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 petroleum-derived 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 °C to 145 °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 non-volatile fuels.