Simulation Models for Spark Ignition Engine: A Comparative Performance Study

Abstract

A single-zone zero-dimensional model for any hydrocarbon fuel based on Wiebe heat release function has been implemented in Simulink to test the performance of spark ignition engine. Annand's model for convective heat losses is taken for modeling of engine cycle. The Simulink results are validated with experimental results from literature. The peak pressure during combustion drops with decrease in intake pressure which is similar to the experimental trend. With increase in speed from 1000rpm to 4000rpm, the brake thermal efficiency drops from 25% to 17% while the indicated efficiency is seen to be almost constant (32%). Two dimensional Computational Fluid Dynamic model using FLUENT of experimental test engine is prepared for axi- symmetric flow in the combustion chamber. It is a setup for closed cycle simulation that can predict pressure, mass burn fraction. CFD Simulation is carried out on an experimental engine set up at rated rpm of engine (1.8 HP @3600rpm). The CFD results with the validated Simulink model for this engine configuration shows that at low speeds (1000rpm), the maximum cylinder pressure prediction is about 8% higher for CFD analysis while this deviation is seen to be about 3% at higher speed (3600rpm). The Simulink model is subsequently used to test the predications of brake power and subsequently compared with the experimental results and CFD studies. Both the predictions are found to be in good agreement with the experimental results.