Browsing by Author "Lawes, Malcolm"

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    Interpretation of Auto-ignition Delay Times Measured in Different Rapid Compression Machines
    (White Rose University Consortium, 2015) Bradley, Derek; Lawes, Malcolm; Materego, Myeji C.
    An international collaboration was initiated by thirteen different research groups to understand and explain the differences in auto-ignition delay times, measured on different rapid compression machines, RCMs, of different design and size [1,3]. The Consortium measured delay times, k, for ioctane under the same conditions: fixed oxygen content of 21%, pressure at the end of compression, Po, 2.0 MPa, and compression temperatures, To, in the range 650-950K. Figure 1 gives the experimental auto-ignition delay times, ke , from seven different RCMs plotted against 1000/To. Each point is identified by a number unique to each participating group. There is significant scatter in ke , particularly at the intermediate and low temperatures
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    Low Temperature Ignition Properties of N-Butanol: Key Uncertainties and Constraints
    (Laboratory of Heterogeneous Mixtures and Combustion Systems, 2015) Agbro, E.; Materego, Myeji C.; Lawes, Malcolm; Tomlin, A. S.
    A recent kinetic mechanism (Sarathy et al., 2012) describing the low temperature oxidation of n-butanol was investigated using both local and global sensitivity/uncertainty analysis methods with ignition delays as predictive targets over temperature ranges of 678-898 K and equivalence ratios ranging from 0.5-2.0 at 15 bar. The study incorporates the effects of uncertainties in forward rate constants on the predicted outputs, providing information on the robustness of the mechanism over a range of operating conditions. A global sampling technique was employed for the determination of predictive error bars, and a high dimensional model representation (HDMR) method was further utilised for the calculation of global sensitivity indices following the application of a linear screening method. Predicted ignition delay distributions spanning up to an order of magnitude indicate the need for better quantification of the most dominant reaction rate parameters. The calculated first-order sensitivities from the HDMR study show the main fuel hydrogen abstraction pathways via OH as the major contributors to the predicted uncertainties. Sensitivities indicate that no individual rate constant dominates uncertainties under any of the conditions studied, but that strong constraints on the branching ratio for H abstraction by OH at the α and γ sites are provided by the measurements.