MEASUREMENT OF IONIC MOBILITY IN AVIATION FUEL

摘要

This paper presents work on the measurement of ionic mobilities in aviation fuel. These mobilities determine the speed with which ions move under the influence of a local electric field. The motivation for this work is to contribute to the understanding of the behaviour of electrostatic charge in fuel systems. The measurement method is based on a 'time-of-flight' principle, in which a high electric field is applied to pre-charged fuel. The time taken for the ions in the charged fuel to move across a region of uncharged fuel is recorded. The velocity of the ions is calculated, the applied field is known and from this data the ionic mobility is deduced. A purpose-built test rig was designed and built. Simulation work was performed using COMSOL to optimise the rig design and the choice of experimental conditions. The paper presents the principles behind the method, the design of the rig, and results from the simulation work. Measurement data is presented, and the method for the analysis of this data is outlined. The estimated accuracy was typically approximately ±10%. Mobilities were determined for fuels with conductivities of approximately 3-7pS/m and 23-28pS/m. The mobilities were consistently larger for the higher conductivity fuel, taking account of uncertainties in the measured values. The mobilities were found to be at the upper end of values in the literature for other hydrocarbons.