Spontaneous Ignition Of Droplet Pairs Of N-Decane And N-Tetradecane In Microgravity

The induction times of pairs of droplets of n-decane and n-tetradecane have been investigated experimentally in microgravity. The results were compared to the induction times of single droplets. N-decane is a well matching model fuel for synthetic kerosene while n-tetradecane is well matching the ignition behavior of synthetic diesel fuel. All droplets had a diameter of 0.8 mm. The experiments were carried out at pressures of 0.3 and 0.5 MPa and in the temperature range of 650 to 850 K. The spacing of the droplet pairs was 1, 2, 4 and 6 mm (center distance). The LIF on formaldehyde was applied. Formaldehyde is the stable product of the cool flame reaction and is formed parallel to the OH-radical whose concentration in the cool flame is too low for detection. As formaldehyde is immediately decomposed at hot ignition, the whole ignition process is displayed by applying this technique. The results show that for both fuels the induction times of a pair of 1 mm distance are slightly longer than for a single droplet. Beyond 1 mm the induction times drop below that of a single droplet. The 6 mm spacing showed the shortest induction times. With widening gap between the droplets, the instant of hot ignition moves from near the droplets interspace to in between the droplets and moves back to an arbitrary outside location at 6 mm gap.(c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.