Richard T.J. Porter

A global sensitivity study of cyclohexane oxidation under low temperature fuel-rich conditions using HDMR methods

This paper presents a global sensitivity analysis of simulations of low-temperature isothermal cyclohexane oxidation under fuel-rich conditions using the method of high-dimensional model representation (HDMR). The analysis is used to investigate the important features of the oxidation process, as well as possible factors underlying qualitative discrepancies between simulations and experiments. The particular feature of interest is the characteristic of quadratic autocatalysis, which is observed experimentally and leads to the maximum rate of reaction occurring at 50% consumption of the deficient reactant (oxygen), with the fuel consumption exerting only a weak dependence. The kinetic mechanisms tested do not exhibit this characteristic when simulating the experimental conditions. The models also exhibit shorter induction times than those observed in the experiment. The HDMR study demonstrates a sensitivity of these features to the A-factors of key reactions of the cyclohexylperoxy radical (C6H11OO). At the low temperatures studied here, these are peroxy–peroxy radical reactions rather than the isomerisation routes that have been the subject of other investigations at higher temperatures. The low temperature product channels for reactions of the cyclohexylperoxy radical are therefore an important area for future kinetic studies. The effects of wall reactions of peroxy and peroxide species were not found to outweigh the impact of the main A-factors, but including wall losses led to significant higher order interactions between input parameters. This constitutes an interesting and important area for further research.

Mercury Transformation Modelling with Bromine Addition in Coal Derived Flue Gases

In this work we present a gas-phase mechanism describing the oxidation of mercury by bromine and chlorine for application to coal derived flue gases. Developed sub-models for Hg-Cl and Hg-Br oxidation are combined with NOX, sulphur, chlorine and bromine chemistry in order to form an overall homogeneous mechanism that is applicable to post-combustion flue gases. The mechanism is compared to experimental data obtained from flow reactor studies and then investigated using rate-of-production and sensitivity analyses in order to identify the most important and influential reaction channels.

Automatic generation of reduced reaction mechanisms for hydrocarbon oxidation with application to autoignition boundary prediction for explosion hazards mitigation

Abstract In this work we present an automatic method for removing species and reactions from comprehensive reaction mechanisms without significant detriment to model performance. Numerical methods are applied to a lean n-butane—air closed vessel system. A method for the automatic construction of closed vessel ambient temperature—composition ( T a −) ignition diagrams is presented, which is used to evaluate the comprehensive and reduced models. Application of the quasi-steady state approximation to the reduced mechanism has been proven to significantly reduce the number of species with very little loss of output accuracy.