Effect of silane on ignition characteristics of JP10 and kerosene as shown in shock tube study

On the basis of the ignition experiments of JP10 and kerosene, experimentswere carried out to study the effect of silane addition on ignitioncharacteristics of these two typical heavy hydrocarbon fuels behindreflected shock waves over the temperature range of 880\sim1800K and pressurerange of 0.16~0.53MPa.A longer observation time is required as the ignition time increases at thelower temperature region. The shock tube worked under conditions for atailored interface, resulting in an observation time of about 7ms, and thelower temperature bound of experiments was extended in the current study.The uncertainty in the concentration of the fuel vapor due to the adsorptionof the fuel vapor on the shock tube wall is one of the largest sources oferrors in ignition time measurements of heavy hydrocarbon fuels, thus thegaseous concentrations of JP10 and kerosene were determined in the shocktube by measuring the gas pressure with a high-precision vacuum gaugecombined with gas chromatography. Since kerosene is a complex mixture ofmany hydrocarbon components, the adsorption content of differentcomponents differs, so the gas composition different from the liquidcomposition. In the present study, a simulant modified fuel for kerosene wasprepared by adding some heavy hydrocarbon components into the originalkerosene in proportion to the adsorption content to compensate the loss inthe gas phase through the adsorption. To minimize the degree of adsorptionand increase the test fuel vapor pressure, the shock tube was preheated andmaintained at 70 C throughout the experiments. The conditions behindthe reflected shock were calculated from the incident shock speed using theone-dimensional shock relations. A quartz window was installed on thesidewall very close to the endplate of the driven section to monitor theemission from the ignition process in the reflected shock region. Theemission focused through a lens was detected by using a photomultiplierafter passing through a monochromator centered at the emission line of OHradical at 306.5nm as a marker to identify the instant of ignition.When the molar ratio of the added silane with the fuel was in the range of10%\sim15%, the corresponding mass ratio was 2%~3%, a significantreduction in the ignition delay time was observed experimentally. Anincrease of the additionof silane shortened the ignition delay for JP10 at the lower endof temperature range studied. Specifically, the ignition time for JP10decreased from 3.7 to 0.87ms at 1100K and from 0.17 to 0.10ms at1500K. By contrast, the addition of silane shortened the ignition delay for kerosenethroughout the temperature range considered. Specifically, the ignition timefor kerosene decreased from 3.6 to 0.91ms at 1000K and from 0.75to 0.16ms at 1220K. The results presented herein are useful for the engine design andfuel selection in supersonic combustion researches, and also can be used tovalidate chemical kinetics models of heavy hydrocarbon fuel combustion withsilane addition.