Marine Engineering

A cargo vessel has admirably coefficient of 500, fuel coefficient of 120,000 and service speed of 19.9 knots. Her propulsion is powered by a single 2-S, 9-cyl. marine engine with compression ratio 22. Cylinder bore 1m and piston stroke 2.5m directly driving a single fixed-pitch screw propeller , at C-MCR the engine delivers 40MW of brake power at 100rpm. The engine can run on diesel fuel (MDO) with formular C12.3H22.2, lower heating value of 42500 kJ/kg and stoichiometric A/F 14.5 employing a diesel cycle or natural gas (NG) mainly consisting of methane with formula CH4, lower heating value of 49770 kJ/kg and stoichiometric A/F 17.2 employing an Otto Cycle. The mechanical efficiency of the engine is 0.95 and all partial engine efficiencies are the same regardless of the fuel employed. Finally, the Fuel Coefficient of the vessel when running on MDO is 120,000. 1. Find SFOC of the engine when running on either fuel mode (MDO or NG). Assuming that both ambient and scavenging air receiver temperature is 35 centrigrade, entrapped air efficiency is 1.0 and total air excess ratio is 2.5. Find the scavenging receiver air pressure required for both fuel modes of the engine (MDO and NG). Then, calculate the turbocharger compressor power requirement and turbocharger turbine power production assuming that isentropic efficiency is 0.85 and 0.80 respectively and the mechanical turbocharger efficiency is 0.98. Finally, write the perfect combustion reaction for each fuel mode showing the mass amounts of fuel, air and combustion product components per cylinder and per cycle. Ambient pressure is 1bar. For air R = 287 J/kg/K, Y = 1.4; for exhaust /combustion gas R = 277 J/kg/K, Y = 1.3