Implementation of a Theoretical Carburetor Model in One-Dimensional Engine Simulation Software

The main circuits of a small engine carburetor can be represented as a complex, dynamic, two-phase flow fluid network. This paper presents the theoretical characterization of a dynamic one-dimensional model of fuel and air flow in small engine carburetors and its implementation into a one-dimensional engine simulation software package. This implementation allows for studying the effect of changes in individual carburetor parts on engine performance. The characterization of the model indicated that the dynamic behavior of the entire flow network can be captured by the solution of the instantaneous momentum balance equation on the single-phase liquid elements of the network, simplifying the dynamic model considerably.

The second part of this work discusses the implementation into the one-dimensional engine simulation package, and shows examples of the studies that the coupled implementation allow for. Compared to a steady-state model, the implementation of the dynamic flow network captures enrichment effects due to the inertia of the fluid and the continued flow after the intake valve is closed. Parametric studies showed that the most relevant parameters in the carburetor performance are the diameters of the venturi and main fuel orifice.