A theoretical calculation of the reduction in drag obtainable by ejector action of the exhaust gases when mixed with the cooling air-flow of a typical air-cooled engine

Abstract

The formulae which give the thrust theoretically obtainable in a system where the ejector exhaust is mixed with the engine cooling air are of considerable mathematical complexity, and it is not therefore evident under what conditions the greatest benefit can be obtained from such a system. By considering a special case, it is shown that there is an optimum size of the mixing duct in relation to the exhaust-pipe diameter; and also that the effect of mixing the exhaust gas and cooling air streams is only beneficial when the available total pressure head behind the engine is small.