Simulative Investigation of the Service Methane Number of LNG Mixtures Using 1D-Engine Simulation and Reaction Kinetics

Following the ongoing software development, the continuously increasing accuracy of 0D/1D-simulation of combustion engines and chemical mechanisms for the use in reaction kinetic calculation open up a new possibility to calculate combustion processes. Particularly combustion processes with high dependency on reaction kinetics, such as knocking events, can be predicted. The simulation of knock events further allows a characterization of the knock behavior of LNG mixtures. This paper focuses on 1D-simulative investigation of knocking events to determine the Service Methane Number of different LNG mixtures and their dependency on single gas components. This is realized with two different approaches, which are presented in this work. In the first approach, measurement data and a Three-Pressure-Analysis-model are used to describe the in-cylinder condition at inlet valve closes. The results are used as starting condition in a reaction kinetic model which simulates the geometric and thermal compression during the engine combustion cycle. The second approach consists of a predictive 1D-engine simulation model with an integrated knock model on the basis of reaction kinetics and a statistical model to describe Cycle-to-Cycle variations. Using these two approaches, the knock behavior of reference gases, consisting of methane and hydrogen, and different LNG-mixtures is simulated under comparable engine operating and knock conditions. By comparison of reference gases and LNG mixtures, the Service Methane Number and its dependency on single gas components is determined.