Prediction of the knocking combustion and NOx formation for fuel gases with different methane numbers

The knocking combustion and the nitric oxide emissions are important boundary conditions with respect to a further efficiency increase in large gas engines. It was, therefore, the aim of the presented work to model the self-ignition of the end gas and the nitric oxide formation for different burn gas mixtures using detailed reaction kinetics. The investigations were based on a one-dimensional gas exchange model with an adapted, predictive combustion model. An empirical model of the cyclic variations was implemented. In contrast to previous approaches, particularly the fast burning cycles were analysed in order to predict the knocking combustion. All models were validated with measurements from a one-cylinder research engine. The comparison with test bench results showed that a good correlation with the measurements could be achieved for the engine performance, the combustion as well as for the nitric oxide formation and the knock tendency. The numerical models will further be used to optimize the combustion process.