Relevant challenges in crash-stop studies

Abstract

Object and purpose of research. This paper discusses crash-stop of ship propellers. The puspose of the study was to investigate a number of relevant challenges in this process, i.e. to refine the methods of crash-stop distance calculation, to update the scenarios for which crash-stop strength of propeller blades has to be verified, as well as to determine operational parameters and algorithms for automatic control systems of electric power plants in crash-stop conditions. Subject matter and methods. The study was based on the results of quasi-crash-stop model tests, as well as on previous publications about crash-stop maneuvers of ships and operations of their propulsion systems in these conditions. Main results. To obtain more accurate crash-stop distance estimates, it was suggested to use an alternative, bollard-pull system of propeller-hull interaction coefficients for crash-stop conditions. It was also suggested to perform crash-stop strength check of propellers not only for the scenarios with maximum hydrodynamic load, but also for the moment of propeller rotation direction reversal because it might be accompanied by considerable inertial loads. It is shown that model testing is not helpful in determination of operational parameters and automatic control system algorithms for electric power plants because shaft lines cannot be simulated correctly. These parameters can be obtained through calculations, but this will require more refined expressions for shaft line friction moments. Conclusion. The actual problems of ship reverse propulsion theory is presented in the paper. The possible approaches to their solution are proposed.