An Evaluation of Local Heating as a Means of Fuel Evaporation for Gasoline Engines 860246
The technique of evaporating fuel by localized heating before entering the intake manifold is evaluated as a means of improving A/F ratio control. Techniques currently in use are briefly discussed, and attempts to analyze fuel evaporation in S.I. engines are reviewed. A test fixture which includes all the essential features of production feasible hardware is used to develop a basis of understanding for the evaporation process. Tests are conducted on a flow bench using water as “fuel”, and on an engine using isooctane and gasoline. A heat-mass transfer analogy is described and used to predict evaporation rates for water and isooctane. Predicted and measured rates are compared for both bench and engine tests. Engine tests with gasoline show the ability of the test configuration to evaporate all part throttle fuel flow before it enters the intake manifold. Results are presented which show the ability of local heating to reduce A/F excursions on the 1.6 Liter engine by 80% over the ambient temperature range of 0°F to 70°F. Results showing the elimination of cylinder to cylinder A/F maldistribution are presented, and recommended operating temperatures and heat inputs for engine operation are also presented.