Development and Validation of a Multi-Zone Combustion Model for Predicting Performance Characteristics and NOx Emissions in Large Scale Two-Stroke Diesel Engines

Abstract

In the present study, an existing multi-zone combustion model has been modified and applied to predict the performance characteristics and the NOx emissions of a large-scale two-stroke diesel engine (i.e. 12.5 MW rated power). Initially, an attempt was made to examine whether the multizone model can predict with sufficient accuracy the main performance parameters of the stationary diesel engine, using input data from the shop tests (i.e. engine speed, fuel consumption and scavenging pressure at different engine loads). Hence, it was verified that the model is capable of describing the main performance characteristics of the engine with satisfactory accuracy (i.e. reference state). Further on, an experimental investigation was conducted on the specific engine, consisting of a series of performance and NOx emissions measurements that were conducted at constant speed and at three different engine loads. Then, the proposed model was applied at the present engine condition to evaluate its ability to predict the combustion mechanism using the measured cylinder pressure trace as basis for comparison. Furthermore, the predicted engine out NOx emissions were compared to measured values to examine if the model can estimate at least qualitatively the effect of engine load on them. From this combined theoretical and experimental analysis is revealed that the developed model is capable of adequately predicting both engine performance and NOx emissions of large-scale two-stroke diesel engines.