Mathematical optimization of variable valve timing for reducing fuel consumption of a SI engine

In this study, the sensitivity analysis and Quasi-Newton algorithms are used to optimize valve timing XU7/L3 engine in order to reduce fuel consumption and increase engine performance. At first, all components of engine are modeled in GT-POWER and a comparison with experimental results is performed to confirm the accuracy of the model. Then, GT-POWER model is coupled with MATLAB-SIMULINK to control inputs and outputs with sensitivity analysis and Quasi-Newton algorithms. The results obtained indicate that optimal valve timing significantly reduces brake specific fuel consumption (BSFC). Moreover, the convergence rate of Quasi-Newton algorithm for reaching the optimal point is higher than the one of sensitivity analysis algorithm.