THIS paper is a concluding report on that phase of the equilibrium-volatility work at the Bureau of Standards which is applicable to engine performance as affected by vaporization in the manifold. New data on bubble-points are presented and an improved method is outlined for obtaining temperatures on specific air-vapor mixtures from the experimental observations. By taking into consideration the slope of the A.S.T.M. distillation curve, the 16-1 temperature at any percentage evaporated from 0 to 100 per cent can be computed from the A.S.T.M. temperature with an average deviation of 1 deg. cent. (2 deg. fahr.) by means of simple relations which are applicable to pure hydrocarbons and hydrocarbon mixtures, of any degree of complexity, within the gasoline range. Values for other mixtures can be readily obtained from the 16-1 temperatures.
Two alignment charts and a duplex chart, given and explained in the Appendix, are useful for quickly evaluating bubble-points, data from 0 to 90 per cent evaporated, dew-points and temperatures for easy engine starting.
In the discussion, a description is given of the method followed at the University of Michigan in which the equilibrium volatility is plotted with temperatures as ordinates and percentage vaporized, by weight, as abscissas for a particular air-fuel ratio supplied by the carbureter or to the equilibrium apparatus. It is recommended that the results of the volatility-data study be printed in detail in pamphlet form for distribution, and the author of the paper says that this is now under consideration. It is stated by one of the discussers that fuel volatility comes first, mixture-distribution second, and then combustion-chamber design. After determining the fuel volatility, the first part of the engine design relates to inductance of the fuel, because the entire power of the engine depends upon its ability to breathe in and burn that fuel. Supplying constant intake temperature as a carburization means, using oil, is discussed also.