The emission of Oxides of Nitrogen is formed due to high flame temperature, nitrogen content in fuel and air. If combustion at overall lean stoichiometry, the NOx problem might be relieved. The figure.6 shows the emission of Oxides of Nitrogen for without and with preheating for MI oil with respect to brake power. It is seen from the figure that the NOx increases with increase in load. The diesel produced 180pp, at no load and 942 ppm at full load. The MI oil without preheating 66ppm at no load, 310 ppm at 75% of full load and 325 ppm at full load and with preheating83 ppm at no load 249 ppm at 75% of full load and 300 ppm at full load.

The reduction of NOx for preheated oil is 53% at no load, the reduction of 56% at 75% of full load and reduction of 68% at full load than diesel. However the Raw MI oil shows lower NOx at all loads than diesel operation, the reduction in NOx emission is due to lower air entrainment and fuel air mixing rate with MI oil compared to diesel. Thus the peak flame temperature is very low resulting less emission of NOx. The reduction on NOx emission was 55% at initial loads for MI oil, with/without changing the injection timing. At 75% of full load the NOx emission was 689 ppm, raw MI oil 310 ppm, 398 ppm for advance injection timing and 207 ppm for retard injection timing. The emission of NOx was due to peak flame temperature of the combustion. The fuel developed the peak flame temperature less than diesel and producing low NOx. Since the advanced injection timing must have effect on increase in peak flame temperature at high loads with the engine is also at hot working temperature.
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Figure: 6 NOx for MI Oil with/without preheating