Reduction of acoustic and infrared emissions from a mil. std. 1.5-kW engine-generator set

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This is a report of a program conducted jointly by Bolt Beranek and Newman and the U.S. Army Mobility Equipment Research and Development Center. The program was to reduce the acoustic and infrared emissions from a MIL. Std. 1.5 kW gasoline engine-generator. A goal for inaudibility at 100 m in a jungle environment is derived and a feasibility study conducted into ways of achieving it. Of equal importance is the provision of adequate cooling for the engine generator so that it can operate over the temperature range −50°F to +125°F. A new exhaust muffler was designed for the engine, an aluminum enclosure was employed, based upon a standard transit case lined with fiberglass and perforated metal, and new vibration mounts were used. Separate lined inlet and exhaust ducts were employed for the cooling air and inadvertent internal recirculation of the air was prevented. Adequate cooling was then obtained over the whole temperature range. A total noise reduction of 23 dBA was achieved for a unit with a final weight of 217 lb and a volume of 9.5 ft3.