Performance Analysis of Carburetor Fuel Metering in SI Engines

This research book investigates the airflow characteristics of a carburetor venturi using CFD for different throttle valve angles. A three-dimensional venturi model was developed and analyzed in ANSYS Fluent. The study evaluated velocity and pressure behavior at throttle angles of 0°, 15°, 30°, and 45°. Results show that low throttle openings produce weak airflow acceleration and insufficient pressure drop. Increasing the throttle angle enhances velocity and reduces static pressure at the venturi throat. The 30° throttle angle provides the best balance between airflow acceleration and pressure distribution. Velocity and pressure contours at 30° show smooth flow with limited separation. At 45°, higher airflow is accompanied by increased turbulence and non-uniform pressure recovery. Flow separation and recirculation downstream of the throttle contribute to energy losses. Overall, the study identifies 30° as the optimum throttle angle for efficient venturi performance and improved air–fuel mixture formation.