Wind-tunnel Tests of Carburetor-intake Rams

An investigation was conducted in the NACA 20-foot wind tunnel of the ramming effect of three general types of carburetor intake rams for radial engines, namely, the internal constant area type, the external constant area type, and the external expanding type. The rams were installed on a radial air- cooled engine nacelle, and tests were made with and without the propeller operating. The results indicated that the external types having entrances near the front of the engine cowling gave the greatest ramming effect. The propeller increased the ramming effect for the external types. From considerations of the ramming effect, the best entrance location for the external types was close to the nose of the engine cowling. For the internal type, the best location was in a plane perpendicular to the propeller shaft and immediately forward of the engine cylinders.