Simulation And Optimization Of The Performance Of Marine Main Diesel Engine In Waste Heat Utilization System

Because of the significantly improvement on ship’s energy utilization while operating,waste heat utilization on large marine low-speed two-stroke diesel engine has drawn more andmore attention. But due to the high thermal efficiency, the exhaust gas temperature is low,which is not conductive to use the energy contained in exhaust gas, so the increasing of theexhaust temperature is necessary, while the loss on power and economy should be acceptable.In this paper, MAN B&W6S50MC large marine low-speed two-stroke diesel engine as theobject, study on increasing the exhaust gas temperature to more than290°C withoutincreasing fuel consumption no more than2%and the maximum combustion pressure notexceeding the limit, so the waste heat boiler could make full use of the energy in exhaust,thereby the energy utilization of the entire vessel could be improved.First, based on the detailed analysis on the main structure of the6S50MC diesel engineand specific characteristics of the low-speed two-stroke diesel engine, a simulation model isestablished in Matlab/Simulink environment. According to the propulsion characteristic, themodel is verified and the simulation results are compared to the experiment data. Comparisonresults verify the accuracy of the simulation model due to the consistent between simulationresults and the experiment data.Based on the simulation model, the waste heat of the engine is modulated by adjustingthe engine and the turbocharger. While modulateing by adjusting the engine, impacts onmodulation by changing the injection advance angle, the exhaust duration and exhaust gasbypass are studied. Some parameters are chosen from results, the model is simulated bycombinated these parameters, and the simulating results meet the requirements.In the process of modulating by adjusting the turbocharger, impacts on performance byreducing the nozzle area are simulated. A certain nozzle area is chosen based on the results,and by adding the bypass, the model is simulated, and the simulating results meet therequirements as well.On the basis of the characteristics of the marine diesel engine, a thermal equilibriumanalysis on original6S50MC diesel engine and the modulated engine is studied. And thegenerating capacity through power turbine and the waste heat boiler under the rated condition is estimated. The analysis and the calculation results shows that by applying waste heatutilization system to the modulated engine, energy utilization of the whole system could beincreased, and relatively the fuel consumption of the whole system is decreased.