Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines

Abstract

In diesel engines, NOx formation is a highly temperature-dependent phenomenon and takes place when the temperature in the combustion chamber exceeds 2000 K. Therefore, in order to reduce NOx emissions in the exhaust, it is necessary to keep peak combustion temperatures under control. One simple way of reducing the NOx emission of a diesel engine is by late injection of fuel into the combustion chamber. This technique is effective but increases fuel consumption by 10-15%, which necessitates the use of more effective NOx reduction techniques like exhaust gas recirculation (EGR). Re-circulating part of the exhaust gas helps in reducing NOx, but appreciable particulate emissions are observed at high loads, hence there is a trade-off between NOx and smoke emission. To get maximum benefit from this trade-off, a particulate trap may be used to reduce the amount of unburnt particulates in EGR, which in turn reduce the particulate emission also. An experimental investigation was conducted to observe the effect of exhaust gas re-circulation on the exhaust gas temperatures and exhaust opacity. The experimental setup for the proposed experiments was developed on a two-cylinder, direct injection, air-cooled, compression ignition engine. A matrix of experiments was conducted for observing the effect of different quantities of EGR on exhaust gas temperatures and opacity.

Water injection effects on the performance and emission characteristics of a CI engine operating with biodiesel

“…The exhaust gas is essentially inert and therefore does not react in the combustion chamber and only absorbs heat [4]. Even though, the EGR has a potential of reducing NOx up to 50%, it has an inherent drawback of increasing the PM emissions [2,19,20]. In addition, the heat absorption by exhaust inert gas in the cylinder chamber results in small amount of power loss from the engine as well.…”

Particulate Characterization and Size Distribution in the Exhaust of a Gasoline Homogeneous Charge Compression Ignition Engine

“…Singh et al (2006) investigated the role of lubricating oil in soot deposition and trace metal emissions from an engine operated with exhaust gas recirculation (EGR). In another research, Agarwal et al (2004) found that EGR increases the smoke opacity of engine exhaust which is because of higher particulate formation. Nam et al (2008) and Agarwal et al (2003) reported that wear particles from engine components such as valves, valve seals, piston rings and turbochargers also cause trace metal emissions in particulates such as silicon, calcium, zinc and phosphorus.…”

Comparison of Measured and Predicted Performance and the Emission Characteristics of Single Cylinder CI Engine using Pongamia Pinnata based Bio-Diesel

“…Figure 13 and figure 14 shows smoke variation with various EGR levels at no load and full load condition respectively. Higher smoke opacity of the exhaust is observed when the engine is operated with EGR compared to without EGR [3,10,12,15,17]. The variations in the smoke opacity level at high loads are higher compared to that at lower loads.…”

“…In case of diesel engines, these penalties include higher specific fuel consumption and particulate matter emissions. Effectively, a tradeoff between NOX and soot is observed with the use of EGR [12][13][14][15]. The reduction in flame temperature reduces the rate of soot oxidation/re-burning.…”