Publication Detail

Toward the Development of an Integrated Electric Ship Evaluation Tool

Julie Chalfant, Chryssostomos Chryssostomidis
8 pp.
$5.50 DOM / $7.50 INT

With the advent of energy-intensive weapons and sensor systems visualized for future United States Navy surface combatants, the design of Navy ships is turning to the all-electric ship as a potential solution that enables power sharing between propulsion and other loads. One ramification of the allelectric option is that the resulting electric-drive propulsion systems can be configured such that the motor is directly coupled to the propeller, thus eliminating the need for reduction gears. Current state-of-the-art propellers are rated for approximately 150 rpm; this relatively slow speed in a direct-drive configuration requires extremely large motors. For example, a typical destroyer-sized vessel capable of speeds up to 30 knots requires four motors each weighing approximately 120 metric tons and occupying 86 cubic meters. A high-speed propeller would allow a correspondingly higher speed motor, resulting in reduced motor weight and volume.

Direct evaluation of the weight and volume savings is inadequate; an integrated approach must be used to account for secondary effects. After substituting the new motor and propeller in the baseline ship, we use their efficiencies in conjunction with a typical operating scenario to determine fuel usage.We evaluate cooling system load and make changes as appropriate to include resizing cooling water pumps if necessary. We then analyze layout and arrangements for any necessary changes such as additional tankage or pumping capacity. Overall ship performance including hydrostatic considerations such as draft and trim are evaluated.

This total ship approach allows us to determine the net benefit realized from the high-speed propeller. Net benefits are then compared to the baseline ship to produce interesting tradeoffs such as increased range versus increased payload or designing a smaller ship. Such total ship analysis is valuable as designers go on to answer such questions as the proper distribution system for a particular application, or to analyze the impact of specific technology advances.

Parent Project

Project No.: 2008-ESRDC-01-LEV
Title: Electric Ship Research and Development Consortium (ESRDC)

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