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01-04-2009, 21:33
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![Stijn's Avatar](image.php?s=4e9c0141f539f8efcb85a31c7387b322&u=78&dateline=1299976055) |
Class of 2003
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Join Date: Dec 2003
Posts: 8,760
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Inmiddels is iedereen het er over eens dat ik er naast zit met mijn 'een diesel die niet rookt loopt niet goed (genoeg)' theorie, dus maar even een stukje tekst waarin duidelijk wordt uitgelegd dat zwarte rook echt geen nutteloze te rijke, weggegooide brandstof is.
Diesel engines produce very little carbon monoxide as they burn the fuel in excess air even at full load, at which point the quantity of fuel injected per cycle is still about 50% lean of stoichiometric. However, they can produce black soot (or more specifically diesel particulate matter) from their exhaust, which consists of unburned carbon compounds. This is caused by local low temperatures where the fuel is not fully atomized. These local low temperatures occur at the cylinder walls and at the outside of large droplets of fuel. At these areas where it is relatively cold, the mixture is rich (contrary to the overall mixture which is lean). The rich mixture has less air to burn and some of the fuel turns into a carbon deposit. Modern car engines use a diesel particulate filter (DPF) to capture carbon particles and then intermittently burn them using extra fuel injected into the engine.
The full load limit of a diesel engine in normal service is defined by the "black smoke limit". Beyond which point the fuel cannot be completely combusted, as the "black smoke limit" is still considerably lean of stoichiometric. It is possible to obtain more power by exceeding it, but the resultant inefficient combustion means that the extra power comes at the price of reduced combustion efficiency, high fuel consumption and dense clouds of smoke. This is only done in specialized applications (such as tractor pulling competitions) where these disadvantages are of little concern
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