CONCEPT OF EGR (EXHAUST GAS RECIRCULATION):
Exhaust gas recirculation (EGR) is an old invention that first was used by spark-ignited engines, but later on was adopted for diesel emission control. There are mainly two types of EGR configurations: high pressure EGR system and low pressure EGR system. In high pressure system, a portion of the exhaust gas upstream of the turbo charger is routed back to the intake manifold. In the low pressure EGR systems, a portion of the exhaust gas is taken from the exhaust pipe, usually after some after treatment device, and introduced between the intake air filter and turbo compressor. EGR systems lower NOx emissions in different ways. First the oxygen concentration in the combustion mixture is reduced by diluting the inlet air with combustion products. Exhaust gas, Second the peak combustion temperature is reduced by dilution and introduction combustion products [6]. It should be noted that most of the NOx emission occurs during lean mixture limits when exhaust gas recirculation is least effective. Hydrocarbon and CO control require lean mixtures. In this project it is used 25% EGR for our thesis. Percentages of EGR can be measured various way. We have measured at this way,
% of EGR = (t2-t1)*100/t2.
Here,
t1 = Time required to fill-up the bag without EGR
t2= Time required to fill-up the bag with EGR