Numerical and Experimental Study of Fuel and Air Flow in Carburetors for Small Engines

This work presents a complete model of the carburetor for small engines. It extends the previously published models by incorporating a detailed review of two-phase flow pressure drop, the effect of the fuel well on the control of airbleed flow, and unsteady flow. The homogenous two-phase flow model, which is commonly used in carburetor modeling, was compared with an empirical correlation derived from experiments in small pipes and found to be in poor agreement. In order to assess unsteady flow conditions, the model was extended by solving instantaneous one-dimensional Navier-Stokes equations in single-phase pipes. This strategy proved successful in explaining the mixture enrichment seen under pulsating flow conditions. The model was also used to derive a sensitivity analysis of geometries and physical properties of air and fuel.