. Two-stroke engines often have a high power-to-weight ratio, power being available in a narrow range of rotational speeds called the power band. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust (or scavenging) functions occurring at the same time. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft.
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