Unlike 4-stroke Diesel engines, 2-stroke Diesel engines use a 2-stroke Diesel cycle, and are much more energy efficient (50% efficient as opposed to 35% of 4-stroke Diesel engines). The 2-stroke Diesel engine cycle differs significanly from 2-stroke gasoline engines as they do not mix lubricants with the fuel. They hence avoid all of the extra pollution (compared to 4-stroke engines) that normally occurs in the case with gasoline engines. This, unlike gasoline 2-stroke engines, makes them a appropriate technology 2-stroke engines.
Types
As a appropriate technology, only 2 types of engines are suitable: the 2-stroke trunk piston (these btw also come in 4-stroke versions, but we won't go into that) and the 2-stroke (uniflow or loop scavanged) crosshead Diesel engine. Both need to be made to use indirect fuel injection.
Both the 2-stroke trunk piston and crosshead Diesel engines, but especially the last engine have the advantage of being able to use all types of liquid biofuels (including pure plant oil, cleaned and even uncleaned waste vegetable oil). We will describe only the crosshead Diesel engine in this article, as the trunk piston engine is less suitable.
Design charisteristics
Unlike what one would expect, the design of the 2-stroke crosshead Diesel engine is actually very uncomplicated. The loop scavanged crosshead Diesel engine is even a bit simpler in design as the uniflow crosshead Diesel engine, as it has no valves at all, however as the effiency is less, the use of the uniflow crosshead Diesel engine is preferred.
Criticism
The 2-stroke crosshead Diesel engine has a very bad reputation on pollution/emissions. they are generally being used today in large ships. However, they are generally run on very poor quality (undistilled) petrofuels, which causes the huge amount of pollution/emissions. The engine itself however is extremely well designed. As such, when running on biofuels (ie SVO, WVO -either cleaned or uncleaned-), air pollution is minor, and emissions are almost entirely eliminated.
See also
- Internal combustion engine
- Electricity_generator: use of Diesel engine as gen-set, suitable as it allows running on optimal speed/load
Further information
- http://en.wikipedia.org/wiki/Diesel_engine#Low-speed_diesels
- http://en.wikipedia.org/wiki/Diesel_engine#Low-speed_engines
- http://www.marinediesels.info/Basics/the_2_stroke_engine_explanation.htm
- http://www.marinediesels.info/Basics/the_2_stroke_crosshead_engine_explanation.htm
- http://en.wikipedia.org/w/index.php?title=Two-stroke_diesel_engine&printable=yes
- http://en.wikipedia.org/wiki/Piston#Trunk_pistons
- http://www.emma-maersk.com/engine/Wartsila_Sulzer_RTA96-C.htm
- http://www.appropedia.org/Internal_combustion_engine (external links)
- 2-stroke diesel; use in developing world (chennai)
- [http://www.marinediesels.info/4_stroke_trunk_piston_engine_access.htm