Effect of Spark Plug Geometry on the Cyclic Combustion Variability and Fuel Consumption of Gasoline Engines

Abstract

A numerical analysis of the effect of spark plug geometry on the cyclic combustion variability and fuel consumption is presented. Cycle simulations are performed at different operating conditions of a spark-ignition engine including changes of engine speed and load. After calibration of the model constants for an average cycle using the experimental results of the considered engine, the cyclic combustion variability over 1,500 cycles with the application of a classic J-gap spark plug is simulated. With the same values of calibration constants and perturbations of parameters that cause the cyclic combustion variability, cycle simulations are performed with a fine central (iridium) electrode spark plug. The cycle simulation results for the evaluation of combustion stability and fuel consumption are compared with the previous simulation results achieved with the classic spark plug geometry. The application of the iridium spark plug electrode improves the combustion stability over the analyzed operating range of the engine, with a maximum improvement of 13.5% at part load and low engine speed. A reduction of fuel consumption of approximately 1.25% is achieved at part load conditions. The simulation results confirm that the application of the iridium spark plug geometry has potential to improve engine stability and fuel economy.