Impact of Cold and Hot Exhaust Gas Recirculation on Diesel Engine
Today most of the transport vehicles in countries like India where cost effective is the predominant criteria utilize diesel engines rather than petrol engines. From past 5 years usage of diesel engines was rapid which can be addressed from the sales report of many automobile companies. The reason behind this could be cost of diesel fuel and efficiency of the diesel engine when compared to petrol engine. But when we look on the worse side of diesel engine, emissions from diesel engine are high especially NOx. So there is a need for a technique which could reduce the emissions without affecting the performance of engine. One such technique could be Exhaust gas recirculation. Present paper aims to find the impact of cold and hot EGR on emissions of diesel engine.
Effect of cooling the recirculated exhaust gases on diesel engine emissions
Abstract Although combustion is essential in most energy generation processes, it is one of the major causes of air pollution. Spiral fin exhaust pipes were designed to study the effect of cooling the recirculated exhaust gases (EGR) of Diesel engines on the chemical composition of the exhaust gases and the reduction in the percentages of pollutant emissions. The gases examined in this study were oxides of nitrogen (NO x ), carbon dioxide (CO 2 ) and carbon monoxide (CO). In addition, O 2 concentration in the exhaust was measured. The two designs adopted in this study were exhaust pipes with solid and hollow fins around them. The first type uses air flow around the fins to cool the exhaust gases. The second type consists of hollow fins around the exhaust pipe to allow cooling water to flow in the hollow passage. Different combinations and arrangements of the solid and hollow fins exhaust pipes were used. It was found that decreasing the temperature of the EGR resulted in reductions in the oxides of nitrogen (NO x ) and carbon dioxide (CO 2 ) but increased the carbon monoxide (CO) in the exhaust gases. In addition, the oxygen (O 2 ) concentration in the exhaust was decreased. As a general trend, the percentages of reduction in the NO x gas concentrations were lower than the percentages of increase in the CO emissions as a result of cooling the EGR of a Diesel engine by a heat exchanger. Using water as a cooling medium decreased the exhaust gases temperature and the amount of pollutants more than did air as a cooling medium. In a separate series of tests, increasing the cooled EGR ratios decreased the exhaust NO x but increased the particulate matter concentrations in the exhaust gases.
The effect of EGR rates on NOX and smoke emissions of an IDI diesel engine fuelled with Jatropha biodiesel blends.
The depletion of fossil fuels and the worst impact on environmental pollution caused of their burning 
have led to the search for renewable clean energies. Nowadays, there are many sources of renewable 
energy. Biodiesel is just one source, but a very important one. Biodiesel has been known as an attractive 
alternative fuel although biodiesel produced from edible oil is very expensive than conventional diesel. 
Therefore, the uses of biodiesel produced from non-edible oils are much better option. Currently Jatropha 
biodiesel (JBD) is receiving attention as an alternative fuel for diesel engine. However, previous studies 
have reported that combustion of JBD emitted higher nitrogen oxides (NOX), while hydrocarbon (HC) 
and smoke emissions were lower than conventional diesel fuel. Exhaust gas recirculation (EGR) is one of 
the techniques being used to reduce NOX emission from diesel engines; because it decreases both flame 
temperature and oxygen concentration in the combustion chamber. Some studies succeeded to reduce 
NOX emission from biodiesel fuelled engines using EGR; but they observed increase in smoke emission 
with increasing engine load and EGR rate. The aim of the present work is to investigate the effect of 
EGR on an indirect injection (IDI) diesel engine fuelled with JBD blends in order to reduce NOX and 
smoke emissions. A 4-cylinder, water-cooled, turbocharged, IDI diesel engine was used for investigation. 
Smoke, NOX, carbon monoxide (CO) and carbon dioxide (CO2) emissions were recorded and various 
engine performance parameters were also evaluated. The results showed that, at 5% EGR with JB5, both 
NOX and smoke opacity were reduced by 27% and 17% respectively. Furthermore, JB20 along with 10% 
EGR was also able to reduce both NOX and smoke emission by 36% and 31%, respectively compared to 
diesel fuel without EGR.