Application of a novel charge preparation approach to testing the autoignition characteristics of JP-8 and camelina hydroprocessed renewable jet fuel in a rapid compression machine

A variety of new, alternative jet fuels are being considered as replacements for conventional petroleumderived jet fuels, and the autoignition chemistry of these fuels are of prime interest. However, traditional batch-based premixture preparation approaches used in chemical kinetics studies are burdened by the low volatility of these fuels. In this work, a new charge preparation approach is described and characterized in which a fuel and air premixture is created directly in the test chamber of a rapid compression machine. The approach relies on a fuel injector to load a small quantity of fuel into the test chamber with high resolution. Preparation of the test charge directly in the device rather than in a mixing vessel reduces the mixture pressure, and hence the fuel partial pressure and mixture temperature requirements to avoid thermal decomposition of the fuel. Gas chromatography/mass spectrometry is used to confirm that an accurately known mass of JP-8 jet fuel is injected into the rapid compression machine, and that all components of the fuel are evaporated and homogeneously mixed within 2 min of the fuel injection, for temperatures from 105 degrees C to 145 degrees C. Ignition delays for JP-8 in air are measured at low temperatures (670-750 K) and low pressures (7 and 10 bar) and the measurements are compared with literature data. The autoignition characteristics of the bio-based camelina hydroprocessed renewable jet fuel are also measured and contrasted with those of JP-8. Under similar compressed conditions, the camelina hydroprocessed renewable jet fuel ignition properties are distinct from JP-8, which provides motivation for pursuing new test strategies to elicit the autoignition chemistry of alternative jet fuels and other nonvolatile fuels. (c) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.