Two-stroke diesel engine

Brons two stroke V8 Diesel engine driving a Heemaf generator.

A two stroke diesel engine is a diesel engine that works in two strokes. A diesel engine is an internal combustion engine which operates using the Diesel cycle. Invented in 1892 by German engineer Rudolf Diesel, it was based on the hot bulb engine design and patented on February 23, 1893. During the period of 1900 to 1930, four-stroke diesel engines enjoyed a relative dominance in practical diesel applications. Charles F. Kettering and colleagues, working at the various incarnations of Electro-Motive and at the General Motors Research Corporation during the 1930s, advanced the art and science of two-stroke diesel technology to yield engines with much higher power-to-weight ratios than the two-stroke diesels of old.[1] This work was instrumental in bringing about the dieselisation of railroads in the 1940s and 1950s.[1]

All diesel engines use compression ignition, a process by which fuel is injected after the air is compressed in the combustion chamber causing the fuel to self ignite. By contrast, gasoline engines utilize the Otto cycle, in which fuel and air are mixed before entering the combustion chamber and then ignited by a spark plug.

Two strokes

Two-stroke internal combustion engines are more simple mechanically than four-stroke engines, but more complex in thermodynamic and aerodynamic processes, according to SAE definitions. In a two-stroke engine, the four "cycles" of internal combustion engine theory (intake, compression, ignition, exhaust) occur in one revolution, 360 mechanical degrees, while in a four-stroke engine it occurs in two complete revolutions, 720 mechanical degrees. In a two-stroke engine, more than one function occurs at any given time during the engine's operation.

In most EMD and GM two-stroke engines, very few parameters are variable and all the remaining ones are fixed by the mechanical design of the engines. The scavenging ports are open from 45 degrees before BDC, to 45 degrees after BDC (this parameter is necessarily symmetrical about BDC). The remaining, adjustable, parameters have to do with exhaust valve timing, and these are established in order to maximize combustion gas exhaust, and to maximize charge air intake, and these two parameters are not necessarily symmetrical about TDC (or, for that matter, BDC). A single camshaft operates the poppet-type exhaust valves and the Unit injector, using three lobes: two for exhaust valves (either two valves on the smallest engines or four valves on the largest; and the third for the Unit injector).

Specific to EMD two-stroke engines (567, 645, and 710):

Specific to GM two-stroke (6-71) and related on-road/off-road/marine two-stroke engines:

Notable manufacturers

References

  1. 1.0 1.1 Sloan 1964, pp. 341–353.
  2. Horsepower for naturally aspirated engines (including Roots-blown two-stroke engines) is usually derated 2.5 percent per 1,000 feet (300 m) above mean sea level, a tremendous penalty at the 10,000 feet (3,000 m) or greater elevations which several Western U.S. and Canada railroads operate, and this can amount to a 25 percent power loss. Turbocharging effectively eliminates this derating.
  3. MTU Inc, Detroit Diesel 2-cycle engines.

Bibliography

Works cited

Further reading