Study of upgraded biogas as a fuel for diesel engine in dual fuel mode with and without thermal barrier coating

Abstract

newlineThe present thesis focusses on addressing to the faster depletion of fossil fuel and newlineenvironmental pollution in addition to the energy crisis that hinders the progress of a newlinenation. Towards this end, extensive laboratory experiments were conducted for production newlineof biogas from semidried banana leaves by adopting anaerobic digestion process. To newlineimprove the quality of raw biogas, a single column scrubbing unit with NaOH solution newlinespray arrangement is fabricated, which is capable to enrich the CH4 content in upgraded newlinebiogas (UBG) up to 87.02% by absorption of CO2. Then, the UBG is compressed and newlinestoried in cylinders. The compressed UBG was used for running of a single cylinder, 4 newlinestroke, water cooled diesel engine in dual fuel mode. UBG was inducted in three different newlineflow rates (0.6, 0.8 and 1.0 kg h-1) at the inlet manifold of the engine. In the next set of newlineinvestigations, the un-coated piston and valves of the diesel engine were replaced with newlineyttria stabilized zirconia (YSZ) coated piston and valves to observe its influence on engine newlineperformance, combustion and emission characteristics. newlineThe combustion characteristics, engine performance and emission characteristics, at newlinefull load operations with dual fuel mode were seen to be important function of the UBG newlineflow rates. The brake thermal efficiency (BTE), brake specific energy consumption newline(BSEC), exhaust gas temperature, smoke opacity, CO and HC emissions, the peak value of newlinemean combustion temperature (MCT), cylinder pressure and rate of heat release (RHR) newlinewere found to be affected by altering the UBG flow rates. It was observed that, at full load newlineoperation, the engine exhibited a drop in BTE in dual fuel mode by 23, 29 and 34% for newlineUBG flow rates 0.6, 0.8 and 1 kg h-1 respectively as compared to base results of diesel newlinealone operation. As a consequence of this, BSEC increased by 23, 24 and 30% for the newlinerespective flow rates of UBG. The exergy efficiency also decreased with increase in newlinedestruction of exergy at all engine loads for dual fuel operation. This emphasized the newlineadaptation of advanced technology for improved performance of dual fuel engine, newlinecombatting the poor combustion characteristics of biogas. newlineThe engine performance with coated engine in dual fuel mode, was seen to have newlineimproved compared to uncoated engine. The coated engine was found to have higher newlinevii newlinebiogas energy share (BGES) indicating improvement in combustion process. Also decrease newlinein destruction of exergy and BSEC conforming the improvement in combustion process newlinedue to coating. Out of the three chosen UBG flow rates 0.8 kg h-1 flow rate exhibited an newlineoverall suitable performance for both coated and uncoated engine.