Editing Two-stroke engine (section)

====Uniflow scavenging====
<!-- This section is linked from [[Exhaust pulse pressure charging]] and [[Tuned exhaust]] 
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<gallery mode=packed heights=150px widths=200px>
File:Uniflow 2-stroke diesel animation.gif|Two-stroke diesel uniflow engine animation
File:Diesel engine uniflow.svg|Uniflow scavenging flow schematic
</gallery>

[[File:Ciclo del motore 2T unidirezionale.svg|thumb|right|The uniflow two-stroke cycle:
{{ordered list
| Top dead center (TDC)
| Bottom dead center (BDC)
}}
{{legend|#10ff00|A: Intake (effective scavenging, 135°–225°; necessarily symmetric about BDC; Diesel injection is usually initiated at 4° before TDC)}}
{{legend|#639eff|B: Exhaust}}
{{legend|#ffae21|C: Compression}}
{{legend|#f00|D: Expansion (power)}}]]
In a uniflow engine, the mixture, or "charge air" in the case of a diesel, enters at one end of the cylinder controlled by the piston and the exhaust exits at the other end controlled by an exhaust valve or piston. The scavenging gas-flow is, therefore, in one direction only, hence the name uniflow.

The design using exhaust valve(s) is common in on-road, off-road, and stationary two-stroke engines ([[Detroit Diesel]]), certain small marine two-stroke engines ([[Gray Marine Motor Company]], which adapted the [[Detroit Diesel Series 71]] for [[Gray Marine 6-71 Diesel Engine|marine use]]), certain railroad two-stroke [[diesel locomotive]]s ([[Electro-Motive Diesel]]) and large marine two-stroke main propulsion engines ([[Wärtsilä]]). Ported types are represented by the [[opposed piston]] design in which two pistons are in each cylinder, working in opposite directions such as the [[Junkers Jumo 205]] and [[Napier Deltic]].<ref>{{cite web|url=http://www.iet.aau.dk/sec2/junkers.htm |title=junkers |publisher=Iet.aau.dk |access-date=2009-06-06 |url-status=dead |archive-url=https://web.archive.org/web/20080501215400/http://www.iet.aau.dk/sec2/junkers.htm |archive-date=May 1, 2008 }}</ref> The once-popular [[split-single]] design falls into this class, being effectively a folded uniflow. With advanced-angle exhaust timing, uniflow engines can be supercharged with a crankshaft-driven blower, either piston or Roots-type.<ref>{{cite web |url=https://www.enginehistory.org/Piston/Before1925/EarlyEngines/J/J.shtml |title=Selected Early Engines: Junkers |first=Kimble D. |last=McCutcheon |date=1 August 2022 |website=Engine History |access-date=14 June 2024 |quote=Junkers built experimental two-stroke opposed-piston diesel aircraft engines during WWI, which were derived from a stationary engine line. These featured two crankshafts at the cylinder ends connected by a gear train that also drove the propeller. Two pistons, working in opposite directions in each cylinder, uncovered inlet and exhaust ports near the ends of their strokes. The exhaust port was uncovered first, and when the inlet port was uncovered, a compressed air charge was forced through the cylinders, practically clearing all burnt gases.}}</ref><ref>{{cite web |url=https://airandspace.si.edu/collection-objects/junkers-jumo-207-d-v2-line-6-diesel-engine/nasm_A19660013000 |title=Junkers Jumo 207 D-V2 In-line 6 Diesel Engine |publisher=National Air and Space Museum |access-date=14 June 2024}}</ref>