Speed-Control System for an Aircraft Cabin-Supercharger Drive

Cabin supercharging is becoming extremely important as flight ceilings for military aircraft are extended upward. Many different schemes have been worked out for using main-engine power to drive variable-speed blowers at speeds which will maintain the desired air-flow and cabin pressure at various altitudes. Two fundamental problems are 1. Providing a variable-ratio transmission between the engine and the blower. 2. Controlling the blower speed to maintain the required air delivery. In some cases a third problem arises because the point of air delivery is at a considerable distance from the engine, necessitating either a long transmission of power or the use of long air ducts. Requirements for remote supercharger drives of moderate power may be met by means of a variable-voltage electric coupling. By using suitable motor characteristics the air delivery of a blower connected to such an electric coupling can be controlled by a simple regulator designed to vary current in proportion to voltage. Requirements for the electric equipment are developed, and laboratory tests on a nine-horsepower model are presented to demonstrate that the equipment meets the specified performance.