Research On Multi-point Mathematical Model Of Ship Diesel Propulsion Plant And Marine Operation Evaluation System

The high-power low-speed diesel engine is still widely used in the bulk carrier, oil tankers, container ships and other large ocean-going ships with its advantages of high thermal efficiency, low fuel consumption, combustible using inferior fuel and so on. Modeling and simulation of large low-speed marine diesel propulsion system can help to analysis its performance and operation characteristics, and lay a foundation for control or application research. Around the topic of marine operation evaluation system, research work focuses on a main line of the simulation and application of marine diesel engine propulsion control system. Marine operation evaluation system includes marine engine simulation model, intelligent evaluation, question library and network communication four parts. Besides the drawback of manual evaluation, for the marine engine simulation model, there is a shortage that the existing model of diesel engine can not meet the special simulation condition such as engine fault and rough sea, and the resetting of PID parameters settings under different control modes for electronic governor of propulsion control simulation system is another problem. Aiming at these shortages, the specific research work of this paper is given as follows.A multi-point mathematical model of ship diesel propulsion plant is built which can meet the demand of marine operation evaluation system. With the modular modeling theory, by taking the large-scale, low-speed two-stroke ship diesel engine MAN B&W 6S35MC as the research object, the simulation model of diesel engine propulsion system including models of air starting bottle, cylinder, scavenge box, exhaust manifold, air cooler, turbocharger and propeller is developed by VC++. During modeling, the model features in full operating range simulation and fault simulation are considered seriously. The simulation contents include three parts, steady-state process simulation, transient process simulation and fault-state simulation. Steady-state process simulation includes the cylinder’s running parameters accurately at different loads, the flow rate at scavenging port and exhaust valve during scavenging, and combustion heat release rate. To verify the accuracy of the model, the simulation results at different load and speed are compared with the experiment data and sea trial data. Transient process simulation includes the process from starting to stable running at any load for both ship and diesel engine and the instantaneous process simulated at an operating state when changed to another. Fault-state simulation includes cylinder fuel shut-off, fuel injection timing ahead or lagged, exhaust valve leakage and so on. The simulation results show that the ship diesel propulsion plant multi-point simulation model can meet the requirement of marine operation evaluation system in the aspect of simulation accuracy.The visual simulation system of controllable pitch propeller propulsion control plant Alphatronic 2000 PCS is developed, and further more, an improved particle swarm optimization algorithm is put forward to research the PID parameter optimization of its electronic governor. Aiming at the existing defects of quick losing of diversity and easily trapped in local optima during the search process for standard particle swarm optimization algorithm, the improved particle swarm algorithm is put forward with diversity enhancing mechanism and neighborhood search strategy (DESPSO). The fitness function of DESPSO is established by considering the overshoot, rise time and steady-state error of output speed of diesel engine as the optimization. The simulation experiment results show that DESPSO has good convergence and stability and higher success rate of optimization, at the same time can be effectively used in ship electronic governor PID parameter optimization.The completion of marine operation evaluation system based on virtual reality is developed by 3ds Max to realize the functions of scene roaming and human-computer interaction. On the base of the visual marine operation evaluation system, a fuzzy evaluation algorithm based on the expert system assessment rules has been proposed for crew operation examination. First, a method based on fuzzy analytic hierarchy process is presented to determine the weight of each question in an examination, and after that this algorithm was accomplished by setting the evaluation rules specific to each question according to a common evaluation rule table initially, and then tracking the variables during the whole operating process. The evaluation proceeded during and after the examination. A proper membership function was chosen to calculate the membership degree for each variable during the evaluation, and a reasonable score was given after the evaluation with a queryable evaluation record. Finally, two operation examples are taken, and the evaluation results being consistent with the scores given by the expert system show that the feasibility of the algorithm is well verified.