Publication Date:
2019-07-12
Description:
Although the application of a ring cowl to an airplane with an air-cooled engine increases the maximum L/D and the high speed to an appreciable extent, the performance in climb and ceiling is not increased as much as one would expect without analyzing the conditions. When a ring cowl is installed on an airplane, the propeller is set at a higher pitch to allow the engine to turn its rated r.p.m. at the increased high speed. V/nD is increased and the propeller efficiency at high speed is increased slightly. The ratio of r.p.m. at climbing speed, V(sub c) , to the r.p.m. at maximum speed, V (sub m) is dependent upon the ratio of V(sub c) to V(sub m). The increase in V(sub c) for all airplane with ring cowl i s not as great as the increase in V(sub m), so that the ratio V(sub c)/V(sub m) is less than for the airplane without ring. Consequently the r.p.m. and full throttle thrust power available are less at V(sub c) for the airplane with ring cowl and in spite of the increase in L/D due to the installation of the ring, the excess thrust power available for climbing is not appreciably changed. The same method of reasoning accounts for the small increase in absolute ceiling in spite of a large increase in L/D maximum.
Keywords:
Aerodynamics
Type:
NACA-SR-3A
,
NACA Misc. Paper No. 26
Format:
application/pdf
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