Engine-Cooling Problems with Venturi Cowling

AFTER DEFINING the expression “venturi cowling” and reviewing briefly the standards by which engine cooling is judged, the author discusses the subject of temperature measurement as a preface to considering the factors affecting engine cooling under venturi cowling. He states that probably the first problem confronting the designer is that of determining the area of the air-entrance passage, and gives examples of the application of the theoretical formula for determining the required entrance and exit areas.

Stating that the inclusion of some sort of inter-cylinder baffle or deflector is vitally important to the design of a venturi cowl if it is to cool the engine satisfactorily, the author states that he cannot recall a venturi-cowl installation in successful commercial use in which some device of this kind is not employed. He then comments upon deflectors and gives illustrations of different types, together with the results obtained therefrom. The subject of oil cooling is analyzed, as is also that of the effect of cooling modifications on speed. Emphasis is laid on the fact that the experimental data and recommendations given apply to nine-cylinder radial engines in the 300 to 450-hp. range. In conclusion, seven specific recommendations are made for the benefit of the designer who wishes to lay out a venturi cowl for a 300 to 450-hp. engine in an airplane which is expected to travel 140 to 180 m.p.h.