Generation and analysis for a skeletal chemical kinetic model of IC8H18 with Nitric oxide in HCCI combustion

Abstract

A new mechanism for IC8H18 with nitric oxide (IC8H18-NO) in homogeneous charge compression ignition (HCCI) combustion is presented to investigate the effects of NO in exhaust gas recirculation (EGR) on combustion. The IC8H18 sub-mechanism consists of 112 species and 467 reactions. A NO sub-mechanism is developed through reaction path analysis. The reaction paths of NO are summarized on the basis of the detailed NO mechanism reported by Anderlohr to describe the effects of NO on IC8H18. A new IC8H18-NO mechanism with 167 species and 835 reactions is described. The IC8H18 sub-mechanism of IC8H18-NO mechanism was validated by the ignition delay times in a shock tube. Experimental and computational results are in good agreement with those of ignition delay times at 855 to 1269 K and at 2 and 6 MPa with equivalence ratios of 0.5 and 1.0. The new IC8H18-NO mechanism is also validated in an HCCI engine. Computational results are consistent with experimental data of ignition delay times at a NO concentration range of 0 to 500 × 10-6 (volume fraction). The effects of NO on IC8H18 differ as the NO concentration increases. Therefore, the effects of NO on IC8H18 are simulated using a zero-dimensional model using the CHEMKIN PRO software. Key reactions at different NO concentrations are proposed by analyzing the sensitivity and productivity rates. The resource of OH for initial IC8H18 consumption is mainly generated through R476, which occurs as a result of the promoting effect of NO reon IC8H18 consumption. The ability of NO to combine with active radicals, such as those in R476, is enhanced as the NO concentration is increased.