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A plug flow reactor (PFR) is built for investigating the oxidation chemistry of fuels at up to 50 bar and 1000 K. These conditions include those corresponding to the low temperature combustion (i.e. the autoignition) that commonly occurs in internal combustion engines. Turbulent flow that approximates ideal, plug flow conditions is established in a quartz tube reactor. The reacting mixture is highly diluted by excess air to reduce the reaction rates for kinetic investigations. A novel mixer design is used to achieve fast mixing of the preheated air and fuel vapour at the reactor entrance, reducing the issue of reaction initialization in kinetic modelling. A water-cooled probe moves along the reactor extracting gases for further analysis. Measurement of the sampled gas temperature uses an extended form of a three-thermocouple method that corrects for radiative heat losses from the thermocouples to the enclosed PFR environment. Investigation of the PFR’s operation is first conducted using non-reacting flows, and then with isooctane oxidation at 900 K and 10 bar. Mixing of the non-reacting temperature and species fields is shown to be rapid. The measured fuel consumption and CO formation are then closely reproduced by kinetic modelling using an extensively validated iso-octane mechanism from the literature and the corrected gas temperature. Together, these results demonstrate the PFR’s utility for chemical kinetic investigations.

A novel automatic bridge linking capacitance and resistance has been developed. This bridge with only one 10 nF capacitance and one 10 kΩ resistance standard, operating at 1592 Hz, is implemented based on digital compensation techniques. The standards are all defined as four terminal-pair impedances. All voltages applied to the bridge are generated by a multiphase direct-digital-synthesis sine wave source, a special channel of which provided accurate phase and constant amplitude when the phase is changed. In contrast with the conventional quadrature bridge, a lot of inductive dividers and a series of balancing processes are avoided. Preliminary experimental results indicate a relative uncertainty of four parts in 107 is obtained and could be improved further.

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