Co-Simulation and Dynamic Assessment of Thermal Management Strategies Aboard Naval Surface Ships

The US Navy continues to support applied research on the design, development, and simulation of their future fleet of all-electric ships (AES). Central to the Navy's vision is the use of electricity as the primary energy transport means for the majority of ship systems. For example, ship propulsion has historically been handled by dedicated gas turbines connected directly to reduction gears, which drive a propeller. In the AES concept, prime movers are connected directly to generators, from which electrical power is sent to propulsors (via motor drives), and also to other ship systems. 

The motivation behind this design approach is threefold. First, a future surface ship must be robust and reconfigurable; with an optimal power distribution grid, ship sectors damaged during combat can be isolated from the rest of the grid, thus minimizing damage and prolonging the ship's operability. Second, with a standard modular power grid, maintenance and cost of repair to ship power systems would be more efficient and cost-effective. Finally, the Navy expects to integrate various high-energy weapons and radar systems in future warships. An optimized power distribution grid would allow the ship to employ large pulses of energy required to implement these advanced systems. However, the introduction of advanced electronics and pulsed-energy systems on a surface ship is not without consequences. From a heat generation point of view, the AES will produce significant thermal side effects that have the potential to produce catastrophic failures at both the system and component level. Thermal management is considered an enabler for the technologies likely to appear on an AES.

Currently, the Arleigh Burke DDG-51 class destroyer employs five 200-ton marine chiller units to handle active cooling of ship systems and components. Every shipboard component, from the smallest processor chip to the largest gas turbine, contributes dynamically to this thermal management challenge due to the generation of “waste heat” that must be managed. It has been estimated [1] that, on average, approximately 681 tons of waste heat is rejected from an Arleigh Burke class warship. However, this average value does not capture the magnitude of peak waste heat during transient situations. On a highly dynamic, controls-oriented ship, such as the notional AES, steady-state values provide little utility from a reconfiguration or system failure perspective. When a fully capable AES is deployed, shipboard cooling requirements are predicted to have increased by as much as 700% [1]. However, this steady-state value does not include the integrated effects of dynamic power buildup and adaptive grid response following the introduction of high-energy weapons and sensors. It is the objective of the research reported in this paper to simulate shipboard thermal load management from a dynamic, controls-based, system-level perspective.