Matching Engine and Propeller

Abstract

The torque and shaft speed (rpm) of an engine will be the same as the torque and rpm of the propeller it drives. The marine designer attempts to place this torque_rpm coincidence at a point that will be best by some criterion for the total propulsion plant, and that will be satisfactory for the individual components under all operating conditions. This is the "matching" problem. Basic principles of driver-load relationships, the fundamental problem of choosing the matching point, and allowances for deteriorations in service, are developed here. Effects of towing loads and of auxiliary loads are also discussed. The use of a controllable_pitch propeller complicates the matching, since propeller pitch variations constitute a degree of freedom in addition to that provided by engine fuel control. The marine designer's task with propulsion engines driving this type of propeller is outlined.