An analytical model to predict nitric oxide concentration in a diesel engine for potential use as feedback for model-based engine control

摘要

Governmental regulation of harmful pollutants requires reduced in-cylinder nitric oxide (NO) formation in internal combustion engines, including diesel engines. Because of the importance of NO emission, it might be desired to have a means to predict its in-cylinder concentration on a real-time basis for various applications, including engine control. Proper estimation of NO concentration during the diesel combustion process, however, is challenging due to the heterogeneous nature of the combustion mixture. For example, use of the ubiquitous single-zone model (typically used to calculate heat release during combustion) renders unrealistic mixture temperatures below those of NO formation kinetics; thus, use of the single-zone model will predict substantially lower NO concentrations than the engine's actual NO concentrations. In many cases, the single-zone model would predict zero concentrations of NO. This study renews a 'two-stage' model that computationally divides the cylinder into four zones; these four zones collectively create more realistic temperatures for the purpose of predicting in-cylinder NO concentration. This article re-introduces the two-stage model and demonstrates its effectiveness at predicting in-cylinder NO concentration.