Automatic Predicting Torsional Vibrations on Main Propulsion Plants, Installed Two-Stroke Diesel Engines: Algorithms and Software

Abstract

The main propulsion plant (MPP) on marine sea-going ships consisting of a diesel engine as the main engine and driving the ship propeller is with the torsional vibrations to be calculated in accordance with the Rules for the Classification and Construction of Sea-Going Ships. The Rules are given by one of maritime registers in the world that are the members of IACS, such as Russian Maritime Register of Shipping (RMR), DNV, ABS, at el. The TV calculation (TVC) on the MPP usually is certainly a monumental calculation task and is conducted with special software for TVC. Nowadays, in accordance with the Rules, almost modern software products for TVC have the abilities to calculate the TVs at normal working regimes and at misfire regimes (called by Normal or Misfire regimes relatively) with only one of cylinders of marine diesel engine (MDE) while engine speed range covers from the minimum to maximum values of the operation speeds. The paper presents improved algorithms and software for automatic calculating the TVs (SATVC) at the Normal and the Misfire regimes, in which the misfiring processes appear not only in one cylinder, but also in two of the MDE cylinders together. The SATVC was based on the made mathematical models, algorithms and coded in LabView by authors. The SATVC consists of modules for automatic calculation of freedom TVs (FTVs), excited torsional moments (ETM), excited TVs (ETVs), permitted torsional pressures (PTP), and common management (CTVC). TVC at every working regime of MDE was automatically conducted in the following procedure: Configuration of the MPP for TVC; Calculation of FTVs; Calculation of ETM; Calculation of ETVs); Calculation of ETVs, and solution of the TVC in considered working regime. The working regime of MDE was modeled by a vector of firing coefficients (VFC) of every MDE cylinder.