INVESTIGATIONS ON THE PERFORMANCE AND EXHAUST EMISSIONS OF A DIESEL: BRAKE THERMAL EFFICIENCY

BRAKE THERMAL EFFICIENCY

The figure.2 shows the brake thermal efficiency of Madhuca Indica oil in diesel engine without and with preheating with respect to Brake power. It can be seen that the engine is operated with maximum efficiency at full load. At the same time at 75% of full load 25.8% efficiency obtained for diesel fuel, 19.9% for Madhuca Indica oil without preheating and 21.8% efficiency with preheating. The raw MI oil without preheating has high viscosity and it affects poor spray characteristics and homogeneity of air fuel mixture.


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Figure. 2 B TE of MI Oil with preheating and without preheating

The improvement in BTE by preheating was 10.5%. The preheating may assist the vegetable oil to spray better; mixing and evaporating would be the reason for improvement in efficiency than raw oil. At 75% of full load the 3 dog advancement did not show any improvement in efficiency but by retarding the timing the engine efficiency at full load from 22.5% for raw oil dropped to 16%. The reduce in BTE may be due the late ignition delay caused the irregular combustion inside the cylinder.

BRAKE SPECIFIC FUEL CONSUMPTION (BSFC)

The figure.3 shows the variation of BSEC for Madhuca Indica with and without preheating with respect to brake power. It is seen from the figure that the bsec decreases with increase in load. The energy consumption of MI oil was more than diesel because of lower calorific value. The preheating of oil shows considerable improvement at higher loads 75% of full load without preheating 4.9 and with preheating 4.58 and at full load without preheating 5.5 and with preheating 4.38. The improvement in BSEC at 75% of full load is 6.5% and at full load 20% was measured due to preheating. Oil preheating at 1300C temperature might have caused more release of heat energy due to better mixing of fuel the main reason for this improvement is due to the improved fuel spray, better mixing and vaporization to better extent helped the preheated oil to release more heat energy resulting less consumption of fuel.
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Figure : 3 BSEC (MJ/KWh) for MI Oil with preheating and without preheating

This shows that the advance in injection at full load helped by reducing delay period and the hot environment also favour to release heat energy than at retarded timing. Further from the test the MI oil can perform efficiency with the same injection timing.