Analysis of engine tuning for optimum waste heat recovery power

Abstract

A marine diesel engine have an efficiency of 50%, the other 50% can be parted in two, where 25% are heat which is cooled away in the cooling systems and 25% is waste heat in exhaust gases. The waste heat have potential to be useful by converting it to electricity where the gained electricity can be used for propulsion via electric shaft motor. This reports data are received from questionnaires handed out to engine manufacturers and personnel on board ships, and MATLAB simulations. The data proves that combining an Organic Rankine Cycle (ORC) system with a 2-stroke marine diesel engine can improve a ships specific fuel consumption without increasing ships emissions. Simulations were done in order to find an optimal way of tuning for increased combined cycle engine efficiency. Before running the simulation material the environmental limitations needed to be considered whit regard to increased temperature, the engine is under more stress from higher exhaust and cooling water temperature. Mechanical limits needs to be accounted for as well, in particular on the fuel nozzles, pistons and piston rings. These limitations have been examined and compared to adjust the appropriate limits for the calculations. The results of this report show a way to reach optimum tuning for a combined cycle engine. For example does this result prove that by using an Organic Rankine Cycle can the Specific Fuel Oil Consumption be decreased by 12g/kWh. With live operating ships and personnel’s input the report gives an idea for changes that can be made in order to improve fuel consumption, for new builds and current vessels.