Interactive computer programme to facilitate diesel engine/propeller matching

Abstract The general problem of matching a diesel engine to a propeller is solved using a computer programme. The programme can deal with any engine specified by constraints on its power speed characteristic readily available from manufacturers, and any hull form provided resistance vs speed curves are available either from scale model experiments, standard curves or sea trials. For any selected propeller diameter, gear ratio or propeller blade area ratio the programme automatically calculates the maximum ship speed which just satisfies the engine constraints over a range of propeller pitch ratio values. The calculation is based on using a data bank of previously. stored model series thrust and torque parameters, and the resulting forward speed vs pitch ratio curve is presented on a graphics terminal. Families of these characteristics can be automatically generated for selected variations in propeller diameter, blade area ratio, gear ratio or for different resistance vs speed curves which may represent other ship displacements, trims or account for fouling, weather, etc. The display curves are stored and may be interactively retrieved under light pen control so that rapid comparisons can easily be drawn between different parameter selections. As an example of the use of the programme the paper describes the design of a propulsion system for a small commercial vessel using hypothetical data, and thus demonstrates the sensitivity of speed vs pitch ratio characteristic variations with propeller diameter, gear ratio, blade area ratio and displacement, and some general conclusions may be drawn from the results presented.