Fuel Economy in Petrol Engines

Abstract

Charts are given in this paper from which may be found the indicated thermal efficiencies, the fuel consumption per indicated horse-power-hour, and the mean effective pressures which are practically attainable in a compact combustion-chambered petrol engine of any bore between 3 inches and 8 inches when running at any compression ratio between 4/1 and 9/1 and at any speed from 1,000 r.p.m. upwards on an octane, ethyl alcohol, or benzene-air mixture of any strength between 20 per cent weak and 20 per cent rich. From these charts similar information in regard to any mixed petrol may be deduced with fair accuracy. The performance of actual engines is compared with the attainable performance in the light of views, given in some detail, relating to phenomena associated with the working fluid and the combustion of the charge. The conclusion is that improvement in charge mixing within each engine cylinder would lead to better performance. Characteristic merit and demerit curves are suggested which appear to be capable of yielding useful information in regard to the functioning of engines.