The Townenda Ring is an annular radome of a radial aircraft engine designed to reduce drag . Like its contemporary NACA fairing , the Townend’s ring controls the flow of air both from the outside and from the inside, between the ring and the cylinders, which improves motor cooling.
History
In 1927, Dr. Hubert Townend , a researcher at the National Physical Laboratory ( NPL ) of Great Britain, was studying the streamlining of bodies, monocoque fuselage and airship body. He found that when the annular surface is located at the front of the body under investigation, the total aerodynamic drag decreases. When passing through the ring, the flow accelerated, and the increase in the flow velocity prevented the premature stall and the formation of vortices. Based on this research, he developed the design of the cylinder fairing of a star-shaped engine in the form of a narrow ring, which was called the “Townend Ring”.
The ring, patented in 1929, became typical of high-speed aircraft of the first half of the 1930s with radial air-cooled motors. The installation of the ring gave an increase in maximum speed of 15-25 km / h.
Between 1931 and 1935, NACA and Townenda designs were considered direct competitors; proponents of both designs argued that their choice is better. In the USA, the NACA profile replaced the Townend’s ring thanks to the intervention of the military, who ordered in 1933 a series of Martin B-10 bombers with the NACA fairing (and simultaneously abandoned the Boeing B-9 with the Townend’s ring). According to Martin, the new fairing not only increased speed by 48 km / h, but also significantly reduced landing speed.
As aviation developed, it turned out that the Townend’s ring was effective only at speeds of no more than 400 km / h, and by the end of the 1930s it had ceased to be used in new high-speed developments.