Modeling And Simulation And Performance Study Of Propulsion System For Large Semi-Submersible Heavy Lift Vessel

The navigation conditions of a Semi-Submersible Heavy Lift Vessel(SSHLV)are rather complex and variable.When investigate the performance of the propulsion system for SSHLV,both the independent features of individual parts and the matching characteristics of the whole system are necessary to consider,not only the steady state performance but also the transient behavior of the propulsion system need to be taken into account.For the purpose of saving cost,increasing efficiency and improving security,it is of great necessary and importance to model and simulate the propulsion system of SSHLV.In present dissertation,a modularized model of the conventional propulsion system for SSHLV is built in the MATLAB/SIMULINK simulation environment.A mean value model of the diesel engine is built in this paper.The in-cylinder process of the diesel is modeled with the application of the basic Seiliger cycle.Using the parameters and stages defined in the Seiliger cycle it is possible to characterize the in-cylinder process.Based on the diesel engine test data,the influence on the combustion parameters by the working condition is investigated.Polynomial formula for calculating the isochoric combustion parameter is obtained and corrected by using multivariable regression fitting method with the test data.The isobaric combustion parameter is calculated according to the energy conservation law after the isochoric combustion parameter is determined.The gas exchange process is modeled using the quasi-steady state method.The model of the controllable pitch propeller and hull resistance are built respectively on the basis of the open water characteristics and the hull resistance curve.Based on the Wageningen B-screw series,the open water characteristics of the controllable pitch propeller is obtaind.The hull restistance of the SSHLV is calculated using the Holtrop-Mennen method.According to the simulation results,both the steady-state and transient-state performance of the propulsion system under the design navigation condition are researched for the SSHLV.The steady-state performances under the off-design conditions are also investigated.Both the influences on the propulsion system performance by the resistance characteristics and the propeller pitch are studied.The adjustment rule of the propeller pitch under different conditions is provided.The results show that the model can be applied to the performanceresearch of the propulsion system for the SSHLV effectively and can be used for the matching analysis and the integration design of the propulsion system during the early design phase of the ship.