Comparative study of the simulation ability of various recent hydrogen combustion mechanisms in HCCI engines using stochastic reactor model

Abstract

Hydrogen is a clean potential alternative fuel for internal combustion engines and completely eliminates the carbon based engine emissions (CO, CO2 and unburned hydrocarbons). Homogenous charge compression ignition (HCCI) is a low temperature combustion mode with higher thermal efficiency and ultralow NOx emission. Hydrogen HCCI engine can combine potential benefit of fuel and combustion characteristics. In HCCI engine, combustion is governed by the chemical kinetics of the oxidation reactions. In-order to find a suitable reaction mechanism to numerically predict the combustion characteristics of hydrogen HCCI engine, 15 recent hydrogen combustion mechanisms are compared and analyzed. All mechanisms were simulated using a stochastic reactor model (SRM) to evaluate the combustion parameters for HCCI engine. Simulations were performed by varying inlet temperature (400e440 K), intake pressure (1.0e3.0 bar), engine speed (1000 e3000 rpm) and relative air-fuel ratio (l ¼ 2 to 8) for all the mechanisms. Ignition delay predicted from different mechanism was compared with experimental data and ignition delay was also compared at engine like condition using all the test mechanisms. Error in prediction of different combustion parameters such as start of combustion (CA10), maximum cylinder pressure (Pmax) and maximum heat release rate (HRRmax) were evaluated using different hydrogen combustion mechanisms. It was found that a recently developed hydrogen mechanism (Maurya-2017) shows the closet resemblance with the experimental cylinder pressure data. The Oconaire-2004 mechanism was able to accurately predict the characteristics of hydrogen HCCI combustion. It was also found that NUIG-NGM-2010 and CRECK-2014 mechanisms were able to estimate the HCCI combustion characteristics under higher combustion temperature