Effects of injection timing on nonlinear dynamics of the combustion process in the lean-burn premixed natural gas engine

Abstract.

The nonlinear dynamics of the combustion process in the lean-burn premixed natural gas engine are studied in this paper. Based on nonlinear dynamic theory, the complexity of the combustion process is analyzed under different injection timing conditions. The phase spaces are reconstructed for the experimentally obtained in-cylinder pressure real-time series and the return maps are plotted for the IMEP time series. The results of phase space reconstruction manifest that the attractors are limited to the finite range in the reconstructed phase space. The attractors have a folded and twist geometry structure. The attractors under medium injection timing conditions are looser and more complex. The return maps indicate the coexistence of the stochastic and deterministic components in the patterns combustion process. With the injection timing increasing, there are both a transition from stochastic to deterministic and a transition from deterministic to stochastic, forming the region of deterministic behavior. The largest Lyapunov exponents (LLE) for in-cylinder pressure time series are calculated and the coefficients of variations (COV) of IMEP are also analyzed. The results express that the LLE values are positive. There are a “steep increase” and a “steep decrease” for the LLE and COV values as the injection timing increasing.