NORA: a way to control NOx emissions produced by combustion
Nitrogen oxides (NOx) are pollutants produced during combustion by combination at high temperature of oxygen and nitrogen present in the air. Controlling their formation is an important research field for the transport industry since a significant reduction in NOx at source may potentially make it possible to reduce the complexity and cost of pollution abatement systems.
In the framework of the Groupement Scientifique Moteur (GSM*), a multidisciplinary research team at IFPEN, bringing together experts in combustion chemistry and fluid mechanics, recently developed an effective approach for addressing this industrial challenge. Dubbed NORA (Nitrogen Oxide Relaxation Approach), the approach combines detailed nitrogen oxide formation models with advanced turbulent combustion models with an optimized calculation cost. It describes the formation and reduction of NOx during the combustion cycle and determines the different types and their proportions.
The adopted method is to determine the concentrations of nitrogen oxides in thermodynamic equilibrium, then calculate the characteristic time of relaxation to this balance through a chemical kinetics model developed in partnership with the CNRS. Tabulation of this information based on a limited number of parameters (temperature, pressure, air-fuel ratio) can effectively and quickly predict the NOx concentration in combustion engines and their interaction with the formation of other pollutants such as soot.
Designed to be generic, this method allows a precise prediction of the impact of fuel on the NOx formation and interactions of different pollutants produced by combustion. It is also a tool that can be used to ensure a better match between the fuel and its usage.
* Economic Interest Group bringing together IFPEN, PSA and Renault SA
NOx are really hard to model and to predict using simulation tools, even more when you want to perform fast simulation, close to real time. This kind of model is very useful for understanding the NOx formation process at a research level. Do you think OEM will buy this model and use it for application purpose? Do you think it will be used to save some engine test cell experiments or only for knowledge purpose?