Karanjaoil is obtained from the seeds of Pongamia pinnata tree, native to the tropicaland Asia which offers most suitable climate for its growth. Each fruit ofmedium sized Karanja tree (18 m height) contains 1–2 kidney shaped brownish redkernels with an oil content of 30 to 40%.
The BSFC is increased with increasingproportion of Karanja oil in the blend due to lower calorific value of Karanja oil83,84. The thermal efficiency of the higher Karanja oil blends is observed tobe lower than that of diesel fuel 85. For all the proportions of Karanja blends,the exhaust gas temperature is found to be higher than that of diesel fuel. Karanjaoil blends emitted more CO and CO2 than the mineral diesel. Smoke opacity andNO concentration are found to be lower and higher respectively for lowerKaranja oil blends compared to mineral diesel at all loads. It is suggestedthat lower blends (up to 20%) of Karanja oil can be used as alternate fuel tothe mineral diesel supplies 87.
Sureshkumar et al. 88 observed an increase inBSFC up to B40 from the experiments conducted on a single cylinder, fourstroke, water cooled engine with various blends of Pongamia pinnata methylester (PPME). This could be due to presence of dissolved oxygen in the biodieselthat enables complete combustion. B20 blend emit less CO emission (~50% at 50%load) than diesel fuel. A reduction of(~8.67%) NOX emission is observed with B20 biodiesel blend as compared todiesel. These results suggest that PPME blends up to 40% by volume could replacethe diesel fuel in terms of less emissions and better performance. In contrary,Rao et al.
91 observed higher exhaust gas temperature and NOX emissions forneat Karanja. Higher density, viscosity and surface tension of the biodiesellead to lower BTE (~ upto 6.49%).
Except NOX emission (28.73%), the CO(77.52%), HC (76.
66%) and smoke emissions (36.5%) decreased significantly forall biodiesel-diesel blends as reported by Chauhanet al. too 98.