There still seems to be a bit of confusion out there between what each system does and how they work so hopefully this article can clear things up. So not only will the truck de-rate and shut down when the DEF urea tank goes empty, it will do the same thing at higher temperatures because urea loses its NOx cleaning properties when its over 30 degrees celsius.
However the main treatment process of the exhaust gases is done through a chemical reaction.
Once that happens, we find a decreased amount of oxygen molecules in the combustible air because of the less oxygen-rich exhaust gas resulting in a cooler combustion temperature and reduced NOx gases.
Notably there are two versions of the SCR technology with one using a copper zeolite catalyst and the other using an iron zeolite catalyst. Either or both are used to reduce NOx which is basically excess, unburned oxygen from the combustion process.
However modern diesel engines now utilise both technologies in harmony.
This is what removes particulate matter from the exhaust. That equipment comes in the form of two different methods used in the aftertreatment of the exhaust emissions. It is used in combination with EGR in that it does recirculate some of the exhaust gases back through the engine but only in a marginal amount.
Urea is not very stable either since it freezes at degrees celsius and breaks down between degrees celsius. It uses no new technology, does not create any additional weight to the truck and does not take up valuable real estate on your truck.
Additionally, enhanced EGR requires that more diesel is injected into the DPF for active regenerations — a sort of cleaning process. In addition to that, it makes no use of urea which has a known problem of availability especially at fuelling stations. This solution allows the engine to operate under optimal combustion temperatures but that in turn produces an unacceptable amount of NOx.
The disadvantage is that we now have a less efficient combustion process due to the lower combustion temperature which decreases fuel mileage. This exhaust gas is cooled on its way back to the engine and is mixed with oxygen rich air from the intake.
This reaction effectively produces water and nitrogen which are environmentally safe. A truck will generally burn 40 litres of DEF every kilometers. Either way, below or above 30, the truck will not be meeting EPA standards and may enter limp mode.
Cummins and Paccar have both implemented this version. The exhaust gases are passed through a system called a decomposition reactor which reacts the nitrogen oxide from the exhaust with diesel exhaust fluid DEF which is most commonly a combination of de-ionized water and urea.In the early days, most trucks had only an EGR system with a diesel particulate filter (DPF) inline with the exhaust system so the question of SCR vs EGR was relevant.
However modern diesel engines now utilise both technologies in harmony. The Risk of CO2 Emissions Essay. Essay about Informative Speech on Egr, Dpf, Scr Emission Systems. There has been three major technologies added to diesel exhaust systems since including an EGR, DPF, and SCR that have dramatically reduced NOx emissions (smog gases).
Abstract: Exhaust gas recirculation (EGR) is an effective strategy to control NOx emissions from diesel killarney10mile.com emissions may be further reduced by cooling of the EGR stream.
Drawbacks of EGR include increased PM. Low Emissions Potential of EGR-SCR-DPF and Advanced Fuel Formulations-A Progress Report Low Emissions Potential of EGR-SCR-DPF and Advanced Fuel Formulations-A Progress Report Department of Emissions Research Automotive Products and Emissions Research Division August This approach involves extensive exhaust gas cooling systems, recirculation valves to divert a portion of the exhaust or ultra- high pressure injection, and a diesel particulate filter (DPF), which needs active regeneration to avoid blockages which leads to higher fuel consumption.
Informative Speech on Egr, Dpf, Scr Emission Systems Essay Central Idea Statement: There has been three major technologies added to diesel exhaust systems since including an EGR, DPF, and SCR that have dramatically reduced NOx emissions (smog gases). Introduction I. Who knows the fundamental difference between a gas and .Download