Sea Trials have recently been underway for Canada’s new City Class Patrol Frigate (CPF). These trials provided the first opportunity to measure the performance of the new DRES Ball Infra-red Signature Suppression (IRSS) system installed on a ship. Prior to these trials 1/4 scale hot flow model test and computer simulation performance results were available.

The CPF DRES Ball IRSS systems are installed on the exhaust uptakes of the GE LM2500 main gas turbines. The DRES Ball provides both metal surface cooling for all view angles and plume cooling. The DRES Ball significantly reduces the IR signature of the LM2500 exhaust.

This paper presents a comparison between the 1/4 scale hot flow model test results with the full scale sea trial results. Performance variables included in the comparison are; metal surface temperatures, back pressure, plume temperature distribution, and surface static pressures. Because of the confidential nature of the DRES Ball system performance, all classified data has been nondimensionalized so that only relative comparisons can be made between the full scale and 1/4 scale data.

The results show that the full scale system performs better than the 1/4 scale model because of Reynolds number effects. The plume temperature, surface temperatures and back pressure were all lower (better) than in the 1/4 scale model tests. One of the original concerns with the installation was that relative wind would degrade the performance of the DRES Ball onboard a ship. The wind effect was found to be benign during the trials.

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