comanr Quote:
in curand o teava goala, cel mai tare upgrade!
bravo , esti un mare meserias, avem nevoie de tine, iesi afara.
Ar fi bun un topic remap da sau nu/EGR da sau nu...
Cum vad ca nu ai citit despre egr iti pun eu ceva informatii.
Advantages of EGR:
-Reduced NOx
-Potential reduction of throttling losses on spark ignition engines at part load
-Improved engine life through reduced cylinder temperatures (particularly exhaust valve life)
Disadvantages and Difficulties of EGR:
-Since EGR reduces the available oxygen in the cylinder, the production of particulates (fuel which has only partially combusted) is increased when EGR is applied. This has traditionally been a problem with diesel engines, where the trade-off between NOx and particulates is a familiar one to calibrators.
-The deliberate reduction of the oxygen available in the cylinder will reduce the peak power available from the engine. For this reason the EGR is usually shut off when full power is demanded, so the EGR approach to controlling NOx fails in this situation.
-The EGR valve can not respond instantly to changes in demand, and the exhaust gas takes time to flow around the EGR circuit. This makes the calibration of transient EGR behavior particularly complex- traditionally the EGR valve has been closed during transients and then re-opened once steady state is achieved. However, the spike in NOx / particulate associated with poor EGR control makes transient EGR behavior of interest.
-The recirculated gas is normally introduced into the intake system before the intakes divide in a multi-cylinder engine. Despite this, perfect mixing of the gas is impossible to achieve at all engine speeds / loads and particularly during transient operation. For example poor EGR distribution cylinder-to-cylinder may result in one cylinder receiving too much EGR, causing high particulate emissions, while another cylinder receives too little, resulting in high NOx emissions from that cylinder.
-Although the term EGR usually refers to deliberate, external EGR, there is also a level of internal EGR. This occurs because the residual combustion gas remaining in the cylinder at the end of the exhaust stroke is mixed with the incoming charge. There is therefore a proportion of internal EGR which must be taken into account when planning EGR strategies. The scavenging efficiency will vary with engine load, and in an engine fitted with variable valve timing a further parameter must be considered.
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